Spatial and depth trends for Octocorallia morpho-functional groups on the Gulf of California associated with local oceanopraphic data

Abstract

Octocorals are the most abundant Class on temperate and tropical reefs, however, not much information about their ecological role or distribution trends is known on the Gulf of California (GC). Changes in local oceanographic conditions due to climate change could affect the octocorals community, disrupting the ecosystem. Therefore, three sites have been sampled in the Central and Southern region of the GC, to define the distribution trends for Octocorallia Class. Five morpho-functional groups have been described (G1 “Mesh fan”, G2 “thick ramification”, G3 “Messy fan”, G4 “Bushy shape” & G5 “Big Ones”) to understand the ecological role of the octocorals. Latitudinal and bathymetrical patterns have been found and statistical analysed to perform correlations upon environmental and oceanographic features (Bathymetry, Night Sea Surface Temperature (NSST), Chlorophyll-a (CHL.A), nutrients (NO32-, PO43-), Particulate Organic Carbon (POC), Surface Current Velocity (SCV) and Diffuse Attenuation Coefficient (KD-490)). Results show a south-east (SE) tendency for the oceanographic variables, becoming more tropical and oligotrophic through the mouth of the gulf. These conditions variations seem to determine the distribution of the groups, finding two general inclinations. G1 and G4 morpho-functional groups prefer shallow, warm oligotrophic waters, while the remaining three prefer deep, colder and eutrophic waters. Oligotrophic waters presented maximum values of abundance density, however, less diversity is found in more tropical conditions. We argue about the possible adaptations of the groups to follow this tendency and their ecological function.