Increasing nutrient concentrations and the rise and fall of a coastal fishery; a review of data from the Nile Delta, Egypt
Increasing nutrient concentrations and the rise and fall of a coastal fishery; a review of data from the Nile Delta, Egypt
复制标题
DOI：
10.1016/j.ecss.2007.11.028
复制
发表时间：
2008-04
影响因子：
2.8
通讯作者：
A. Oczkowski;S. Nixon
中科院分区：
文献类型：
--
作者：
A. Oczkowski;S. Nixon
有一个概念基础和一些经验证据表明，增加沿海水体的养分负荷最初会将生态系统生产力提高到某个阈值，超过该阈值，次级生产力和渔业产量将会下降。在这里，我们汇编了埃及和国际文献中有关鱼类上岸量的数据以及埃及尼罗河三角洲四个大型沿海泻湖（63-500km2）的无机养分（氮和磷）数据，为渔业产量对大范围富集（高达 1mM 溶解有机氮，DIN）养分供应增加的最初积极但随后消极的反应提供证据。将四个泻湖的数据作为一个总体，鱼类上岸量随着营养物质的增加而增加，达到约 100μM DIN 的上岸量峰值，超过该值，上岸量呈指数下降。看来，农药和重金属污染以及过度捕捞在 DIN 浓度最高时导致渔业产量下降中只发挥了很小的作用。我们没有足够的证据来说明导致渔业衰退的具体机制，但怀疑可能与富营养化的某些特征（例如低氧）有关。
There is a conceptual basis, and some empirical evidence, that increasing nutrient loads to coastal waterbodies will initially increase ecosystem productivity up to a threshold, beyond which secondary productivity and fishery yields will decline. Here we have compiled data from the Egyptian and international literature for fish landings and inorganic nutrient (nitrogen and phosphorus) data from four large coastal lagoons (63–500km2) on Egypt's Nile Delta to provide evidence for the initially positive, but then negative, response of fishery yields to increased nutrient supply across a very wide range of enrichment (up to 1mM dissolved organic nitrogen, DIN). Taking the data from the four lagoons as an aggregate, fish landings increase with increased nutrients up to a peak in landings at approximately 100μM DIN, beyond which there was an exponential decline in landings. It appears that pesticide and heavy metal contamination and overfishing played only minor roles in the lowered fishery yield at highest DIN concentrations. We do not have sufficient evidence about the specific mechanisms that led to the decline of the fishery, but suspect that some feature of eutrophication—low oxygen, for example, may have been involved.