90 years ago, the first CPR tows were performed to enable plankton forecasting, to benefit the economic performance of the North Sea fishery. There was no expectation that tows would continue for decades but the unique longevity of the survey is testament of its value to the scientific and policy communities, providing a basin-wide and long-term measure of the ecological health of marine plankton.
Despite a trend of increased tow vessel size and speed, the CPR has proven itself robust and reliable. Able to be deployed at up to 25 knots in rough seas, it has towed in all of the worlds’ oceans by container ships, passenger ferries, fishing boats and sailing vessels, sampling to date over 7 million nautical miles. More than 60 years of consistent methodology offers a unique tool to the scientific community and has helped produce over 1000 publications in peer-reviewed journals.
The CPR device is a self-contained plankton sampler that does not require power from the towing vessel. The robust and mechanically simple design means it can be deployed from most vessels whilst underway, minimising inconvenience for the shipping community.
The CPR Survey uses Ships of Opportunity (SOOPs) to tow CPRs, utilising existing SOOP routes and schedules. Whilst a CPR can easily be deployed behind Research Vessels, using SOOPs means that no additional ship journeys, and therefore CO2 emissions, are required. The CPR Survey has historically operated along numerous shipping routes, on a monthly basis, giving a consistent methodology across the time series. The CPR Survey is part of the SOOP Implementation Panel (SOOP-IP), part of the Global Ocean Observing System (GOOS), working with partners around the world to better coordinate our observations of the world’s oceans.
The CPR device itself has a payload area, and can successfully incorporate a number of instrumentation packages – allowing in-situ physical / chemical parameters alongside the biological data, and using the network of vessels to sample at basin scales. However, the concept of attaching sensors to the CPR is not new, starting in 1964 with the addition of a mechanical thermograph (illuminated thermometer + photographic film geared to the CPR impellor). Temperature, conductivity, depth, chlorophyll, turbidity, pitch, roll, vibration, acceleration and light intensity have been measured using the CPR as a platform over the years, but never positioned at the heart of the CPR survey. The iCPR project intends to enhance the capabilities of the CPR by offering a flexible, comprehensive and robust solution in terms of global monitoring. Using the iCPR sampler alongside a new set of procedures and technologies, the iCPR project will bring a large variety of new data (e.g. in-situ images, environmental parameters, CPR behaviour, etc.) and integrate them into the CPR data collection started more than 60 years ago.
Additionally digital holography opens up new possibilities in terms of data acquisition. Total depth-of-field, fine resolution and good performance at high water velocities allows for in-situ particle imaging without disrupting the standard operating methodology of the CPR. Identification of particles poorly retained (or destroyed) by the CPR and analysis using specific AI algorithms for rapid assessment of particle images are some of the aims of the iCPR project.
In addition to the new sensory capabilities of the iCPR system, the iCPR project will be enhanced by the integration of more information about the oceans and new computational techniques. These include incorporating oceanographic variables and information about species functional traits into the analysis, AI-based image processing, and the use of timescale-specific approaches and machine learning to process and interpret our data. In this way we enhance our understanding of the past and present state of the plankton community without impacting the consistency and continuity of regular CPR sampling.