Evaluation of Blue Crab, <i>Callinectes sapidus</i>, Megalopal Settlement and Condition during the Deepwater Horizon Oil Spill

The Blue Crab, Callinectes sapidus, is a commercially, culturally, and ecologically significant species in the Gulf of Mexico (GOM), whose offshore stages were likely impacted by the Deepwater Horizon oil spill (DWH). To test for DWH effects and to better understand the planktonic ecology of this species, we monitored Callinectes spp. megalopal settlement and condition at sites within and outside of the spill extent during and one year after the DWH. We tested for DWH effects by comparing 2010 settlement against baseline data available for two sites, and by testing for differences in settlement and condition inside and outside of the spill extent. We also developed time series models to better understand natural drivers of daily settlement variation (seasonal and lunar trends, hydrodynamics, wind) during 2010 and 2011. Overall, we found that neither megalopal settlement nor body weight were significantly reduced at oiled sites, but that high unexplained variation and low statistical power made detection of even large effects unlikely. Time series models revealed remarkably consistent and relatively strong seasonal and lunar trends within sites (explaining on average 28% and 9% of variation, respectively), while wind and hydrodynamic effects were weak (1–5% variation explained) and variable among sites. This study provides insights into DWH impacts as well as the natural drivers of Callinectes spp. megalopal settlement across the northern GOM.蓝蟹（Blue Crab，*Callinectes sapidus*）是墨西哥湾（Gulf of Mexico, GOM）中兼具商业、文化与生态重要性的物种，其近海生活史阶段很可能受到了深水地平线漏油事件（Deepwater Horizon oil spill, DWH）的影响。为验证深水地平线漏油事件的影响，并深入理解该物种的浮游生态学，我们于漏油事件发生期间及发生后一年，在漏油影响范围内外的多个监测点，对梭子蟹属（Callinectes spp.）大眼幼体的定居量与健康状况开展了监测。我们通过两种方式验证漏油事件的影响：一是将2010年的幼体定居量与两处监测点的基线数据进行对比，二是检验漏油影响范围内外的幼体定居量与健康状况是否存在显著差异。此外，我们还构建了时间序列模型，以解析2010年与2011年间每日幼体定居量波动的自然驱动因子，包括季节与月相周期、水动力条件及风力因素。整体而言，我们发现受油污影响的监测点中，大眼幼体的定居量与个体体重均未出现显著下降；但由于存在大量无法解释的波动，且统计效力偏低，即便存在较强的影响效应，也难以被检测到。时间序列模型结果显示，各监测点内均存在高度一致且相对显著的季节与月相周期特征，二者分别平均可解释28%与9%的定居量波动；而风力与水动力条件的影响则较弱，仅能解释1%至5%的波动，且不同监测点间的影响效应存在差异。本研究为解析深水地平线漏油事件的影响，以及墨西哥湾北部海域梭子蟹属大眼幼体定居的自然驱动因子提供了重要见解。