University of Delaware professor George Luther has made a career studying chemical reactions in the marine environment.

He has explored chemical reactions in the Black Sea and in Delaware's Inland Bays; sampled hydrothermal vents at the top of Yellowstone and at the bottom of the ocean; and investigated ocean and coastal waters in the St. Lawrence Estuary in Canada.

Last week Luther was aboard the R/V Hugh R. Sharp, UD’s 146-foot flagship research vessel, to get a better grasp on the manganese cycle at work in the Chesapeake Bay.

Manganese is a trace nutrient important to the growth of humans, plants and animals. In humans, manganese helps aid digestion. In plants, it is the key metal involved in forming oxygen during photosynthesis. It is also crucial to the growth and survival of marine organisms.

“Without the manganese cycle, toxic hydrogen sulfide would get closer to the water’s surface, which could wreak havoc on fish and crabs,” explains Luther, the Maxwell P. and Mildred H. Harrington Professor of Oceanography in the College of Earth, Ocean, and Environment. “If sulfide found its way into a person’s bloodstream, it would attack the iron in hemoglobin and affect the individual’s ability to breathe. The same would be true for many marine organisms if hydrogen sulfide were closer to the water’s surface.”

A laboratory that floats

So, how do scientists measure things like manganese in the marine environment?

In years past, scientists would take water samples at sea and then return to land to analyze the samples in the laboratory. Today, research vessels like the R/V Sharp enable scientists to do their work aboard ship on the ocean.

Like any other UD lab, the R/V Sharp is outfitted with the latest scientific technology for research. There are sonars, current profilers and instruments for testing water column chemistry, salinity, temperature and pressure.

Operated by UD personnel, the ship’s modular design can support a wide range of marine disciplines including chemical, geological, physical and biological sciences, as well as acoustics, fisheries and marine mammal research.

UD's R/V Hugh Sharp and the predecessor vessel R/V Cape Henlopen have been long-term members of the UNOLS (University National Oceanographic Laboratory System) fleet, supporting key agency and university oceanographic research.

UNOLS is a regional class of vessels capable of research serving the East and Gulf Coasts: locally, as far east as the Bahamas, as far south as the Gulf of Mexico and as far north as the Canadian border. The R/V Sharp can remain at sea for up to 14 days and can accommodate up to 14 scientists and their equipment — everything from autonomous underwater vehicles to acoustic sensors to coring devices for taking mud samples at the seafloor.

Marine technicians manage the scientific equipment onboard and act as liaisons between the scientists and crew to ensure the science is properly integrated and the cruise mission accomplished.

“The R/V Sharp can do almost anything a larger ship can do except operate large remotely operated vehicles (ROVs) and the deep-sea submersible Alvin. It’s a good size for coastal and bay work and offers high maneuverability, excellent deck space and an exceptional crew,” says Luther.

On the Chesapeake Bay and beyond

For Luther’s Chesapeake Bay study, water was pumped onboard the ship from various depths so his research team could measure oxygen, sulfide, manganese and other chemical species while instruments aboard the R/V Sharp collected salinity, temperature, turbidity and fluorescence (a proxy for chlorophyll) measurements. Luther is trying to understand the chemistry that occurs in narrow zones of the water, particularly what different chemical species of manganese and manganese-associated bacteria are present.

“There is a gradient where organisms and chemistry occur together. We have evidence that that manganese is bound to organic compounds (humic material that gives a yellow color to the water) that come from decaying plants. An engineering colleague, Dr. Yo Chin, and his student will help us analyze what’s happening with these humic materials at the molecular level,” he explains.

The research has application locally and in major ocean basins like the Arabian Sea or Black Sea.

“The same chemistry happens in these similar systems but the concentrations are typically higher in the Chesapeake Bay, making it easier to make measurements without contamination,” says Luther.

Other institutions and scientists use the R/V Sharp, too. Recent projects include work with the National Oceanic and Atmospheric Administration’s Northeast Fisheries Science Center to study the health of the sea scallop population, an annual project since 2008.

A major part of that science mission was towing a high-definition video camera to capture footage of the scallop population, along with other data, for the Northeast Fisheries Council. The ship’s high-definition fiber optic cable made it possible to stream the video so researchers could assess the population on-site, then use the data to inform catch limits and other important policies.

In July, the ship’s dynamic positioning capability landed the crew in the Gulf of Mexico with Office of Naval Research-funded researchers. Dynamic positioning is like a computerized autopilot that automatically monitors wind and current conditions, while electric motors housed in watertight pods beneath the stern hold the ship’s position. The pods can rotate 360 degrees and turn at different speeds enabling the captain to steer the vessel with precise movements. The ability to remain in position without drifting is helpful for a variety of reasons.

“In the ONR project, we needed to place large equipment in a grid formation on the seafloor so scientific divers could do their work, but it also helps ensure collected samples reflect a single vertical profile from one location in the water column like in George Luther’s work,” says Jon Swallow, director of marine operations in the School of Marine Science and Policy. “It is a capability that not a lot of other vessels offer.”

Staying on the leading-edge

The R/V Sharp crew spend approximately 180-190 days at sea (from March through November). Off-season projects include maintenance and modernizing the R/V Sharp to keep pace with technology advances and customer needs.

This winter, Swallow will upgrade the vessel’s dynamic positioning system and prepare for a mid-life maintenance overhaul. His first step will be to talk with scientists about what lab capabilities they need most.

But today Swallow has other things on his mind, like planning for the crew’s next mission to conduct research related to sea level rise in South Carolina with U.S. Geological Survey scientists.