Monitoring the Prestige oil spill impacts on the northern Iberian shelf ecosystem Francisco Sánchez Alberto Serrano Francisco Velasco Santiago Parra Inmaculada Frutos Simposio VERTIMAR Vigo

CATASTROPHE SCENARIO On November 2002, the tanker Prestige carrying tons of heavy oil (M-100) produced a large spill over the continental shelf and oceanic waters off Galicia. As a consequence, the drift of the oil slick during several months over a large area of the Bay of Biscay caused sedimentation events on the deep continental shelf grounds. The special characteristics of the Prestige spill had necessary to evaluate the biological effects in the continental shelf area. Possible effects on biota of shelf ecosystem: No direct lethal effects Direct sub-lethal effects Indirect effects (trophic input medium and large term)

TROPHIC MODEL OF THE CONTINENTAL SHELF ECOSYSTEM

To quantify the distribution of fuel on the bottom and on the species, with particular attention on fishing gears efficiency To estimate the impact on the shelf communities including the different compartments: infaunal, suprabenthic, epibenthic and demersal To estimate changes in the abundance and distribution of the main commercial species according to the previous situation before the catastrophe Trophic ecology of the main species of fish and some invertebrates and comparison with the results of the historical series Assessment of the impact of the fuel on the growth and batch fecundity in fishes of commercial and ecological interest (CSIC – IEO posters) To estimate the effects on fisheries Generate a trophodynamic model to summarize the effects GENERAL OBJECTIVES

1.Infaunal communities - Box corer (Galicia) 2.Suprabenthic communities - Suprabenthic sledge (Galicia) 3.Epibenthic commun. - Beam trawl (Galicia and Cantabrian sea) 4.Demersal species - Otter trawl (Galicia and Cantabrian sea) EXPERIMENTAL DESIGN OF SURVEYS Stations arranged in a radial pattern, located in 5 geographic sectors and 3 depth strata December January 2003 Mars - April 2003 September - October 2003 (120 trawl hauls) Mars - April 2004 September - October 2004 (120 trawl hauls)

DEPOSITS OF HEAVY OIL ON THE CONTINENTAL SHELF

DISTRIBUTION OF HEAVY OIL (tar aggregates) ON GALICIA SHELF

DRIFT OF OIL TO THE CANTABRIAN CONTINENTAL SHELF

INFAUNAL COMMUNITIES Parra, S. & I. Frutos, Temporal evolution of infaunal and suprabenthic communities on the Galician continental shelf (NW, Iberian Peninsula), after the Prestige oil spill. (poster, this Symposium) 159 species

SUPRABENTHIC COMMUNITIES Parra, S. & I. Frutos, Temporal evolution of infaunal and suprabenthic communities on the Galician continental shelf (NW, Iberian Peninsula), after the Prestige oil spill. (poster, this Symposium) 136 species

EPIBENTHIC COMMUNITIES 277 species 114 samples Environmental variables Depth Latitude Sediment: fine sands, coarse sand, Q 50 sorting coefficient, organic content Prestige: Tar aggregates amount Samples codes: Season: w = winter s = spring a = autumn Zone: 1 = Rias Baixas 2 = Costa da Morte 3 = Galicia North Depth strata: A = m B = m C = m RDA ordination biplot of environmental variables and samples Spring Autumn Winter Tar Latitude Depth % O.M. Q 50 S0S0 % Fine sand % Costa Morte Latitude % Coarse sand % Mud Inner shelf Middle shelf Outer shelf Statistical tests Ecological indices: no significant correlations between species richness, biomass and diversity respect: Tar aggregates (oil) Impact zone (spatial approach) post-spill periods (temporal approach) In: Serrano et al, Spatial and temporal changes in benthic communities of the Galician continental shelf after the Prestige oil spill. MPB

DEMERSAL AND COMMERCIAL SPECIES RDA ordination biplot of environmental variables and samples 175 species 126 samples Environmental variables Depth Latitude Sediment: fine sands, coarse sand, Q 50 sorting coefficient, organic content Prestige: Tar aggregates amount Samples codes: Season: w = winter s = spring a = autumn Zone: 1 = Rias Baixas 2 = Costa da Morte 3 = Galicia North Depth strata: A = m B = m C = m Inner shelf Middle shelf Outer shelf Statistical tests Ecological indices: no significant correlations between species richness, biomass and diversity respect: Tar aggregates (oil) Impact zone (spatial approach) Pre-spill and post-spill periods (temporal approach) In: Serrano et al, Spatial and temporal changes in benthic communities of the Galician continental shelf after the Prestige oil spill. MPB

SIMPER analysis: 7 indicator taxa explaining 50% of disimilarity between 2002 and 2003 (impact), and between 2003 and 2004 (recovery) Impact indicator groups Serrano, et al., Decrease and rebound effect of some indicator taxa after the Prestige oil spill in the Galician Atlantic shelf. (poster, this Symposium)

Commercial species: MEGRIM (L. boscii) Age 0Age 1

Commercial species: MEGRIM (L. boscii) Year-class abundance (number/30 min. trawl)

Commercial species: NORWAY LOBSTER (N. norvegicus) Norway lobster biomass differences December October 2002

Commercial species: NORWAY LOBSTER (N. norvegicus) Sanchez, et al., Monitoring the Prestige oil impacts on some key species of the Northern Iberian shelf. MPB

At the moment we can not conclude about the degree of impact of the Prestige catastrophe on the shelf communities and their resources. We must to wait and to try to differentiate the real impact and the natural variability of the populations. Thank you very much for your attention GENERAL CONCLUSION