The south-west lagoon of New Caledonia is a wide semi-open coral reef lagoon bounded by an intertidal barrier reef and bisected by numerous deep inlets. This paper synthesizes findings from the 2000-2008 French National Program EC2CO-PNEC relative to the circulation and the transport of suspended particles in this lagoon. Numerical model development (hydrodynamic, fine suspended sediment transport, wind-wave, small-scale atmospheric circulation) allowed the determination of circulation patterns in the lagoon and the charting of residence time, the later of which has been recently used in a series of ecological studies. Topical studies based on field measurements permitted the parameterisation of wave set-up induced by the swell breaking on the reef barrier and the validation of a wind-wave model in a fetch-limited environment. The analysis of spatial and temporal variability of suspended matter concentration over short and long time-scales, the measurement of grain size distribution and the density of suspended matter (1.27 kg l(-1)), and the estimation of erodibility of heterogeneous (sand/mud, terrigenous/biogenic) soft bottoms was also conducted. Aggregates were shown to be more abundant near or around reefs and a possible biological influence on this aggregation is discussed. Optical measurements enabled the quantification of suspended matter either in situ (monochromatic measurements) or remotely (surface spectral measurements and satellite observations) and provided indirect calibration and validation of a suspended sediment transport model. The processes that warrant further investigation in order to improve our knowledge of circulation and suspended sediment transport in the New Caledonia lagoon as well as in other coral reef areas are discussed, as are the relevance and reliability of the numerical models for this endeavour.

The concentrations of nine elements (Ag, As, Cd, Co, Cr, Cu, Mn, Ni and Zn) were measured in the oyster Isognomon isognomon and the edible clam Gafrarium tumidum from different sites along the SW New Caledonian coast which is subjected to important chemical inputs due to intense land-based mining activities (New Caledonia is the third world producer of nickel). Results indicate that concentrations in the two organisms mirrored the geographical differences in contamination levels as established through element analyses in sediment. On the basis of organism analyses, two out of the seven investigated stations can be considered as relative "reference" sites, except for As, for which very high levels were detected in clam and oyster tissues (up to 441 microg g(-1) dry wt for clams). Overall, our results indicate that both tropical organisms investigated could be used as valuable bioindicator species for surveying metal contamination in the coastal waters of New Caledonia with reasonable perspectives of wider application to other coral reef environments.

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The periodicity of striae formation in the tropical scallop Comptopallium radula (Indo-West Pacific Ocean) was investigated with an in situ marking technique, using the calcein fluorochrome. To minimize scallop stress caused by excessive handling, in situ benthic chambers were used for marking experiments.Once marked, scallops (shell height range: 38.4-75.8 mm) remained on site in a large benthic enclosure and were collected at regular time intervals to count new striae formed after marking, over a period of 3 months. A 3-hour exposure period with calcein (150 mg L -1 ) was sufficiently long to create a detectable mark in nearly all shells. It was however impossible to count the striae in 48.2 % of the shells (mainly large specimens) because of a very small growth after marking. Lack of significant mortality during the experiments indicated that tested calcein concentrations were not lethal. A decrease in shell growth rate was observed after marking but the respective impacts of calcein toxicity and changes in environmental conditions could not be discriminated. Our results suggest that in situ calcein marking inside benthic chambers is suitable for shell growth studies of scallops, provided the latter are not too old. After marking, the juvenile C. radula formed an average of one stria every 2.1 days in summer. Reports of 2-day periodicity in biological rhythms are rare. Striae formation in C. radula may be controlled by an endogenous oscillator, synchronized by an environmental cue acting as a zeitgeber, such as seawater temperature or sea level pressure, both of which exhibit 2-day variations in the Pacific Ocean. As in many other scallop species, C. radula forms striae periodically under natural conditions, but this study shows that in pectinid juveniles, this periodicity can deviate from a daily cycle. These results suggest that C. radula shells have tremendous potential for recording environmental conditions during periods ranging from months to a few years and with a resolution of 2 days.The original publication is available at www.springerlink.com

Ten sediment trap arrays were deployed over two years for periods of 3 to 40 days in three different sampling points along a 50 m long Mediterranean submarine cave. Mean total particulate matter flux decreased strongly from the semi-dark area (3.3 g mW2 d-') to the dark area (0.8 and 0.6 g m-' d-I). Carbon represented 3.3% to 3.5% and nitrogen 0.34% to 0.38% of settling dry matter. The decrease in organic input from the entrance to the terminal part of the cave results in increasingly oligotrophic conditions with distance from the cave entrance. Horizontal resource limitation can be connected with a strong zonal decrease in fauna richness. Biomass declines both in hard substrate and soft bottom communities. Despite major differences, some similarities are noticed between oligotrophic conditions that may occur in the dark cave and those in around 1000 m depth ecosystems. Dark oligotrophic submarine caves can be considered to be good scale models for the study of some aspects of general trophic pathways,

Abstract. Submarine caves display a paucity of benthic density and biomass that may be related to low trophic resources. Analysis of organic carbon, organic nitrogen, carbohydrate, protein and lipid content of suspended particulate matter was made during the period July 1985-July 1987 in a Mediterranean cave (Marseille, France) in order to determine any differences in the particulate organic matter composition along an horizontal transect. Particulate organic matter content clearly declined from the entrance of the cave to the dark inner area. This impoverishment could not be explained by a simple decrease in a few organic compounds, but appeared to be related to the combination of a decrease in both the amount and the composition of the suspended particles. Three progressive levels of impoverishment were identified towards the dark inner area of the cave: (i) decreasing amounts of seston; (ii) decreasing organic content of particles; (iii) increasing proportions of the geopolymeric (i.e., humic) components in the remaining organic matter, indicating increased degradation. The cave appeared to be sharply divided into two distinct sections -a twilight outer section whose waters contained slightly lower amounts of particulate organic matter than the open sea, and a dark inner section, 8 to l 0 m higher, separated from the outer section by a steep rise and with waters of low organic matter content. The water in the twilight section appeared to be in thermal equilibrium with the open sea, and that in the dark inner section displayed thermal stratification. These differences indicated the presence of two distinct water bodies with contrasting average residence times, estimated as 1 d in the outer twilight section and 8 d in the dark inner section. The joint action of sedimentation and degradation resulted in an abrupt depletion of particulate organic matter in the dark inner section accompanied by a decrease in the benthic fauna. The decline in benthic heterotroph populations is probably related to the abrupt transition to oligotrophic conditions.

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