How well does the Continuous Plankton Recorder (CPR) sample zooplankton? A comparison with the Longhurst Hardy Plankton Recorder (LHPR) in the northeast Atlantic

The Continuous Plankton Recorder (CPR) survey has collected data on basin- scale zooplankton abundance in the North Atlantic since the 1930s. These data have been used in many studies to elucidate seasonal patterns and long-term change in plankton populations, as well as more recently to validate ecosystem models. There has, however, been relatively little comparison of the data from the CPR with that from other samplers. In this study we compare zooplankton abundance estimated from the CPR in the northeast Atlantic with near-surface samples collected by a Longhurst-Hardy Plankton Recorder (LHPR) at Ocean Weather Station India (59 degree N, 19 degree W) between 1971 and 1975. Comparisons were made for six common copepods in the region: Acartia clausi, Calanus finmarchicus, Euchaeta norvegica, Metridia lucens, Oithona sp. and Pleuromamma robusta. Seasonal cycles based on CPR data were similar to those recorded by the LHPR. Differences in absolute abundances were apparent, however, with the CPR underestimating abundances by a factor of between 5 and 40, with the exception of A. clausi. Active avoidance by zooplankton is thought to be responsible. This avoidance is species specific, so that care must be taken describing communities, as the CPR emphasises those species that are preferentially caught, a problem common to many plankton samplers.

An increase in snake pipefish (Entelurus aequoreus) in the northeast Atlantic: possible causes and effects

Climate induced changes in the planktonic community have been reported in the North Atlantic in recent years (Beaugrand et al., 2002), and similar responses has been seen in higher trophic levels (eg fish, Brander et al., 2003). Many of these responses have been identified by the use of the Continuous Plankton Recorder (CPR), and here we discuss recent results from the survey concerning pipefish, numbers of which have increased dramatically around the UK in recent years. This has also been reported in both the scientific and popular press, and anecdotally by many divers. Pipefish are easily recognized, being vermiform with a long slender ‘snout’ and an armoured outer layer, much like an elongated seahorse. This increase has raised many questions, why has it happened and what affects will it have on the ecosystem?

Continuous Plankton Records - Phytoplankton Zooplankton And Environment Northeast Atlantic And North-Sea 1958-1980

Year-to-year fluctuations in the abundance of phytoplankton in the North-East Atlantic and the North Sea for the period 1958 to 1980 are described. Based on similarities between their annual fluctuations in abundance, the taxa may be divided into two groups, one of 12 species of diatoms and 1 species of Ceratium, the other of 5 species of Ceratium. The annual fluctuations in abundance of the Ceratium group is negatively correlated with a component of sea surface temperature (representing changes in the open ocean) and with the frequency of cyclonic weather over the United Kingdom. The Diatom group shows very similar annual fluctuations to those of most of the zooplankton species. Both groups show a high ·proportion of long wavelength variability in the form of a more less linear downward trend in abundance over the whole period. There is evidence to suggest that the high proportion of long wavelength variability shown by the zooplankton is influenced by inherent persistence in stocks from year-to year. The phytoplankton show little or no persistence. The close relationship between zooplankton and phytoplankton may, therefore, involve feed-back through nutrient recycling so influencing the annual levels of abundance of phytoplankton.