University of New England

A Coastal Observing System for Saco Bay

The infrastructure for this project is supported by a $499,927 award from the Maine Technology Institute from August 1, 2006, through July 31, 2011.

Principal Investigators

Phil Yund, Ph.D., Director
Marine Science Education and Research Center    
University of New England

Steve Zeeman, Ph.D., Professor
Dept. of Biology
University of New England

Charles Tilburg, Ph.D., Asst. Prof.
Dept. of Chemistry and Physics
University of New England

Individual Collaborators

Joe Kelley, Ph.D.
Mary Jane Perry, Ph.D.
Huijie Xue, Ph.D.
School of Marine SciencesUniversity of Maine

Institutional Collaborator

Gulf of Maine Ocean Observing System

Problem

The Saco River is the fourth largest river in the State of Maine, with a discharge rate that can exceed 600 m³ s^-1 during spring run-off events.  During such events, the plume of river water extends over many tens of square kilometers of the coastal ocean.  River discharge is thought to be a major driver of the western Maine coastal current and to play a critical role in the formation of coastal blooms of toxic phytoplankton.  However, the contributions of individual river plumes to coastal dynamics have not yet been explored.  Specific science questions for the Saco River discharge include:

1. What is the spatial extent of the discharge plume, and how does it vary temporally?
2. How is sediment flux within Saco Bay and transport offshore related to river discharge?
3. What are the biological consequences of plume mixing in Saco Bay, with respect to nutrient delivery and primary productivity?
4. How do meteorological events affect mixing and plume behavior?
5. Can wind or tide-driven mixing during a discharge event reduce bottom salinity sufficiently to kill benthic marine organisms in Saco Bay?
6. How does variation in global climate affect the linkages between the river, the bay, and the coastal current?

The last question is a long-term goal that will extend beyond the formal end of this five-year project.
 

Approach

Answering these questions requires long-term data collection that can only be achieved with remotely deployed sensors.  Consequently, we will assemble a coastal observing system that will consist of one buoy and one shore-based station, each equipped with multiple sensors.  Sensors on the buoy will continuously monitor water temperature, salinity (at multiple depths), chlorophyll, current velocity profiles, wave characteristics, and wind speed and direction.  All data will be telemetered back to shore and will be available to the research community and the general public on a near real-time basis via a web interface provided by the Gulf of Maine Ocean Observing System (GoMOOS).  The shore-based station will feature a sub-set of the sensors deployed on the buoy, plus nutrient sensors, and data from these instruments will also be available via GoMOOS.

These two fixed-position systems are most useful for addressing temporal dynamics.  With only two sites, inferences about spatial dynamics would be severely limited.  Consequently, we will also deploy additional instrumentation on an intermittent, site-specific basis.  Instruments in this “moveable” category include two acoustic doppler current profiler (ADCP) and CTD combinations mounted in trawl-proof frames (to characterize waves, current velocity profiles, and bottom salinity) and four GPS drifters to track surface currents.  In combination, this equipment will let us better characterize the spatial extent and behavior of the discharge plume. 

Remote observations from these systems will provide the core data to address the science questions, but cannot provide all of the necessary information.  Consequently, we will be seeking other funding sources and collaborations to support process studies (e.g., deployment of sediment traps to assay sediment flux, water column sampling to detect specific phytoplankton species, etc.).