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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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The western Mediterranean Sea, showing the surveyed localities of Ircinia fasciculata.
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pone-0020211-g001: The western Mediterranean Sea, showing the surveyed localities of Ircinia fasciculata.

Mentions: Quantitative surveys on the sponge mortality were carried out in two Marine Protected Areas in the western Mediterranean Sea: Cabrera National Park (Balearic Islands, Spain, hereafter Cabrera NP) and Reserve Naturelle de Scandola (Corsica, France, hereafter Scandola RN) (Fig. 1). Quantitative assessments of sponge population's status started in 2007 in Cabrera NP and were extended in 2008 to Scandola RN till late summer 2010. After the first observation of mortality signs in October 2008, qualitative surveys (presence/absence) of mortality (presence of partial or total necrosis) were carried out in six other zones encompassing the Spanish and French coasts (Table 1; Fig. 1). Finally, sponge mortality recorded by other research teams in several areas of western Mediterranean was also compiled to assess the geographical extent of the sponge die-offs (Table 1).


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)

The western Mediterranean Sea, showing the surveyed localities of Ircinia fasciculata.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0020211-g001: The western Mediterranean Sea, showing the surveyed localities of Ircinia fasciculata.
Mentions: Quantitative surveys on the sponge mortality were carried out in two Marine Protected Areas in the western Mediterranean Sea: Cabrera National Park (Balearic Islands, Spain, hereafter Cabrera NP) and Reserve Naturelle de Scandola (Corsica, France, hereafter Scandola RN) (Fig. 1). Quantitative assessments of sponge population's status started in 2007 in Cabrera NP and were extended in 2008 to Scandola RN till late summer 2010. After the first observation of mortality signs in October 2008, qualitative surveys (presence/absence) of mortality (presence of partial or total necrosis) were carried out in six other zones encompassing the Spanish and French coasts (Table 1; Fig. 1). Finally, sponge mortality recorded by other research teams in several areas of western Mediterranean was also compiled to assess the geographical extent of the sponge die-offs (Table 1).

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