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Baltic Sea Barnacles: Preparing Themselves for the Future

Reference
Pansch, C., Nasrolahi, A., Appelhans, Y.S. and Wahl, M. 2012. Impacts of ocean warming and acidification on the larval development of the barnacle Amphibalanus improvisus. Journal of Experimental Marine Biology and Ecology 420-421: 48-55.
In a study published in the Journal of Experimental Marine Biology and Ecology, Pansch et al. (2012) write that "the world's oceans are warming and becoming more acidic," noting that "both stressors, singly or in combination, impact marine species," and suggesting that "ensuing effects might be particularly serious for early life stages." They also state that to date, "most studies have focused on ocean acidification (OA) effects in fully marine environments, while little attention has been devoted to more variable coastal ecosystems, such as the Western Baltic Sea." And since they indicate that "natural spatial and temporal variability of environmental conditions such as salinity, temperature or CO2 impose more complex stresses upon organisms inhabiting these habitats, species [living there] can be expected to be more tolerant to OA (or warming) than fully marine taxa."

In exploring this hypothesis, Pansch et al. acquired data on the variability of temperature and pH within the inner Kiel Fjord of Schleswig-Holstein, Germany, as well as on "the responses of the barnacle Amphibalanus improvisus from this habitat to simulated warming and OA during its early development." This they did by exposing A. improvisus nauplii (the first larval stage of many crustaceans) and cyprids (the second larval stage of barnacles) to different temperatures (12, 20 and 27°C) and CO2 (nominally 400, 1250 and 3250 ppm) treatments for eight and four weeks, respectively," while "survival, larval duration and settlement success were monitored."

So what did they find? First of all, the four researchers found a prolongation of the nauplius phase that they acknowledge could "lead to a mismatch of the larvae with their phytoplankton prey." However, they note that any climate-alarmist-predicted increase in seawater temperature would likely "accelerate nauplii development and, thus, may buffer OA effects," and they say that such results have actually been observed "in sea urchin larvae and oysters, where higher temperatures mitigated negative effects of OA," citing the work of Sheppard Brennand et al. (2010) and Waldbusser et al. (2011). In their study, on the other hand, they found that things were just the opposite, indicating that "warming negatively impacted cyprid survival," but that "OA counteracted these negative effects."

"It should also be stressed," as they continue, "that only the most severe OA level applied herein (3250 ppm CO2) had occasional effects, whereas the OA conditions as predicted by the end of this century (1250 ppm CO2) in most cases did not affect A. improvisus larvae." In addition, and "interestingly," they report that "the major release of larvae and thus, development, settlement and first intense calcification in A. improvisus occurs during early summer when pH is lowest." And they add that "A. improvisus is also found in stands of the brown macroalga Fucus spp. where 2500 ppm CO2 (pH 7.4) can be measured," and they write that that "another barnacle species, Chthamalus stellatus, was shown to survive and grow at extremely low mean pH of 6.6 in the vicinity of volcanic CO2 vents in Ischia, Italy (Hall-Spencer et al., 2008)."

In summing things up, Pansch et al. write that "given their present wide tolerance and the possibility to adapt to shifting environmental conditions over many generations, barnacles (A. improvisus) from the Western Baltic Sea might be able to overcome OA as predicted by the end of this century." And, "supporting this," they note that Parker et al. (2011) have shown "selectively bred lines of the estuarine oyster Saccostrea glomerata to be more resilient to OA than wild populations." Consequently, as in so many other cases of knee-jerk predictions of impending CO2-induced catastrophe, both global warming and ocean acidification appear not to be the quite the demons they have been made out to be within another coastal marine-life setting.

Additional References
Hall-Spencer, J.M., Rodolfo-Metalpa, R., Martin, S., Ransome, E., Fine, M., Turner, S.M., Rowley, S.J., Tedesco, D. and Buia, M. 2008. Volcanic carbon dioxide vents show ecosystem effects of ocean acidification. Nature 454: 96-99.

Parker, L.M., Ross, P.M. and O'Connor, W.A. 2011. Populations of the Sydney rock oyster, Saccostrea glomerata, vary in response to ocean acidification. Marine Biology 158: 689-697.

Sheppard Brennand, H., Soars, N., Dworjanyn, S.A., Davis, A.R. and Byrne, M. 2010. Impact of ocean warming and ocean acidification on larval development and calcification in the sea urchin Tripneustes gratilla. PLoS One 5: e11372.

Waldbusser, G.G., Voigt, E.P., Bergschneider, H., Green, M.A. and Newell, R.I.E. 2011. Biocalcification in the eastern oyster (Crassostrea virginica) in relation to long-term trends in Chesapeake Bay pH. Estuaries and Coasts 34: 221-231.

Archived 6 November 2012