Pacific Science (198 1), vol. 35, no. 1© 1981 by The University Press of Hawaii. All rights reserved

A cropora in Hawaii. Part 1. History of theScientific Record, Systematics, and Ecology!

RICHARDW. G RIGG,2 JOHN W. WELLS,3 and CARDEN WALLACE4

ABSTRACT: Present occurrence of the coral genus Acropora in Hawaii haslong been questio ned. This paper reviews the scientific literature concerningthis controversy and presents the results of a recent resource survey of theentire Hawaiian Archipelago tha t clearly estab lishes the presence of threespecies of Acropora in Hawaii. These species are Acropora cytherea, A . valida,and A. humilis. Taxonomic descriptions for each species are presen ted, alongwith notes on their worldwide geographic distribut ions. In Hawaii, the threespecies are found only on six islands in the middle of the chain . Extension oftheir ranges throughou t the archipelago may be limited by discontinuous andsporadic larval recruit ment.

THE HAWAIIAN ARCHIPELAGO consists of ap­proximately 132 high volcanic islands, rockyislets, atolls , reefs, banks, shoals , seamo unt s,and guyots (Armstrong 1973). The islandchain stretches northwest from the Island ofHawaii diagonally across the Pacific to KureAtoll, a distance of 2450 km. Beyond KureAtoll , a series of drowned atoll s (guyots) andseamounts extend the chain to the EmperorSeamounts. The Emperor Seamounts con­tinue northward all the way to the juncturebetween the Kuril and Aleutian trenches.

In spite of the vast geography of theHawaiian Archipelago, knowledge of themarine biota of the Hawaiian Islands was,until abo ut 1976, based largely on researchdone in the major high islands (Hawaii toNiihau) . Prior to this time, knowledge ofmarine flora and fauna of the NorthwesternHawaiian Islands consisted primarily of the

I Hawaii Institute of Marine Biology contributionnumber 608. The Nation al Sea Grant Program and theHawaii State Office of the Marine Affairs Coordinatorprovided funding for this research. Manuscript accepted12 January 1981.

2 University of Hawaii, Hawaii Institute of MarineBiology, P.O. Box 1346, Kaneohe, Hawaii 96744.

3 Cornell University, Departm ent of GeologicalSciences, Ithaca, New York 14850.

4 James Cook University of North Queensland ,Queensland, Australia 4811.

results of the United States Exploring Ex­pedit ion in 1840 and 1841, the "AlbatrossExpedition" in 1902, and the Ta nager Expedi­tion in 1923. In 1976, a five-year researchprogram on wildlife and fisheries manage­ment in the Northwestern Hawaiian Islandswas planned by the National Ma rine FisheriesService, the U.S. Fish and Wildlife Service,the Hawaii State Division of Fish and Game,and the University of Hawaii Sea GrantProgram.

In 1978 and 1979, in connection with thefive-year research plan , the species compo­sition of coral reefs off the islands of Nihoa,Necker, French Frigate Shoa ls, GardnerPinnacles, Maro Reef, Laysan, Lisianski,Pearl and Hermes, Midway, and Kure wassurveyed. This inventory confirmed and doc­umented the presence of the coral genusA cropora in Hawaii. Three species were re­corded. Unti l this discovery , a controversyover the occurrence of Acropora in Hawaiipersisted for many years . In part, this con ­troversy was due to the presence in Hawaiiof Acropora in the geologica l record fromthe Miocene followed by apparent disap­pearance during the Pleistocene. Thus, thepurpose of Part I of this paper is to sum­marize the scientific record of the genus inHawaii, substantiate the taxonomic positionof the three species discovered, and describetheir present patterns of distribution and

2

abundance. In Part 2 of this paper, zoogeo­graphic aspects of Acropora are considered .

METHODS

Stations were selected off all major islandsor reefs in the Hawaiian Archip elago. Ateach station, the species composition andcommunity structure of macro benthic species( » 2 em in the greatest dimension) werequantitatively analyzed by conducting 25-mor 50-m line transects at depths between 5and 15m (Grigg and DoIlar 1980). Qualitativeestimates of abundance of the macrob enthoscovering much larger areas (about 5000 m-)were also coIlected. The number of stationsselected per island ranged between two andeight, depending proportionately on islandsize and diversity of habitats. Where present,fragments from mature (largest) colonies ofAcropora were coIlected and preserved informalin. The reproductive condition ofthese colonies was determined by directlyexamining the mesentaries of decalcifiedspecimens (G rigg and Boucher, ms) and bystandard histological techniques. AIl sam­ples used to determine reproductive condi­tion were collected in the months of Jun e,September , and November. At one station atFrench Frigate Shoals, a core was obtainedfrom a water depth of 10m to ascertain thepresence of Acropora in the recent past .Material from the core was dated usingradiocarbon dating.

The taxonomic position of the three speciesof Acropora was determined from coloniescoIlected in 1978 and 1979 at French Frigateshoals. The Hawaiian specimens were com­pared with a large number of Acropora coralscollected from the Great Barrier Reef. (Thelatter were collected by John Veron andCarden Wallace for a revision of the familyAcroporidae.) Type material of A . variabilisKlun zinger was received on loan from theMuseum fiir Naturkunde, Humboldt Uni­versity, Berlin. Radial corallites are illus­trated by scanning electron micrograph staken at James Cook University, Australia.The terminology used in this paper is definedby Wallace (1978).

PACIFIC SCIENCE, Volume 35, January 1981

SCIENTIFIC RECORD

The protean reef coral genus Acropora,with some 325 nominal species, is one of themost widely distributed of living reef cora lsin the Indo-Pacific, but its current presencein Ha waiian waters has long been doubted.Its absence from early collections of recentHa waiian corals was notable. J. D. Dana, inthe first (1872) and subsequent editions ofhis Corals and Coral Islands, suggested thatthe "Hawaiian Islands . . . are outside of theTorrid Zone . . . , and the corals are con­sequently less luxuriant and much fewer inspecies. There are no Madrepores [A cropora]and but few of the Austraea and Fungiatribes, while there is a profusion of coral ofthe hardier genera, Porites and Pocillopora."Earlier , in 1846, in his great report on thezoophytes of the U. S. Exploring Expedi­tion, Dan a pointed out that "at the Sand­wich Island s, which are near the northernlimits of the coral seas, Porites andPocillopora prevail. . .. " Quelch, in his mon­ograph of the Challenger reef coral s (1886),observed that " it is a noteworthy peculiarityof the coral faun a of the Sandwich Island sthat no representative of the widely dis­tributed genus M adrepora [A cropora] isfound on the reefs." But Brook , in his 1893monograph of the genus, listed the Sand wichIslands as one of the several localities ofMadrepora echinata Dana, although he listedonly three specimens of the species in theBritish Mu seum collections , none of themfrom Hawaii .

For nearly a century there have been onexhibit in the vitrines of the Galerie deZoologie, Museum Nationale d'HistoireNatureIIe , Paris, two specimens of AcroporalabeIled "Madrepora longicyathus M. E. &H. lies Sand wich. M. Ballieu 1874," on theshell of a large Pinctada and " M adreporadurvillei M. E. & H. lies Sandwich. M.Ballieu 1875." These were "discovered" in1978 by Denni s M. Devaney, the curator ofinvertebrates at the Bishop Museum inHonolulu, Hawaii. To an inquiry concerningtheir origin, J. P. Chevalier replied that hecould find no record of their acqu isition andthat M. BaIlieu was unknown to the Museum.

Acropora in Hawaii. Part I -GRIGG, WELLS, AND WALLACE 3

He also pointed out in correspondence "acurious thing: besides this sample , there isanother example of Acropora longicyathuswhich is fixed also on a shell of oyster(Pin ctada) but it comes from Tahiti (coil.Clone, no. I, 1871)." Like Studer's M.echinata, also attached to a pearl oystershell, it is probable that M. Ballieu's coral swere either purchased in Hawaii or wereobtained in Tahiti but were mistakenly attri­buted to Hawaii.

In 1875, when the Challenger stopped inHonolulu, Moseley noted (as Verrill did later)that corals not from Hawaiian waters wereoffered for sale: "There is a large shop ofChinese and Japanese curiosities , and twophotographers' shops, where corals , importedmostly from the Marquesas, and spuriousimitations of native implements manufac­tured for sale, are disposed of, at exorbitantprices to passengers from the mail steamer"(Moseley 1879:456).

The first published evidence of the pres­ence of Acropora in Hawaii came in 1901when Studer described some corals in thecollections of the Berne Museum, includingsome collected in 1896 and 1897 by H. H.Schauinsland at Laysan. Among the Ha­waiian species were several not previouslyrecorded and still not known to occur in theislands: Madrepora (Acropora) echinata (nonPallas), Fungia (Fungia) fungites (Linn .),Fungia (Ct enactis) echinata (Pallas) , Ha­lomitra tiara (= H. pileus [Linn.]) andMerulina regalis? Dana. However, there isno certainty that all of these actually camefrom Hawaii. Studer noted that at least twohad been purchased in Honolulu and thoughtthat they had probably come from elsewherein the Pacific. His figured specimen of A.echinata, a small colony on a large pearlshell, if it did come from Hawaii, is possiblythis species but is different from all threespecies discussed in the present paper. Ayear later Verrill (1902) said that A . echinatawas "probably imported," and that he had

never seen an authentic species of Acropora from Hawaii.Local collectors assert that the genus does not occurthere. But great quantities of corals, etc., are broug htfrom the Polynesian Island s to Honolulu by missionaryvessels and sold there as curiosities . . . and probably this

is the case with the several [actually oneI species ofAcropora recorded from the Hawaiian Island s by Brook.Their occurrence there certainly needs confirmation, forin the large authentic collections of corals I have studiedfrom those islands no Acropora has occurred.

Studer's specimen was figured again byVaughan in his monograph on the Ha waiiancorals (1907) with no comment on its prove­nance, save that "this species has been re­ported from the Hawaiian Islands by Brookand Studer. I have seen no specimens of itfrom there." Later (1910) he apparently ac­cepted it: " A cropora is possibly but notprobably, except for A. echinata, entirelyabsent from Hawaii ." Notwithstanding thevery dubious specimen of A . echinata, it hassincebeen accepted that the genus isnot foundin the Hawaiian coral 'fauna, the nearestoccurrence being at Johnston Island , 720 kmto the southwest, where there are at least fivespecies. Dana's 1872 statement has also beenaccepted as sound, although as late as 1943Vaughan and Wells pointed out that anumber of tropical Pacific coral genera werelacking in Hawaii, and that " Acropora isdoubtfully represented by a single species."

In 1936, a sizable colony of Acropora,probably A . cytherea (Dana), was collectedat French Frigate Shoals northwest of themain island s. About that time, inWashington, D.C. , Paul Galtsoff told JohnWells of the find but said that its whereaboutswere unknown. In 1946, C. H. Edmondsonpublished a photograph of this specimenin his Reef and Shor e Fauna of Hawaii.In reply to an inquiry in 1947 about thespecimen, he wrote that it was not in theBishop Museum, and that "the Hawaiianboys who collected it did not inform me ofits disposition." Was it broken up and sold forsouvenirs? A search at the National Museumof Natural History failed to find any record.Nevertheless, this lost coral was clear ev­idence of the presence of living Acropora inthe Hawaiian Islands, and indicated thatfurther search at French Frigate Shoalswould provide a final answer.

Nearl y 40 years later , an A cropora colonywas found living at a depth of 40 ft off Poipuon the south coast of Kauai . R. A. KinzieIII sent it to John Wells, who tentatively

4

identified it as A . pan iculata Verrill, knownfrom one or two localities in the westernPacific. It was later figured (Ma ragos 1977)with notes on its origin .

Then, in 1977 came the major discovery ofHawaiian A cropora. John Naughton found atabulate colony about 2 ft acro ss at LaPerouse Pinnacles, French Frigate Shoals,some 500 miles northwest of Kauai. Thecolony was subsequently determined to beA . cytherea. More colonies were located byLeighton Taylor. In 1978 and 1979, R. W.Grigg found still more A. cytherea and twoother species, A . valida and A . humilis, thefirst two in relatively large numbers at depthsranging from 3 to 20 m at a variety oflocalities at French Frigate Shoals. This dis­pelled any idea that Acropora is a rareHawaiian coral and ' initiated the presentpaper.

TAXO NOM Y

The three species of Acropora in Hawaiiidentified from specimens collected at FrenchFrigate Shoals are A . cy therea (Dana), A .valida (Dana) (= A. variabiiisi, and A .humilis (Da na). All of these species havebroad Indo-Pacific distributions, and alloccur in some locations of the type dubbed"marginal belts" by Crossland (1949), char­acter ized by "absence or almost absence ofthe great reef builder , the genus Acropora."

Unfo rtunately, with knowledge of thebiology of Acropora in a poor state, it is notpossible to discuss special life-history strat­egies of these species which might explaintheir broad distribution. However , all can beassociated with either severe or unpredic­table conditions. A. cy therea is known on theGreat Barri er Reef (mainly from unpub­lished observation s) as one of the plate­forming species which are early colonizers ofdisturbed areas. A . valida characteristicallyoccurs as the dominant (and sometimes theonly) A cropora in the austere conditions ofthe algal ridge (e.g., in the Marshall Island s).Similarly A . humilis is a dominant (orcodominant) cora l on windward reef front sreceiving extreme wave action on the GreatBarrier Reef.

PACIFIC SCIENCE, Volume 35, January 1981

Acropora cy therea (Dana, 1846)

M adrepora cytherea Dana , 1846 :441,pI. 32, fig. 3a, 3b; Brook 1893: 99(synonymy).

Acropora cytherea: Crossland 1952: 215;Wallace 1978: 289, pis. 63, 64A, 64D,66C, 66D, 67.

M adrepora efflorescens Dana , 1846 :441,pI. 33, fig. 6; Brook 1893:35(synonymy).

? Acropora efflorescens: Pillai and Scheer1976:26, pI. 3, fig. 3.

M adrepora armata Brook, 1892:452;1893: 100, pI. 10, figs. A, B (synonymy).

M adrepora reticulata Brook, 1892: 461;1893:68, pI. 4, figs. A, B.

Madrepora reticulata var. cuspidata Brook ,1893:69.

A cropora reticulata: Wells 1954:422, pI.11 0, figs. 4-6, pI. 114, figs. 1-6(synonymy); Pillai and Scheer 1976:28,pI. 7, fig. 1.

M adrepora arcuata Brook, 1893 : 102, pI.12; Studer 1901 :395.

Acropora cytherella Verrill 1902 :253, pI.36, fig. 7, pI. 36a, fig. 7, pI. 36f, fig. 1(synonymy).

A cropora corymbosa "cytherea Form " :von Marenzeller 1907:32, pI. 1, figs. 1,2, pI. 2, fig. 3.

Acropora hyacinthus (part): Hoffmeister1925:64; Wells 1954:421.

MATERIAL EXAMINE D: 4 specimens col­lected at French Frigate Shoals, July 1979.

DESCRIPTION: This species occurs as stalkedtables, up to 480 em in diameter, with amore or less rounded outer edge, sometimeswith additional platelike layers. Color is palebrown.

SKELETON: The specimens are all portionsof flat plates (figure l a). The primary direc­tion of branching is horizontal and there isconsiderable, but not complete, ana stomosisof horizontal branches. From these branches,short vertical to oblique branchlet s mainly5-10 mm in length arise singly or in groups(figure Ib ). The radial corallites are ap­pressed tubul ar with the outer wall extendedupward as a lip. Many radial corallites are intran sition to axial corallite sta tus, and these

Acropora in Hawaii. Part i -GRIGG, WELLS, AND WALLACE 5

FIGURE I. Acropora cytherea: a, general view, O.5x ; b, S.E.M. of branchlet bundle , 8x ; c, S.E.M. of coenos teumbetween corallites, 180x ; d, S.E.M. ofradial corallites, 18x .

appear tubular with dimidiate openings. Theaxial corallites are usually 2-5 mm exert.Their outer diameter is 1.5-2.5 mm, innerdiameter 0.6-1.2 mm. The primary septa areall present, up to tR; the secondary cycle isabsent, or occasionally 1-3 septa are justvisible. The coenosteum is costate on radialcorallites and reticulate with scattered, later­ally flattened spines elsewhere (Figure Ic, d) .

DEPTH RANGE AT FRENCH FRIGATE SHOALS :

3-20m.

GEOGRAPHIC DISTRIBUTION: Madagascar(Pichon, personal communication), Masca­rene Archipelago (Faure 1977), AmiranteIslands, Seychelles, Maldives, Minicoy, Ara-

fura Sea, China Sea, Great Barrier Reef,Solitary Islands, Funafuti Atoll , Fiji Islands,Marshall Islands, Tahiti, NorthwesternHawaiian Islands, Hawaii .

DISCUSSION: This is a common reef-frontspecies, sometimes referred to as A. reticulata,a synonym, and sometimes confused with A.hyacinthus. On many reefs A . hyacinthus andA. cytherea have overlapping distributions,with the former shallower than the latter. A.hyacinthus does not have the long axial co­rallites of A . cytherea; its radial coralliteshave more rounded lips and are more evenlyarranged on branchlets. There is a slightpossibility that some of the table colonies atFrench Frigate Shoals are A . hyacinthus .

6

Acropora valida (Dana, 1846)

M adrepora valida Dana, 1846: 461, pI. 35,fig. 1; Brook 1893: 168.

Acropora valida: Hoffmeister 1925:60, pI.12, figs. 1, la-c; Wells 1954:429, pI. 130,figs. 7-9; Nemenzo 1967:99, pI. 30; Pillaiand Scheer 1976: 29, pI. 7, figs. 3,4; ZouRen-lin 1978: 107.

Madrepora variabilis Klunzinger, 1879: 17,pI. 1, fig. 10, pI. 2, figs. 1, 5, pI. 5, figs. 1,3, pI. 9, fig. 14; Brook 1893: 161.

Acropora variabilis: von Marenzeller1907:49, pI. 15, figs. 40-44; Vaughan1918: 181, pI. 80, figs. 2, 3, 3a, 3b;Faustino 1927:276; Wells 1950:38 ;1954:428, pI. 128, figs. 1,2, pI. 130, figs.1, 2; Rossi 1954: 52; Stephen son andWells 1956: 19; Scheer and Pillai 1974:23, pI. 8, fig. 2; Pillai and Scheer 1976:31 ; Zou Ren-lin 1978: 107; Wallace1978:299, pI. 80C, D.

Acropora variabilis var. pachycladosKlunzinger: Crossland 1952:222, pl. 38,figs. 1, 6.

MATERIAL EXAMI NED: 5 specimens, collect­ed at French Frigate Shoals, July 1979.

DESCRIPTION: This species is corymbose ingrowth form (Figure 2a). Colonies up to 30em high and 40 em wide occur at FrenchFrigate Shoals. Color is tan.

SKELETON: From a central attachmentarea, branches arise vertically to obliquely ,sometimes branching again, and sometimesproliferating at the tip. Branches are 7-12mm greatest diameter, up to 70 mm in length,and only slightly tapering. Radial corallitesare of mixed length, or mainly all of similarlength, up to 5 mm long, partly to fullyappressed tubular (Figure 2c). The openingsare oval, directed at 45° to 90° to the branch,the outer edge of the wall sometimes extendsupward and is slightly liplike. Primary septaare all present, usually up to tR, but some­times to tR; the secondary cycle is partly tofully present , up to i-R. Axial corallites arearound 1 mm exert, with outer diameter2.0-2.8 mm, inner diameter 1.0-1.3 mm.Primary septa are present , up to t R;secondary septa are absent , or 1 to 3 present ,

PACIFIC SCIENCE, Volume 35, January 1981

to less than i-R. The coenosteum consists oflines of laterally flattened spines (Figure 2b).

DEPTH RANG E AT FR ENCH FRIGATE SHOALS:

3-20 m.

GEOGRAPHIC DISTRIBUTIO N: Madagascar(Pichon , personal communication), Ma sca­rene Archipelago (Faure, personal com­munication), Red Sea, Maldives , Andamans,Nicobar Island , Mergui Archipelago, Singa­pore, Philippines, China Sea, Great BarrierReef, Solitary Islands (Veron et al. 1974),Fiji Islands, Marshall Islands, New Cale­donia, Tonga, Tuamotus, NorthwesternHawaiian Islands.

DISCUSSION: The two species A . valida(type locality, Fiji Islands) and A. variabilis(type locality , Red Sea) are here combinedfor the first time, as the relatively little­treated species A. valida falls well within thelarge range of variability recorded for A.variabilis. The French Frigate Shoals speci­mens are similar in all characteristics, exceptthe inner axial corallite diameter, to somespecimens from the Palm Island group,Great Barrier Reef.

Acropora humilis (Dana, 1846)

M adrepora humilis Dana, 1846:483, pI.31, fig. 4, pI. 41, fig. 4.

Acrop ora humilis: Wells 1954:425, pl. 100,fig. 1, pI. 126, figs. 1-6, pI. 127, figs. 3,4, pI. 128, figs. 3-5 (synonymy) . Rossi1954:50; Stephenson and Wells 1956:15; Scheer 1967:424, figs. 4, 5; Pillaiand Scheer 1976:32; Zou Ren-lin 1978:105; Wallace 1978:300, pis. 81, 82, 83.(For a complete synonymy refer to Wells1954.)

MAT ERIAL EXAMINED: 1 specimen collectedat French Frigate Shoals, 8 m depth, July1979.

DESCRIPTION: The specimen examinedcomprises small pieces from a corymbo se orcaespitose colony (Figure 3a). The longestbranch is 55 mm in length , and the broadest22 mm. Radial corallites are mixed sizes,up to 3 mm diameter and 3 mm in length ,

Acropora in Hawaii. Part I-GRIGG, WELLS, ANDWALLACE 7

FIGURE 2. Acropora valida: a, general view, O.7 x ; b, S.E.M. of coenosteum between corall ites, 16x ; c, S.E.M . ofradial corallites, 160x.

projecting at 90° to branch, tubular with di­midiate openings and thickened walls (Figure3b). Axial corallites are 1.5 mm exert, 4.0­5.5 mm outer diameter, 1.0-1.5 mm innerdiameter. Both septal cycles are developed,primaries to t R, secondaries to ±R. Co­enosteum is a dense arrangement of costae

on radial corallites, with lines of laterallyflattened spines between radial corallites.

GEOGRAPHIC DISTRIBUTION: Madagascar(Pichon 1978), Mascarene Archipelago(Faure 1977), Red Sea, Arafura Sea, Mal­dives, Cocos-Keeling, Philippines, China

8 PACIF IC SCIENCE, Volume 35, Jan uary 1981

FIGURE 3. Acropora humilis : a, genera l view, I x; b, S.E.M. of radial corallites, 16x .

1000 FFSDISTRIBUTION AND ABUNDANCE

500OF ACROPORA

IN THE HAWAIIAN ARCHIPELAGO

.."'E 100 ABUNDANT MARa -Acropora cytnerea0

,CJ Acropora valida0 50

COMMON0 ISSS'3 Acropora humilis10...... ,(J)

lJJZ GARDNER0 10 -r---l0 UNCOMMONo 5

,u,0

-r- LAYSANa: RARElJJ ,CD::E KAUA I NI HOA::::>z

05

H M 0 NE LI PH MK018 19 20 21 22 23 24 25 26 27 28 29 30

L ATITUDE (ON)

FIGURE 4. Distrib ution and abundance of Acropora spp. in the Hawaiian Archipelago in the most favorablehabitats. Note that abunda nce is expressed on a log scale. This is done to emphasize the importance of one colony,that is, the capabili ty of colonization. Only one colony of A . cy therea was found on Kauai and Nihoa and two onLaysan, clearly setting the outer limit of the distribution. The center of the distribution is French Fr igate Shoa ls,where over 1000 colonies of A. cytherea can be found in a 5000 m2 area.

Acropora in Hawaii. Part I -GRIGG, WELLS , AND WALLACE 9

Sea, Great Barrier Reef, Solitary Island s(Veron 1974), Solomon Island s, Samoa, Fiji,Marshall Islands, Tuamotus, French FrigateShoals, Hawaii .

DIS CUSSION: This species, as revised byWells (1954), has a long list of synonyms.Studies underway on the Great Barrier Reefsuggest that this lumping may be too ex­treme, and that two, or even three , speciesmay be involved . However, there is no doubtthat the French Frigate Shoal s material isthe same species as A. humilis s. s. A. humilisis characteristically a shallow-water Acroporaoccurring as a dominant species on outer reefflats and the upper few meters of exposed reeffronts , but it does also occur commonly onhorizontal reef surfaces that are subtidal andnot exposed to strong wave action. In the firstsituation, colonies tend to have a broadlyencrusting base (of a similar diameter to thecorallum) from which branches arise verti­cally with little or no secondary branching(e.g., see Wells 1954, pI. 128, fig. 5; Morton1974, fig. IOD; Wallace 1978, pI. 8IA). In thesecond, the attachment diameter is smallerthan that of the corallum, and secondarybranching is more frequent (e.g., see Wallace1978·, pI. 8IB). The French Frigate Shoal smaterial is in the second category.

DISTRIBUTIO N, ABUNDA NCE, AND

REPRODUCTIV E BEHAVIOR

The result s of coral reef surveys off allmajor islands in the Hawaii an Archipelagoindicate that species of Acropora occur ononly six islands (Kauai, Necker, FrenchFrigate Shoal s, Gardner Pinnacles , MaroReef, and Laysan, Figure 4). Three speciesof Acropora were found at French FrigateShoals and Maro Reef, whereas only onewas collected at Kauai, Necker, GardnerPinnacle s, and Laysan islands. The distribu­tional center for all three species appears tobe at French Frigate Shoal s, where they aremost abundant (Figure 4). A . cytherea andA . valida are about three times more abun­dant at French Frigate Shoals than at MaroReef. In some localities at French FrigateShoals, A . cytherea occupies an average of

40 percent of the bottom cover (Figure 5).The largest colonies of A . cy therea measuredat French Frigate Shoals are 480 em indiameter.

At French Frigate Shoals A. cy thereaoccurs between .depths of 3 and 20 m inman y habitats : inside the lagoon on patchreefs, in areas partially protected from opensea, and off all exposed sides of the island.The most well-developed colonies occur atthe southwestern end of the "atoll" nearDisappearing Island . A . valida occur s inmore restricted habitats partially protectedfrom open sea but at similar depths. Onecolony of A . humilis was found at FrenchFrigate Shoal s inside the barrier reef at adepth of 10 m. Several other colonies of A.humilis were found at Maro Reef also near10m depth. Of the three species of A croporain Hawaii, only A . cy therea has a variablegrowth form dependent upon habitat. Insidethe barrier reef, vasiform colonies of A.cytherea grow higher off the bottom withtaller and narrower supporting basal sta lksthan colonies outside the reef. Coloni es inareas exposed to open sea are more heavilybranched and thicker than colonies in pro­tected habitats.

The distributional patterns of all threespecies are very patchy. For example , thesighting of one colon y during a survey wouldinvariably increase the probability of findinganother colony of the same species. Aggre­gation could result from gregarious larvalbehavior or immediate settlement or couldbe due to physical fragm entation. At FrenchFrigate Shoals many settlement sites can bedistingui shed, hence larval sett lement mustoccur from time to time. Even so, larvalrecruitment may not be a continuous pro­cess. The size frequency distribution of A.cy therea is relatively continuous, suggestinglow year-class variability; however, thiscould also be a result of frequent frag­mentation. In June 1978, 36 colonies of A.cytherea at 10m adjacent to La PerousePinnacle were measured and tagged in orderto determine growth. In September 1979,the same area was resurveyed , but only 16tagged colonies could be found . It was evi­dent that man y colonies in this area had

10 PACIFIC SCIENCE, Volume 35, January 1981

FIGURE 5. Benthic photo-transect conducted at French Frigate Shoals at 10 m depth on the outer reef south ofDisappearing Island . In this area Acropora cytherea accounts for 40% of the bottom cover.

been fragmented or overturned. In January1979, a severe "Kona" storm hit this portionof the archipelago and may have caused theobserved destruction. In any case, it wouldappear that the aggregated patterns of distri­bution for both A. cytherea and A. valida aredue to both fragmentation and larval be­havior , at least at French Frigate Shoals.

In order to determine the degree to whichlarval settlement within the archipelago isdue to local reproduction versus outside re­cruitment, colonies of A . cytherea andA . valida were collected at French FrigateShoals, Maro Reef, and Laysan Islandduring as many months of the year as pos­sible. Each collection consisted of fragmentsbroken from the largest (most mature)colonies present. The mesenterial septa ofpolyps from these colonies were examinedand all oocytes and spermaries were mea­sured. Unfortunately, the results are incon­clusive, primarily because the data cover too

few months to detect whether or not anannual cycle exists or whether or not gona­dal material in colonies from these islandsever reaches reproductive maturity (Table 1).

The largest oocyte or spermary recordedin the three species of Acropora on anyHawaiian island was 41011 in A . cytherea,24011 in A . valida , and 25011 in A. humilis(fable I). Recent work in Australia byCarden Wallace and Jamie Oliver (personalcommunication) on reproductive cycles ofAcropora indicates that mature or near­mature colonies of A . cytherea containoocytes up to 93411 in length and spermariesup to 132111 in length. Equivalent measuresfor A . valida are 128011 for oocytes and328011 for spermaries. These data leave littledoubt that all the colonies examined inHawaii of at least these two species, andprobably of A . humilis as well, were in animmature state. Since the Hawaiian datawere collected over a six-month time period

Acropora in Hawaii. Part I -GRIGG, WELLS, AND WALLACE

TABLE 1

REPRODUCTIVE CONDITION OF A cropora spp. IN THE NORTHWESTERN HAWAIIAN ISLANDS

11

SPECIESAND

LOCATION

NUMBER NUMBER PERCENTMONTH COLONIES POLYPS POLYPS

COLLECTED COLLECTED EXAMINED WITH GONADSOOCYTE

LENGTH (urn)SPERMARY

LENGTH (um)

Acropora cythereaF FS*

FFS

Maro

Laysan

Laysan

A cropora validaFFS

Maro

Acropora humilisMaro

* French Frigate Shoals

Sept. 1980

Nov. 1978

June 1979

June 1979

Sept. 1980

June 1979

Sept. 1980

Sept. 1980

20

4

7

2

20

6

64

21

32

10

10

15

65

24

44%

100%

0%

0%

10%

93%

7%

62%

n = 45x = 106

SD = 44.5Range = 35-300

n = 82x = 238

SD = 83.4Range = 110-440

n= ­x= -

SD= ­Range = -

n= ­x= -

SD= ­Range = ­

n= ­x= -

SD= ­Range = -

n = 85x = 72

SD = 46.5Range = 15-240

n = 18x = 58

SD = 26.0Range = 30-110

n =40x = 128

SD = 56.0Range = 50-250

n =40x = 126

SD = 36.9Range = 80-220

n = ­x= -

SD= ­Range = ­

n= ­x= -

SD= ­Range = -

n= ­x= -

SD= ­Range = ­

n=2x = 100

SD=ORange = -

n=2x = 110

SD = 70.7Range = 60-160

n= ­x= -

SD= ­Range = -

n=3x = 153

SD = 50.3Range = 60-200

(June, September, November), it would besurprising but not impossible to have missedthe season in which reproductive maturityoccurs in all three species. On the basis ofexisting data it therefore appears unlikelythat species of Acropora in Hawaii success­fully produce larvae. Recruitment may de­pend entirely on recolonization from outsidethe archipelago . If this conclusion is correct,the patterns of distribution and abundanceof Acropora in Hawaii should reflect thepresent route of colonization (see Acroporain Hawaii . Part 2. Zoogeography).

Observations at Gardner Pinnacles (mid­way between French Frigate Shoals andMaro Reef) may shed further light on thequestion of the source and frequency oflarval recruitment in the Hawaiian Archipel­ago. At Gardner Pinnacles in 1978, most ofthe reef at 10m depth was dominated byvery large (1-10 m diameter) but dead col­onies of A . cytherea. Only three living col­onies were sighted in 1978, all less than 4 emIn diameter. On the surface of the deadcolonies of A. cytherea, the largest coloniesof P. lobata that were present were collected

12

(n = 10) and later sectioned in the labor­atory so that growth bands could be counted(Buddemeier, Maragos, and Knutson 1974;Grigg and Dollar 1980). The oldest colonieswere 16 years, suggesting that some catastro­phic event prior to 1962 killed all of the A.cyth erea at Gardner. Since that time, theonly successful recruitment appears to havebeen in the last year or two. Either survivalof recruits at Gardner Pinnacles is very lowor recruitment is a very sporadic process (onthe order of once in 15 years). This mayexplain why Acropora spp. have not dis­persed to more islands in the chain. If thesource of recruitment is within the chain (ifthe center of distribution is French FrigateShoals), the Gardner data suggest that repro­duction is sporadic, possibly only in verywarm years. Alternatively, recruitment maydepend entirely on sporadic colonizationfrom outside the archipelago.

While recruitment of Acropora in Hawaiimay be discontinuous and severe mortalitymay be intermittent, it appears as thoughA cropora has been in Hawaii for some time.In 1979, two 50-cm cores, 5 em in diameter,were extracted from the reef at a depth of 10m at French Frigate Shoals . At the bottomof one of the cores was a piece of fossil coralidentified as Acropora (Michel Pichon , per­sonal communication). Unfortunately thispiece of coral was unsuitable for radiocar­bon dating due to a high calcite content.However, directly above the Acropora therewas an intact fragment of Porit es suitablefor radiocarbon dating. The radiocarbon ageof this fragment is 414 ± 68 years. This isclear evidence that Acropora has been inHawaii since before the time of Westerncontact (1778). The zoogeographic implica­tions of this finding coupled with the dataon reproduction, ecology, and possible re­cruitment from outside the archipelago aresufficientlycomplex to warrant separate treat­ment and therefore are considered in Part 2of this paper.

ACKNOWLEDGEMENTS

The assistance of the National Sea GrantProgram and the Hawaii State Office of the

PACIFIC SCIENCE, Volume 35, January 1981

Marine Affairs Coordinator is gratefullyacknowledged. Steven J. Dollar, MichaelPalmgren, Lisa Boucher , Catherine Agegian ,and Tony Chess assisted in various aspectsof the fieldwork . James Maragos made avail­able to us the only known sample ofAcropora from the Island of Kauai. LisaBoucher analyzed the reproductive conditionof all of the Acropora samples from Hawaii.We would also like to thank J. Darley, E. M.Centre , James Cook University, for adviceand use of equipment; the AustralianInstitute of Marine Science for photographicassistance; and Dr. D. Kuhlmann, Museumfiir Naturkunde, Berlin, and Dr. YossiLoya , Tel-Aviv University, for the loan ofspecimens.

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