Interspecies and spatial diversity in the symbiotic zooxanthellae density in corals from northern South China Sea and its relationship to coral reef bleaching

Coral reef bleaching is usually characterized by expulsion of symbiotic zooxanthellae, loss of zooxanthellae pigmentation, or both. We collected 128 samples comprising 39 species of 21 genera of reef-building corals from Luhuitou and Xiaodonghai in Sanya of Hainan Island and Daya Bay of Guangdong Province, respectively, and analyzed the symbiotic zooxanthellae population density. The results show that: (1) the symbiotic zooxanthella density varies from 0.67x10(6) to 8.48x10(6) cell/cm(2), displaying significant interspecies variability, with branch corals usually having relatively less zooxanthellae (ranging from 0.67x10(6) to 2.47x10(6) cell/cm(2)) than massive species (from 1.0x10(6) to 8.48x10(6) cell/cm(2)); (2) corals inhabiting within 4 m water depth have higher levels of symbiotic zooxanthellae than those living at the bottom (similar to 7 m depth) of the reef area; (3) there is no discernable difference in the zooxanthellae density between corals from relatively high latitude Daya Bay (similar to 22 degrees N) and those from relatively low latitude Sanya (similar to 18 degrees N) at comparable sea surface temperatures (SST); (4) in partially- bleached corals, the density of zooxanthellae shows the following order: healthy-looking part> semi-bleached part > bleached part. Based on the above results, we suggest that (1) the zooxanthellae density difference between branching and massive coral species is the main cause that branching corals are more vulnerable to bleaching than massive corals. For example, symbiotic zooxanthellae levels are low in branching Acropora and Pocillopora corals and thus these corals are more susceptible to bleaching and mortality; (2) symbiotic zooxanthellae density can also be affected by environmental conditions, such as sediment loads, diving-related turbidity, and aquaculture-related nitrate and phosphate input, and their increase may reduce symbiotic zooxanthellae density in corals

The Coral Trait Database, a curated database of trait information for coral species from the global oceans.

Trait-based approaches advance ecological and evolutionary research because traits provide a strong link to an organism's function and fitness. Trait-based research might lead to a deeper understanding of the functions of, and services provided by, ecosystems, thereby improving management, which is vital in the current era of rapid environmental change. Coral reef scientists have long collected trait data for corals; however, these are difficult to access and often under-utilized in addressing large-scale questions. We present the Coral Trait Database initiative that aims to bring together physiological, morphological, ecological, phylogenetic and biogeographic trait information into a single repository. The database houses species- and individual-level data from published field and experimental studies alongside contextual data that provide important framing for analyses. In this data descriptor, we release data for 56 traits for 1547 species, and present a collaborative platform on which other trait data are being actively federated. Our overall goal is for the Coral Trait Database to become an open-source, community-led data clearinghouse that accelerates coral reef research