Abstract

The present study is a first characterization of benthic communities associated with the intensively-exploited sea urchin Loxechinus albus in Northwest Patagonia. Using video-transects, we sampled 22 L. albus beds, distributed among five sampling zones, defined by oceanographic criteria and geographic proximity. Species composition was characterized and compared among zones using Permutational analysis of variance (PERMANOVA), followed by multiple comparisons and distance-based redundancy analysis. In addition, we used species archetype models (SAMs) to identify and estimate the probability of presence of different groups of species (archetypes) that respond similarly to environmental variables. Most zones were characterized by one or two highly abundant taxa, with Corynactis, Arbacia dufresnii, Antholoba achates, and Pseudechinus magellanicus being the most abundant. Sampling zones were shown to have significant effects upon species composition, reflected in significant differences among most zones. The most informative SAM identified three archetypes and considered substrate effects, linear and quadratic effects of temperature and chlorophyll-a concentration, and linear effects of salinity. Probability of Archetype 1 decreased with latitude, particularly south of the Desertores Sill Constriction. Probability for Archetype 2 seemed related to both latitude and salinity. Archetype 3 presented low probabilities across the whole study area. Considering all results, we propose dividing the study area into three main zones: (1) an estuarine area north from Desertores Sill Constriction, (2) an oceanic area corresponding to the Gulf of Corcovado, the Outer Chonos Archipelago and northern sections of the Inner Chonos Archipelago, and (3) an estuarine area located at the southern section of the Inner Chonos Archipelago.