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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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Mean densities of Ircinia fasciculata (a) and Sarcotragus spinosulum (b) recorded in Cabrera NP (circles, C) and Scandola RN (triangles, S) during the monitoring period.Bars represent standard errors. Mean concentrations, which were not significantly different in a Tukey test, are joined by horizontal lines. N =  number of specimens sampled.
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pone-0020211-g006: Mean densities of Ircinia fasciculata (a) and Sarcotragus spinosulum (b) recorded in Cabrera NP (circles, C) and Scandola RN (triangles, S) during the monitoring period.Bars represent standard errors. Mean concentrations, which were not significantly different in a Tukey test, are joined by horizontal lines. N =  number of specimens sampled.

Mentions: In both sites, densities of I. fasciculata decreased dramatically from around 10 (in Scandola RN) and 7 (in Cabrera NP) specimens·m−2 before the mortality event (summer 2008) to less than 1 specimens·m−2 at the end of autumn 2010 (Fig. 6a). The ANOVA analyses showed that time had a significant effect on I. fasciculata densities in Cabrera NP and Scandola RN, which were significantly lower in July and October 2009 and July 2010, after the first outbreak (Fig. 6a, Table 2). In Cabrera NP, where three sites were monitored, no significant differences in I. fasciculata densities were observed between sites (populations); neither was the interaction between locality and time significant (Table 2), indicating that the pattern of density losses was similar everywhere (Table 2).


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)

Mean densities of Ircinia fasciculata (a) and Sarcotragus spinosulum (b) recorded in Cabrera NP (circles, C) and Scandola RN (triangles, S) during the monitoring period.Bars represent standard errors. Mean concentrations, which were not significantly different in a Tukey test, are joined by horizontal lines. N =  number of specimens sampled.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0020211-g006: Mean densities of Ircinia fasciculata (a) and Sarcotragus spinosulum (b) recorded in Cabrera NP (circles, C) and Scandola RN (triangles, S) during the monitoring period.Bars represent standard errors. Mean concentrations, which were not significantly different in a Tukey test, are joined by horizontal lines. N =  number of specimens sampled.
Mentions: In both sites, densities of I. fasciculata decreased dramatically from around 10 (in Scandola RN) and 7 (in Cabrera NP) specimens·m−2 before the mortality event (summer 2008) to less than 1 specimens·m−2 at the end of autumn 2010 (Fig. 6a). The ANOVA analyses showed that time had a significant effect on I. fasciculata densities in Cabrera NP and Scandola RN, which were significantly lower in July and October 2009 and July 2010, after the first outbreak (Fig. 6a, Table 2). In Cabrera NP, where three sites were monitored, no significant differences in I. fasciculata densities were observed between sites (populations); neither was the interaction between locality and time significant (Table 2), indicating that the pattern of density losses was similar everywhere (Table 2).

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