Sewage effects at the end of the world: impact on the intertidal macrobenthic community in the Beagle Channel

A first baseline assessment of low intertidal macrobenthic communities in the Beagle Channel (Ushuaia, Argentina) was conducted, focusing on the ecological effects of urban sewage discharge. A hierarchical spatial and replicate sampling design was implemented across 300 quadrats in both reference and sewage-impacted localities. Over 70,000 individuals representing 60 species were recorded. Higher species richness was observed in reference zones. Although a core group of species was shared across the environmental gradient, sensitive bioindicator taxa such as brittle stars and chitons were found primarily in reference localities, while pollution-tolerant species such as Capitella capitata and Nematoda were dominant in impacted ones. Beta diversity analyses indicated that species replacement prevailed in impacted localities, whereas species richness contributed more significantly in reference localities. Some localities in both conditions were identified as having a significant local contribution to overall beta diversity. Up to 60% of the variation in community structure was explained by environmental variables, notably total dissolved solids and fecal coliform concentrations. The results reveal spatially localized but ecologically significant alterations attributed to sewage discharge. Improved wastewater management in Ushuaia is recommended, along with long-term monitoring of benthic communities as a proxy for ecosystem health in this unique sub-Antarctic coastal environment.