Climate Change and the European Water Dimension - Agri ...

study has been maded to explore potential effects of UVBR increase in shallow
lagoons. In marine algae, phanerogams and phytoplankton, photosyntehsis can be
inhibited by UVBR (Smith et al., 1992). Furthermore, UVBR enhances phytoplankton
and bacterial mortality particularly in the top 5 m of the water column, where there is
little attenuation (Boelen et al., 2002).
It has been also demonstrated that enhanced UVBR can change the structure and
dynamics of the pelagic food web (Mostjir et al., 1999). As a consequence, the
ecosystem develops toward a microbial food web (smaller organisms, less
productive) in preference to an herbivorous food web (larger organisms, much more
productive). This food web change can have broad implications for aquaculture in
lagoons.
IV.D.4. Expected long-term effects related to climate changes that are superimposed
on direct human alterations
Human activities within watersheds and in coastal lagoon systems have direct impact
on the quantity and quality of the waters delivered to adjacent seas or ocean. An
increased variety of land uses has contributed to increased changes in watershed
structure and hydrographic networks. Overall, these alterations influence coastal
lagoons and nearshore coastal waters through spatial dependent and time-lagged
processes that control the delivery of nutrients and pollutants (Borum, 1996, Turner
et al., 1997, Valiela et al., 1997, Vitousek et al., 1997, Carpenter, et al, 1998, Holland
et al., 2004).
Losses of goods and services.
Seagrass communities, and to a lesser extent microphytobenthic systems, support
high secondary production that is not only of commercial interest. Biotic equilibria,
especially those depending upon seagrass processes, are responsible for invaluable
ecosystem functions and services such as carbon dioxide and nutrient sinks,
sediment oxygenation and stability, recovery of redox buffers, etc. Climate change
may indirectly add further stress, degrading and threatening their ecological
sustainability. In the long term, losses of non-commercial goods and services can
determine also economic losses, e.g. fishery decline, touristic attractiveness, etc.
Impact of aquaculture:
Aquaculture development affects local ecosystems, where wastewater from fish or
mollusc farming can pollute the aquatic environment. The exploitation of benthic
organisms (e.g., clams) can also cause sediment reworking and alteration. In warm
water, not only the development risk of human pathogens increases, but also water
quality undergoes deterioration. Accelerated microbial decomposition of aquaculture
wastes can cause lowering of oxygen concentrations and perhaps induce stress to
cultivated organisms as well as natural species. Higher temperatures may allow
higher incidences of disease, especially if the organisms in the region are under
stress.
Increasing eutrophication.
The interaction between eutrophication and climate change can potentially determine
shifts in community structure and enhance the risk of harmful algal blooms, the risk of
increase in the frequency and severity of anoxic crises with subsequent mortality of
commercial species.
Increasing unpredictability.
Coastal lagoons are recognised as highly unpredictable environments. There is
evidence that within certain thresholds, marine communities and ecosystems are
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