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REBENT : Benthic monitoring network (REseau de surveillance BENThique)

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REBENT : Benthic monitoring network (REseau de surveillance BENThique)

Brittany as a pilot-region : from the set up stage to the implementation stage

Growing demands for surveys on marine biodiversity

Since the end of the 90’s, the need to better understand and monitor marine biodiversity has been increasing noticeably. It is necessary to assess both the impact of pollutions and anthropogenic activities as well as the climate change. It is also a question of improving the management and protection of the natural environment. These needs range from the international and European levels (international conventions, European regulations, etc) to the national, regional and even local levels (environmental zones of ecologic interest, marine natural reserves, management plans, etc).

Benthic species (living on sea floors) act as permanent monitor species of the marine environment. They integrate local ecological features and are subject to natural fluctuations or fluctuations generated by human activities.

It is true to say that France has taken a long time to implement a dynamic policy corresponding to these growing needs. The Erika shipwreck, in December 1999, suddenly highlighted the lack of consistent reference data on the distribution of benthic fauna and flora along the continental shelf. All parties, scientists and institutions alike, have seized the opportunity to collect and format data relating to benthic habitats along the coasts of Brittany.

Strong regional dynamics

As a matter of fact, Brittany has many assets to offer:

- A well developed and varied marine environment, made up of sheltered bays or masses of rocks exposed to sea winds, numerous islands and islets, wide tidal flats (sandy and rocky), with numerous remarkable habitats, such as sea grass beds, maerl beds or alga fields.

- A zone shared between two biogeographic regions that, besides increasing biodiversity at the regional level, offers first-class opportunities to identify the effects of climate change.

- Numerous attacks on the environment : along the popular coasts of Brittany, the benthic fauna and flora are subject to many disturbances produced by human activities : either directly produced (effects of dragging fishing gear, aggregate extractions, shellfish farming, etc), or resulting from chronic pollutions (urban, industrial or agricultural waste disposal) or accidental inputs (oil spills, introduction of exogenous species).

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- Strong requests for management, initiated by the Diren (regional administrative body for the environment) and Région Bretagne (Brittany administrative body).

- Scientific and technical expertise within a multidisciplinary process, with the cooperation of various scientific bodies: IFREMER (French Research Institute of the Sea), IUEM (European Institute of Marine Studies), MNHN and the Marine research centres of Dinard and Concarneau, Roscoff biological centre, EPHE/CNRS laboratory of Dinard, CEVA in Pleubian.

REBENT, the benthic monitoring network (REseau de surveillance BENTique), was set up accordingly. The objectives were to collate relevant and coherent knowledge on the coastal benthic habitats, and to set up a “watchdog system” to detect the medium and long-term evolutions of these habitats, notably as regards biodiversity; Brittany is the pilot-region.

Besides the contribution of scientific partners, REBENT also gets financial support from DIREN, Région Bretagne and « Total Corporate Foundation for biodiversity and the sea », and special funds from the French “Comité Interministériel d’Aménagement du terrritoire”

(Interministerial Committee for regional development). IFREMER is in charge of the general coordination of the project.

During the course of 2001-2002, a preliminary project was drawn up and the following actions were undertaken: strategy and methods, operational schedule and distribution of work to the partners. Priority was given to recurrent needs in accordance with regulatory obligations. Operations started in 2003.

In order to optimize data collection and management, international and more notably European cooperation was sought. In concrete terms, this led to (i,) a network of experts in marine biodiversity and to an international working group on mapping seabed habitats, and (ii,) the European interreg MESH project (Mapping European Seabed Habitats). MESH aims to draw up guidebooks for seabed habitat mapping (choice of tools, methods of optimization and modelling) and also to produce harmonized cartographic charts.

About fifteen scientists work annually on the project, occasionally helped by R&D subcontractors: about fifty days are dedicated to surveys on oceanographic research vessels, airborne data collection, satellite imagery planning, numerous trips on board small boats, about a hundred dives and several weeks working on the tidal flat.

Historical data valuation

A bibliographical compilaton, based on different laboratory archives, has led to an inventory of maps, which, for the most part, are the results of prospecting surveys in the 60’s and 70’s.

At that time, a great effort was made to study the sea floor –sediments and biology- of the English Channel and the Bay of Biscay.

Collected data, systematically digitized and embedded in a Geographical Information System, cover most of the territorial French waters except very shallow sea floors and tidal zones.

Today, these documented original data are available on the REBENT website. As the maps compiled by the different authors are heterogenous in nature and the terms are complex, there data are rarely used, but recent work has been carried out to harmonize the different nomenclatures and to integrate the typology of the European seabed habitats. On this

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occasion, about twenty habitats –not listed at the European level until now- have enriched this typology. The maps will be available on the MESH project website.

Physical parameters, such as bathymetry, sedimentology, turbidity, swell exposure, etc, have also been updated and restructured.

New acquisitions

A regional inventory of remarkable habitats

In addition to historical data, a particular effort has been made to locate, at the regional level, the remarkable habitats on very shallow sea floors and in tidal zones (maerl beds, sea grass beds, etc), and to implement systematic updating procedures. The last prospection, carried out in 2005, compiled -in northern Brittany only- nearly seventy dwarf eelgrass beds, which had never been listed before. Concerning "kelp forests", it is difficult to draw up an exhaustive list but modelling is a way of determining their distribution.

Habitat mapping on reference zones

In order to get precise and updated references of the representative zones –including Natura 2000 sites- studies on seabed habitat mapping have been scheduled on about twenty zones located all around Brittany. These studies require new technology which provides accurate monitoring of the environment. These methodological developments take advantage of the MESH project involvement: a European intercalibration workshop on the techniques of habitat mapping, focussing on tidal zones and very shallow sea floors, was held in Brest in 2005.

In tidal zones, the Bay of Saint-Brieuc, Trégo-Goëlo, Abers, Glénan and Le Croisic were studied. The data acquired concerned coastal orthophotography, satellite imagery, topographic survey (Lidar) and observations made during field survey (measurements of the altimetric limits of alga belts, nature of sediments, inventory of fauna and flora, etc).

In submerged zones, Quiberon, Concarneau and Glénan (2003), Bay of Vilaine (2004), south of the Bay of Audierne and Abers (2005) as well as Trégor-Goëlo (2006) were studied onthe oceanographic vessel Thalia, using (i,) acoustic tools (multi-beam sounder, side-scan sonar) to conduct a monitoring survey on the sea floor morphology and sediments, (ii,) sampling tools (bucket, trawl pole) and (iii,) monitoring tools (underwater video, dives) to give biological features.

Acoustic surveys were conducted on very shallow sea floors (Concarneau, Glénan, Abers) on a small boat equipped with a multi-beam sounder and topographic recording (Lidar) in order to ensure the flow of information between the covered and uncovered sea floors.

Spatial dynamics of the vegetal cover

With SPOT satellite imagery and the regional expertise in remote sensing data processing, a systematic monitoring of the vegetal cover, in coastal zones uncovered by tides, has been implemented along most of the coasts of Brittany. Acquisitions scheduled at spring tides - together with in situ checks - are made, so as to get observations every 6 years from each selected point on the coastline. Systematic searches of archives images (available since 1986) have been carried out regularly and numerous documents have been found. The areas

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concerned are the coasts of Trégor, northern Finistère and Morbihan. Generally speaking, a substantial regression in the algal cover in Trégor and Morbihan has been witnessed.

The evolution of eelgrass beds (Zostera marina), growing at the bottom of tidal flats and on very shallow sea floors, is studied from aerial photographs. The main results obtained within a period of 10 years, from six different sites, and according to standard procedure, show a general trend to spreading on the upper continental shelf, although regressions may be observed in some sites.

Animal et vegetal diversity monitoring

More localized observations of marine biodiversity have been implemented on selected habitats, including remarkable habitats and well represented seabed habitats, which are likely to show the evolution of “normal environment” in terms of ecological quality. In tidal zones, they concern fine sediments, sea grasses and some types of rock masses. On very shallow sea floors, they concern fine sands, maerl beds and some types of bedrocks, observed while diving.

Samples are regularly taken according to procedures and, generally speaking, about ten sites located along the coasts are short-listed. The parameters measured concern specific richness and abundance, biomass, etc.

The numerous results obtained will be significant at medium and long-term. The first interpretations, based on the knowledge of species (groups and successions), already point to qualitative and quantitative indicators as regards the ecological state of fine sands.

Thanks to diving expeditions, it is now possible to fix the depth limits of kelp belts, in about thirty selected points along the coasts of Brittany. Compared with previous data, they indicate changes in the distribution of species and an upward trend of the lower limits, but there are fluctuations which require further assessment.

The regional participants have played a great part in the definition of the benthic monitoring strategy and in implementing the Water Directive (Directive Cadre Eau). They represent the English Channel-Atlantic Ocean shoreline in the European intercalibration working groups, set up to define the ecological indicators. Suggestions to adapt the monitoring network have been made, in order to meet the 2006-2007 Water Directive requirements.

Data management and data distribution

Because of the different types of data and the volume involved as well as the necessity to ensure, the long-term traceability of information, the data could not be possibly stored in Ifremer’s current monitoring database. Particular specifications were drawn up concerning the data bank and a reorganization of the database is currently in progress, as part of a specific project called Quadrige².

It was important to make the results available to a large audience and this has led to the development of a website in which scientists, marine environment management bodies and the general public can access the information (specifications sheets, study reports and monitoring reports, etc), cartographic charts and processed satellite images, thanks to dynamic mapping tools.

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Within the context of the MESH project, the first national symposium on habitat mapping was held in Saint-Malo in November 2005. Habitat mapping users exchanged and compared their studies over two days.

The first REBENT days took place in Rennes (Brittany), on May 16 and 17, 2006. The

“REBENT-Bretagne restitution workshop” was the occasion to present some of the studies that have been carried out since the implementation stage.

Future prospects

Benthic monitoring, imposed by the Water Directive, will be extended to the entire French territory, with the long-term commitment and support of the Water Agencies concerned.

However, this is not sufficient to meet all the other objectives (protected marine reserves, reference status relatingto accidental pollutions or climate change, management requirements, etc). The continuity and development of the current actions, as part of the REBENT pilot- project, will soon be discussed, notably regarding finances and staff : the time and effort spent by a small group of motivated partners in creating this regional dynamics, must be strongly encouraged. An organizational chart of research and operations on benthic biodiversity must be considered as well - either at the regional or national level- where scientific research bodies, technology centres, local authorities, R&D departments, public utilities, will be fully involved. Round-tables on this subject were held during the REBENT symposium (May 16 and 17, 2006).

For more information

REBENT project website: http://www.rebent.org/

REBENT days in Rennes (May 16 and 17, 2006): http://www.rebent.org/journees_rebent MESH project website: http://www.searchmesh.net/

Contacts

Brigitte Guillaumont, IFREMER – Brest/DYNECO/AG (brigitte.guillaumont@ifremer.fr ) Dominique Hamon, IFREMER – Brest/DYNECO/EB (dominique.hamon@ifremer.fr )

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