Future climate scenarios for a coastal productive planktonic food web resulting in microplankton phenology changes and decreased trophic transfer efficiency.
We studied the effects of future climate change scenarios on plankton communities of a Norwegian fjord using a mesocosm approach. After the spring bloom, natural plankton were enclosed and treated in duplicates with inorganic nutrients elevated to pre-bloom conditions (N, P, Si; eutrophication), lowering of 0.4 pH units (acidification), and rising 3°C temperature (warming). All nutrient-amended treatments resulted in phytoplankton blooms dominated by chain-forming diatoms, and reached 13-16 μg chlorophyll (chl) a l-1. In the control mesocosms, chl a remained below 1 μg l-1. Acidification and warming had contrasting effects on the phenology and bloom-dynamics of autotrophic and heterotrophic microplankton. Bacillariophyceae, prymnesiophyceae, cryptophyta, and Protoperidinium spp. peaked earlier at higher temperature and lower pH. Chlorophyta showed lower peak abundances with acidification, but higher peak abundances with increased temperature. The peak magnitude of autotrophic dinophyceae and ciliates was, on the other hand, lowered with combined warming and acidification. Over time, the plankton communities shifted from autotrophic phytoplankton blooms to a more heterotrophic system in all mesocosms, especially in the control unaltered mesocosms. The development of mass balance and proportion of heterotrophic/autotrophic biomass predict a shift towards a more autotrophic community and less-efficient food web transfer when temperature, nutrients and acidification are combined in a future climate-change scenario. We suggest that this result may be related to a lower food quality for microzooplankton under acidification and warming scenarios and to an increase of catabolic processes compared to anabolic ones at higher temperatures.
Institut de Ciències del Mar - CSIC, Barcelona, Spain.
Albert
A
Calbet
P. P. Shirshov Institute of Oceanology RAS, Moscow, Russia.
Andrey F
AF
Sazhin
Skidaway Institute of Oceanography, University of Georgia, Savannah, Georgia, United States of America.
Jens C
JC
Nejstgaard
Skidaway Institute of Oceanography, University of Georgia, Savannah, Georgia, United States of America; Department of Biology, University of Bergen, Bergen, Norway.
Stella A
SA
Berger
Skidaway Institute of Oceanography, University of Georgia, Savannah, Georgia, United States of America.
Zachary S
ZS
Tait
Institut de Ciències del Mar - CSIC, Barcelona, Spain; Instituto de Investigaciones Marinas - CSIC, Vigo, Spain.
Lorena
L
Olmos
Department of Biology, University of Crete, Heraklion, Crete, Greece.
Despoina
D
Sousoni
Institut de Ciències del Mar - CSIC, Barcelona, Spain; Institute of Oceanography, Hellenic Centre for Marine Research, Athens, Greece.
Stamatina
S
Isari
Institut de Ciències del Mar - CSIC, Barcelona, Spain.
Rodrigo A
RA
Martínez
Department of Biology, University of Bergen, Bergen, Norway; Sars International Centre, Uni Research, University of Bergen, Bergen, Norway.
Jean-Marie
JM
Bouquet
Department of Biology, University of Bergen, Bergen, Norway; Sars International Centre, Uni Research, University of Bergen, Bergen, Norway.
Eric M
EM
Thompson
Department of Ecology and Environmental Sciences, Umeå University, Umeå, Sweden.
Ulf
U
Båmstedt
Department of Bioscience, Aarhus University, Roskilde, Denmark.
Hans H
HH
Jakobsen
D018533:Biomass; D002734:Chlorophyll / Q000096:biosynthesis; D000077194:Chlorophyll A; D016798:Ciliophora / Q000502:physiology*; D002980:Climate; D057231:Climate Change; D017377:Diatoms / Q000502:physiology*; D004141:Dinoflagellida / Q000502:physiology*; D005068:Eutrophication; D020387:Food Chain; D005544:Forecasting; D052836:Heterotrophic Processes; D006863:Hydrogen-Ion Concentration; D015233:Models, Statistical; D009664:Norway; D010839:Phytoplankton / Q000502:physiology*; D013696:Temperature
D002734:Chlorophyll; D000077194:Chlorophyll A