Technology grant promises new dimension for oxygen studies

A team of VIMS researchers has received a $200,000 technology-development grant to enhance the capabilities of Acrobat, a towed instrument platform that they use to map oxygen-poor waters in Chesapeake Bay.

Drs. Larry Haas, Iris Anderson, and Howard Kator have been using the small winged vehicle for several years to generate two-dimensional profiles of oxygen concentrations and other water-quality measures in the York River and other Bay tributaries. Drs. Jian Shen and Mark Brush have also recently joined the team.

The new grant will allow the researchers to test and refine the software needed to add a third dimension to their studies. Three-dimensional maps are crucial for accurately calculating the volume of dissolved oxygen (DO) in a tributary or the Bay.

"DO volumes are becoming a key metric for monitoring water quality," says Haas. "The ability to process and display data in 3-D rather than 2-D will give us a much better picture of fine-scale oxygen variations in areas like the lower York and Rappahannock rivers, and thus allow us to calculate the volume of water below a selected dissolved-oxygen value."

All higher life forms in Chesapeake Bay need dissolved oxygen to survive. "Dead zones," marine areas with insufficient oxygen for undersea life, are increasing due to excess nutrients that ultimately rob waters of oxygen. About 150 such zones now exist in coastal waters worldwide, including the main-stem of Chesapeake Bay and its tributaries.

The grant will also allow the researchers to develop the technology needed to outfit Acrobat with miniature water samplers. Laboratory analysis of samples collected at different sites and depths will allow the team to calibrate or verify the data from Acrobat's electronic sensors.

"Right now, Acrobat records dissolved-oxygen levels in the river using electronic sensors," explains Haas. "By collecting water samples we can measure dissolved oxygen directly. That will allow us to ground-truth the electronic signals."

The ability to collect discrete water samples at specific locations in the water column while underway will allow calibration of other data parameters as well, including chlorophyll. Chlorophyll readings indicate the amount of photosynthesis and plant growth in an area. Dead zones form when marine plants within nutrient-fueled blooms die, sink to the bottom, and are consumed by marine bacteria (a process that uses oxygen).

Outfitting Acrobat with water samplers will pose a significant engineering challenge. Researchers deploy the instrument platform by towing it behind a moving research vessel, where it undulates through the water column like a porpoise. Adding external equipment will disturb the instrument’s flight capabilities.

The team is working with Acrobat developer Sea Sciences Inc. to minimize those effects by testing the device in a water flume. "It's the marine equivalent of testing an airplane in a wind tunnel," says Haas.

The grant is one of twelve development projects for environmental technology funded by the Cooperative Institute of Coastal and Estuarine Environmental Technology (CICEET) during fiscal year 2005. A partnership of the University of New Hampshire and NOAA, CICEET fosters the development of tools for clean water and healthy coastal habitats nationwide.

All research projects will take place at National Estuarine Research Reserve System (NERRS) sites around the U.S. The Acrobat study areas in the York River lie adjacent to four reserve sites managed by the Chesapeake Bay National Estuarine Research Reserve (CBNERRVA) program at VIMS.