Differential tolerance capacity of intertidal organisms (sponge and zoanthid) to the environmental stresses: Preliminary findings from a rockpool transplantation experiment

Abstract

Marine intertidal organisms face extreme environmental fluctuations due to tidal cycles. To investigate the impact of environmental changes (high salinity, sea surface temperature, and anthropogenic pollution) on the health of the coastal area, we selected the dominant intertidal organisms: sponge (Cinachyrella cf. cavernosa) and zoanthid (Zoanthus sansibaricus) as our model system from a rocky beach Anjuna, Goa, India. Sponges and zoanthids were transplanted from their natural habitat (mid-tide pools) to new habitat (upper-tide pools). The study was carried out for 15 days when these pools experienced flushing during the first and last 5 days (high tide was >1.8 m) and no flushing during the middle 5 days (high tide was <1.8 m). The indices of physiological response (such as in budding activity and oscular openings) in the sponge and (chlorophyll estimation and symbiotic zooxanthellae count) in zoanthid were estimated at natural and transplanted habitats. Upper intertidal pools experienced intense temperature (29.9-36.15�C), salinity (35.03-46.7 ppt) and variability in dissolved oxygen (3.2-9.5 mg/l). The transplanted sponge did show the closure of oscula (90.62%) and reduction in buds (40-94.9%), but they could survive beyond 15 days. While transplanted zoanthid showed bleaching and did not survive beyond 72 h due to reduced chlorophyll content (up to 44.21%) and zooxanthellae count (34.54%). Our results depicted the differential tolerance capacity of sessile organisms like sponge and zoanthid to environmental changes, which govern the vertical zonation in the rocky intertidal region. It highlights the role of these sessile invertebrates as early indicators of environmental changes.