26. Brown-to-blue: Fluvial deposition in the coastal ocean and its impact on nearshore ecosystems

Sediment, nutrients, and pollutants from a variety of land-based activities adversely impact many nearshore ecosystems in the United States and around the world. These contaminants are transported by surface water runoff into coastal waters, and there is compelling evidence that the sources have increased globally as a result of human-induced changes to watersheds. The small, steep rivers such as those found along the U.S. west coast are recognized to generate high sediment discharge, which can be effectively modified by alterations in land use. Significant anthropogenic modifications have been made to many of these rivers’ drainage basins, including agriculture, feral grazing and urbanization that have, in turn, altered the character and volume of land-based pollution released to the coastal ocean. Terrigenous run-off and deposition in the coastal ocean has potential impact on nearshore ecosystems by blocking light and inhibiting photosynthesis, directly smothering benthic fauna and fish habitat, and causing nutrification that alters ecosystem dynamics. Studies that combine information on watershed, surface flow, transport and fate of sediment and other pollutants in the nearshore environment, and their impact on marine ecosystem health are essential; these different components form the framework of the developing source-to-sink and ecosystem research programs around the world. USGS science capabilities are particularly well suited to provide science for making informed decisions on land-based pollution threats to nearshore ecosystems. For example, watershed and hydrologic data could be assimilated with geologic and oceanographic processes data and compared to nearshore benthic habitat surveys to develop an ecological model to predict the impacts of climate change or watershed modification on a critical nearshore species such as kelp, salmon or rockfish.

The goal of this work is to evaluate the mechanisms of sediment delivery to the shoreline and its dispersal in coastal ocean, especially with respect to land-use change. The postdoctoral fellow will develop and test innovative means for measuring and predicting rates, pathways and processes of material export from terrestrial to coastal systems using state-of-the-art process-response models and assimilations of disparate data types such as lidar- and satellite-derived high-resolution topography and bathymetry, coastal geomorphology, and historic and real-time oceanographic and meteorologic measurements. Specific tools that could be employed include high-resolution acoustic and optical profilers to measure flow and water column properties, sediment coring units, DELFT–3D numerical modeling and both side-scan and multibeam mapping systems. The research results will provide an important step in the longer-term goal of predicting how future climate change and human population growth may impact marine ecosystems. The study area will be the central coast of California, which has large fluvial sediment inputs and numerous critical marine habitats as described below.

The postdoctoral fellow will have ample opportunities for interdisciplinary collaborations in hydrology, ecology, geology, oceanography, physics, statistics, spatial data analyses, numerical modeling, remote sensing and engineering. She/he will be able to develop partnerships with researchers from different USGS centers, academia and other federal agencies (NPS, EPA, NOAA). The postdoctoral researcher will be at the forefront of interdisciplinary research in the United States and will participate in significantly improving our understanding of the delivery of land-based pollution to the coastal oceans and its impact on their long-term health.

Central California is regarded as the transition zone between the wetter Pacific Northwest and drier southern California, and recent climate modeling suggests that rainfall will decrease in the upcoming decades. This change will modify the magnitude and timing of fluvial sediment delivery to the coastal ocean and thus its impact on nearshore ecosystems. This region is of national importance for three reasons. First, central California is the home to three National Marine Sanctuaries, one National Seashore, one coastal National Monument and one National Recreation Area, along with one of the more advanced regional ocean observing systems in the nation (CenCOOS). Second, the state of California has implemented the Marine Life Protection Act, which designated the first comprehensive, integrated system of marine reserves along the US west coast, and central California is the test-bed for the state-wide MLPA effort. Third, and most importantly, the US west coast has seen a significant reduction in fisheries stocks (salmon, steelhead and rockfish; all federally threatened) that have resulted in fisheries closures; river mouths and shallow rock reef habitats are utilized by all of these species during different stages of their life cycles. These efforts directly corroborate the timeliness of this need: nearshore ecosystems are in world-wide decline due to a number of causes, and land-based pollution is singled out as a major contributor.

Proposed Duty Station: Santa Cruz, CA

Areas of Ph.D.: Oceanography, geology, hydrology, geography, coastal engineering

Qualifications: Applicants must meet one of the following qualifications: Research Oceanographer, Research Geologist, Research Engineer

(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Research Advisor(s): Curt Storlazzi, (831) 427-4721, cstorlazzi@usgs.gov; Jonathan Warrick, (831) 427-4793, jwarrick@usgs.gov; Amy Draut, (831) 427-4733, adraut@usgs.gov; David Rubin, (831) 427-4736, drubin@usgs.gov

Human Resources Office contact: Erica Settlemyer, (916) 278-9383, esettlemyer@usgs.gov

Summary of Opportunities