Reef Science: Development Highlights
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.
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.
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.
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.
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.
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.
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.
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.