Water sampling devices range from a bucket dropped over the side of a ship to large water bottles sent thousands of meters toward the seafloor on a wire. Another technique involves placement of trays of sterilized sediment back on the deep-sea floor to study colonization rates and animal distribution. Bottom trawls, dredges, and coring devices are used to collect animals that live in or on the sediments and rock bottom. Many techniques developed by divers to handle fragile plankton have been redesigned for use with submersibles. These are maintained in aquaria in the ship's laboratory and studied at sea, as they cannot be grown or preserved intact. Some animals, such as gelatinous zooplankton, are collected by scuba divers, who gently place specimens in glass jars to avoid damaging their fragile bodies. In other techniques, a series of samples may be collected by a device at the small end of a single net, or a silhouette photographic system may take pictures of the animals collected. When the samples come aboard the ship, some may be examined immediately under microscopes in the ship's lab, animals may be dissected or analyzed for clues to their food sources or exposure to pollutants, and other samples may be preserved for further work in shore-based laboratories. The largest multiple opening-closing variety consists of a great metal frame carrying as many as 20 nets and an environmental sensing array that sends information back to the ship's laboratory, where biologists signal the nets to open in sequence as they observe temperature, depth, salinity, and other characteristics of the water column. The smaller ones, perhaps a meter long, may be towed briefly in near-surface waters. Some of the tools oceanographers employ are described here.Ĭollecting nets come in a wide array of sizes. At the same time, they must be very precise. They must mesh with ships' winches and cranes and be of a size and weight manageable on the wet, unsteady, windswept deck of a research vessel. Oceanographic tools must carry out their missions in corrosive seawater and under high pressure in the deep sea. Another approach is to create instruments or even automated laboratories to operate autonomously on the seafloor or in the water column. Since the ocean itself is not a convenient place to conduct research, scientists collect samples of water, sediment, flora, and fauna for study in laboratories aboard ship or ashore.
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