reefs and rain forests

Robert van Woesik b984138 at
Mon May 29 20:31:01 EDT 2000

RE: Coral reefs and Rain forests

A similarity in diversity maybe the only thing that coral reefs and rain
forests have in common; let us not forget Steele's classic paper in 1985
(Steele, J.H. (1985) A comparison of terrestrial and marine systems.
Nature 313, 355-358).

Plant communities appear limited by dispersal in both temperate
(Tilman's many references) and tropical regions (Hubbell S.P., Foster,
R.B., O’Brien, S.T., Harms, K.E., Condit, R., Wechsler, B., Wright, S.J.
and Loo de Lao, S. (1999) Light-gap disturbances, recruitment
limitation, and tree diversity in a neotropical forest. Science 283,
554-557), where seed shortages keep diversity high and gaps may be
occupied at random. Hubbell et al. (1999, p. 557) state “...sites [in a
tropical moist forest] are won by ‘default’ by species that are not the
absolutely best competitor for the site”. However, in the tropical
marine environment ‘seed’ dispersal does not appear to be a problem, as
broadcast spawning ensures widespread dispersal of coral larvae. Many
coral communities show no sign of recruitment limitation (except maybe
very isolated reefs). Steele (1985) suggested a combination of an
immense annual larval production in the oceans with extensive larval
dispersal might be a reflection of the dampened short-term environmental
variability of that environment. On the other hand, organisms in the
terrestrial system must cope with more short-term variability and hence
display more restricted dispersal mechanisms than oceanic organisms. A
means to the same end (i.e., high diversity) differs between tropical
terrestrial and tropical marine systems, the former most likely being
dispersal assembled and the latter by some other mechanism(s).  Yet, it
is hardly surprising that the mechanisms causing high diversity on the
land may differ from those in the sea. The environmental variability,
for example temperature, in terrestrial systems is large in both the
short and long-term, but the oceans have a smaller amplitude of
variability in the short term (Steele 1985); variations to this
variability will be more detrimetal to organisms in the marine
environment than to terrestrial organisms (e.g., the 1998 high SST and
consequent coral bleaching), because marine organisms are adapted to
small physico-chemical variability. Caution is necessary if we continue
to compare the two systems (i.e., coral reefs and rain forests) as
similar systems when in fact the processes that shape the systems are
completely different.

Rob van Woesik

Dr. Robert van Woesik
Associate Professor
Department of Marine Sciences
University of the Ryukyus
Nishihara, Okinawa 903-0123

E-mail: b98413 at

Ph: (81) 098 895 8564
Fax: (81) 098 895 8552

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