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

自1985年以来，“褐潮”单细胞藻类（嗜食金黄色球菌）在长岛东部沿海水域零星发生，并破坏了当地的商业扇贝渔业。对Peconic河口10年时间序列数据的分析表明，水华强度与高硝酸盐地下水流量呈负相关，与高盐度相关。实验室和实地数据表明，盐度不太可能代表对褐潮华的直接生理控制。然而，预算计算表明，地下水的氮供应比该生态系统的其他外部来源高12个数量级。1995年收集的数据表明，褐潮水华利用溶解有机氮（DON）进行生长，DON在细胞增加的同时大幅下降。我们假设水华的发生是由无机氮和有机氮的相对供应调控的，在很大程度上是由地下水流量的变化决定的。验证这一假设的第一步是证明在DON中有一些化合物可以被a . anophagefferens有效地利用，使其比其他特有物种具有竞争优势。我们将通过实地和实验室研究来确定食虫a.a anophagefferens的DON来源。实验室工作将包括鉴定Peconic河口的DON成分，这些成分可以支持藻类的生长，并表征DON吸收系统和利用机制，使这种藻类在利用氮方面具有竞争力。制备与DON利用相关的主要蛋白的免疫探针。在野外，我们将表征a.a anophagefferens在开花期间利用的DON部分，并使用免疫探针跟踪这种藻类的氮营养。每周的营养生物测定和各种溶解氮和颗粒氮池的分析将补充更详细的现场采样。

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.