The Giant Triton (Charonia tritonis) and other members of the genus Charonia have been collected by humans for most of recorded history, but it is difficult to determine the extent to which the population densities of these species have been altered by human activities. Tritons are confirmed predators of many species of starfish and Endean (1969) discussed the possible causes of crown-of-thorns starfish outbreaks with particular emphasis on the removal of the predators of adult and juvenile starfish by humans. The triton has the potential to play a significant ecological role in low-density population dynamics by direct predation on juvenile and adult starfish and by limiting the aggregation of starfish prior to spawning and thereby limiting egg fertilisation and the subsequent outbreak potential of the starfish population.
Population density, size-frequency and reproductive data on an
assemblage of shallow water, coral-reef starfish (Asteroidea)
were gathered over five years at Heron Reef. Heron Reef, which is
located near the southern end of the Great Barrier Reef, has not
been known to carry an outbreak of the crown-of-thorns starfish
(Acanthaster planci) and its coral cover is well developed. While
there has been detailed study of the starfish assemblages on some
reefs that have recently undergone Acanthaster planci population
outbreaks (Yamaguchi, 1975 b; 1977 a), the composition of these
assemblages may well be different from pre-outbreak assemblages.
The results presented in this study are in accord with the
hypothesis of Endean and Cameron (1990 a) that complex, high
diversity assemblages of coral-reef animals are characterised by
a predominance of rare, long-lived species with relatively
constant population sizes and size structures and a minority of
relatively common, short-lived opportunistic species
characterised by fluctuating population sizes and size
structures.
Many scientists are convinced that Ice Ages would result from marked declines in atmospheric concentration of Carbon Dioxide (CO2). Because the level of CO2 in oceanic surface waters is in approximate equilibrium with its concentration in the atmosphere and the solubility of CO2 in water is highest at times of lowest atmospheric concentration, the oceans are an enormous reservoir of CO2. At present, the Earth's atmosphere only contains small amounts of CO2. Calcium Carbonate deposition / dissolution is heavily pH dependent and provides an additional sink of bicarbonate in oceanic surface waters which are alkaline, and a potential source in pure fresh water which is acidic. Calcium Carbonate dissolution at the lysocline effectively buffers oceanic waters. Calcium Carbonate deposits, while common in shallow water, do not occur below this depth. Given the large area covered by coral reefs, and a carbonate deposition rate of many kilograms per square metre per year, these structures deposit megatonnes of Calcium Carbonate annually. Forty-four percent of this mass is effectively Carbon Dioxide.
By the 14th of August in the year 2126, the Earth will be presented with a dilemma ..... The passage of comets has heralded many changes on Earth ..... Haley's may have generated interest, but there would certainly be no mistaking the passage of an early Swift-Tuttle about 590 million years ago ..... A great harmonic time series is evidenced in the fossil record ..... Starting at the Cambrian boundary, there are sixteen cycles of about 22.1 million years until the Permian extinction. Then a further 8 cycles until the Tertiary-Cretaceous boundary, followed by another 3 up to the Pleistocene ..... The major extinctions and adaptive radiations seem to represent tips of cosmological icebergs in more ways than one .....
url of this page -- Revised: 22nd September 1996. Copyright ©
1996 Charonia Research