MEES Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/19655

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Physiological responses of Acartia and Eurytemora spp. to changes in the nitrogen:phosphorus quality of their food
(2014) Bentley, Katherine Marie; Glibert, Patricia; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This study addressed how copepods respond to varying nutrient content in their prey. Copepod physiological responses were measured along a gradient of prey nitrogen:phosphorus (N:P) ratios created by altering the P content in diatom prey grown at a constant rate. Acartia tonsa, a broadcast spawner, and Eurytemora carolleeae, a brood spawner, increased excretion of P as prey N:P declined (i.e. P increased). E. carolleeae had higher somatic tissue nutrient content, while A. tonsa had higher egg nutrient content overall and higher P in eggs as N:P decreased. E. carolleeae egg production was greatest when eating high N:P prey while A. tonsa showed the opposite. Egg viability declined at high N:P for both copepods, yet A. tonsa viability was always greater than E. carolleeae viability. Both copepods responded physiologically to food of varying quality, yet regulated their homeostasis differently. Prey nutrient content may be significant in the environmental selection of different copepods.
RESPONSES OF THE COPEPOD ACARTIA TONSA TO HYPOXIA IN CHESAPEAKE BAY
(2015) Barba, Allison Patricia; Roman, Michael R; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Chesapeake Bay experiences seasonal hypoxia each year and while studies have been done investigating how the copepod Acartia tonsa responds to hypoxia, few studies have focused on a comprehensive understanding of how its behavior and fitness are affected by low oxygen. The abundance, distribution, fitness and diel vertical migration patterns of A. tonsa were measured on series of six cruises in 2011 and 2012 in spring, summer and fall. I found that copepod abundance, distribution and vertical migration were significantly affected when hypoxic waters occurred below the pycnocline. I also found that males were less impacted by hypoxia than females, with a greater decrease in female abundance and vertical migration when there were hypoxic bottom waters.