Coupled effects of oil spill and hurricane on saltmarsh terrestrial arthropods

Abstract

Terrestrial arthropods play an important role in saltmarsh ecosystems, mainly affecting the saltmarsh’s primary production as the main consumers of terrestrial primary production and decomposition. Some of these arthropods, including selected insects and spiders, can be used as ecological indicators of overall marsh environmental health, as they are differentially sensitive to ecological stressors, such as land loss, erosion, oil spills, and tropical storms. In the present study, we used terrestrial arthropods collected from seven (three lightly-oiled, four heavily-oiled) sites in Barataria Bay and from three unoiled reference sites in Delacroix, Louisiana, to determine the impacts of the distribution and re-distribution of Deepwater Horizon (DWH) oil on these saltmarsh ecosystems. A total of 9,476 and 12,256 insects were collected in 2013 and 2014, respectively. The results show that the terrestrial arthropods were negatively affected by the re-distribution of DWH oil by Hurricane Isaac in 2012, although the level of impacts varied among the arthropod groups. Moreover, the mean diversity index was higher (>1.5) in 2014 than in 2013 (<1.5) for all sites, suggesting a recovery trajectory of the saltmarsh arthropod population. The higher taxonomic richness observed in the reference sites compared to the oiled sites for both years also indicated long-term impacts of DWH oil to the saltmarsh arthropod community. Whereas a slow recovery of certain terrestrial arthropods was observed, long-term monitoring of arthropod communities would help better understand the recovery and succession of the marsh ecosystems.

Stable isotope analyses identify trophic niche partitioning between sympatric terrestrial vertebrates in coastal saltmarshes with differing oiling histories

“…Post-spill declines in the abundance of terrestrial invertebrates, such as insects and spiders, also were reported for Louisiana marshes after the DWH oil spill (McCall & Pennings, 2012;Pennings, McCall & Hooper-Bui, 2014;Husseneder, Donaldson & Foil, 2016). However, significant temporal, spatial, and taxon-specific variation in post-spill responses and recovery across studies and the potential for redistribution of DWH oil by hurricanes (McCall & Pennings, 2012;Bam et al, 2018) likely confound comparisons of the availability of terrestrial resources to sparrows and rats in our study. Specifically, Hurricane Isaac in 2012 is thought to have remobilized and redistributed oil that was deposited in inshore and offshore sediments such that some coastal locations that were initially oil-free became contaminated with petroleum hydrocarbons (Turner et al, 2019).…”

“…The increase in niche width may show the subtle chronic effects of food web dynamics whereby the foraging behaviour of rats shifts to generalism (i.e., a niche expansion) at oiled sites, possibly in response to changes in prey availability/diversity. Researchers have reported persistent effects several years after the DWH oil spill whereby there were significant declines in diversity of marsh meiofauna and macrofauna (Fleeger et al, 2015;Fleeger et al, 2019), arthropods (Bam et al, 2018), fiddler crabs (Zengel et al, 2015) and snails (Deis et al, 2020). These changes in diversity and prey availability due to oil are not only limited to salt marshes but extend to other ecosystems.…”

“…Similarly, the DWH oil spilled resulted in sparrows incorporating carbon from oil into gut contents and newly grown feathers (Bonisoli-Alquati et al, 2016). The DWH oil spill led to decreased insect and arthropod abundances and altered community compositions at oiled sites compared to unoiled sites (Zengel et al, 2015;Husseneder, Donaldson & Foil, 2016;Bam et al, 2018) possibly leading to increased competition among terrestrial vertebrates for prey at oiled sites (sensu Bergeon Burns et al, 2014). Despite their potential as bioindicators, limited information exists on the trophic niches and trophic interactions of sparrows and rats (although see Olin et al, 2017;Johnson, Olin & Polito, 2019).…”

Transport Processes in the Gulf of Mexico Along the River-Estuary-Shelf-Ocean Continuum: a Review of Research from the Gulf of Mexico Research Initiative

“…Noticeably, this remobilization was such that sites initially classified as "un-oiled" eventually got contaminated, thus confounding subsequent analyses (Turner et al 2014a(Turner et al , b, 2019. Furthermore, the occurrence of re-oiling was confirmed by various ecological studies that, in addition to a partial ecosystem recovery in the 2 years after the oil spill, also found increased areas of oil-induced side effects after 2012 (Snyder et al 2015;Bam et al 2018;Perez-Umphrey et al 2018).…”

Formation of Oil-Particle-Aggregates: Numerical Model Formulation and Calibration

“…Oil spills have detrimental impacts on coastal ecosystems and marine life (Nixon et al, 2016;Bam et al, 2018;Robinson and Rabalais, 2019;Martin et al, 2020). As a result, oil models have been developed to predict the transport and fate of oil, often by employing Lagrangian particle tracking (Zhu et al, 2018).…”