While literature is relatively abundant on adult shellfish, ecophysiological studies at the larval stage are scarce because of both technical difficulties and inadequate methodology. A tool dedicated to provide basic information for larval ecophysiology was accordingly developed. Two steps were followed: first a flow-through method of Crassostrea gigas larval culture was perfected during a set of experiments in which rearing systems and larval density were assessed. Then a continuous hydrobiological data recorder was adapted with modifications to comply with our experimental aim. SILO (Système d'Instrumentation des Larves en flux Ouvert) allowed the successive acquisition of hydrobiological parameters in ten 150 l larval tanks in which larvae were reared using flow-through techniques under controlled environmental conditions. An automated system enabled sequential measurement of hydrobiological parameters from one larval culture to the next. A chamber system contained several probes for measurement of temperature, salinity, pH and fluorescence. The electronic system allowed real time acquisition, storage and transfer of data. SILO was successful as a larval rearing device, reducing larval disturbance that could result from transfer and handling for measurement. It was also efficient as a tool to provide basic information for larval ecophysiology research. The effect of temperature (17, 22, 25, 27, 32°C) on growth and ingestion of microalgae was studied to test SILO. Maximum growth occurred at 27 °C (16 ± 2 µm d-1) and 32 °C (15 ± 3 µm d-1) whereas larvae reared at 22 and 25°C showed lower development (8.6 ± 3.1 and 11.7 ± 2.5 µm d-1, respectively). Moreover, metamorphosis exhibited no significant difference at 27 or 32 °C with 87.5 ± 7.1 and 85.9 ± 9.6% respectively, while at 22 or 25 °C lower metamorphosis was recorded with 55.2 ± 8.3 and 57.6 ± 9.6%, respectively. The lowest temperature (17 °C) strongly inhibited ingestion whereas the highest temperature (32 °C) stimulated maximum feeding activity over the whole larval rearing period.

The MAREL Iroise data buoy provides physico-chemical measurements acquired in surface marine water in continuous and autonomous mode. The water is pumped 1.5 m from below the surface through a sampling pipe and flows through the measuring cell located in the floating structure. Technological innovations implemented inside the measuring cell atop the buoy allow a continuous cleaning of the sensor, while injection of chloride ions into the circuit prevents biological fouling. Specific sensors for temperature, salinity, oxygen and fluorescence investigated in this paper have been evaluated to guarantee measurement precision over a 3 month period. A bi-directional link under Internet TCP-IP protocols is used for data, alarms and remote-control transmissions with the land-based data centre. Herein, we present a 29 month record for 4 parameters measured using a MAREL buoy moored in a coastal environment (Iroise Sea, Brest, France). The accuracy of the data provided by the buoy is assessed by comparison with measurements of sea water weekly sampled at the same site as part of SOMLIT (Service d'Observation du Milieu LIToral), the French network for monitoring of the coastal environment. Some particular events (impact of intensive fresh water discharges, dynamics of a fast phytoplankton bloom) are also presented, demonstrating the worth of monitoring a highly variable environment with a high frequency continuous reliable system.

Abstract. The Gironde Estuary, one of the largest European ones, presents temporary low dissolved oxygen content in its fluvial section close to the Bordeaux urban area. In a context of population growth and of long-term environmental changes, the development of a high-frequency monitoring programme of the fluvial-estuarine system of the Gironde, called MAGEST (MArel Gironde ESTuary), had appeared essential to address current and future water-quality issues/evaluations. The objectives of the MAGEST survey program are to establish a reference database to improve the knowledge of the Gironde Estuary functioning, encompassing the aspects of hydrology, sediment dynamics and biogeochemistry. Through examples of results from intratidal to seasonal time scales, we demonstrate how such a long-term, high-frequency monitoring of a fluvio-estuarine system is of valuable interest to extract the main trends of its functioning and of the water quality in relation to external forcings (climatology, urban wastes, land use, . . . ) and to predict the future evolution of an estuary with global and environmental changes.

This paper describes the mechanical behaviour of ropes used for deep sea oceanographic operations. First the requirements of deep sea handling ropes are presented. Two high performance fibres are commonly used, aramid co-polymer and high modulus polyethylene (HMPE), and these are then compared. Results from tests on single fibres and 50 ton break load braided ropes are presented, which show that the initial stiffness of a new HMPE rope increases with load level in a bedding-in process resulting from both molecular alignment and construction reorientation. The aramid rope is less sensitive to this effect and shows a high stiffness from first loading. Measurements made at sea on oceanographic ropes of both materials using an elastic recoil method are presented, and apparent modulus values are consistent with laboratory measurements. Once both ropes have been fully bedded-in the HMPE is significantly stiffer, particularly under dynamic loads. Creep tests indicate that aramids creep less quickly than HMPE under constant loads over a 6 h period at 20 °C. Bending over sheave tests indicate longer lifetimes for the aramid but further tests on wet aramid are required to complete this conclusion. Highlights► Original data on the mechanical behaviour of two types of deep sea handling rope. ► New results from measurements at sea. ► A discussion of the relative merits of aramid and HMPE fibre ropes for this application.

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