4.7 Environmental considerations
Coastal lagoons face the following problems with respect to ecosystem productivity and capacity to sustain fishers’ livelihoods.
Most of the French lagoons have to face increasing anthropogenic pressures as they are the final receivers of pollution, in particular the incoming quantities of nutrients coming from the water treatment plants of the surrounding cities or drained together with pesticides from the agricultural activities in their catchment basins are high (for example those coming from rice culture in the Camargue area, from vineyards in the Thau lagoon, from maintenance of urban gardens or from chemical treatments against mosquitoes in the Palavasian area). Detergents are particularly concentrated during the summer touristic season, while pesticides are more abundant in winter during the periods of rain.
Some lagoons like Berre are subject to pollution coming from the oil industry, while others like Bages-Sigean are threatened by the proximity of chemical plants.
In the Berre lagoon from 1966 to 1993, the diversion of the Durance River to feed a hydroelectric power plant has induced an inflow of freshwater of almost four times the volume of the lagoon water, at least doubling the annual natural discharge of suspended matter and nutrients. The current global discharges are now lower due to the restrictions applied to the power plant and also to dryer conditions and better treatment of sewage waters along the catchment basin. Until 1966 the Berre lagoon was a salty lagoon with a highly diversified marine fauna and flora. The decrease in biodiversity, the eutrophication processes and the chemical pollution of water and sediments have deeply altered that natural environment. Almost all the vegetal species have disappeared, including the eelgrass Zostera marina, a keystone species that previously constituted extensive meadows in the lagoon; while the marine animal populations have declined or have disappeared and they have been substituted by a euryhaline macrofauna. Due to the anoxic conditions existing in the deeper parts of the lagoon, the benthic life has disappeared.
The faecal germs have an impact on filter-feeders (shellfish), which can become contaminated and unfit for consumption (risk of typhoid, hepatitis). The fecal bacteria (Escherichia coli and Streptococcus) show periods of particular abundance after heavy rainfall and in the lagoon where shellfish aquaculture is developed, consumption of shellfish is regularly prohibited for some time.
The phenomenon of “malaigue”, an eutrophication due to the excess of nutrients combined with the high summer temperatures, is regularly observed in most of the French Mediterranean lagoons; they have biological (mortalities of shellfishes and fishes, development of unwanted plants or animals), economic (benefit loss resulting from oysters and mussels mortalities) and touristic (bad water quality, bad smells due to the production of hydrogen sulphide). Another recurring problem for the French lagoons is the sporadic development of toxic microalgae and 9
especially those of the genus Alexandrium and Dinophysis, the toxins of which are dangerous 5
for humans and are concentrated by the oysters and the mussels.
Since 2009, there is a high mortality of young oysters, the origin of which has not yet been completely determined. This crisis led 20 percent of the producers to change their strategy, some of them increasing their mussel production, others beginning to produce mussels for the first time.
4.8 References
Arfi, R. 1991. Etang de Berre 1990 suivi exceptionnel du milieu. Marseille, France, Centre Oceano. 15 pp.
Barral, M., Sourribes, V., Bourgeois, E., Gavoty, E., Barre, N. & Tillier, C. 2007. Vers une gestion integree des lagunes mediterraneennes. Tome 1: synthese generale. Pole relais lagunes mediterraneennes.Tour du Valat 1, Conservatoire des Espaces Naturels de LR2. 73 pp.
Cepralmar. 2003. Suivi de la peche aux petits metiers. Prud’homie du Languedoc, Roussillon, Annee 2002: 1–8.
Cepralmar. 1984. Etangs cotiers du Languedoc-Roussillon. Situation actuelle. CEE Programme Mediterraneen integre: enquetes preparatoires. Rapp. Polycop. 294 pp.
Charret, C.L. 2011. Etude des lagunes mediterraneennes. FM0E 203 Ecosystemes aquatiques, organisation et fonctionnement. Master 1 BGAE, Universite Montpellier II. 12pp.
Diren Languedoc-Roussillon, Biotope, Cen-lr, Tour du Valat, Pole relais lagunes mediterraneennes. 2007. Catalogue regional des mesures de gestion des habitats et des especes d’interet communautaire – type lagunes littorales. 274 pp
Farrugio, H. & Le Corre, G. 1984. Les pecheries de lagune en Mediterranee, definition d'une strategie d'evaluation. Rapport final convention CEE XIV-B1-84/2/MO3 P1. Ifremer DRV 85/PE/Sete, France. 251 pp.
Gervasoni, E., Perignon, A., Sourisseau, E., Rey-Valette, H., Yimam, E. & Feldman N. 2011. Monographie, La conchyliculture en Mediterranee. Cepralmar, CRCM, Lameta. 29 pp.
Le Corre, G. 1990. Suivi exceptionnel de l’etang de Berre. Bilan halieutique. Ifremer DRV. Rapp. 27 pp.
Pole relais lagunes mediterraneennes. 2008. Mieux gerer les lagunes mediterraneennes. Novaterra, Delphine Bonnet Ed. 94 pp
Quignard, J.P. 1989. Caracteristiques biologiques et environnementales des lagunes des cotes francaises medirerraneennes. Academie de Lascours, Actes 1989-2. pp. 83–102.
Quignard, J.P. & Zaouali, J. 1980. Les lagunes perimediterraneennes. Bibliographie annotee. Bulletin de l‘Office national des Peches Tunisie, IV n°2: 293–360.
Reynal, L. 1980. La peche sur les etangs de la cote orientale Corse. Faculte de Montpellier. 60 pp. (Memoire DEA).