Galaska, M. | bioRxiv Science

bioRxiv2021

Seascape genomics reveals metapopulation connectivity network of Paramuricea biscaya in the northern Gulf of Mexico

The degree of connectivity among populations influences their ability to respond to natural and anthropogenic stressors. In marine systems, determining the scale, rate, and directionality of larval dispersal is therefore central to understanding how coral metapopulations are interconnected and the degree of resiliency in the event of a localized disturbance. Understanding these source-sink dynamics is essential to guide restoration efforts and for the study of ecology and evolution in the ocean. The patterns and mechanisms of connectivity in the deep-sea (> 200 meters deep) are largely understudied. In this study, we investigated the spatial diversity patterns and metapopulation connectivity of the octocoral Paramuricea biscaya throughout the northern Gulf of Mexico (GoM). Paramuricea biscaya is one of the most abundant corals on the lower continental slope (between 1200 and 2500 m) in the GoM. The 2010 Deepwater Horizon oil spill (DWH) directly impacted populations of this species and thus are considered primary targets for restoration. We used a combination of seascape genomic analyses, high-resolution ocean circulation modeling, and larval dispersal simulations to quantify the degree of population structuring and connectivity among P. biscaya populations. Evidence supports the hypotheses that the genetic diversity of P. biscaya is predominantly structured by depth, and that larval dispersal among connected populations is asymmetric due to dominant ocean circulation patterns. Our results suggest that there are intermediate unsampled populations in the central GoM that serve as stepping stones for dispersal. The data suggest that the DeSoto Canyon area, and possibly the West Florida Escarpment, critically act as sources of larvae for areas impacted by the DWH oil spill in the Mississippi Canyon. This work illustrates that the management of deep-sea marine protected areas should incorporate knowledge of connectivity networks and depth-dependent processes throughout the water column.

ecology↗

bioRxiv2021

Utility of Occupancy Models with Environmental DNA (eDNA) fromOlympic Coast National Marine Sanctuary

Adjacent to the spectacular, rugged coastline bordering the Olympic Peninsula of Washington State, Olympic Coast National Marine Sanctuary (OCNMS) encompasses 8257 km2 of coastal waters that support one of North Americas most productive marine ecosystems. These rich waters support important recreational, commercial and subsistence fisheries for Washington state and four sovereign tribal governments: the Quinault Indian Nation and the Makah, Quileute and Hoh Tribes. Given its ecological, cultural and economic significance, managers from OCNMS are tasked with monitoring and management towards conserving the areas ecological integrity. The development of metabarcoding with environmental DNA (eDNA) as an effective freshwater monitoring tool has potential applications in marine systems, but the statistical analysis and the interpretation of those eDNA results are still under development. One promising strategy to analyze eDNA is through the use of occupancy models. Occupancy models enable us to calculate probabilities of detection from each taxon sequenced and are designed to work with presence-absence data. To inform our long term monitoring design of this coastal ecosystem, we collected 44 eDNA samples at nine of OCNMS long term mooring sites in 2019 and tested four different molecular markers for species reported and taxonomic richness. Additionally, we assessed occupancy models for use with eDNA to estimate the number of samples required to accurately predict the presence of a species. Occupancy models show great promise for use in eDNA studies provided there is sufficient replication; additionally, the choice of molecular marker strongly influences a taxas probability of detection. Author SummaryWe show the utility of using occupancy models with eDNA in Olympic Coast National Marine Sanctuary for monitoring near-shore marine biological communities. Based on probabilities of detection, long term coastal monitoring projects using eDNA would benefit from designs prioritizing sample number (10-20 samples per site) over sites sampled. With proper study design, occupancy models provide a statistical framework for comparisons between sites and over time. By accounting for simple non-detection vs true absence, occupancy models help to eliminate noise from eDNA studies, increasing detection of true shifts in community composition. We also demonstrate that marker choice is an important study design consideration not only for the types of taxa recovered, but also for consistency between samples and timepoints.

bioinformatics↗