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Effects of CO2, nutrients and light on coastal plankton: II. Metabolic rates. Aquatic Biology

TitleEffects of CO2, nutrients and light on coastal plankton: II. Metabolic rates. Aquatic Biology
Publication TypeJournal Article
Year of Publication2014
AuthorsMercado, JM, Sobrino, C, Neale, PJ, Segovia, M, Reul, A, Amorim, AL, Carrillo, P, Claquin, P, Cabrerizo, MJ, León, P, Lorenzo, MR, Medina, JM, Montecino, V, Napoléon, C, Prasil, 0., Putzeys, S, Salles, S, Yebra, L
JournalAquatic Biology
Volume22
Pagination43-57
Date Published11/20/14
Abstract

We conducted a microcosm experiment aimed at studying the interactive effects
of high CO2, nutrient loading and irradiance on the metabolism of a planktonic community
sampled in the Western Mediterranean near the coast of Málaga. Changes in the metabolism
of phytoplankton and bacterioplankton were observed for 7 d under 8 treatment conditions,
representing the full factorial combinations of 2 levels each of CO2, nutrient concentration
and solar radiation exposure. The initial plankton sample was collected at the surface from
a stratified water column, indicating that phytoplankton were naturally acclimated to high
irradiance and low nutrient concentrations. Nutrient addition combined with high irradiance
resulted in a significant increase in primary production. Nitrate uptake by phytoplankton was
also stimulated under high nutrient conditions. High nutrients, high irradiance and the combination
of low CO2 and high irradiance positively affected bacterial production. Light was the
main factor affecting the respiration rates of the community, which were higher at the high
light level. After 7 d of incubation, nutrient loading was the only factor that significantly
affected the amount of particulate organic carbon (POC) accumulated in the microcosms.
Therefore, the changes in metabolic rates produced at high CO2 had no effect on net production
of particulate organic matter. If these results are extrapolated to the natural environment,
it could be hypothesized that high levels of CO2 will have a limited impact on biological
pump activity in the northern Alboran Sea since it is assumed that POC export towards deeper
layers determines the potential for carbon sequestration.