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Marine chemical ecology
Giant barrel sponge Xestospongia muta
Marine invertebrate larval
Photographic guide to sponges of
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Bleaching in Xestospongia muta:
Tissues of X. muta contain cyanobacterial symbionts
belonging to the Synechococcus-Prochlorococcus clade (Gómez et al.
2004; Steindler et al. 2005) that impart the reddish-brown to brown-gray
coloration to the sponge. In addition, the cyanobacteria may be responsible for
the translocation of carbon, nitrogen and phosphorous to the host sponge
(Wilkinson 1983) which likely enhances sponge growth (Thacker 2005).
|Reports of bleaching, or loss of pigmentation, of X. muta, along with
other symbiont-containing sponges, began to appear along with reports of coral
bleaching events over a decade ago (Vincente 1990). In some cases, bleached
sponges deteriorated and disintegrated; moreover, bleached X. muta were
more susceptible to predation by parrotfishes and generalist predators (Dunlap &
Bleaching and subsequent mortality has since been observed throughout the
Caribbean (Nagelkerken et al. 2000) and has also been reported for an analogous
species, Xestospongia testudinaria, on reefs in Australia. To date, there
has been no systematic investigation of mortality due to sponge bleaching, or
its impact on sponge distributions and abundances.
We have observed regular bleaching of X. muta at all our transect sites.
Sponges may only become pale, or at the extreme, nearly completely white. Cyclic
bleaching is common, affecting as many as 86% of the sponges within transects
during a given sampling period, although adjacent sponges are often dissimilarly
affected. Cyclic bleaching is usually not fatal and sponges recover over time.
Many of the sponges within our study sites exhibit intense bleaching during the
fall but had recovered their pigmentation by the following spring. Sponge AFL,
below, was bleached in October 2000 and had recovered seven months later.
Another example, sponge ABH also exhibited bleaching and recovery within two
The cause of cyclic bleaching in X. muta remains unclear.
Bleaching is less prevalent in sponges at shallow sites, suggesting that high
seawater temperatures are not responsible. Some evidence suggests that cyclic
bleaching may be tied to post-reproductive stress.
Fatal bleaching appears to
be a separate phenomenon from cyclic bleaching. Fatal bleaching is a
complete whitening of sponge tissue and results in large amounts of tissue loss
or complete sponge mortality.
Fatal bleaching has been associated with a
distinctive “orange band” separating mildly bleached and completely bleached
portions of tissue as the syndrome progresses. Tissues of fatally
bleached sponges are vigorously consumed by both spongivorous and generalist
predatory fishes (Dunlap & Pawlik 1998). "Sponge orange-band" (SOB) syndrome
may be a very extreme form of cyclic bleaching, but more likely is associated
with pathogenesis. We are working with collaborators to further investigate
Dunlap, M., Pawlik, J.R. 1998.
Spongivory by parrotfishes in Florida mangrove and reef habitats. Mar. Ecol.
Gómez, R., Erpenbeck, D., Van
Dijk, T., Richelle-Maurer, E., Devijver, C., Braekman, J.C., Woldringh, C., Van
Soest, R.W.M. 2004. Identity of cyanobacterial symbionts of Xestospongia muta.
Boll. Mus. Ist. Biol. Univ. Genova 66-67: 82-83
Nagelkerken, I., Aerts, L., Pors, L. 2000. Barrel sponge bows out. Reef
Steindler, L. Hucheon, D, Avni,
A, Ilan, M. 2005. 16S rRNA phylogeny of sponge associated cyanobacteria. App.
Environ. Microbiol. 71:4127-4131
Thacker, R.W. 2005. Impacts of shading on sponge-cyanobateria symbioses: a comparison between
host-specific and generalist associations. Integr. Comp. Biol. 45: 369-376.
- Vincente, V.P. 1990.
Response of sponges with autotrophic endosymbionts during the coral-bleaching episode in
Puerto Rico (West Indies). Coral Reefs 8: 199-202.
C.R. 1983a. Net primary productivity in coral reef sponges. Science
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