Low-Tide Exposure of Sponges in a Caribbean Mangrove Community |
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| Authors: | K Rützler |
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| Institution: | Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington DC 20560, USA. |
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| Abstract: | Abstract. Sponges on subtidal red-mangrove prop roots may become exposed to air many times per year during very low tides. Full exposure is stressful and potentially fatal, particularly if occurring in full sun. Large root sponges show distinct species zonation between mean low water and -0.5 m. Haliclona implexiformis and Lissodendoryx isodictyalis are near the top while Scopalina ruetzleri are near the lower end of the range. Temporary experimental desiccation resulted in 100% recovery of all three species after they had been exposed to either sun or shade for up to 2 h. Scopalina is the least resistant and lost over 90% tissue within 3 days after the 4-h and 6-h experiments; the remaining cell mass succumbed to infestation by microbes. Haliclona and Lissodendoryx recovered from as much as 6 h in full sun but lost 85% and 80% of the original tissue volume, respectively. In Lissodendoryx , clusters of larvae developed in the regenerating fragments. Water loss tolerated by the three species is estimated as 66% of wet weight in Haliclona , 54% in Lissodendoryx and 38% in Scopalina . Salinity of interstitial seawater (pore water) extracted from exposed sponges rose from ambient 3.5% to 4.348% after 1 h, to 5.1–5.9% after 6 h. Most endobionts died or left their host during this last phase. Natural vertical zonation in these sponges reflects their resistance to tidal exposure. |
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| Keywords: | Intertidal Porifera red-mangrove roots fouling community temperature-salinity stress desiccation |
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