Abstract
Phytoplankton size structure, a major determinant of trophic structure and biogeochemical functioning in pelagic ecosystems, can be described by the slope of the size-abundance spectrum (SAS). Previous observational studies reporting spatio-temporal changes in phytoplankton SAS slope have focused on particular open-ocean or coastal environments. Therefore, the overall variability in phytoplankton SAS slope still has not been investigated over wide ranges of biomass and productivity including both oligotrophic open-ocean regions and productive coastal waters. Here we present a multi-cruise overview of the basin-scale variability in phytoplankton biomass and SAS slope across the Atlantic Ocean, covering coastal, shelf, and oceanic environments over the 50°N-50°S latitude range. We find the inverse relationship between cell size and abundance to be pervasive across the studied regions, even in highly productive coastal waters. In oceanic regions, consistent latitudinal patterns are observed in the relationship between nutricline depth, phytoplankton biomass and SAS slope. There is a strong degree of covariation between SAS slope at the surface and at the base of the euphotic layer, indicating that geographical changes in phytoplankton size structure override vertical variability. A basin-scale relationship exists between increasing resource supply, enhanced phytoplankton biomass, and progressively less steep SAS slopes, reflecting increasing importance of large cells in more productive waters. However, the relationship between ecosystem productivity and both SAS slope and mean community cell size is saturating, which means there is no continuous trend towards ever increasing contribution by larger cells. Similar phytoplankton size structures, with a biomass dominance by the 2–20 μm size class, are found in both moderately and highly eutrophic waters. Our results provide an observational benchmark for testing the predictions of size-based plankton models and for assessing future, climate-related shifts in phytoplankton size structure in both coastal and oceanic regions of the Atlantic Ocean.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 103104 |
| Journal | Progress in Oceanography |
| Volume | 217 |
| DOIs | |
| State | Published - Aug 8 2023 |
Bibliographical note
KAUST Repository Item: Exported on 2023-09-14Acknowledgements: We thank all the researchers who contributed to the collection and analysis of samples and data as well as the captain and crew of all oceanographic vessels involved in the different surveys and programs. This research was supported by the European Union through H2020 TRIATLAS project ‘Tropical and South Atlantic climate-based marine ecosystem predictions for sustainable management’ (Grant agreement No. 817578) and by the Spanish Ministry of Science and Innovation through research grants CTM2008-03699, CSD2008-00077, CTM2004-05174-C02 and REN2000-1248. The Atlantic Meridional Transect is funded by the UK Natural Environment Research Council through its National Capability Long-term Single Centre Science Programme, Climate Linked Atlantic Sector Science (grant number NE/R015953/1). This study contributes to the international IMBeR project and is contribution number 388 of the AMT programme. The RADIALES program is supported by Instituto Español de Oceanografía (Spain) and additional funds from Xunta de Galicia (Spain) through grant IN607A2022-05. The ACEx/SIMTECO cruise was supported by the Brazilian National Council for Scientific and Technological Development (CNPq, grant 558108/2009-1) and the Funding Authority for Studies and Projects (FINEP). The PATEX cruise was supported by the Brazilian National Council for Scientific and Technological Development (CNPq, grant 520189/ 2006-0). The Abraços 2 cruise was funded by the the French oceanographic fleet.
ASJC Scopus subject areas
- Aquatic Science
- Geology