This project will use two five-day-long ship-based sampling expeditions centered on previously studied hard banks in the Gulf of Mexico to assess pre- and post-oil spill impacts on the diversity, vitality, and distribution of the offshore seaweeds and macrocrustaceans (e.g. shrimp, crabs) living at depths of 45-90 meters. A comparison of the results of the current inventory with the inventories from previous surveys in the same region will be informative in terms of which species of benthic seaweed and crustaceans are most sensitive to oil pollution, and also allow predictions of their potential to subsequently recover from this ecological disaster.
Marine algae are the principal producers of oxygen in the marine ecosystem, and their die-off may affect the entire food chain and result in the expansion of an already existing "dead zone" throughout the Gulf. Post-spill changes in the diversity, population structure, and reproductive capacity of benthic seaweeds and macrocrustaceans (and other invertebrates) are measureable when compared to a large dataset from pre-spill sampling. Detection and quantification of these effects will reflect potential impacts of the oil spill in sensitive deep bank environments. All material collected from each trip will be sorted, identified, and the associated information entered into web-accessible databases. This effort will involve both undergraduate and graduate students.
In the northwestern Gulf of Mexico unconsolidated rubble and beds of rhodoliths ("red stones") are associated with unique offshore deep bank habitats at depths of 40-85 m, capping the salt domes that are peculiar to that part of the northern Gulf. These rubble habitats were prominent features harboring the highest known seaweed diversity in the NW Gulf prior to the April 2010 BP oil spill disaster, with rhodoliths completely or partially covered by crust-forming red algae supporting a great diversity of additional red, brown and green photosynthetic seaweeds, many of which were bladelike and provided lush vegetative cover. They also provided habitats for a diverse assemblage of animals, including the most diverse deep bank assemblages of crabs, shrimps, and lobsters in the Gulf. Results from the NSF-funded post-spill RAPID expeditions in December 2010 and April 2011 indicated that seaweed diversity in all dredged sites was severely depressed or altogether absent relative to pre-spill sampling. Diversity and abundance of the previously rich crab and shrimp populations was also diminished, and the species composition was altered. "Bare" or partly algal-denuded unconsolidated rubble brought back as "live rocks" from April and August 2011 post-spill cruises have been maintained in 20-gallon tanks, and this rubble gradually became covered by a suite of red, green and brown seaweed germlings that to this day continue to grow to adult size revealing biodiversity repressed in the NW Gulf at the time of the post-spill sampling. Many of these species currently growing and reproducing in tanks in the Biology Department at the University of Louisiana at Lafayette had not been observed in the field during the pre-spill samplingsTesting for algal spore presence in the seawater used to partly fill the tanks based on a PCR approach tested negative, providing evidence that the intrinsic source of the propagules is the "bare" rubble retrieved. The rate of algal succession is being documented by digital photography and their taxonomic identity is confirmed by ongoing molecular barcoding and morphological evidence. The implications of these exciting results indicating that undetected algal propagules, spores and germlings collected along with the "bare" rocky substrata have been triggered to germinate, grow, and reproduce under laboratory conditions that exclude herbivores, are far-reaching. These algal assemblages in laboratory settings go through a series of dynamic successions including temporal biomass decline and subsequent regrowth, reflecting pre-spill species composition at a particular collecting site. The emphasis on these cryptic (hidden) young seaweed stages forms the basis for newly proposed pending research. This new direction will place emphasis on understanding a complete context for the earliest stages of a seaweed’s life history leading to mature individuals, and on their role in overall algal community resilience following major anthropogenic insult. With the potential recovery of the algal assemblage, one might predict that the crab and shrimp populations could also recover to previously observed levels of diversity and abundance. This will of course depend upon the success of larval stages for these crustaceans, and their successful recruitment to the deep bank habitats over coming months and years. Recolonization could be influenced greatly by spill impacts on water column environments critically important to the success of larval stages, even after algal assemblages recovery. Continued field monitoring of the recovering algal assemblages on these deep banks, along with the associated crab and shrimp populations, should reveal whether pre-spill levels of species diversity and abundance are achieved. Strong emphasis was placed on Public Education and Outreach. To boost the project’s outreach efforts to the general public, the PIs Suzanne Fredericq and Darryl Felder, along with their undergraduate students, a postdoc, and graduate students at UL Lafayette contributed to the production of video clips demonstrating the science behind the Project in the YouTube channel "nemastoma2".
