Coral Reef Science:  Development Highlights

Eric Borneman

This month, I cover several articles on global coral reef decline...

Hughes, T. P., Baird, A. H., Bellwood, D. R., Card, M., Connolly, S. R., Folke, C., Grosberg, R., Hoegh-Guldberg, O., Jackson, J. B. C., Kleypas, J., Lough, J. M., Marshall, P., Nyström, M., Palumbi, S. R., Pandolfi, J. M., Rosen, B., Roughgarden, J. 2003. Climate change, human impacts, and the resilience of coral reefs. Science. 301 (5635), p.929, 5p, 3 graphs, 2 maps, 1c.

Abstract:

The diversity, frequency, and scale of human impacts on coral reefs are increasing to the extent that reefs are threatened globally. Projected increases in carbon dioxide and temperature over the next 50 years exceed the conditions under which coral reefs have flourished over the past half-million years. However, reefs will change rather than disappear entirely, with some species already showing far greater tolerance to climate change and coral bleaching than others. International integration of management strategies that support reef resilience need to be vigorously implemented, and complemented by strong policy decisions to reduce the rate of global warming.

Pandolfi, John M., Bradbury, Roger H., Sala, Enric, Hughes, Terence P., Bjorndal, Karen A., Cooke, Richard C., McArdle, Deborah, McClenachan, Loren, Newman, Marah J. H., Paredes, Gustavo, Warner, Robert R., Jackson, Jeremy B. C. 2003. Global Trajectories of the Long-Term Decline of Coral Reef Ecosystems. Science 301 (5635), p. 955, 4p, 1 chart, 3 graphs.

Abstract:

Degradation of coral reef ecosystems began centuries ago, but there is no global summary of the magnitude of change. We compiled records, extending back thousands of years, of the status and trends of seven major guilds of carnivores, herbivores, and architectural species from 14 regions. Large animals declined before small animals and architectural species, and Atlantic reefs declined before reefs in the Red Sea and Australia, but the trajectories of decline were markedly similar worldwide. All reefs were substantially degraded long before outbreaks of coral disease and bleaching. Regardless of these new threats, reefs will not survive without immediate protection from human exploitation over large spatial scales.

Gardener, Toby A., Isabelle M Cote, Jennifer A. Gill, Alastair Grant, Andrew R. Watkinson. Long-Term Region-Wide Declines in Caribbean Corals. 2003. Science 301 (5635), p958, 3p, 3 graphs, 1 map.

Abstract:

We report a massive region-wide decline of corals across the entire Caribbean basin, with the average hard coral cover on reefs being reduced by 80%, from about 50% to 10% cover, in three decades. Our meta-analysis shows that patterns of change in coral cover are variable across time periods but largely consistent across subregions, suggesting that local causes have operated with some degree of synchrony on a region-wide scale. Although the rate of coral loss has slowed in the past decade compared to the 1980s, significant declines are persisting. The ability of Caribbean coral reefs to cope with future local and global environmental change may be irretrievably compromised.

Comments:

In this issue of Science, there appeared numerous articles on the decline of coral reefs throughout the world. For those of us working in the field, those who keep abreast of such developments, and those who have spent some time on coral reefs, this is really nothing all that new. However, the data shown here, the scope of the articles and research involved, and the huge author list make quite a statement. More than anything, it shows the nearly unanimous feeling of researchers that our coral reefs have been declining, are continuing to decline rapidly, and are in desperate need of conservation. Let's think about this carefully on our next visit to the fish store. I urge everyone to consider their collections carefully and make sure that whether they cost a few dollars or a few hundred that each one is provided with care that ensures it survival. Moreover, efforts by aquarists to contribute to conservation based programs and efforts are urgently needed. It's our responsibility to care for each species exploited by us for the hobby.

Invertebrate Tidbits

Ronald L. Shimek, Ph. D.

This month, I will discuss an interesting article on peppermint shrimp...

Baldwin, A. P. and R. T. Bauer, 2003. Growth, survivorship, life-span, and sex change in the hermaphroditic shrimp Lysmata wurdemanni (Decapoda: Caridea: Hippolytidae). Marine Biology (2003) 143: 157-166.

Abstract:

Lysmata wurdemanni (Gibbes) is a protandric simultaneous hermaphrodite. All individuals first mature as a male-phase individual (MP) and then later change to a female-phase individual (FP) that spawns and broods embryos but can also mate as a male. A Gulf of Mexico population was sampled monthly for 1 year and bimonthly the next. Estimates of basic population parameters were obtained from cohort analysis to reveal possible factors explaining the unusual sexual biology of L. wurdemanni as well as the broad variation in the size (age) of change from MP to FP. Growth rates of individuals from cohorts varied from 4-7 mm carapace length per year. Growth of small MPs in the laboratory was somewhat faster but concordant with growth rates estimated from field samples. The period from recruitment to >50% sex change in cohorts varied from 3 months to 1 year. In the laboratory, the size and interval to sex change was similar to that of the most rapidly changing cohort observed. Survivorship of cohorts was high until later in life; life-span was estimated to be 12-18 months. Rates of sex change were highest from late winter through spring, in time for the spring-summer breeding season. The size and age of sex change in cohorts were related to the season of recruitment. MPs recruited from late winter to mid-spring rapidly changed to FPs at a relatively small size. A majority of MPs recruited in the summer and autumn did not change to FPs until the following late winter to spring, and they did so at a larger size. Rates of sex change were not correlated with the sexual composition of the population. We conclude that seasonal factors related to female breeding greatly influence sex change in L. wurdemanni. We found no evidence to support demographically influenced and socially mediated environmental sex determination, which has been suggested for L. wurdemanni and other sex-changing caridean shrimps.

Comments:

This article discusses everything you wanted to know about the growth and sexual habits of the peppermint shrimp, but were afraid to ask. Some of the interesting points are that the maximum life expectancy in the studied Gulf of Mexico population was only about a year and a half, and that the carapace (the "shell" over the body of the shrimp) increases in length about 4 to 7 mm per year. These shrimp enter the population by metamorphosing from a planktonic larva. Immediately after recruitment they are males. Later, after a period that varied from three months to about a year, they change into a hermaphroditic animal.