THE EFFECTS OF NUTRIENTS AND LIGHT ON MIXOTROPHS IN NARRAGANSETT BAY: A MESOCOSM AND FLOW CYTOMETRY STUDY

Mixotrophy, a form of nutrition involving autotrophy and heterotrophy within one planktonic cell, changes what is known about the transfer of energy to higher trophic levels and carbon cycling on the marine microbial level. However, little is known about mixotrophic activity under environmental stressors including nutrient limitation in situ because the field is relatively new with few methods found to measure data. Understanding the effects of nutrients and light on mixotrophs is important because these organisms affect higher trophic levels and productivity in an environment. Narragansett Bay (NB) is a highly productive estuarine ecosystem with primary production typically limited by nutrients in the summer providing an ideal place to study the effects of nutrients on mixotrophs. This study examined mixotroph abundance in plankton samples collected from NB in tandem with the Narragansett Bay Long Term Plankton Time Series, and determined the effects of nutrient availability and light limitation on mixotrophs by comparing against samples with added nutrients and incubated in low light. Lysotracker Green, a common method to characterize mixotroph abundance, was applied to samples for analysis on a flow cytometer. The study found that mixotroph abundance decreased in low light treatments indicating NB’s mixotrophs may not turn to heterotrophy in time of light stress. Mixotroph abundance did increase when there were lower nutrients available indicating that mixotrophy is an effective form of nourishment in times of nutrient stress. Results from this study provide meaningful data regarding the relationship between mixotrophs and nutrients/light in NB, which has been part of a long-standing discussion due to sewage disposal, water treatment upgrades, and runoff from agriculture or storms.

Presentation Preference: Poster

Primary Presenter: Deyanneira Colon Maldonado, University of Rhode Island - Graduate School of Oceanography (colondeyanneira@gmail.com)

Authors:

Deyanneira Colon Maldonado, University of Rhode Island - Graduate School of Oceanography  (colondeyanneira@gmail.com)

Rickie Ewton, University of Rhode Island - Graduate School of Oceanography  (rickie@uri.edu)

Susanne Menden-Deuer, University of Rhode Island - Graduate School of Oceanography  (smenden@uri.edu)