COI Funded Project: The Influence of Dissolved Organic Phosphorus on Phytoplankton Blooms in Coastal Systems


Project Funded: 2005
Key Words: Biological Oceanography

Proposed Research

Over the second half of the 20th century, nutrient loading to coastal zones has increased dramatically. Excess loading of macronutrients to estuaries contributes to increases in surface chlorophyll a concentration, with concomitant effects on water clarity and dissolved oxygen that can negatively impact important fisheries. The largest estuary in the United States, the Chesapeake Bay exemplifies the current problem. Strategies to combat excess nutrient loading to the Bay have thus far addressed the total nitrogen (N) and phosphorus (P) inputs. However, not all forms of N and P are equally available to phytoplankton. P exists in many forms in estuarine systems and the bioavailabiliy of these different forms in the Chesapeake could have a major influence on plant growth, or chlorophyll a standing stock. Three organic forms of P constitute the dissolved organic phosphorus (DOP) pool: phosphomonoesters, phosphodiesters and phosphonates. Substantial work has been done to examine the phosphomonoesters which are available to phytoplankton through the activity of the alkaline phosphatase enzyme. Very little is known about algal phosphodiesterases and C-P lyases, the enzymes that mediate the bioavailability of the other two pools. We will assay the activity of all three enzymes in model cultures and coastal populations of phytoplankton in Chesapeake Bay. Anticipated outcomes from this research include: 1) Culture validation of new approaches to assay enzymes involved with DOP hydrolysis. 2) Field implementation of assays for DOP bioavailability. 3) An index of P bioavailability in the Chesapeake to document which P species have the largest impact on phytoplankton growth. This research will result in a better understanding of P bioavailability in the Chesapeake Bay allowing managers to target reductions of the most bioavailable P species (as determined herein). This will be more cost effective for the management of plant growth than the reduction of total P. In short, these data will allow the implementation of cost-effective Best Management Practices (BMPs) for the reduction of specific P species.