Detecting Anthropogenic Stress in an Ecosystem: 3. Mesoscale Variability and Biotic Indices

Abstract

Previous work in the Ria Formosa Lagoon has revealed that it is possible to use macrofauna community structure as an indicator of contamination effects. Communities at sites adjacent to sewage outfalls indicated contamination but no pollution gradients were observed. In this study, macrofauna within a sub-section of the earlier work were investigated to determine the extent of mesoscale (10-100 m) variability and new indices of biological community structure. The results were evaluated using univariate (Marine Biotic Index; BI) and multivariate statistical methods (PCA). The computer program Barrier (usually used with genetic data) was also applied to detect "barriers" between spatially referenced samples. PCA identified the most significant factor effecting the distribution of the organisms in the study area to be the mud content of the sediment (% <63 µm). Communities at sandy sites consisted of suspension feeders and detrital browsers, whilst communities at muddy sites were composed mainly of deposit feeders. The second principal component produced a vector characterized by a contamination gradient. The effects of the sewage discharge appeared to be concentrated at the outfall as it had the highest TOC (10.4%) content and was the only site to be characterized by the BI as slightly polluted. With the use of the BI and Barrier two gradients were observed in the transition of sites from an unpolluted to a polluted state. These gradients appeared not to follow the flow of the channel as expected (high % TOC of sites along the channel), and instead extended west and south from the sewage source. In conclusion, weak gradients were observeable; the multiple approaches of BI, PCA and Barrier analyses in concert were able to confirm the sewage dispersion route through the area.

Paradigmatic responses of marine benthic communities to different anthropogenic pressures, using M‐AMBI, within the European Water Framework Directive

“…AMBI has been validated using many different anthropogenic pressures on a world-wide basis (e.g. Borja et al 2003a;Chenery & Mudge 2005;Muxika et al 2005;Muniz et al 2005;Carvalho et al 2006;Quintino et al 2006;Fleischer et al 2007). Following these investigations, AMBI has been found to respond to different pressures, such as hypoxia and eutrophication processes, oil platform discharges, engineering works, dredging and fish aquaculture.…”

Current status of macroinvertebrate methods used for assessing the quality of European marine waters: implementing the Water Framework Directive

“…Borja et al, 2003;Solís-Weiss et al, 2004;Chenery & Mudge, 2005;Muniz et al, 2005;Muxika et al, 2005;Carvalho et al, 2006;Quintino et al, 2006;Fleischer et al, 2007;Cheung et al, 2008). Following these investigations, AMBI has been found to respond to different drivers and pressures, such as: hypoxia and eutrophication processes; oil platform discharges; engineering works; dredging; fish aquaculture; etc.…”

Identifying the Source of Nutrient Contamination in a Lagoon System

“…The distribution of sewage-derived compounds has previously been determined in this area; Mudge and Duce (2005) identified sources, sinks, and pathways of contaminants with lipid biomarkers whilst Hewitt and Mudge (2004), Hopkins and Mudge (2004), and Chenery and Mudge (2005) identified the presence of sewage contaminants with biological indicators. It is possible to separate sewage, marine, and terrestrial inputs with biomarkers, and to determine their relative influence at each site.…”

“…Numerous studies have been undertaken within the Ria Formosa investigating water quality with the aid of biological indicators (Hewitt and Mudge, 2004;Hopkins and Mudge, 2004;Chenery and, Mudge, 2005), lipid analysis (Mudge and Duce, 2005) and oxygen concentrations (Mudge et al 2008); however, there is little information available regarding the biologically important nutrients (Newton and Mudge, 2005). These studies have determined the origin of contaminants and shown that both the Ramalhete Channel and the Esteiro de Maria Nova could be major contributors.…”