Posted by: oikosasa | December 10, 2012

Winners in a changing world

Invasive species may actually increase resistance to climate changes. Celia Olabarria and co-workers studies this interaction in marine macroalgal assemblages.  Now on early View: Response of macroalgal assemblages from rockpools to climate change: effects of persistent increase in temperature and CO2

Here is a short summary by the authors:

Climate change is one of the greatest threat  that marine systems are facing. Changes in ocean temperature, biogeochemistry, sea level, UV radiation, and circulation patterns have been identified over the last few decades. Specifically, warmer and more acidic oceanic water (due to the increase of CO2 in the atmosphere and oceans) are of great concern to marine biologists. Non-indigenous species are also impacting marine communities around the world at an unprecedented rate. These species are often ecosystem engineers (e.g. brown canopy algae) that can replace native species and their functional role in the ecosystem, or modify habitat characteristics and food sources for consumers. We do not have information about how invaded communities will respond to climate change compared to non-invaded communities.

Marine macroalgae that dominate the rocky intertidal in most oceans, and in temperate and Polar regions cover rock surfaces in the shallow subtidal, make a substantial contribution to marine primary production (10%) and describe important ecological functions. They may be also actively involved in lowering global warming and climate change. Research about effects of different climate change scenarios on macroalgae has found quite variable and species-specific responses. Until now, most research has focused on the effects of climate change on single macroalgae species, rather than on whole communities. While this approach is useful for understanding species-specific mechanisms behind the effects of environmental changes, it ignores species interactions which may buffer or amplify individual responses thereby altering predicted assemblage-level responses.

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Macroalgal assemblages from rock pools are interesting model systems to study climate-driven changes because they are composed of different morpho-functional groups of varying diversity and identity of species. Despite coping with daily and seasonal variations in pH and temperature, their response to more persistent changes are unknown. We were able to manipulate temperature and CO2 concentration in mesocosms to evaluate how these to climate-change factors affected several ecosystem functioning variables at both individual and assemblage level. For that, we used synthetic macroalgal assemblages of varying diversity and identity of species resembling those characteristic of rock pools.

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Results revealed that the increase in temperature and CO2 concentration may interact and affect the functioning of coastal macroalgal assemblages, with effects largely dependent on species composition of assemblages. Although the effects of assemblage richness were mostly negligible, significant differences were found between the response of native and invaded assemblages. Data suggested that  invaded assemblages might be more resistant in the predicted future scenario of climate change. This paper emphasises the importance of using multiple stressors-study approaches at community level to get better predictions of climate change impacts on ecosystem functioning.

Photo: F. Arenas and M. Matias

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