![]() This allows for accurate control over the location and timing of samples – crucial in plankton studies. ![]() The Multiple Opening/Closing Net and Environmental Sensing System has a live data stream, so an operator can control it from the ship. Buckets at the end of each net collect the zooplankton samples. Closing one net triggers the opening of the next one, so samples are fully sequential. This system of nine nets for zooplankton is towed by a metal frame in open water. Multiple Opening/Closing Net and Environmental Sensing System This unit also has sensors to measure temperature, salinity and depth of each sample. Nine nets with 1m² openings, attached to a stainless steel frame, can be opened and closed remotely. The MultiNet plankton sampler is a world-leading system for horizontal, oblique and vertical sample collections in successive water layers, down to depths of 3,000m. “Mammoth” MultiNet Multiple Plankton Sampler It can collect up to 100 discrete, sequential samples, producing high spatial resolution within the water column. The LHPR operates in combination with BAS’s custom-built down-wire net monitoring system to make sampling more accurate. Using the Longhurst-Hardy plankton recorder (LHPR), zooplankton can be sampled between two layers of gauze, from depths of up to 1,000m. Photographer: Sarah Chapman (BAS) Longhurst-Hardy plankton recorder Deploying Rectangular Mid-water Trawl (RMT8) on the James Clark Ross, 2015. The RRS Sir David Attenborough has a Down-Wire Net Monitoring System to communicate with and control the operation of plankton and trawl nets for krill and krill fishing. A custom-built support stand constructed at BAS means that the net and its frame be pre-assembled and kept in one piece during a cruise, facilitating and accelerating its deployment. Weighing nearly 1,000kg, the RMT25 can be unwieldy in rough conditions. It and is best suited for mesopelagic catching fish. The biggest RMT system (RMT25) has a mouth opening of 25 square metres, and a cod-end mesh size of 5mm. Its relatively small size means that it can be deployed in an efficient and targeted way, using acoustic information to guide the net to specific targets. It is best suited for catching macrozooplankton, particularly Antarctic krill. The mid-sized RMT (RMT8) has a mouth opening of eight square metres and mesh of 5mm. The smallest version of the RMT net system (RMT1) has a one square metre mouth opening, with 330 µm mesh and is mainly used to catch mesozooplankton. This pelagic trawl system is available in different configurations for specific scientific requirements. The RMT systems are are operated in combination with the down-wire net monitor system giving real-time control and also identifying the environmental conditions (temperature, salinity and depth) of the water where it is deployed. When deployed from the RRS Sir David Attenborough, the RMT can reach 2000m. This allows targeted sampling in specific swarms or water layers. The Rectangular midwater trawl (RMT) system consists of two nets of the same size, which can be opened and closed independently.
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