Physical Forcing and Seasonal Variations in Phytoplankton in the Coastal Ocean

Chlorophyll blooms typical in wintertime at MVCO are visible in satellite imagery (Image courtesy of Heidi Sosik).

The overall objective of this project is to understand the processes controlling the seasonal variability of phytoplankton biomass over the inner shelf off the northeast coast of the United States.

Coastal ocean ecosystems are highly productive and play important roles in the regional and global cycling of carbon and other elements but, especially for the inner shelf, the combination of physical and biological processes that regulate them are not well understood. Past studies have shown dramatic seasonal variability in phytoplankton biomass on the northeast US shelf with low levels between the spring and fall equinoxes, and high levels with high variability between the fall and spring equinoxes. Information on the inner shelf is sparse, but suggests pronounced winter blooms. This study, funded by the National Aeronautics and Space Administration's Office of Earth Science, combines analysis of satellite imagery, Regional Ocean Model System (ROMS) numerical simulations, and long-term, in-situ measurements of biological, physical, and chemical variables at the Martha's Vineyard Coastal Observatory (MVCO).

Investigators from WHOI plan to document changes in phytoplankton biomass on the inner continental shelf over a range of space and time scales. In conjunction with investigators from Rutgers University, measurements and models will be used to characterize vertical mixing and cross-isobath transport processes. This interdisciplinary approach should help to improve understanding of winter and autumn phytoplankton blooms over the inner shelf with an emphasis on their relationship to physical processes that regulate light and nutrient availability. These results will significantly advance knowledge of how physical, chemical, and ecological factors interact to regulate variability in phytoplankton biomass in coastal regions. This knowledge is critical for assessment of climate change and anthropogenic effects on coastal ecosystems.

Optics Acoustics and Stress In Situ (OASIS)

Optics Acoustics and Stress In Situ (OASIS) is a project funded by the Office of Naval Research (ONR) to provide a critical evaluation of the dynamics of suspended particles and their effects on the optical and acoustical characteristics of the water column. The measurements will be used to evaluate a state-of-the-art model of particle dynamics and should ultimately improve predictions and interpretations of suspended sediments and the associated acoustical and optical fields.

Instrumentation deployed at the Martha's Vineyard Coastal Observatory, just south of the Air-Sea Interaction Tower (ASIT), in 15 meters of water includes:

1. AC-9 spectrophotometer (WETLabs)
2. AQUAscat multi-frequency acoustic backscattering sensor (AQUATEC)
3. TAPS multi-frequency acoustic backscattering sensor (BAE)
4. LISST-floc, near-forward scattering sensor (Sequoia, Sci.)
5. (2) EcoVSF, 3-angle, single wave length optical backscattering sensor (WETLabs)
6. (2) LSS, broad-angle, single wave length optical backscattering sensor (WETLabs)
7. WETStar, CDOM fluorometer (WETLabs)
8. Autonomous camera

A second platform was deployed to measure bottom turbulence characteristics and currents and included two 5-MHz ADVs and one 16-MHz ADV.