There is a
developmental sensitivity to pH for most aquatic organisms. Ocean acidification
due to increasing amounts of carbon dioxide is a current and future problem for
organisms with the gradual lowering of the ocean pH. Carbon dioxide increases
also can affect freshwater systems, but episodic acidity causes more problems
with organisms in poorly buffered streams, ponds and lakes.
In this paper, the effects of transient acid spikes on development of Lepomis sunfish
were studied by combining field work with laboratory studies. Lepomis sunfish
eggs were collected from rocks on nests in two freshwater ponds and tested for
their resistance to laboratory induced transient acid spikes. Fertilized eggs
on rocks within the same nest were used for each pH transient experiment. Egg
masses on one rock from the nest were used as a control while egg masses on
another rock were exposed to transient acid spikes. Overall, 3163
early-life-stage Lepomis individuals
(2459 eggs, 309 pre-swim-up larvae, and 395 Post-Swim-Up fry) taken from seven
different nests were exposed to acid conditions in these experiments; another
1592 control individuals from the same nests were grown to the Post-Swim-Up
stage in non-acid conditions.
The experiment findings indicated that various stages of development
showed different responses to the acidic effects. The survival was high in the
controls (94.0%); survival for groups exposed to acid water ranged from 85.5%
to 0% (data pooled for groups with the same pH, duration of acid exposure, and
life-stage). The major stages studied were fertilized egg, hatched with
attached yolk sac, and free swimming with gills. The acid sensitivity followed
development stages with the most acid sensitive stage being free swimming with
gills.
In conclusion, this fieldwork-laboratory data chain supports earlier
field studies, providing the final link in an evidentiary chain showing the
effects of transient acid spikes on Lepomis hatching profiles
in freshwater ponds.
Article
by William G. Hagar, et al, from University
of Massachusetts Boston, Boston, USA.
Full
access: http://mrw.so/1aHM3G
Image
by Matthieu Berroneau, from Flickr-cc.
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