Date Thesis Awarded


Access Type

Honors Thesis -- Access Restricted On-Campus Only

Degree Name

Bachelors of Science (BS)


Interdisciplinary Studies


Mark Brush and Iris Anderson

Committee Members

Rachel O'Brien


Estuaries are important sites of carbon cycling; however, the impact of increasingly prevalent harmful algal blooms (HABs) on cycling in these systems remains unclear. To examine the impact of two bloom species, Alexandrium monilatum and Margalefidinium polykrikoides on the quantity and composition of the dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) pools and rates of benthic and pelagic microbial respiration in the lower York River Estuary, VA, a series field samplings and laboratory incubations were performed. The two HAB species greatly increased the size of the DOC and CDOM pools and altered the character of the CDOM pool, causing it to shift towards higher molecular weights and lower levels of aromaticity. DOC released by A. monilatum and M. polykrikoides both stimulated increased respiration by pelagic microbes, but displayed different levels of microbial lability in the DOC produced suggesting species level differences in how HABs affect DOC cycling. HAB produced organic matter did not stimulate increased levels of benthic microbial respiration as measured in sediment core incubations, suggesting that benthic microbial communities are not carbon limited. These findings show that HABs alter the quality and quantity of the DOC pool which in turn affects pelagic microbial respiration. This study also highlighted the need for species level analysis of HABs to be factored in to future estuarine carbon budgets in HAB affected systems.

On-Campus Access Only