Indian Journal of Marine SciencesVol. 19,September 1990, pp. 165-170

Composition and distribution of interstitial meiofauna of the sandy beachat Gopalpur, south Orissa coast

Anita Pattnaik & M V Lakshmana RaoDepartment of Marine Sciences, Berhampur University, Berhampur 760 007, .India

Received 28 August 1989; revised 29 May 1990

Harpacticoid copepods are the most dominant group, forming nearly 70% ofthe total interstitial popula-tion of the beach. Nematodes (14.68%) are second in overall abundance. Other common groups are turbellar-ia, archiannelida, polychaeta and isopoda. Mean annual population densities are 245, 1401 and 191 individu-als per 10em- respectively at high, mid and lowtide levels. Seasonal changes in faunal densities are pronounc-ed. The total fauna exhibits 2 peaks, one of a very high magnitude (3225-5249) in summer (March-May) andanother of a lesser intensity in December. Horizontally the fauna is concentrated around the mid tide level andnumbers drop off rapidly more towards low water than at the upper levels. Vertically the fauna extends deepdown to the water table, but the bulk of the population is confined to the top 20 ern. Spatial and temporalvariations are controlled by physical factors of which temperature, salinity and beach stability areimportant. \ .

Quantitative studies on the interstitial meiofauna ofthe sandy beaches along the Indian coasts have beenmade at a few widely separated localitiesl-6. Alongthe Orissa coast there is but a single report on .thesystematics of these animals from the intertidal sandsat Puri and Konark 7. In view of this a detailed studyhas been undertaken on the ecology of interstitial fa-una of the exposed sandy beach at Gopalpur, southOrissa coast. This paper deals with the composition,population density, seasonal changes and horizontaland vertical distribution of the fauna, sampled at atransect during July 1983-June 1984.

Materials and MethodsThe physical characteristics of the beach at Gopal-

pur (19°16'N and 84°54'E) have been described". On a20 point exposure scale the beach is classified as expo-sed, being subjected to moderate to heavy wave ac-tion throughout the year.The beach sediment is com-posed mostly of well sorted medium sand of meanparticle size 250-350 urn. The beach is well drained;consequently the interstitial water is well oxygenatedand reduced layers are not encountered. Beach confi-guration undergoes drastic changes during the south-west monsoon, whereas for the rest of the year beachprofile changes are much less pronounced.

Sand samples were taken at the time of low tidesduring day at high, mid and low littoral levels. A pers-pex tube (5 em long and 2.5 em internal diam.) wasused to take cores stepwise to a depth of 15em at lowtide and mid tide stations and upto 25 em at the hightide level. Samples were taken twice a month and data

on these is used to study percentage composition, po-pulation densities and seasonal changes. For moredetailed observations on horizontal and vertical dist-ribution, collections were made at 5 m intervals fromthe high tide level to the waters' edge and to a depth of30-80 em at the different beach levels. These sampleswere taken on two occasions, in May and December1984.

Interstitial animals were extracted from the sedi-ment by Uhlig's sea water ice extraction? followed byanaesthetization'? with 6% MgCh. Animals were id-entified only to the level of major groups. Whole sam-ples were counted. Faunal densities are expressed asnumbers per surface area of 10em- as defined by Grayand Rieger!". Unless otherwise stated the numbers ofanimals given in tables and figures are the totals of thethree (or five) 5 em cores at the three tidal levels and themeans of the two observations in the month.

Results and DiscussionComposition-Fifteen meiofaunal groups were re-

corded at the transect (Table I). Of these ciliates, turb-ellarians, nematodes and harpacticoid cope podswere ubiquitious and also occurred in fairly largenumbers; gastrotrichs, polychaetes, archiannelidsand isopods were collected frequently and were occa-sionally abundant; coelenterates, oligochaetes, kino-rhynchs and halacarids were collected on many occa-sions, but in small numbers; rotifers, ostracods andcollembola were rare. Three features offaunal com-position need mention: all groups represented aretruly interstitial; larval forms of macroinvertebrates

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INDIAN J MAR SCI, VOL. 19, SEPlEMBER 1990

Table I-Population densities (no. 10 em - 2) of interstitial groups at high, mid and low tide levels

Groups 1983 1984 Mean(%)

July Aug. Sept. Oct. Nov. Dec. Jan. Feb. March April May June

High Tide.Level

Ciliata" VC C A A VC C VC VC VC VC VC CCoelenterata 2Turbellaria 25 2 13 20 33 68 32 44 10 43 12 47 11.86

Rotifera 2Gastrotricha 8 76 61 4.93Kinorhyncha 18 24 9 4 1.87

Nematoda 91 48 47 60 92 108 59 112 170 394 506 30 58.36Polychaeta 6 4 6 12 \0 4 1.43

Oligochaeta 2 6 4Archiannelida 4 2 6 4 14 4 1.16

Ostracoda 2Copepoda 43 8 27 46 14 96 12 . 2 34 198 6 4 16.66Isopoda 18 70 2.99Halacarida 2 2 4Collembola 2 2 2

Total 189 58 119 130 156 294 123 206 296 707 589 85

Mid Tide Level

Ciliata" A C VC C VC A VC C C C C VCCoelenterata 2 4 2 30 0.23Turbellaria 53 22 29 20 53 47 23 49 34 13 104 II 2.72Rotifera 2 2 2Gastrotricha 14 32 27 118 1.14

Kinorhyncha 4 2 2 26 4 4 0.23Nematoda 26 22 52 16 61 48 45 74 200 136 386 17 6.56Polychaeta 6 4 110 197 46 17 23 \0 2 2.47Oligochaeta 14 7 4 6 2 2 0.21Archiannelida- 4 2 6 6 124 72 9 9 14 116 190 3.28Ostracoda 2Copepoda 38 88 40 261 975 14 686 4956 3022 3674 144 82.67Isopoda 5 4 4 38 16 2 0.41Halacarida 2 2 2 4 0.06

Total 136 52 181 86 657 1374 173 868 5249 3225 4452 366

Low Tide Level

Ciliata" VC C C VC VC VC VC C VC A VC CCoelenterata 6 2 2 0.44Turbellaria 19 36 54 22 38 14 52 42 32 32 134 21 21.63Gastrotricha 6 11 30 2.05Kinorhyncha 2 6 \0 14 1.40Nematoda 42 6 30 36 6 27 21 32 54 44 100 27 18.53Polychaeta 2 2 \0 16 19 18 34 2 2 4.58Oligochaeta 14 6 6 8 4 1.65Archiannelida 4 2 12 2 6 2 2 2 II 1.48Copepoda 54 10 129 120 90 20 31 30 32 12 176 19 31.53Isopoda 356 2 6 8 2 16.31

Total 471 56 219 188 178 117 141 141 190 96 412 84

*C--Common VC-Very common A-Abundant

166

PATINAIK & RAO: MEIOFAUNA OF SANDY BEACH

which constitute temporary members ofmeiofaunawere seldom encountered; and the interstitial mol-luscs and tardigrades reported as frequently occur-ring on the beaches at Waltair '? and Puri and Kon-ark? were not collected so far.

A total of231 sediment cores were examined on the21 sampling dates at the three tidal levels. If data forthese are pooled (Table I) the harpacticoid copepodsrank as the most abundant taxon (68.39%) followedby nematodes (14.68%), the two groups accountingfor about 80% of the total population. Other groupsthat make cognizable contribution are the turbellari-ans (5.89%), archiannelids (2.81 %), polychaetes(2.54%) and isopods (2.4%). While nematodes aregenerally the dominant taxon in marine meiofauna,many early workers7.13 -15 reported the prepondera-nce of cope pods on exposed beaches with a mean par-ticle size greater than 200 urn. Based on theirexperie-nee with south African beaches McLachlan et af. IS

postulated that harpacticoids will be dominant in be-ach sands coarser than 330 urn, nematodes in finesand and that the two taxa will be equally important insands around 330 urn. Grain size analysis" of a largenumber of sand samples gives a mean particle diame-ter of310 urn for the average beach conditions at Go-palpur and harpacticoids are highly dominant here. Itwould thus appear that while the copepod fraction isundoubtedly greater in sands of coarser grades, thelimits of mean particle size around which their rela-tive proportion increases are somewhat variable anddiffer from region to region. Further the compositionof the fauna varies significantly between tidal levelswhere nematodes are the dominant taxon at the hightide level (58.36%), copepods are overwhelminglydominant (82.67%) at the mid tide, whereas at the lowtide the proportion of copepods is diminished beca-use of sizable contribution by turbellarians, nemato-des and isopods (Table I). Incidentally, the large per-centage (68.39) of copepods on the beach sands atGopalpur is much greater.:than that reported at com-parable east coast localitiest-P. At other areas invest-igated nematodes were dominant on the southwestcoast- as well as in the finer sediments at Porto Nov03,

Sagar Island" and Digha '. From the Andaman-Nico-bar group of islands Rao 16 reported a preponderance 0" 32 .s---a---../!I,,'t!l

of copepods, whereas in a single survey from the same ~ ' p_-8/area Ansari and Ingole" recorded a higher percentage ~ 28 \,' 210 ~of nematodes. e \8, Gf z

0.. ,/

Seasonal distribution-Seasonal changes in faunal 3 ' ,d' ;{d . d t- 2" -+---r---r-,.-.:<."'r--..--~--.----r-"--~"""T""-+ 16 C/)density of the various groups over the stu y peno are J A 5 0 " 0 J r M A M J

shown in Table I and of nematodes, copepods andtotal fauna at the mid tide level, in Fig. I. With theexception of polychaetes and kinorhynchs all groupsshow a maximum during summer (March-May). Ex-

ceptionally high population densities (no. 10cm -2)are recorded for copepods (3022-4956) in the threemonths. Nematodes attain a maximum density of 506at the high tide level in May. Polychaetes reach peaknumbers in colder months November-December andthis is also the period favourable to kinorhynchs eventhough they are present in small numbers. Archian-nelids exhibit two maxima, in May-June and Novem-ber-December. Copepods also show a minor peak inDecember. Seasonal fluctuations ofturbellarians arenot as pronounced as those of the above groups, butthey also occurred in largest numbers in May. Gastro-trichs were totally absent during July- December andthe highest population density for this group was inMay. The isopods occurred sporadically and the hig-hest numbers were recorded in July (low tide level)and April (high tide level).

Total fauna exhibits 2 maxima (Fig. I). Since thecomposition of total fauna is strongly influenced bycopepod numbers, seasonal population trends ofthese two components parallel each other (Fig. I). Ingeneral interstitial population densities at Gopalpurare poor during the southwest monsoon (June to Oct-ober), This is a period when the beach configurationchanges drastically at short intervals due to severeerosion or heavy deposition. Also, between Augustand October the salinity is the lowest for the year (Fig.I). These two factors are not conducive for the establi-

- NEMATODES

COI'Q'OOSIt

101000 I!)---[!j TOTAL FAUNA

300III...o:: 200-c:I:...z

100

--- TEMPERATIJR[

E1---1!l32 ro-)(

SALINITY

Fig. l=-Seasonal changes in population density at mid tide level inrelation to temperature and salinity of ambient water (numbers

for total fauna and copepods on logarithmic scale)

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INDIAN J MAR set, VOL. 19, SEPTEMBER 1990

shment of interstitial populations even though thetemperature is favourable (Fig. I). With the cessationof the monsoon, the populations recover in Novem-ber and reach highest densities in March-May (thelow population density in January is probably a sam-pling artifact). Rich summer populations are favou-red by increasing temperature, high salinity, stablebeach conditions and probably, greater food availab-ility. Summer maxima ofmeiofaunal densities werereported from other localities in India and were due toincrease in cope pod numbers". Where winter maximawere also recorded, these were due to increase in nem-atode populations+". In the present study the winterpeak is associated with rich populations of copepodsaugmented by polychaetes and archiannelids, the ne-matodes making little contribution. But for this devi-ation, the seasonal trends observed at Gopalpur arein conformity with the patterns reported at other Ind-ian localities'v'+".

100

...Cl

~Z••• 50u-r

Horizontal distribution-Data presented in Table 1allows the following generalizations regarding thehorizontal distribution of interstitial fauna on theGopalpur beach: nematodes especially and kinorh-ynchs to some extent, show a preference towards thehigh tide level; the soft-bodied groups turbellarians,oligochaetes and isopods are more characteristic ofthe low tide station; all the other groups find optimalconditions at the mid tide level.

In order to get a better picture of the horizontaldistribution, the fauna was sampled at closer inter-vals of 5 m along the transect on two occasions. Res-ults of the summer survey (15 May 1984) are shown inFig. 2A along with the beach profile on that date (Fig.28). While many groups were represented in the sam-ples, only three occurred in numbers large enough forgraphic presentation. The turbellarians were somew-hat evenly distributed along the transect. Nematodeswere dominant at the upper levels. Nearly 70% of the

b--A TURBELLARIA (n=63~)(!}----{!J NEMATOOA (n= 22321~ COPEPODA ( n= 270911(-- - ~ TOTAL FAUNA (n= -5808)

A~~--~~--~~--,.~

Ii

r BD C

'"30 25 20 15 10 0

DISTANCE fROM WATER EDGE (m)

H G o B "IolHWS H

c

MLWN

35

'

z r rr.·.. f' ,:~ :::: ;: .. , .;":~~ 20-30 H G E 0 B '"~ 30-40 (r.=331t) (r=666) (n=2445) (n=365) (n=270) (n='2'O)

40-5050-6'1

60-70

0-5

zo-eo

~ COPEPODS C

~ NEMATODES

!ill] TURBELL-'RI-,(n = 1325)

0 OTHERS

Fig. 2-Horizontal and vertical distribution of fauna (15 May 1984). A-norizolllal distribution; B-beach profile;C-vertical distribution

168

PAlT.NAlK & RAO: MEIOFAUNA OF SANDY BEACH

cope pod population is concentrated at substation Eand almost all of this is confined to the top 5 em. Asmuch as 81.63% of the total fauna occurred above themid tide level.

The observation that on beaches which are welldrained the meiofauna is concentrated around themid tide level and that numbers drop rapidly towardslow water and high water is well documentedl.13-15.Results of the present investigation are in agreementwith these findings. However, in contrast to what hasbeen reported from other parts of the world, interstit-ial animals at Gopalpur show a tendency towardsgreater numbers on the upper levels rather than on thelower shore. This is evident from the distributionshown in Fig. 2A and Table 1.Density (no. 10em - 2)at high tide (245) is considerably greater than at thelow tide (191). Turbulence resulting from moderateto heavy wave action for a greater part of the yearrestricts numbers towards the lower levels on the Go-palpur beach, whereas at the upper levels the faunaappear to be better adapted to withstand desiccation.Decreased turbulence, not too severe desiccation andadequate oxygen and food availability provide opti-mal conditions for the establishment of rich populati-ons around the mid tide level.

Vertical distribution-There was no consistent pa-ttern to the vertical distribution of the interstitial fau-na. On the basis of routine collections three generaliz-ations can be made: (i) the top 5 em usually had poorpopulations, particularly at the high tide level; but onseveral occasions copepods were present in large nu-mbers in these cores at mid tide; (ii) the coelenteratesand isopods were never taken in the 0-5 em cores and(iii) gastrotrichs were more common in the deepercores.

Vertical distribution of the fauna was studied in-tensively at 8 substations along with horizontal distri-bution and the results are shown in Fig. 2C. Whilepreparing this diagram the largest population in anycore (0-5; 5-10 ern etc.) at a particular substation istaken as 100% and numbers at other depth horizonsare represented in proportion to the latter. Again noconsistent pattern was observed except that at almostall beach levels approximately 80% or more of thepopulation is confined to the top IS to 20 em. Howev-er, above MTL where the water table drops deepdown the column at spring low tides, the fauna ext-ends to deeper zones. At substation F, at a depth of 80em, the total fauna is about 40% as rich as at thesurface.

Interstitial populations on the Gopalpur beach un-dergo vertical migrations within the sand column du-ring tidal cycle. After each tidal inundation the faunarealign themselves vertically at different depths. The

Table 2---Comparison of maximum meiofauna densities(no. 10 em - 2) of the sandy beaches along the Indian coast

Locality/Source Nematodes Copepods Totalmeiofauna

Porto Nov03 SandHigh tideMid tideLow tideAverage

Waltair3

Waltair13

Sagar Island+ SandDigha5 (st B)Andamans?Gopalpur(present study)

High tideMid tideLow tideAverage

5941150790(845)

18644818

(217)

9611960992

(1307)228

178-30034215266116

2185984597

134336888

506386100(331)

1984956176

(1777)

7075249471

(2142)

pattern of realignment is somewhat different aftereach submergence. Absence of any consistent verticaldistribution pattern at this locality is perhaps relatedto the vagaries of the migration behaviour of indivi-dual groups.

Comparison with other localities-In Table 2 inter-stitial population densities of the exposed sandy be-ach at Gopalpur are compared with other Indian loc-alities where quantitative data are available- -6. Ne-matode densities are much greater at Porto Nov03

and marginally higher at Digha ' and at both theselocalities the beach sediment is composed of finersand. High nematode densities are also reported fromthe Andamans" in sediments of mean particle sizevarying between 1.28-3.60 <1>. The mean (1777) andmaximum (4956) densities (no. 10em - 2) of copepodsat Gopalpur are the highest for the sandy beachesalong the Indian coasts so far reported. Total fauna isricher than that reported from other localities in pe-ninsular India and compares favourably with the richpopulations from the Andamans", but lower than thenumbers recorded on Malaysian beaches 17. J n gene-ral the population densities recorded at Gopalpur arericher than, or at least as rich as, those of the exposedtemperate and subtropical beaches in different partsof the world13.18,19.

AcknowledgementThe authors thank Prof. P.M. Misra for providing

facilities for this work. One of us (AP) thanks theauthorities of Berhampur University for the award ofa Research Fellowship.References

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INDIAN J MAR SCI, VOL. 19, SEPTEMBER 1990

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