Abstract
Different hypotheses related to the regional-scale configuration of the Yucatan Continental Shelf (YCS) between the Gulf of Mexico (GoM) and the Caribbean Sea have been proposed. Hypotheses regarding its regional boundaries include: (i) an ecoregional boundary at Catoche Cape, dividing the Western Caribbean and the Southern GoM ecoregions; and (ii) a boundary within the Southern GoM ecoregion at 89°W, separating the West and Mid-Yucatan areas. We tested the hypothesis of no variation in benthic macrofaunal assemblages between regions delimited by the former boundaries using the species and functional traits of soft-bottom macrofauna. We considered that the depth and temporal environmental dynamics might interact with regional variations, generating complex benthic community patterns. The data were collected over five years (2010–2012, 2015–2016) at 86 stations (N = 1, 017 samples, 10–270 m depth), comprising 1,327 species with 45 combinations of functional traits. The variation in species composition and functional trait assemblages were both consistent with the occurrence of three separate regions in the Yucatan Peninsula (West Yucatan, Mid-Yucatan and Western Caribbean). This regional configuration was consistent with changes in assemblage structure and depth zonation as well as temporal variation. Along with spatial and temporal variation, diversity diminished with depth and different regions exhibited contrasting patterns in this regard. Our results suggest that the spatial and temporal variation of soft-bottom macrofauna at YCS demonstrate the complex organization of a carbonate shelf encompassing different regions, which may represent transitional regions between the Caribbean and the GoM.
Highlights
Ecoregions are defined as areas with relatively homogeneous communities that are distinct from adjacent systems (Spalding et al, 2007) and that are affected by environmental conditions, such as currents, upwellings, primary productivity and sediment, among others
Our findings have demonstrated spatial, temporal and depth variations in the distribution of soft-bottom macrofaunal assemblages along the Yucatan Continental Shelf (YCS)
The spatial and temporal variations indicated the complex organization of carbonate shelf communities, which were previously believed to be relatively homogeneous environments, where major spatial and temporal changes can occur
Summary
Ecoregions are defined as areas with relatively homogeneous communities that are distinct from adjacent systems (Spalding et al, 2007) and that are affected by environmental conditions, such as currents, upwellings, primary productivity and sediment, among others. A comprehensive definition of the configuration of marine ecoregions has been proposed by Spalding et al (2007) based on biogeographical data and environmental conditions. A distinct regional configuration has been proposed for the Gulf of Mexico based on chlorophyll-a concentration patterns (Salmerón-García et al, 2011), which may help to redefine ecoregions in smaller areas. There is a broad consensus that the environmental drivers that influence the distribution of benthos change with depth, leading to a gradient effect on the dynamics of the abundance and distribution of benthic assemblages from shallow to deep water (Zajac, 2008; McArthur et al, 2010). Testing different regional variation hypotheses and including depth in spatial analyses of marine benthos may assist in the identification of ecological variation at regional scales
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