Sosik, Heidi: Woods Hole Oceanographic Institution (Project Lead)
Project Funding:
2013 - 2015
NRA: 2012 NASA: Ocean Biology and Biogeochemistry
Funded by NASA
Abstract:
The Middle Atlantic Bight has historically been one of the most productive shelf areas in the world, but the demand for coastal resources (e.g., fisheries, properties, and recreation areas) is growing at the same time that human-induced disturbances (e.g., nutrient loading, contaminant inputs, and introduced species) are increasing. Furthermore, there is direct evidence for substantial warming of these coastal waters and some observations indicate related impacts on the ecosystem. Phytoplankton community structure and dynamics have profound effects on the entire ecosystem, but insufficiently sustained and detailed observations have limited our ability to quantify their vulnerability and responses to these coastal changes. However, an ongoing multi-year time series at the Martha s Vineyard Coastal Observatory (MVCO) is beginning to hint at trends and possible mechanisms of phytoplankton community response:
- picophytoplankton, especially picocyanobacteria, appear to be increasing in biomass while the relative contribution of nanophytoplankton is declining;
- seasonal diatom blooms are persisting, perhaps through a mechanism of high biodiversity and complementary niches that stabilizes microphytoplankton biomass despite environmental extremes (such as the warmest winter on record in 2012); and
- optical proxies relevant for ocean color remote sensing indicate an overall increase in the composite cell size index for the phytoplankton community, suggesting that changes within the nanophytoplankton fraction deserve further attention.

The goal of this proposal is to assess whether these suggestive trends are robust and relevant for understanding responses to climate. This will be accomplished with a combination of continued in situ sampling, use of regional remote sensing products, and targeted controlled experiments in the laboratory. We will extend time series, expand spatial coverage, and conduct more in depth data analyses required to address the goal. The study will capitalize on the natural experiments that occur in response to event- scale dynamics, large amplitude seasonal cycles, and interannual perturbations associated with forcing at the regional scale and larger (e.g., anomalous winters).
We will characterize variability with a combination of high temporal resolution in situ observations at MVCO; boat-based observations (monthly at MVCO and bi-monthly to the mid-shelf), including depth profile sampling; and satellite-based remote sensing for regional scale spatial-temporal variability. MVCO also provides a comprehensive suite of meteorological and oceanographic observations. Regional properties will be mapped from standard MODIS products (SST, PAR, Chl, etc.) as well as emerging products for phytoplankton properties from ocean color radiometry (accessory pigments, cell size indices, etc.). Our primary tools for in situ characterization of diversity in the phytoplankton will be the automated submersible flow cytometers FlowCytobot (for optical properties of pico-to-nano-sized cells) and Imaging FlowCytobot (for optical properties and high-resolution images of nano-to-microplankton, allowing automated classification of cells into more than 40 taxonomic groups). These instruments have been deployed at MVCO since 2003 and 2006, respectively, and a laboratory benchtop version of the imaging instrument has been modified to control continuous culture experiments to study effects of environmental factors on phytoplankton growth rates.
We anticipate that this fundamentally time-series approach integrating high resolution taxonomic information with physiological properties and steps toward spatial upscaling (local to regional) will lead to fundamental insights into the response of this coastal system to change. Improved scientific understanding of this type is sorely needed for responsible stewardship in the face of societal concerns and as yet unpredictable consequences of climate change.
More details may be found in the following project profile(s):
