Sarah Gasko, University of Michigan

Class Year:

2024

Mentor:

Judy O'Neil, Ph.D.

Abstract:

Chesapeake Bay has a history of varying nutrient fluxes that lead to periods of eutrophication. During these times of nutrient overabundance, phytoplankton blooms can have negative consequences on bay health including hypoxia in bottom waters, which affect species up the food chain. Mesozooplankton (>200µm), mainly copepods, are consumers of phytoplankton, making them vital species for trophic energy transfer. While various research has focused on how phytoplankton are affected spatially and temporally by environmental conditions, less is understood about how copepod grazing may be impacted by such influences across time and space. Thus, this study sought to determine if there is a significant relationship between salinity or nutrient levels, which vary throughout the bay, and rate of mesozooplankton grazing. Water samples were collected from six sites across Chesapeake Bay’s main stem, and the >200µm size fraction were filtered out. Phytoplankton biomass was measured after an incubation period between these treatment groups and controls where mesozooplankton were not removed. Results reflect a shifting influence of salinity on mesozooplankton grazing between June and July. Furthermore, NOx concentration was found to be positively correlated with grazing, whereas ammonium and phosphate levels showed no significant relationship with grazing. While grazing data from June and July broaden the current understanding of interactions between abiotic environmental factors and biotic species, further research should observe higher trophic species alongside shifts in other environmental factors over a longer time period with larger sample sizes. 

Location:

Horn Point Laboratory