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Impact of ocean acidification on Corallium rubrum (L. 1758): an experimental approach

Ocean acidification refers to the decrease in pH resulting from the increased dissolution of atmospheric carbon dioxide (CO2) in the seawater. Increasing evidence suggests that ocean acidification might have an impact on several marine species. However, the information available on the effects of acidification on gorgonians of the Mediterranean Sea is almost completely lacking. The red coral Corallium rubrum plays a prominent role in sustaining high levels of biodiversity and ecosystem functioning and is affected both by climate change and local over-harvesting. To evaluate possible effects on biocalcification, growth and polyps’ activity of C. rubrum, colonies collected from Portofino Marine Protected Area have been exposed to different pCO2 conditions through bubbling under experimental conditions. Three levels were used: a control (372 ppm) and two pCO2 scenarios (734 and 975 ppm) expected to occur by the end of this century by the Intergovernmental Panel on Climate Change. Results showed that calcification and growth rates as well as activity of coral polyps are significantly affected by increasing pCO2. The results of the present study also indicate that ocean acidification has the potential to negatively impact the energy allocation, metabolic and ingestion rates, reproductive output and recruitment success. All these variables have the potential to determine shifts in population size structure of this relevant species, and may contribute to a substantial decline in size and distribution of C. rubrum populations in the future.

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6    1. Introduction 1.1. Ocean acidification Over the past 250 years, atmospheric carbon dioxide (CO 2 ) levels increased by nearly 40%, from pre-industrial levels of approximately 280 ppm (parts per million) to nearly 384 ppm in 2007 (Solomon et al. 2007). This rate of increase, driven by human fossil fuel combustion and deforestation, is at least an order of magnitude faster than that occurred for millions of years (Doney & Schimel 2007), and the current concentration is higher than experienced on Earth for at least the past 800,000 years (Luthi et al. 2008). Rising atmospheric CO 2 is tempered by oceanic uptake, which accounts for nearly a third of anthropogenic carbon added to the atmosphere (Sabine et al. 2004), and without which atmospheric CO 2 would be approximately 450 ppm today: a level of CO 2 that would have led to even greater climate change than that presently experienced. Ocean CO 2 uptake, however, is not benign; it causes pH reductions and alterations in fundamental chemical balances that together are commonly referred to as ‘ocean acidification’. Since climate change and ocean acidification are both caused by increasing atmospheric CO 2 , acidification is commonly referred to as the ‘other CO 2 problem’ (Doney et al. 2009). Ocean acidification is a predictable consequence of rising atmospheric CO 2 and does not suffer from uncertainties associated with climate change forecasts. Absorption of anthropogenic CO 2 , reduced pH, and lower calcium carbonate (CaCO 3 ) saturation in surface waters are well predicted by models and verified by hydrographical surveys and time series data (Caldeira & Wickett 2003, Caldeira & Wickett 2005, Orr et al. 2005, Solomon et al. 2007, Feely et al. 2009). At the Hawaii Ocean Time-Series (HOT) station ALOHA the growth rates of surface

Laurea liv.II (specialistica)

Facoltà: Scienze

Autore: Ulisse Cardini Contatta »

Composta da 80 pagine.

 

Questa tesi ha raggiunto 155 click dal 05/09/2013.

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