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We studied the diel variation of in situ coral temperature, irradiance and photosynthetic performance of hemispherical colonies of Porites lobata and branching colonies of Porites cylindrica during different bulk water temperature and tidal scenarios on the shallow reef flat of Heron Island, Great Barrier Reef, Australia. Our study presents in situ evidence that coral tissue surface temperatures can exceed that of the surrounding water under environmental conditions typically occurring during low tide in shallow reef or lagoon environments. Such heating may be a regular occurrence on shallow reef flats, triggered by the combined effects of high irradiance and low water flow characteristic of low Spring tides. At these times, solar heating of corals coincides with times of maximum water temperature and high irradiance, where the slow flow and consequent thick boundary layers impede heat exchange between corals and the surrounding water. Despite similar light-absorbing properties, the heating effect was more pronounced for the hemispherical P. lobata than for the branching P. cylindrica. This is consistent with previous laboratory experiments showing the evidence of interspecific variation in coral thermal environment and may result from morphologically influenced variation in convective heat transfer and/or thermal properties of the skeleton. Maximum coral surface warming did not coincide with maximum irradiance, but with maximum water temperature, well into the low-tide period with extremely low water flow in the partially drained reef flat, just prior to flushing by the rising tide. The timing of low tide thus influences the thermal exposure and photophysiological performance of corals, and the timing of tidally driven coral surface warming could potentially have different physiological impacts in the morning or in the afternoon. [ABSTRACT FROM AUTHOR]

To help assess the biological impact of warm-core eddies off eastern Australia, lanternfish (family Myctophidae) were sampled during cruises in August, September and October, 1979 and February and May 1980 as part of a 14 mo time-series study of Eddy J. During the study, Eddy J drifted some 500 km southward along the east coast of Australia and coalesced with another eddy, Eddy I. Myctophids were collected at night by midwater trawling ( n=150) in the upper 500 m of the water column. In all, 46 species of myctophids (6 913 specimens) were caught. Percentage similarity indices and cluster analyses of species assemblages showed that: (1) temporally, the myctophid fauna changed markedly both inside and outside the eddy between October and February, but, within a season, the myctophid fauna inside Eddy J changed little between consecutive cruises; (2) spatially, myctophid communities generally corresponded more closely with sample location with respect to the eddy than with depth and temperature per se. The 4 most common species ( Diaphus meadi, Hygophum hygomii, Lampanyctus alatus and Benthosema suborbitale), on the other hand, had ubiquitous distributions with respect to eddy location but had peaks of abundance at particular temperatures (15°, 17°, 19° and 21°C, respectively). The 5th most common species, Diaphus danae, was limited to outside or edge samples. The results suggest that the biological contrasts between a warm-core eddy and surrounding water masses are largely a function of the degree of the eddies' physical isolation after separation from the East Australian Current and that natural seasonal variations in myctophid communities may overshadow more subtle successional changes inside an eddy as the eddy ages. [ABSTRACT FROM AUTHOR]

Presents a study on the genetic structure of outbreak populations of the crown-of-thorns starfish on the Great Barrier Reef in Australia, by a comparison of two sets of outbreak populations occurring ten years apart. Methods and materials used in the study; Discussion on the results of the study.