REPORT DOCUMENTATION FORMWATER RESOURCES RESEARCH CENTER

University of Hawai i at Manoa2 FCST Category1Report

Number Technical Report No. 122~ Report Date

February 1979Ecological Observations off theMOkapu~ O'ahu~ Ocean Outfall:A Post-Installation Study

6Author (s)

Anthony R. RussoSteven J. DollarE. Alison Kay

SNo. of Pagesix + 49

b No . of 17NO. ofTables 13 Figures 17

9 Grant or Contract Agency

Department of Public WorksCity and County of Honolulu

lOGrant or Contract No.F-637-78

11 d D •Keywor s escPbpto~s: *Benthic fauna, *coral, *marine animals, aquaticlife, marine plants, Hawaii.

Identifie~s: *Micromollusks. biomonitorin~, marine outfall, Mokapu outfall.12Abstract (Purpose, method, results, conclusions)

An ecological study of the benthic and fish communities at Mokapu,O'ahu, was completed in the summer of 1978 approximately 1 yr subsequent tothe installation of a submarine outfall by the City and County of Honolulu.Data were obtained from five transects between Mokapu Point on the north­eastern tip of O'ahu to Alala Point, approximately 6 034 m (3.75 miles)south, at depths of 6 to 24 m (20-80 ft). This study is subsequent to aninitial survey completed in 1975 prior to outfall construction.

Results show little or no effect from the operation of the outfall onthe benthic and fish communities. There are not significant differences inthe abundance, diversity, or composition of fishes from 1975 to 1978 exceptat the outfall site where new substrate was formed by construction. Betweenthe 1975 and 1978 studies there are some differences in coral species coverindices, which are attributed to patchy substrate distribution rather thanstress from the sewer outfall. Differences in species composition and dis­tribution of micromolluscan assemblages may also be explained, at least inpart, by patchy distribution of the substrate.

2540 Dole Street, Holmes Hall 283 • Honolulu, Hawai i • U.S.A.

ECOLOGICAL OBSERVATIONS OFF THE MCKAPU, O'AHU, OCEAN OUTFALLA POST-INSTALLATION STUDY

by

Anthony R. RussoSteven S. Dollar

E. Alison Kay

Technical Report No. 122

February 1979

Interim Progress Reportfor

MOKAPU BENTHIC ECOSYSTEM AND FISH POPULATION STUDY

Principal Investigators: Anthony R. Russo and L. Stephen Lau

Project Period: 1 June 1978 to 31 May 1979

The research reported herein was funded by the Department of Public Works,City and County of Honolulu, and the Water Resources Research Center,University of Hawaii.

v

ABSTRACT

An ecological study of the benthic and fish communities at MBkapu,

o 'ahu, was completed in the summer of 1978 approximately 1 yr subsequent to

the installation of a submarine outfall by the City and County of Honolulu.

Data were obtained from five transects between MBkapu Point on the north­

eastern tip of O'ahu to Alala Point, approximately 6 034 m (3.75 miles)

south, at depths of 6 to 24 m (20-80 ft). This study is subsequent to an

initial survey completed in 1975 prior to outfall construction.

Results show little or no effect from the operation of the outfall on

the benthic and fish corrmunities. There are not significant differences in

the abundance, diversity, or composition of fishes from 1975 to 1978 except

at the outfall site where new substrate was formed by construction. Between

the 1975 and 1978 studies there are some differences in coral species cover

indices, which are attributed to patchy substrate distribution rather than

stress from the sewer outfall. Differences in species composition and dis­

tribution of micromoUuscan assemblages may also be explained, at least in

part, by patchy distribution of the substrate.

CONTENTS

ABSTRACT....

INTRODUCTION.Description of Study Sites

FISH AND ALGAE .Methods and Materials.Results. . . ...Discussion.

CORALS. . . .Methods.Results.Discussion

MICROMOLLUSKSMethods.Results.Discussion

CONCLUS ION.

REFERENCES.

APPENDICES.

ILLUSTRATIONSFIGURES

1. Map of Sampling Stations, 1975 and 1978, M6kapu Outfall,Kailua Bay, O'ahu. . . . . . . . . . .. . ....

2. Comparative Standing Stocks of Fish at All Stations,1975 and 1978, M6kapu Outfall, O'ahu .

3. Variation of Total Coral Cover and Species Cover Diversitywith Depth, 1975 and 1978, Mokapu Outfall, O'ahu ....

4. Percent Cover of Four Dominant Coral Species. Station A.Mokapu Outfall. O'ahu, 1975 and 1978 .

5. Percent Cover of Four Dominant Coral Species. Station B,Mokapu Outfall, O'ahu, 1975 and 1978 .

6. Percent Cover of Four Dominant Coral Species, Station C,M6kapu Outfall, O'ahu, 1975 and 1978 .

vii

v

1

3

3

3

4

6

11

11

11

19

27

27

28

35

36

37

39

2

9

13

14

14

15

viii

7. Percent Cover of Four Dominant Coral Species, Station 0,M6kapu Outfall, O'ahu, 1975 and 1978 16

8. Percent Cover of Four Dominant Coral Species, Station E,M6kapu Outfall, O'ahu, 1975 and 1978 . . . . . . . . . . 17

9. Total Coral Species Richness (Number of Species) forEach Transect, 1975 and 1978, Mokapu Outfall, O'ahu. . . . 18

10. Abundance and Species Diversity of Micromo11usks on TransectsB through E, 1975 and 1978, Mokapu Outfall, O'ahu. . . . . . .. 30

11. Summary of Micromo11uscan Species Distribution and Abundanceat Depths of 60 to 100 Feet, 1975 and 1978, Mokapu Outfall, O'ahu. 31

12. Micromo11uscan Species Composition at Depths of 20 to 100 Feet,MOkapu Outfa11, 0' ahu, 1975 and 1978 . . . . . . . . . . . • . 32

13. Summary of Micromo11uscan Species Composition and Abundance atDepths of 20 to 40 Feet, Mokapu Outfall, O'ahu, 1975 and 1978. 33

PLATES

1. Newly Formed Boulder Substrate Surrounding Mokapu PointSewage Outfall Pipe, O'ahu, 1978 . . . . . . . . . . . . . . . .. 7

2. Diffuser Vent in Mokapu Outfall Pipe, O'ahu, 1978. 223. Exposed Mokapu Outfall Diffuser Pipe, O'ahu, 1978. . . . . 224. Bryozoan, Triphyllozoon hirsutum Busk, Growing on

Outfall Boulders, Mokapu Outfall, O'ahu, 1978. . . . . . . . 24

TABLES

1. Comparative Statistics for Fish Populations from 1975 to1978, Mokapu Outfall, O'ahu. . . . . . . . . . . . . . . . . . 4

2. Algal Biomass, Mokapu Outfall, O'ahu, 1975 and 1978. . . . . . 63. Percent of Benthic Cover by Coral Species for Each

Transect, 1978 and 1975, Mokapu Outfall, O'ahu • . . . 124. Abundance, Species Diversity, and Species Composition of

Micromo11usks at Transect Stations, Mokapu Outfall, O'ahu, 1978. . 295. Mean Percent Composition and Ranks of Six Dominant Species

of Micromo11usks at Depths of 20-40 Feet, 1975 and 1978,Mokapu Outfall, O'ahu. . . . . . . . . • . . . . . . . . . . 34

6. Mean Percent Composition and Ranks of Five Dominant Speciesof Micromo11usks at Depths of 60-100 Feet, 1975 and 1978,Mokapu Outfall, O'ahu.......•............... 34

INTRODUCTION

During the month of December 1975 a study of the benthic marine commu­

nity was made at Mokapu, O'ahu (Russo et al. 1977). This study was made

prior to the completion of an outfall with a discharge of secondary sewage

effluent; the outfall, constructed for the City and County of Honolulu,

began operation in December of 1977. During February 1978 the Kane'ohe Bay

outfall was diverted to Mokapu, and in May 1978 the Kailua Bay outfall was

connected to the Mokapu line. The total volume rate of sewage discharge is

approximately 0.4 m3/s (9 mgd). The total outfall length is 1 524 m

(5 000 ft) including the diffuser which has a length of 293 m (960 ft) and

lies in 25.9 to 30.5 m (85-100 ft) of water. The outfall pipe was

laid on the bottom, and its entire length was covered with large boulders.

In compliance with the request of the City and County of Honolulu, this

study is a follOW-Up to the initial survey made in 1975. The main purpose

of this study is to report on changes, if any, in the benthic community

made by the construction and discharge of the outfall. The following have

been monitored and changes reported:

1. Fish population abundance and diversity

2. Biomass of attached algae

3. Diversity and cover of hermatypic corals

4. Distribution, abundance, and diversity of micromollusks.

Ecological surveys of the marine environment prior to installation of

sewer outfalls are now a part of most local water quality studies (Turner

et al. 1964). Follow-up surveys are important in order to assess any major

changes to the coastal marine environment caused by the construction of

outfalls (Turner et al. 1965). These surveys also provide outfall engineers

with feedback on the design of outfall systems and their feasibility for use

under different environmental conditions.

A study of the Kailua Bay area was conducted in 1973 (Kay et al. 1973)

to examine the benthic biota in a baseline study from M6kapu Point to

Mokulua Island off Lanikai. The 1975 study (Russo et al. 1977) gathered

data on the benthic biota at five stations from Mokapu Point to Alala Point

north of Lanikai (Fig. 1). These same stations were reexamined in June

1978; comparative findings are presented in this report.

2

oIo

KILONETER

IOQ

8 - SAMPLING STATION

SUBSTRATE DESCRIPTION

1 - SAND, SILT

2 - SOLID BASALT PAVEMENT

3 - SOLID LIMESTONE VENEER

4 - BASALTIC BOULDERS

WATER DEPTHCONTOUR

(METERS)

I~

FIGURE 1. SAMPLING STATtONS. 1975 AND 1978, MOKAPU OUTFALL, KAILUA BAY,O'AHU

3

Description of Study Sites

Station B coincides with the Mokapu outfall; three stations, C, 0, E,

are located 1 609, 4 023, and 5 632 m (1, 2.5, and 3.5 miles) south of the

outfall; and station A is located 1 609 m (1 mile) north of the outfall off

Mokapu Point (Fig. 1). Station C is located north of Kailua Bay, station 0

in Kailua Bay, and station E off Alala Point. At each station, depths of

6, 12, and 18 m (20, 40, and 60 ft) were studied as in the 1975 study. In

1975 the 30-m (IOO-ft) depth was examined, and results showed that all

stations except A had a sand substrate at the 30-m depth. In this study

the 24-m (80-ft) depth, which seemed to be the limit to hard, coral-bearing

substrate, was surveyed at stations A, B, and o. The results from this

depth will be used as an additional area for comparison in the follow-up

study proposed for the summer of 1979.

FISH AND ALGAEMethods and Materials

Fish surveys were made at stations A through E at depths of 6, 12, and

18 m. A 30-m (lOO-ft) line marked off at every meter was laid on the bot­

tom. A diver swimming along the line counted and identified species of

fish 3 m (10 ft) on either side of the transect line so that a 186 m7

(2000 ft 2) area was swept. At station B, a fish count was made at each

depth on the outfall and 10 m (33 ft) to either side of the outfall. Fish

diversity was calculated at each depth using the Shannon-Wiener information

index, H' (Russo et al. 1977). To compare fish communities before and

after outfall operation, Sorenson's Similarity Index was used (Mueller­

Oombois et al. 1974). The index in effect measures the redundancy of fish

species from one spatial community to another or, as in this case, from one

point in time to another. The equation for the index is SI = 2CjA + B where

C = number of species common to both transects

A = number of species in 1975 transects

B = number of species in present (1978) transects,

Mueller-Oombois and Ellenberg (1974) suggest that an index of 50% (.50)

represents a threshold value; that is, if the index value exceeds 50%, the

similarity is great enough to indicate that the species are a part of the

same association or community. In general, common species may be emphasized

4

in defining communities since they are most involved in the bioenergetics

of the community.

Algal biomass at each station was determined by cropping all the algae

in a 1/4-m2 quadrat placed randomly at five points along the transect line

at each depth. Each quadrat sample of algae was sorted into genera, weighed

wet on a Mettler balance, dried at 38°C (100°F) for 24 hours, and then

weighed again. Presence or absence of major invertebrates other than corals

was noted on each transect.

Results

Calculation of Sorenson's Similiarity Index for all stations and depths

shows very little change in characteristic fish communities between Decem­

ber 1975 and June 1978 except at station B, the outfall site (Table 1).

TABLE 1. COMPARATIVE STATISTICS FOR FISH POPULATIONSFROM 1975 TO 1978, MOKAPU OUTFALL, O'AHU

Station Similarity Index % Change % Change in % Change inFish Species in HI Total Fi sht No. Species

A20 .61 -12 -8 -20

40 .60 -19 -3 -17

60 .67 -1.7 -22 +4

B20;~ .25 +123 +82 +77

40 no fish counted +100 +100on first transect

60 +100 +100

C20 .80 +30 +5 +100

40 .55 +25 +11 +16

60 .55 +11 -28 +8

020 .55 +0.5 -14 +20

40 .61 -12.5 -28 -5

60 .51 +1.1 +25 +20

E20 .45 -6.5 -7 -16

40 .57 -5.0 -16 -10

60 .58 -10.8 -20 -17

*Transect excluding outfall fish aggregations.tLarge schools excluded.

5

There was little similiarity between the 1975 and 1978 transects at station

B. Results also show little change in total fish, diversity index, and

species richness at each station and depth except for station B. At sta­

tion B20 there was an 82% increase in total fish counted, a 77% increase in

numbers of species, and a 123% increase in diversity.

Fish of the families Acanthuridae and Chaetodontidae were abundant,

along with the family Pomacentridae, as they were in the 1975 survey.

Thalassomaduperreyi (Labridae) was abundant at most stations as it was in

1975. A list of species, diversity indices, and equitability components

(H'/H'max) for all stations and depths is shown in Appendix A.

At station B results showed a large increase in all major fish fami­

lies, especially over the large rocks covering the outfall. Transects laid

at a distance 10 m from the outfall line showed less fish than directly

over the outfall but still showed more total fish and greater species rich­

ness than in the 1975 survey. At station B depths where no fish were seen

in December 1975, fish now abound. Large aggregations (>30) of Kyphosus

cinerasoens (nenue), Chaetodon miliaris (lemon butterfly), Mulloidichthys

aurif7amma (weke), Parupeneus porphyre~s (kumu) and Abudefduf abominalis

(mamo) were seen at depths of 24 to 30 m (80-100 ft) along the diffuser.

Results of the algae collection showed that most of the biomass of

algae recorded was found at stations B, C, and D. In the 1975 study most of

the algal biomass occurred at these same stations (Russo et ale 1977; Table

1). There was no large change in biomass of algae from 1975 to 1978.

Halimeda remained the most abundant algae seen. Dictyopteris, Amansia,

Asparagopsis, and Desmia were also abundant. At station B40 beds of

Dictyopteris australis were found covering large areas of the bottom. Al­

though many other algal species were seen, none was abundant enough to mea­

sure and record for biomass. Results are shown in Table 2.

As in the 1975 survey, the most frequently encountered macroinverte­

brates, other than corals, were sea urchins of the genera Echinothrix,

Echinometra, and Tripneustes. At station C the burrowing sea urchin Echi­

nostrephus aoiculatus was observed. This species was not reported in the

1975 survey. The distribution of sea urchins was spotty, and their abun­

dance very low.

6

TABLE 2. ALGAL BIOMASS, MOKAPU OUTFALL, O'AHU, 1975 AND 1978

1975 1978

Station Depth Wet Wt. Dry Wt. Wet Wt. Dry Wt. Genus

(m) ------------------ (9) ------------------

A20 6 None None None None None

40 12 None None None None None

60 18 None None None None None

B20 6 None None None None None

40 12 None None None None None

60 18 None None None None None

C20 6 None None None None None

40 12 None None None None None

60 18 125 44 91 28 Dictyopteris

162 75 100 45 Halimeda

020 6 None None None None None

40 12 79 15 65 15 Halimeda

60 18 None None None None None

E20 6 229 89 None None Dictyopteris

40 12 None None None None None

60 18 None None None None None

Discussion

The fish communities at each of the stations and depths remained

essentially the same from 1975 to 1978 except for station B, the outfall

site. Similarity indices show that the communities did not change their

composition by species (Table 1). Communities would only be expected to

change their species composition under extreme stress, e.g., depletion of

food supply, destruction of substrate habitat, change of physico-chemical

environment. Changes of this type were not observed in this study. All

values of Sorenson's index, except for station B, were above 50%. Expe­

rience has shown that there is rarely a similarity index based on species

presence which exceeds 60 to 70% (Mueller-Dombois 1974). Even the species

lists of two similar, neighboring communities rarely have more than 2/3 of

their species in common. At station B the similarity index indicates a

significant change in fish abundance and diversity, probably due to the new

substrate afforded by construction of the outfall. The new substrate pro­

vided by the large rocks covering the outfall attracted large numbers of

fish, providing not only substrate for the growth of attached algae but

also habitat space (Plate 1). The rudderfish (Kyphosus cinerascens) was

abundant over the outfall substrate. This fish, a strict herbivore, was

seen grazing on attached algae. Acanthurids, which are also herbivorous in

general, were abundant along the outfall. Large numbers of weke (MUlloi­

dichthys aurif1amma) were observed feeding on the sediment alongside the

outfall. Weke normally feed on benthic infauna and may have been feeding

on organic detritus in the sediment. Whatever their food source, the out­

fall site attracted them in large numbers. These observations are consis­

tent with many studies done on the increased nucleus of marine organisms,

especially fish, associated with the construction of artificial reefs.

PLATE 1. NEWLY FORMED BOULDER SUBSTRATE SURROUNDING MOKAPUPOINT SEWAGE OUTFALL PIPE, O'AHU, 1978. BOULDERSSIGNIFICANTLY INCREASED THE HABITAT COMPLEXITYLEADING TO MORE NUMEROUS SETTLING SITES FOR BEN­THIC INVERTEBRATES AND TO INCREASED SHELTER ANDGRAZING SURFACES FOR MOTILE INVERTEBRATES ANDFISHES.

7

8

The new substrate also attracted large numbers of water column forag­

ers. Many fish are adapted to foraging for plankton and organic particles

in a water column above a reef substrate (Davis et al. 1973). There are

several species of coral reef fish which forage in a water column. For

example, Strasberg (1966) cited the pomacentrid Abudefduf saxatiZis as being

a "particulate plankton picker." Large aggregations of the pomacentrid

Abudefduf abominaZis were seen in the water column above the outfall at all

depths. This species was described by Hobson (1974) as being mainly a

diurnal planktonivore which preys primarily on copepods in the water column.

Large aggregations of the butterfly fish Chaetodon miZiaris were observed

over the outfall at most depths. C. miZiaris is also a p1anktonivorous

water column feeder (Hobson 1974).

A fish count was made on the diffuser in 27 m (90 ft) of water. Large

aggregations of Lutjanus kasmipa (taape), Acanthupus oZivaceus, and MUZZoi­

dichthys fZavoZineatus (weke) were seen (Appendix A). The bryozoan Tri­

phytZozoon hipsutum, sometimes called lace coral, was very abundant along

the diffuser (4-8 colonies/m2 ). The abundance of bryozoans may be due to

the increase in particulates and microorganisms in the water because this

organism is a strict filter feeder.

In the December 1975 study, fish standing stock abundance was reported

to be high at stations A, D, and E and lower at stations C and B. The same

trend has held in this study (Fig. 2). When large, passing schools of fish

are excluded from the total counts, the percent change from 1975 to 1978

ranged from 3 to 28% at all stations except for station B which showed an

82% increase in fish seen. These counts were made off the outfall. A much

larger increase of fish was realized if those directly over the outfall

were included. Along with this increase in total fish, a significant in­

crease in diversity index and numbers of fish over data reported in 1975

was seen at station B (Table 1). At all other depths except C20 the per­

cent change in species richness was small. The anomalous result at C20 is

explained by the fact that an increase from 2 to 4 species was seen, that

is, there was a small absolute increase but a large percentage increase.

Grigg (1972) reported changes in both species and abundance of near­

shore fishes off sugar mill outfalls on Hawai'i. He reported the increase

of some species which could utilize the waste as food and a decrease in

others which were affected by the pollution load. Turner et al. (1965)

-(IJ,

Eoco'-o 400c-

_ 1978 June

F:::::::::::~ 1975 December

9

~

:r:CJ)

l.L.l.L.oen~

uo.....en<!)

zoz~en A B C

STATIONo E

*Excluding large schools and those fish counted over theoutfall.

FIGURE 2. COMPARATIVE STANDING STOCKS OF FISH AT ALLSTATIONS, 1975 AND 1978, MOKAPU OUTFALL, O'AHU

reported large aggregations of two species of fish feeding off effluent in

the vicinity of the Orange County, California Sanitation District Ocean

Outfall. They measured kelp bass and sand bass close to the maximum size

(0.4 m or 17 in.) for these species. However, Turner et al. did not record

whether or not there was a change in the diversity at the outfall. The

central idea is that a community has structure which is somehow defined, at

least in part, by its diversity. In polluted environments there normally

is less diversity. Pollution intolerant species give way to more tolerant

forms (Stein and Denison 1963). The tolerant forms tend to become more

abundant because there is less competition for existing resources. Patrick

and Strawbridge (1963), describing the changes in a phytoplankton community

structure, carefully point out that the use of single indicator species may

not be a valid measure of pollution load. In reporting large aggregations

of organisms, especially fish, the investigator may not correctly interpret

an increase in abundance and biomass as a positive result since pollution

intolerant species may have been replaced by tolerant ones. There is also

the remote possibility that a large change in the community might occur

with no change in diversity. This may occur where niches occupied prior to

an environmental change are replaced with new species tolerant to the new

10

environmental milieu. In the case of the Mokapu outfall station, there was

a definite increase in abundance of a few species of fish; but, more impor­

tant, there was also a concomitant increase in both diversity components-­

the species richness and equitability. There was also an increase in fami­

lies represented. This is an indication of little or no pollution stress

on the fish community; in fact, as mentioned above, the outfall construction

probably enhanced all aspects of the fish community by increasing habitat

(shelter) space and settling sites for algae and other sessile organisms

upon which fish feed.

The biomass of algae did not change significantly. The same dominant

species were seen in this study as were observed in 1975. During dives at

26 to 27 m (85 to 90 ft) over the diffuser, the effluent discharge was no­

ticeable directly over the diffuser but disappeared 15 to 20 m from the out­

fall. The outfall plume discolored the water slightly as it rose and formed

a 2 to 3-m turbidity layer over the outfall. The mixing is vigorous in

these waters, and it is speculated that little nutrient enrichment takes

place except at the diffuser. This may explain why there was no apparent

increase in algal biomass at the stations. Extensive Dictyopteris beds were

observed, but these beds were also observed by Kay et al. (1973) and by

Russo et al. (1977) before the outfall became operational. At station E20

no algae were recorded in this study although Dictyopteris was recorded in

1975. This is probably due to our inaccuracy in finding the area, the

spotty distribution of algal beds, and the turbidity at this station.

CORALSMethods

The coral community and associated macroinvertebrates were surveyed

using a continuous photographic transect technique, a method which appears

to be more efficient with respect to time spent under water and area sur­

veyed than either a chain transect or conventional quadrat method. In this

study, each transect was 30 m long at depths of 6, 12, and 18 m at each of

the five stations.

The photographic transect technique involved mounting a Nikonos II

camera on a supporting frame 1.25 m above a 1 x 0.7-m quadrat. The support­

ing frame and quadrat were constructed of O.Ol-m (1/2-in.) aluminum tubing,

11

and the camera was mounted on a Plexiglas plate attached to the four sup­

porting arms of the frame. At each transect location, a 30-m polypropylene

line was laid across the bottom at a random orientation. The camera quadrat

frame was placed on the bottom so that the l-m side of the quadrat was

parallel to the first meter of transect line. A color slide was then taken

of the 1 x O.7-m area within the quadrat. This process was repeated at 12

random marks along the 30-m transect line. Transect locations and depths

were written in large letters on an underwater slate and photographed with

the remaining film for later identification. Because small colonies may

not show up in the transect photographs, a diver with a species checklist

on a clipboard recorded the presence of all coral species in each frame of

each transect.

The developed slides were projected onto a grid with the same dimen­

sions as the quadrat, and the abundance of corals and noncoral substrate

was estimated by counting the number of square centimeters occupied by each

coral colony. From these counts, estimates of percent cover and colony

size were determined.

Results

Tabulation of the coral coverage at each transect in terms of percent

coral and noncoral bottom cover is listed in Table 3 for each species and

substrate type for both the 1975 and 1978 surveys. Also in Table 3 are the

differences in total coral coverage between the two surveys. The total

coral cover and the species cover diversity (Shannon-Wiener index H' =s

~L Pi/In/Pi, where Pi = the proportion of the ith species) at each transect'l-=l

for both the 1975 and 1978 surveys are shown in Figure 3. For the thirteen

species encountered. five can be considered dominant species as they

occurred on most of the coral-containing transects. These five corals-­

Poai Uopora meand:l'ina, Porites lobata, P. corrtpressa. Montipora verI'Ucosa,

and M. patula -- are the dominant corals on most Hawaiian reefs and have been

shown to comprise very high proportions of the coral cover off the Kona

Coast of Hawai'i (98%) (Dollar 1975a. b) and in Kane'ohe Bay, O'ahu (95%)

(Maragos 1972). Figures 4 to 8 show plots of abundance of these corals

at each transect for the 1975 and 1978 surveys. The various species of

12

TABLE 3. PERCENT OF BENTHIC COVER BY CORAL SPECIES FOR EACHTRANSECT, 1978 AND 1975, MOKAPU OUTFALL, O'AHU

Spec I..A20 A~O A60 A80 820 840 860 C20

Stat IonC40 C60 020 040 060 080 £20 [40 £60

).95 0.69 0.09

4.59 )4.)0 )0.)0

000

0.22 0.36 0.51

2.28

0.52

0.82

5.02

1.62 16.87 10.76

12.62 '.)4 4.'2

o 7.11 0.)0

0.0' 5.15 14.78

7.)6

1.)

6.)7

27.7

0.39

1.46

0.86

15.5

1.% 24.28 12."

16.16 5.20

2.50 2.40

0.87 11.7)

4.20

1.91

2.'7 26.37 10.53 12.00

4.1) 8.19 '.7) 1.57

0.14 O.~ 0 0

0.30 5.28 '5.2 0

O.,~ .1.90

8.6) 3.21

0.14

9.50

0.83

17. )4

2.76•• t

4.60

).54

7.H

10.60

19.70

1.15

0.20

7.05 7.70

8.SO 16.7)

ot 0.09

0.02 0.05

1978 7.62 10.78

1975 2).00 1).8)

1,,8 O.~ 0

'''5 0 0.02

0.0)

3.14

o62.42

o 0

o 0

o 0

o 0

o 0

0.08 0.09

).)9 0

3.13 0

o 0

o 0

O.I~ 0.03

0.16 0

0.85

0."7.)0

".00.22

o0.03

o 0

o

o 0

4.40 0

o 0

o 0

o.h 7.74

o 0

o 0

o

15.9) 0

o

o 0

o 0

o 0

o 0

3.62 15.60 '.1'

o 3.82

8.44 40.11 11.4)

49.86 53.12

o 0

o 0

18." 0

o 0

o 0

o 0

0.23 0

o 0

14.57

3.19

0.80 8.52

3.68 0

000

000

0.47 0 0

0.02 0.01 0

000

0.28 0 0

000

000

000

000

0.06 0 0.51

0.09 0 5.0

1.55 0

0.63 60.45 67.71

0.06

2.62

o 0 0 0

o 0.05 0 0

o 0 0 0

o 0 0 0

000 0

o 0 0.11 0

o 0 0 0

o 0.46 0 0

o 0 0 0

o 0 0 0

0.58 0 0 0

4.70 0 0.4) 0.3)

0.15- 0.14 0.05 0 0 0.35 0.41

0.16 0 0.'9 0.68 0.47 6.45

o0.)1

o 0

o

o 0

o

o 0

o

o 0

o

o 0

0.02

O.O~ 0

o

o0.)0'

0.19

o

.,78 0 0

1"5 0 0

,,,8 0 0

'''5 0 0

1,,8 0 0

1"5 0 0

.,,8 0 0

1"5 0 0

1,,8 0 0

1"5 0 0

1,,8 0." 0

1"5 0 0.05

1,,8 80.67 69.70

'''5 51.82 40.09

1,,8 4.26 11.71

'''5 16.71 29.60

7).35 86.16 94.60

51.20 Z).49 40.33

).80 1.60 0.01 ~1.2) ~.6

28.30 14.66 45.34 89.6

".17 58.24 0.53

8.33 10.34 I.~

oo

oo

2.52

I.~I

o'0.37

oo

1~.03 1.50

0.84

oo

o

o

oo

79.32 13.6~ 66.40 25.61 55.93 86.60

18.39 9.10 fl.77 38.70 14.16

o28.09

oo

oo

65.35 85.50 61.69

17.55 7.76 51.28

0.59 0.09 0.19

0.06 1.62

oo'.0

1.14 °o

o

°

12.31

".90

o

°1,,8 0

1"5 0

L....atona

Sond Rubble

lIoncorel

Ia.elt

Totol CorelCover

1978 15.07 18.57

1975 31.69 30.98

14.33 12.45

27.64

5.46 0.83 0.53

29.47 44.26 44.13

4.86 34.04 14.41 38.00

9.07 82.67 92.20 21.49

33.94 86.36 53.13 12.59 41.58 13.39

82.~ 91.14 17.71 60.06 85.37

Difference In coralcoyer bot""'.n 1975end 1978

16.62 12.41 13.32 24.01 43.43 43.60 '.81 48.63 77.79 16.51* 49.04 4.78 5.12 18.48 71.98

H'-SpeclesCover DI ver'Sl ty

1978

1976

0.47

0.62

0.94

0.76

0.63

0.71

0.59 0.61

1.1~

0.45

1.21

0.36

0.95

1.00

1.27

0.82

0.95

0.55

0.85

1.29

1. 14

1.21

1.06

1.61 0.94

0.70

1.61

0.83

0.58

0.83

"Higher coy.r In 1978.t_ .... No dat8 collected.to • Spec Ies not found. no l.

13

80 STATION A 1.6 STATION A

60 1.2

40 0.8

20 0.4

0 0.0

80 STATION B 1.6

60 1.2

-J:40 ~ 0.8

>-20 I- 0.4

(/)

a:: a::ww 0 > 0.0

>0

STATION C0

STATION Cv 80 w 1.6.J Cl<X <Xa:: 60 a:: 1.20 wv >.J 40 0 0.8<X vl- I0 20 (/) 0.4I- w~ 0

u0.00 w

a. /j

STATION D(/)

-,,-"STATION D80 .J 1.6<X

60 I- 1.20I-

40 0.8

20 0.4

0 0.0

80 STATION E 1.6 STATION E

60 1.2 A--- 1975 Ii --- 1975

40 -- - 1978 0.8 - --1978I

20 0.4 I-

0.020 40 60 80 100 120 0 20 40 60 80 100 120

TRANSECT DEPTH, It TRANSECT DEPTH, It

NOTE: Ft x 0.304 8 = m.

FIGURE 3. VARIATION OF TOTAL CORAL COVER AND SPECIES COVER DIVER-SITY WITH DEPTH AT EACH TRANSECT, 1975 AND 1978, MOKAPUOUTFALL, O'AHU

14

20

1978STATION A Montipora spp. 0

Poct/lopOra meandrina 1//1Porites lobata f:;/rJPorites compressa •

10080

1975

////

~~ ;;I ;; ~;:.~;:.[;.·.•i;;11;;;;:..:••......:..;:;.•.::;;

/ /;;/;; :~::.•..:~;::: :~ ::::::;: ;~~~i·II:III\!oL....c:::::I.<::..L.~a. __---'=~~;;;:;:;:l__...c:=:L~=~

-1..--1LL..=

20 40 60

10

a: 10lJJ

6<..>~ol-I-o(I)

cfl 20

DEPTH, It

NOTE: Ft X 0.304 8 = m.

FIGURE 4. PERCENT COVER OF FOUR DOMINANT CORAL SPECIES, STA­

TION A, MOKAPU OUTFALL, O'AHU, 1975 AND 1978

1978

10

0::::::;:;

a:lJJ

1975>0<..>~ 300l-I-0(I)

~ 200

10

020 40

STATION 8

Ill'

;;160 80

Montipora spp. 0Pacillopora meandrtna[22]

Porites lobata [J]

Porites compressa •

100

DEPTH, It

NOTE: Ft X 0.304 8 = m.

FIGURE 5. PERCENT COVER OF FOUR DOMINANT CORAL SPECIES, STA­

TION B, MOKAPU OUTFALL, O'AHU, 1975 AND 1978

15

30

1978

20

a: 10w>0u~0 0~ 1975~0CD

~ 200

10

STATION C

IMontiporo spp. 0Pocilloporo meondrino k /1Porites lobata (::::::::::1

Porites campresso •

20 40 60

DEPTH, ft

NOTE: Ft X 0.304 8 = m.

FIGURE 6. PERCENT COVER OF FOUR DOMINANT CORAL SPECIES, STA­TION C, MOKAPU OUTFAll, O'AHU, 1975 AND 1978

Montipora are grouped together because many of these species are so morpho­

logically similar that they are indistinguishable in the transect photo­

graphs. Figure 9 shows the number of coral species at each transect during

both the 1975 and 1978 surveys.

By conducting repetitive surveys at the same locations in successive

years, one can distinguish changes and effects in both space and time.

When the benthic-cover data obtained in the 1978 survey is compared to the

1975 survey data, no clear and consistent patterns associated with the out­

fall location are evident. The only pattern that does occur is that coral

cover was lower on all but one transect in 1978. This trend does not ap­

pear to be correlated with outfall stress since some of the greatest dif­

ferences occurred at stations farthest from the source of discharge. In­

stead, the major differences that did occur appear to be the result of

patchy distribution of benthos and substrate types rather than biotic re­

sponses to outfall stress. ($ee discussion below.)

The greatest differences occur at the outfall site (station B) where

coral cover of all species, number of species, and species cover diversity

16

60 ....--------------------------------.....,

50

1978 STATION D

Montipora spp. 0Poci//oporo meandrino 1221

40

30

20

a: 10lJJ>0u::E0 0t- 1975t-Oco~ 500

40

30

Porites /obato

Porites compresso

Iiill

•

20 40

DEPTH, ft

60

NOTE: Ft X 0.304 8 = m.

FIGURE 7. PERCENT COVER OF FOUR DOMINANT CORAL SPECIES, STA­TION D, MOKAPU OUTFALL, O'AHU, 1975 AND 1978

1978

20

10

ol-__--l=t;;;;;:;:a..- ~L.£i:i:i:i<

1975

0:: 60W

~U

~o 50l-I-om;f!. 40

30

20

STATION E

Montiporo spp. 0Pocil/opora meondrina I22JPorites lobata liDPorites compressa •

17

DEPTH. ft.

NOTE: Ft x 0.304 8 = m.

FIGURE 8. PERCENT COVER OF FOUR DOMINANT CORAL SPECIES, STATION E,MOKAPU OUTFALL, O'AHU, 1975 AND 1978

19

were lower in 1978 (Figs. 3, 5, and 9). In contrast, observations showed

that an enhancement of the community had occurred at the outfall structure

itself due to settling of various benthic forms on the complex substrata

formed by the diffuser pipe and boulder cover. The other area of greatest

cover difference between 1975 and 1978 occurred at station E60, the station

farthest from the outfall diffuser. Stations C and D, between stations B

and E, had relatively similar community structures at both surveys while

station A, closest to the outfall, showed consistently less coral cover and

lower diversity in 1978 relative to 1975.

Appendix B gives a brief summary of each transect location during the

1978 survey, describing both the physiography of the substratum and the

dominant macrobenthos that inhabit the area.

Discussion

The environmental variables seeming to affect coral community struc­

ture most directly are wave energy which causes skeletal breakage and tis­

sue abrasion, available light energy associated with photosynthetic and

calcification processes, available solid substrata for larval settling,

sedimentation that may smother corals, and interspecific competition be­

tween corals and other benthic forms. The relationships of these natural

factors to the coral communities located at the five study stations in

Kailua Bay are discussed by Russo et al. (1977).

Possible causative factors of stressed benthic communities which have

received particular attention in the past include increases in nutrients,

turbidity, sediments, and various toxins (EPA 1976). It is possible that

all exert· some influence on the distribution and abundance of the benthos,

and some effects are probably synergistic (Grigg 1978). Human activity can

also alter coral community structure by creating artificial changes in some

of the above variables. The major environmentally significant aspect of

the delivery of organic matter (sewage) is nutrient loading and consequent

cultural eutrophication of the ecosystem (Smith 1977). Accumulation of

organic-laden sediment emanating from the outfall discharge or from passage

through the food chain can modify or cover substrates causing them to be­

come unsuitable for settlement of many epibenthic species (Grigg and Kiwala

1970). While sewage outfall discharge can increase turbidity, causing a

decrease in the light energy available for photosynthetic activity, an

20

effect of sewage effluent on reef corals appears to be domination of the

hard bottom substrates by epifaunal filter feeders dependent upon suspended

organic materials in the water column. These filter feeders can success­

fully outcompete corals for space and light. Benthic algal blooms that are

attributable to eutrophication from sewage outfalls also have resulted in

reduced settlement and smothering of corals in nutrient-rich outfall areas.

Two sewage outfalls on O'ahu have been shown to cause these types of

effects on coral communities. Within 500 m of the old Sand Island sewage

outfall, Grigg* has observed bottom communities dominated by mounds of

deposit-feeding polychaete worms (Chaetopterus sp.); corals were totally

lacking. Between 500 and 1 000 m the Chaetopterus mounds disappeared and

substratum consisted of either sand or limestone. Echinoids, zoanthids,

and calcareous algae were the dominant macrobenthos in this zone. Beyond

1 000 m, living corals and associated species gradually increased in abun­

dance up to a distance of 6 000 m. The highest species diversity of the

macrobenthos was observed at stations of intermediate distances where nor­

mally dominant species were less abundant and species associated with the

outfall were present.

Likewise, Kane'ohe Bay, O'ahu, has been chronically polluted by sewage

as well as subjected to substantial terrestrial input from sediment-laden

stream runoff. Today, the southeastern sector of the bay, the area receiv­

ing large amounts of both sewage and stream flow, bears little resemblance

to a coral reef. Most areas once supporting coral? now have a variety of

filter feeding organisms--barnacles, sponges, tunicates, oysters, poly­

chaetes, etc. The central sector presents a picture of a coral reef commu­

nity with conspicuously altered biological characteristics. In particular

the green alga Diatyosphaeria cavernosa has displaced corals, primarily

Porites compressa on the reef slopes of that sector (Smith 1977). Present­

ly the sewage discharge into Kane'ohe Bay is suspended, and the resulting

responses of the communities to this relaxation of stress are being moni­

tored.

However, these types of responses to sewage stress do not appear to be

taking place in Kailua Bay approximately 1 yr after commencement of outfall

operation. On the contrary, the outfall structure itself is creating addi-

*R. Grigg 1978: Personal communication.

21

tional hard substrate area for coral colonization; and numerous small colo­

nies, most of which appear to be PooiUopora meandrina and Porites lobata,

were observed on the large basaltic boulders that are placed over and adja­

cent to the outfall pipe. The bryozoan Triphyllozoon hirsutum Rusk was also

observed abundantly on these outfall boulders at the 24- to 30-m (80- to

100-ft) depths. This was the only location in the entire study area where

Triphyllozoon was observed. The boulder stacks also form an area of habi­

tat space that is far more complex than the broad flat pavement that the

outfall pipe bisects. Several spiny lobsters,PanuZirus spp., were observed

in the shelter of the interstices between the boulders, as wer; several

species of sea urchins, Heterooentrotus mammiZatus, and Eohinothrix spp.

In this sense, the outfall pipe and adjacent boulders are acting as an

"artificial reef" in an area which has extremely low relief and is barren

of extensive settlement.

None of the benthic filter feeders or benthic algae mentioned as being

common around the Sand Island and Kane'ohe Bay outfalls were observed in

the immediate vicinity of the M6kapu outfall. The only abundant filter

feeder that has colonized the area is TriphyZZozoon hirsutum, and this spe­

cies is presently limited to the outfall structure itself, appearing in

relatively small clumps with large areas of bare substrata still available.

It is possible that the combination of a relatively low discharge rate

(0.4 m3 js or 9 mgd) and relatively strong and variable current velocities

of up to 1 knot around M6kapu Point (Bathen 1972) disperse the effluent

rapidly enough so that the increase in suspended organic material is not

great enough to support dominating communities of filter feeders or leafy

benthic algae like those found in the proximity of Sand Island or Kane'ohe

Bay. This reasoning is supported by the observation that there is no evi­

dence of effluent discharge in the surface waters of Kailua Bay. At Sand

Island the discharge location was readily apparent from the surface, both

by sight and odor.* Also, the discharge effluent at Mokapu has been ob­

served to disperse rapidly in the water column; visual effects of impair­

ment of water clarity were not apparent except within about 2-3 m of the

discharge exits in the outfall pipe (Plates 2 and 3).

The abundance of the bryozoan, TriphyZZozoon is also significant with

*R. Grigg and M. Palmgren 1978: Personal communication.

22

PLATE 2. DIFFUSER VENT IN MOKAPU OUTFALL PIPE, O'AHU, 1978.PLUME OF SEWAGE CAN BE SEEN PULSING FROM THE VENTIN THE LOWER CENTER OF THE PICTURE. NOTE WATERCLARITY ADJACENT TO OUTFALL VENT, INDICATING THATDISCHARGE AREA IS RAPIDLY FLUSHED. ALSO NOTELACK OF SEDIMENT ACCUMULATION ON BOULDERS ADJA­CENT TO VENT.

PLATE 3. EXPOSED MOKAPU OUTFALL DIFFUSER PIPE, O'AHU, 1978.NOTE HIGH NUMBERS OF FISH AROUND DIFFUSER.

23

respect to physical parameters of the waters near the diffuser. Soule and

Soule, research fellows at the Alan Hancock Foundation, University of

Southern California, state in an unpublished manuscript that no bryozoans

are found where rapid dispersion of fine sediments is taking place. Grigg

(1978) observed no bryozoans at stations up to 4 miles (6 436 m) from a

sewage discharge off Palos Verdes, Calif. Turbulence is also a controlling

factor for bryozoans. The erect, branching forms are too fragile to toler­

ate wave action; and even the tight-clinging, encrusting forms grow only on

the protected surfaces of rocks and coral heads. However, bryozoans do not

tolerate stagnant water well. The polyps must be provided with moving

water for filter-feeding and excretory exchange.*

The Mokapu outfall diffuser seems to be an ideal habitat for TriphyZ­

Zozoon hirsutum. The organic load of the surrounding water is high enough

to provide abundant material for filter feeding. However, this load is

presently low enough and water movement is high enough to prevent sedimen­

tation that is a limiting factor to bryozoans. Since the diffuser is below

normal wave base of 24 to 30 m (80-100 ft), water movement is not intense

enough to be destructive to the colonies. Therefore, the abundant appear­

ance of bryozoans is a good indicator that the physical condition of the

environment is presently not stressed with respect to sewage-induced sedi­

mentation.

Another possibility is that the time since discharge commencement has

not yet been long enough for the community to undergo the successional

changes to a climax community of filter feeders or algal domination. It is

possible that the community is now in some preliminary stages where organic

material levels are building to a threshold point, after which filter

feeders and leafy algae will begin to proliferate.

Substrates may also require time to proceed through conditioning

stages, after which new forms will begin to settle and grow. As noted pre­

viously, corals have settled on the new substrates immediately adjacent to

the direct flow of the outfall. These colonies are still less than several

centimeters in size; presumably because corals are known to require condi­

tioning of their substrate (Harrigan 1972), growth is relatively slow.

However, the clumps of TriphyZZozoon are presently as large as 25 to 30 cm

(Plate 4). It will be interesting to see if the present relationship con­

tinues, and, if so, to what degree the bryozoan outcompetes the corals for

*D.F. Soule and J.D. Soule 1978: Personal communication.

24

PLATE 4. BRYOZOAN, TRIPHYLLOZOON HIRSUTUM BUSK, GROWING ONOUTFALL BOULDERS, MOKAPU OUTFALL, OIAHU, 1978.LARGEST COLONIES ARE APPROXIMATELY 30 CM IN DIAM­ETER. EXPOSED OUTFALL PIPE SURFACE IS AT LEFT.

space on the outfall boulders. It is also possible that other filter feed­

ers will begin to settle and proliferate in the outfall area, outcompeting

TriphyUozoon. No "before-after" studies have been conducted previously on

sewage stresses in Hawai'i, so there is no information base with which to

compare the observed pattern of change at M6kapu Point. It may be that the

Sand Island area went through a similar period of small coral and bryozoan

abundance prior to the population explosion of Chaetopterus worms.

Hopefully, the third survey, proposed for the summer of 1979, will

provide additional data to show what the effects of the effluent discharge

are on community successional patterns. If colonization and growth on the

new substrate continue to be mainly corals and other organisms not asso­

ciated with severe sewage stress, then it may be concluded that for at

least two years the outfall has had no negative, and even some positive,

effects on coral reef and reef animal growth.

Apparent dissimilarities between the corresponding transects of the

1975 and 1978 surveys could have been from several causes. The most obvious

cause for less coral cover at the later date would be adverse effects of

25

sewage introduction to environment. However, this does not seem to be the

case. As stated previously, none of the detrimental effects of sewage-­

turbidity, sedimentation, proliferation of algal blooms, or high concentra­

tions of benthic filter feeders or algae--are in evidence. Also, the

greatest decrease in coral cover (other than at the outfall station) occurs

at stations A and E. Station E is farthest away from the outfall and would

be expected to exhibit the least change in coral cover if the range of in­

fluence of sewage were responsible for the noted decrease.

What does seem to be the cause of the variance is the inexact replica­

tion of the transects. It appears that natural variability from patchiness

of bottom topography and coral cover and the variability of transect loca­

tion caused by inexact navigation is of a magnitude great enough to mask

any changes caused by sewage stress.

While it would be expected, under random patchy conditions, that as

many transects would have greater coral cover in 1978 as in 1975, this was

not the case. On only one transect (D20) was the coral cover higher in

1978. While this result appears to be caused by some nonrandom phenomena,

examination of the areas involved provides reasons for the unexpected dis­

tributions.

In 1975 station B showed coral cover of 29.5, 44.3, and 36.5% at the

6, 12, and 18 m (20, 40, and 60 ft) transects, respectively. In 1978 the

same transects showed coral cover of 5.5, .8, and .5%. Although this

reduction could be the result of outfall construction that proved to be

lethal to corals in the immediate area, it seems that the bottom topography

of the two transects is different enough to conclude that the locations are

different. With the exception of B20-78 which was located in an area en­

tirely of basalt substrata, most of the substrate at the 12- and l8-m depths

was unconsolidated sand and rubble, and a flat limestone pavement mostly

devoid of benthic cover. In contrast, the 1975 transects all appear to

have occurred on patches of limestone veneers of active reef growth. It

seems that the small variation in horizontal distance within the study area

reflects large differences in community structure and the factors that

affect this structure. In this case, this proves to be an advantageous

situation since the area where the outfall occurs is mostly barren; and,

initially at least, the outfall is providing settling sites for a more

diverse substrata. On the other hand, the benthic communities in the area

26

surveyed in 1975 may have been more damaged by outfall construction.

Similarly, the percent coral cover at transects E60-75 and E60-78 were

85.4 and 13.4%, respectively. Much of the coral cover in the area of the

1975 survey was one species, Montipora patuZa (62.4%). This species was

not recorded at all on the 1978 transect. The high abundahce in the first

survey was due to the transect location in the center of and parallel to

the depth contours of a small area of steep vertical relief. Seaward of

this small cliff area the substrata were sand and coral rubble, while the

shoreward side was a flat limestone shelf with numerous encrusting species.

It appears that M. patuZa has the adaptive advantage of populating steep

vertical areas by growing in an overlapping plate-like form. This growth

form is rarely observed on flat areas. The steep cliff area encountered in

the 1975 survey area was very narrow, with a change of only about 4 verti­

cal meters and did not appear to be a common topographic feature in Kailua

Bay. Since the 1978 transect was not located on this cliff, bottom commu­

nity structure was markedly different between the two surveys. It is inter­

esting to note that even though the total coral cover at E60 was markedly

different, species diversity (HI) was closely parallel (Fig. 3). While

total coral cover varied considerably, both transects were dominated by one

species, P. Zobata in 1978 (86.3%) and M. patuZa in 1975 (73.1%).

The opposite situation with respect to species cover diversity occurred

at station D. In the 1975 survey transects D40 and D60 were conducted par­

allel to the upper and lower edges of a cliff area densely populated with

plates of M. patuZa. In the 1978 transect, the l2-m (40-ft) transect was

conducted on a flat reef veneer that was not clearly dominated by anyone

species. While the coral cover is greater on the 1975 transect (83%) com­

pared to 1978 (34%), the diversity relationships are reversed: .89 in 1975

compared to 1.45 in 1978. When coral cover is low, enough bare substrate

is available for a relatively large number of species to settle without com­

petitive superiority by one species. In contrast·, in areas where one spe­

cies can effectively outcompete other forms to dominate most of the avail­

able space, diversity is low.

Variability within very small areas is most clearly shown in station A.

This station was the easiest to relocate since it was positioned directly

off Mokapu Point and landmarks on the point were readily recognizable. How­

ever, results show that at the 6-, 12-, and l8-m (20-, 40-, and 60-ft)

27

transects the 1975 survey consistently showed higher total coral cover and

species cover diversity (Fig. 3). This result could be interpreted to re­

flect detrimental effects from the outfall causing a reduction of live

coral cover. If this were the case, it would be expected that higher lime­

stone cover would be recorded in the later survey since this is the compon­

ent including dead coral colonies. However, at all three transects lime­

stone cover was higher in the 1975 surveys, conducted before the sewage

outfall was constructed. Again it is concluded that small variation in

locations can reflect relatively large differences in benthic community

structure. This area is directly off a point projecting into the area of

highest wave activity and current energy. Apparently these are the factors

which affect coral community structure in this area since there is no pau­

city of hard substrata and the most common species is P. meandrina. This

coral is considered a fugitive species since it is first to colonize areas

of new substrata and occurs in areas too harsh, with respect to wave energy,

for other species. Relatively small changes in depth and distance from the

shoreline cliff around Mokapu Point are apparently enough to reflect changes

in community response to factors of wave stress. This is most clearly seen

at the 6-m (20-ft) transect which showed 23% P. meandrina cover in 1975 and

only 7.6% in 1978.

MICROMOLLUS KS

Methods

The micromollusks described below were obtained primarily on transects

C, D, and E. A single sample from a l2-m depth (40 ft) was obtained on

transect A; and, of the two samples from transect B (excluding the two sam­

ples from the diffuser), only the sample from 24 m (80 ft) had sufficient

specimens for analysis.

Micromollusks were analyzed as described previously (Russo et al.

1977). Sediment samples obtained by hand by scuba divers at depths of 6 to

24 m (20 to 80 ft) were picked for shells under a binocular dissecting

microscope from volumes of 25 cm~ The micromollusks were then separated

to species, counted, and analyzed for species composition and species diver­

sity. In this report the term "abundance" is substituted for "standing

crop" used in the previous report (Russo et al. 1977); it was determined as

28

was standing crop in the earlier report, by dividing the number of shells by

sediment volume. Figures for abundance are minimal in that they do not in­

clude fragments and juvenile shells too small for identification. Species

diversity indices were calculated from the Shannon-Wiener function, HI =rpilog~Pi (Pielou 1969). Species composition is represented by relative

abundance values for various groups and species.

Results

Abundance, species diversity, and species composition of the micro­

molluscan assemblages are shown in Table 4, and the distribution of these

parameters on the transect lines is shown in Figures 10 to 13. In the

following discussion, the samples are separated into two groups of stations,

at 6- to l2-m (20- to 40-ft) depths and 18- to 30-m (60- to 100-ft) depths.

This separation was suggested by differences in species composition which

were confirmed by analysis utilizing the Sorenson coefficient of similarity

which demonstrated two clusters of assemblages, a shallow water assemblage

at 6 to 12 m and a deeper water grouping at 18 to 30 m.

As in the 1975 samples, gastropods comprise between 86 and 100% of the

micromolluscan assemblages on transects C to E. Most of the gastropods are

epifaunal; hence, the assemblage is largely a weed- or rubble-associated

assemblage rather than one associated with infauna.

At depths of 6 to 12 m (20 to 40 ft) on transects C through E, average

abundance is 7.1 shells/cm 3• Four groups of micromollusks comprise about

50% of the assemblages on each transect: the archaeogastropod TpicoZia

vaPiabiZis, the rissoids Rissoina ambigua and R. miZtozona, the cerithids

Bittium paPcum and B. zebPum, and species of the family Triphoridae. At

depths of 18 to 30 m (60 to 100 ft), average abundance is slightly higher,

9.1 shells/cm 3, than at the 6- to 12-m (20- to 40-ft) depths. The dominant

species at the deep stations are the rissoid VitPieithna marmopata, the

dialid CePithidium peppaPVuZum, species of the family Triphoridae, and

TPicoZia.

At the 6- to 12-m depth interval abundance, species composition, and

distribution are in the main similar to those described in 1975; but some

differences, especially with respect to the proportions of species present,

are apparent. Overall abundance at this depth interval was little changed

with respect to the 1975 abundance figure (7.1 shells/cm 3 vs. 7.6 shells/

TABL

E4.

ABUN

DANC

E,SP

ECIE

SD

IVER

SITY

,AN

DSP

ECIE

SCO

MPO

SITI

ON

OFM

ICRO

MOL

LUSK

SAT

TRAN

SECT

STA

TIO

NS,

MOK

APU

OU

TFA

LL,

OIA

HU

,19

78

Stl

ltlo

n*C2

002

0E2

0A4

0Cl

tO04

0E4

0C6

006

0E6

0B8

008

0D

lff.

At

Dlf

f.Bt

~o.

mlc

rom

ollu

sks

6241

425

515

145

125

188

3310

567

349

446

269

319

No.

/cm

!2.

516

.610

.26.

01.

85.

07.

51.

34.

22.

714

.017

.810

.812

.8H

'(s

pec

ies

div

ersi

ty)

3.6

4.4

2.3

4.8

4.1

3.6

4.1

1.2

3.4

4.3

3.4

4.1

2.8

3.4

No.

gas

tro

po

ds

6140

725

414

745

125

184

3210

258

323

407

267

316

%C

ompo

sIt

Ion

tT

rio

oti

ava

ria

bit

is25

1864

89

1417

----

147

4§

4

Ris

80in

aam

bigu

aJ3

4--

II4

--I

Ris

soin

aep

ham

ilta

--§

--I

2--

§--

----

I4

32

Ri8

soin

am

itto

sona

1514

§5

2223

23--

37

--4

I§

Vit

rio

ith

na

mar

mor

ota

37

--4

9--

5--

37

832

I4

Bit

tiw

np

ar=

lzeb

rum

6II

§5

----

----

----

--§

ceri

thid

iwn

perp

arvu

lwn

--§

----

2--

§--

234

4218

2332

Dia

tava

ria

----

--5

--§

§3

I--

5I

4724

Tri

ph

ori

dae

53

--9

910

5--

--14

25

46

*ln

dlc

ates

tran

sect

(A,

B,C

,0,

E)an

dde

pth

(20,

40,

60,

80ft

).tS

amp

les

at

dif

fuse

r.T

Per

cent

of

gas

tro

po

ds.

§Am

ount

too

smal

lto

beco

unte

d,

N 1.0

30

5.0

30 B

204.0

10

0

15 3.0

10

,'a,5 0 ..4.0

...... -J:, \, ,,., 'o-~-o 0'

E ~\

u 0 \

"-.... \

ci 30 Diii \

Z IX: ,~

UJ 3.0UJ ><.> 20 0 Dz<l ,0 (J)

0 IUJ

Z U:::> 10 IlD

, UJ

<l 'o----d, 0-

(J) 4.0 ,0

,\ ,,

50 E0-...... ,

"-0

40 3.0

E

30

20 4.0

1975

10 1978 1975

1978

0 3.020 40 60 80 100 120 20 40 60 80 100 120

DEPTH, ft DEPTH, ft

NOTE: Ft x 0.304 8 = m.

FIGURE 10. ABUNDANCE AND SPECIES DIVERSITY OF MICROMOLLUSKS ONTRANSECTS B THROUGH E, 1975 AND 1978, MOKAPU OUTFALL,O'AHU

31

25

1975 \1 \----- 1978 21 1 \

1 \I \

1 \~ 17 1 \0 1 \40 z I \0 13

I \.... I \

30 ::l 1CD I.. 0:: 9 I, .... I.. Cf) 0

20, , I'0 0 ,

1.. 5,

I, ,, I10

, ,,, ,I, 0

0'0

DiDID vtlf'iD17 48

13 44

9 40~0

Z 5 0, 360.... ' ..,Cf) ' ..0 I '0------0----_0 320-~

I")

12 rrit:(J/iD WlriDbili6 E0 u0 ~ 280z

8ILl, 0 24, z

4,

~, 0, z,, ,,-- ::l 20CD

0.. ".

~

16 Trlpllorldoe 16

12 12

/a...B 8 / '\

I ,I ,

I,

4I "4 I '0

0 ..

0.........

0A 8 C 0 E A B C 0 E

TRANSECT TRANSECT

NOTE: ft x 0.304 8 = m.

FIGURE 11. SUMMARY OF MICROMOLLUSCAN SPECIES DISTRIBUTION AND ABUNDANCEAT DEPTHS OF 60 TO 100 FT, 1975 AND 1978, MOKAPU OUTFALL, O'AHU'

32

TRANSECT C TRANSECT 0 TRANSECT E30

064%@20'

\\ \

20 \ 'a.. "\

\"."'0\

10

~" #,1)...

0Hi~~oino millozono,0 H/~~oino mlliozono

20 ' \,, \0' \

\10 \

\\\

0Vifricirhntl Vifricifhna Vifricithna

0~ 8 '\0 , \ ..0- " \

.. 'Z , \ 0'0 4 ~. \ ,... ~.

,• ,(/) \0 \ ~

\ ,Q. 0:E a. porcum /8. ztllJrum 8.parclllll /8. z_rum0U

8

4

0Trip horldo. Triphorido. Triphorldoe

15

10 ,0, \

,/ \\

5 d \\\

\

0

DEPTH,ft

NOTE: Ft x 0.304 8 = m.

FIGURE 12. MICROMOLLUSCAN SPECIES COMPOSITION AT DEPTHS OF 20 TO 100FEET, MOKAPU OUTFALL, 1975 AND 1978

33

30Tricolio yorlobilis

20

10

1975

- ---- 1978

---0,"' ...

'0

Bittfum porcum

Rlssoino mll/ozono

,,~" ," ," ,,," ,"cI ", ,,,

O~I:::::.-~~-----==::::::::~H

4

01---------=---------;8

cf?-.i 20oI­en 10o0..:E8 0 r..-------------------l

EoC

TRANSECT

BA

24 r--r----,.---,------r---....,-......

4

O~..L___~.:..___..L.____.J. ~_J

20

~ 12z<toz 8:JCD<t

toE~ 16oz

EoC

TRANSECT

B

_........-o-----~,--- ""

'0

0 _

--------0' .. ........

0 .. ....' ....

A

4

8

Vllricithno mormor%

8

4

O~~----L----'------'--_--L---'

01-----------........---......-;12

Note: Ft x 0.304 8 = m.

FIGURE 13. SUMMARY OF MICROMOLLUSCAN SPECIES COMPOSITION AND ABUNDANCEAT DEPTHS OF 20 TO 40 FT, MOKAPU OUTFALL, 0 I AHU, 1975 AND 1978

34

cm 3). However, in 1978 there were proportionately more TricoZia, Bittium

parcum, and Vitricithna and lesser proportions of Triphora spp. in the sam­

ples than were recorded in 1975. Rankings of the most abundant species are

shown in Table 5, and the changes in rank as reflected in the general dis­

tribution of species are shown in Figure 13.

TABLE 5. MEAN PERCENT COMPOSITION AND RANKS OF SIX DOMINANT SPECIESOF MICROMOLLUSKS AT DEPTHS OF 20-40 FEET*, 1975 AND 1978,MOKAPU OUTFALL, O'AHU

1975 1978x % of x %ofSample Rank Sample Rank

Rissoina miZtozona 19 1 14.7 2

Triphoridae 9.7 2 4 5

TricoZia variabiZis 8 3 26.3

Rissoina anibigua 5.7 4 4.3 4

Bittium parcum 4.3 5 5.7 3

Vitricithna marmorata 1.6 6 4 5

*Ft x 0.304 8 = m.

Differences in species composition at the 18- to 30-m depth level are

not so noticeable as at the lesser depths, but there is a noticeable differ­

ence in abundance, from an average of 23.8 shells/cm 3 at these stations in

1975 to an average of 9.1 she11s/cm 3 in 1978. Vitricithna replaces Cerithi­

dium perparvuZum as the most abundant mollusk at these depths in the 1978

samples, and TricoZia variabiZis occurs in greater abundance (Table 6).

TABLE 6. MEAN PERCENT COMPOSITION AND RANKS OF FIVE DOMINANT SPECIESOF MICROMOLLUSKS AT DEPTHS OF 60-100 FEET*, 1975 AND 1978,MOKAPU OUTFALL, O'AHU

1975 1978- % of x % ofxSample Rank Sample Rank

Cerithidium perparvuZum 30 1 10.5 2

Diala varia 9 2 1 5

Vitricithna marmorata 7.3 3 15 I

Triphoridae 5 4 8 3

Tricolia variabilis 4.7 5 7.5 4

*Ft x 0.304 8 = m.

35

Comparison of the 36.6-m (120-ft) depth level samples on transect B

with the two samples from the diffuser area in 1978 show little change in

species composition but a major difference in average abundance from 22.7

she11s/cm 3 in 1975 to 12.8 shells/cm3 in 1978. Cerithidium perparvuZum was

the dominant species in 1975 and again in 1978; the ranking of the five

dominant species was about the same in 1978 as in 1975.

Discussion

Differences between the 1975 and 1978 micromolluscan assemblages in­

clude:

1. A generally lower abundance (number of shells/cm3 of sediment)

2. Increased proportions of Bittium parcum, TricoZia variabiZis, and

Vitricithna marmorata at the 6- to l2-m (20- to 40-ft) depth

levels and concomitant decrease in the proportions of Triphoridae

3. Increased proportions of Vitricithna at the 18- to 30-m (60- to

lOO-ft) depth levels.

The differences may in part be ascribed to the effects of the diffuser

system on the biota and may in part be associated with the patchy nature of

the substrate.

At the 6- to l2-m depth levels the three species which increased in

abundance between 1975 and 1978 were those associated with frondose algae

and/or increasingly soft substrata rather than hard substrates. High pro­

portions of all three are characteristic of micromolluscan assemblages

elsewhere on O'ahu where some stress has been identified (Kay 1978). It is

interesting that there are increases in abundance for all three species at

all the stations and concomitant decreases in sponge-associated species

(Triphoridae) at all three stations. But, while it is tempting to speculate

that the relative increases in abundance of the three species are associated

with increased nutrient content of the water, it is also possible to suggest

that the samples reflect a variety of substrates in the area. Dollar sug­

gests, for example, that the generally lower coral cover he recorded for this

report are the result of patchy distribution of the benthos and types of sub­

strates rather than biotic responses to outfall stress. Thus, the samples

reported here may also reflect the patchy nature of the substrate rather

than an actual change in abundance and species composition associated with

the diffuser system. It should be noted, however, that decrease in abund-

36

ance of shells at depths of 18-30 m (60-100 ft) parallels the finding in

Mamala Bay where decrease in abundance was noted following the opening of

the diffuser system in 1977 (Kay 1978).

CONCLUSION

From the results of this study, the following conclusions are drawn:

1. The fish population study showed no significant difference in fish

abundance, composition, or diversity at stations A, C, D, or E between

1975 and 1978.

2. Fish abundance and diversity increased significantly at the outfall

station (B) from 1975 (before outfall construction) to after outfall

operation in 1978. The formation of new substrate by the outfall con­

struction seems to have provided substrate for microscopic algal growth.

Coincident with this was a large increase in herbivorous fishes.

3. The biomass of algae did not change significantly at any of the stations

between studies.

4. Coral cover was lower on all but one transect in 1978. This trend does

not appear to be correlated with outfall stress since some of the

greatest differences occurred at stations farthest from the source of

discharge. Differences may reflect the patchy distribution of the

substrate.

5. The greatest differences in coral species-cover diversity of all species

occurred at the outfall.

6. Filter feeders (bryozoans) were abundant at the outfall site, probably

due to new hard substrate and an increase in suspended organic material

in the water column.

7. Similiarity coefficient and dendrograph analysis revealed a separation

of two clusters of micromolluscan assemblages, a shallow water assem­

blage at 6 to 12 m (20-40 ft) and a deeper water grouping at 18 to 30 m

(60-100 ft).

8. Differences between the 1975 and 1978 micromo1luscan assemblages include

(a) a generally lower abundance (no. of she1ls/cm 3 of sediment),

(b) increased proportions of Bittium parcum, Tricolia variabilis, and

Vitricithna marmorata at the 6- to l2-m (20- to 40-ft) depths and a con­

comitant decrease in Triphoridae, and (c) increased proportions of

37

Vitricithna at 18- to 30-m (60- to 100-ft) depths. These differences

may in part be associated with patchy substrate.

REFER~NCES

Bathen, K.H. 1972. A descriptive study of the circulation and water qua­lity in Kailua Bay, Oahu, Hawaii during 1971 and 1972. Tech. Rep. No. 29,Look Laboratory, University of Hawaii.

Davis, W.P., and Birdsong, R.S. 1973. Coral reef fishes which forage inthe water column. HelgoLander Wiss. MUresunters 24:292-306.

Dollar, S.J. 1975a. "Zonation of reef corals off the Kona Coast of Hawaii."Master's thesis, University of Hawaii.

1975b. Ecology of West Hawaii coastal waters: A preliminary reporton the relationship between community structure and environmental stressin three Kona Coast coral communities. Report to Water Resources ResearchCenter, University of Hawaii.

EPA and Sanitation District of Los Angeles County. 1976. EISjEIR FinalJoint Outfall System Plan: Vol. I. U.S. Environmental Protection Agency,C-06-1051-010, SCH-740-506-05.

Grigg, R.W. 1972. Some ecological effects of discharged sugar mill wasteon marine life along the Hamakua coast, Hawaii. Report submitted to C.Brewer and Co. and Theo. H. Davies and Co., Ltd., Honolulu, Hawai'i.

1978. Rocky bottom communities: Long term changes at Palos Verdes.In press.

, and Kiwala, R.S. 1970. Some ecological effects of discharged wastes---on marine life. Calif. Fish and Game 56(3):145-55.

Harrigan, J.F. 1972. "The planula larva of PociUopora damicornis: Lunarperiodicity of swarming and substratum selection behavior." PhD. disser­tation, University of Hawaii.

Hobson, E.S. 1974. Feeding relationships of teleostean fishes on coralreefs in Kona, Hawaii. Fishery Bull. 72:915.

Kay, E.A. 1978. Micromolluscan assemblages in Mamala Bay, 1977. WaterResources Research Center, Progress Report for the Department of PublicWorks, City and County of Honolulu, Hawaii.

; Reed, S.A.; and Russo, A.R. 1973. A baseline survey of benthic-'b-;-i-ot"-a in Kailua Bay. In The Quality of Coastal Waters: Second Annual

Progress Report, Tech. Rep. No. 77, Water Resources Research Center,University of Hawaii.

Maragos, J.E. 1972. "A study of the ecology of Hawaiian reef corals."PhD. dissertation, University of Hawaii.

Mueller-Dombois, D., and Ellenberg, H. 1974. Vegetation ecology. New York:John Wiley and Sons.

Patrick, R., and Strawbridge, D. 1963. Methods for studying diatom popUla­tions. J. Water Poll. Control Fed. 35:151.

38

Pielou, E.C. 1969. An introduation to mathematiaaL eaology. New York:Wiley-Interscience.

Russo, A.R.; Dollar, S.J.; and Kay, E.A. 1977. An inventory of benthicorganisms and plankton at Mokapu, O'ahu. Tech. Rep. No. 101, WaterResources ResBarch Center, University of Hawaii.

Smith, S.V. 1977. A preliminary report on the responses of a coral reef/estuary ecosystem to relaxation of sewage stress. In Proa. Third IntL.CoraL Reef Symposium, Miami, ,Florida, pp. 578-83.

Stein, J.E., and Denison, J.G. 1963. Limitations of Indicator organisms.In PoLLution and Marine EaoLogy, ed. T.A. Olson and F. Burgess, p. 323.New York: John Wiley and Sons.

Strasberg, D.W. 1966. Observations on the ecology of four apongonid fishes.Paa. Sai. 20:338-41.

Turner, C.H. 1965. The marine environment in the vicinity of the OrangeCounty Sanitation District's ocean outfall. Calif· Fish and Game 52:28.

____~; Ebert, E.E.; and Given, R.R. 1964. An ecological survey of amarine environment prior to installation of a submarine outfall. CaLif·Fish and Game 50:176-89.

39

APPENDICES

APPENDIX A. FISH SPECIES LIST, MOKAPU OUTFALLFOLLOW-UP STUDY, 1978. . . . . . . . . . . . . . . . . . . 41

APPENDIX B. DESCRIPTION OF CORAL STUDY SITES,MOKAPU OUTFALL, O'AHU, 1978. . . . . . . . . . . . . . . . 46

41

APPENDIX A. FISH SPECIES LIST, MOKAPU OUTFALL FOLLOW-UP STUDY, 1978(HI =Diversity Index J =Equitability Component [HI /H ' max])

Station A20

ThaZassoma baZZieui 8T. duperreyi 18Acanthurus nigrofusaus 37A. Zeuoopareius 7A. triostegus (sandvicensis) 2Ctenochaetus strigosus 2Chaetodon muZticinctus 4C. quadrimacuZatus 1Chromis Zeucurus 2PZectrogZyphidodon imparipennis* 1P. johnstonianus 4Stegastes fascioZatus t 2SuffZamen bursa 3Pervagor spiZosoma 3Scarus spp. 2Naso Zi turatus 2Parupeneus muZtifasciatus 2

Total Species: 17 TOTAL 100HI = 3.6J = .878*old name - Abudefduf irrrparipennistold name - Pomacentrus jenkinsi

Station A40

ThaZassoma duperreyi 30T. baZZieui 2Chaetodon quadrimacuZatus 3Acanthurus nigrofuscus 5A. oZivaceus 2SuffZamen bursa 7Rhinecanthus rectanguZus 1PZectrogZyphidodon johnstonianus 5Pervagor spiZosoma 4Parupeneus muZtifasciatus 1

Total Species: 10 TOTAL 60HI = 2.47J = .74

Station A60

ThaZassoma duperreyi 21Coris gaimardi 2Acanthurus nigrofuscus 8Naso Zituratus 2Ctenochaetus strigosus 7Chromis verator 2DascyZZus aZbiseZZa 2Chronis Zeuourus 8Stegastes fascioZatus 2Chaetodon ZunuZa 1C. quadPimacuZatus 7C. muZticinctus 6C. mi Ziaris 1Forcipiger f1avissimus 3C. coraZZicoZa 3Scarus spp. 1Parupeneus muZtifasciatus 6Pervagor spi Zosoma 3Canthigaster janthinopterus* 1Paracirrhites arcatus 1SuffZamen bursa 2MUZZoidichthys fZavoZineatus t 1Centropyge potteri 6

Total Species: 23 TOTAL 96HI = 3.97J = .874*old name - C. jactatortold name - M. sandvicensis

42

APPENDIX A--Continued.

Station A80

ThaZaBsoma duperreyi 20Aaanthurus nigrofusauB 7Naso Zituratus 1Zebrasoma fZavesaens 2Ctenoahaetus strigosus 21Chaetodon fremblii 3C. multiainatus 5Centropyge potteri 11SuffZamen bursa 2Pervagor spilosoma 1Anampses auvieri 1Foraipiger fZavissimus 2Saarus spp. 2Chromis leuaurus 7Canthigaster janthinopterus 4Paraairrhites araatus 2Aetobatus narinari 1Saorpaena aoniorta 1Parupeneus multifasaiatus 7

Total Species: 19 TOTAL 100H' = 3.56J = .83

Station 820 on Outfall

Chaetodon miliaris >30Chromis verator 5Abudefduf abominalis 15Kyphosus cinerascens 30MUlloidichthys aurifZa~a 10Ctenochaetus strigosus 6Naso unicornis 3N. literatus 2Monotaxis grandoculis 1Scarus spp. 2Parupeneus porphyreus 5

Total Species: 11 >109H' = 2.78J = .799

Station 820 10 m off Outfall

Thalassoma duperreyi 29Aaanthurus nigrofusaus 20A. leucopareiuB 3A. triostegus 4Plectroglyphidodon imparipennis 5P. johnstonianus 4Pervagor spi Zosoma 3Haliahoeres ornatissimus 1Coris fZavovittata 2Paracirrhites araatus 1P. forsteri 1Anampses spp. 2

Total Species: 13 TOTAL 75H' = 2.90J = .781

Station 840 on Outfall

Mulloidiahthys aurifZamma >20Chaetodon mi liaris >20Kyphosus ainerasaens >20Abudefduf abominalis >20Acanthurus triostegus 15A. olivaaeus 5A. nigrofusaus 5Naso li teratus 3N. uniaornis 2Chaetodon fremblii 2Thalassoma duperreyi 4T. baUieui 5Chromis verator 2Bodianus bilunulatus 2Scarus spp. 4Parupeneus multifasciatus 3

Total Species: 16 TOTAL >132H' = 3.48J = .866

Station 840 10 m off Outfall

Thalassoma duperreyi 3Chaetodon fremblii 1SuffZamen bursa 2Parupeneus multifasciatus 2MUlloidichthys auriflamma 2

Total Species: 5 TOTAL 10H' = 2.25J = .97

TOTAL

APPENDIX A--Continued.

Station 860 on Outfall

Kyphosus ainerasaensChaetodon mil iarisMUlloidiahthys aurif1ammaCtenoahaetus strigosusChromis veratorAbudefcluf abominalis

Total Species: 6 TOTALHI = 2.33J = .89

Station 860 10 m off Outfall

Thalassoma cluperreyi

Station B80 on Outfall

Kyphosus ainerasaensChaetodon miliarisAaanthurus olivaaeusMUlloidiahthys aUPif1ammaThalassoma cluperreyiBodianus biZunuZatusLutjanus kasmiraChaetodon frembZiiStegastes fasaioZatusHaliahoeres ornatissimusDasayZlus albisaeZZaCoris balZieuiAulostomus ahinensis

Total Species: 13HI = 2.96J = .797

>20>20>20

53

10

>78

4

>20>20

18>20

55

10221311

>108

43

Station 8 at 27.4 m (90 ft)on the Diffuser

MUZloidiahthys f1avolineatus >20Aaanthurus oZivaaeus >15Lutjanus kasmira >15Abudefduf abominalis >10Chromis verator 6Aaanthurus triostegus 4A. nigoris 2A. nigrofusaus 9Naso li turatus 4Chaetodonmiliaris 8C. frembZii 2Thalassoma duperreyi 3Parupeneus porphyreus 2P. muZtifasaiatus 4Ctenoahaetus strigosus 4Meliahthys vidua 2Anampses spp. 1

Total Species: 17 TOTAL >111HI = 2.96J = .71

Station C20

Aaanthurus triostegus(sandvwensisJ 7

ThaZassoma cluperreyi 2Suff1amen bzaosa 1Pervagor spi Zosoma 2

Total Species: 4 TOTAL 12HI = 1.62J = .81

Station C40

Aaanthurus nigrofusausThalassoma duperreyiPervagor spi losomaCtenoahaetus strigosusPZeatrogZyphidodon johnstonianusSuff1amen bursa

Total Species: 6HI = 2.02J = .78

TOTAL

1463311

28

44

APPENDIX A--Continued.

Station C60

Parupeneu8 muZtifa8aiatu8Da8ayZZus aZbiseZZesPervagor SpiZo8omaCanthigaster janthinopterusCentropyge potteriChaetodon miZiaris

Station 020

Aaanthurus nigrofusausA. triostegusA. mataThaZassoma duperreyiCtenoahaetus strigosusParupeneus muZtifasaiatusA. oUvaaeusSuffZamen bursaChaetodon quadrimaauZatusC. unimaauZatusC. frembUiC. muUiainatusCentropyge potteriNaso U turatusBodianus biZunuZatusStegastes fasaioZatusThalassoma balZieuiRhineaanthus aauZeatusCanthigaster janthinopterusPZeatrogZyphidodon johnstonianus

Total Species: 20 TOTALH' = 3.52J = .81

Total Species: 6H' = 2.37J = .91

TOTAL

421113

12

156

1318

5213122111111111

77

Station 040

ThaZas80ma duperreyi 15Stegastes fasaioZatus 9Ctenoahaetus strigosus 8Aaanthurus nigrofusaus 5Centropyge potteri 7Zebrasoma !Zavesaens 1Chaetodon unimaauZatus 6C. multiainatus 8Pervagor spiZosoma 3Saarus spp. 4Chromis spp. 2StethojuZis baZteata 1Canthigaster janthinopterus 1Paraairrhites forsteri 1Parupeneus bifasaiatus 1BaZistes spp. 1

Total Species: 16 TOTAL 73H' = 3.52J = .87

Station 060Lutjanus kasmira 41Chromis verator* 29Thalassoma duperreyi 9Ctenoahaetus strigosus 19Chaetodon unimaauZatus 13Chromis spp. 18Chromis leuaurus 8Aaanthurus triostegus 8A. nigrofusaus 2Zebrasoma fZavesaens 1ThaZassoma baUieui 2Parupeneus multifasaiatus 3Stegastes fasaioZatus 2Pleatroglyphidodon johnstonianus 2Naso U turatus 1Centropyge potteri 3Abudefduf abominalis 2Chaetodon ornatissimus 1Foraipiger fZavissimus 1Bodianus bilunulatus 1Saarus spp. 1Sufflamen bursa 1Pervagor spi losoma 1Parupeneus porphyreus 1

Total Species: 24 TOTAL 170H' = 3.54J = .77*Misidentified as Dasayllus trimaau­latus in Russo et al. (1977) study.

APPENDIX A-Continued.

45

Station D80

Chpomis ve~ato~* 26Ctenoahaetus swigosus 17Thalassoma duperreyi 10Sufflamen b~sa 4Pleawoglyphidodon johnstonianus 3Chae todon mi l iaris 2Fo~aipige~ flavissimus 2Chaetodon unimaaulatus 2Parupeneus muUifasaiatus 3MUlloidiahthys flavolineatus 3Chaetodon multiainatus 1Canthigaste~ janthinoptepus 1Cent~pyge potteri 1Saapus spp. 2COl'is gaimardi 1

Total Species: 15 TOTAL 78HI = 3.03J = .77*Misidentified as Dasayllus trimaau­latus in Russo et al. (1977) study.

Station E40

Thalassoma dupe~~eyi 17Ctenoahaetus strigosus 21Aaanthur>us nig~ofusaus 16Chaetodon unimaaulatus 7

. Stegastes fasaiolatus 6~omis leuauPUs 3Chaetodon multiainatus 3C. f~embUi 1Cenwopyge potteri 1Aaanthupus t~iostegus 2A. olivaaeus 2Pleat~oglyphidodon johnstonianus 2Chaetodon miUaris 1Thalassoma ballieui 2Canthiga8te~ janthinoptepus 1Fo~aipige~ flavissimus 1Pervago~ spi losoma 1Par>upeneus muUifasaiatus 1Anampses spp. 1Paraai~~hites araatus 1

Station E20

Thalassoma dupe~~eyi

Ctenoahaetus strigosusAaanthupus mataStegastes fasaiolatusAaanth~ leuaopareiusAbudefduf so~didus

Chaetodon miliarisC. quadrimaaulatusCanthigaste~ ainatusOst~aaion lentiginosum

Total Species: 10 TOTALHI = 2.83J = .85

12774222111

39

Total Species: 20HI = 2.85J = .66

Station E60

Ctenoahaetus strigosusAaanth~ wiostegusThalassoma duperreyiT. baUieuiChaetodon multiainatusC. miUarisC. lunulaC. f~embUi

Sufflamen b~sa

Bodianus bilunulatus, Paraai~~hi tes fo~ste~i

P. araatusOswaaion meleag~is

Co~is flavovi ttata

Total Species: 14HI = 3.12J = .81

TOTAL 90

186454311221111

TOTAL SO

46

APPENDIX B. DESCRIPTION OF CORAL STUDY SITES,M5KAPU OUTFALL, O'AHU, 1978

Station A20

Large basaltic boulders and wave-scoured basaltic bottom with encrust­

ing calcareous algae characterized this transect. Dominant coral cover con­

sisted of numerous colonies of PocilZopora meandrina; some flat encrusta­

tions of Porites Zobata; and, occasionally, small patches of Montipora spp.

and Pavona varians. Dead colonies of P. meandrina covered with algal

growth were also numerous. The only sea urchins observed were Echinothrix

diadema.

Station A40

Basaltic pavement and boulders were the major topographic features of

this area. Numerous large P. meandrina colonies, both alive and dead, and

small encrustations of P. lobata were common. Sea urchins observed were

Echinometra mathaei, Tripneustes gratiZla, and Echinothrix diadema. The

black sponge, Chondrosia chucaZZa,was observed on many of the dead coral

colonies.

Station A60

Basaltic pavement with less boulder cover than shallower transects at

Station A were found at the 18-m (60-ft) depth. Fewer P. meandrina colo­

nies were observed with the dominant coral species being encrusting P.

lobata. Limestone substrata occupied by boring Echinometra mathaei and

numerous small patches of the zoanthid PaZythoa tubercuZosa were common.

The sea urchins Tripneustes gratiZZa and Echinothrix diadema were occa­

sionally observed.

Station 820

Basaltic boulders covered with a filamentous algal turf and small coral

colonies, mainly P. meandrina, were observed at the area of the outfall.

The soft coral PaZythoa tubercuZosa and the black sponge Chondrosia chucalla

were observed occasionally as were the sea urchins Echinometra mathaei,

Tripneustes gratiZZa, and Echinothrix diadema.

47

Station 840

This transect was all coarse sand, limestone rubble fragments, and

basaltic pavement covered with sediment. Very few corals were observed on

the pavement, and these were limited to small patches of P. lobata, usually

less than 5 em in diameter. Abundant stands of Codium sp. and other fila­

mentous algae were observed in the sandy areas. No sea urchins were ob­

served in this area.

Station 860

Coarse sandy rubble and areas of hard pavement with short algal turf

were the main features of this area. Several areas of basaltic boulders

with small encrusting colonies of Montipora verrucosa and Porites lobata

were observed. No sea urchins were observed in this area.

Station C20

A flat, limestone-covered basaltic pavement with very sporadic macro­

benthos characterized transect C20. Corals present were mostly small, flat,

encrusting florms with the exception of some large well-formed hemispherical

heads of P. meandrina. The calcareous alga Porolithon sp. was noted on some

of the boulders as was the sea urchin Tripneustes gratilla.

Station C40

Limestone pavement and a fairly well-developed reef framework charac­

terized this area. Extensive lobata, flat, encrusting P. lobata, and hemis­

pherical P. meandrina colonies were numerous with small clumps of short­

fingered P. compressa. Most of this area consisted of a relatively complex

substrata in areas of higher coral cover with interstitial areas between

and under colonies. Several small patches of sand and coral rubble were

also observed. Black sponges were observed on many dead P. meandrina colo­

nies, and Palythoa tuberculosa colonies were occasionally present. Echino­

thrix diadema was the only sea urchin observed.

Station C60

This site featured flat limestone veneer with very little substrate

relief. Flat, encrusting species of P. lobata and large, flattened, hemis-

48

pherical clumps of P. meandrina were the only abundant corals observed.

Clumps of Porolithon and numerous sea urchings of the species Tripneustes

gratilla were also observed on the flat pavement.

Station 020

Here, a flat, limestone-veneer pavement with extensive encrusting spe­

cies, mainly P. lobata, M. verrucosa and M. patula, was found. Many of

these colonies had long narrow cracks produced by commensal alpheid shrimps,

Alpheus deuteropus. Pocillopora meandrina heads were sporadic as were

clumps of Porolithon sp. and some calcareous algae, Halimeda discoidea.

Echinometra matheai was the only sea urchin present, and these were observed

in holes bored in the limestone veneer.

Station D40

The topography of this transect was generally limestone reef structure.

The dominant corals were encrusting P. Zobata and M. ontipora sp. The coral

Pavona explanulata was very abundant at this transect, the only place in

this study where such concentrations of this species occurred. Palythos

tuberculosa and Porolithon sp. were also occasionally observed.

Station 060

This transect occurred on a sloping bottom (approximately a 30° grade)

that was almost entirely covered with flat overlapping plates of Montipora

spp. and Porites lobata. The remaining bottom cover was nonliving lime­

stone composed of dead coral skeletal material. Occasional E. matheai were

observed in this limestone.

Station 080

The substratum at this transect was predominantly sandy limestone

rubble with large, flat colonies of Montipora spp., Porites lobata, and

Porites (Synaraea) convexa. Clumps of P. compressa with long thin branches

were also present. No P. meandrina or urchins were encountered in this

area.

49

Station E20

Most of this transect consisted of irregular limestone outcrops

covered with a thin algal turf. Very few corals were encountered, and these

were predominantly small encrustations of Porites Zobata. Colonies of the

soft coral PaZythoa tubercuZosa were fairly abundant. Several sand patches

and sand channels intersected the boulder platform. High wave energy

appeared to be a consistent condition in this area. No sea urchins were

observed on any parts of this transect.

Station E40

This transect consisted of a relatively flat limestone pavement, with

the main coral species being large, well-developed colonies of P. meandrina;

flat, encrusting P. Zobata; and short-fingered clumps of P. compressa.

Pavona expZanuZata was also common. Urchins observed were Echinometra

mathaei in interstitial spaces of the limestone pavement, Tripneustes

gratiZZa, and Echinothrix diadema.

Station E60

A flat limestone pavement mostly devoid of corals was the major topo­

graphic feature at this transect. The only common species observed was

P. Zobata. Numerous Tripneustes gratilla, as numerous as 9 per quadrat were

observed, as were Echinometra mathaei, which were common in holes in the

substrata.