Information for undergrads and
prospective grad students
Marine chemical ecology
Giant barrel sponge Xestospongia muta
Marine invertebrate larval
Photographic guide to sponges of
BIO 501: Science as a Profession
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Monitoring Populations of Xestospongia muta
In 1997, we began a pilot study monitoring populations of
X. muta on the coral reefs off Key Largo, FL. Three years later, with
the added use of the
habitat, we had a total of 4 monitoring
sites: 2 at 15 m depth on Pickles Reef and Conch Reef, and two deeper sites on
Conch Reef, at 20 m and 30 m. In Oct. 2006 using Tri-Mix Technical Diving,
we added a deep monitoring site at 50 m.
Each site consists of three 16 m radial transects, within
which each individual X. muta is uniquely identified and monitored over
time (right). Sites are visited twice a year, with data collected on recruitment,
mortality, growth, bleaching and disease. In addition, each sponge is
photographed, creating a photo library of over 5,000 images. As of May 2005,
617 sponges have been monitored and photographed.
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
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.
| Bleaching |