Environmental Engineering Reference
In-Depth Information
systems, phenology has been associated to both climate and anthrophogenic
disturbances on the marine biota (Yang and Rudolf 2010), and in many
species phenology is biased in the directions predicted from global
warming in the last few decades (Parmesan 2006). The synchronization of
the phenological cycles of phyto- and zooplankton is crucial for the matter
and energy transfer through the food web (Beaugrand et al. 2003, Edwards
and Richardson 2004, Chassot et al. 2010). In fact, a mismatch scenario
between food availability and heterotrophic demand might profoundly
affect population of superior predators (Durant et al. 2007, Yang and Rudolf
2010).
Spring phytoplankton blooms are ubiquitous in temperate systems,
but growing evidence showed changes in phenology, magnitude and
composition both in the fi eld (Cloern et al. 2007, Wiltshire et al. 2008,
Guinder et al. 2010) and in mesocosms experiments (Sommer and
Lengfellner 2008, Lewandowska and Sommer 2010). Increasing temperature
advances the spring phytoplankton bloom, and the degree of advance
depends on resource dynamics, predator-prey interactions and taxonomic
phytoplankton groups according to their physiological characteristics. In
deep systems with thermal stratification, spring blooms are triggered by
correlated increases in temperature and seasonal light availability (Edwards
and Richardson 2004). Conversely, in shallow, well-mixed systems,
phytoplankton blooms can occur coupled to external light regime and
independently of temperature change (Sommer and Lengfellner 2008). For
instance, in shallow estuaries, changes in turbidity, i.e., light attenuation,
salinity and nutrient supply along the land-sea transition can signifi cantly
affect the magnitude of the phytoplankton bloom and the community
structure (e.g., Struyf et al. 2004). Similarly, changes in phytoplankton
phenology and species composition of the winter-early spring bloom
have been observed in the Bahía Blanca Estuary (Argentina) in relation to
long-term decreasing trends in local precipitations and warmer conditions
over the last decades (Guinder et al. 2010). In the eutrophic Neuse River
Estuary (USA), phytoplankton production has been signifi cantly reduced
in response to droughts events (Wetz et al. 2011). In the Narragansett Bay
(USA), changes in the phytoplankton annual pattern over the last 50 years
(i.e., decrease in the winter-spring bloom and occurrence of relatively
short diatom blooms in spring, summer and fall) have been related to
warming water especially in winter, cloudiness and a signifi cant decline in
the wind speed (Nixon et al. 2009), together with a shift from eutrophic to
oligotrophic conditions due to wastewater treatments. A further example
is given by the increase in phytoplankton summer blooms in the Bahía
Blanca Estuary in recent years. The combination of dredging operations
together with changes in the wind pattern have induced the resuspension
of nutrients and resting stages of diatoms (Guinder et al. 2012), that have
