Marc Nogueras

The new seafloor observatory (OBSEA) for remote and long-term coastal ecosystem monitoring

A suitable sampling technology to identify species and to estimate population dynamics based on individual counts at different temporal levels in relation to habitat variations is increasingly important for fishery management and biodiversity studies. In the past two decades, as interest in exploring the oceans for valuable resources and in protecting these resources from overexploitation have grown, the number of cabled (permanent) submarine multiparametric platforms with video stations has increased. Prior to the development of seafloor observatories, the majority of autonomous stations were battery powered and stored data locally. The recently installed low-cost, multiparametric, expandable, cabled coastal Seafloor Observatory (OBSEA), located 4 km off of Vilanova i la Gertrú, Barcelona, at a depth of 20 m, is directly connected to a ground station by a telecommunication cable; thus, it is not affected by the limitations associated with previous observation technologies. OBSEA is part of the European Multidisciplinary Seafloor Observatory (EMSO) infrastructure, and its activities are included among the Network of Excellence of the European Seas Observatory NETwork (ESONET). OBSEA enables remote, long-term, and continuous surveys of the local ecosystem by acquiring synchronous multiparametric habitat data and bio-data with the following sensors: Conductivity-Temperature-Depth (CTD) sensors for salinity, temperature, and pressure; Acoustic Doppler Current Profilers (ADCP) for current speed and direction, including a turbidity meter and a fluorometer (for the determination of chlorophyll concentration); a hydrophone; a seismometer; and finally, a video camera for automated image analysis in relation to species classification and tracking. Images can be monitored in real time, and all data can be stored for future studies. In this article, the various components of OBSEA are described, including its hardware (the sensors and the network of marine and land nodes), software (data acquisition, transmission, processing, and storage), and multiparametric measurement (habitat and bio-data time series) capabilities. A one-month multiparametric survey of habitat parameters was conducted during 2009 and 2010 to demonstrate these functions. An automated video image analysis protocol was also developed for fish counting in the water column, a method that can be used with cabled coastal observatories working with still images. Finally, bio-data time series were coupled with data from other oceanographic sensors to demonstrate the utility of OBSEA in studies of ecosystem dynamics.

Control and acquisition system design for an Expandable Seafloor Observatory (OBSEA)

Design of the control unit for the OBSEA seafloor observatory based on a 32 bit microcontroller with SNMP (Simple Network Management Protocol) communication.

OBSEA an oceanographic seafloor observatory

In this paper is described the different items of a subsea observatory. The control system is constantly monitoring the internal and external components of the observatory detecting operating faults and acting automatically in consequence‥ It will be presented an overview of the information treatment servers structure used in the OBSEA project explaining the chosen topology

Study on Heat Dissipation and Cooling Optimization of the Junction Box of OBSEA Seafloor Observatory

Multidisciplinary underwater observatories represent an exceptional technological resource that can signify a qualitative forward step in marine scientific research as well as operational oceanography and climate change study. A cabled underwater observatory system that can provide broad bandwidth communication and power to oceanographic instruments is developed. The observatory consists of a subsea junction box that is fixed at a cable terminal, enabling real-time communication, power conversion, and power distribution of up to eight oceanographic instruments and one connection for a junction box. Therefore, the observatory has the capacity to cover a large range of distance-time observations, and to provide new opportunities for research and technological innovation. However, there are some issues to consider when designing the electronic system for the underwater observatory. The main concern is the location of the equipment in a hostile environment with difficult access for inspection and repair. Hence, appropriate heat management of the electronic apparatus has a significant influence on the useful life of this equipment. Specific validation and study of the behavior of the system prior the deployment, and permanent equipment status monitoring is essential to assure fault-free operation over the longest possible period of time. In this study, we present the thermal studies carried out on the junction box of the Observatorio Submarino Expandible Cableado (OBSEA) (expandable underwater cabled observatory) and the monitoring procedures are established. The underwater observatory has been deployed off the coast of the Balearic Sea and has been operating in real conditions for more than three years without interruption. The results show that this underwater observatory system is adequate for subsea real-time and long-term observations.

Geophone calibration by means of hyperbaric chamber

This work proposes the use of a hyperbaric chamber in order to verify and validate the calibration in a marine geophone sensor before and after the pressure underwater laboratory test. The focused objective is the behavior respect to frequency of coupling between the geophone and the sediment to characterize its transfer function. The calibration of the 3 axes of the geophone up on the sediment box are made with a shaker table. We can observe the variations of coupling sensibility of the sensors of the geophone work through the sediment after the test inside the hyperbaric chamber at 20 atmospheres of water pressure.

Evaluation of AUV-borne ADCP measurements in different navigation modes

Most Autonomous Underwater Vehicles (AUVs) mount an Acoustic Doppler Current Profilers (ADCP). Data from this sensor are rarely used in scientific studies due to the complexity of its processing and the lack of validation. Aside of that, AUV operators lack a set of guidelines regarding the optimal navigation modes and AUV-borne ADCP configurations to obtain the most accurate data possible. This study compares 12.6 hours of AUV-borne ADCP currents measurements, taken in different AUV navigation modes and ADCP configurations, to those of a moored AWAC. Results show RMS errors of 5 cm/s for U (East) and V (North) measures and of 2 cm/s for vertical currents measures for most of the navigation modes. Cell size is found to be the most influential parameter in data accuracy and yo-yo type of surveys are proved to be as accurate as constant depth ones.