Download - Submarine Caves and Cave Biology of Bermuda

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copepods, ostracods, isopods, amphipods,mysids, and cumaceans, as well astanaidaceans, echinoderms, tunicates andfish. While many of these animals, such assponges, echinoderms, tunicates and fish, arenormal inhabitants of the near-shore zane,others are known only from the caves andare restricted to this habitat. It was soonapparent that most cave-adapted (i.e., eyeand pigment-reduced) animals inhabited thedeep, marine waters in the interior of cavesand were thus only accessible by cave divers.

Therefore, specialized training in cavediving would be required to investigate andcatalog the fauna of Bermuda's caves. InSeptember 1979, I invited Paul Meng, aFlorida-based cave diving instructor with theNSS Cave Diving Section, and his friendBarry Warner to come to Bermuda and teacha course for several friends, Paul Hobbs, RobPower, and me. Once properly trained andequipped, we organized ourselves as theBermuda Cave Diving Association andbegan to systematically explore, map, andscientifically document the island's anchialinecaves.

Bermuda is a volcanic seamount located1000 km off the east coast of the UnitedStates in that part of the Western Atlanticknown as the Sargasso Sea. The island wascreated by a series of mid-ocean volcaniceruptions that began about 60 million yearsago, at a time when the Atlantic Ocean wasmuch narrower. Subsequent plate tectonics

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Green BayCave

prior, a biologist had attempted to collectfrom several cave pools but found nothingof interest and concluded that the caves werelifeless habitats. Indeed at that time, Virtuallyall investigations of aquatic cave life wereconducted on freshwater habitats and someof the world's most prominent cave biologistshad stated that, with few exceptions, marinecaves were not important to the field ofbiospeleology.

Not to be deterred, I contacted Dr. BorisSket of the University of Ljubljana inSlovenia, who was studying caves along the

Adriatic coast, andinvited him to come toBermuda. Dr. Sketaccepted and spent twoweeks working with mein September 1978. Wemade dives in several ofthe more open cavepools and found thatsalinity increased withdepth so that at 10 to 20foot depths, the salinityapproached that of theopen sea. It was in thesedeeper, fully marinewaters that wediscovered a wealth ofmarine life includingsponges, gastropods,various worms, andcrustaceans, including

Fig. 1: Map ofBermuda showing the location ofprinciple caves: Green Bay, Admiral's,Walsingham, Palm, Government Quarry, and Tucker's Town Caves.

Submarine Caves and Cave Biology of Bermudatext and ph(Jt(J9raphs blJ Th(Jmas M. Ifi((e

Department of Marine Biology, Texas A & M University at Galveston, Galveston, TX 77553-1675My scientific interest in caves began quite

by accident. After finishing my PhD in June1977, my first job was as a research scientistat the Bermuda Biological Station, where Iconducted studies of tar being washed upon the island's beaches. Up to that time, myinterest in caves was from a purelyrecreational viewpoint. I had done some cavediving while obtaining my Masters degree inOceanography at Florida State and laterwhen teaching at the Florida Institute ofTechnology, When I moved to Texas to workon my PhD, I found diving opportunities tobe quite limited and so I contacted Houstoncavers who invited me along on their trips tocaves in central Texas and northern Mexico.

Upon arriving in Bermuda to start my newjob, I was excited to learn about thenumerous and well-decorated limestonecaves the island had to offer. Since Bermudais a rather small, narrow island, most of itsapproximately 150 known caves are withina few hundred meters of the coast (Figure 1)and many contain sea level pools in theirinterior. Such pools. both at entrances andin the interior of otherwise dry caves, lackabove ground connection with the sea andcontain tidally fluctuating brackish or saltwater. They are properly referred to as"anchialine." Bermuda's anchialine cavepools contain exceptionally clear, dark blue,and often quite deep waters. Although largesubmerged stalactites and stalagmites can beseen from the surface, there are typically noobvious signs of cave-adapted aquaticanimals from above.

Curious about the apparent lack of life inthe cave pools, I asked Dr. Wolfgang Sterrer,the director of the Biological Station, ifanyone had ever looked for animals in thesaltwater caves. He told me that several years

NSS NEWS, August 2003 217

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Passage opens into a large silt flooredchamber-the Desert-before passing undera low arch into the Trunk Passage. This isthe largest passage in the cave, averaging 15m wide and 10 m high. The far end of theTrunk passage terminates in a breakdownstope to the surface and a murky inlandsinkhole-Cliff Pool -the second and onlyother entrance to the Green Bay System. Onthe east side of the Trunk Passage, theHarrington Sound Passages comprise twointerconnecting passageways with muchclearer water than adjacent sections of thecave. The Bath Tub Ring Room at 15 mdepth near the end of the Harrington SoundPassage contains a horizontal bleached bandof bedrock about 50 em in width cuttingacross the rock strata (Figure 2). In the samearea are bones of a sea turtle that apparentlybecame lost and died in the cave at sometime in the distant past.

The North Shore Passage is the longestsingle passage in the cave. It begins on thewest side of the Trunk Passage and extendsfor nearly 500 m to a point past the northernshoreline of the island, where the passagebecomes too low for divers to follow. Severalextended interconnecting loops characterizethis part of the cave. Undercut walls and thelevel nature of this part of the cave at 18 mdepth indicate an underground stream musthave flowed through these tunnels duringglacial low stands of sea level. Massivestalactites and stalagmites, present in virtuallyall parts of the underwater cave, are anotherindication of the cave's long history as a drycave.

Biological zonation is evident as the diverprogresses farther into the cave from theGreen Bay entrance. Brightly coloredsponges, hydroids, tunicates, and otherencrusting organisms literally cover the wallsand ceiling in areas close to the entrance. Asa consequence of decreasing tidal currentsand particulate matter suspended in thewater, the density of these organisms declineswith distance into the cave. In the muchclearer waters of the deep cave interior,troglobitic species predominate.

Other larg~ anchialine caves are locatedon the opposite side of Harrington Soundfrom Green Bay Cave. Two major cavesystems in this area, called the WalsinghamTract, are the Walsingham and Palm CaveSystems. The Walsingham System is about1.3 km long and comprises seven separateentrances: Deep Blue, Vine, Old Horse,Walsingham, Fern Sink, Crystal andWonderland Caves. Of these, Walsinghamwas a former commercial cave, whileadjacent Crystal and Wonderland (nowrenamed Fantasy) are major touristattractions in Bermuda.

Deep Blue Cave consists of an isolatedpool in the Bermuda jungle at the base of a10 m high limestone cliff face. The pool isparticularly impressive due to its crystal clear

stalactites and stalagmites, confirming thatthe caves must have been dry and air-filledfor much of their history.

Green Bay Cave is presently the longestcave in Bermuda, with more than 2 km ofsurveyed passage. The main entrance is awide, submerged passageway extendinginland from the end of Green Bay onHarrington Sound. From shallow depths atthe Green Bay entrance, the cave slopesprogressively deeper to the Rat Trap, a lowbut wide section at 17 m depth. At this point,a low side passage turns south to theConnection Passage and the major part ofthe cave, while the Rat Trap continues andopens out into the Green Bay Passage. Thispassage climbs over breakdown at theLetterbox and passes through a tightrestriction between collapse blocks only toenlarge again. This further extension of theGreen Bay Passage bends back towardHarrington Sound and extends to a small airbell in ceiling breakdown. An underwaterbreakdown slope on the left side of the airbell descends to a spacious, deeper chamberwith a massive boulder choke at one end anda room with distinctly lower visibility-theFog Room at the other.

From the Rat Trap, the Connection

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Marine biologist Tom IIiffe with plankton net bY'S!alagmltl!Blue Cave. Submerged speleotlilflns originally 7/ftmed

ng tbe Ice Ages when sea level wastpwer and the c,vese dry. . I J!

-----~and sea floor spreading have maintainedBermuda's location relative to NorthAmerica, while ever increasing its distancefrom Europe and Africa as the Atlantic Oceanenlarged. Thus, Bermuda has never beenpart of, or closer to, a continental landmass.

As the top of the volcanic seamount waseroded down below sea level, corals beganto grow around the margins, thus producingthe only atoll in the North Atlantic. Coral reefderived limestone, first deposited as coastalsand dunes, caps most of present-dayBermuda. Approximately one million yearsago, limestone caves began forming duringglacial periods, when sea level was 100 rn ormore tower. Later, as glaciers on thecontinents melted and post-glacial sea levelsrose, encroaching seawater drowned largeportions of the caves. Continuing collapse ofoverlying rock into the large, solutionallyformed voids created the irregular chambersand fissure entrances that are commonly seenin Bermuda's caves. Extensive networks ofsubmerged passageways, developedprimarily at depths between 17 and 20 mbelow present sea level, interconnectotherwise isolated cave pools. Thesepassages, only accessible to divers, are welldecorated at all depths with impressive

218 NSS NEWS, August 2003

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COMPASS and TAPE SURVEY BY:

Robin Barber, Rebecca Belcher, Darcy Gibbons,Tom lliffe, Bob Richards, Sandy Stephens andBernie Szuka/ski.

SURVEYED DATES: January 7-8, 2002

CARTOGRAPHY BY: Bob Richards

TOTAL SURVEYED TRAVERSE: 745 metersTOTAL VERTICAL EXTENT: 28 meters

PROFILE VIEW

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@2003, BeCK1S Project

water of an incredible azure color. The rockybottom is covered by the green algaeCaulerpa contrasted with patches of brilliantfoliose red algae and pale brown plates ofthe reef-building coral Agaricia. Underwater,the cave becomes even more spectacular asa diver descends and enters a vastsubmerged chamber. Looking over hisshoulder, the diver beholds a breathtakingpanorama of the broad fissure he has justentered through, silhouetted by sparklingsunbeams piercing the blue water against abackdrop of lush green algae. Thismagnificent chamber continues to a riftextending to the surface and emerging in themore sheltered and secluded glamour of theVine Cave Pool. Dazzling red crustosecoralline algae covers the rocks on the bottomof this overhung and dimly illuminated pool.

At the northern end of the Deep Blue pool,a tight squeeze between breakdown blocksin shallow water connects to a narrow riftthat was passable only after being dug outby divers. From that point, a cathedral-likeunderwater chamber (Figure 3) ascends to atiny air bell, before dropping to a low tunnelat 22 m depth-the deepest point in the cave.The passage then climbs to the top of a riftand separates into a loop that rejoins in ahigh-ceiling, circular air room. A short swimat 6 m depth then brings the diver out intothe main entrance pool ofWalsingham Cave.

The connection to Fern Sink and theremainder of the Walsingham System isthrough a low fissure at 20 m depth off theloop past the circular air bell. On the far sideof the fissure, which is negotiable only withside-mounted tanks, the cave divides. Onepassage ascends a steep breakdown slopeto the Fern Sink rift pool, while anotherpasses under a low deep arch to reach amajor tunnel connecting two spacious air bellchambers, accessible only by diving. Thisarea is magnificently decorated withspeleothems ranging from massive columnsto fragile soda straws and helictites. From thelargest of the two air bells, a narrow lowpassage connects to the main pool in the

commercially shownsection of Crystal Cavewhile another passageextends to the secondpool of WonderlandCave.

Striking contrastsdistinguish the DeepBlue-Walsingham andFern Sink-CrystalWonderland segments ofthe System. In theformer, noticeable tidalcurrents are present,especially in therestriction at Deep Blue

Fig. 4: Heavily vandalized speleothems in a newly discovered and the pool atcave in Bermuda. W a lsi n g ham

Additionally, the wallsand speleothems in this section are staineddark brown to black. In the latter parts of thecave, no currents are evident, the visibility isessentially unlimited, and rock surfaces showno evidence of staining or submergence.Even the frailest soda straws and helictitesremain in pristine condition. Apparently tidalexchange through the system betweenHarrington Sound and Castle Harbour isdirected by way of a route along thesoutheast edge of the cave, while othersections are in a hydrologically more isolatedcul-de-sac.

Palm Cave System, with its five entrances(Cripplegate, Myrtle Bank, Palm, Sailor'sChoice and Straw Market Caves) is locatedimmediately southwest of the WalsinghamSystem. Tidal flow from Castle Harbour firstmoves through the Walsingham System andunder an impenetrable saddle valley ofcollapse origin before entering the PalmSystem and connecting to Harrington Sound.Cripplegate Cave is a tidal spring onHarrington Sound with a shallow underwaterentrance opening up into a room beneaththe entrance pool of Myrtle Bank Cave. FromMyrtle Bank, the cave passage splits, withboth offshoots descending to the main levelof passage development at 18 m depth. Thesouth passage consists of a high but narrowfissure that appears to have originated as avadose canyon. One branch of this fissurepinches out in an area very close toHarrington Sound as evidenced by thepresence of mussel shells on the cave floor.Another side offshoot that takes currentcontinues for several hundred meters beforebecoming too low.

The north passage from Myrtle Bankextends inland and enlarges to a tidal channelabout 5 m in diameter. It then enters a sizablesubmerged chamber situated between thePalm and Sailor's Choice entrances.Climbing over a mound of breakdownbeneath the Sailor's Choice entrance, thepassage changes form to a high, wide riftconnecting to the Straw Market pool.

The Harrington Sound side of the Palm


System is characterized by strong tidalcurrents and a profusion of colorful spongesand hydroids, encrusting the walls. Even theguideline through this section of the cave hasbecome totally overgrown. Visibility is lessthan in other parts of the cave fartherremoved from tidal flow. Bedrock andspeleothems, where visible, are darklystained as in the passageways connectingDeep Blue and Walsingham.

Government Quarry Cave was discoveredduring quarrying operations in 1969 but wasdestroyed when quarrying resumed in themid 19805. The cave contained two pools,one of which was initially explored to acomplex fissure system reaching depths of24 m-one of the deepest underwater cavesin Bermuda. However, before explorationcould continue in the cave, large amountsof refuse and other debris were intentionallybulldozed into the pool to fill it before thequarrying away of the overlying rock. As aresult of this dumping, water in theGovernment Quarry Cave and manyadjacent caves turned anoxic and sulfurous(Iliffe et aI., 1984).

Geological drilling operations atGovernment Quarry encountered a largecave at 18 m depth below sea ievel. The drillbit subsequently dropped to 33 m wherevolcanic bedrock was recovered. This wouldimply that caves in the Government Quarryarea are the deepest in Bermuda and havebeen developed at the island's limestonebasalt interface, averaging about 30 m belowpresent sea level.

Tucker's Town Cave contains an immenseunderwater chamber that is lacking in thespeleothems so characteristic of otherBermuda caves. No passages have beenfound extending away from the chamber.Accumulation of dune-like sand depositscover the cave floor in several locations. Afunnel-shaped depression in the floor at 18m depth was apparently caused by sanddropping into a lower level. Although theceiling shows evidence of a collapse origin.the only visible breakdown is present at thefar end of the chamber from the entrancepool. Water in the cave is exceptionally clearwith no sign of tidal currents.

Numerous other anchialine caves havebeen explored by divers, but many more

Fig. 5: Flowstone shattered by blastingin a cave in a limestone quarry.

discovery in Bermuda, several taxa had beenknown only from the Old World. Twocolorless, eyeless amphipods from the genusPseudoniphargus, P. grandimanus and P.carpa/is, are the first representatives to befound on the western side of the Atlantic.Other species from this genus inhabit cavesand groundwater around the Mediterraneanbasin and northwest Africa, in the Atlanticdrainage systems of Portugal and Spain andin the Azores and Canary Islands. A newgenus and species of calanoid copepod,Paracyclopia_naessi, has been collected fromsix caves in Bermuda. It belongs to the familyPseudocyclopiidae represented previously byonly a single genus inhabiting waters aroundthe British Isles and Norway.

The misophrioid copepod Spe/eophriabiuexiIJa has a sister species inhabitinganchialine caves from the Balearic Islands inthe Mediterranean.

3. Affinities with transoceanic island taxa:The calanoid copepod £nantiosisbermudensis has sister species inhabitinganchialine caves in the Bahamas, Belize,Galapagos, Rji and Palau. The misophrioidcopepod Speleophriopsis scottodicarloibelongs to a genus containing otheranchialine cave species from the BalearicIslands, the Canary Island in the EasternAtlantic, and Palau in the Western Pacific.

Two species of podocopid ostracods,

Fig. 6: Typhlatya i1iffei, an atyid shrimp that with caveadapted sister species inhabits freshwater and marinecaves in the Mediterranean, Atlantic, Caribbean andeastern Pacific.

Fig. 7: Mictocaris halope, a crustacean representing the neworder Mictacea, inhabits several caves in Bermuda and canbe regarded as a "living fossil."theirto

An extraordinarily richand diverse stygobiticfauna inhabits theanchialine caves ofBermuda. Seventy-fivestygobitic species havebeen identified so far fromBermudian caves,including 64 crustaceans, 5mites, 2 ciliates, 2gastropod molluscs, and 2segmented worms. In orderof abundance, the crustaceans include 18species of copepods, 18 ostracods, 7amphipods, 6 shrimps, 6 cumaceans and 3isopods. Notable in their absence areremipedes and thermosbaenaceans.

Despite the isolated mid-ocean locationof Bermuda, many of its endemic anchialinetaxa show highly perplexing biogeographicalaffinities. These general associations can besummarized into the following groups:

1. Affinities with Caribbean and WestAtlantic taxa: Not surprisingly, consideringBermuda's location on the edge of the GulfStream, many of the island's troglobitic taxashow affinities to Caribbean species. Theamphipod Bogidiella (Antillogidiella)bermudensis, isopods Arubo/ana aruboidesand Curassanthura bermudensis, and shrimpJanicea antiguensis are allied with speciesfrom the Antillean region of the Caribbean.Affinities with Bahamian taxa include theshrimp Barbouria cubensis, Typh/atya iliffeiand Parhippolyte sterreri, calanoid copepodEnantiosis bermudensis and halocypridostracod Spelaeoecia bermudensis. Thecalanoid copepocl Epacteriscus rapax and thecyclopoid copepod NeocycJops stock; hadbeen described based on specimens from theCaribbean coast of Columbia before beingreported from Bermuda caves.

2. Affinities with amphiatlantic and OldWorld taxa: Amphiatlantic organisms consistof species inhabitingcaves on opposite sidesof the Atlantic Ocean.The anthurid isopodgenus Curassanthurahas three species: C.bermudensis fromBermuda, C. canariensisfrom the Canary Islands,off the west coast ofAfrica, and C. halmafrom the Caribbeanislands of Bonaire andCuracao.

Prior

of the caves where nowater currents arediscernible and suspendedparticulate matter is absentfrom the water column.

ANCHIALINE CAVE

FAUNA

likely await discovery. Two years ago, blastingin a limestone quarry uncovered a large andremarkably beautiful cave containing a deeplake. I was called in by the BermudaGovernment to document and evaluate thiscave. When I arrived on the island, I foundthat vandals had entered the cave andintentionally smashed speleothems rangingfrom highly colored stalactites and stalagmitesto pure crystalline soda straws and helictites(Figure 4). The effect of nearby blasting wasclearly evident where actively depositingflowstone slabs a meter of more in thicknesshad been sheared apart across the grain(Figure 5). Diving exploration of the lakerevealed the presence of an underwater roomadorned with 1-2 m long straws and fantastichelictites up to 30 em in length.

ANCHIALINE CAVE ECOLOGY

Pools in Bermuda caves typically consistof a 1 to 3 m thick surface layer of brackishwater overlying nearly fully marine seawater.Surface salinities are lowest in those caveswith connections most remote from the seaand may even approach becoming totallyfresh. The highly stratified cave water columnresults from the absence of wind- and waveinduced mixing.

Water temperatures show similarvariations with depth. Surface temperaturesvary seasonally depending on the positionof the pool in relation to the cave entrance.For example, surface water temperatures inthe entrance pool of Walsingham Cave variedfrom 16 to 28°C over the course of a year,while surface temperatures in the deepinterior pool of Crystal Cave ranged from18.4 to 22.6°. Deeper waters in the moreisolated caves remain stable year round at19 to 200C.

Dissolved oxygen levels also vary withdepth. Surface water, in equilibrium withatmospheric oxygen, is saturated, whilewaters below the halocline in more isolatedcaves vary from 56 to 78% saturation.

Anchialine cave pools in Bermudafluctuate with the tides, but with reducedamplitude and a delayed cycle in comparisonwith open waters. Tidal amplitudes in cavesrange from 33 to 87% that of tides in openwaters, while lag times in the tidal cycle varyfrom 9 to 151 minutes.

As was noted for Green Bay Cave,biological zonation varies with the proximityto the cave entrance and the strength of tidalcurrents. Analogous to terrestrial caves, theentrance or twilight zone of marine cavescontain normal open water species typicallyfound in shaded or protected habitats suchas the underside of stones. Many fish andlobster, for example, take up residence in thecave entrance zone. Farther into the cave inareas of total darkness, food resourcesbecome more limited and biomass decreases.Strictly stygobitic (aquatic troglobitic) speciespredominate in the farthest interior regions


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Fig. 8: Antecaridina lauensis is an atyidshrimp known from caves and otheranchialine habitats in a number of widespread locations across the Indo~Pacific

region. It was recently discovered froma saltwater well in Bermuda.

ORIGINS OF BERMUDA'S ANCHIALINE

FAUNAA number of temporal and spatial origins

for the anchialine cave fauna of Bermudahave been proposed. Plate tectonics,stranding of species on the shoreline of afossil sea, and coconut spreading or birdtransfer are considered to be possible, butunlikely, explanations as to how cave speciesfirst reached Bermuda.

The cave shrimp of Bermuda as well asother anchialine invertebrates may have hadthree temporal derivations: (1) recent (fromthe Caribbean by way of the Gulf Stream e.g., Barbouria cubensis and Janiceaantiguensis); (2) during the separation of theAfrican and American continental masses(e.g., Typhlatyajliffei); and (3) from Tethyanrelicts which originated in the shallow tropicalsea that formed between the supercontinentsduring the Triassic period, 205 to 250 millionyears ago (e.g., Parhippo/yte sterreri). Thetransoceanic distributions of cave shrimpssuch as Procaris and Typh/atya as well asother crustaceans including the amphipodPseudoniphargus and the mysid Stygiomysissuggest that such members of the anchialinecave fauna of Bermuda and the Caribbeanmay have originated before the opening ofthe Atlantic in the Jurassic, 150 to 205 millionyears ago.

A possible deep-sea origin of theanchialine fauna is suggested by similaritiesin fauna and environment between the twohabitats. In addition to caves, anchialine

Iliffeoecia i1iffei and Paracypris crispa, areknown only from caves in Bermuda and ananchialine lava tube in the GalapagosIslands. Likewise, the only two speciesincluded in the podocopid genus Kare/oeciainhabit caves in Bermuda and theGalapagos.

In addition to the procarid shrimp Procarischacei from Bermuda, the only othermembers of this genus inhabit anchialinevolcanic caves on Ascension Island in theSouth Atlantic and Hawaii in the mid Pacific,as well as limestone caves on Cozumel in theCaribbean. The atyid shrimp genusTyphlatya, represented by T iliffei in

Using a GIS for Cave and KarstConservation in Bermuda

Bernie Szuka(skiThe islands of Bermuda, located in the

Western Atlantic Ocean approximately1000 km off the coast of North Carolina,contain many significant caves. Bermudais a densely populated country withapproximately 65,000 inhabitants and aland area of roughly 57 squarekilometers. Approximately 150 caveshave been discovered in Bermuda, manyof which are profusely decorated withdelicate and unique speleothems. Manycaves include passages which extend tosea level and contain deep anchiaHnepools and extensive underwaternetworks. A large variety of cave~

adapted life, including previouslyunknown species, have been found inthese underwater caves. Of the speciesidentified in Bermuda's caves 25 arecurrently on the critically endangeredspecies list. The high population densityand resultant development pressures,vandalism, pollution and other negativefactors have significantly impacted andcontinue to threaten Bermuda's uniquecave resources.

In early 2002 the Bermuda Cave andKarst Information System (BeCKIS)project was established with the primarygoals of increasing public awareness ofBermuda's caves and cave life, increasingawareness of negative impacts on theseresources, and promoting the scientificstudy of Bermuda caves. The BeCKlSutilizes GIS software from ESRI, one ofthe project sponsors, to maintain adatabase and inventory of cave locationsand field observations. The GIS is beingused to establish baseline qualityinformation from past observations, andto query and analyze the data and tounderstand relationships with othergeographic and hydrologic factors. Thedevelopment of a GIS database alsofacilitates the production of high qualitycartographic maps invaluable to recordthese features and understand theirsignificance and relationships (as in thecolor GIS images on the facing page).

Bermuda (Fig. 6), includes stygobitic speciesin the Caribbean, South Atlantic,Mediterranean and the Galapagos Islands.

4. Affinities with deep sea taxa: Until theirdiscovery from anchialine caves, misophrioidcopepods had been considered to be a deepsea group. Two species of misophrioidsinhabit Bermuda caves.

The new crustacean order Mictacea isrepresented by only three species: Mictocarisha/ope from Bermuda caves (Fig. 7), Hirsutiabathyalis from 1000 m depth off the Atlanticcoast of Surinam and H. sandersetafia from1500 m depths in the Bass Straits betweenAustralia and Tasmania.

The colorless, transparent oligochaetePha/lodrilus macmasterae from Bermuda ismost closely related to P /obatus from bathyal(200 to 2000 m) depths on the continentalslope off Surinam.

5. Affinities with interstitial/crevicularfauna: The archiannelid polychaeteLeptoneriJIa prospera is the only species fromthis group inhabiting marine caves. All othermarine archiannelids, with the exception ofone deep sea species, are members of theinterstitial sand fauna.

Judging from its minuscule size (0.25-0.27mm), the platycopioid copepod NanocopiaminutaJTlay be of interstitial or crevicularorigins. The amphipod Ingo/fiella /ongipes,described from only a single Bermudaspecimen, appears to have originated fromspecies inhabiting coastal interstitial waters.

6. Living fossil taxa: Such species are relictfauna surviving only in restricted habitats thathave served as a refuge. The isopodAt/antasellus cavernico/us is one of twospecies belonging to the familyAtlantasellidae. The platycopioid copepodAntriscapia prehensiJis, a very primitivespecies, shares many characters with thetheoretical ancestral capepod. Mictocarisha/ope from the new order Mictacea(meaning "mixed or blended") is named forthe common features it has with otherperacarid crustacean orders. It may thus beregarded as representing a missing link in theevolution of the Crustacea.

7. Affinities with primarily stygobitic taxa:Many of Bermuda's anchialine stygobites aremembers of genera or higher taxacharacteristically inhabiting caves orgroundwater. Included in this group are theamphipods Bogidiella (Antillogidiella)bermudensis, Pseudoniphargus grandimanusand P carpaNs; isopods Arubofana aruboidesand Curassanthura bermudensis;misophrioid copepods Spefeophria bivexi/laand Spe/eophriopsis scottodicarfoi;halocyprid ostracod SpeJaeoeciabermudensis; and shrimp Barbouriacubensis, Typhlatya iliffei, Parhippolytesterreri and Procaris chacei. Also noteworthyare the calanoid copepods Epacteriscusrapax, Erebonectes nesioticus and Enantiosisbermudensis which all belong to the

predominantlyEpacteriscidae.

stygobitic family


species have recently been found to inhabitwater-filled crevices and fissures within thebedrock. Such a sub-sea level crevicularhabitat may extend to considerable depthsin the ocean and provide a virtual continuumfrom inland caves to seamount slopes andpotentially even to mid-ocean ridges.However, arguments against a deep seaorigin include the presence of widespreadanoxia in the deep sea during the recent pastand phylogenetics evidence suggesting thatboth cave and deep sea forms separatelyevolved from common shallow waterancestors.

THREATS TO THE ANCHIALINE HABITAT

A number of environmental threats imperilanchialine caves, especially those inBermuda. Quarrying of limestone can beparticularly hazardous in that it not onlydestroys caves but also disrupts groundwatercirculation patterns through the karsticaquifer. Furthermore, any stygobitic speciesin the caves in question are destroyed. Thus,large-scale mining activities and associateddestruction of the cave habitat have thepotential to cause the extinction of endemicspecies. Umestone quarries in Bermuda havecaused the complete destruction of a numberof anchialine caves.

"Deep well injection" (to relatively shallowdepths of approximately 30 m or less) is beingused to dispose of sewage and wastewaterin Bermuda. At least one Yucatan cave closeto an injection site has recently becomepolluted with brown, turbid water below thehalocline. Considering the ever-acceleratingrate of development in many coastal areaswithin the tropics and the lack of propercontrols, the potential for pollution of karstgroundwater is enormous.

Although deep well injection has beenused as a means of disposing of treatedsewage in South Florida, the process iscontroversial at best. The Roridan aquifersystem, which is used for water supplythroughout most of Florida, is a thicksequence of carbonate rocks. In SouthFlorida, the lower strata of the Floridanaquifer contain saline water. These strata at

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760 m depth have high permeability becauseof fractures and solution features and readilyaccept millions of gallons per day ofwastewater. Less permeable carbonate strataoverlying the injection zones have beencounted on to contain the injectedwastewater and prevent upward migrationof the wastewater and/or the resident salinewater. However, at several sites upwardmigration has been evidenced.

The unique limestone/basalt rocksequence in Bermuda is a quite differenthydrogeological setting than Rorida, Thus,problems of groundwater contamination thathave cropped up in Rorida are much morelikely to occur in Bermuda where theinjection wells are much shallower. Deep wellinjection requires special investigation,design, construction, operation, andmonitoring in order not to present a majorgroundwater pollution hazard.

In comparison to open water marineenvironments, anchialine caves are uniquelysensitive to organic pollution. Due to the totaldarkness inherent with caves, photosynthesisand resulting oxygen production does notoccur. Also, the restricted connections ofthese caves to open waters inhibit input ofoxygen from the sea. Thus, depleted levelsof dissolved oxygen are characteristic ofdeeper cave waters. Addition of organicmatter in the form of sewage, plant matteror garbage to cave waters stimulates growthof naturally occurring bacterial populations.These bacteria rapidly consume all availabledissolved oxygen and subsequently producehighly toxic hydrogen sulfide. Thus, organicpollution is extremely serious, inevitablyleading to oxygen depletion, The loss ofoxygen in cave waters due to pollution willresult in suffocation of the aerobic cavemacrofauna.

CURRENT AND FUTURE RESEARCH

Collaborative cave research projects inBermuda are underway with severalscientists on diverse topics. In June 2002,archiannelid polychaete worms werecollected from Bermuda caves for study byKatrine Worsaee of the University ofCopenhagen. In these samples, Katrine hasfound a new species that is highly specializedto the cave habitat. In an environmentdominated by crustaceans, we are finding avariety of other cave-adapted invertebrates.In March 2003, specimens of the crustaceanMictocaris halope were obtained for Dr.Stefan Richter of Humbolt University inBerlin. Stefan is examining the internalanatomy of Mictocaris in order to betterdetermine the place of the order Mictaceawithin the Crustacea. On the same trip,several already broken stalagmites werecollected for use by Dr. Lloyd Keigwin of theWoods Hole Oceanographic Institute intesting theories on climate history in theocean.

In 2002, two of my graduate students,Rebecca Belcher and Darcy Gibbons,obtained summer internships at the BermudaAquarium in order to begin cave-relatedresearch projects. Rebecca is sequencingmitochondrial genes from the atyid caveshrimp Antecaridina fauensis (Figure 8) inorder to compare widely spaced populations.This species was first reported from ananchialine cave in Fiji and later from IndoPacific locations, including the HawaiianIslands, Marshall Islands, Solomon Islands,New Caledonia, Japan, Guam, Philippines,Madagascar and the Red Sea. Recently,shrimp identified as this species werediscovered from a 30 m deep saltwater wellin Bermuda. Rebecca has collected morethan 40 specimens of Antecaridina from theBermuda well and has successfully amplifiedand begun characterizing the sequences ofthree mitochondrial genes. We have alsoobtained Pacific specimens from caves in thePhilippines, Guam and Marshall Island andwill begin to sequence DNA from theseshrimp for comparison. This work shouldprovide insight into the timing and mode ofdispersal of this and other anchialine animals.

Darcy Gibbons is compiling anenvironmental survey of each of the known150+ caves on the island, replicating ahistorical survey of these caves carried outin 1983. The caves are being analyzed forpositive characteristics includingspeleothems, size, and biological andhistorical significance, as well as for negativethreats including the extent of vandalism,water pollution, dumping or littering, andquarrying or construction. When completed,the current data will be compared to thehistorical data in order to analyze whetherthe environmental status of the caves hasimproved or worsened over the interveningtwenty years. Darcy is also analyzing cavewater quality to determine whether there issignificant water pollution such as excessnutrients or fecal contamination.

In order to raise public awareness of theisland's caves and cave animals and todocument threats to this fragile habitat, theBermuda Cave and Karst InformationSystem (BeCKIS) has been erected as acomponent of the Bermuda ZoologicalSociety's Bermuda Biodiversity Project.BeCKIS will locate and map caves andcompile data on their biological, geological,and hydrological. This information will beentered, along with other biological,geological, topographical, land use, andenvironmental data into a comprehensiveGIS database composed of interrelated layersthat can be queried for various planning,ecological or conservation initiatives.

For more information on anchia/ine cavesin Bermuda and elsewhere, please visit ourwebsite at: www.cavebiology.com