Geoscience Reference
In-Depth Information
5.4.1.2.4. Echinoderms
In contrast to mollusks, echinoderms are, in general, relatively
resistant to ocean acidification. No lethal mid-term impact has been
observed, but sublethal effects have been reported. For example,
positive modifications have been measured in sea urchins [RIE 09]
and brittle stars [WOO 08]. Other physiological alterations have been
observed such as a disruption in the acid-base balance [MIL 07], a
decrease of the efficiency of the immune system [HER 11], as well as
an increase in respiration associated with an imbalance in the growth of
tissues and calcification [WOO 08]. Echinoderms are, like mollusks,
meroplanktonic organisms; in other words, they have a planktonic
larval stage. Some experiments have shown a decrease in the sperm
motility of sea urchin [HAV 08] and holothurian [MOR 09],
suggesting a significant reduction of the fertility at low pH levels. Sea
urchin larvae and juveniles respond negatively with higher rates of
mortality [SHI 05]. However, these lethal effects are not always
observed (e.g. [DUP 10]). Embryos appear to be rather resistant to
elevated CO
2
and the first effects generally appear during the first
larva stage after hatching, most of the time with a delayed growth at
low pH levels (e.g. [MAR 11]).
5.4.1.3.
Unknowns and experimental approaches
Our understanding of the consequences of ocean acidification on
marine biology is restricted by the limited information available on the
response of communities and ecosystems over timescales
representative of the lifecycles of organisms and on the interaction
with other environmental changes, such as global warming. Most of
the data was collected during perturbation experiments performed on
species isolated from their natural environment, often in the
laboratory. It is not certain that the results of such experiments can
be extrapolated to natural systems due to the lack of information on the
impact of ocean acidification on ecological interactions, such as
predation, competition and mutualism.
Several approaches can be used to address this shortcoming.
Natural CO
2
gradients can provide valuable information. This is the
