64
extensive changes in the net atmosphere-ocean balance of
carbon dioxide (Gruber et al. 2009). The authors also noted
the possibly important role of other oceanic regions that
could be large contributors to feedbacks in the climate
system.
Primary production in the ocean has declined in the last
decades and corresponds with increasing sea surface temperature and decreasing iron input. Since especially in high
latitudes the ocean acts as important carbon sink, a climate
change related further decline in primary production suggests major implications for the carbon cycle (Gregg et al.
2003). The same trend was predicted for many regions using
a global model due to increasing stratification and nutrient
limiting conditions in the ocean, with exception of the poles
(Henson et al. 2018). Reduced sea ice and longer bloom periods in the Arctic have already lead to an increase in net primary production (Arrigo and van Dijken 2015). In contrast,
net primary production decreases were also predicted with
simulations from nine Earth system models within the framework of the fifth phase of the Coupled Model Intercomparison
Project (CMIP5) (Fu et al. 2016).
Useful tools are one-dimensional biogeochemical models
such as MEDUSA (Model of Ecosystem Dynamics, nutrient
Utilisation, Sequestration and Acidification) that can globally simulate multi-decadal plankton ecosystem scenarios
(Yool et al. 2011). In a global approach, the model was used
to investigate spring bloom timing related to climate change
in a high resolution. The change in bloom initiation timing
was substantial, which could lead to food shortages for predators. Additionally, increasing ocean stratification and nutrient limiting conditions will likely result in less total primary
production (Henson et al. 2018). Detailed future predictions
using this one-dimensional biogeochemical model exist for
the Ross Sea in the Antarctic. Primary production for the
twenty-first century was estimated and presumably increases
5% in the early and 14% in the late twenty-first century.
Melting ice, increased radiance, and decreasing mixed layer
depths influence primary production during the first half,
diatom mass likely stays constant while Phaeocystis antarctica multiplies, which then switches for the second half.
Shallower mixed layer depths will change phytoplankton
composition and carbon export (Kaufman et al. 2017).
On the Patagonian coast, average primary production will
likely increase and phytoplankton communities sequester
significant carbon amounts important for secondary production. However, these predictions cannot be made for open
ocean areas without restrictions (Villafañe et al. 2015).
Furthermore, changes will vastly differ regionally, showing
increasing primary production in some areas and decreasing
primary production in others. Another critical value influencing phytoplankton variability and competition is the increase
of stratified conditions within the water column (Yoshiyama
et al. 2009).
Many studies have been conducted to gather more information about phytoplankton community changes and their
effects on the food web (e.g., Edwards and Richardson 2004;
Schlüter et al. 2012; Harding Jr. et al. 2015). Fu et al. (2016)
used a model to simulate climate change impacts on net primary production and export production. Using an intense
warming scenario, the net primary production was critically
dependent on the phytoplankton community structure. This
model gives a good insight in the importance of communitybased studies in order to monitor changes in this sensitive
system. Changes in phytoplankton communities have, for
example, already been observed under changing environmental conditions in the Arctic regions. Shifts in certain protist abundances indicate an enhanced presence of potentially
toxic Alexandrium dinoflagellate species (Elferink et al.
2017).
Changes in the phytoplankton composition also cause the
whole food web to change since predators might have to
adapt to new food sources. Alternating environmental factors
can facilitate the invasion of new species, which can migrate
naturally inside the water masses or might be introduced via
ballast water. These atypical range expansions cause structural changes in the food web, especially if the invasive species can adapt well or even better than indigenous species
and may even become dominating (Walther et al. 2002;
Olenina et al. 2010).
Other effects include the shifts of bloom events, mainly
due to temporal and long-term climatic changes, or the timing of phyto- and zooplankton growth. These changes in timing could result in drastic consequences of ecosystem
functionality. Existing studies on trophic mismatching in the
plankton community are mostly focused on interactions
between spring blooms (e.g., Edwards and Richardson 2004;
Wiltshire et al. 2008). Therefore, not much is known about
the ecological impacts and the functioning of the marine ecosystem (Thackeray 2012).
The floral composition of Chesapeake Bay at the US coast
of the Atlantic Ocean revealed a shift in phytoplankton community. With nitrogen being the limiting nutrient but diatoms
requiring relatively large amounts, the local community will
likely shift to a smaller diatom proportion. Anthropogenic
nutrient input might trigger changes as well as climaterelated shifts in phytoplankton composition (Harding Jr.
et al. 2015). Seasonal variability studies can provide useful
insights into future climate changes, as they can give an
impression about the mechanisms leading to changes.
Studies at the coast of Patagonia in Argentina exposed seasonally different phytoplankton communities to possible
future conditions, like enhanced temperatures and solar radiance, nutrient enrichment, and ocean acidification. Increasing
ocean temperature has little effect on pre-bloom communities.
However, ultraviolet radiance during blooms leads to photochemical inhibition of phytoplankton. Increasing temperaL. Käse and J. K. Geuer
extensive changes in the net atmosphere-ocean balance of
carbon dioxide (Gruber et al. 2009). The authors also noted
the possibly important role of other oceanic regions that
could be large contributors to feedbacks in the climate
system.
Primary production in the ocean has declined in the last
decades and corresponds with increasing sea surface temperature and decreasing iron input. Since especially in high
latitudes the ocean acts as important carbon sink, a climate
change related further decline in primary production suggests major implications for the carbon cycle (Gregg et al.
2003). The same trend was predicted for many regions using
a global model due to increasing stratification and nutrient
limiting conditions in the ocean, with exception of the poles
(Henson et al. 2018). Reduced sea ice and longer bloom periods in the Arctic have already lead to an increase in net primary production (Arrigo and van Dijken 2015). In contrast,
net primary production decreases were also predicted with
simulations from nine Earth system models within the framework of the fifth phase of the Coupled Model Intercomparison
Project (CMIP5) (Fu et al. 2016).
Useful tools are one-dimensional biogeochemical models
such as MEDUSA (Model of Ecosystem Dynamics, nutrient
Utilisation, Sequestration and Acidification) that can globally simulate multi-decadal plankton ecosystem scenarios
(Yool et al. 2011). In a global approach, the model was used
to investigate spring bloom timing related to climate change
in a high resolution. The change in bloom initiation timing
was substantial, which could lead to food shortages for predators. Additionally, increasing ocean stratification and nutrient limiting conditions will likely result in less total primary
production (Henson et al. 2018). Detailed future predictions
using this one-dimensional biogeochemical model exist for
the Ross Sea in the Antarctic. Primary production for the
twenty-first century was estimated and presumably increases
5% in the early and 14% in the late twenty-first century.
Melting ice, increased radiance, and decreasing mixed layer
depths influence primary production during the first half,
diatom mass likely stays constant while Phaeocystis antarctica multiplies, which then switches for the second half.
Shallower mixed layer depths will change phytoplankton
composition and carbon export (Kaufman et al. 2017).
On the Patagonian coast, average primary production will
likely increase and phytoplankton communities sequester
significant carbon amounts important for secondary production. However, these predictions cannot be made for open
ocean areas without restrictions (Villafañe et al. 2015).
Furthermore, changes will vastly differ regionally, showing
increasing primary production in some areas and decreasing
primary production in others. Another critical value influencing phytoplankton variability and competition is the increase
of stratified conditions within the water column (Yoshiyama
et al. 2009).
Many studies have been conducted to gather more information about phytoplankton community changes and their
effects on the food web (e.g., Edwards and Richardson 2004;
Schlüter et al. 2012; Harding Jr. et al. 2015). Fu et al. (2016)
used a model to simulate climate change impacts on net primary production and export production. Using an intense
warming scenario, the net primary production was critically
dependent on the phytoplankton community structure. This
model gives a good insight in the importance of communitybased studies in order to monitor changes in this sensitive
system. Changes in phytoplankton communities have, for
example, already been observed under changing environmental conditions in the Arctic regions. Shifts in certain protist abundances indicate an enhanced presence of potentially
toxic Alexandrium dinoflagellate species (Elferink et al.
2017).
Changes in the phytoplankton composition also cause the
whole food web to change since predators might have to
adapt to new food sources. Alternating environmental factors
can facilitate the invasion of new species, which can migrate
naturally inside the water masses or might be introduced via
ballast water. These atypical range expansions cause structural changes in the food web, especially if the invasive species can adapt well or even better than indigenous species
and may even become dominating (Walther et al. 2002;
Olenina et al. 2010).
Other effects include the shifts of bloom events, mainly
due to temporal and long-term climatic changes, or the timing of phyto- and zooplankton growth. These changes in timing could result in drastic consequences of ecosystem
functionality. Existing studies on trophic mismatching in the
plankton community are mostly focused on interactions
between spring blooms (e.g., Edwards and Richardson 2004;
Wiltshire et al. 2008). Therefore, not much is known about
the ecological impacts and the functioning of the marine ecosystem (Thackeray 2012).
The floral composition of Chesapeake Bay at the US coast
of the Atlantic Ocean revealed a shift in phytoplankton community. With nitrogen being the limiting nutrient but diatoms
requiring relatively large amounts, the local community will
likely shift to a smaller diatom proportion. Anthropogenic
nutrient input might trigger changes as well as climaterelated shifts in phytoplankton composition (Harding Jr.
et al. 2015). Seasonal variability studies can provide useful
insights into future climate changes, as they can give an
impression about the mechanisms leading to changes.
Studies at the coast of Patagonia in Argentina exposed seasonally different phytoplankton communities to possible
future conditions, like enhanced temperatures and solar radiance, nutrient enrichment, and ocean acidification. Increasing
ocean temperature has little effect on pre-bloom communities.
However, ultraviolet radiance during blooms leads to photochemical inhibition of phytoplankton. Increasing temperaL. Käse and J. K. Geuer