Environmental Engineering Reference
In-Depth Information
al. 2006), stream fi sh communities (Genner et al. 2010) and suggested in
pelagic marine copepods (Beaugrand et al. 2003). Further fi eld studies
(Gómez and Souissi 2007, Winder et al. 2008, Guinder et al. 2010, 2013), and
empirical investigations (Sommer and Lengfellner 2008, Lewandowska and
Sommer 2010) reported a restructuring of the phytoplankton community
composition toward a dominance of small species along with increasing
water temperature. The reduction in cell/body size of planktonic organisms
and displacements of species ranging to higher latitudes have been mainly
ascribed to global warming (Morán et al. 2009, Daufresne et al. 2009,
Beaugrand et al. 2010), which might affect food web networks, with potential
negative effects on the biological carbon pump.
Phytoplankton cell size follows biophysical rules (e.g., nutrient uptake,
motion, sinking rates, kinetics of metabolism) that affect growth rates,
the biogeochemical cycling and trophodynamics (Finkel et al. 2010). The
replacement of large cells by smaller ones under warming conditions is
likely related to shifts of the species' environmental optimum growth
and the higher competitive skills of small cells (Winder et al. 2008). A
non-exclusive hypothesis suggests changes in grazing rate or selectivity
of zooplankton (Sommer and Lengfellner 2008, Klauschies et al. 2012).
The climate-change scenario of warming and nutrient depletion in the
euphotic zone favor the dominance of small-sized phytoplankton species
(e.g., Rodriguez et al. 2001), as they present higher surface to volume ratios
and thus lower sinking velocities (Huisman and Sommeijer 2002) and small
diffusion boundary layers, i.e., more effi cient nutrient uptake and superior
ability to harvest light (Litchman et al. 2007). In agreement to this, the
appearance of small phytoplankton species followed by the persistence,
perennial predominance or even establishment as dominant species has
been increasingly documented worldwide (Hays et al. 2005, Beaugrand
et al. 2010). For instance, the abundance of
Cyclotella
taxa has increased in
lakes since the nineteenth century (Rühland et al. 2008, Winder et al. 2008)
linked to enhanced thermal stratifi cation. Similarly, the phytoplankton size-
structure in some estuaries has shifted towards the dominance of smaller
diatoms, e.g.,
Cyclotella
sp. and
Thalassiosira minima
(Guinder et al. 2010)
in relation to complex interactive effects of increase in water temperature
and salinity, as well as changes in precipitation regime and modifi cations
in trophic interactions (Guinder et al. 2013).
Bloom phenology and magnitude
:
Rising temperatures in both marine and
freshwater systems are related to the advancement of seasonal ecological
events in phyto- and zooplankton (Parmesan and Yohe 2003, Edwards and
Richardson 2004, Winder and Schindler 2004). The phenology is the study
of the seasonal cycles, i.e., phytoplankton blooming events, zooplankton
hatching eggs, and their link with environmental variations. In coastal
