Jean Luc Devenon

Impact of cross-reef water fluxes on lagoon dynamics: a simple parameterization for coral lagoon circulation model, with application to the Ouano Lagoon, New Caledonia

This manuscript presents a combined experimental and numerical study of the impact of cross-reef fluxes on coral reef lagoon dynamics. The selected field site is the Ouano Lagoon (New Caledonia Island, France) in the South Western Pacific Ocean. Measurements of wave transformation above the reef and current profiles through passages and reef openings have been carried out during a 3-month survey. Data analysis reveals the preponderant roles played by both tides and waves on the lagoon dynamics. Based on field data, a simple parameterization of cross-reef fluxes is implemented in a coastal lagoon circulation model and a satisfactory agreement is found between parameterized model and field results. The model is thus used as a numerical experimental tool in order to analyse the cross-reef flows’ possible influence on a narrow lagoon dynamics. The results highlight the importance of cross-reef fluxes induced by wave breaking over the reef barrier on the whole lagoon circulation and water properties.

How could thermal stratification affect horizontal distribution of depth-integrated metazooplankton communities in the Gulf of Gabes (Tunisia)?

ABSTRACT The spatial and temporal variability of metazooplankton communities in relation to environmental and trophic factors were studied in the Gulf of Gabes during three periods of increasing thermal stratification in June, July and September. Non-metric multi-dimensional scaling (NMDS) revealed the time and space succession of three zooplankton communities in relation to the degree of thermal stratification. A co-inertia analysis showed the association between these communities and the trophic conditions (abundance and composition of microplankton) driven by stratification. Three divergent communities were evident. The first, characterized by annelid larvae and coastal copepods, was associated with shallow mixed and microplankton-rich water (June, coastal). The second, characterized by euphausiids, amphipods, doliolids and several deep-water copepods, corresponded to highly stratified microplankton-poor water (September). The third, characterized by the most ubiquitous and abundant species, was linked to intermediate water (June deep and July). Temperature and salinity conditions also explained the distribution of key species. Clausocalanus furcatus, Oithona plumifera and Triconia conifera were clearly associated with warm and highly stratified water (September). Enhanced thermal stratification led to higher surface salinity, explaining the emergence of euryhaline taxa such as Oithona plumifera.

Water Masses Exchanges Within Boughrara Lagoon-Gulf of Gabes System (Southeastern Tunisia)

Coastal lagoons are saline water bodies partially isolated from ocean or seas by one or more barrier islands, and linked to the sea by one or more relatively small channels. Lagoons naturally grade into other types of wetland habitat including semi enclosed marine bays, freshwater lakes and estuaries (Barnes in Coastal lagoons. Cambridge University Press, Cambridge, p. 106, 1980).