The Study Will Include Three Integrated Effortss: Two Remote Sensing Efforts Coupled By

Mobile Bay Plume Studies: A Collaborative Effort NASA RPC 18 April 2008

Purpose: The goal of the research is to produce and test tools that will define the sediment and brackish water plume of an estuary communicating with a sound or sea. It will specifically address the Mobile Bay plume, improving remote sensing of this phenomenon for other coastal areas. The specific purpose of this task is to provide ground truth measurements for remote sensing tools and numerical models of the plume.

Background: The ability to identify, quantify, and predict plumes from major bays (such as Mobile Bay) is important for a number of interrelated reasons. By studying plume dynamics we are potentially able to describe or predict coastal hydrodynamics, quantify sediment transport to aid in coastal sediment management, assess the impact of those discharged sediments (and associated nutrients and organic materials) on coastal water quality, and understand watershed land-use. Approach: Collaborative NASA-Mississippi State University (MSU) projects are developing new capabilities in plume motion detection and recognition. Using the Mobile Bay plume as a test site, they employ remote sensing capabilities supported by in situ data. One project, led by investigators at the NASA Stennis Space Center, focuses primarily on capturing and quantifying Mobile Bay’s external plume – the buoyant sediment plume on the continental shelf in the nearshore (< 30 miles) Gulf of Mexico. A second effort, led by investigators at MSU, concentrates on the internal plume – within Mobile Bay and Mississippi Sound. The two projects are linked since the (internal) Bay is the source of the (external) Gulf of Mexico plume. In situ data are provided by sampling cruises within the Bay, Mississippi Sound, and the Gulf of Mexico in collaboration between NASA-MSU investigators and the Dauphin Island Sea Lab. Data collection is also coordinated with other entities that collect and or use environmental data, such as the Alabama Department of Environmental Management and the USA Corps of Engineers, and will leverage studies by the NOAA-funded Northern Gulf Institute directed at estimating watershed loads to and sediment transport within and through Mobile Bay, including application of advanced numerical flow and transport models. Establishing calibrated remote sensing methods for tidal plume measurements will offer enormous benefits over the conventional “blind man and the elephant” approach of trying to extrapolate over large areas from a limited number of point samples, particularly given the time and cost associated with collecting those point samples. The results from this study will contribute to the Gulf of Mexico Regional Sediment Management Master Plan and may contribute to understanding critical fish habitats, such as submersible aquatic vegetation. Status: Data collection cruises began in November 2007. Two cruises – one for the outer plume and one for the inner plume -- are completed each month, with about 16 stations sampled each cruise (see Figures 1 and 2). Water samples are taken at one to three depths for analysis of dissolved organic carbon, total particulate carbon, chlorophyll-a, and total suspended solids. Vertical profiles of light extinction, temperature, dissolved oxygen, and turbidity are taken with an in-situ meter. Data are provided to the NASA and MSU research team members monthly.

Figure 1. Inside Plume Station Locations

Figure 2. Outside Plume Station Locations

Points of Contact: MSU: Dr. James L. Martin, 662-325-7194, [email protected] NASA: Dr. Jean T. Ellis, 228-688-1185, [email protected]