Cognitive dysfunction and risk assessment by prey: predictable changes in global climate have unpredictable effects
2012; Wiley; Volume: 26; Issue: 3 Linguagem: Inglês
10.1111/j.1365-2435.2011.01956.x
ISSN1365-2435
Autores Tópico(s)Coral and Marine Ecosystems Studies
ResumoFunctional EcologyVolume 26, Issue 3 p. 551-552 FE SPOTLIGHTFree Access Cognitive dysfunction and risk assessment by prey: predictable changes in global climate have unpredictable effects Brian D. Wisenden, Corresponding Author Brian D. Wisenden Correspondence author. E-mail: wisenden@mnstate.eduSearch for more papers by this author Brian D. Wisenden, Corresponding Author Brian D. Wisenden Correspondence author. E-mail: wisenden@mnstate.eduSearch for more papers by this author First published: 03 February 2012 https://doi.org/10.1111/j.1365-2435.2011.01956.xCitations: 5AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Anthropogenic impacts at the biosphere level, already well underway, show rapidly increasing concentrations of CO2 in the atmosphere. Data released in November 2011 show mean global CO2 levels of 388·92 ppm, up from 228 ppm in 1979, and a 40% increase in CO2 since the beginning of the industrial revolution in the mid-1700s (http://www.esrl.noaa.gov/gmd/ccgg/trends/). Much attention has focused on the effects of anthropogenic CO2 on mean global temperature and the resulting melting of polar ice caps, changes in sea level and changing patterns and intensity of weather events (e.g. Reaser, Pomerance & Thomas 2000). The chemical reactivity of CO2, that is, the suppression of pH, has only recently started to receive attention (Munday et al. 2009; Dixson, Munday & Jones 2010; Cripps, Munday & McCormick 2011; Ferrari et al. 2011). Shifts in pH have a direct effect on the physiology and behaviour of aquatic life and potentially disrupt finely tuned ecological interactions. As abiotic parameters shift in response to global climate change, so too will selection in complex multispecies interactions. Predicting the magnitude and direction of selection is a desirable goal, but the most recent data from Ferrari et al. (2012) indicate that predicted changes in global climate will have unpredictable effects on the functional ecology of marine ecosystems. The aquatic environment is ideal for the solution and dispersal of chemical information. Aquatic animals use chemical information for all the major ecological functions: navigation, finding food, avoiding predators, finding mates and timing the simultaneous release of gametes with a spawning partner. Behavioural ecologists are well-positioned to explore how cues currently used for decision making by animals may be impacted by current and projected environmental changes. Initial work (Munday et al. 2009; Dixson, Munday & Jones 2010; Cripps, Munday & McCormick 2011; Ferrari et al. 2011) indicated that pH shifts resulting from elevated atmospheric levels of CO2 projected by climate models interfered with chemically mediated behavioural responses by one or more mechanisms: (i) alteration of the messenger molecules; (ii) impairment of receptors that detect the messenger molecules or (iii) impairment of cognitive processing of the information within decision-making processes in the brain of the fish. The current study (Ferrari et al. 2012) showed impaired responses to the predation threat presented in the visual modality. It is unlikely that one environmental variable, CO2 concentration, could similarly impair two separate sensory systems at the level of the visual and chemosensory receptors. These new data strongly suggest that the effect of CO2 is impairment of higher cognitive function where input of sensory information is integrated with decision-making algorithms that produce behavioural output. In other words, the results of the earlier studies may be explained entirely by effects of elevated CO2 on cognitive processing of information about predation risk, and not tied to any one sensory modality. With our current level of understanding of the effect of oceanic acidification on behaviour and cognition, it is nigh impossible to predict how cognitive dysfunction will affect complex marine ecosystems. This is especially true because not all prey species are affected equally (Ferrari et al. 2011) and we do not yet have data on the roles of learning, sensory adaptation or selection resulting from long-term exposure. It is thus essential that future research is directed at testing a broad range of marine taxa from multiple functional groups to better understand, anticipate and mitigate short- and long-term effects of oceanic acidification on the functional ecology of marine ecosystems. Oceanic acidification is more subtle and yet far more devastating than pH shifts that have occurred in freshwater systems as a consequence of anthropogenically acidified precipitation. Freshwater fishes generally show olfactory impairment (or perhaps cognitive dysfunction?) at pHs below 6·0 (Jones, Hara & Scherer 1985; Lemly & Smith 1985, 1987; Royce-Malmgren & Watson 1987; Leduc et al. 2004) but some freshwater species function normally down to pH 3 (Hara 1976). Oceanic pH has already dropped 0·1 pH units and is projected to be reduced by 0·3 units by the year 2050 and 0·5 units (i.e. more than a threefold increase in the concentration of hydrogen ions) by the year 2100 (Caldeira & Wickett 2003, 2005). Marine ecosystems are at greater risk from acidification because, unlike terrestrial and freshwater ecosystems, marine ecosystems have been chemically stable over evolutionary time. Consequently marine organisms, on the whole, lack the cellular physiological mechanisms to tolerate even small changes in pH (Ishimatsu, Hayashi & Kikkawa 2008; Pörtner 2008). Although specific predictions are difficult to make, it is certain that destabilization of functional ecological interactions will result in reduced community complexity, reduced species richness and reduced resilience of community stability in the face of natural and anthropogenic stressors. If this were a perfect world, the timing of this article, in the wake of the United Nations Climate Change Conference in Durban, South Africa, would stir renewed resolve among the political class to find international mechanisms to curb CO2 emissions. 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