Extraction sélective de matériaux en France et interactions avec le milieu marin

• At the national level, the marine aggregate industry produces 7.5 million tonnes of materials per year. The sum of maximum exploitation rights authorized annually for active sites has more than doubled since 2011, now standing at approximately 23.7 million tonnes. However, it remains below authorized rights, with current sites representing strong production potential. • Regular dredging of port basins and navigation channels is essential to maintain maritime traffic. In 2011, 24.7 million tonnes of dry matter were dredged in France, including 3.5 million tonnes in French Guiana. 75% of these sediments came from 7 major maritime ports, predominantly from estuarine ports of Rouen, Nantes-Saint-Nazaire and Bordeaux.

• Considered a fishing activity, sea exploitation of Laminaria digitata and Laminaria hyperborea kelp species is subject to quotas. Production is dominated by L. digitata harvesting, with 57,800 tonnes live weight equivalent landed in 2013. However, L. hyperborea production is increasing, reaching 23,000 tonnes that same year. Exploitation of these macroalgae is concentrated on Breton coasts, mainly in the Iroise Sea. • In the Mediterranean, red coral exploitation, Corallium rubrum, is also considered a fishing activity and is regulated. In 2013, 11 tonnes were landed for the Gulf of Lion area.

• These activities generate pressures on the marine environment: • physical losses and damage, mainly topographic modifications or changes in sediment composition and grain size; • chemical modifications of the environment, particularly increased turbidity or release into the water column of nutrients or contaminants contained in sediments.

• These pressures affect marine life, particularly benthic communities: organism destruction during extraction, photosynthesis disruption, changes in community faunal composition and population demographic structure of exploited species… These effects can propagate across food webs or entire ecosystems. • The extent of pressures and extraction activity impacts on the marine environment and the sustainability of these effects depend greatly on the site's initial ecological characteristics and exploitation conditions (intensity, duration…).

• The term aggregates refers to mineral-origin particles not exceeding 80 mm in size. Extracted marine aggregates come from soft seafloor deposits (sands and gravels) located between 5 and 50 m depth. These are siliceous materials (sands or gravels) or calcareous (shell sands [3]). Siliceous aggregates are often of alluvial origin. Calcareous sands have marine origin, coming from hydraulic dunes formed by tidal currents where shells and calcareous skeletons of dead marine organisms accumulate. • At the national level, the aggregate industry produces 394 million tonnes of aggregates per year, of which just under 2% are of marine origin (UNICEM, 2006-2013 average). While marine aggregates represent a small share of national production, marine aggregate extraction significantly feeds economic sectors consuming aggregates in coastal departments and areas accessible by navigable waterways. The number of requests for mining titles and marine aggregate exploitation authorizations, particularly siliceous aggregates, has increased in recent years. However, the goal of increasing the relative share of marine aggregates [4] to approximately 5% of national aggregate production is slowed by economic conditions and marine aggregate production has been in decline since 2009. • Extracted siliceous materials are mainly used for concrete production and beach nourishment. Calcareous materials are mainly used in Brittany for amending highly acidic agricultural soils. • Aggregate extraction is governed by mining code (decree no. 2006-798), except extractions dedicated to beach nourishment which require no authorization. For regulated extractions, exploitation rights are acquired following an instruction process. • In mainland France, exploited deposits are distributed between Dieppe and the Gironde estuary. The sum of maximum exploitation rights authorized for active sites has more than doubled since 2011, now standing at approximately 14 million m3, of which 13.8 million m3 for siliceous materials, or 23.5 million tonnes. Brittany is the only region in France exploiting calcareous materials, with a maximum authorized volume of 208,000 m3. • Marine extraction sites occupy 166 km2 compared to 44.6 km2 in 2012, representing just under 0.05% of metropolitan territorial waters. • There is currently no marine aggregate extraction in the Mediterranean except occasional sand extraction for beach nourishment. An extraction project in the Gulf of Lion is under study. • Overseas, there is siliceous and calcareous volcanic sand exploitation in Guadeloupe, as well as small-scale siliceous sand extraction activity in Saint-Pierre-et-Miquelon. • In the English Channel and North Sea, siliceous sand and gravel concessions are all located east of the Cotentin headland. Six are currently operating. Siliceous material extraction represents 9,540,000 m3 authorized annually for a total area of 137 km2. This volume and total concession area have increased nearly tenfold since 2011 (872,000 m3 for 15 km2). A new extensive exploitation strategy is observed, notably with three new concessions representing a total area of 120 km2, located beyond the territorial sea limit. There are currently 11 landing ports for siliceous materials in Eastern Channel. Shell sand extraction occurs exclusively in Brittany. Concessions exploiting maërl have been closed since end of 2013, with 3 still active in 2011. Three concessions are currently operating with a maximum authorized volume of 208,000 m3 annually and total authorized area of 2.5 km2. To address losses from maërl exploitation prohibition, a shell sand concession request was submitted for Lannion Bay, covering 4 km2 with maximum authorized volume of 250,000 m3 (Pointe d'Armor site). • In the Atlantic, active siliceous sand and gravel concessions are all located in the Bay of Biscay, between Loire and Gironde, in territorial waters. Six concessions are operating, three on the Chassiron deposit off Oléron island. They represent a maximum authorized annual volume of 4,159,000 m3 for a total area of nearly 26 km2. These figures are slightly lower than 2011 (4,678,000 m3 for 29.5 km2). • Overseas, an extraction site for volcanic and calcareous mixed sands for construction is currently operating in Guadeloupe. The concession area is 0.66 km2 with a maximum authorized annual volume of 118,000 m3. There is also small-scale siliceous sand extraction activity in Saint-Pierre-et-Miquelon. Extraction authorization requests are renewed annually. Two exploitation zones (in Saint-Pierre port and in Anse à l'Allumette) were authorized for 2015, with a maximum quantity of 3,150 tonnes.

• The French port system comprises state ports, including 11 major maritime ports, and ports managed by local authorities or their groups (over 500). • The 11 major maritime ports, 3 of which are estuarine (Rouen, Nantes-Saint-Nazaire and Bordeaux), handle over 80% of France's maritime goods traffic. • Port authorities or their delegates are responsible for ensuring port access to enable installation exploitation and ship safety. Dredging maintenance of navigation channels and port basins is therefore unavoidable. Two dredging types exist: • maintenance dredging, nearly permanent for estuarine ports, consisting of port and access route maintenance; • dredging undertaken during specific work (navigation channel deepening, port construction or extension), representing approximately 5% of all dredging performed. • These activities are subject to environmental legislation, particularly water laws. The administrative regime applying to dredging is determined by three criteria: volume of sediments to extract, sediment quality (physicochemical characteristics and contaminant concentration), and distance between dredging zone and nearest marine culture areas. Depending on these data, dredging may be performed without prior administrative procedure or may be subject to declaration or authorization regime under water law. Since June 1, 2012, authorization request files must include an environmental impact study with content specified in article R 122-5 of the environmental code. • Dredged material is most often submerged at sea (dumping). This represented 94% of total dredged sediment quantity, excluding French Guiana, in 2010. It may also be stored on land, to lesser extent. Finally, it can also be used to nourish beaches weakened by coastal erosion. • Three different dredging techniques exist (hydraulic, mechanical and hydrodynamic). The most used dredging technique in mainland France is hydraulic dredging (71.3% of dredged sediments in major maritime ports in 2010, 86.3% in other ports). • Annual dredged sediment quantity varies mainly year-to-year when new or deepening work is performed. In 2011, 24.7 million tonnes of dry matter were dredged in France, including 3.5 million tonnes in French Guiana. • A large majority (74% of total in 2011) of this material comes from 7 major metropolitan maritime ports (18.3 million tonnes in 2011). Year 2009 stands out with much larger dredged volumes totaling 38 million tonnes of dry matter, including 29.6 million tonnes dredged at 7 major metropolitan maritime ports. Work undertaken at Havre (Port 2000 extension) and Marseille ports that year were responsible for this increase. • Sediment quantity dredged in estuarine ports of Rouen, Nantes-Saint-Nazaire and Bordeaux is greater (75% of dredged sediments in 2010) than in other major maritime ports, due to significant alluvial inputs at corresponding estuaries. In the Mediterranean, dredged volumes are much smaller (3 million m3 in 2008), with 90% coming from Marseille major maritime port.

• French seaweed production is estimated at 70,000 tonnes annually. Wild seaweed represents the majority of production, with only 50 tonnes coming from seaweed farming. They are mainly harvested along Breton coasts, either at sea using seaweed vessels with mechanized equipment (scrapers and combs), or on the foreshore by foot harvesters. • French seaweed production is largely dominated by kelp exploitation. Two kelp species are exploited: Laminaria digitata and Laminaria hyperborea. Considered a fishing activity, their exploitation is governed by strict management rules. • L. digitata production is seasonal, with biomass varying significantly throughout the year, showing winter biomass loss of 50 to 60% compared to summer biomass. Campaigns run between May and October, with peak activity in summer. • L. hyperborea represents a much more important source than L. digitata on metropolitan coasts and, with less yearly biomass variation, is also exploited in winter. • Laminaria digitata is harvested by seaweed vessels equipped with an articulated crane to which a scraper is fixed. Laminaria hyperborea harvesting is performed using selective fishing equipment called a "Norwegian comb," which is dragged by the vessel like a dredge across kelp fields, uprooting the largest specimens. • Kelp exploitation is concentrated on Breton coasts, mainly in the Iroise Sea. Resource estimates on Finistère coasts are currently underway. Production is dominated by Laminaria digitata fishing, with 57,800 tonnes live weight equivalent landed in 2013 (52,900 tonne average over 1985-2014 period). The entire licensed fleet of 35 seaweed vessels has a daily quota of 970 tonnes. A new management device to improve resource exploitation was implemented in 2014, with each vessel assigned a zone for exclusive L. digitata resource responsibility. • Breton kelp is mainly landed at Lanildut port in Finistère. It is used for alginate production, with numerous industrial applications in food and pharmaceutical industries. • Unlike Laminaria digitata, whose production declined 20% over 20 years, L. hyperborea exploitation has increased strongly in recent years. Previously anecdotal, it really began in 1997, with annual volumes under 5,000 tonnes until 2007. Between 2007 and 2012, 11 vessels were equipped for L. hyperborea harvesting, including 6 in the Molène archipelago (60–80% of Breton production) and 3 in the Roscoff area (5–20%). Volume increased from 9,000 tonnes harvested in 2007 to 23,000 tonnes in 2013. Total landings in managed zones (Finistère coastline) are limited to maximum 35,600 tonnes for 2015. Since this species grows slower than L. digitata, a fallow system was implemented on small areas to prevent overexploitation. Altogether, between 35,000 and 60,000 tonnes of kelp are harvested annually since 2007.

• Mediterranean red coral, Corallium rubrum, is an invertebrate animal close to sea fans (cnidarian phylum) forming tree-like red colonies. It colonizes rocky substrates with low light exposure from a few metres depth, notably in caves and overhangs, down to several hundred metres. It is primarily present in central and western Mediterranean basins, notably in Italy (Sardinia and mainland coast) and France (Corsica and mainland coast). • No current estimate of red coral resources on French Mediterranean coasts is available. Exploited since antiquity for artisanal crafts and jewelry, coral has recently attracted underwater tourism interest, translating to economic activity (commercial dive clubs). • Total Mediterranean production reached a maximum of 98 tonnes in 1978, with 72 tonnes from Sardinia. In 2013, French production outside Corsica was approximately 11 tonnes. • Mediterranean production halving over 40 years appears correlated with resource scarcity and major evolution in fishing methods and activity management. European regulation no. 1626/94 of June 27, 1994 prohibited trawled equipment use for coral harvesting. Today, it is performed exclusively using scuba diving. • The number of coral fishing licenses granted annually by authorities is decided after consulting profession representatives. Currently, twenty coral fishers operate on mainland and 10 in Corsica. Along the Côte Vermeille, fishing is authorized from May 1 to September 30 inclusive, at depths exceeding 50 m, prohibited within Cerbère-Banyuls national nature reserve perimeter. Maximum annual coral extraction per fisher is 50 kg, with harvested colony base diameter exceeding 8 mm. In Corsica, fishing is also prohibited between 0 and 50 m depth, with a fallow system implemented (Dirm Mediterranean). • In Provence-Alpes-Côte d'Azur region, conversely, there is no depth restriction, red coral being rarely present at depths exceeding 50 m. However, harvesting only colonies with basal diameter exceeding 7 mm is recommended. Since October 2013, two reserves within Calanques national park and Côte Bleue marine park are prohibited from exploitation.

• Human activities described in this document directly exploit marine habitats, resulting in habitat removal or partial removal of mineral or organic constituents, exercising physicochemical pressures on the environment depending on exploitation modalities and intensity. These pressures in turn create impacts on marine habitats and communities, with extent depending on their initial state and pressure sensitivity. • Benthic community composition is determined by abiotic factors such as substrate nature, wave exposure mode, current strength, depth (influencing temperature and light), freshwater inputs from watercourses (influencing salinity, turbidity and water nutrient concentration) and available oxygen quantity in soft sediments. Different factor combinations generate diverse communities with varied species and ecological richness. Species richness refers to the number of present species. Ecological richness is a more anthropomorphic criterion attributing ecological value to communities or habitats based on rarity (Hermella reefs), structural interest (maërl), or functional value (kelp forests, seagrass beds…).

• Environmental pressure extent The physicochemical pressure extent from extraction activities varies with exploitation modalities and exploited site physical environment. Exploitation modalities are described by extraction intensity (hours per hectare per year), topographic modifications generated (extraction furrow number, excavation depth), seasonality, frequency and exploitation duration. Pre-exploitation site physical environment is characterized by topographic, granulometric and hydrodynamic conditions. • Sediment removal causes local bathymetric level lowering and seafloor topography modification. Furrow imprints vary between 30 and 60 cm depth for 2 to 3 m width. On heavily exploited sites, successive furrows overlap, generating substrate overdeepenings reaching several metres. Local hydrodynamic regime may also be modified, altering sedimentation processes. • Aggregate extraction can also form a turbid plume several metres wide, increasing water turbidity at depth and surface. Most studies show this plume generally extends 200 to 500 m beyond the vessel, mainly depending on hydrodynamic and meteorological conditions. These particles subsequently redeposit on the seafloor. • According to substrate nature and local hydrodynamic conditions, aggregate removal may modify sediment composition by exposing deeper sediment layers with different grain size. Furrows created by equipment passage, characterized by reduced currents, can fill with fine particles brought by tidal currents. Furthermore, grain size is susceptible to modification in the turbid plume deposit zone, enriching fine particles. • Aggregate extraction potential effects on coastline are debated. Following extraction, exploited site morphology change may modify seafloor current regime, potentially altering surface sediment equilibrium and thus affecting coastal erosion, particularly if extraction site is nearshore and shallow. Sediment aspiration destroys sessile or poorly mobile fauna. Temporary turbidity increase and turbid plume particle sedimentation can cause high mortality in filter-feeding animals. Extraction thus reduces macrofauna abundance, biomass and species richness, with 40 to 95% organism number and biomass reduction and 30 to 70% species richness decrease measured. Macrofauna impact extent is greater with higher extraction intensity. • Marine aggregate extraction impacts on marine life Short-term, species richness often decreases with biomass increasing, showing opportunistic species and those tolerant to drastic environmental condition changes. On still-exploited sites, new communities can show high juvenile individual rates unable to reach maturity due to successive disturbances. • Benthic community modifications within extraction sites can propagate to higher trophic levels, particularly fish communities. While destruction impact on nursery or spawning areas on fish communities is undoubted, aggregate extraction impacts outside these zones are harder to evaluate. Scientific studies identified variable effects: strong fish species number and abundance decline, fish community composition changes or no negative effects on fisheries, either onsite or nearby. Fish population identified impacts depend greatly on study site, monitoring temporal scale and concerned species. • Returning to stable state near or equivalent to initial state requires activity stoppage and return to initial morphobathymetric and sedimentary conditions. Furrows can persist beyond ten years and site recolonization could occur 2 to over 10 years after exploitation stoppage; return to near-initial state remaining extraction site dependent.

• Dredging operations cause local turbidity increase (dredge passage and overflow water discharge), accompanied by temporary nutrient salt release and sediment-contained contaminant remobilization (metal and organic micropollutants). Dredged sediment quality largely depends on contaminant inputs from watersheds and nearby coastal industrial and port activities. • Like aggregate extraction, dredging operations cause habitat and resident species destruction. Most dredged volumes come from estuarine ports, making dredging effects on these complex ecosystems difficult to interpret, given highly variable environmental conditions (terrigenic input variations, hydrological variations…) and different anthropic pressures. Water turbidity increase impairs light propagation through the water column, potentially temporarily impairing phytoplankton photosynthetic capacity and benthic plant communities. Nutrient salt release conversely has stimulating effect. These two factors combination is thus susceptible to temporarily modifying primary production. • Port dredging is not considered highly impactful to benthic habitats when occurring in highly anthropized port enclosures. However, most dredged volumes come from regular estuarine navigation channel maintenance, outside these enclosures. For many marine species, estuarine environments are essential with environmental protection and management measures, notably through the Natura 2000 network. Distinguishing port dredging impacts from other disturbance sources and quantifying them is difficult. • Like aggregate extraction, hydraulic extraction can aspirate benthic fauna and demersal fish. Maintenance dredging can also cause estuarine habitat and biocenosis destruction and degradation. Major estuarine maritime ports already implement measures to limit dredging ecological impacts: most impactful technique use limitation, dredging volume optimization relative to actual needs and dredging scheduling in periods more compatible with estuarine ecological functioning.

• Kelp forests form stratified habitat influencing lower strata hydrodynamic and light conditions. Diverse microhabitat availability for different species makes kelp forests one of rocky coastal environment's most productive and complex biotopes, sheltering highly diverse and abundant flora and fauna. • Exploitation generates two main pressures: removing more or less algal biomass fraction and thus habitat, and on zones with mobile rocky block seafloor, substrate disturbance from block displacement, overturning or removal. Substrate disturbance may accompany local temporary turbidity increase, notably after Norwegian comb passage. • Currently, L. hyperborea autumn and winter harvesting appears to represent only negligible fraction compared to natural uprooting from winter storms, with estimates of approximately 200,000 tonnes L. hyperborea annually torn in the Iroise Sea. For L. digitata, exploitation spans May to mid-October, an important period for many marine animals using this habitat lifecycle. This algae removal is estimated as similar magnitude to natural losses without exploitation; L. digitata removal is thus susceptible to doubling losses incurred without exploitation. • Furthermore, kelp removal releases colonization space for other algal species more resistant to environmental stress, with resulting inter-specific competition fragilizing kelp population persistence, notably in current climate warming context. • To partially remedy kelp exploitation environmental impact scientific study lack, the HYPERIMP program, coordinated between 2011 and 2012 by Iroise Natural Marine Park, examined Norwegian comb use incidence on L. hyperborea biocenosis. According to study results, this tool use impact appears limited. However, it should be noted that monitoring occurred with single comb pass, with block overturning impacts from comb passage not evaluated in this study.

• Red coral presents biological characteristics making it particularly overexploitation-vulnerable, with very slow growth and late sexual maturity. It lacks national protection but its exploitation is regulated: red coral concerns two conventions and international regulation ratified by France, with exploitation regulated (species referenced in Barcelona and Bern Convention annex III, and Habitats-Fauna-Flora directive annex V). At Mediterranean scale, consensus exists that shallow-water red coral populations are overexploited. • Fished sectors show strong population demographic structure erosion, meaning age-class individual distribution. Large colonies, also most fertile, are preferentially harvested, with C. rubrum colonies rarely exceeding 10 to 15 cm height and 1 cm basal diameter at 60 m or shallower depths today. This imbalance is unobserved in marine protected areas where harvesting is prohibited. This motivated exploitation prohibition between 0 and 50 m depth in Corsica and along Côte Vermeille. Small-large colony demographic imbalance reduces population reproductive capacity (larval dispersal capacity and population connectivity studies ongoing), fragilizing non-renewable resource at human lifespan scale.

• In recent decades, species and habitat protection has substantially increased, notably through European directives (Birds and Habitats-Fauna-Flora directives). Species or habitat protection lists were prepared and marine protected areas (Natura 2000 sites) designated for habitats and species requiring special conservation zone (SCZ) designation for protection. More recently, Marine Strategy Framework Directive imposes member states achieving or maintaining good marine environmental status, including habitats (pelagic and benthic) and species (birds, marine mammals, fish…). Human activities modifying marine seafloor integrity are also subject to this directive and governed by national environmental regulation, due to potential benthic habitat impacts or even ecosystems. • -* Context Marine seafloor presents great habitat variety, dependent on different abiotic and biotic factors. Depth, substrate nature, permanent or temporary submersion character, water column characteristics, hydrodynamic energy, light quantity, salinity… condition living organism presence and interactions. Marine material extraction, mineral or living, represents important economic stakes, however exercising physicochemical pressures depending on exploitation modalities and intensity. These pressures in turn create marine habitat and community impacts, partly depending on these pressure sensitivity. Selective material extraction activities are addressed here from their marine ecosystem interaction angle, with this document objective being documented knowledge summary synthesis on these interactions. • - Definition In this document scope, selective material extraction is defined as targeted removal for industrial purposes of mineral and biological matter from marine seafloor soil and subsoil. These material extraction generates various pressures, mainly topographic and granulometric seafloor modifications. Ecological impacts essentially consist of immediate, total or partial targeted benthic habitat destruction and associated biocenosis (living beings), plus resulting benthic community modifications. Addressed extraction activities are: (1) marine aggregate extraction; (2) port sediment dredging; (3) seaweed exploitation at sea; (4) Mediterranean red coral exploitation. • - Sources Thematic contribution to Marine Strategy Framework Directive initial assessment regarding selective material extraction. Source data: Cerema, FAO Fishstat, Ifremer, Mineralinfo, SARL Allen-Mahé, UNICEM, UNPG. Some document elements result from interviews, with authors thanking: M. Laurans (Ifremer), Y. Troadec (marine fisher, Breton seaweed fishers representative), and Ph. Le Niliot (Iroise Natural Marine Park).