Technology Solutions - ACS Publications - American Chemical Society

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Technology▼Solutions Technologies converge to make integrated ocean observing system a reality Thanks to recent advances in sensor technologies, high-speed data telemetry, computational power, and modeling, ocean scientists agree that their long-held goal of creating an international ocean observing system is moving within reach—together with the funding crucial for bringing it to fruition within the next 2–10 years. Such a system would collect boatloads of valuable data for environmental scientists, including crucial information about the ocean’s primary production and anthropogenic inputs to the world’s fragile coastal ecosystems. The integrated ocean observing system (IOOS) envisioned by researchers and federal agencies will couple the existing data-gathering systems—sparse and sporadic ship voyages, moored and floating buoys, and remote surveillance by satellites and planes—with new fiber-optic and power cable grids on the seafloor equipped with numerous instrument nodes. Fleets of autonomous underwater vehicles (AUVs), some docked at grid nodes for easy deployment, will serve as mobile instrument platforms to follow transient phenomena and gather data as directed by scientists ashore. A new highbandwidth computer network will assimilate near-real-time data from all sources and make it available to researchers and the public. Such a glorious vision has few detractors. “Everyone agrees we should be measuring everything,” says Margaret McManus, an oceanography professor at the University of Hawaii and an IOOS planner. But, McManus adds, “financially and logistically, there is [only] a handful” of critical variables for which autonomous instrumentation is already operational. Most of these are aimed at physical and chemical properties, such as the land-based high-frequency radar arrays used to study surface currents and the standard conductivity, tem-

perature, and depth (CTD) samplers that are deployed in many moored and floating buoys. However, instruments in various stages of development promise to unlock complex biological interactions. IOOS planning is divided between the federal interagency coordinating body known as Ocean.US and the National Science Foundation’s Ocean Research Interactive Observatory Networks (ORION). In particular, researchers would like to monitor the composition of the oceans’ plankton population, which includes all the small plant and animal organisms that float or drift in salt water. The phytoplankton, or photosynthesizing algae, that serve as the primary producers in the food web are a key component of the plankton, especially because some are the source of dangerous toxins during harmful algal blooms (HABs). Plankton also includes viruses, bacteria, and the larvae of fish, mollusks, and crustaceans. Knowing phytoplankton’s role in the carbon cycle will help illuminate the mechanisms of climate change, including increasing oceanic CO2, which is expected to acidify marine environments with unknown biological consequences. The standard laboratory method for pinpointing plankton species, which requires an expert to visually examine a water sample under a microscope, is a timeconsuming and expensive process. To make this analysis autonomous, the Dutch company Cytobuoy developed a portable flow cytometer that can be used in the lab, aboard ship, on a mooring, or on an AUV or mini-sub, although it does not yet have satellite transmission capability. The instrument exposes a water sample to a light source to detect the presence of chlorophyll a (present in all phytoplankton) and phycobilins (pigments made only by blue-green and red algae). It also

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uses forward and side-scattering laser beams to determine the size and shape of each cell. These results don’t identify phytoplankton by species but do indicate which groups are present in the water and give approximate concentrations. Being able to track nutrient availability would also be useful in understanding the effects on phytoplankton of natural cycles, such as cold water upwelling events, and anthropogenic inputs, such as fertilizer runoff and sewage effluent. Nitrate levels in particular are increasing and may contribute to HABs. A new nitrate analyzer developed by the Monterey Bay Aquarium Research Institute (MBARI) and Satlantic, a Nova Scotia company (Environ. Sci. Technol. 2002, 36, 344A) uses a UV spectrophotometer to determine the anion. Most of the nutrient sensors developed to date measure only one nutrient at a time, but regulatory agencies must sample a range of chemicals. One potential solution is a four-nutrient (nitrate, phosphate, silicate, and ammonia) analyzer made by ECOLab, which is being used to complement flow cytometry data, according to Al Marchi, a research technician at San Francisco State University’s Dugdale/ Wilkerson Laboratory for Biological Oceanography in Tiburon, Calif. Even more precise fingering of species is on its way. Chris Scholin at MBARI is developing a probe called the Environmental Sample Processor (ESP) to identify and quantify a variety of organisms, including phytoplankton that produce HABs, the larvae of invasive species such as the Asian crab Musculista senhousia, and microbes pathogenic to humans and farmed fish. The ESP extracts ribosomal RNA from organisms in a water sample and then exposes the extracted sequences to an array of unique, complementary probes. If any species included on the ESP are present in the sample, a chemiluminescent reaction will identify it. The ESP is not yet deployable for long periods as part of an IOOS. It © 2004 American Chemical Society

NEPTUNE

Node locations Fiber-optic cable Exclusive economic zone boundaries Fault lines Spreading centers Subduction zone

The first new component of the Integrated Ocean Observing System that ocean researchers hope to put in place will be the NorthEast Pacific Time-series Undersea Networked Experiments (NEPTUNE) system, a joint U.S.–Canadian project to cover a 500–1000 kilometer chunk of the Pacific Ocean with an electrooptical network and instrumentation to study plate tectonics, biological processes, and wave and tide actions. NEPTUNE planners expect to lay down the first cable next year.

can’t analyze plankton species and their toxins in the same array, and issues related to depressurization of the water sample inside the instrument would need to be resolved for it to function below 50 meters. As Scholin says, “There is a huge gulf between taking very sophisticated analytical equipment operated by highly trained scientists” and making it “much smaller than a breadbox, the size of a softball inside a can that’s underwater operating on batteries.” Because water is opaque to radar and light is limited below the surface, acoustic technologies take on great

importance. Acoustic multifrequency backscattering techniques prove useful in studying zooplankton distributions. Emerging research suggests that recently discovered thin layers in the ocean—vertically thin strata that can extend for miles—are a crucial habitat for all kinds of plankton from bacteria to fish larvae. Research by Van Holliday of BAE Systems indicates that upwards of 75% of zooplankton concentrate in layers less than a meter thick. McManus, who is studying these thin layers with colleagues from the University of Rhode Island and BAE Systems, uses a multifrequency acous-

tical profiling system developed by BAE Systems that generates sound at wavelengths from 265 to 1000 kilohertz. Calculations applied to the returning reflections give an idea of the density of organisms at centimeterscale resolutions, McManus adds. The instruments are placed at a maximum depth of 20 meters to look upwards at the thin layers that are 5–10 meters below the surface. McManus says she has made limited two-and-a-half-month in situ deployments of acoustical profilers in a near-shore environment. “Hopefully in 10 years we’ll be able to have them deployed everywhere,” McManus says. Data and power transmission methods taken for granted in land, air, and even space encounter daunting obstacles underwater. “If I put an instrument 10 miles away in Monterey Bay, it is more remote in a communication sense than the Mars rovers are,” says Jim Bellingham, director of engineering at MBARI. Problems with power, pressure, and sea creatures can scuttle almost any technology. Cabling and instruments are vulnerable to biofouling, both from microbes and larger animals. “It’s not unusual for parrotfish to chew through the cables and starfish, who are used to breaking up bivalves, to pry apart the equipment,” says Richard Jahnke, a chemical oceanographer at the Skidaway Institute of Oceanography in Savannah, Ga. Waves and currents interfere with measurements and tear instruments from their moorings. Unless remotely deployed instruments are coupled to power and fiber-optic cables, electricity must come from batteries or solar cells (Environ. Sci. Technol. 2001, 35, 11A–12A) and instruments must transmit their data by satellite, radio, or cell phone, necessitating periodic surfacing to download and regenerate. Pressure is also a factor. As Jahnke observes, “There’s only a 1-atmosphere pressure change between Earth and outer space,” but between the surface and the ocean floor, there can be differences of 400–500 atmospheres. Consequently, only a “subset of the electronics” usable on land “will work in the ocean,” says Bellingham. For example, light-emitting diodes that include air bubbles will be crushed. Despite the challenges, IOOS plans proceed apace, with funds included in the 2006 budget of the U.S. federal government. —VALERIE BROWN

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