Continuous Plankton Recorder

Background

Larval decapod (Image:Anita Slotwinski/TAFI)

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.

 

Drifting Barometers of Change

The ocean teems with microscopic drifting primary producers. These are phytoplankton, and they are grazed by microscopic animals known as zooplankton.

Through photosynthesis, phytoplankton produce half of the world oxygen and support most marine life. Zooplankton include krill, copepods and young stages of crabs, lobsters, squid and most fish. They provide food for a multitude of creatures including fish, penguins, whales and turtles.

Plankton are short-lived and respond rapidly to changes in ocean conditions. This makes them valuable sentinels of environmental change such as global warming. Measurements of plankton diversity and distribution over time provide a baseline for detecting impacts of climate change at the base of the ocean food web.

Sir Alister Hardy deploying one of the first CPR instruments

 

History of the Continuous Plankton Recorder

On the Discovery expedition of the Antarctic in 1926, Sir Alister Hardy collected continuous records of phyto and zooplankton abundance that dramatically showed the patchiness of plankton in the Southern Ocean. He called the new sampling device the “Continuous Plankton Recorder” and it remains in use and virtually unchanged to this day. This robust and durable device is towed near the ocean surface over extended transects (100s-1000s km), collecting plankton on a filtering silk.

The AusCPR survey builds on the success of the ‘mother’ CPR survey run by the Sir Alister Hardy Foundation for Ocean Science (SAHFOS) based in Plymouth, and also on the success of the SO-CPR Survey led by Australia. The SAHFOS marine monitoring program has been collecting data in the North Atlantic and North Sea on the ecology and biogeography of plankton since 1931, and is one of the longest biological marine time series in the world. The unique marine biological dataset has provided a wide range of ecological indicators. These have been used by scientists and policy makers to address marine environmental management issues such as harmful algal blooms, eutrophication and pollution, climate change and fisheries. SAHFOS has successfully collected and archived over 220,000 plankton samples since 1946 in the North Sea and North Atlantic Ocean through this practical and cost-effective technology. Similarly, the SO-CPR Survey has collected over 30,000 samples.  Data are being using for research, conservation and management purposes, such as the bioregionalistion of Southern Ocean.

Ships of Opportunity

The strength of the CPR lies in its unique ability to collect samples frequently over large spatial scales. This is possible because the CPR is a simple, robust device that can be towed behind ships of opportunity (SOOPs) on their normal trading routes at their conventional operating speeds, usually 15–20 knots, unaccompanied by research staff. Other large-scale surveys are often conducted as part of fish stock surveys (because of cost constraints) and are thus usually conducted annually, whereas samples that are collected frequently (weekly– monthly) are usually point samples taken close to the coast where they are subject to local coastal processes. Sampling from SOOPs is so cost effective that it is now spawning new satellite surveys.

 
Other CPR Surveys

In addition to the 'mother' North Atlantic CPR survey (pictured below) and the AusCPR survey, there are 3 other CPR surveys: viz. North Pacific, Northwest Atlantic and Southern Ocean. The North Pacific survey, operated from the Sir Alister Hardy Foundation for Ocean Science (SAHFOS) in the UK, has been running since 2000 and samples down the west coast of Canada and the US, and between the US and Japan. The Northwest Atlantic survey is operated by the Northeast Fisheries Science Center (NEFSC) USA and runs down the east coast of USA and has been operating since 1977. The Southern Ocean CPR survey has been run by the Australian Antarctic Division since 1991 (below). This survey tows mainly during the early spring to late autumn (September-April) in the Southern Ocean when research and supply vessels are operating. Occasional tows are conducted in winter when the opportunity arises.

Spatial coverage of the CPR survey over the past 65 years in the North Atlantic (Map:Anthony Richardson/SAHFOS)
CPR coverage in the Southern Ocean (Map:AAD)