Freshwater and subaerial diatom floras have not been extensively
examined in the Hawaiian Islands. This paper reports the study of a subaerial
diatom flora in a small steam vent near Kilauea Crater, Island of Hawaii. A total
of 35 taxa was identified , 3 of which are new records for the state. The Kilauea
vent flora is unusual in floral composition and differs markedly from other
Hawaiian subaerial diatom floras we have studied, particularly in the dominance
of Anomoeoneis serians var. brachysira and Frustulia rhomboides

McMillan, Mischelle

Rushforth, Samuel R.

Pacific Science

ScholarSpace at University of Hawai'i at Manoa

Pacific Science (1985) , vol. 39, no . 3© 1985 by the University of Hawaii Press. All rights reservedThe Diatom Flora of a Steam Vent of Kilauea Crater,Island of Hawaii 1MISCHELLE McMILLAN and SAMUEL R . RUSHFORTH2ABSTRACT: Freshwater and subaerial diatom floras have not been extensivelyexamined in the Hawaiian Islands. This paper reports the study of a subaerialdiatom flora in a small steam vent near Kilauea Crater, Island ofHawaii. A totalof 35 taxa was identified , 3 of which are new records for the state. The Kilaueavent flora is unusual in floral composition and differs markedly from otherHawaiian subaerial diatom floras we have studied, particularly in the dominanceof Anomoeoneis serians var . brachysira and Frustulia rhomboides.RESULTS AND DISCUSSIONscraping algae from exposed lava walls and bycollecting visible bryophytes. This materialwas placed in a vial and returned to ourlaboratory.The sample was cleared according to stan-dard methods using boiling nitric acid (St.Clair and Rushforth 1977) and mountedin Naphrax resin. Slides were examinedusing Zeiss RA microscopes with Nomarskiinterference-phase and bright-field objectivesand accessories. Photographs were taken ofeach taxon when possible, using Nikon AFMphotomicrographic equipment.In order to obtain information on the dia-tom community structure, 400 diatom frus-tules were counted and percent relative densityfor each taxon was calculated. These datawere also used to calculate a Shannon-Weaver diversity index (Patten 1962, Shan-non and Weaver 1949).A total of 15 diatom genera containing 35taxa was identified in our material. TheKilauea flora was dominated by relatively fewspecies, with the majority being present in lownumbers. For instance, Anomoeoneis seriansvar. brachysira and Frustulia rhomboides to-gether comprised 74.0% of the population.The next two most abundant taxa, Pinnulariatermitina and Achnanthes linearis, contributed6.7% and 4.4%, respectively, to the popula-tion, for a total 0[85.1 % for the top four taxa .294MATERIALS AND METHODSMANY WORKERS in our laboratory havestudied the freshwater flora of the HawaiianIslands for the past several years in an effort tocharacterize the resident algal taxa. Initially,we examined the flora of several freshwaterstreams (Fungladda, Kaczmarska, and Rush-forth 1983). Subsequently, we studied the sub-aerial diatom flora of Thurston lava tube(Rushforth, Kaczmarska, and Johansen 1984).The present paper is the first in a series inwhich the algal floras ofunusual subaerial andspring habitats are examined.This paper discusses the diatom flora of asteam vent of Kilauea Volcano, Island ofHawaii . This vent is located approx. 1km westof Volcano House near State Highway 11 .The vent substrate we collected was a wet wallthat was moistened by steam rising from thevent aperture. The steam was cooled by thetime it reached the vent opening, condensingand thoroughly moistening the surroundinglava surfaces . Mosses and other bryophytesgrew on these walls, as did green and blue-green algae . Diatoms also grew on these wallsin association with the bryophytes and algae.A composite sample was obtained 28 April1982 from the surface of the steam vent by1 Manuscript accepted 3 April 1985.2 Brigham Young University , Department of Botanyand Range Science, Provo, Utah 84602.Diatom Flora of a Steam Vent-McMILLAN AND R USHFORTH 295Nine of the organisms were present only assingle specimens in our count. The dominanceof a relatively few taxa in the flora is alsoreflected by the low Shannon-Weaver diver-sity index of 1.722.The Kilauea flora is strikingly differentfrom that of a subaerial wet wall at Thurstonlava tube, Island ofHawaii (Rushforth, Kacz-marska, and Johansen 1984), which is only4 km south of the Kilauea vent. The Thurstonflora had a greater biomass of living diatomsand contained 30% more species, for a total of49 taxa. More important, the Thurston florahad only 7 taxa in common with the Kilaueaflora, and the dominant species at the two siteswere entirely different. This is interesting sincethe lava substrates at the two localities wereapparently equivalent and the bryophytefloras were macro scopically similar. However ,the substrate was wetter at the Thurston siteand diatoms not only colonized bryophytesbut formed mucilaginous mats directly uponthe lava walls as well. This is in contrast tothe Kilauea vent site where there was littleexposed lava for colonization and the dia-toms were primarily epiphytic. In addition,the vent locality was less protected and there-fore should experience increased insolation. Itis also possible that the steam in the Kilaueavent carries chemicals that influence floralcomposition.Many of the organisms we found in theKilauea vent are cosmopolitan and have beencollected on wet walls in other parts of theworld. However, the Kilauea flora as a wholeis different from any we have studied in NorthAmerica (Clark and Rushforth, in press ;Rushforth et al. 1976) and from those re-ported in other parts of the world (Hustedt1930-1966, Patrick 1977). Particularly note-worthy is the absence of Cymbella and Den-ticula species and the reduction in Achnanthesand Navicula species in the Kilauea flora.Three of our taxa from the Kilauea siterepresent new records for the HawaiianIslands. These are Navicula muticoides, Nitz-schia frustulum var. subsalina, and Nitzschiaminutula. In addition, it is likely that our Gy-rosigma species represents a new record. It isinteresting to note that there is an absence ofendemic species in the Kilauea vent flora . Theapparent paucity of endemic taxa in theHawaiian flora was discussed by Fungladda,Kaczmarska, and Rushforth (1983) and sup-ports the hypothesis that diatom dispersal tothe islands does not seem to be a limitingfactor in the development of the local floraand that little local speciation has occurred.TAXONOMIC SECTIONIn the remainder of this paper, each taxonis described and discussed briefly. Taxa arelisted alphabetically.ACHNANTHESAchnanthes lanceolata (Breb.) Kuetz. (Fig-ure 1, 1,2). Valve 10-12.5 JIm long by 5-6 JImwide; striae 14-15 in 10JIm on both valves.Only two valves of this taxon were noted inour material.Achnanthes linearis (W. Sm.) Grun. (Figure1,3,4). Valve 8.5-1 1.5JIm long by 2-4JImwide; striae (22)24-26 in 10JIm on bothvalves. This taxon was fourth most com-mon in our sample, comprising 4.4% of thepopulation. We placed our specimens intoA : linearis rather than A . minutissima on thebasis of coarser striation.Achnanthes montana Krasske (Figures 1,5,6). Valve 10-12.5 JIm long by 5-6JIm wide;striae 18-20 in 10JIm, becoming somewhatfiner near ends. This taxon was present atKilauea only as two valves.AMPHORAAmphora normanii Rabh. Valve 26 JIm longby 5JIm wide; striae 11 -12 in 10JIm. Thistaxon was present in our collection as a singlevalve.ANOMOEONEISAnomoeoneis serians var . brachysira (Breb.ex Kuetz.) Hustedt (Figure I, 7, 8). Valve16-21.5 JIm long by 5-6 JIm wide; striae296 PACIFIC SCIENCE, Volume 39, July 19851026162120151914FIGURE I. 1,2, Achnanthes lanceolata; 3, 4, Achnanthes linearis; 5, 6, Achnanthes montana; 7,8, Anomoeoneis seriansvar. brachysira; 9, 10, Eunotia curvata var. subarcuata; 11, 12, Cocconeis placentula var. lineata; 13, Eunotia polydentula;14,15, Bacillariapaxill!fer, x 1260; 16, Eunotiapraerupta var. inflata; 17, 22, Eunotia tenella; 18, Pinnularia leptosoma;19, Gomphonema brasiliense; 20, Gomphonema parvulum; 21, Gomphonema parvulum var. lagenula: 23, Frustuliarhomboides; 24, 25, Melosira roseana; 26, Frustulia vulgaris var. elliptica. All figures are x 2000 unless otherwise noted.Diatom Flora of a Steam Vent-McMILLAN AND R USHFORTH 29726-28 in lO,um at the middle of valve, becom-ing more than 30 in 10 ,urn near ends. This wasthe most abundant taxon in our collection. Itcomprised 53.6% of the population.BACILLARIABacillaria paxillifer (0. Muell.) Hendey(Figure 1, 14, 15). Valve 72-82,um long by5-6.5,um wide; fibulae not equidistant, 7-8 in10,um;striae 24-26 in 10 ,urn. This taxon waspresent as two intact valves and fragments inthe Kilauea material.COCCONEISCocconeis placentula var. lineata (Erh .)Cleve (Figure 1,11,12). Valve 15,um long by8,um wide; striae on both valves 22 in 10 ,urn.This taxon was represented by one completevalve and fragments in our material.EUNOTIAEunotia curvata var. subarcuata (Naeg.)Grun. in V.H. (Figure 1,9,10). Valve lunateor arcuate, dorsal and ventral margins paral-lel, 7-1O.5,um long by 2.5-3,um wide; striae21-24 in 10 ,urn. This taxon was the most com-mon Eunotia in our material. Our specimenswere smaller than usual for this variety but fitquite well in other respects (Wahrer 1981).Some of our smaller specimens were nearlyovoid in shape, with poorly visible terminalnodules.Eunotia polydentula (Brun .) Hust. (Figure1, 13). Valve 10.5 ,urn long by 3 ,urn wide; striaesomewhat radiate, 20-22 in 10 ,urn. This Eu-notia was present in the Kilauea material onlyas a single intact specimen and as broken frag-ments. Striae were very fine in our specimens .Eunotia praerupta var. inflata Grun. (Figure1,16). Valve about 28,um long by 6,um wide;striae 12 in 10,um at the middle of valve,becoming 14-15 in lO,um near ends . Thistaxon was present as a single broken valve inour material.Eunotia tenella (Grun.) Cl. (Figure 1, 17,22). Valve slightly swollen at the middle,19-25.5,um long by 3-4.5,um wide; striae15-18 in 10,um at the middle of valve, becom-ing finer near ends . This taxon was present asfive, or six complete valves in our material.FR UST ULI AFrustulia rhomboides (Ehr.) DeT. (Figure 1,23). Valve 42-55,um long by 11 -12,um wide;transverse and longitudinal striae 28-30 in 10,urn. This taxon was the second most commonin our material. It comprised approx. 20.4%of the Kilauea vent population. Only thenominate F. rhomboides occurred in the steamvent. Both F. rhomboides var. saxonica and F.rhomboides var. capitata are common in otherHawaiian localities.Frustulia vulgaris var . elliptica Hust. (Fig-ure 1, 26). Valve 41 ,urn long by 9 ,urn wide,with rounded ends; transverse striae radiate atmiddle of valve, becoming convergent nearends, 38-40 in 10 ,urn; longitudinal striae28-30 in 10 ,urn. Only a single valve of thistaxon was observed in our material.GOMPHON EMAGomphonema brasiliense Grun. (Figure I,19). Valve 23 ,urn long by 5 ,urn wide; striaeparallel in the center of the valve, becomingradiate near the ends , 15-16 in the middle ofthe valve, becoming somewhat finer near theends. This taxon was present only as a singlespecimen in our material.Gomphonema parvulum (Kuetz.) V.H. (Fig-ure 1,20). Valve 18,um long by 4.5,um wide;striae 14-15 in 10 ,urn, somewhat finer at ends.This taxon was present in our material as asingle valve. It was shaped as G. parvulum var.micropus but had finer striae.Gomphonema parvulum var. lagenula(Kuetz.? Grun.) Hustedt (Figure 1,21). Valve25 ,urn long by 6 ,urn wide; striae 13-14 in10 ,urn. This taxon differs from the nominateby having knobbed ends . We saw only a singlevalve of this taxon, although it is common inother Hawaiian localities.Gomphonema truncatum Ehr. Valve about29832 /lm long by 9.5 /lm wide; striae radiate11 -12 in 10 /lm at the middle , becoming12':"-1 4 at the basal pole. Only a single speci-men was noted in our Kilauea material.GYROSIGMAGyrosigma cf. acuminatum ' var . gallicaGrun. (Figure 2, 40). Valve 94.5 /lm long by13 /lm wide; striae 30-31 in 10 /lm , undulate atmidvalve . Only a single specimen of this taxonwas present in our Kilauea material. Our spec-imen had finer striae than is usual for thistaxon, but otherwise fit the description well.MELOSIRAMelosira roseana Rabh. (Figure 1,24,25).Valve 11.5 /lm in diameter; striae 14-16 in 10/lm; three prominent punctae present at mid-valve. This taxon was present only as a singlespecimen in our material.NAVICULANavicula contenta f. biceps (Arnott) Grun.(Figure 2, 31). Valve 7-9 /lm long by 2.5-3 /lmwide; striae finer than 30 in 10 /lm, often unre-solved. This taxon was quite common in ourKilauea material; it is common in subaerialhabitats in other parts of Hawaii as well.. Navicula mutica Kuetz. (Figure 2, 28-30).Valve 11 -27 /lm long by 5-7.5 /lm wide; striae16-21 in 10 /lm at the center, becoming some-what finer at the ends . Navicula mutica wascollected as several frustules from the Kilaueavent. Our specimens were quite variable inshape, and the striae were always fine.Navicula muticoides Hust. (Figure 2, 33-34). Valve 10-15 /lm long by 5.5-7 /lm wide;striae 24-30 in 10 /lm . This species was pre-sent as several specimens in the Kilauea mate-rial. It is determined by the deflected proximalraphe ends and the near marginal isolatedpunctum.Navicula radiosa var. parva Wallace (Figure2,27). Valve 25 /lm long by 4.5 /lm wide; striaeradiate 15-16 in 10 /lm . Only a single spec-PACIFIC SCIENCE, Volume 39, July 1985imen of this taxon was noted in our material.Navicula species (Figure 2, 32). Valve 19 /lmlong by 3.5 /lm wide; striae unresolved. Thistaxon was represented by 4 or 5 valves in ourmaterial.NITZSCHIANit zschia frustulum var. subsalina Hust.(Figure 2, 35). Valve 10 /lm long by 2 /lm wide;striae 28 in 10 /lm; fibulae 14-16 in 10 /lm. Wesaw only a single specimen of this Nitzschia inthe Kilauea material. It is characterized by itsfine striae and fine, equidistant fibulae .Nitzschia minutula Grun. (Figure 2, 42).Valve 23.5-26 /lm long by 3 /lm wide; striae30-32 in 10 /lm; fibulae equidistant, 13 in 10/tm'llear valve center, 15 in 10 /lm near valveends. This species was present as three valvesin our material. We have placed it into N.minutula on the basis of the equidistant fibulaeand fine striation.Nitzschia palea (Kuetz.) W. Sm. (Figure 2,38). Valve about 24 /lm long by 5.5 /lm wide;striae unresolved; fibulae 12-13 in 10/lm. Nitz-schia palea was represented by two brokenvalves in the Kilauea material.Nitzschia pellucida f. minores Cleve-Euler(Figure 2, 39). Valve 21 /lm long by 7 /lm wide;striae 32-34 in 10 /lm; fibulae 19-20 in 10 /lm.This Nit zschia was present only as a singlespecimen in the Kilauea material.Nit zschia species (Figure 2, 37) . Valvelinear lanceolate, with subcapitate apices,74-86 /lm long by 4-5 /lm wide; striae dis-tinctly punctate, forming vertical and hori-zontal rows, 22-24 in 10 /lm; keel submar-ginal ; fibulae unevenly spaced near valvecenter, 7-8 in 10 /lm; central fibula large,slightly displaced toward valve center. Wehave seen this taxon only at the Kilauea siteduring our Hawaiian studies. It is unusual dueto its punctate striae, which are aligned toform horizontal and vertical striae. We havepreviously reported (Fungladda, Kaczmar-ska, and Rushforth 1983) that this taxon issimilar in some respects to several of the lan-ceolate Nit zschia species, including N. .inter-media, N. linearis, and N. subtilis, but differsfrom each of these in certain respects. Ouri ·3143424127F IG URE 2. 27, Na vicula radiosa var. par va; 28- 30, Navi cula mutica; 31, Na vicula contenta f. biceps; 82, Navi culaspecies; 33, 34, Navicula muticoides; 35, Nitzschia frustulum var. subsa/ina; 36, Syn edra ulna, x 1000; 37, Ni tzschiaspecies; 38, N itzschia palea; 39, Ni tzschia pe//ucida f. min ores; 40, Gyrosigma cf. acuminat um var. ga//ica; 41, Synedrafascicu lata var. truncata; 42, Nitzschia minutula ; 43, Pinnularia borealis var. rectangularis; 44, Pinnularia termit ina; 45,Rhopalodia gibberula var. vanheurckii . All figures are x 2000 unless otherwise noted.300specimens are within the reported range ofvariability of N . gandersheimiensis (Lange-Bertalot and Simonsen 1978), although thearrangement of striae and central fibulaein ours deviate from that taxon. Nitzschiamiramarensis Hagelstein (1938: 398) appearsto be very similar to our specimens. Ours differby being smaller and having somewhat finerstriae than that taxon.PINNULARIAPinnularia borealis var. rectangularis Carl-son (Figure 2, 43). Valve 22-36 Jim long by5.5-8.5 Jim wide; striae 4-6 in 10Jim. Pinnula-ria borealis var . rectangularis was present inmoderate numbers in our Kilauea materialbut was less abundant than P. termitina.Pinnularia leptosoma (Grun.) Cl. (Figure I ,18). Valve 21-22 Jim long by 4 Jim wide; striae20 in 10 Jim, becoming somewhat finer nearends . This taxon has fine striae for a Pinnu -laria and may be separated from Calon eisbacillum, which is also present in the Hawaiianflora , on the basis of the striae being coarserand tending to become more convergent inthe former. This taxon was quite rare in ourmaterial.Pinnularia termitina (Ehr.) Patrick (Figure2,44). Valve 31-57 Jim long by 4.5-5.5 Jimwide; striae 11-15 in 10 Jim. Pinnularia term i-tina was quite abundant in our Kilauea mate-rial, comprising about 6.7% of the population.RHOPALODIARhopalodia gibberula var. vanheurckii O.MueIl. (Figure 2, 45) . Valve about 35 Jim longby 7.5 Jim wide; costae 4-5 in 10 Jim, som e-what finer near ends ; striae 19-20 in 10 Jim.This taxon was present at the Kilauea site as asingle specimen.SYNEDRASyn edra fasciculata var. trun cata (Greg.)Patrick (Figure 2, 41). Valve 39-42 Jim longby 4.5-5 Jim wide; striae 13-14 in 10 Jim, be-coming somewhat finer near ends . We ob-PACIFIC SCIENCE, Volume 39, Ju ly 1985served this taxon as two valves in our material.Synedra ulna (Nitz.) Ehr. (Figure 2, 36).Valve 101- 120Jim long by 7.5- 8.5 Jim wide;striae 9-11 in 10Jim. Synedra ulna was seenin our material as one intact and three brokenvalves.LITERATURE CITEDCLARK, R. L., and S. R . RUSHFORTH. In press .The algae of selected han ging gardens fromthe Lake Powell region , Utah. Great BasinNaturalist.FUNGLADDA, N ., 1. KACZMARSKA, and S. R .RUSHFORTH. 1983. A contribution to thefreshwater diatom flora of the HawaiianIslands. Bibl. Diatom. 2(2): 1-103.HAGELSTEIN, R. 1938. The Diatomaceae ofPuerto Rico arid the Virgin Islands. Pages313-450 in Scientific survey of Puerto Ricoand the Virgin Islands. Vol. 3. New YorkAcademy of Science, New York.HUSTEDT, F . 1930-1 966. Die KieselalgenDeutschlands, Oesterreichs und derSchweiz. in L. Rabenhorst, ed. Kryptoga-men Flora von Deutschland, Oesterreichund der Schweiz. Vol. 7, P. I (1930); P. 2(1959); P. 3 (1966). Reprint, Johnson Re-print Corp., New York.LANGE-BERTALOT, H. , and R. SIMONSEN. 1978.A taxonomic revision of the Nitzschiaelanceolatae Grunow. Pt. 2. European andrelated extra-European freshwater andbrackish water taxa. BaciIlaria I : 11-11 0.PATRICK, R. 1977. Ecology of freshwaterdiatoms and diatom communities . Pages284-322 in D . Werner, ed. The bio logy ofdiatoms. Blackwells, Oxford.PATIEN, B. C. 1962. Species diversity in netph ytopl ankton of Raritan Bay. J . Mar.Res. 20 :57-75.RUSHFORTH, S. R. , 1. KACZMARSKA, and J , R .JOHANSEN. 1984. The subaerial diatom floraof Thurston lava tube, Hawaii . Bacillaria7 : 135- 157.RUSHFORTH, S. R., L. L. ST. CLAIR, T. A.LESLIE, K. H. THORNE, and D . A. ANDERSON,1976. The algae of two hanging gardensfrom southeastern Utah. Nova Hedwigi a27:23 1-323.i ,l' , , '-i'B, ,. , P ,' t: V:.: f ~'w:etiee#m"Diatom Flora of a Steam Vent-McMILLAN AND R USH FORTH 301SHANNON, G. E., and W . W EAVER. 1949. Themathematical theory of communication .University of Illinois Press, Urbana.ST. CLAIR, L. L., and S. R . RUSH FORTH. 1977.The diatom flora of Goshen warm springs ,ponds and wet mead ows , Goshen, Utah .Nova Hed wigia 28 : 353- 425.WAHRER, R . J . 1981. Comparative valvemorphology of selected species of EunotiaEhr. (Bacillari ophyceae). Ph.D. Thesis,Texas A&M University, College Station.

The Diatom Flora of a Steam Vent of Kilauea Crater, Island of Hawaii

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The Diatom Flora of a Steam Vent of Kilauea Crater, Island of Hawaii

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