Top-down and bottom-up control of phytoplankton on a mid-latitude continental shelf ecosystem

It is widely accepted that ecosystems are subject to both, resource-driven (bottom-up) and predation-driven (top-down) controls. However, it is very frequent that the control of the structure and dynamics of marine phytoplankton is associated only with the availability of resources, despite the fact that top-down control has been identified as an important factor in shaping marine phytoplankton patterns. This is the case of the studies carried out in the Gulf of Cadiz, which has generally been approached from a resource control perspective, without including predation by zooplankton as a forcing element on phytoplankton. This work makes a first attempt to the study of the combined bottom-up and top-down controls of phytoplankton in the Gulf of Cádiz and aims to test their relative influence on the variance of phytoplankton biomass. For this purpose, monthly samples of chlorophyll-a, mesozooplankton and environmental variables determining phytoplankton growth were taken during six years. We found that the top-down control had more relative weight on the variance of phytoplankton biomass for the continental shelf as a whole. Resource availability (i.e. bottom-up control) determined phytoplankton growth rate although grazing (i.e., top-down control) determined the maximum chlorophyll values in the studied region. Henceforth, our results indicate that considering the top-down control is necessary to understand phytoplankton dynamics in the continental shelf of the Gulf of Cadiz

RODRÍGUEZ-GÁLVEZ Susana;  MACIAS MOY Diego;  PRIETO Laura;  RUIZ Javier; 

2023-08-31

PERGAMON-ELSEVIER SCIENCE LTD

JRC133515

0079-6611 (online),   

https://www.sciencedirect.com/science/article/pii/S007966112300126X,    https://publications.jrc.ec.europa.eu/repository/handle/JRC133515,   

10.1016/j.pocean.2023.103083 (online),