Wageningen IMARES is een samenwerkingsverband tussen Wageningen UR en TNO IMARES Ecological sensitivity in the Netherlands part of the North Sea J.A. van Dalfsen

Ecological Risks Main aspects of oil pollution: - risk to ecological vulnerable areas - risk to birds - risk to organisms in the water column, the seabed and shores

What is sensitive or vulnerable?

Fishing areas & Benthos diversity

Important sea bird areas at the North Sea (Skov et al.) Avg/year Ranked according to densities

Risk to Birds Different species vary in terms of their sensitivity to oil The sensitivity of seabirds depends largely on behavioural characteristics and species-specific differences in terms of the risk of exposure to oil Seabirds are particularly vulnerable to oil because even the smallest amount destroys the insulating and waterproofing abilities of their feathers TernPuffinGuillemot

Oil Vulnerability Indices Factors used by Camphuysen (1989) in evaluating an oil vulnerability index for birds in the southern North Sea Range BehaviourExposure 1 - Breeding 5 - Roosting 11 - Spring 2 - Migration 6 - Foraging 12 - Summer 3 - Wintering 7 - Reaction to disturbance 13 - Autumn 4 - Marine orientation 8 - Flocking14 – Winter 9 - Nesting density 10 - Specialisation The scale of vulnerability of seabirds depends not only on numbers present but also on behavioural and other characteristics of the species involved. An Oil Vulnerability Indices assesses these characteristics and species-specific sensitivity to oil pollution

Most sensitive seabird families (Camphuysen, 1989) Mean oil vulnerability index (OVI) scores for seabird families of the North Sea Family Mean OVI Min Max Auks Divers Cormorants and shags Gannets and boobies Sea ducks Petrels and shearwaters Diving ducks Grebes Storm-petrels Terns Gulls Skuas Phalaropes

Vulnerability to Oil spill Time and place (UK Atlas)

Natural variation 9 years of December countings Auk - Guillemot

Data density Information covers not the total DCS

Bird value map for the DCS Based on a Ecovalue per species Multiplied with abundance per time period of 2 months

Region Marine Estuary Habitat Water surface, water column, inter-tidal, sub-tidal, Terrestrial, Sub-habitat water surface, shallow water, deep water, sandy beach, dunes, hard substrate, salt marsh, mud flats, reefs & beds, Type of organism Birds, mammals, fish, plankton, fish, benthos, vegetation, insects Risk to the water column, sea bed and land Habitats characteristics are mostly physical (MESH), Whereas sensitivity depends on species

Risks to the water column and sea bed Ecotox effects on plankton, benthos & fish Physical stress Reduced feeding efficiency of organisms Areas of different ecological value, with species having different sensitivities to oil Some habitats depend on certain key species (bio-engineers) Recovery time

Sensitivity and the use of dispersants Main aspects of oil pollution: - risk to ecological vulnerable areas - risk to birds - risk to organisms in the water column or on the seabed Does this change when dispersants are used?

Ecological sensitivity and the use of Dispersants Change from water surface to the water column and sea bed: Increased concentration hydrocarbon components Increased bio-availability of components of oil & dispersants Toxic effect Physical effect (Depending type/amount of oil, water depth, water temperature, turbulence etc.)  Change of sensitive areas and species  enters more easily in the food web

‘Marine’ food web Copepod production

Sand eel as example Feeds on copepods, worms and plankton It important food for different birds e.g.Terns What is the fate of dispersed oil and what are the risk to this food chain? Are there long term or chronic effects to expect? Noorse Stern

Different species and areas vary in terms of their sensitivity to oil The sensitivity of sea areas depends mainly on the numbers and behaviour of sensitive (seabird) species occurring there The amount of oil spilled is less important than the season in which spillage occurs, and the location of that spillage. A small amount of oil in a crucial seabird habitat can be far more deadly than a large oil spill elsewhere. Information on bird species presence on a European or DCS scale is far from complete. This lack in information prevents a good decision process on the use of dispersants Conclusions

Conclusions II There is poor environmental baseline data for comparing the status of a situation prior to and after oiling The effect of oil hydrocarbons thru the food web is still difficult to quantify There is a lack in integrated population or ecosystem studies compared to single species studies

1. Collection and compiling information on the ecosystem values of the DCS. 2. Natural variation in ecosystems stresses the need for efficient monitoring 3. Long-term, chronic sub-lethal impacts of oil pollution need to be studied, including food web studies 4. Evaluation of the sensitivity of the ecosystem components on oill spills detergents 5. Produce adequate information for the decisions to safeguard the most valuable areas and populations in the case of an oil spill Conclusions III what is needed?

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