Spatial patterns of macrozoobenthos diversity on sewage-impacted intertidal rocky shores in Central Patagonia, Argentina

The effects of untreated wastewater and shore levels on zoobenthic diversity, species accumulation, and abundance-biomass relationships were studied on intertidal rocky shores of central Patagonia, Argentina. Winter samples (2015) from two sewage-impacted and two reference sites showed that pollution disrupted macrozoobenthic diversity and zonation. A total of 83 taxa were identified, with polychaetes (31 species), mollusks (22), and crustaceans (21) being the most diverse. Impacted sites had greater intra-environmental diversity heterogeneity and higher abundance at the lower midlittoral level, indicating a shift towards lower intertidal levels. Species richness was lower and evenness was higher in the polluted mid-littoral level. ABC curves in the stressed areas showed moderate disturbances with variability across shore zones, while non-polluted rocky shores typically exhibit a higher cumulative faunal biomass than abundance. In impacted areas, chronic habitat changes and disturbances to the mussel matrix by Perumytilus purpuratus are likely responsible for differences in diversity and abundance-biomass relationships.