Environmental Engineering Reference
In-Depth Information
Ongoing warming together with rising CO
2
will see an expansion of low
oxygen zones, perhaps by more than 50% of their present volume by the
end of the century (Oschlies et al. 2008). These expansions will affect some
of the world's most productive regions in terms of fi sheries, so there could
be economic as well as ecological consequences. Furthermore, coastal
eutrophication resulting from increased riverine run-off of fertilizers and
increases in sea level will bring further accumulations of particulate organic
matter and increased microbial activity that consumes dissolved oxygen
(Díaz and Rosenberg 2008). Mobile organisms are able to avoid low oxygen
concentrations, but sedentary ones have little choice but to tolerate low
oxygen concentrations or die. Those which are able to tolerate hypoxic
conditions might, paradoxically, benefi t from reduced predation if predators
are themselves excluded (Altieri 2008).
Bakun (2010) has reported that the available data series are short
compared to the relevant time scales of variation. So, how can the multiple
realizations of the controlling processes be assessed in order to confi dently
identify the basic dynamics? Moreover, if one surrenders the assumption
of system stationarity, how can one hope to parameterize any sort of
predictive model? The same author states, “if one is confronted with a
complex adaptive system, wishing (or pretending) it were otherwise may
yield answers”. But these probably will not be the correct, comprehensive
or useful answers that are needed.
Main Manifestations of Climate Change Effects on the Marine
Environment
Ocean climate is variable and there have been warm periods previously,
notably from the mid-1920s to the 1960s in the North Atlantic (Jensen 1939).
The changes in species and ecosystems which took place then were very
similar to those occurring now and we can use these past warm periods
as analogues. However, these warm periods during the 20th century are
examples of natural climate variability, whereas present climatic trends
are expected to continue and conditions are moving outside the bounds of
previous experience due to climate change. The trend will not be smooth
and will continue to have large interannual and decadal variability
superimposed on it (Sutton and Hodson 2005, Smith et al. 2007). Decadal
variability in ocean climate is one of the major causes of regime shifts, when
the biology of large areas such as the North Sea changes quite rapidly to
a different state (altered species dominance, production and seasonality)
(Beaugrand 2004). Understanding the way in which climate change may
affect decadal and shorter time scale variability, is therefore essential in
predicting future climate impacts on marine ecosystems and fi sheries.
