Date of Submission


Document Type


Degree Name

Master of Science in Environmental Science


Biology and Environmental Sciences


Roman Zajac, Ph.D.


Macroalgae, Macrobenthic, Algal Mats, Ecological System, Infaunal Community Structure


Seaweed, Eutrophication


Marine algae, Estuarine eutrophication, New Haven Harbor (Conn.), Marine benthic ecology, Ecosystem health


Seasonal macroalgal mats caused by eutrophication may modify environmental conditions potentially causing negative or positive effects on species depending on their spatial extent and temporal duration. The western portion of New Haven Harbor is experiencing extensive and seasonally abundant drift macroalgae. This thesis focused on examining the effects of macroalgal mats (mostly Ulva spp.) on infaunal community structure in New Haven Harbor, Connecticut. Instances of algal mats occurring at low amounts and for a short period of time can be beneficial to the macrobenthic community, but when algal growth is extensive and persistent, infaunal community structure may suffer reductions in species richness, abundance, and biomass. Sediment and algae samples were collected over the course of a year, from October 2011 to October 2012 at five different study areas based on previous studied extents of algal cover. Algae was present at all sites at some point during the study, with inshore areas extensively covered and more open harbor areas with low coverage. Benthic community characteristics differed and exhibited greater variation among samples where algal mats present versus areas with less or no algal cover. Total abundance and diversity were lower in the presence of algae, and rebounded in the fall. Areas with higher concentrations of algae appeared to have more variable community structure during the peak algal growth time than areas with low or no algae. Complex interactions among the seasonality of algal growth and infaunal community structure appear to at play and continuing to monitor macroalgal blooms and their impacts on the benthic community would provide insight into the ecological health of New Haven Harbor

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