2019
Published in 3/8/2020
Cláudio Alexandre Tabaio Brandão Diversity and population dynamics of endolithic coral symbiotic dinoflagellates at Lizard Island (Great Barrier Reef, Australia) Coral reefs worldwide owe their ecological success to the symbiotic relationship established between marine invertebrates and dinoflagellates of the family Symbiodineaceae. Even though these microalgae are primarily renowned by their mutualistic symbioses with corals and other host organisms, they also thrive as free-living cells in the environment and are found in the water column and in the benthos. These environmental populations represent an important pool of potential coral symbionts, but their biology and ecological relevance remain largely unexplored. Previous studies by our research group have shown that in culture the majority of these microalgae are capable of producing small, sand-like carbonate structures that encase the algae as endolithic cells. The discovery of these so-called symbiolites in vitro provided first evidence of an endolithic life cycle strategy of symbiodiniaceans and led our team to search for evidence of this aspect of symbiodiniacean life history in naturally occurring endolithic communities in sediments of the Great Barrier Reef (GBR, Australia). Recent projections show that reefs worldwide will start transitioning from a net-calcifying to a net-dissolving state by 2050 due to ocean acidification. This radical change in reef chemistry is likely to affect the endolithic communities of symbiodiniaceans profoundly, as entering the endolithic niche is based on calcification, but the extent of this effect is currently unknown. In order to understand how these changes may take place, it is imperative to understand the current state of diversity, abundance and population dynamics of these endolithic communities of coral symbiotic algae. Thus, the aim of the present proposal is to assess the absolute abundance and seasonal dynamics of endolithic symbiodiniaceans on the coral reef sediments of Lizard Island. Carrying out the current proposal will provide fundamental new information about symbiodiniacean life history and ecology with far-reaching implications for their role in coral reef ecosystems worldwide.
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