Benthic macroalgae of the Arabian Sea 1 Benthic macroalgae of the ...
Benthic macroalgae of the Arabian Sea 1 Benthic macroalgae of the ...
Benthic macroalgae of the Arabian Sea 1 Benthic macroalgae of the ...
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<strong>Benthic</strong> <strong>macroalgae</strong> <strong>of</strong> <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong>Algal assemblages <strong>of</strong> Masirah Island (Oman) and <strong>the</strong> Socotra Archipelago (Yemen),a case studyTom SchilsResearch Group Phycology, Department <strong>of</strong> Biology, Ghent University, K. L. Ledeganckstraat35, 9000 Ghent, Belgiumtom.schils@rug.ac.beFig. 1. Stoechospermum polypodioides (Lamouroux) J. Agardh, a common brown alga <strong>of</strong><strong>the</strong> coastal waters around Masirah Island. Scale bar = 1 cmSubsequent to <strong>the</strong> Oman 99 Mission (November 1999), a field trip to <strong>the</strong> Socotra Archipelago(Yemen; March - May 2000) was organised to compare <strong>the</strong> algal assemblages <strong>of</strong> Masirah Islandwith o<strong>the</strong>r upwelling areas in <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong>. During both campaigns, collection efforts werefocused on <strong>the</strong> diverse and species rich sublittoral algal vegetations. The biotic and abioticparameters <strong>of</strong> <strong>the</strong> sampling sites were documented, <strong>the</strong> observed seaweeds registered and <strong>the</strong>majority <strong>of</strong> <strong>the</strong> algae preserved on herbarium sheets (Fig. 1), as formalin specimens or silica gelsamples (molecular analysis). In addition to qualitative sampling, vegetation relevés (quadrats<strong>of</strong> 0.25 m 2 ) were used to determine <strong>the</strong> ecology <strong>of</strong> <strong>the</strong> algal vegetations around Socotra. Thevegetation parameters and <strong>the</strong> environmental variables were noted in situ (Schils 2000) andcompleted with biomass data in <strong>the</strong> field laboratory. The latter method (scraping-<strong>of</strong>f phytomass)also showed its use for qualitative sampling, as it revealed <strong>the</strong> species richness <strong>of</strong> small algae inunderstory layers.<strong>Benthic</strong> <strong>macroalgae</strong> <strong>of</strong> <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong> 1
Databases (MS Access 2000) were designed to store <strong>the</strong> sample data <strong>of</strong> <strong>the</strong> different field trips.A first database, “Phycobase”, contains information on <strong>the</strong> (i) collected specimens; (ii) acompilation <strong>of</strong> all macroalgal genera classified by <strong>the</strong>ir latest systematic position; (iii) tablesand queries <strong>of</strong> all documented algal taxa <strong>of</strong> <strong>the</strong> nor<strong>the</strong>rn Indian Ocean. This databaseautomatically detects new records <strong>of</strong> species and genera, executes exhaustive biogeographicalcomparisons, classifies specimens, etc. Additionally, <strong>the</strong> records (specimens) contain hyperlinksto html pages, which include descriptions and comparisons <strong>of</strong> <strong>the</strong> specimens with literaturereports <strong>of</strong> related taxa. The html documents are continuously updated and <strong>the</strong>ir structure issystematically arranged with links to (i) higher and lower taxonomic levels, (ii) macroscopicand microscopic images and (iii) personal comments <strong>of</strong> specialists. Currently 1721 specimensare stored in Phycobase, 587 from Masirah Island and 1134 from <strong>the</strong> Socotra Archipelago. S<strong>of</strong>ar, about 30% <strong>of</strong> <strong>the</strong> specimens are identified to species level and 50% to genus level.Preliminary checklists for both islands in <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong> were included in project reports(Schils 1999, 2000). At present, <strong>the</strong> research efforts aim at a systematic study <strong>of</strong> coherenttaxonomical groups, mainly belonging to <strong>the</strong> Rhodophyta.The second database, “SMM relevés”, contains <strong>the</strong> vegetation relevés. The database includesfor each sampling station <strong>the</strong> site description, <strong>the</strong> environmental variables and <strong>the</strong> relevés as subforms. This allows orderly and sound adjustments (refined identifications). All data arecombined in 2 tables, permitting analyses by means <strong>of</strong> cross tables (statistics, extraction <strong>of</strong>matrices for multivariate analyses, etc.).A prospective analysis <strong>of</strong> <strong>the</strong> vegetation relevés around <strong>the</strong> Socotra Archipelago (Tukey HSDtest; Schils 2000) shows that <strong>the</strong> sample sites <strong>of</strong> upwelling regions are characterised by asignificantly higher species richness (p < 0.5) compared to <strong>the</strong> o<strong>the</strong>r coastal areas. A similarpattern is observed for Masirah Island, where <strong>the</strong> algal communities <strong>of</strong> <strong>the</strong> east coast areanalogous to those <strong>of</strong> <strong>the</strong> south coast <strong>of</strong> Socotra Island. The sublittoral marine macr<strong>of</strong>lora <strong>of</strong> <strong>the</strong>upwelling areas is characterised by <strong>the</strong> seasonal presence <strong>of</strong> gelatinous red algae(Dumontiaceae, Naccariaceae, Nemastomataceae and Schizymeniaceae). Similar vegetationsare found in distant regions in <strong>the</strong> Indian Ocean and <strong>the</strong> Pacific, which are subject to a coldwater regime with considerable current dynamics (e.g. Hawaii, Abbott pers. comm.). Millar &Kraft (1984) state that <strong>the</strong>se ra<strong>the</strong>r “primitive” algae could persist over a long period in time in<strong>the</strong>se more or less constant sublittoral habitats. In this context, it is interesting to analyse <strong>the</strong>actual distribution patterns <strong>of</strong> <strong>the</strong>se algae within <strong>the</strong> Indian Ocean and <strong>the</strong> Pacific.The first taxonomical topic covered <strong>the</strong> first observations <strong>of</strong> Naccariaceae taxa for <strong>the</strong> IndianOcean. Representatives <strong>of</strong> <strong>the</strong> genus Reticulocaulis (previously monospecific and endemic toHawaii) were collected in <strong>the</strong> coastal waters <strong>of</strong> Masirah and Socotra Island. Biogeographicaland taxonomical aspects <strong>of</strong> <strong>the</strong>se algae were studied. The Omani specimens were compared indetail to formalin samples <strong>of</strong> <strong>the</strong> type species and <strong>the</strong> developmental stages (especially those <strong>of</strong><strong>the</strong> female gametophytes) were discussed. The collection <strong>of</strong> R. mucosissimus <strong>of</strong>f MasirahIsland, revealed a disjunct distribution pattern <strong>of</strong> <strong>the</strong> type species. The Socotran specimenspossessed <strong>the</strong> generic characteristics but differed from R. mucosissimus, resulting in <strong>the</strong>description <strong>of</strong> a new species, R. obpyriformis (Schils et al. submitted). R. obpyriformis showsadditional carposporophyte characteristics that confirm previously stated similarities (Abbott1985, 1999) with o<strong>the</strong>r “primitive” Florideophyceae, particularly Acrosymphyton. Thephylogenetic position <strong>of</strong> <strong>the</strong> genus and <strong>the</strong> family remain unclear. Pending molecular studies onReticulocaulis and additional Atractophora and Naccaria samples (<strong>the</strong> o<strong>the</strong>r Naccariaceaegenera) should clarify <strong>the</strong>ir phylogeny and biogeography.<strong>Benthic</strong> <strong>macroalgae</strong> <strong>of</strong> <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong> 2
The gelatinous red algae belonging to <strong>the</strong> families Dumontiaceae, Nemastomataceae andSchizymeniaceae were analysed in a subsequent study. The taxa <strong>of</strong> <strong>the</strong>se families are relativelywell investigated in o<strong>the</strong>r parts <strong>of</strong> <strong>the</strong> world, but information on <strong>the</strong>ir presence and distributionin <strong>the</strong> Indian Ocean is lacking. The studied species assume a great affinity with <strong>the</strong> gelatinousred algal flora <strong>of</strong> Australia and <strong>the</strong> Great Barrier Reef in particular. However, <strong>the</strong> includednew records from o<strong>the</strong>r Indian Ocean localities show that many gelatinous red algae mighthave a wider distribution range. The observations <strong>of</strong> Hommersand (1986) support <strong>the</strong> latterpoint <strong>of</strong> view, he states that <strong>the</strong>se ra<strong>the</strong>r “primitive” algae are widely distributed in <strong>the</strong> tropicsand in regions that bordered <strong>the</strong> original Tethyan Ocean. This implies that previouslymentioned biogeographical links (Børgesen 1934; Wynne 2000) with distant areas (Australia,Japan and South Africa) cannot be confirmed using representatives <strong>of</strong> <strong>the</strong>se families incomparative studies. The floristic similarities would be mere results <strong>of</strong> comparing distant,well-investigated areas within regions <strong>of</strong> an inadequately known marine flora. In investigating<strong>the</strong>se algae, we focused on <strong>the</strong> post-fertilization events that typify <strong>the</strong> families and species.New information concerning <strong>the</strong>se critical characters, which have been scarcely observed inpast studies, is included in <strong>the</strong> manuscript (Schils & Coppejans submitted). Additionally, anewly described Platoma species (Fig. 2) constitutes <strong>the</strong> first record <strong>of</strong> this genus for <strong>the</strong>Indian Ocean.Fig. 2. A Platoma sp. nov. from Masirah Island, <strong>the</strong> first record <strong>of</strong> this genus for <strong>the</strong> IndianOcean. Scale bar = 1 cmAt present, a study on <strong>the</strong> Delesseriaceae (Rhodophyta) <strong>of</strong> <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong> is in process.Representatives <strong>of</strong> this family are relatively well documented for adjacent areas in <strong>the</strong> IndianOcean and <strong>the</strong>se taxa are consequently a good tool for biogeographical analyses. Themorphology, anatomy and reproductive characteristics <strong>of</strong> ten species are being studied,including taxa with disjunct distribution patterns (e.g. Zellera sp.) and first records since <strong>the</strong>iroriginal description (e.g. Chauviniella jadinii). Ano<strong>the</strong>r family <strong>of</strong> <strong>the</strong> Ceramiales, <strong>the</strong>Rhodomelaceae, will be examined in <strong>the</strong> framework <strong>of</strong> an MSc <strong>the</strong>sis (2001-2002).<strong>Benthic</strong> <strong>macroalgae</strong> <strong>of</strong> <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong> 3
O<strong>the</strong>r algal groups that require a thorough examination are <strong>the</strong> Chlorophyta, <strong>the</strong> Nemaliales and<strong>the</strong> Rhodymeniales. This research will be executed in collaboration with <strong>the</strong> respectivelyspecialists: Frederik Leliaert (Chlorophyta; Ghent University, Belgium) and John Huisman(Nemaliales and Rhodymeniales; Murdoch University, Australia). As <strong>the</strong> phycologicalfieldwork was part <strong>of</strong> a multidisciplinary study, <strong>the</strong> coastal areas around <strong>the</strong> SocotraArchipelago will be analysed for ecological and seasonal patterns using <strong>the</strong> vegetation relevésand remote sensing data (Rebecca Klaus; Warwick University). The final goal is anextrapolation <strong>of</strong> <strong>the</strong>se results to o<strong>the</strong>r upwelling areas in <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong> (e.g. Masirah Island).Previous biogeographical studies <strong>of</strong> <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong> showed floristic affinities with distantareas, e.g. Australia, Japan and South Africa (Børgesen 1934; Wynne 2000). Our preliminaryresults show floristic affinities with <strong>the</strong> East African Coast, <strong>the</strong> Indo-Malayan Region, westernand eastern Australia. These findings fit <strong>the</strong> hypo<strong>the</strong>sis <strong>of</strong> Hommersand (1986), whichdemonstrates that ocean currents during <strong>the</strong> Miocene were determinant for <strong>the</strong> presentdistribution patterns <strong>of</strong> <strong>the</strong> marine macr<strong>of</strong>lora. Prospective research using Phycobase shouldfacilitate an elaborate biogeographical analysis <strong>of</strong> this stepping stone region in <strong>the</strong> IndianOcean.ReferencesAbbott I. A. 1985. Vegetative and reproductive morphology in Reticulocaulis gen. nov. andNaccaria hawaiiana sp. nov. (Rhodophyta, Naccariaceae). Journal <strong>of</strong> Phycology 21: 554-561.Abbott I. A. 1999. Marine red algae <strong>of</strong> <strong>the</strong> Hawaiian Islands. Bishop Museum Press, Honolulu,Hawai’i. 477 pp.Børgesen F. 1934. Some marine algae from <strong>the</strong> nor<strong>the</strong>rn part <strong>of</strong> <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong> with remarkson <strong>the</strong>ir geographical distribution. Kongelige Danske Videnskabernes Selskab, BiologiskeMeddelelser 11: 72 pp.Hommersand M. H. 1986. The biogeography <strong>of</strong> <strong>the</strong> South African marine red algae: a model.Botanica Marina 29: 257-270.Millar A. J. K. & Kraft G. T.. 1984. The red algal genus Acrosymphyton (Dumontiaceae,Cryptonemiales) in Australia. Phycologia 23: 135-145.Schils T. 1999. Macroalgae. In: (Planes S. & Galzin R. eds) Preliminary Report ScientificMission Oman 99, Sultanate <strong>of</strong> Oman, November - December 1999. Ardoukoba, Paris. 22-23, 64-69 pp.Schils T. 2000. Short Report: Macroalgal assemblages <strong>of</strong> <strong>the</strong> Socotra Archipelago, Yemen. In:(Hariri K. I. & Krupp F. eds) Conservation and Sustainable Use <strong>of</strong> Biodiversity <strong>of</strong> SocotraArchipelago. Marine Habitat, Biodiversity and Fisheries Surveys and management. Report<strong>of</strong> Phase IV. Senckenberg Research Institute, Germany. 12 pp. accepted.Schils T. & Coppejans E. Gelatinous red algae <strong>of</strong> <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong>, including Platomabibendiforme sp. nov. (Gigartinales, Rhodophyta). submitted.Schils T., De Clerck O. & Coppejans E. Reticulocaulis mucosissimus and R. obpyriformis sp.nov., <strong>the</strong> first Naccariaceae (Rhodophyta) records for <strong>the</strong> Indian Ocean. submitted.Wynne M. J. 2000. Fur<strong>the</strong>r connections between <strong>the</strong> benthic marine algal floras <strong>of</strong> <strong>the</strong> nor<strong>the</strong>rn<strong>Arabian</strong> <strong>Sea</strong> and Japan. Phycological Research 48: 211-220.<strong>Benthic</strong> <strong>macroalgae</strong> <strong>of</strong> <strong>the</strong> <strong>Arabian</strong> <strong>Sea</strong> 4