Page 34 - climate-change2013

2. Changes

in reproduction

and breeding dates

of key species

Increasing seawater temperature affects physiological
processes in marine organisms and consequently influ-
ences processes such as foraging, growth, behaviour
and reproduction. Physiological performance is the
principal determinant of a species’ tolerance to envi-
ronmental variability and change. As climate or other
conditions shift, organisms initially respond on the basis Loggerhead turtle (Caretta caretta) in the southwest of Sardinia coast, Italy.
of physiological and behavioural adaptations that have Photo: J. Cuetos, OCEANA
been moulded through their evolutionary history. In this
way, they may be able to adapt or acclimatize to the
new conditions. If conditions are intolerable, however,
migration to other areas, life cycle adjustments or local
extinction may occur.

There is now good evidence that over the last decade
the timing of seasonal events such as breeding and
reproduction of many species around the globe has
shifted due to climate change. Higher seawater tem-
peratures and acidification are affecting physiological
processes in marine organisms and will continue to do
so, with eventual impacts on the geographical distribu-
tion of species (Lejeusne et al., 2010; Ross et al., 2011).
Moreover, as temperature affects reproductive devel-
opment in many species, seawater warming could re-
sult in spawning periods occurring earlier than normal.

INDICATOR

Changes in reproduction and breeding
dates of selected species

Nesting season and hatching success

In sea turtles, sex determination is dependent on
incubation temperature. Lower temperatures result
in male hatchlings and higher temperatures produce
females. This means that eggs laid early in the season
could be more likely to produce male hatchlings
than eggs laid later on. For the breeding sea turtle
species Caretta caretta and Chelonia mydas, monk
seals Monachus monachus and coastal seabirds, by
recording the dates of arrival and of the start of the
breeding (nesting) season, as well as hatching and
nestling success, it is possible to analyse trends in the
timing of these events and their potential effects.
Evolution of annual flowering prevalence (bars, FP:
PROPOSED MONITORING PROCEDURE flowering records per total records) since 1973 un-
Nesting beaches, coastal caves and other sites should til 2004 in the NW Mediterranean, upper graph: the
be periodically monitored, and the dates of arrival and dashed line represents the annual mean NW Medi-
of the start of the breeding (nesting) season should be terranean sea surface temperature maxima (1ºC)
recorded for each species. for the same period. (From Diaz-Almela et al., 2007).

32 COLLECTION