Grossman Nearshore Habitats

Nearshore Habitats of the Skagit Delta: Forecasting Coastal Climate Change Impacts

USGS Coastal Habitats in Puget Sound Project: ~$100,000 total funding 
from 2007 to 2010
Additional funds needed for completion: $100,000 (two years)

Background and motivation: The nearshore region of the Skagit River Delta provides diverse habitats for salmon, forage fish, birds, and invertebrates, including shellfish that sustained indigenous peoples of the area for millennia. Crab, shrimp, clams and oysters are valued marine resources that utilize nearshore habitats but are increasingly impacted by changes in climate that affect quality and flow of water, sediment and nutrients. Our ability to forecast impacts to these marine resources and to better manage activities that adversely affect them relies on our knowledge of their distribution and habitat requirements.

This project focuses on mapping and classifying the seafloor substrate, morphology, and water column conditions that characterize habitats and quantify the biophysical processes that change them. Linking processes that influence water quality (e.g., temperature, salinity, pH, turbidity, dissolved oxygen, nutrient concentrations) and seafloor properties (morphology, sediment type) provides models to predict how habitats will change with expected climate forcing. This information is important for evaluating likely threats to valued marine resources, developing best practices for land-use activities that minimize impacts to nearshore habitats, and implementing management plans to assure population recovery.

Maps showing (top) high-resolution bathymetry and (bottom) acoustic backscatter intensity of the seafloor surrounding the Skagit Delta. This data along with underwater video, photographs, and dive surveys allow classifications of habitats to be made to quantify the distribution of habitats and marine resources.

Objective: The objectives of this research are to (1) quantify the distribution of benthic habitats and water column conditions that shape and control habitat availability, and (2) gather information on biophysical processes –hydrodynamics (currents, waves) and water quality (temperature and salinity gradients) – that influence habitats and are related to climate forcing, in order to forecast coastal climate impacts in the future across the delta ecosystem.

Project Team: The project team consists of scientists of the U.S. Geological Survey, Western Washington University, and the Skagit River System Cooperative (SRSC).

Expected outcomes (2011–2012): Maps and GIS data layers of the distribution of benthic habitats and water column characteristics that influence habitat availability; models relating climate forcing to habitat changes and impacts. Results will inform coastal and marine spatial planning, restoration designs that mitigate impacts to nearshore habitats, and forecasts of habitat responses to climate-driven changes to river flow, sediment delivery, sea level rise and estuarine mixing by winds, waves, and tides.