Project Funding: 2013 - 2014

NRA: 2012 NASA: Ocean Biology and Biogeochemistry   

Funded by NASA

Abstract:
Problem statement: The DWH oil spill posed a significant threat to the health of the Gulf of Mexico ecosystem, for example by damaging the pelagic Sargassum spp. that provides important habitat (food, shade, shelter) to fish, shrimp, crabs, turtles, and other marine organisms. Yet to date, despite the enormous amount of effort in studying the DWH event (including the PI s own work to quantify the oil spill surface expression and post- spill impact), two essential questions still remain to be answered: 1. How much surface oil is present in the surface ocean at a given time and location? 2. What occurred to GOM s Sargassum during and after the DWH spill? In addition, what occurred to the water column phytoplankton? Objectives: At synoptic scales, the above questions can only be answered through remote sensing, which unfortunately has been underutilized. The project here is to make use of the unprecedented airborne data, in conjunction with other remote sensing data and field data as well as radiative transfer models, to quantify the surface oil volume and to assess the spill s impact on marine algae in the northern GOM, with the following objectives: 1) Understand the optics of oil spills and develop algorithms to estimate surface oil volume, and document spatial and temporal distributions of surface oil expression and quantity. The outcome will help narrow down the area of potential impact on marine algae; 2) Assess oil spill impact on Sargassum during and after the DWH oil spill; 3) Depending on the feasibility study result, document and interpret temporal changes in phytoplankton community structure in the northern GOM in response to the DWH oil spill. Changes in phytoplankton fluorescence quantum yield will also be assessed; 4) Establish validated baseline data and methodology in response to future potential spills and other events, and provide recommendations for future NASA missions with specific goals of monitoring oil spills (e.g., GEO-CAPE).  Approach: The project will rely entirely on the analyses of both remote sensing and in situ data collected during the after the spill. Specifically, 1) Radiative transfer models (atmospheric correction, Monte-Carlo simulations) will be used in combination with AVIRIS, MODIS, MERIS, and Landsat data to understand the optical signature of various oil types (thin film versus emulsified oil) and thickness, and sensor-specific algorithms will be developed to derive the oil thickness; 2) Time series analysis of multi-sensor data will be used to provide information on the location, severity (i.e., thickness), and duration of the surface oil presence; 3) Customized atmospheric correction and bio-optical inversion algorithms will be developed and applied to the multi-sensor data to detect and quantify changes in Sargassum biomass, changes in fluorescence quantum yield, and possibly changes in phytoplankton community structure; 4) Document and publish established algorithms, approaches, and results, and provide recommendation for future missions on oil spill monitoring and impact assessment. Relevance and significance NASA’s potential in oil spill research in marine environments (in either assessment of the oil itself or assessment of the spill s environmental impacts) has been significantly under- utilized. The project PI has worked on both aspects under NASA support with some preliminary results published. The international collaborator adds world-class expertise in optical modeling of oil spills. The dedicated effort and activities outlined here will help realize the full potential of NASA capacity in both scientific research and societal needs for studying oil spills. For example, knowledge of changes in Sargassum biomass is of particular importance to assess the potential impact of the DWH oil spill on the various trophic levels of the marine ecosystem, and improved methods to quantify surface oil will help plan mitigation efforts for future spills.

Publications:

Long, J. S., Hu, C., Wang, M. 2017. Long-term spatiotemporal variability of southwest Florida whiting events from MODIS observations. International Journal of Remote Sensing. 39(3), 906-923. DOI: 10.1080/01431161.2017.1392637

Marechal, J., Hellio, C., Hu, C. 2017. A simple, fast, and reliable method to predict Sargassum washing ashore in the Lesser Antilles. Remote Sensing Applications: Society and Environment. 5, 54-63. DOI: 10.1016/j.rsase.2017.01.001

More details may be found in the following project profile(s):

• NASA Ocean Biology & Biogeochemistry (OBB) Project Profile