Mass Mortality of the West-Indian Echinoid Diadema antillarum (Echinodermata: Echinoidea): A Natural Experiment in Taphonomy

Abstract

During 1983, populations of the common long-spined echinoid Diadema antillarum were decimated by disease throughout the Caribbean and as far north as Bermuda. The sudden incorporation of tests and spines of large numbers of urchins into surficial reef sediments suggests that sediment composition may be altered with respect to the amount of echinoderm material present. The hypothesis that a clear record of the mass mortality might be preserved in the reef sedimentary record was tested at Bonaire, Netherlands Antilles, where the mortality was reported to have occurred in November, 1983. Samples taken along a series of reef profiles and at specific depths within surficial reef sediments were analyzed for total echinoderm content and the proportion of the echinoderm fraction composed of skeletal elements of D. antillarum. The echinoderm fraction is virtually unchanged from pre-mortality levels as reported by other workers. Echinoderms overall are minor contributors to reef sediments, and skeletal elements of Diadema account for a large proportion of the echinoderm fraction. The lack of a strong signal of the event demonstrates the inadequacy of the reef sedimentary record to preserve this short-term, ecologically significant event.

A 3000 year record of Caribbean reef urchin communities reveals causes and consequences of long‐term decline in Diadema antillarum

“…However, the millennial-scale rarity of Diadema across four cores and over periods of varying coral community composition indicates microhabitat effects are not a significant cause of rarity. Fourth, urchin spines found in our cores may have been transported downslope from shallower waters post-mortem (Greenstein 1989), which may account for the relatively high abundance of shallow water-dwelling Lytechinus and Tripneustes. However, this would not explain the rarity of Diadema spines compared to those of E. viridis because these taxa occupy similar depth zones (Shulman 1990).…”

Sediment accumulation, stratigraphic order, and the extent of time-averaging in lagoonal sediments: a comparison of 210Pb and 14C/amino acid racemization chronologies

“…Time-averaging on the order of 19 to 125 yrs (1r and 2r, respectively) implies that a recent mass die-off will be mixed with the remains from normal annual mortality of *19 yrs. While time-averaging and bioturbation need to be quantified on a site specific basis, it is illustrative to examine the classic study of Diadema mass mortality (Greenstein 1989) in the context of what we now know about time-averaging in coral reef-associated sediment. Assuming a stable population size and an average life span of 4 yrs (Ogden and Carpenter 1987) implies a population turnover of 25 % per annum.…”

Geological Approaches to Coral Reef Ecology

“…For example, the mass mortality of Diadema antillarum throughout the Caribbean and tropical western Atlantic during 1983 to 1984 continues to affect coral reef communities adversely in many areas (Smith and Ogden 1994). However, when constituent particle analyses of reef sediments obtained after the mortality event occurred in Bonaire, Netherlands Antilles, and Andros Island, Bahamas, were compared to published reports of the composition of reef sediments examined prior to the mortality event (Greenstein 1989;Greenstein and Meyer 1990), no evidence of a layer rich in echinoderm material was obtained. These results underscore the rapidity with which echinoid material was reworked and diluted by additional sediment derived from the reef, considering that innumerable echinoids, each possessing a skeleton of thousands of elements, were observed to decay and disarticulate on the reef substrate over a relatively short interval of time (Greenstein 1989).…”