Dissolved Organic Nitrogen and Brown Tide Blooms in Long Island Coastal Waters

点击翻译按钮获取中文摘要

Blooms of the `Brown Tide` unicellular algae (Aureococcus anophagefferens) have occurred sporadically since 1985 in coastal waters of Eastern Long Island and have devastated the local commercial scallop fishery. Analysis of a 10 year time series data set from the Peconic Estuary indicates that bloom intensity is inversely correlated with the discharge of high nitrate groundwater and associated with higher salinities. Laboratory and field data suggest that salinity is unlikely to represent a direct physiological control on Brown Tide blooms. However budget calculations indicate that nitrogen supply from groundwater is 1 2 orders of magnitude higher than other external sources for this ecosystem. Data collected in 1995 demonstrated that Brown Tide blooms utilize dissolved organic nitrogen (DON) for growth as evidenced from the large decrease in DON parallel with cell increase. We hypothesize that bloom initiation is regulated by the relative supply of inorganic and organic nitrogen, determined to a large extent by groundwater flow variability. An appropriate first step to test this hypothesis is the demonstration that there are compounds in the DON that can be efficiently utilized by A. anophagefferens giving it a competitive advantage over other endemic species. We will identify the source of DON that is available to A. anophagefferens via field and laboratory studies. The laboratory work will involve the identification of the DON components from the Peconic Estuary that can support growth of the alga and characterization of the DON uptake systems and utilization mechanisms that make this alga competitive at utilizing nitrogen. Immunological probes to major proteins involved in the utilization of DON will be prepared. In the field we will characterize the DON fraction utilized by A. anophagefferens during a bloom as well as follow the nitrogen nutrition of this algae using immunological probes. Weekly nutrient bioassays and analysis of various dissolved and particulate nitrogen pools will complement the more detailed field sampling.