Environmental Engineering Reference
In-Depth Information
development was very late in the early 1970s, early in the late 1950s, and
very early in the 1990s (Mackas et al. 1998). These changes in timing were
strongly correlated with large-scale year-to-year and decade-to-decade
ocean climate fl uctuations, as refl ected by spring season temperature
anomalies in the surface mixed layer in which juvenile copepodites feed and
grow (Mackas et al. 1998). The change in developmental timing is probably
a consequence of both increased survival of early cohorts in warm years
and physiological acceleration (Mackas et al. 1998).
Using long-term data (1958-2002), Edwards and Richardson (2004)
detected signifi cant phenological changes in zooplankton community
in the central North Sea. The timing of temporary members of the
zooplankton (
meroplankton
, organisms that are planktonic for only a part
of their life cycle), might be affected more by warming sea temperatures
than permanent members (
holoplankton
) (Edwards and Richardson 2004).
During summer, meroplankton as a whole (larvae of cirripeds, cyphonautes,
decapods, echinoderms, fi sh larvae, and lamellibranchs) has anticipated
their appearance in the plankton by 27-days over the 45-years study
period (Edwards and Richardson 2004). In the case of copepods and non-
copepod holoplankton, they have both moved forward only by 10-days.
Organisms that are dependent upon temperature to stimulate physiological
developments and larval release have signifi cantly moved forward in their
seasonal cycle in response to temperature (Edwards and Richardson 2004).
The level of response differed throughout the community and the seasonal
cycle, leading to a mismatch between trophic levels and functional groups
(Edwards and Richardson 2004). The different extent to which functional
groups are moving forward in time in response to warming has led to a
mismatch between successive trophic levels and a change in the synchrony
of timing between primary, secondary and tertiary production (Edwards
and Richardson 2004).
Marine zooplankton and ocean acidifi cation
Acidifi cation of the ocean is another effect of global change linked to CO
2
emissions. Almost 50% of anthropogenic CO
2
emitted in to the atmosphere
diffuses passively into the ocean, and when CO
2
dissolves in the seawater,
it causes alterations in fundamental chemical balances that together are
commonly referred to as
ocean acidifi cation
(Fig. 1) (e.g.
,
Caldeira and Wickett
2003, Sabine et al. 2004, Doney et al. 2009, Feely et al. 2010). Such changes
comprise increase in the concentration of carbonic acid (H
2
CO
3
), bicarbonate
ion (HCO
3
-
) and hydrogen ion (H
+
), and decreases in the concentration of
carbonate (CO
3
2-
) in surface waters, where the bulk of oceanic production
occurs. Thus, production of H
+
lowers the pH and causes the phenomenon
called ocean acidifi cation. Carbonate ions can react with the excess H
+
to
