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Monitoring Populations of Xestospongia muta
Recruitment & Mortality
After several years of study, we are beginning to see patterns of recruitment and mortality. Overall, total number of sponges has increased in all sites since 1999. New, small recruits (right) are regularly found in low numbers. A larger recruitment event was observed in Fall 1999, just one year after a mass mortality event linked to Hurricane Georges. In total, we have observed 20% mortality in X. muta, over half of which is mortality of new recruits.
Growth & Tissue Recovery
Determining sponge growth is the most difficult aspect of this study, because these sponges are highly amorphous. By analyzing paired side and top digital photos of sponges over time, we have documented several instances of ~30% volume regrowth of medium-sized sponges over 18 months following severe tissue loss by line damage (sponge AAC below), and also have found golfball- to baseball-sized recruits appearing suddenly between 6 mo visits. Drastic changes in the size of medium to large-sized sponges have not been evident, however, suggesting that sponge growth may be very gradual or possibly episodic.