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

Figure IV.C.13. Long-term monthly changes (1958-1999) in the plankton index. A
negative anomaly in the index indicates a low value for Calanus finmarchicus, euphausiids,
mean size of calanoid copepods with the exception of C. helgolandicus (opposite pattern) and
Pseudo-calanus spp. (no relationship). A positive anomaly indicates a high abundance of
preys (and preys of suitable size). Cod recruitment (in decimal logarithm) in the North Sea
(curve in white) is superimposed. The period of the Gadoid Outburst (Cushing 1984) is also
indicated. Modified from Beaugrand et al. (2003).
Temperature increases metabolic rate and therefore increases the energy demand.
Temperature rises decreases the quality and the quantity of prey available for larvae
(so the energetic supply). Temperature rise may have therefore augmented the
energetic unbalance of larval cod that may have resulted in increasing larval mortality
(the hypotheses of size specific survival or growth dependent mortality). These
results provide evidence that changes in the plankton ecosystem are the probable
cause of the increased recruitment during the period 1963-1983, which was called
the “Gadoid Outburst”.
IV.C.8. Habitats
The coastal marine system is organized as a succession of spatial units, each of them
having its own characteristics and where the organisms are adapted to a specific range
of environmental conditions. Estuaries, salt-marshes, lagoons, rocky shores, seagrass
meadows, sandy beaches, all these units or habitats are often very productive, and in
the same time, very vulnerable to changes in the external forcing which are issued from
land, atmosphere and ocean and interact in the coastal zone at overlapping scales.
Coastal lagoons around Europe are already experiencing drastic and irreversible
changes (see part B and part E of the Report) in their ecosystems reacting to both
climatic trends and increasing human pressure. Seagrass beds are another example of
marine habitats under climate change threats, particularly vulnerable to increase in
storminess.
Seagrass meadows
Seagrasses are vascular plants, typically configured like their terrestrial counterparts with
a system of leaves, flowers and roots. Originally deriving from land and/or freshwater
102