J. H. Carleton

Quantitative video sampling of coral reef benthos: large-scale application

The feasibility of reliably estimating percent cover of coral reef benthos by video techniques is examined. Video belt transects were recorded within study areas on Davies and John Brewer Reefs in the central Great Barrier Reef during September 1988. Two years later in September 1990, the study area at Davies Reef was resampled concurrently by video and line intercept transects. Percent cover data of major coral growth forms and non-biotic physionomic attributes were extracted from video footage by scoring the identity of items located at even or random spaced points along the transect. A cost-benefit analysis which compared increases in precision with increases in sampling effort suggested that the optimum regime for analyzing 200 m long video transects was five subsamples of 110 random points or one sample of 550. This regime resolved both spatial variability at large and smaller spatial scales (between study areas and among transects) and temporal change (within a single study area over a two year period) for total live coral and individual growth forms. The strengths of the technique lie in its cost-savings in filed expenses, and in the production of a permanent visual record. The limitations of the technique lie in reduced taxonomic resolution when compared with “hands on” field techniques. The results suggest that for broad taxonomic categories of coral reef benthos reliable estimates of relative abundance can be obtained by video techniques.

Directional Swimming of Fish Larvae Determines Connectivity of Fish Populations on the Great Barrier Reef

Evidence of contamination in PCR laboratory disposables. Naturwissenschaften 82, 423–431 (1995) 18. Taberlet P, Griffin S, Goossens B, Questiau S, Manceau V, Escaravage N, Waits LP, Bouvet J: Reliable genotyping of samples with very low DNA quatities using PCR. Nucl Acids Res24, 3189– 3194 (1996) 19. Zierdt H, Hummel S, Herrmann B: Amplification of human short tandem repeats from medieval teeth and bone samples. Hum Biol 68: 185–199 (1996)

Rapid changes in shelf waters and pelagic communities on the southern Northwest Shelf, Australia, following a tropical cyclone

Abstract A pronounced shift in water column characteristics and in the composition of plankton communities was observed following the passage of Tropical Cyclone Tiffany along the margin of the southern Northwest Shelf, Australia in January 1998. Satellite-derived images of sea surface temperature, meteorological and hydrographic data indicate a southward movement of shelf waters into the study area near North West Cape (21°46′S). Changes in water mass temperature and salinity characteristics also occurred as a result of local heating and evaporation. Local in situ growth was likely to have caused increases in micro-phytoplankton abundance, biomass and primary production on the shelf. A diverse, copepod-dominated shelf mesozooplankton community changed to a less diverse assemblage dominated by copepods usually found in shallow nearshore habitats. Post-cyclone larval fish catches included families absent or rare in pre-cyclone samples. In the case of copepods and larval fish, southward transport of water masses along the shelf was most likely to have caused the observed changes. Long-shore water transport forced by cyclonic winds may be a recurrent, but episodic mechanism of planktonic dispersal on the North West Shelf.

Temporal patterns in distributions of tropical fish larvae on the North-west Shelf of Australia

Information on the temporal distributions of tropical fish larvae is scarce. Early stage larval fishes were sampled using towed bongo plankton nets at sites on the southern North West Shelf of Australia (21°49′S, 114°14′E), between October and February of 1997/98 and 1998/99. The first summer was characterised by El Nino–Southern Oscillation-driven upwelling and high primary productivity, whereas in the second summer water temperatures were warmer and primary production was lower. Benthic percoid shorefishes dominated surface assemblages in both summers and this pattern may be typical of tropical shelf environments.The abundance and diversity of larval fishes were lowest in October and increased from November through to February. Assemblages displayed weak cross-shelf patterns, with a few taxa being more abundant at inshore sites (e.g. monacanthids), whereas others were more abundant offshore (e.g. scombrids). Although the composition of assemblages remained relatively consistent, many taxa (e.g. pomacentrids and carangids) showed differences in abundance between summers. Multivariate analyses found no relationships between abundance patterns of larval fishes and biophysical variables, such as temperature, salinity, and zooplankton biomass. Thus, seasonal changes in abundance may reflect differences in the spawning activities of adult fishes and/or larval survival.

Tropical zooplankton in the highly-enclosed lagoon of Taiaro Atoll (Tuamotu Archipelago, French Polynesia)

Abstract Nocturnal zooplankton assemblages around Taiaro Atoll were sampled over six nights during February 1994. Replicate zooplankton samples were collected at windward and leeward locations in the enclosed lagoon and adjacent ocean with a metered net (85 cm diameter, 500 μm mesh) towed for 15 min at 5 m depth. The zooplankton community in the lagoon was very different from that in the ocean. Oceanic samples contained 50 mostly holoplanktonic taxa (diversity index, H′=2.62; evenness index, J′=0.67). Lagoonal samples contained 19 mostly meroplanktonic taxa (H′=1.54, J′=0.52) with three taxa (decapod larvae; an ostracod, Cypridina sp.; a copepod, Acartia fossae) contributing >90% of the individuals. Unlike the ocean, zooplankton distributions in the lagoon were not homogenous; instead spatial patterns were apparently formed by the interaction between hydrodynamic processes and species-specific behaviour.

Determinants of pelagic metabolism in the Timor Sea during the inter-monsoon period

The Timor Sea is a major conduit of the Indonesian Throughflow characterised by large internal waves and tides. To ascertain whether these result in high pelagic productivity, we conducted experiments to determine the metabolic balance between net community production (NCP) and community respiration (CR) on the Sahul Shelf, the Sahul Shoals and the Yampi Shelf, an area of active hydrocarbon seeps. The barrier to vertical mixing of subthermocline nutrients represented by the halocline allowed new production to dominate in March 2004, whereas production in June 2005 depended on recycled nutrients. CR was correlated with dissolved organic carbon (DOC) in 2004, but with chlorophyll in 2005, suggesting that respiration was dominated by microheterotrophs in 2004 but by autotrophs in 2005. Overall, area-specific CR averaged 120 ± 92 (s.d.), 101 ± 52 and 61 ± 6 mmol O2 m–2 day–1, NCP averaged 109 ± 85 (s.d.), 32 ± 41 and 57 ± 10 mmol O2 m–2 day–1, and average gross primary production (= CR+NCP) : R ratios were 1.9, 1.4 and 1.9 on the shelf, at the Sahul Shoals and the Yampi Shelf, respectively. We suggest that differences in water column structure and internal wave activity drive intermittent high production events in a predominantly oligotrophic sea.