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H. Dutta
Physiological and physical factors enable cyanobacteria to dominate phytoplankton assemblages under higher temperatures (O’Neil et al. 2012). In fact, physiological
traits specific to cyanobacteria provide them much advantage compared with other
taxa under such conditions. Hence, the effects of climate change have been predicted
to exert substantial effects on phytoplankton species composition and biomass in
freshwaters and potentially favour cyanobacteria over other phytoplanktons. As a
whole, cyanobacteria as a group are likely to increase in most regions in the future
(Carey et al. 2012). In this context, Kosten et al. (2012) state that warmer climates
do not increase the overall phytoplankton biomass but the percentage of the total
phytoplankton biovolume attributable to cyanobacteria increases steeply with temperature. Their results indicated a synergy between nutrients and climate. The genus
Microcystis is an important example in this context. Experimental results indicate
that higher temperature and phosphorous levels would yield higher growth rates in
the toxic strain of this cyanobacteria, compared with its non-toxic strain. So, future
eutrophication and climatic warming are predicted to promote the growth of toxic,
rather than non-toxic populations of Microcystis (Davis et al. 2009).
Greater input of nutrients and rising temperatures synergistically intensify the
symptoms of eutrophication (Moss et al. 2011). Climate change leads to intense
storms that increase soil erosion and thus nutrient delivery is increased. At times, it
decreases rainfall in summers or gives rise to dry seasons and consequently, the water
levels diminish in lakes. As a result, nutrients that are already present become concentrated and the marginal sediment is exposed to mineralization and nutrient release.
Residence times are also increased. This favours the propagation of persistent phytoplankters such as cyanobacteria (Moss et al. 2011). Apart from these, warming
soils, and melting glaciers (Jeppesen et al. 2011) and higher rates of mineralization
in catchment soils (Rustad et al. 2001; Brookshire et al. 2011) due to climate change
also contribute to nutrient loading. Moreover, warming causes greater deoxygenation at the surfaces of lake sediments and so more nutrients are released in summer
(Jensen and Andersen 1995). Nutrients are also likely to increase in the marine environment. This is understood from the fact that climate change is likely to trigger
temperature fluctuations that could affect the oceanographic features in the Mediterranean. Consequently, nutrient enrichment and plankton blooms are expected to occur
(CIESM 2008).
3.4 Assessment of Synergistic Effect of Climate Change
on Eutrophication and Species Invasion
3.4.1 Criteria for Assessment
Assessment has been done based on the following six phenomena (A-F). These specific phenomena have been identified as the criteria for assessment because they
H. Dutta
Physiological and physical factors enable cyanobacteria to dominate phytoplankton assemblages under higher temperatures (O’Neil et al. 2012). In fact, physiological
traits specific to cyanobacteria provide them much advantage compared with other
taxa under such conditions. Hence, the effects of climate change have been predicted
to exert substantial effects on phytoplankton species composition and biomass in
freshwaters and potentially favour cyanobacteria over other phytoplanktons. As a
whole, cyanobacteria as a group are likely to increase in most regions in the future
(Carey et al. 2012). In this context, Kosten et al. (2012) state that warmer climates
do not increase the overall phytoplankton biomass but the percentage of the total
phytoplankton biovolume attributable to cyanobacteria increases steeply with temperature. Their results indicated a synergy between nutrients and climate. The genus
Microcystis is an important example in this context. Experimental results indicate
that higher temperature and phosphorous levels would yield higher growth rates in
the toxic strain of this cyanobacteria, compared with its non-toxic strain. So, future
eutrophication and climatic warming are predicted to promote the growth of toxic,
rather than non-toxic populations of Microcystis (Davis et al. 2009).
Greater input of nutrients and rising temperatures synergistically intensify the
symptoms of eutrophication (Moss et al. 2011). Climate change leads to intense
storms that increase soil erosion and thus nutrient delivery is increased. At times, it
decreases rainfall in summers or gives rise to dry seasons and consequently, the water
levels diminish in lakes. As a result, nutrients that are already present become concentrated and the marginal sediment is exposed to mineralization and nutrient release.
Residence times are also increased. This favours the propagation of persistent phytoplankters such as cyanobacteria (Moss et al. 2011). Apart from these, warming
soils, and melting glaciers (Jeppesen et al. 2011) and higher rates of mineralization
in catchment soils (Rustad et al. 2001; Brookshire et al. 2011) due to climate change
also contribute to nutrient loading. Moreover, warming causes greater deoxygenation at the surfaces of lake sediments and so more nutrients are released in summer
(Jensen and Andersen 1995). Nutrients are also likely to increase in the marine environment. This is understood from the fact that climate change is likely to trigger
temperature fluctuations that could affect the oceanographic features in the Mediterranean. Consequently, nutrient enrichment and plankton blooms are expected to occur
(CIESM 2008).
3.4 Assessment of Synergistic Effect of Climate Change
on Eutrophication and Species Invasion
3.4.1 Criteria for Assessment
Assessment has been done based on the following six phenomena (A-F). These specific phenomena have been identified as the criteria for assessment because they