Grand Bay National Estuarine Research Reserve, Moss Point, Mississippi, United States of America.
The Institute for Marine Mammal Studies, Gulfport, Mississippi, United States of America.
PLoS One. 2018 Jun 21;13(6):e0199214. doi: 10.1371/journal.pone.0199214. eCollection 2018.
The co-occurrence of the Deepwater Horizon oil spill and the northern Gulf of Mexico cetacean Unusual Mortality Event have raised questions about the stability of inshore bottlenose dolphin (Tursiops truncatus) populations throughout the region. Several factors could have contributed to the ongoing event, but little attention has been paid to the potential effects of increased search effort and reporting of strandings associated with oil spill response activities, which were widespread for an extended period. This study quantified the influence of increased search effort by estimating the number of bottlenose dolphin strandings reported by oil spill responders and comparing monthly stranding rates with and without response-related records. Results showed that response teams reported an estimated 58% of strandings during the Active Response period within the study area. Comparison of Poisson rates tests showed that when responder-influenced stranding records were removed, the monthly stranding rates from the Active Response period (May 2010 -April 2014) were similar to the Post-Removal Actions Deemed Complete period (May 2013 -March 2015) (e.g., p = 0.83 for remote areas in Louisiana). Further, analyses using the Getis-Ord Gi* spatial statistic showed that when response-related stranding reports were removed from the Active Response period, significant spatial clustering of strandings (p < 0.05) was reduced by 48% in coastal Louisiana. Collectively, these results suggest that increased search effort resulting from the Deepwater Horizon oil spill response throughout remote portions of the Unusual Mortality Event geographic region had the capacity to increase reporting and recovery of marine mammal strandings to unusually high levels. To better understand how stranding data relates to actual mortality, more work is needed to quantify dolphin population size, population trends, and carcass detection rates including the role of search effort. This is vital for understanding the status of a protected species within the northern Gulf of Mexico.
深水地平线石油泄漏事件和墨西哥湾北部异常死亡率事件的同时发生，引发了人们对该地区近海宽吻海豚（Tursiops truncatus）种群稳定性的质疑。有几个因素可能导致了这一持续事件的发生，但人们很少关注与石油泄漏应对活动相关的搜索工作增加和搁浅报告的潜在影响，这些活动在很长一段时间内都广泛存在。本研究通过估算石油泄漏应急人员报告的宽吻海豚搁浅数量，量化了增加搜索工作的影响，并将有和没有与应急相关记录的每月搁浅率进行了比较。结果表明，在研究区域内的主动应对期间，应急小组报告了估计有 58%的搁浅事件。泊松率检验的比较结果表明，当去除受应急人员影响的搁浅记录时，主动应对期（2010 年 5 月至 2014 年 4 月）的每月搁浅率与移除行动完成后的时期（2013 年 5 月至 2015 年 3 月）相似（例如，路易斯安那州偏远地区的 p 值为 0.83）。此外，使用 Getis-Ord Gi* 空间统计分析的结果表明，当从主动应对期去除与应急相关的搁浅报告时，路易斯安那州沿海地区显著的搁浅空间聚类（p < 0.05）减少了 48%。总的来说，这些结果表明，由于深水地平线石油泄漏应对工作在异常死亡率事件地理区域的偏远地区的增加，搜索工作有可能增加海洋哺乳动物搁浅的报告和回收数量，使其达到异常高的水平。为了更好地了解搁浅数据与实际死亡率的关系，需要做更多的工作来量化海豚种群数量、种群趋势和尸体检测率，包括搜索工作的作用。这对于了解墨西哥湾北部保护物种的状况至关重要。
