DOCUMENT RESUME

ED 464 821 SE 066 100

AUTHOR Harding, Juliana M.; Mann, Roger; Clark, Vicki P.TITLE Shell Games. VORTEX: Virginia's Oyster Reef Teaching

EXperience.INSTITUTION Virginia Inst. of Marine Science, Gloucester Point, VA.REPORT NO VSG-99-13; VIMS-ES-47PUB DATE 1999-00-00NOTE 25p.; For a related VORTEX document, see SE 066 101.

Co-sponsors were Virginia Sea Grant Marine Advisory Program,Virginia Environmental Endowment, and Chesapeake BayRestoration Fund Advisory Committee.

AVAILABLE FROM Virginia Institute of Marine Science, P.O. Box 1346,Gloucester Point, VA 23062. Tel: 804-684-7302; Fax:804-684-7045; Web site:http://www.vims.edu/fish/oyreef/vortex.html.

PUB TYPE Guides Classroom Teacher (052)EDRS PRICE MF01/PC01 Plus Postage.DESCRIPTORS Critical Thinking; Elementary Secondary Education;

*Environmental Education; *Field Trips; *InterdisciplinaryApproach; Marine Education; Multimedia Instruction; ProblemSolving

IDENTIFIERS *Chesapeake Bay; *Oysters; Sustainability

ABSTRACTThis document introduces Virginia's Oyster Reef Teaching

EXperience (VORTEX), which is an interdisciplinary program focusing on theimportance of oyster reef communities in the Chesapeake Bay ecosystem. TheVORTEX program uses field and laboratory experiences supported by multimediainstruction. This document presents an overview on the biology of oysters,oyster reefs on Chesapeake Bay, the characteristics of their habitat, and howcitizens can help with the restoration process. (YDS)

Reproductions supplied by EDRS are the best that can be madefrom the original document.

00

Shell Games.

VORTEX: Virginia's Oyster Reef Teaching

EXperience.

Juliana M. Harding

Roger Mann

Vicki P. Clark

U.S. DEPARTMENT OF EDUCATIONOffice of Educational Research and Improvement

EDUCATIONAL RESOURCESINFORMATION CENTER (ERIC)This document has been reproduced asreceived from the person or organizationoriginating it.

CI Minor changes have been made to improvereproduction quality.

Points of view or opinions stated in thisdocument do not necessarily representofficial OERI position or policy.

PERMISSION TO REPRODUCE ANDDISSEMINATE THIS MATERIAL HAS BEEN

GRANTED BY

J. Harding

TO THE EDUCATIONAL RESOURCESINFORMATION CENTER (ERIC)

SE

VOS370

EHELL GAMES

NTRODUCTION

One of the more obvious features of many sandybeaches in the Chesapeake Bay region is the col-lection of shells visible between the tide lines.These shells are the creations of a wide variety ofmolluscs as well as prizes for beachcombers.Molluscan shells are calcium carbonate structuresmade by soft-bodied invertebrates in the phylumMollusca (Figure 1). The shell is secreted by theanimal and grows with the animal. Unlike hermitcrabs, molluscs do not ever leave their shells totransfer to others.

The molluscan shell has two main functions:

1. The shell is a hard protective barrier for the softbody of the animal. When a mollusc is threatenedby a predator or unfavorable environmental con-ditions, it simply retreats into its shell. When thethreat has passed, the mollusc emerges unharmed.

2. The shell provides muscle attachment pointsfor the soft bodied animal. The external skeletonor shell anchors the mollusc to its muscle systemsallowing it to move, eat, breathe, or burrow effec-tively.

The shell is the most recognizable feature of manymolluscs. The form of a molluscan shell is di-rectly related to its function and the lifestyle of theresident mollusc. The shells themselves are trea-sure troves of biological and ecological informa-tion provided the observer is attuned to the "clues"or morphological features that tell the animal'sstory. Muscle scars, shell shape, and shell thick-ness all can be used to infer details of the animal'slifestyle and habitat.

This sort of forensic ecology provides a simple,cost-effective means to encourage students of allages to develop qualitative and quantitative skillsincluding observation, hypothesis testing, data pre-sentation, and communication. The classroom ac-tivities described herein begin with a simple over-view of common Chesapeake Bay bivalves (BayBivalves) . The second activity (Oyster vs. Oys-ter) focuses on the Eastern oyster (Crassostreavirginica), one of the historically dominant spe-cies in the Bay. It sets the stage for the third activ-ity (Oysters and Reefs: How Shell Shape Definesthe abitat) which describes the importance of oys-ter reefs within the Chesapeake Bay ecosystem.

Figure 1: Representative Chesapeake Bay bivalveshells.

3

mulooda9,S5 ay,s5ile7 R46,177.dillo, Etpe. des-we

Related educational resources:

Harding, J.M., Mann, R., and V. Clark. 1999. Oyster Reef Communities in the Chesapeake Bay: A Brief Primer.Virginia Institute of Marine Science, Gloucester Point, VA. VSG-99-05, VIMS-ES-44.

Harding, J.M., Mann, R., and V. Clark. 1999. Oyster Reef Communities in the Chesapeake Bay [CD-ROM].Virginia Institute of Marine Science, Gloucester Point, VA. VSG-99-06, VIMS-ES-45. (see the ORCCB CDwebsite: http://www.vims.edu/fish/oyreef/orccb.html for release notes and CD updates).

The VORTEX (Virginia's Oyster Reef Teaching EXperience) website. http://www.vims.edu/fish/oyreef/vortex.html(provides regular updates on VORTEX program activities and resource materials).

The Bridge: An On-Line Ocean Science Resource Center for Teachers. http://www.vims.edu/bridge/ (see "biol-ogy" section for a list of links to websites on oysters and other molluscs).

The VIMS Molluscan Ecology Program website. http://www.vims.edu/fish/oyreef/reef_page.html (provides atechnical overview of ongoing oyster reef research and restoration activities in Virginia).

Harding, J.M., Mann, R., and V.P. Clark. 1999. Shell Games. Virginia Institute of Marine Science,

Gloucester Point, VA. VSG-99-13, VEMS-ES-47 11/99.

© 1999. VIMS VORTEX Program. All rights reserved.

This publication may be reproduced by educators for instructional use only. Unless otherwise noted, all pictures andillustrations contained herein are the property of Juliana M. Harding. Permission to reproduce or use any pictures sepa-

rately from the entire publication should be obtained directly from the authors.

www.vims.edu/fish/oyreef/vortex.html

Virginia Institute of Marine ScienceGloucester Point, VA 23062

2

VCCDEMZ

3AY 3IIVALVES

Although the waters of the Chesapeake Bay are hometo many molluscs, the Bay's bivalves are the most com-monly recognized and commercially important. Theyhistorically dominated intertidal habitats in terms ofboth ecology and physical presence. Bivalve molluscshave paired shell valves (Figure 1.1) joined at the hingeby a ligament. This ligament is much like our ownligaments and cartilage. The shell valves grow out-wards from the hinge structure. The shell valves arealso held together by adductor muscles. The hingeligament and adductor muscles work together to en-able the animal to open and close its valves at will.The valves must be open for the animal to breathe, feed,and release gametes (eggs and sperm). Bivalves arefilter feeders whose gills are specially modified for bothrespiration and food capture.

The shape of a bivalve shell relates directly to theanimal's lifestyle and habitat. This activity uses fourcommon Chesapeake Bay bivalves the hard clam(Mercenaria mercenaria), the Eastern oyster(Crassostrea virginica), the Atlantic Bay scallop(Argopecten irradians), and the Atlantic ribbed mussel(Geukensia demissa) - to provide a broad overview ofbivalve diversity and biology within the ChesapeakeBay.

Ligament

A. External view

B. Internal view

Figure 1.1. Generalized bivalve valves

Objective: Examine Chesapeake Bay bivalve shells andrelate shell shape and morphology to the lifestyle (Howdo they live?) and habitat (Where do they live?) of theanimal.

Skills: Observation, communication, hypothesis test-ing, and group collaboration.

Relevant Virginia SOL:LS.5 Classification of organismsLS.10 Organism adaptation to biotic and abiotic factorsBI0.5 Life functions

Materials: For each small group, at least one set offour types of bivalve shells including one each of hardclam, oyster, bay scallop, and ribbed mussel. Usematched pairs of valves if available; otherwise a singlevalve from each species will do.

Procedure:1. Divide students into small groups or "researchteams".2. Provide each group with one set of shells includinghard clam, oyster, scallop, and ribbed mussel valves.3. Using the worksheet on page 7, have students de-scribe and compare the shell valves within and betweenspecies in terms of:

- general shape qualitative descriptions (round,wing shaped, flat, etc.)

- quantitative measurements of shell height andshell width (see Figure 1.2 below)

Figure 1.2. Generalized shell valve showing locations ofmeasurements

NoVi08. lla .0.yrs5407 aerfRieduCIII§U-W eYt:ll*Ir§e*ce

- general appearance (texture, color, etc.)specific morphological features including loca-tion of the hinge and adductor muscle scars (seeFigure 1.1)

4. After they have initially examined the shells, giveeach group of students a set of local habitat descrip-tions (given below). Ask students to pair each bivalvewith a habitat. (Where do you think you would findthis animal?). Have them include justification for theiranswers based on their observations of shell morphol-ogy. . Some bivalves may be found in more than onehabitat.5. Review each group's responses as a class using theillustrated key on the following pages to emphasize re-lationships between bivalve form and function.

Habitat 1: Sand bottom. Sand bottom habitat is easyto burrow into and is often intertidal and adjacent toseagrass beds or oyster reefs.

Habitat 2: Reef structures. Natural reefs are three-dimensional structures made exclusively of attachedbivalves and their shells.

Habitat 3: Tidal salt marshes. Tidal marsh habitathas sediment suitable for burrowing and grasses suit-able for attachment of molluscs.

Related vocabulary:adductor muscle: one of the muscles that closes the

valves of a bivalve shell.

aggregate: group or gather together.

anterior: the forward or front section of an animalthat goes first during locomotion.

elliptical: oval or egg shaped, not round.

posterior: the rear or last section of an animal.

substrate: the bottom or surface to which an animalattaches

Suggested discussion questions:

1. External fouling and attachment scars are two of thefeatures that distinguish attached bivalves from bur-rowing bivalves. Why do you think burrowedbivalves lack either or both of these characteristics?

2. What are some of the risks and benefits associatedwith burrowing? How do these compare with thoseencountered by a bivalve attached to an exposedsurface?

3. Compare the four types of shells in terms of shellthickness. How do you think shell thickness re-lates to a bivalve's habitat and lifestyle?

External view

a)

0ta

Internal view

Muscle scars

Hard ClamMercenaria mercenaria

Description: Convex shell valves give this animal awedge-shaped profile. Anterior and posterior adduc-tor muscles are approximately the same size and musclescars are clearly visible on the shell interior as are hingeand ligament structures. Shell valves may be large andquite thick. Leading edge of the interior valves may bedark purple. Shell exterior is gently ridged.

Habitat: Sand bottom.

Lifestyle: The wedge-shape of the shell valves com-bined with a large muscular foot enables these animalsto effectively burrow into the sand. Once burrowed,the animal extends its two siphons to the sand surfacewhere they are faintly visible (called "keyholes" byclammers). The siphons transfer water into and out ofthe animal's body enabling it to feed, breath, and re-lease gametes while completely buried. Hard clamsare usually found in groups or beds.

Comments: Hard clams are the target of a commercialfishery in the Lower Chesapeake Bay. Hard clamaquaculture is a growing industry, especially onVirginia's Eastern Shore. Natural predators includecownosed rays, blue crabs, and several species of lo-cally occurring whelks (Channeled, Knobbed, Rapa).

External view

0.a

Internal view

0

Muscle scars

Atlantic Ribbed MusselGeukensia demissa

17)0FD

0

Description: Wing-shaped shell valves have obviousexterior fluting or ribs. Anterior end is gently rounded,posterior end is flared. Anterior adductor muscle issmaller than the posterior adductor muscle. Shell valvesare thin. Exterior color ranges from greyish white tobrown.

Habitat: Tidal salt marshes. May be half-buried in themud/peat bottom or attached to either the roots and/orstems of marsh grass or a hard surface.

Lifestyle: The wing-shaped valves help the animalpartially burrow into the soft marsh bottom. Musselsmay also attach themselves with protein threads to hardsurfaces, they do not have to be burrowed. If the ani-mal is attached to an exposed surface, the wing-shapedribbed shell is hydrodynamically suited to help pre-vent the mussel from being washed from its location.In either case, siphons extend from the posterior (flared)region and transfer water into and out of the animal'sbody enabling it to feed, breath,and release gametes.

Comments: Ribbed mussels are common in local saltmarshes. Natural predators include marsh crabs, rac-coons, and several species of marsh birds and fishes.

3

External view Internal view

Atlantic Bay ScallopArgopecten irradians

Description: Disk-shaped shell valves that have obvi-ous exterior fluting or ribs. Shell valves are very slightlyconvex and almost completely round. Single adduc-tor muscle is very well developed and muscle scar iscentrally located. Shell valves are thin. Exterior coloris greyish white.

Habitat: Sand bottom especially near and in seagrassbeds.

Lifestyle: The powerful adductor muscle can quicklyand repeatedly contract, forcing water out of theanimal's body by clapping the shell valves together.This enables the animal to swim quickly via "jet-pro-pulsion". The streamlined shell valve shape and exte-rior ribs enhance swimming hydrodynamics. Restingscallops may be partially buried in sandy depressionsthat they excavated with water jets created by the ad-ductor muscle. Scallops possess a well-developed sen-sory system that helps them detect and avoid potentialpredators.

Comments: Bay scallops rely heavily on seagrass habi-tat. The decline of seagrass (particularly eelgrass) bedsin the Chesapeake Bay since the 1960s has reducedsuitable habitat for these animals. Seagrass restorationefforts in the Bay and seaside estuaries of Virginia'sEastern Shore are also helping Bay scallop populations.Natural predators include rays (cownose and Atlanticstingray), starfish, and several species of locally occur-ring whelks (Channeled, Knobbed).

External view

Internal view

Muscle scar

Eastern OysterCrassostrea virginica

0En

Description: The shell valves are slightly oval with acupped left shell valve and a flattened right shell valve.Left shell valve is cemented to the bottom and containsthe body of the animal. Elliptical purplish adductormuscle scar is obvious. Exterior of the shell is greyishwhite, roughened, and thick. Leading growth edgesare thin, paler in color and may be quite sharp.

Habitat: Sand bottom in flat beds (bars) or in three-dimensional reef structures.

Lifestyle: The oyster begins its life as a microscopicplanktonic larva. Eventually, it settles onto hard sub-strate and cements its left shell valve to the hard sur-face. As the animal grows, the left shell valve cups andprovides protection for the animal's soft body. Growthoccurs in a direction opposite the hinge. Migration ofthe adductor muscle (and scar) from the hinge or old-est region toward the growth edge or youngest regioncontinues throughout the oyster's life.

Comments: Oysters naturally aggregate and can formlarge reef structures over time. Historically, oyster reefsdominated the ecology and physical geography of theBay. Oyster shells, either in reefs or flat bars, providehabitat for numerous other invertebrates (crabs, mus-sels, worms, etc.) as well as many fishes. Oysters havebeen fished in the Chesapeake Bay since colonial timesand before; shell piles or "middens" left by nativeAmericans are quite common in the Tidewater region.

Des

crip

tion

ofsh

ell s

hape

Hei

ght o

rw

idth

Des

crip

tion

ofte

xtur

e, c

olor

,et

c.

Sket

chsh

owin

gm

uscl

e sc

ars,

hing

e, a

ndot

her

feat

ures

Hab

itat

Har

d C

lam

,

Atla

ntic

r:b

bed

Mus

sel

Atla

ntic

Bay

Sca

llop

-, -

1.--

,

\VI.

.

,

Eas

tern

Oys

ter

Hab

itat 1

: San

d bo

ttom

. San

d bo

ttom

hab

itat i

s ea

sy to

bur

row

into

and

is o

ften

inte

rtid

alan

d ad

jace

nt to

sea

gras

s be

ds o

r oy

ster

ree

fs.

Hab

itat 2

: Ree

f st

ruct

ures

. Nat

ural

ree

fs a

re th

ree-

dim

ensi

onal

stru

ctur

es m

ade

excl

usiv

ely

of a

ttach

ed b

ival

ves

and

thei

r sh

ells

.

Hab

itat 3

: Tid

al s

alt m

arsh

es. T

idal

mar

sh h

abita

t has

sed

imen

t sui

tabl

e fo

r bu

rrow

ing

and

gras

ses

suita

ble

for

atta

chm

ent o

f m

ollu

scs. 1

0

ff*ituPiko.`).'0)yiueor':,:tee .7te.odifi'dakRrICkpoepure. .f.

OYSTER VS. OYSTER

The Eastern oyster (Crassostrea virginica) is often de-scribed as one of the Chesapeake Bay's "keystone"species. The term "keystone" species refers to an ani-mal that plays a central ecological role within a habi-tat. Prior to the late 1800's, oysters dominated theChesapeake Bay both ecologically and physically.Oysters were so abundant that they could filter most ofthe Bay's water once every three to five DAYS (Newell,1988'). Captain John Smith described these pre-colo-nial oyster reefs in his log books as navigation haz-ards.

Reef oysters are usually exposed to favorable biologi-cal conditions in Chesapeake Bay tributaries. How-ever, not all oysters are found on subtidal reefs. Oysterbars or flat clumps of oyster shell may also be found inmany parts of the Bay. On Virginia's Eastern Shore,especially in the seaside estuaries, oysters commonlyoccur in small groups or clumps.

Although the seaside oysters are the same species asthe reef-building oysters commonly observed in the Baytributaries (both are Crassostrea virginica), there arenoticeable differences in shell shape or morphology.These morphological differences are largely due to dif-ferences in the animals' habitats. Comparison of reefoysters and seaside oysters can reveal the influences ofhabitat conditions including tidal currents, bottom type,and salinity on shell morphology within the same spe-cies.

Objective: Examine representative oyster shells fromthe seaside and from western shore Chesapeake Baytributaries and relate observed differences in shell mor-phology (shape) to habitat conditions.

Skills: Observation, hypothesizing, communication,and group collaboration.

Relevant Virginia SOL:LS.10 Organism adaptation to biotic and abiotic factors in a

biomeLS.11 Dynamic nature of organismsB10.5 Organism response to environment

Materials: Oyster shells from western shore Chesa-peake Bay tributaries (reef oysters) and seaside estuar-ies (seaside oysters).

Procedure:1. Divide students into small groups or "researchteams".2. Give each group at least one reef oyster valve andone seaside oyster valve. At this point, do not identifythe shells as oyster shells.3. Using Worksheet A, on page 11, have the studentsdescribe and compare the two different types of shellvalves in terms of:

general shape qualitative descriptions (round,wing shaped, flat, etc.)

- quantitative measurements of shell height andshell widthgeneral appearance and texture

- specific morphological features including loca-tion of the hinge and adductor muscle scars

4. Ask the students which of the shells are oyster shells.Have each research team present its answer (and rea-sons for the answer) to the class. If the students don'trecognize that both shells are oyster shells, highlightthe basic similarities between the shells. Tell them thatthe observed differences in shell morphology are dueto differences in habitat conditions.5. List various habitat conditions (e.g., temperature,salinity, tidal currents, bottom type [sand vs. mud]) onthe board to help the groups with #6 below.6. Using Worksheet B, on page 12, have the groupsmake predictions as to which habitat conditions are re-sponsible for the observed differences in the shells. Askeach group to put together a habitat description for eachshell type (3 or 4 sentences) and descriptions of poten-tial habitat-specific advantages of each morphologyto present to the class.7. Following the group reports, review the group habi-tat descriptions and advantages as a class and compileclass habitat descriptions and advantages for each shelltype. Compare these descriptions with the descriptionsgiven on pages 9 and 10.

1 Newell, R. 1988. Ecological changes in the Chesapeake Bay: Are they the result of overharvesting the American oyster, Crassostrea virginica? pp.536-546. In: Lynch, M. P. and J. A. Mihursky (eds.). Understanding the Estuary: Advances in Chesapeake Bay Research. Chesapeake ResearchConsortium Publication 129.

i

vapanz

CHESAIPEAKE BAY TRIBUTARY OR REEF OYSTIERSrT

r."

-

SHELL MORPHOLOGY RELATED HABITAT CHARACTERISTICS

A reef oyster's shell is almost half as wide as it is Reef oysters occur in deeper areas below the tidelong and somewhat oval shaped. line, where tidal currents are relatively slow.

Because water velocity or flow around theanimal is relatively low, a slim, streamlinedshell is not necessary. In calm water, theoyster's shell grows more or less equally ineach direction.

Low tidal currents mean reduced movementof sand along the bottom. Because bottomsediments are not usually stirred up into thewater column, reef oysters can grow nearthe bottom with less risk of suspended sedi-ments clogging their gills.

Shell exterior is covered with worm tubes, bar- Lower tidal currents make it easier for many in-nacles, young oysters (oyster spat) and other foul- vertebrates including other oysters to settle ontoing organisms, the hard surfaces of oyster shells. These inverte-

brates are able to establish themselves and beginto grow because the shells are not scoured by wa-ter and sand twice a day during changing tides.

12

Vt4Ouoll6v'z'aysveu. keefreorligkag Egkdeopre

SEASIDE OYSTEIRS

SHELL MORPHOLOGY RELATED HABITAT CHARACTERISTIC

A seaside oyster's shell is long and narrow with a Seaside oysters occur in habitats with high tidalcurrents.

- These oysters are usually attached to smallbits of shell or other hard material in the sandbottom. The oysters grow vertically off thebottom and up into the water column. Thehooked hinge area helps prevent the animalfrom being dislodged by tidal currents.

slightly hooked hinge area.

The long, narrow shell is streamlined, re-ducing the force of water movement over theshell. This helps keep the animal from be-ing dislodged.

- High tidal currents stir up and move sandnear the bottom. Filter feeding, oysters arevulnerable to "clogging" of their filtering sur-faces by excess sand in the water.

The seaside oyster's shell lacks or shows little evi- It is difficult for organisms such as barnacles oys-dence of barnacles, worm tubes, oyster spat, or ter spat, and worms to settle and grow on seasideother fouling organisms. oysters' shells. Swift tidal currents sweep over the

oysters twice a day scouring the shells with a mix-ture of water and sand.

1 3

Sket

ch b

oth

side

s of

each

oys

ter

shel

lbe

low

.

Des

crib

e th

e sh

ape

of e

ach

shel

l.H

eigh

t and

wid

thD

escr

ibe

the

text

ure,

col

or, a

ndot

her

shel

l fea

ture

s.

RE

EF

oyst

er

SEA

SID

E o

yste

r

Lis

t the

maj

or d

iffe

renc

es b

etw

een

the

shel

ls.

1415

16

Com

pare

the

phys

ical

and

che

mic

al c

hara

cter

istic

s of

eac

h oy

ster

hab

itat u

sing

the

tabl

e be

low

. Ran

k th

e ch

arac

ter-

istic

s fr

om 1

(lo

wes

t) to

5 (

high

est)

in te

rms

of th

eir

infl

uenc

e on

oys

ter

shel

l sha

pe in

eac

h ha

bita

t.E

xpla

in y

our

rank

ings

.

Rel

evan

t hab

itat

char

acte

rist

ics

Wes

tern

sho

re C

hesa

peak

eB

ay tr

ibut

ary

(RE

EF

oyst

er h

abita

t)

Seas

ide

tidal

cre

ek(S

EA

SID

E o

yste

r ha

bita

t)

Rel

ativ

e in

flue

nce

on o

yste

r sh

ell

shap

eR

EE

FSE

ASI

DE

Ann

ual w

ater

tem

pera

ture

ran

ge (

°C)

4 to

30°

C4

to 3

0° C

Salin

ity r

ange

(pp

t)7

to 1

8 pp

t20

to 3

5 pp

t

Tid

al c

urre

nts

(spe

ed)

Low

to M

oder

ate

Hig

h

Bot

tom

type

Sand

, mud

, or

oyst

er s

hell

Sand

, mud

, or

oyst

er s

hell

Tid

al r

ange

(ex

posu

redu

e to

tide

s)L

ess

than

2 m

2 m

or

mor

e

17

tz,

OYSTIERS AND REEF& IHIow SHELL SHAPE DERNES ME HA

Eastern oysters (Crassostrea virginica) dominated theecological and physical landscape of the ChesapeakeBay prior to the mid-19th century. The oyster played acentral role in the Bay's food web because of itsabundance and feeding capacity. Crassostrea is a reef-forming oyster species. The large reefs created by theBay's oysters were the foundations of complex shallowwater communities whose members includedHUNDREDS of species.

A living oyster reef is a complex structure in whichmany species can both live and feed. It is thiscomplexity that makes the reef both unique andimportant. An oyster reef is not just a pile of dead shellsbut a veritable condominium for many other species.All the nooks and crannies within the reef are occupiedby species that specialize in occupying these veryspecial nooks and crannies. The spaces between theoyster shells come in all sorts of shapes. Flat spaces areoccupied by flat species such as skilletfish. Tall thinspaces are occupied by thin profile fish such as blennies.More regular-shaped spaces are occupied by gobies,whose bodies are about equal in height and width. Allof these species of fish may eat similar things, but theycoexist in the greater reef structure because individualfish species occupy different types of small spaces. Thuseach species has its own unique microhabitatrequirements within the reef. Successful species areable to make the most of available space and resources.

These small fish species not only live and feed in thereef, they breed there also. Their larval forms eat oysterlarvae, so the interdependence of the reef residents isstrengthened. These fishes are called intermediate reef

Figure 3.1. A look at the surface of an oyster reef. The spacesbetween the shells provide favorable habitat for many small animals.

ETAT

fishes because they are resident on the reefs andintermediate in the reef food chain. These small fishesare eaten by other resident species like mud crabs, andby larger non-resident predators, such as striped bass,bluefish, and others that seasonally move into the riversto feed. The food chain becomes a food web, growingin complexity.

Figure 3.2. An underwater close-up of an oyster reef. Note the spacesbetween the oyster shells and the 3 small fishes that are visible on andbetween the shells.

In essence, the nooks and crannies or spaces betweenand within the oyster shell matrix are defining featuresof the oyster reef habitat. These spaces provide:

increased surface area for settlement by oyster larvaeas well as algae and other invertebrates (such as barnaclesand polychaete worms) that are eaten by larger species.

protected places for oyster larvae to settle and avoidpredation by blue crabs.

nesting sites and sheltered habitat for small fishes andinvertebrates that are prey for larger species.

Since the spaces within the oyster shell matrix are socritical to the function of oyster reef habitat, these nooksand crannies provide a logical starting point for anyexamination of oyster reef communities and the relatedfood web or trophic structure.

18

Hawk llga'z Oyarr Recerrearkkg? IMilpefiapore

SURFACE AREA: WHY REEFS ARE SUCCESSFUL HABITAT

In the context of oyster reefs, surface area describes the actual amount of oyster shell that is exposed to the water column.Reef structures are essentially large piles or mounds of oyster shell. These mounds provide more surface area forsettlement of oysters and other animals than oyster bars, or flat lawns of oyster shell.

Why does a mound have more shell exposed to the water than a lawn?

When oyster shell is lying flat on the river bottom, only When oyster shell is made into a mound or reef structure,one side of each shell is exposed to the water: most of the shells have a portion of BOTH sides of the

shell exposed to the water. Remember that oyster shellsare irregularly shaped and do not fit nicely together likebuilding blocks. An oyster shell pile has lots of spacesbetween the shells - and lots of exposed surface area.

PART I. THE REEF MATRIX: HIGH PROFILE REAL ESTATE

Objective: Examine the relative differences betweenoyster bars (shell lawns) and oyster reefs (shell mounds)in terms of available surface area for settlement by otherspecies.

Skills: Observation, communication, demonstration ofthe surface area concept, and math (averaging).

Relevant Virginia SOL:6.9 Living systemsLS.4 Animal needsBI0.9 Analysis of local ecosystems

Materials: Two or three dozen oyster shell valves perstudent research team.

Procedure:1. Divide class into small groups or "research teams"of two to four students each.2. Provide each group with two or three dozen oystershell valves.3. Have half of the groups use their oyster shells tomake an oyster bar, a flat lawn of oyster shells in asingle layer. When the bar is completed, have the stu-dents count the number of oyster shell sides that areexposed to the air.

4. Instruct the other groups to use their oyster shells tobuild small mounds or reef structures. Remind thestudents that it is acceptable to have spaces betweenthe shells. Have the students count the number of exte-rior and interior oyster shell sides (total or partial) thatare exposed to the air.5. Average the number of exposed shell sides in theoyster bars and the number of exposed shell sides inthe oyster reefs. Compare the difference. Discuss thebiological consequences of these differences keepingin mind that:

1. Oyster spat (larvae) prefer to settle on exposed oystershell. Increased availability of hard surfaces maytranslate into increased oyster recruitment and con-tinued reef growth.

2. Polychaete worms, bryozoans, and many local algalspecies settle preferentially onto exposed hard sub-strate like oyster shells. All of these organisms areeaten by other members of the reef community; thusmore surface area means more food for upper levelconsumers.

3. Mussels and other filter feeders (barnacles) settle onexposed surfaces. Increased numbers of filter feed-ers (including oysters) translates into increased con-sumption of phytoplankton. This reduces chances ofseasonal algal blooms that can cause unfavorablewater quality conditions. Increased filtration activityalso provides more nutrients (by-products of filter-ing activity) for benthic grazers.

Lll

1 9

VCDRT

PART II. REEF RESIDENTS: MATCHING BODY SHAPES

WITH HOUSES

Objective: Demonstrate the importance of spaceswithin the reef matrix as habitat for small reef fishes.

Skills: Observation, communication, and math (graph-ing).

Relevant Virginia SOL:6.9 Living systemsLS.4 Animal needsLS.7 Organism dependence on living/non-living components

of the environmentLS.8 Competition, behavior within a populationLS.9 Population interactions within a communityBI0.5 Organisms response to environmentBI0.9 Dynamic equilibria within communities, analysis of

local ecosystems

Materials: Oyster shell valves (2-3 dozen per group),small (< 1 inch long) white foam packing peanuts (2dozen per group), larger (1-2 inch long) foam packingpeanuts (2 dozen per group), colored markers.

Procedure:1. Divide students into small groups or "research

teams".2. Provide each group with two or three dozen oyster

shells, foam peanuts, and a marker.3. Instruct each group to make an oyster reef with all

of their shells.

StripedBlenny

Side View

Height

Height > Width>

Width

Profile View

4.

5.

6.

7.

8.

Have students use colored markers to label thesmaller foam peanuts as naked gobies (G) and thelarger peanuts as striped blennies (B).When the reefs are completed, have students placeas many naked gobies and striped blennies as pos-sible in their reef without disturbing the reef ma-trix. Only one "fish" should be placed in each space.Have each group report the total number of gobiesand blennies that "live" in their reef. Display classresults as a chart. Discuss how the differences inthe shapes of the reef's nooks and crannies mightbe related to the differences in the shapes and sizesof the fish profiles as well as fish behavior (see Fig-ures 3.3 and 3.4 below).The table on page 16 shows typical numbers of go-bies and blennies that might be found living in aChesapeake Bay oyster reef. Using the data fromTable 3.1, have students graph fish abundance in re-lation to bottom type (see worksheet on page 19).Use the resulting graphs to discuss the relationshipbetween habitat availability and the abundance ofnaked gobies and striped blennies. After the stu-dents understand that increased habitat availability(reef nooks and crannies) translates into increasedabundance of gobies and blennies, use the OysterReef Trophic Diagram (Figure 3.6) to apply thisconcept to the overall reef community. Residentfishes are fish species that live in the reef matrix.Semi-resident fishes spend a majority of their timeon the reef but may move off-reef occasionally.

Height /Height - Width Profile View

Width

Figure 3.3. Picture and profiles of an adult striped blenny. Striped blennies Figure 3.4. Picture and profiles of an adult naked goby. Naked gobies areare larger and more aggressive than naked gobies. Blennies use larger reef small docile fish. They use smaller oyster reef spaces as hiding places, feed-spaces for hiding places, feeding grounds, and nesting sites. ing grounds, and nesting sites.

ll

Huglloolla'z gys5mo° eeffrachllovg Paprookore

CARTESIAN COORDINATE GRAPHING: A REVIEW

Graphing data using the Cartesian Coordinategraphing system requires that the data be arrangedin (X, Y) pairs; that is for every value of the inde-pendent variable there is a corresponding valuefor the dependent variable. Keep in mind thatzeroes are valid data points. Each point on thegraph represents the location coordinates givenby an (X, Y) data pair. In the goby/blenny dataset, bottom type is the independent variable andfish abundance is the dependent variable.

X - axisIndependent Variable

.Site

Bottom Type(% oyster shell)

No. ofnakedgobies

No. ofstriped

blennies

1 0 1 0

2 25 1 1

3 100 10 8

4 75 9 7

5 50 4 2

6 100 12 14

7 0 0 1

8 100 16 10

9 50 5 8

10 25 4 1

11 100 21 7

12 100 8 19

Table 3.1. Data from a diver survey of 12 sites on and imme-diately adjacent to an oyster reef. The type of bottom or sub-strate is described in terms of the percentage of oyster shellwithin a one meter square area. The number of adult nakedgobies and striped blennies observed within the same one metersquare area is also reported.

Transient fishes move onto the reef to feed but spendmost of their time elsewhere. Keep in mind that:

1. Increased abundance of gobies and blennies pro-vides more food for benthic predators such as bluecrabs. Increased blue crab abundance providesmore food for larger fishes that eat blue crabs in-cluding striped bass.

2. Gobies and blennies "graze" or feed on algae andsmall invertebrates such as barnacles and polycha-ete worms that are found on the reef's surface. Anincreased abundance of gobies and blennies mayresult in the removal of more algae and other inver-tebrates. High levels of grazing may help to keepat least part of the reef surface available for contin-ued settlement of spat and other invertebratesthroughout the season.

3. Increased abundance of naked gobies and stripedblennies provides more food for larger fishes likestriped bass, bluefish and weakfish.

4. Increased amounts of food for larger fishes maypositively affect fish abundance and individual fishgrowth, survival, and reproduction.

The relationship between increased shell surface areaand the reef community food web is pretty amazing,isn't it?

Figure 3.5. Representative oyster reef predators (consumers): bluefish(upper left), striped bass (lower left), and a blue crab (right).

21

Figure 3.6. A simple food web for Chesapeake Bay oyster reefs indicating the main trophic levels. Thespecies that are listed for each trophic level are common representatives. In some cases, theremay be at least 20 other species within a particular level. This figure is modified from:O'Beirn, F, Luckenbach, M, Mann, R, Harding, J, and Nestlerode, J. 1999. Ecological functionsof constructed oyster reefs along an environmental gradient in Chesapeake Bay. VirginiaInstitute of Marine Science, Gloucester Point, VA. Annual report submitted to U.S. E.P.A.Chesapeake Bay Program, Annapolis, MD.

OPEN WATERHABITATS

HIGH TIDE LEVEL

LOW TIDE LEVEL 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

OYSTER REEFHABITATS

OC

`4" I,, , >j:%l-r7--2.t;-''Cl,:'v'Q's%'_3

,-, 3-c: _!''1,''' V \ * / ':;- i1:.; rli;:i E:cEis 7: dr?:::-..:.:;-.Cc,

_,- , :,-, : ,-,)

vour1-1-K -,-,..yelr i-71.)&-11,-v.-4,,!: ---7G)&10 ')-,...1.,--";:k.,--ee,-.-..1,,fs\I-(1_::-V-C1<*isi-.)..C.,-.Z:eir;

I ATTACHED ALGAE I --------..

°coo 000 00000000000

PHYTOPLAIUT-01

POO

RESIDENT REEF INVERTEBRATES(FILTER FEEDERZ /112AZERS/PREDATOZ\

MusselsOysters

Polychaetesj

AmphipodsGastropods

,._Mud Crabs./

TRANSIENT REEF FISHES

Atlantic MenhadenBluefish

CobiaCownose RayStriped Bass

Summer FlounderWeakfish

RESIDENT REEF FISHESClingfish

Naked GobyOyster ToadfishStriped Blenny

SEMI-RESIDENT REEF SPECIES

Atlantic CroakerBlue Crab

Silver PerchSpot

117

22

Notdokes) Oyaeo, Rea: readdog peoleurr

Related vocabulary:benthic: referring to organisms that live in or on the

bottom.

matrix: the complex three-dimensional structureformed by the oyster shells in an oyster reef.

recruitment: successful settlement of an oyster lar-vae from the plankton to a hard surface such as anoyster shell.

settlement: the process by which larval oysterschange from a free-swimming planktonic bodyform to a permanently attached benthic body form.

spat: young oysters that have recently settled fromthe plankton onto a hard surface.

trophic level: one link in a food chain or food web;part of the trophic "pyramid" that represents theenergy flow through the living components of theecosystem.

Suggested discussion questions:

PART I. THE REEF MATRIX: HIGH PROFILE REAL ESTATE

1. When oysters reproduce, the males and females re-lease eggs and sperm into the water at the same time.Fertilization and development of the embryo takeplace in the water column. How could the physicalstructure of an oyster reef improve the reproduc-tive success of oysters in the Chesapeake Bay?

2. Severe storms and floods can send large volumes ofsediment flowing down rivers into the ChesapeakeBay. How would this sediment affect oysters?Which type of oyster structure might suffer the mostnegative impact from this sediment, an oyster baror an oyster reef? Why?

3. Why might it be important or beneficial for a filterfeeding organism, like the oyster, to live up off thebottom in or on a three dimensional structure likean oyster reef? How might these benefits relate tothe long term success or failure of an oyster reefcommunity?

PART II. REEF RESIDENTS: MATCHING BODY SHAPES

WITH HOUSES

1. Given that oyster reefs attract juvenile striped bass,bluefish, weakfish, and blue crabs, why might it beimportant for small reef fishes to be able to hide inthe reef structure?

2. Which type of oyster structure do you think couldsupport more blennies and gobies, an oyster bar oran oyster reef? Give at least two reasons for youranswer.

3. If a striped blenny attempts to move into an oystershell where a naked goby has established a nest, whatdo you think will happen? How could a goby avoidthis situation?

g3

REEF RESIDENTS WORKSHEET

Fish abundance in relation to bottom type on and near oyster reefs

.Site

Bottom Type(% oyster shell)

No. ofnakedgobies

No. ofstriped

blennies

1 0 1 0

2 25 1 1

3 100 10 8

4 75 9 7

5 50 4 2

6 100 12 14

7 0 0 1

8 100 16 10

9 50 5 8

10 25 4 1

11 100 21 7

12 100 8 19

Table 3.1. Data from a diver survey of 12 sites on and imme-diately adjacent to an oyster reef.

ll

Fish Abundance(Number of fish per meter -2)

Y variable

Bottom Type(% oyster shell)

X variable

No. ofNakedGobies

No. ofStriped

Blennies

0

25

50

75

100

24

NuNko lac)z Ppm. Reertreedgovs Et:mew-re_

VORTEXVirginia's Oyster Reef Teaching EXperience

. An Educational Program for Virginia Science Educators

What is VORTEX?

Virginia's Oyster Reef Teaching EXperience (VORTEX) is a multi-component program focusing onthe importance of oyster reef communities in the Chesapeake Bay ecosystem. VORTEX is designedspecifically for science educators by the Virginia Insitute of Marine Science. The program includes aseries of workshops and multimedia materials (i.e., a CD ROM and Internet web sites). All programcomponents are designed to provide a basic biological and ecological background to enable partici-pants to integrate program materials into hands-on science lessons that support selected VirginiaStandards of Learning in Science.

Program partners and co-sponsors include:Virginia Institute of Marine Science Department of Fisheries Science

Virginia Sea Grant Marine Advisory ProgramVirginia Environmental Endowment

Chesapeake Bay Restoration Fund Advisory Committee

For more information, visit the VORTEX web site at: www.vims.edu/fish/oyreef/vortex.html or contactJuliana Harding (jharding@vims.edu), Vicki Clark (vclark@vims.edu), or Roger Mann(rmann@vims.edu).

WIILLHAM&MARY

'VIRGINIA INEITI UTE OF MARINE SCIENCE

SCHOOL OF MARINE SCIENCE

Virginia VORUEZ20

25

VIRGINIAChesapeake Bay Restoration,Fund Advisory Committee

A ir4R/01/741//FRIEND OP THE CHESAPEAKE

VirginiaEnvironmentalEndowment

06/06/2002 14:08 FAX 804 684 7045 VIMS [2)002

U.S. Department of EducationOffice of Educational Research and Improvement (OERI)

National Library of Education (NLE)Educational Resources Information Center (ERIC)

REPRODUCTION RELEASE(Specific Document)

I. DOCUMENT IDENTIFICATION:

SOt_kfp(ERIC

Title: Shell Games

Author(s): Juliana M. Harding, Roger Mann, and Vicki P. Clark

Corporate Source:Virginia Institute of Marine Science VORTEX Program

Publication Date: 1999

II. REPRODUCTION RELEASE:

In order to disseminate as widely as possible timely and significant materials of interest to the educational community, documents announced In themonthly abstract journal of the ERIC system, Resources in Education (RIE), are usually made available to users In microfiche, reproduced paper copy, andeledronic media, and sold through the ERIC Document Reproduction Service (EDRS). Credit is given tO the source of each document, and, if reproductionrelease is granted, one of the following notices is affixed to the document.

If permission is granted to reproduce and disseminate the identified document, please CHECK ONE of the following three options and sign at the bottomof the page.

The aempie Blinker 'shown below wHl beaflixed la all Level I rinemmerds

1

PERMISSION TO REPRODUCE ANDDISSEMINATE THIS MATERIAL HAS

BEEN GRANTED BY

TO THE EDUCATIONAL RESOURCESINFORMATION CENTER (ERIC)

Level 1

ck here ror Level 1 tMee, eemilmng reproeuctiondissemination in microfiche or other ERIC archival

media (e.g., electronic) end Pepsi coPy.

Sigifhere,please

The sample sticker shown holow win bearmed to all Level 2A documents

PERMISSION TO REPRODUCE ANDDISSEMINATE THis MATERIAL IN

MICROFICHE, AND IN ELECTRONIC MEDIAFOR ERIC COLLECTION SUBSCRIBERS ONLY,

HAS BEEN GRANTED BY

2A

TO THE EDUCATIONAL RESOURCESINFORMATION CENTER (ERIC)

Level 2A

X

Check here for Level 2A release. pesmitting reproductionand dissemination In microfiche anti In elearunie media for

EPIC archival xadlaction sun:Kamm only

Documents will be processed as indicated provided reproduction quality permits.If permirAlon to reproduce la granted, but no box is checked, documents will be processed at Levei 1.

Tho sample sticker Shown below wIll boaffixed tll an LeveJ 28 documents

PERMISSION TO REPRODUCE ANDDISSEMINATE THIS MATERIAL IN

MICROFICHE ONLY HAS BEEN GRANTED BY

2B

TO THE EDUCATIONAL RESOURCESINFORMATION CENTER (ERIC)

Level 2B

X

Cher* here for Level 28 release, permitting reproductionand dissemination In micronthe only

I hereby grant tolhe Education& Resources Information Center (ERIC) nonexclusive permission to reproduce and disseminate this documentas indicated above. Reproduction from the ERIC microfiche or elecIrOnic media by persons other than ERIC employees and its systemcontractors requires permission from the copyright hoiden Exception is made for non-profit reproduction by libraries and other service agenciesto satisfy kdorrnation needs of educators In response to discrete inquiries.

sigroeire- meted Name/PecitionflItle:

Juliana M. Harding/Senior Marine Scientist

Montan &Wiese:

Virginia Institute of Marine Sci nceP.O. Box 1346, Gloucester Point, Virginia 23062

Teiephanc;

804) 684-7302FAX:

(604) 684-7045&Mall Addmss:

jharding@vims.eduDate: I

(I, (o/D2---

06/06/2002 14:09 FAX 804 684 7045 VMS 2 003

III. DOCUMENT AVAILABILITY INFORMATION (FROM NON-ERIC SOURCE):

If permission to reproduce is not granted to ERIC, or, If you wish ERIC to cite the availability of the documentfrom another source, pleaseprovide the following information regarding the availability of the document. (ERIC will not announce a document unless it is publiclyavailable, and a dependable source can be specified. Contributors should also be aware that ERICselection criteria are significantly moresbingent for documents that cannot be made available through EDRS.)

Publisher/Distributor:Virginia Sea Grant Marine Advisory Program

Address:Virginia Institute of Marine ScienceP.O. Box 1346Gloucester Point, Virginia 23062

Price:$1.00 each

IV.REFERRAL OF ERIC TO COPYRIGHT/REPRODUCTION RIGHTS HOLDER:

If the right to grant thls reproduction release is held by someone other than the addressee, please provide the appropriate name andaddress:

Name:

Address:

V.WHERE TO SEND THIS FORM:

Send this form to the following ERIC Clearinghouse:

ERIC/CSMEE1929 Kenny RoadColumbus, OH 43210-1080

E-mail: bcekrum.1 @osu.eduFAX: 614-292-0263