IMPACTS OF DWHOS ON GENETIC DIVERSITY
Genetic diversity is a key attribute of populations because it provides the foundation for the ability to adapt to changing environments. This adaptability is of increased concern given shifting ocean temperature and acidification due to climate change. Genetic diversity can be reduced by rapid declines in population sizes (e.g., due to events such as large-scale pollutant spills), followed by even further reductions caused by inbreeding within the smaller remaining populations. In turn, low genetic diversity can impact the viability of populations by reducing not only their ability to recover from damage but also their resilience to changing ocean conditions. As such, assessing genetic diversity is important for evaluating the status of populations and plays a key role in conservation and management efforts. The DEEPEND team will examine if the DWHOS has impacted population sizes of fishes and invertebrate species enough to cause a reduction in their genetic diversity.
Dr. Mahmood Shivji, Co-PI, on the assessment of genetic biodiversity of mesopelagic fish in the Gulf of Mexico:
Crustacean Population Genetics
Our work investigating the genetic diversity and connectivity of crustaceans in the Gulf of Mexico can give us important insight into the effects of the oil spill on the environment. Genetic diversity, which is tightly tied to species health, describes differences between individuals at the DNA-level. The more genetic diversity within a species, the better chance the species has of overcoming ecological changes and challenges. The way diversity is distributed and moves throughout the environment is described as population connectivity. Connectivity through migration of adults or recruitment of pelagic larvae disseminates and maintains diversity throughout habitable environments. Because of this, connectivity can be used to describe species and community resilience: when a perturbation is applied, disrupting lowering local diversity, connectivity allows for genetic rescue from gene pools outside the perturbation’s influence. In this way, connectivity can also help us predict the recovery potential of a species. Both metrics, diversity and connectivity, are very important for diagnosing the effects of the oil spill and for predicting recovery.
In addition to the genetic assessments of diversity and connectivity, the Bracken-Grissom, Eytan, Shivji, and Judkins’s labs are undertaking a comprehensive DNA barcoding initiative for crustaceans, fishes, and cephalopods from the GoM. DNA barcoding allows us to identify species by using a DNA sequence from a specific genomic region as an identifier or “barcode”. This can be extremely useful to discern species complexes that might be undistinguishable at the morphological level. Tissue samples from 350 fish species have been collected to date, with over 40% of these barcoded so far. We have already found evidence of undiscovered species of viperfish, eels, and oceanic basslets, and expect to find more “cryptic” fish species during the course of the project. In a similar manner, DNA barcoding can also be of use to elucidate larval-adult linkages for many species whose larval and/or adult identities are not well known. For example, morphological differences between life-stages are commonplace within Crustacea, thus molecular methodologies such as these are indispensable for an accurate characterization of the Gulf's crustacean biodiversity. For this purpose, all labs are employing one or two mitochondrial regions (16S & COI) that have previously demonstrated their usefulness for identification, systematics, and phylogeographic studies of marine invertebrates and vertebrates. Approximately 90 species of crustaceans have been identified so far by DEEPEND taxonomists (including several new records for the Gulf), which are in the process of being barcoded for these genes. Thirty-nine cephalopods have been barcoded to date and the research focus is examining the genetic diversity of cephalopods within the Gulf of Mexico. Ongoing studies also include the morphological and molecular identification of numerous larvae, and continued identification of species new to science.