Competition
Competition

Sessile organisms
Competition in sessile reef organisms takes 3 forms: 1) preemptive, where through its presence one organism prevents another from occupying the same space, 2) overgrowth, where one organism, like a seaweed, grows over or otherwise crowds out and kills another organism like a coral, and 3) chemical, where through release of a toxic material one organism prevents another from settling and surviving. Access each type via the icons. hot button for preemptive competition part of Biology of Caribbean Coral Reefs website hot button for preemptive competition part of Biology of Caribbean Coral Reefs hot button for overgrowth competition part of Biology of Caribbean Coral Reefs hot button for chemical competition part of Biology of Caribbean Coral Reefs

Overgrowth competition

hot buttons for overgrowth competition hot button for fire-coral overgrowth competition hot button for sponges-overgrowth competition hot button for coral/zoanthid overgrowth competition hot button for tunicate-overgrowth competition hot button for algae/cyanophyte-overgrowth competition
Overgrowth by tunicates is considered here, while information on other taxa can be accessed via the icons.

Tunicates


seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of tunicate overgrowing a coral "The purple growth is a colonial tunicate of the didemnid type, and it seems to be doing very well in overgrowing the two types of coral." - Turks & Caicos 2005

photograph of colonial tunicate overgrowing a sponge
Most or perhaps all colonial tunicates are superior competitors for space. In areas of the Caribbean, mat tunicates (didemnids) commonly overgrow sponges and corals, including several dominant reef-building species. The following photographs show details of these interactions:

NOTE Family Didemnidae comprises several similar-looking species that are difficult to distinguish except by microscopic structure. The ones shown here are mostly Trididemnon sp.

 

 

Here, a mat tunicate Trididemnum solidum
is overgrowing a sponge. Note that the
sponge seems to be degraded, although it is
not obvious that the tunicate is the cause 1.3X

 
photograph of colonial tunicate with a boring sponge

A mat tunicateTrididemnum solidum and a
boring sponge Siphonodictyon coralliphagum
mutually tolerate one-another's presence.
Note the lack of tissue damage on both 0.75X

photographs showing competitive interactions between colonial tunicates and fire corals
photographs showing competitive interactions between colonial tunicates and various cnidarians
Most overgrowth by mat tunicates Trididemnum solidum in Bonaire, Netherlands Antilles occurs at depths of about 20m (6% bottom cover in this particular study). At 10m its cover is half this and, at 5m, is less than 1%. In the locations surveyed, most common species overgrown are boulder corals Montastraea spp., lettuce corals Agaricia agaricites, and fire corals Millepora spp. (see photographs). Sommer et al. 2010 29: 245; photographs courtesy the authors.
photograph of mat tunicate Trididemnum solidium overgrowing a boulder coral Montastraea annularis in Bonaire photograph of mat tunicate Trididemnum solidium overgrowing a lettuce coral Agaricia agaricites in Bonaire photograph of mat tunicate Trididemnum solidium overgrowing fire coral Millepora sp. in Bonaire
Mat tunicate Trididemnum solidum overgrowing a boulder coral Montastraea annularis Mat tunicate Trididemnum solidum overgrowing a lettuce coral Agaricia agaricites Mat tunicate Trididemnum solidum overgrowing fire coral Millepora sp.

If you've seen all the examples of overgrowth competition presented in BCCR, then you should recognise all the photos below. So, which of these sessile species is the"no-holds-barred-superior-invertebrate-overgrowth-competitor" in the entire Caribbean region? Four of the entries are specific, while two refer to a general taxon (gorgonian and coral) with an example species. When you've decided on a choice or two, CLICK HERE for explanations.

 
photograph of fire coral
photograph of chicken-liver sponge photograph of encrusting zoanthid photograph of gorgonian photograph of cathedral coral photograph of mat tunicate
Fire coral Millepora sp. 0.15X Chicken-liver sponge Chon- drilla nucula 0.1X Encrusting zoanthid Palythoa caribaeorum 0.25X Gorgonian: e.g., Pseudopterogorgia sp. 0.05X Coral: e.g., cathedral coral Dendrogyra cylindricus 0.1X Mat tunicate possibly Trididemnum solidum 0.3X

RETURN TO TOP