Evaluation of sewage impact on environmental quality and mesozooplankton community in a highly eutrophic estuary of Argentina

DUTTO, M.S.; LÓPEZ ABBATE, MA C.; BIANCALANA F.; BERASATEGUI, A. A.; HOFFMEYER , M.S.

ICES JOURNAL OF MARINE SCIENCE

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2011

1054-3139

Eutrophication by human sewage is an increasing phenomenon along coastal systems. Two sites in the inner zone of the Bahía Blanca Estuary, one receiving regional sewage discharge (CV)and another pristine area (BM) were compared on mesozooplankton abundance, compositionand diversity as well as on environmental quality. Mean comparisons and multivariate analyses(PCA, MDS, BIOENV) were performed in order to detect significant variation in environmentaland biotic variables, and patterns along the spatial scale during summer and winter. CVpresented significantly higher nutrient amount (nitrogen: 12.53 - 37.3 μM; phosphorous: 2.45 -3.48 μM) and lower values of oxygen (5.77 - 5.86 mg l-120 ) and pH (8.08 - 8.32) than BM. Larvae of the detritivorous crab Neohelice granulata showed maximum abundances at CV (p= 0.049) while the typical estuarine copepod Acartia tonsa, was better represented at BM (p= 0.031). Sewage influenced site presented a poorer environmental quality reflected in elevated nutrient content (overcoming natural enrichment), oxygen depletion and some degree of acidification.Sewage based shifts on mesozooplankton were mainly revealed on community composition. Nitrogen and phosphorous nutrients, dissolved oxygen, pH and N. granulata larvae abundances would be useful monitors of human induced changes along this estuary.