Hull Wesley W, Bourdeau Paul E
Telonicher Marine Laboratory, Humboldt State University, Trinidad, California, United States of America.
Department of Biological Sciences, Humboldt State University, Arcata, California, United States of America.
PLoS One. 2017 Aug 24;12(8):e0183064. doi: 10.1371/journal.pone.0183064. eCollection 2017.
Predation can strongly influence community structure and ecosystem function, so the loss of key predators can have dramatic ecological consequences, unless other predatory species in the system are capable of playing similar ecological roles. In light of the recent outbreak of sea star wasting disease (SSWD) and subsequent depletion of west coast sea star populations, including those of the keystone predator Pisaster ochraceus, we examined whether large mobile crabs could play a role as predators on mussels (Mytilus californianus) on a rocky shore in Northern California. Using a combination of sea star removal and predator exclusion cages we found that mussel mortality was 43-294 times greater in uncaged treatments versus caged treatments. Mortality on uncaged mussels at low tidal elevations was due to predation by large mobile crabs (Cancer productus and Romaleon antennarium); confirmed by the presence of mussel shell fragments and documented attacks on wax snail replicas. Laboratory feeding assays indicated that crabs, on a per unit biomass basis, can consume almost twenty-five times as many mussels per day than sea stars, which together with the results of our field experiment, suggest that large predatory crabs could play an important role in maintaining ecosystem function through their predation on mussels on rocky shores where P. ochraceus are rare, absent, or have been depleted by SSWD.
捕食能强烈影响群落结构和生态系统功能，因此关键捕食者的丧失可能会产生巨大的生态后果，除非系统中的其他捕食物种能够发挥类似的生态作用。鉴于近期海星消瘦病（SSWD）的爆发以及随后西海岸海星种群数量的减少，包括关键捕食者赭色海星（Pisaster ochraceus），我们研究了大型活动螃蟹是否能在北加利福尼亚州多岩石海岸上充当贻贝（加州贻贝，Mytilus californianus）的捕食者。通过结合去除海星和使用捕食者排除笼，我们发现与有笼处理相比，无笼处理中贻贝的死亡率高出43 - 294倍。低潮位时无笼贻贝的死亡是由大型活动螃蟹（首长黄道蟹，Cancer productus和触角黄道蟹，Romaleon antennarium）捕食所致；贻贝壳碎片的存在以及对蜡螺复制品的记录攻击证实了这一点。实验室喂食试验表明，按单位生物量计算，螃蟹每天消耗的贻贝数量几乎是海星的二十五倍，这与我们的野外实验结果一起表明，在赭色海星稀少、不存在或已因海星消瘦病而减少的多岩石海岸，大型捕食性螃蟹通过捕食贻贝可能在维持生态系统功能方面发挥重要作用。
