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Continuous Plankton Recorder cassette

Date1930s

Object number00056042

NameConstant Plankton Recorder

MediumMetal, silk

ClassificationsTools and equipment

Credit LineAustralian National Maritime Museum Collection Gift from CSIRO, Oceans and Atmosphere

Terms

DescriptionThis Continuous Plankton Recorder (CPR) cassette is donated to the museum by CSIRO, along with a CPR body (of earlier vintage) and a larval sampler. The CPR is generally towed behind a ship at a depth of 10 m. Water passes through a narrow aperture at the front of the CPR body, plankton are filtered onto a slow-moving band of silk and covered by a second silk. The silks and plankton are then spooled into a storage tank containing formalin to preserve the plankton for later identification. On return to the laboratory, the silks are removed from the mechanism and divided into sections representing 10 nautical miles (19 km) of tow. Two different techniques are used needed to assess the plankton content: • a ‘greenness index’ is used to estimate phytoplankton (photosynthesising plankton) biomass by comparing the greenness of the silk against a standard colour chart. This relates to the level of green staining from the chlorophyll pigments in the phytoplankton and allows fragments and small phytoplankton to be included in biomass estimates. • microscopic analysis is used to count and identify zooplankton (animal plankton) and phytoplankton to species level where possible. These data can then be related to environmental data collected during the tows, such as location, water temperature, salinity, and climate data. The Continuous Plankton Recorder (CPR) Survey is the longest running marine biological survey in the world and provides plankton-recovered data on a pan-oceanic scale. It was started in 1931 by Sir Alister Hardy and Sir Cyril Lucas. Sir Hardy also designed the first CPR. The Australian Continuous Plankton Recorder (AusCPR) survey measures plankton communities as a guide to the health of Australia’s oceans. It is part of the Ships of Opportunity Facility in Australia’s Integrated Marine Observing System and is jointly operated by CSIRO Marine and Atmospheric Research (CMAR) and the Australian Antarctic Division (AAD). SignificanceOrginally designed by Sir Alister Hardy in the 1930s for collection of plankton within the water column, it is such an excellent intiial design that it has hardly changed in over 100 years. Rather than spot net sampling, which can be inaccurate due to the unique patchy distribution and behaviour of plankton, the CPR is towed behind a ship and gathers samples continuously for up to 500 nautical miles. Between 1990 and 1995, the Australian Antarctic Division (AAD) took Hardy’s original design and slightly modified it, creating a Type II version that, while essentially very similar to Hardy’s original design, is more streamlined, built from marine-grade stainless steel (rather than phosphor bronze) and has an easier reload mechanism.

The IMOS Australian Plankton Survey is an incredibly important intiative in our understanding of Australian zooplankton. Australia has few zooplankton time series. Globally there are zooplankton times series spanning more than 15 years in no fewer than 30 countries, including many relatively small and developing nations. The longest ongoing times series in Australia is 2 years. Given its diversity of marine habitats and the economic and social importance of fishing, Australia is impoverished in long-term zooplankton datasets. The AusCPR project will help redress this situation by providing estimates of plankton abundance monthly along the east coast of Australia and complemented by the tows between Australia and Antarctica. AusCPR was initially supported by the Sir Alister Hardy Foundation for Ocean Science (SAHFOS), who since 1931 have run the largest plankton monitoring program in the world.