Sandy beaches, one of the most abundant coastal ecosystems, contain unique biodiversity, represent ecotonal habitats and are driven by distinctive ecological processes that provide critical ecosystem services. Food webs on sandy beaches may display a high level of trophic coupling at the beach-ocean interface where consumers take advantage of the high productivity generated in coastal waters, subsidizing the shore and providing facultative, seasonal or even perennial opportunities for alternative resource use. However, many beach ecosystems are trapped in a 'coastal squeeze' between urbanization and rising sea levels. These systems are also under threat from oil extraction, as is the case for beaches in Florida and possibly the SE USA as a result of the ongoing and extensive Deepwater Horizon spill. Therefore, trophic organization of these important coastal areas may be disrupted by selected human activities.
The main objectives of this RAPID project are to: (1) document the abundance of critical beach consumers, and (2) describe the trophic structure across sandy beach habitats with an emphasis on the macrobenthic fauna and in the context of potential changes resulting from acute beach oiling and/or chronic anthropogenic disturbance (i.e. development). The general sampling design calls for a series of beaches to be sampled both pre- and post oiling. The sandy beaches sampled will also span different levels of pre-spill anthropogenic disturbance (e.g., human population density, quantity of fixed structures, levels of habitat fragmentation). Characterization of the naturally occurring heavy stable isotopes of carbon (d13C) and nitrogen (d15N) will be conducted on the major benthic organisms and their food sources to 1) unravel food web structure; 2) detail the contribution of various food sources to consumer diets using 'mixing models'; and 3) evaluate variability of trophic position of major consumers, diet shifts, and subsidy integration across beaches with varying levels of development. The PIs also expect that ecosystem- level impacts of oiling as revealed via the food web may be detected with this approach.
Broader Impacts:
A post-doctoral associate will be trained and mentored in this RAPID project. One graduate student will be trained in field techniques and stable isotope analyses. Students conducting undergraduate research will receive training in compiling data on human usage of beaches and characterizing beach characteristics. A video documenting sampling activities and beach features will be assembled as an educational tool and will be posted on the USF, Department of Integrative Biology, website. The study will provide an opportunity for the research team to interact with a large group of local, state and federal agencies, all involved in some aspect of oil spill monitoring, assessment and clean-up. Likewise, the data collected on sandy beach ecosystem structure and dynamics can serve as a baseline for detecting future acute or chronic impacts on these coastal ecosystems. Results will be disseminated by publication in a peer- reviewed journal.
Intellectual Merit Sandy beaches represent one of the most abundant coastal ecosystems in the USA. They support a unique biodiversity and provide critical ecosystem services such as serving as areas for bird nesting and human recreation and tourism as well as offering storm protection for coastal developments. Animals that are found in the beach swash zone- the area of wave run up and back wash- are also important food for fish, birds, and predatory invertebrates. As a result of the Deepwater Horizon Oil Spill, beaches along the coastlines of the northeastern Gulf of Mexico were threatened by the possibility of being oiled, with the potential for ecosystem services to be disrupted. The overall purpose of the study reported here was to develop baseline data on ecological features of sandy beaches across a large geographic area that could be utilized for evaluating whether selected ecosystem features would change if beaches became oiled. Specifically, the abundance of sediment dwelling animals on beaches and their feeding behavior were targeted. The main objectives of this one year study were to: (1) document the abundance of macrofaunal animals greater than 1mm in size that dominated the communities of organisms living within beach sediments in both the swash zone and upper beach sands; and (2) characterize the diets of these macrofaunal organisms in sets of beaches that were either oiled or not impacted by oiling. The findings from this study revealed new information on ecology of sandy beaches from the southeastern USA/Gulf of Mexico coastline. Mole crabs were the most abundant taxa found in swash zone sediments and salt marsh grass, seagrass or macroalgae were the major components of wrack. Some oiled beaches had very low abundances of large ghost crabs while a broad range of sizes of ghost crabs was recovered from non-impacted beaches. Diets of coquinas and mole crabs, along with those of ghost crabs, when compared across all the beaches, displayed marked differences, but these were strongly related to the geographic location and type of plant material washed onto beaches. Such information can be compared to that already available from beaches in different climates and coastal settings and is invaluable for the development of baseline data for future impact assessment. Data from this study has been submitted to the Open Archival Information System maintained by NOAA-NODC. At oiled beaches, an unexpected finding was the presence of small tarballs within swash zone sediments. These tarballs were not visually obvious from field observations of sediment surfaces. Moreover, tarballs persisted at least through July 2011. Counts and measurements of tarballs from swash zone samples have not been previously reported and these results have provided the foundation for a more extensive investigation. Broader Impacts Impacts of oil spills are of concern to the general public given the potential for economic losses and potential physical and mental health concerns. Use of beaches is an important factor influencing level of tourism and oiled beaches discourage visits by beach goers. Our identification of prolonged oil contamination in the swash zone emphasizes that while much of a beach may be judged to be cleaned, areas washed by tidal movements may still harbor small oil products. Our documentation of tarballs in swash zone sediments calls for sustained monitoring of the beach environment in order to understand the longer-term effects of beach oiling and patterns of recovery within sandy beaches. A post-doc was mentored, and a graduate student (female) and 5 undergraduate students (all female) were trained. The research team made three presentations at national meetings based upon the findings of the study and the PI attended an NSF sponsored workshop designed to explore impacts of the oil spill on coastal ecosystems. Outreach activities included co-authoring a newspaper article: Myths associated with oil spill published in the St. Petersburg Times www.tampabay.com/news/perspective/spill-myths-debunked/1130916; interview of the PI by National Geographic News, April 2011; and interview of the PI for WMNF News, July 2011.
