Copepod distribution in surface water from Drake Passage using Continuous Plankton Recorder and a Pump-Net onboard system

THOMPSON, GUSTAVO; DINOFRIO ESTELA; ALDER VIVIANA; TAKAHASHI, KUNIO; HOSIE, GRAHAM

BRAZILIAN JOURNAL OF OCEANOGRAPHY

INST OCEANOGRAFICO

Lugar: São Paulo; Año: 2012 vol. 60 p. 367 - 380

1679-8759

There is no single instrument that can sample quantitatively the complete spectrum of pelagic organisms, or even all the components of zooplankton. Mesh size is the main factor affecting species selectivity in the Continuous Plankton Recorder (CPR), implying a need to use multiple net systems to fully characterize a community. Here, we studied the spatial distribution of copepod communities in the water masses of the western and eastern sectors of Drake Passage, using a CPR and a Pump Net onboard system respectively. For this purpose, and assuming that copepod community size structures of each of the three water masses were similar in both sectors studied, we evaluated the possibility of complementing CPR results using a Pump-Net onboard system. The latter system allows the estimation of absolute abundances and has the advantage of solving two problems associated with CPR, namely mesh clogging and low catching efficiency. The contribution of the nauplius forms and species accurately identified with both samplers was analyzed. Although Oithona similis dominated both communities, in the western sector, small species had a higher contribution than Calanus simillimus, while the opposite was true for the eastern sector. Nauplii and early copepodite stages of O. similis were missing in CPR samples and represented between 69-79% of total copepod communities, whereas small calanoid copepods, C. simillimus copepodites and later stages of O. similis were inaccurately sampled by the CPR and represented between 14-18% of the copepod community. Hence, the pump net sampler is useful for complementing the semi quantitative information from the CPR and for its calibration.