TROPICAL MARINE ORGANISMS AND COMMUNITIES W. B. GLADFELTER [Converted to electronic format by Damon J. Gomez (NOAA/RSMAS) in 2003. Copy available at the NOAA Miami Regional Library. Minor editorial changes were made.] LIST OF FIGURES Front Cover : Acropora palmata Reef East End Field Sites Buck Island Reef Profile Salt River Map Commas Marine Algae Representative Sponge Spicules Canmn Reef Demsponges Lebrunea coralligens Representative Coral Skeletal Forms Sea Cucumber Dissection Conch Dissection Representative West Indian Gastropods West Indian Bivalves Representative Zooplankton Back Cover : Queen Conch TABLE OF CagrENTS I Annotated Checklist of Marine Organisms 1 Plants 2 Sponges 4 Chidarians 7 Echinoderms 12 Chordates 15 Molluscs 18 Annelids 21 Crustaceans 23 II Marine Field Trip Sites, St . Croix, V .I . 27 Map, east erxi field sites 27 Synopsis of field sites 28 Buck Island Reef 32 W.I .L. and Smuggler's Cove 36 Tague Bay patch reefs 40 Lamb Bay 42 Holt's Reef 44 East End Bay 46 Tague Bay backreef : day vs night 49 Horseshoe patch 52 Mangroves 54 Cane Bay Reef 57 Frederiksted Pier 60 III Tropical Marine Organisms : Field and Lab Exercises 63 ID of common marine plants 63 Sponges .67 Field ID of sponges 70 Cnidarians 76 Field ID of anthozoans 84 Echinoderms 88 Molluscs 94 Annelids 102 Crustaceans 104 Tropical zooplankton 106 Field observation of reef fishes 112 IV Analysis of Tropical Marine Camu.inities 114 Echinometra populations in different habitats 115 Recovery of A palmata reef 118 Microhabitat specialization : Associations 120 Coral reef community structure 123 Grassbed community structure 127 Fish community structure on small artificial reefs 130 Primary production on reefs 135 Effects of herbivory on algal community 139 Twilight changeover in reef fish community 142 Niche breadth and overlap in a guild of reef organisms 144 BIBLIOGRAPHY 147 ANNOTATED C"tU KLIST OF MARINE ORGANISMS OF ST CROIX, VIRGIN ISLANDS The following is a master list of the common, conspicuous or otherwise important or interesting shallow-water marine invertebrates of the West Indies in general and St . Croix in particular . The organisms are presented in taxonomic outline so that their relationships can be readily seen . Sane of the higher taxa have been superseded in the technical literature but have been used herein because of their greater usefulness to the ru-ispecialist . Some higher taxa without known local representation have been omitted . The ranks of higher taxa have been abbreviated as follows : € = kingdom ; Ph = Phylum ; Cl = Class ; 0 = order ; F = family . There is no well established set of vernacular names for most marine invertebrates and plants (in contrast to vertebrates) . Therefore the scientific, latinized form is used below . The scientific name of an organism consists of two words : the genus (plural = genera) and the species . Both are underlined or italicized. In the account below, for simplicity, the generic name is often used alone except when there is more than one species dealt with in the same genus . € Monera : prokaryotes, with no nuclear or other internal cell membranes Ph Cyanophyta (=Cyanobacteria ; blue-green algae) Microooleus : "slimy" filamentous masses on intertidal rocks Trichodesmium : planktonic ; tufts of fine brown filaments Oscillatoria : rings and halos on dying coral heads ("black band disease") Ph Eubacteria (bacteria) Ph Prochlorophyta : prokaryotes with pigments similar to those of higher plants Prochloron : tiny single green cells in atrial spaces of certain didemnid ascidians € Protista : unicellular or cell colonies without somatic differentiation ; mostly microscopic ; protozoan, etc . Ph Chrysophyta (diatoms) : planktonic and benthic ; unicellular "plants" with sculptured Si02 test Ph Pyrrhophyta (dinoflagellates) Ceratium : 3-horned armored form (i .e . with cellulose plates) Gymnodinium : naked form occurring in reef cnidarians as zooxanthellae Gambierdiscus : large benthic form implicated in ciguatera (tropical fish poisoning) Ph Sa codina (amoebas, etc . ) Cl Foraminifera (forams) : large multinucleate amoebas with perforated Ca0D3 shell often visible to unaided eye J-bnotremma : encrusts in dark cavities or under rocks ; important oanponent in algal ridges, stratified with crustose red algae forms maroon sand grains when eroded Sorites : flat spiralled shell to about 1 mm long in lagoonal sand ; other forms up to 5 mm, may be canon Globigerina : planktonic, taken offshore ; with several u equal spherical chambers 1 A variety of other crustose and free-living forms occur in a number of environments Cl Radiolaria (radiolarians) : planktonic forms with radial Si02 skeletal rays Ph Ciliophora (ciliates and suctorians) : nearly ubiquitous on various substrata ; includes stalked and unstalked forms ; a good source is necrotic marine organisms such as dying hydroids or on "white band disease"-affected A palmata K Plan tae (true plants) : multicellular (usually), with photosynthetic pigments in plastids ; generally attached to substrata; many important plants in tropical waters deposit Ca003 skeletons or inclusions, which then became important components of benthic sediments Ph Rhodophyta (red algae) : reddish, brownish or greenish ; filamentous, branched or crustose ; phycobilins as accessory photosynthetic pigments ; nonmotile gametes € Nemalionales Liagpra : flaccid pinkish-white clumps Galaxaura : clumps of stiff pinkish orange tubular branches Asparagopsis : seasonal on high energy reefs ; like soft little fir trees with reddish midrib € (mot idiales Gelidiella : on intertidal beachrock ; stiff midrib with bipinnate branching € Cryptonemiales Peyssonelia : forming colorful orange or purple crusts in shaded areas (the following genera are corallines, belonging to the family Corallinaceae ; all deposit Ca0)3) Amphiroa : with stiff delicate dichotomous branches Corallina, : on shallow carbonate pavements ; flattened and segmented Jania : very delicate paintbrush-like form Melobesia : small crusty patches on turtle grass blades Lithophyllum : and other crustose eorallines : often forming thickened crusts on dead coral and reef surfaces ; major reef- builders € Gigarbinales Hypnea : hooked branch tips Gracilaria : robust branches, on deeper flats € Rhodymeniales Coelothrix : with iridescent blue tips € Ceramiales Centroceras : with nearly microscopic cross-banding Ceramium : similar but without cross-banding Martensia : delicate lacy pink form, seasonally canton Dasya : very fine filamentous tufts Acanthophora : firm brownish stems with stubby forked lateral branches Bryothamnicn : on wave-swept pavements Laurencia : a number of species, mostly firm and bushy Ph Pheophyta (brown algae) : tan or brown in color due to accessory pigments ; includes many robust forms ; Cao03 deposition not 2 prevalent € Ectocarpales Ralfsia : small dark brown patches on rocks € Dictyotales Dictyota : flat, brown and dichotomously branched Dilophus : similar but with tapering tips Dictyopteris : similar, but with midribs Padina : curled broad blades with conspicuous concentric bands, cannon intertidally Stypopodium: also with concentric bands, blades more linear Lobophora : similar to Padina but without bands € Dictyosiphonales Colpomenia : hollow tan lumps € F ucales Sargassum: quite large and robust, with crinkly blades off tough central stem ; with tiny spherical floats when reproductive Ph Chlorophyta (green algae) : bright to dark green in color ; with chlorophyll b; includes a number of important calcareous forms ; includes a number of coenocytic forms (i .e. with incomplete cell boundaries) € Ulotrichales Entero mrpha : thin and tubular Ulva : delicate flat green blades € Cladophorales Chaetanorpha : long green stringy masses Cladophora : moss-like clumps € Siphoriocladales Batophora : small whorls Neomeris : tiny green or white thin clubs Acetabularia : distinctive small parasols E nodesmis : articulated green branches Valonia : turgid, thin-walled shiny-surfaced spheres Dictyosphaeria : granular crinkly hollow green lumps € Siphonales Bryopsis : very delicate dark green feathers Caulerpa : with extensive tubular stolons ; diversity of thallus forms C raoanosa : pea-like thalli C microphysa : similar but more tapering at base C prolifera : thalli blade-like and smooth C_ cupressoides : linear serrated thalli C sertularioides : feather-like C mexicana : similar but lateral branches wider and overlapping Codium: very dark green felt-like lumpy masses or erect branches Avrainvillea : upright dark green felt-like fans Udotea : similar but paler and stiffer U cyathiformis : goblet-shaped Penicillus : like green shaving brushes anchored in sediment Halimeda : with heavily calcified flat or cylindrical segments ; important contributor to "coral" sand Ph Tracheophyta (vascular plants) Cl Angiospermae Seagrasses : grass-like marine plants in several families other than true grasses ; blades arise from extenmsive root sysbans 3 Thalassia (turtle grass) : blades flat and wide (ca . 1 an) Syringodium (manatee grass) : blades round in x-sec (ca . 1 mm) Halodule (shoal grass) : narrow flattened blades less than 1 mm Halophila : delicate oval blades to a few an long ; generally in shaded areas or deeper water Rupia : in shallow brackish or tenporary .lagoons or salt ponds Mangroves : trees of salty soil that grow along the edges of quiet lagoons, usually zoned landward in the following order : Rhizophora (red mangrove) : grow in seawater to a depth of more than 1 m ; with extensive proproots Laquncularia