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Ecological characteristics of coral patch reefs at Midway Atoll, Northwestern Hawaiian Islands
Ecological aspects of coral patch reefs were studied from 1981 to 1985 in Welles Harbor, Midway Atoll. Water temperatures varied from 17??C in February to 28??C in August. Sizes of reefs studied were described by mean area (59 m2), mean volume (52 m3), vertical relief (<1 m), and inter-reef isolation (100 m). Considerable temporal change in reef size occurred due to large winter swells shifting bottom sand. Six common species accounted for 70% of all individual fish visually censused over 4 years. Overall fish assemblage composition ranged from 11 to 46 fish/10 m2, from 3 to 14 species. Numerical abundance and species richness for all fish (pooled) strongly correlated with physical reef substrate characteristics of area, volume, and vertical relief during summer. Species diversity (H') was not correlated with the substrate variables, suggesting similarity in the structure of fish communities among different sizes of patch reefs. Daily surveillance for presence of large transient taxa suggested that visits by sharks, large jacks, monk seals, sea turtles, and dolphins were infrequent. Density estimates were made for all conspicuous invertebrate megafauna during initial and final assessments. Six common taxa provided 90% of these counts; nearly half were sea urchins. Percent cover also was recorded for coral and algal species on the patch reefs. Cover by live coral was low (about 7%) and dominated by a few species. Mean algal cover ranged from 32 to 77%. Such information on ecological characteristics of reefs may aid in understanding complex ecological processes and provides an earlier reference for current ecosystem studies.
Diet composition and terrestrial prey selection of the Laysan teal on Laysan Island
The Laysan teal (Anas laysanensis) is an endangered dabbling duck endemic to the Hawaiian Archipelago but currently restricted to a single breeding population on Laysan Island. We studied its diet using fecal analysis and behavioral observations. Laysan teal fecal samples (N=118) contained prey items in 15 primary prey categories with a mean of 2.9 (range 0-7) taxa per sample. Sixty-two of these fecal samples were quantified with 2,270 prey items identified (mean items per sample 37; range 0-205). Based on fecal analysis and behavioral observations, we learned that the Laysan teal is not strictly a macroinsectivore as previously reported, but consumed seeds, succulent leaves, and algae, in addition to adult and larval diptera, ants, lepidoptera, coleoptera, and Artemia. We compared abundance of invertebrates from two terrestrial foraging substrates, soil and standing vegetation, to the abundance of invertebrate prey items counted in fecal samples collected from these habitats for the same period. In the soil substrate, Laysan teal selected two of the most abundant invertebrates, lepidoptera larvae and coleoptera. In the standing vegetation, Laysan teal selected the most abundant taxa: coleoptera. Amphipods were consumed in proportion to their abundance, and small gastropods (Tornatellides sp.), isopods, and arachnids were avoided or were identified in fecal matter in disproportion to their abundance in the foraging habitat. We compared fecal composition of samples collected in aquatic and terrestrial habitats and detected significant differences in samples' species compositions. The conservation implications of the adult Laysan teal's diet are positive, since results indicate that the Laysan teal are opportunistic insectivores, and exhibit dietary flexibility that includes seeds and other food. Dietary flexibility improves the possibility of successfully reestablishing populations on other predator-free islands.
South China Sea
The South China Sea is poorly understood in terms of its marine biota, ecology and the human impacts upon it. What is known is most often contained in reports and workshop and conference documents that are not available to the wider scientific community. The South China Sea has an area of some 3.3 million km 2 and depths range from the shallowest coastal fringe to 5377 m in the Manila Trench. It is also studded with numerous islets, atolls and reefs many of which are just awash at low tide. It is largely confined within the Tropic of Cancer and, therefore, experiences a monsoonal climate being influenced by the Southwest Monsoon in summer and the Northeast Monsoon in winter. The South China Sea is a marginal sea and, therefore, largely surrounded by land. Countries that have a major influence on and claims to the sea include China, Malaysia, the Philippines and Vietnam, although Thailand, Indonesia and Taiwan have some too. The coastal fringes of the South China Sea are home to about 270 million people that have had some of the fastest developing and most vibrant economies on the globe. Consequently, anthropogenic impacts, such as over-exploitation of resources and pollution, are anticipated to be huge although, in reality, relatively little is known about them. The Indo-West Pacific biogeographic province, at the centre of which the South China Sea lies, is probably the world's most diverse shallow-water marine area. Of the three major nearshore habitat types, i.e., coral reefs, mangroves and seagrasses, 45 mangrove species out of a global of 51, most of the currently recognised 70 coral genera and 20 of 50 known seagrass species have been recorded from the South China Sea. The island groups of the South China Sea are all disputed and sovereignty is claimed over them by a number of countries. Conflicts have in recent decades arisen over them because of perceived national rights. It is perhaps because of this that so little research has been undertaken on the South China Sea. What data are available, however, and if Hong Kong is used , as it is herein, as an indicator of what the perturbations of other regional cities upon the South China Sea are like, then it is impacted grossly and an ecological disaster has probably already, but unknowingly, happened.