Rilov Gil, Schiel David R
Marine Ecology Research Group, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
Ecology. 2006 Mar;87(3):731-44. doi: 10.1890/04-1853.
In this study, we test in southern New Zealand a conceptual model of food web linkage that is seascape dependent, which can explain some of the variability in rocky shore community structure among sites and coasts. Using a comparative-experimental approach at local and distant sites we demonstrate that mobile subtidal predators (fish and crabs) can exert strong predation pressure on small mussels in the low tidal zone, but only in sites where the seascape includes subtidal reefs. On intertidal benches with adjacent subtidal reefs (+SR), 60-100% of small (5-15 mm) transplanted mussels were removed within a day from experimental tiles on the low shore when unprotected from predation, compared to fully caged controls that had approximately 100% survival over several months. In partial cages that exclude fish but not crabs, survivorship was intermediate. In contrast, on benches without subtidal reefs (-SR) 40-100% of mussels survived for months, even if unprotected. This difference is expressed in lower cover (0-60%) of mussels on rocks at +SR benches compared to -SR benches (70-99%). The central to northern west coast of the South Island is composed mostly of -SR benches, and predation on small mussels there was low and similar to the -SR benches on the east coast, whereas the +SR benches on the east coast had much greater predation. This contrasts to other studies in New Zealand that examined only predation on larger mussels by seastars and concluded that predation is strong on the west coast and weak on the east coast. Excluding large predators from low-shore areas with new recruits for a year in one +SR site showed longer-term predation effects on their abundance and cover. Short-term sampling at the east coast sites showed that mussel settlement was greater in -SR compared to +SR sites, providing some evidence that seascapes may also affect settlement. Overall, predation depended on the local seascape and ultimately affected community structure via suppression of effective recruitment rates. This study emphasizes the importance of predation on early life stages of basal species and the influence of seascapes on top-down interactions between subtidal predators and their intertidal prey.
在本研究中，我们在新西兰南部对一个依赖海貌的食物网联系概念模型进行了测试，该模型可以解释不同地点和海岸的岩岸群落结构中的一些变异性。通过在本地和远处地点采用比较实验方法，我们证明潮下带的移动捕食者（鱼类和螃蟹）可以对低潮带的小贻贝施加强大的捕食压力，但仅在海貌包括潮下带礁石的地点如此。在与潮下带礁石相邻的潮间带平台（+SR）上，当未受捕食保护时，60 - 100%的小型（5 - 15毫米）移植贻贝在一天内从低潮位的实验瓦片上被移除，相比之下，完全封闭的对照组在几个月内的存活率约为100%。在排除鱼类但不排除螃蟹的部分封闭环境中，存活率处于中间水平。相比之下，在没有潮下带礁石的平台（-SR）上，40 - 100%的贻贝存活了数月，即使没有保护措施。这种差异表现为与 -SR 平台（70 - 99%）相比，+SR 平台上岩石上贻贝的覆盖度较低（0 - 60%）。南岛的中西部海岸主要由 -SR 平台组成，那里对小贻贝的捕食较低，与东海岸的 -SR 平台相似，而东海岸的 +SR 平台捕食压力则大得多。这与新西兰其他仅研究海星对较大贻贝捕食的研究形成对比，那些研究得出西海岸捕食强烈而东海岸捕食较弱的结论。在一个 +SR 地点将大型捕食者从有新定居者的低潮带区域排除一年，显示出对其丰度和覆盖度的长期捕食影响。在东海岸地点的短期采样表明，与 +SR 地点相比：-SR地点的贻贝定居情况更好，这提供了一些证据表明海貌可能也会影响定居。总体而言，捕食取决于当地海貌，并最终通过抑制有效补充率影响群落结构。本研究强调了捕食对基础物种早期生命阶段的重要性以及海貌对潮下带捕食者与其潮间带猎物之间自上而下相互作用的影响。
