Environmental Engineering Reference
In-Depth Information
Fig. 4.
Marine phytoplankton is affected by climate-driven hydrological modifi cations at every
level of ecological organization (from organisms to ecosystem). The direct effects of increasing
CO
2
and temperature on phytoplankton are related with cell physiology (e.g., photosynthesis,
growth rates and range shifts). The indirect effects are related with modifi cations of the
pelagic environmental conditions (e.g., pH, light, nutrients and grazing activity), affecting
phytoplankton size-structure, stoichiometry, sedimentation rates, species interactions and
bloom phenology. In turn, these changes result in substantial alterations of the structure of
pelagic food webs and ecosystem functioning.
availability -light and nutrients- and zooplankton grazing pressure and
selectivity. At the individual level phytoplankton is affected via changes
in physiology, morphology and behavior, whereas the population level by
shifting tolerance ranges and thus amplitude of ecological niches, which in
turn infl uence the dispersion and recruitment of the species. The community
level is affected by changes in structure (size, composition, diversity),
phenology and the biogeographical distribution of species that derive
in new inter-specifi c interactions and trophodynamics. Among the most
common direct and indirect universal responses of phytoplankton to climate
change we can summarize: 1) alterations in growth and photosynthesis rates
and in calcifi cation processes related to CO
2
rise and ocean acidifi cation,
2) dominance of smaller species under warmer conditions (related to both
water stability and/or grazing pressure), 3) changes in the phenology,
magnitude and species composition of phytoplankton spring bloom due to
earlier thermal stratifi cation, overwintering and/or enhanced zooplankton
activity, 4) occurrence of biomass peaks or
miniblooms
in other seasons
(e.g., summer, autumn) and HABs in coastal systems related to warmer
conditions, eutrophication and/or changes in wind patterns, and 5) changes
