Abstract
Marine fish communities are threatened by the interrelated effects of anthropogenic disturbance, habitat modification, and
contamination. This thesis examines the ways in which these stressors affect the ecology of fish communities living in estuaries.
Using a variety of methods I documented large scale impacts among fish communities in heavily modified vs. relatively
unmodified estuaries. First, a comprehensive meta-analysis identified trends and knowledge gaps. Studies on adult fish have
generally shown weakly negative impacts from contamination or largely positive impacts where enriching contaminants are
present. I conducted two field studies of adult fish, the results of which were broadly consistent with the literature. Surveys of
large bentho-pelagic fish using underwater video showed increased abundance of targeted species in heavily modified/nutrient
enriched estuaries. However, beach seine surveys of small bodied species indicated little impact on the beach fish community,
even where high levels of modification and contamination were detected. Instead, beach fish were highly correlated to physicochemical
gradients. This suggests that impacts are highly variable among adult fish, and that both ecological characteristics and
habitat preferences play an important role. Prior to this study nearly no research had been published assessing the impacts of
stressors on marine larvae. Substantial differences in larval communities were detected in heavily modified areas, including
increased abundance and diversity, large shifts in the occurrence of species, and changes to the overall composition of the
community. These trends were highly correlated to contamination of trace metals in the sediment and loss of seagrass cover.
Impacts on larval fish were greatest among fully estuarine taxa and those with benthic eggs. Lastly, a final project indicated
strong impacts from the accumulation of some trace metals (Cu, Zn, and Se) in muscle tissue of Psuedorhombus jenynsii on the
relative body size of the species. In combination these results suggest that stressors have their greatest impact at the early stages
of a fishes’ life cycle and that many positive impacts exist in heavily modified estuaries (e.g. increased abundance/diversity).
Also, my results suggest that ecological characteristics and habitat mediation may play an important role in determining the
relative sensitivity of taxa.