Megafauna benthic of outer margins of the continental shelf of Yucatan Peninsula

Megabenthic community on the continental shelf of the Yucatan Peninsula was evaluated during November 2015 and April 2016. Samples were collected at sixteen sites with a trawl net within a depth range of 50 to 200 m, in three sectors (west, central and east) relative to the Yucatan Current. Total abundance was 228,545 Ind km−2 which represent a total biomass value of 456.43 kg AFDW km−2. Main abundant taxa were crustaceans and mollusks (94,974 Ind km−2 and 88,891 Ind km−2, respectively), while crustaceans and poriferans showed highest biomass values (352.5 kg AFDW km−2 and 35 kg AFDW km−2, respectively). Achelous spinicarpus (53,938 Ind km−2) and Turritela radula (21,577 Ind km−2) were the most abundant species, meanwhile highest contribution to the community biomass was provided by P. argus (146 kg AFDW km−2) and A. spinicarpus (45 kg AFDW km−2). Abundance and biomass values were higher in the west sector than the others. Values for H' fluctuated from 0.55 to 3.34, with the highest values in the west sector. Evenness was high at almost all sampling sites. Multisite beta diversity had values of Betasor>0.85, Betasim>0.78 and Betanest<0.09. Abundance, biomass, and diversity values were attributed to the presence of sessile organisms which increase the natural habitat architectural heterogeneity provided by the karstic bottom of the Yucatan Peninsula, favoring the presence of rare species that contribute to the multisite beta values of the study area that result of a turnover without species loss or a nested effect.