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.

Development and validation of a molecular technique for the analysis of archived formalin-preserved phytoplankton samples permits retrospective assessment of Emiliania huxleyi communities

The coccolithophores, particularly the species Emiliania huxleyi (Lohmann) Hay & Mohler, account for the bulk of global calcium carbonate production and as such play a fundamental role in global CO2 cycling and the carbonate chemistry of the oceans. To evaluate the response of this functional group to the effects of climate change, we undertook a feasibility study to determine whether a retrospective approach could be used on archived coccolithophore datasets. We demonstrate for the first time a technique for the extraction of E. huxleyi nucleic acids from archived formalin-fixed samples of the long-term Continuous Plankton Recorder. Molecular analysis of a nine year old formalin-fixed sample reveals the presence of a diverse population of E. huxleyi genotypes within a developing coccolithophore bloom. In addition, E. huxleyi sequences were amplified from a number of formalin-fixed samples, the earliest of which was collected in August 1972. This molecular assay promises the possibility of studying global variations in the distribution and genetic make-up of E. huxleyi communities over extensive periods of time. (c) 2008 Elsevier B.V. All rights reserved.