Sensing coral reef connectivity pathways from space

Coral reefs rely on inter-habitat connectivity to maintain gene flow, biodiversity and ecosystem resilience. Coral reef communities of the Red Sea exhibit remarkable genetic homogeneity across most of the Arabian Peninsula coastline, with a genetic break towards the southern part of the basin. While previous studies have attributed these patterns to environmental heterogeneity, we hypothesize that they may also emerge as a result of dynamic circulation flow; yet, such linkages remain undemonstrated. Here, we integrate satellite-derived biophysical observations, particle dispersion model simulations, genetic population data and ship-borne in situ profiles to assess reef connectivity in the Red Sea. We simulated long-term (>20 yrs.) connectivity patterns driven by remotely-sensed sea surface height and evaluated results against estimates of genetic distance among populations of anemonefish, Amphiprion bicinctus, along the eastern Red Sea coastline. Predicted connectivity was remarkably consistent with genetic population data, demonstrating that circulation features (eddies, surface currents) formulate physical pathways for gene flow. The southern basin has lower physical connectivity than elsewhere, agreeing with known genetic structure of coral reef organisms. The central Red Sea provides key source regions, meriting conservation priority. Our analysis demonstrates a cost-effective tool to estimate biophysical connectivity remotely, supporting coastal management in data-limited regions

An Empirically Validated Method for Characterizing Pelagic Habitats in the Gulf of Mexico Using Ocean Model Data

Mesoscale oceanic features such as eddies generate considerable environmental heterogeneity within the pelagic oceans, but their transient nature makes it difficult to identify both their spatial and temporal extent and their effects on the distribution of pelagic fauna. Simplifying these complex features using a biologically meaningful classification system will likely be a useful first step in understanding the extent of their influence in structuring open‐ocean ecosystems. In this study, we present a tool to classify the pelagic environment in the Gulf of Mexico using sea‐surface height and temperature‐at‐depth data from the 1/25° GOM HYbrid Coordinate Ocean Model (HYCOM). Three “water types” were identified: Loop Current‐origin water (LCOW), Gulf common water (CW), and mixed (MIX) water, where the latter represents an intermediate state during the degradation of LCOW to CW. The HYCOM‐derived classifications were validated against in situ CTD data and microbial samples collected through 2015–2016 by the Deep Pelagic Nekton Dynamics of the Gulf of Mexico (DEEPEND) consortium. The validation data comprised classifications derived from both temperature‐depth (TD) and temperature‐salinity (TS) profiles and from microbial community analyses from the surface to mesopelagic depths. The HYCOM classifications produced an overall agreement rate of 77% with the TS/TD classifications, and 79% with the microbial classifications. With applicability across a wide range of spatial and temporal scales, we believe that the system provides a useful, complementary tool for biological oceanographers and resource managers interested in better understanding the effects of major mesoscale features on the pelagic biota

Adaptation Without Boundaries: Population Genomics in Marine Systems

From the surface, the world’s oceans appear vast and boundless. Ocean currents, which can transport marine organisms thousands of kilometers, coupled with species that spend some or all of their life in the pelagic zone, the open sea, highlight the potential for well-mixed, panmictic marine populations. Yet these ocean habitats do harbor boundaries. In this largely three-dimensional marine environment, gradients form boundaries. These gradients include temperature, salinity, and oxygen gradients. Ocean currents also form boundaries between neighboring water masses even as they can break through barriers by transporting organisms huge distances. With the advent of next-generation sequencing approaches, which allow us to easily generate a large number of genomic markers, we are in an unprecedented position to study the effects of these potential oceanic boundaries and can ask how often and when do locally adapted marine populations evolve. This knowledge will inform our understanding of how marine organisms respond to climate change and affect how we protect marine diversity. In this chapter I first discuss the major boundaries present in the marine environment and the implications they have for marine organisms. Next, I discuss the how genomic approaches are impacting our understanding of genetic connectivity, ocean fisheries, and local adaptation, including the potential for epigenetic adaptation. I conclude with considerations for marine conservation and management and future prospects