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Sponge mass mortalities in a warming Mediterranean Sea: are cyanobacteria-harboring species worse off?

Cebrian E, Uriz MJ, Garrabou J, Ballesteros E - PLoS ONE (2011)

Bottom Line: A laboratory experiment confirmed that the cyanobacteria harbored by I. fasciculata displayed a significant reduction in photosynthetic efficiency in the highest temperature treatment.The sponge disease reported here led to a severe decrease in the abundance of the surveyed populations.It represents one of the most dramatic mass mortality events to date in the Mediterranean Sea.

View Article: PubMed Central - PubMed

Affiliation: Universitat de Girona, Facultat de Ciències, Departament de Ciències Ambientals, Girona, Spain. emma.cebrian@udg.edu

ABSTRACT
Mass mortality events are increasing dramatically in all coastal marine environments. Determining the underlying causes of mass mortality events has proven difficult in the past because of the lack of prior quantitative data on populations and environmental variables. Four-year surveys of two shallow-water sponge species, Ircinia fasciculata and Sarcotragus spinosulum, were carried out in the western Mediterranean Sea. These surveys provided evidence of two severe sponge die-offs (total mortality ranging from 80 to 95% of specimens) occurring in the summers of 2008 and 2009. These events primarily affected I. fasciculata, which hosts both phototrophic and heterotrophic microsymbionts, while they did not affect S. spinosulum, which harbors only heterotrophic bacteria. We observed a significant positive correlation between the percentage of injured I. fasciculata specimens and exposure time to elevated temperature conditions in all populations, suggesting a key role of temperature in triggering mortality events. A comparative ultrastructural study of injured and healthy I. fasciculata specimens showed that cyanobacteria disappeared from injured specimens, which suggests that cyanobacterial decay could be involved in I. fasciculata mortality. A laboratory experiment confirmed that the cyanobacteria harbored by I. fasciculata displayed a significant reduction in photosynthetic efficiency in the highest temperature treatment. The sponge disease reported here led to a severe decrease in the abundance of the surveyed populations. It represents one of the most dramatic mass mortality events to date in the Mediterranean Sea.

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Percentage of the summer period with temperatures above 23°C, 24°C, 25°C and 26°C in Cabrera NP (a) and above 23°C, 24°C and 25°C in Scandola RN (b).Data from SOMLIT (temperature sensors) data series.
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pone-0020211-g007: Percentage of the summer period with temperatures above 23°C, 24°C, 25°C and 26°C in Cabrera NP (a) and above 23°C, 24°C and 25°C in Scandola RN (b).Data from SOMLIT (temperature sensors) data series.

Mentions: Regarding temperature thresholds, in Cabrera NP the years 2008 and 2009 displayed higher percentages of time of exposition than in 2007 regardless the temperature threshold considered, although the percentage of time above 26°C showed the largest differences. In 2010, values were similar to those of the mortality years; however by then the density of populations of I. fasciculata were really low (see Impact of sponge disease section) preventing the assessment of sponge mortality (Figure 7a).


Sponge mass mortalities in a warming Mediterranean Sea: are cyanobacteria-harboring species worse off?

Cebrian E, Uriz MJ, Garrabou J, Ballesteros E - PLoS ONE (2011)

Percentage of the summer period with temperatures above 23°C, 24°C, 25°C and 26°C in Cabrera NP (a) and above 23°C, 24°C and 25°C in Scandola RN (b).Data from SOMLIT (temperature sensors) data series.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105983&req=5

pone-0020211-g007: Percentage of the summer period with temperatures above 23°C, 24°C, 25°C and 26°C in Cabrera NP (a) and above 23°C, 24°C and 25°C in Scandola RN (b).Data from SOMLIT (temperature sensors) data series.
Mentions: Regarding temperature thresholds, in Cabrera NP the years 2008 and 2009 displayed higher percentages of time of exposition than in 2007 regardless the temperature threshold considered, although the percentage of time above 26°C showed the largest differences. In 2010, values were similar to those of the mortality years; however by then the density of populations of I. fasciculata were really low (see Impact of sponge disease section) preventing the assessment of sponge mortality (Figure 7a).

Bottom Line: A laboratory experiment confirmed that the cyanobacteria harbored by I. fasciculata displayed a significant reduction in photosynthetic efficiency in the highest temperature treatment.The sponge disease reported here led to a severe decrease in the abundance of the surveyed populations.It represents one of the most dramatic mass mortality events to date in the Mediterranean Sea.

View Article: PubMed Central - PubMed

Affiliation: Universitat de Girona, Facultat de Ciències, Departament de Ciències Ambientals, Girona, Spain. emma.cebrian@udg.edu

ABSTRACT
Mass mortality events are increasing dramatically in all coastal marine environments. Determining the underlying causes of mass mortality events has proven difficult in the past because of the lack of prior quantitative data on populations and environmental variables. Four-year surveys of two shallow-water sponge species, Ircinia fasciculata and Sarcotragus spinosulum, were carried out in the western Mediterranean Sea. These surveys provided evidence of two severe sponge die-offs (total mortality ranging from 80 to 95% of specimens) occurring in the summers of 2008 and 2009. These events primarily affected I. fasciculata, which hosts both phototrophic and heterotrophic microsymbionts, while they did not affect S. spinosulum, which harbors only heterotrophic bacteria. We observed a significant positive correlation between the percentage of injured I. fasciculata specimens and exposure time to elevated temperature conditions in all populations, suggesting a key role of temperature in triggering mortality events. A comparative ultrastructural study of injured and healthy I. fasciculata specimens showed that cyanobacteria disappeared from injured specimens, which suggests that cyanobacterial decay could be involved in I. fasciculata mortality. A laboratory experiment confirmed that the cyanobacteria harbored by I. fasciculata displayed a significant reduction in photosynthetic efficiency in the highest temperature treatment. The sponge disease reported here led to a severe decrease in the abundance of the surveyed populations. It represents one of the most dramatic mass mortality events to date in the Mediterranean Sea.

Show MeSH
Related in: MedlinePlus