The current reduction of oceanic pH is affecting the saturation state of seawater with respect to calcite and aragonite with heavy consequences for marine calcifiers as shown by experiments using mostly planktonic organisms and corals. However we need more studies using common shallow water calcifiers in order to be able to predict changes in biodiversity and abundance in coastal areas. Today I will present data from a study in progress using a widely distributed bryozoan from the northern Atlantic coasts.
Bryozoans have been successfully used in studies of coastal pollution and in general ecological research as indicators of changes in bottom communities. Preliminary data show that they can also be used in climate change studies as early indicators of switches in carbonate regimes.
The bryozoan Flustra foliacea (L.) is well studied due to its use as a source of the biological active compound Flustramine thus being a suitable subject to study changes in calcification due to ocean acidification. This species forms dense thickets on the seafloor and the bi-mineralic composition of its skeleton should show the differential influence of changes in oceanic pH. Profiles in colonies from the North and Baltic Seas (European North Atlantic basin) from collections spawning several years were studied to assess growth rates, wall structure and wall preservation. Zooid frontal area and zooid shape indexes show significant differences in colony and zooid sizes in both areas despite the assumed low genetic divergence of these populations. Preliminary data also indicates that zooid size is stronger related to temperature rather than food availability.
Morphometric results were compared with data from geochemical composition, dissolution levels and Mg/Ca fluctuations in the same colonies to assess carbonate secreting capacity of Flustra under ocean acidification conditions. Obtained results are being tested in experiments using variable pH/pCO2 conditions. Further studies include analyses of museum material spawning over 200 years to test effects of ocean acidification and temperature on growth and calcification level since pre-industrial times.
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