Abstract
The Gulf of Mexico experiences frequent perturbations, both natural and anthropogenic. To better understand the impacts of these events, we must inventory natural variability within the ecosystem, communities, species, and populations, and contextualize these findings in relation to physical features. Here, we present an integrated study of comparative population genomics and biophysical oceanography. Targeting three species of mesopelagic shrimp common to the Gulf of Mexico midwater (Acanthephyra purpurea, Systellaspis debilis, and Robustosergia robusta), we analyzed genetic diversity and population connectivity as proxies for species health and resilience, respectively. We also simulated a range of vertical migratory behaviors of the shrimp to infer the relationship between diel vertical migration and horizontal transmission between the Gulf of Mexico and the greater Atlantic Ocean. This study aims to establish biological baselines and characterize these values in terms of the prevailing oceanographic feature of the midwater: the Gulf Loop Current. Generally, the oplophorid species (A. purpurea and S. debilis) exhibit lower genetic diversity and higher interpopulation homogeneity compared to the sergestid (R. robusta). Biophysical simulations suggest the differences in vertical migratory regimes between these two groups have important implications for horizontal transport out of the Gulf of Mexico. Because of the difference in vertical migration patterns, access to the Gulf Loop Current varies across taxa and impacts inter-basin migration. Our findings suggest a negative correlation between surface abundance and genetic diversity in these three shrimp species. We hypothesize that this correlation may be due to the relationships between surface abundance and access to the fastest moving waters of the Gulf Loop Current.
Highlights
The Gulf of Mexico experiences frequent environmental perturbations
This study focuses on population genomics and biophysical connectivity of three mesopelagic crustacean species in relation to the Gulf Loop Current (GLC) and associated eddies, the principal mixing features in the Gulf of Mexico
Due to a lack of archived c oxidase subunit I (COI) sequences for R. robusta in GenBank, Basic Local Alignment Search Tool (BLAST) results identified five individuals as Robustosergia regalis, none of which were included in downstream analyses
Summary
The Gulf of Mexico experiences frequent environmental perturbations. In the past decade alone, the region has been struck by two major hurricanes: Hurricane Ike in 2008 (Kraus and Lin, 2009) and Hurricane Harvey in 2017 (van Olderborgh et al, 2017). The Gulf of Mexico hosts a hyper-diverse mesopelagic zone (Sutton et al, 2017) and is described as a unique biogeographic ecoregion, distinct from the Caribbean Sea, Sargasso Sea, and greater Atlantic Ocean (Backus et al, 1977; Gartner, 1988). The frequent perturbations, both natural and anthropogenic, may have a drastic impact on the Gulf mesopelagic given its unique biological community and connections (St. John et al, 2016). Research efforts must focus on diagnosing Gulf health, contextualizing health in relation to the Gulf ’s relationship to the greater Atlantic, and understanding the role(s) of major oceanographic features on inter-basin population connectivity
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