https://orcid.org/0000-0003-1793-8444
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Abstract
The changes within and between seasons in phytoplankton composition and abundance determine the carbon biomass available for upper levels of the food web. Temporal changes in phytoplankton community and environmental parameters in a port in Puerto Madryn, Southwest Atlantic were analysed. During an annual period (2011–2012), samples of surface seawater were collected approximately monthly. We determined phytoplankton community structure (species composition and abundance) and biomass (determined by carbon content and chlorophyll a (Chl a)). Water temperature, salinity and transparency were measured when sampling the surface water and local meteorological data were considered. The main groups observed were diatoms (Bacillariophyta; the most abundant during the concentration peaks of Chl a), dinoflagellates (Dinophyta) and flagellates, which mainly included species of Cryptophyta and Chlorophyta. Diatoms exhibited blooms in March (summer–autumn) and September (spring), represented by Skeletonema costatum and Pseudo-nitzschia spp. respectively. Dinoflagellates contributed to the highest carbon biomass, with peaks in January (summer) and April (autumn), exemplified by Prorocentrum micans and Scrippsiella acuminata, respectively. Temporal differences in community composition were related to the seasonal changes in temperature, solar irradiance, precipitation, salinity and wind velocity. The environmental conditions seem not only to determine the species composition but also cell size distribution: nanoplanktonic (≤ 20 µm) species dominated mainly during late spring, summer and early winter while microplanktonic species (> 20 µm) during late winter and early spring. Our results showed within-season changes and show that not only Chl a, but also carbon content can be considered, as the former is a biased estimator of phytoplankton biomass. This study provides the first seasonally resolved estimation in the area of the carbon biomass available for upper levels of the food web and a necessary information for future scenarios prediction.
HIGHLIGHTS• Two diatom blooms were followed by an increase in dinoflagellate abundance.• Annual environmental conditions drive the phytoplankton community structure.• First seasonally estimation of autotrophic biomass availability for Patagonian trophic web.
Acknowledgements
We would like to thank the CONICET-CENPAT Laboratorio de Climatología for providing the meteorological data. We also thank Néstor Ortiz, Fabián Quiroga and Ricardo Vera (CONICET-CENPAT) for diving and field assistance. We are grateful to Beatriz Beker and Gaspard Delebecq for their advice on the identification of some species. We are also grateful to Instituto Nacional del Agua (INA-CIRSA, Córdoba) and Instituto Antártico Argentino (IAA, Buenos Aires) for providing laboratory space and equipment. We thank the two anonymous reviewers and editor for the comments that helped to improve the manuscript.
Disclosure statement
No potential conflict of interest was reported by the authors.
Supplementary information
The following supplementary material is accessible via the Supplementary Content tab on the article’s online page at https://doi.org/10.1080/09670262.2021.1995630
Supplementary table S1. Environmental conditions during the study period from October 2011 to September 2012 in Almirante Storni Port, Nuevo Gulf (Argentina).
Supplementary table S2. Mean and standard deviation of the abundance of phytoplankton cells, carbon biomass and chlorophyll a (Chl a) registered in this study together with the cell abundance and Chl a registered in previous studies from Santinelli (Citation2008) and D’Agostino et al. (Citation2018) in Nuevo Gulf (Argentina).
Supplementary table S3. Raw data of measured Chlorophyll a in each sample replicate and the corresponding monthly mean and standard deviation from October 2011 to September 2012, in Almirante Storni Port, Nuevo Gulf (Argentina).
Supplementary table S4. Raw data of all sample replicates with cells abundance, carbon biomass and size class (micro and nano plankton) by species/morphotype. Species/morphotype mean volume and the estimated carbon biomass are detailed.
Supplementary table S5. Phytoplankton taxa identified from October 2011 to September 2012, in Almirante Storni Port, Nuevo Gulf (Argentina). (*) taxa with low abundance included as “Other diatoms”, “Other dinoflagellates” or “Other flagellates” in figures and statistical analyses.
Supplementary figure S1. Temporal variation in abundance contribution (percentage) of taxonomic groups, differentiating microplankton and nanoplankton fraction from October 2011 to September 2012, in Almirante Storni Port (Nuevo Gulf).
Supplementary figure S2. Temporal variation in phytoplankton abundance (a) and Chl a (b) in Nuevo Gulf observed during different time periods (indicated in the legend) by diverse research references. Data expressed as mean and standard deviation (bars). Santinelli (Citation2008) and D’Agostino et al. (Citation2018) data is presented as the seasonal mean abundance and Chl a.
