Hughes Brent B, Levey Matthew D, Fountain Monique C, Carlisle Aaron B, Chavez Francisco P, Gleason Mary G
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95060;
SeaSpatial Consulting, Santa Cruz, CA 95060;
Proc Natl Acad Sci U S A. 2015 Jun 30;112(26):8025-30. doi: 10.1073/pnas.1505815112. Epub 2015 Jun 8.
Coastal ecosystems provide numerous important ecological services, including maintenance of biodiversity and nursery grounds for many fish species of ecological and economic importance. However, human population growth has led to increased pollution, ocean warming, hypoxia, and habitat alteration that threaten ecosystem services. In this study, we used long-term datasets of fish abundance, water quality, and climatic factors to assess the threat of hypoxia and the regulating effects of climate on fish diversity and nursery conditions in Elkhorn Slough, a highly eutrophic estuary in central California (United States), which also serves as a biodiversity hot spot and critical nursery grounds for offshore fisheries in a broader region. We found that hypoxic conditions had strong negative effects on extent of suitable fish habitat, fish species richness, and abundance of the two most common flatfish species, English sole (Parophrys vetulus) and speckled sanddab (Citharichthys stigmaeus). The estuary serves as an important nursery ground for English sole, making this species vulnerable to anthropogenic threats. We determined that estuarine hypoxia was associated with significant declines in English sole nursery habitat, with cascading effects on recruitment to the offshore adult population and fishery, indicating that human land use activities can indirectly affect offshore fisheries. Estuarine hypoxic conditions varied spatially and temporally and were alleviated by strengthening of El Niño conditions through indirect pathways, a consistent result in most estuaries across the northeast Pacific. These results demonstrate that changes to coastal land use and climate can fundamentally alter the diversity and functioning of coastal nurseries and their adjacent ocean ecosystems.
沿海生态系统提供了许多重要的生态服务，包括维护生物多样性以及为许多具有生态和经济重要性的鱼类提供育苗场。然而，人口增长导致污染加剧、海洋变暖、缺氧以及栖息地改变，这些都对生态系统服务构成了威胁。在本研究中，我们利用鱼类丰度、水质和气候因素的长期数据集，评估了缺氧的威胁以及气候对埃尔克霍恩湿地鱼类多样性和育苗条件的调节作用。埃尔克霍恩湿地是美国加利福尼亚州中部一个高度富营养化的河口，也是一个生物多样性热点地区和更广泛区域近海渔业的关键育苗场。我们发现，缺氧状况对适宜鱼类栖息的范围、鱼类物种丰富度以及两种最常见的比目鱼——英国鳎（Parophrys vetulus）和斑点沙鲽（Citharichthys stigmaeus）的数量都有强烈的负面影响。该河口是英国鳎的重要育苗场，这使得该物种容易受到人为威胁。我们确定，河口缺氧与英国鳎育苗栖息地的显著减少有关，对近海成年种群和渔业的补充产生连锁反应，这表明人类土地利用活动会间接影响近海渔业。河口缺氧状况在空间和时间上存在差异，并通过间接途径因厄尔尼诺现象增强而得到缓解，这在东北太平洋的大多数河口都是一个一致的结果。这些结果表明，沿海土地利用和气候的变化会从根本上改变沿海育苗场及其相邻海洋生态系统的多样性和功能。
