The temporal and spatial changes of zooplankton and chlorophyll a concentration were studied during the warm stratification period (early June) at three stations whose traits corresponded to the coastal, frontal, and offshore-dome water conditions described for the Catalan Sea. We sampled the stations for 12 days at a frequency ranging from less than 10 to 102 h, with a spatial resolution ranging from 10 to 104 m. The objective was to determine the variability of mesozooplankton and phytoplankton (chlorophyll a) biomass, and average individual size (mass) across a coast-offshore transect in relation to the stratification conditions prevailing in the NW Mediterranean during summer. The vertical distribution of phytoplankton biomass displayed a clear deep maximum at 60 m depth except at the coastal station. This maximum exists during most of the year and is especially important during the density stratification period. It was accompanied during daylight hours by a coherent zooplankton maximum. At sunset mesozooplankton ascended and dispersed, with larger organisms from deeper layers joining the migrating community and increasing the average individual mass. The highest variability of mesozooplankton biomass, individual mass and chlorophyll a concentration occurred at the front station due to the coupling between the vertical migration of zooplankton and the particular characteristics of the front. According to the data shown, the highest variability was observed at the lowest scales.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We are deeply grateful to Marta Estrada for her friendship, stimulating inspiration and collaboration over almost five decades. This paper is intended as a small homage to her kind and inspired leadership.
The VARIMED-95 cruise took place in the framework of the Spanish research project AMB94-1019 from the Ministry of Science to M. Alcaraz. Financial support was also provided by the projects MAR98-0854 and CTM2006-12344-c02 to M.A., TOPCOP-CTM2011-23480 to E. Saiz and FERMI (CGL2014-59227-R) to AC and ES. The authors are indebted to all the participants in the VARIMED-95 cruise, and to the crew of the RV Hespérides. This is a contribution of the Marine Zooplankton Ecology Research Group of the Generalitat de Catalunya (2014 SGR 498).