Ecological effects of Diadema mass mortality. [Final Outline]

This discussion topic submitted by Jamie Engman ( at 11:46 am on 5/1/00. Additions were last made on Monday, May 15, 2000.

Ecological effects of Diadema mortality.

In 1983, an unprecedented, Caribbean-wide dieoff of the urchin Diadema antillarum occurred. Densities of this herbivore decreased drastically in reef environments throughout the region. The resulting reduction in grazing pressure has been implicated in an observed increase in fleshy algal cover on coral reefs. The actual relationship between reduced urchin grazing and increase in algal cover is still open to debate.

I. Introduction: Diadema ecology and life history
a. Habitat
b. Behavior
II. The Mortality Event
a. First observations
b. Symptoms
c. Geographic progression of epidemic
d. Intensity of mortality
III. Apparent Ecosystem Effects
a. Increase in fleshy algae
i. Diadema grazing studies
1. Carpenter 1981
b. Loss of coral cover.
IV. Questions Remaining
a. Cause of disease
b. Recovery of Diadema populations
c. Top down versus bottom up control
i. Lapointe 1997.
1. overfishing was severe long before recent blooms
2. Time line inconsistencies
3. Fore reef involvement
ii. McClanahan and Muthiga 1998
d. Disease-related coral loss
e. Jackson’s ideas

Carpenter, RC. 1981. Grazing by Diadema antillarum Phillippi and its effects on the benthic algal community. J. Mar. Res 39:747-765.

Hughes, TP, Reed DC, Boyle M-J. 1987. Herbivory on coral reefs: community structure following mass mortalities of sea-urchins. J Exp Mar Biol Ecol 113:39-59.

Hughes, TP 1994. Catastrophes, Phase Shifts, and Large-Scale Degradation of a Caribbean Coral Reef. Science 265:1547-1551.

Jackson, JBC. 1997. Reefs since Columbus. Proc. 8th Int. Coral Reef Symp. 1:97-106.

Lapointer BE 1997. Nutrient thresholds for bottom-up control of mactoalgal blooms on coral reefs in Jamaica and southeast Florida. Limnol. Oceanogr 42:1119-1131.

Lessios, HA. 1988. Mass Mortality of Diadema antillarum in the Caribbean: What have we learned? Ann. Rev. Ecol. Syst. 19:371-393.

Lessios, HA. 1988. Population dynamics of Diadema antillarum (Echinodermata: Echinoidea) following mass mortality in Panama. Mar. Biol. 99: 515-526.

Lessios, HA. 1995. Diadema antillarum 10 years after mass mortality: Still rare, despite help from a competitor. Proc. Royal Soc. London Ser. B. 259: 331-337.

Lessios, HA, JD Cubit, DR Robertson, MJ Shulman, MRParker, SD Garrity, and SC Levings. 1984. Mass mortality of Diadema antillarum on the Caribbean coast of Panama. Coral Reefs 3: 173-182.

Liddell WD and SL Ohlhorst. 986. Changes ini tbe benthic community compositioin following the mass mortality of Diadema at Jamaica. J Exp Mar Biol Ecol 95:271-278.

McClanahan, TR and NA Muthiga. 1998. An ecological shift in a remote coral atoll of Belize over 25 years. Envir. Conserv. 25: 122-130.

Woodley, JD. 1999. Sea-urchins exert top-down control of macroalgae on Jamaican Coral Reefs. Coral Reefs 18:192-193.

Yoshioka, PM 1996. Variable recruitment and its effects on the population and community structure of shallow-water gorgonians. Bull. Mar. Sci. 59: 433-443.

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