Diatoms on coral reefs and in tropical marine lakes

Abstract

Coral reef communities as diatom habitats Coral reefs, well known for their tremendous biodiversity and beauty (Veron, 2000; Spalding et al ., 2001), are the most complex ecosystems in the sea, and are often compared to rainforests, both because of the large numbers of organisms (estimates in both cases based on larger organisms and extrapolated wildly to small animals and microorganisms!) and because corals, like rainforest trees, create the structure and habitat for the wealth of other organisms. Coral reefs are formed by a highly successful yet environmentally sensitive symbiotic association between animals (cnidarians; scleractinian corals) and protists (dinoflagellate algae; zooxanthellae in the genus Symbiodinium ). The term coral is generally used to denote the holobiont, i.e. both partners in the symbiosis. On a healthy coral reef, macroalgae are generally sparse and coral cover is high, but the balance can be tipped to communities dominated by fleshy algae by nutrient inputs that promote algal growth in the otherwise oligotrophic waters, or by reduction of normally high grazing pressure (Littler & Littler, 1984). Coral reefs are vital resources for millions of humans in tropical, especially developing countries, who depend on them for fisheries (Cesar, 2000; Sadovy, 2005; Vincent, 2006), tourism income (Brander et al ., 2007), storm protection (UNEP-WCMC, 2006), and sometimes structural materials (Berg et al ., 1998; Mallik, 1999). Biodiversity of coral reefs is also recognized for its pharmacological potential (Adey, 2000).