Talley Drew M, Talley Theresa Sinicrope, Blanco Alexander
Department of Marine Science and Environmental Studies, University of San Diego, San Diego, California, United States of America.
California Sea Grant Extension Program, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, United States of America.
PLoS One. 2015 Mar 20;10(3):e0118891. doi: 10.1371/journal.pone.0118891. eCollection 2015.
Coastal ecosystem modifications have contributed to the spread of introduced species through alterations of historic disturbance regimes and resource availability, and increased propagule pressure. Frequency of occurrence of the Manila clam (Venerupis phillipinarum, Veneridae) in Southern California estuaries has increased from absent or sparse to common since the mid-1990s. Potential invasion vectors include seafood sales and aquaculture, and spread from established northern populations over decades. The clam's post-settlement habitat preferences are, however, uncertain in this region. Our project aimed to identify factors associated with established patches of the clam within a bay toward the southern end of this introduced range. During summer 2013, we sampled 10 tidal flat sites in Mission Bay, San Diego; each containing an area with and without hard structure (e.g., riprap, boulders). We measured likely environmental influences (e.g., sediment variables, distance to ocean). Manila clam densities across the bay were most strongly associated with site, where highest densities were located in the northern and/or back halves of the bay; and weakly correlated with lower porewater salinities. Within sites, Manila clam density was enhanced in the presence of hard structure in most sites. Prevailing currents and salinity regimes likely contribute to bay wide distributions, while hard structures may provide suitable microhabitats (refuge from predators and physical stress) and larval entrapment within sites. Results provide insights into decisions about future shoreline management efforts. Finally, we identify directions for future study to better understand and therefore predict patterns of establishment of the Manila clam in the southern portion of its introduced range.
沿海生态系统的改变通过改变历史干扰格局和资源可用性，以及增加繁殖体压力，促进了外来物种的扩散。自20世纪90年代中期以来，南加州河口菲律宾蛤仔（Venerupis phillipinarum，帘蛤科）的出现频率已从不存在或稀少变为常见。潜在的入侵途径包括海鲜销售和水产养殖，以及数十年来从已建立的北部种群扩散而来。然而，在该地区，这种蛤仔定居后的栖息地偏好尚不确定。我们的项目旨在确定在这个引入范围南端的一个海湾内，与已建立的蛤仔斑块相关的因素。2013年夏季，我们在圣地亚哥使命湾的10个潮滩地点进行了采样；每个地点都有一个有硬结构（如抛石、巨石）和没有硬结构的区域。我们测量了可能的环境影响因素（如沉积物变量、到海洋的距离）。整个海湾的菲律宾蛤仔密度与地点的相关性最强，最高密度位于海湾的北部和/或后半部分；与较低的孔隙水盐度弱相关。在各个地点内，大多数地点有硬结构时，菲律宾蛤仔的密度会增加。盛行的水流和盐度状况可能影响整个海湾的分布情况，而硬结构可能提供合适 的微生境（躲避捕食者和物理压力）以及在各地点内截留幼体 的环境。研究结果为未来海岸线管理工作的决策提供了见解依据。最后，我们确定了未来研究的方向，以便更好地理解并因此预测菲律宾蛤仔在所引入范围南部的定殖模式。
