The North Sea ecosystem is a productive, temperate shelf sea characterized by a complex mixture of marine species living within a highly dynamic physical environment influenced by the interaction of tides and river runoff with topographic features. Based upon differences in key oceanographic and topological characteristics, the North Sea can be separated into various sub-regions such as the well-mixed, shallow (50 m) southern region versus the seasonally stratified, deeper (> 100 m) northern region, or the deep (500 m) Norwegian trench. Unique habitats include the Wadden Sea along the coasts of The Netherlands, Germany and Denmark as well as the shallow and productive Dogger Bank. A number of tidal-mixing areas and frontal zones exist which support a high biodiversity of marine fauna including relatively dense aggregations of plankton and fishes. The fact that key members of the food web exist at either their high or low latitudinal extreme is another feature that makes the species composition of the North Sea highly dynamic seasonally as well as with respect to climate variability and change. The high diversity of habitats, the high population density and the large number of active sectors (shipping, energy exploration, fishing and tourism) makes the North Sea one of the most complex, “hot spots” of anthropogenic effects worldwide.
It is now evident that the human footprint on marine systems is particularly well defined in urbanized coastal areas and shelf seas such as the North Sea where a variety of drivers of change act simultaneously to affect the structure, function and overall ‘quality’ of marine habitats. These drivers (e.g., the need to maintain food security, requirements to increase renewable energy sources, maintaining viable shipping routes) have made areas such as the North Sea ‘hotspots’ of pressures (e.g., the potential for over-fishing, increased land-based pollution causing eutrophication, physical alteration of marine habitats, continued risk of introduction of invasive alien species) acting to alter the abiotic and biotic attributes of marine ecosystems. Some of these pressures are manageable while others are not. For example, climate-driven alteration of physical, chemical, and biological properties of the ocean is a well-documented, unmanageable pressure in the North Sea. Other discrete, human pressures are manageable such as the level of nutrient loading of coastal areas from riverine discharge, fishing activities, use of the seabed for renewable energy development, and marine spatial planning in general. These manageable pressures have the power to exacerbate or potentially alleviate climate impacts and, in general, greatly increase the complexity of changing ocean conditions.
The approach taken by VECTORS in the North Sea was to provide a platform where tools developed in other VECTORS Work Packages could be implemented and combined to create new, integrative products and analyses. The work includes reviews of the key drivers and pressures acting in the North Sea, field surveys, controlled laboratory experiments, a broad array of modelling approaches and policy implications. Taken together, VECTORS activities in the North Sea provide many examples of advances in process knowledge on how drivers of change impact various sectors such as fisheries and tourism, as well as how various sectors such as fishing, shipping, aggregate extraction, renewable energy, act as drivers of change affecting North Sea species.
VECTORS activities within the North Sea have been firmly embedded within a policy framework including both regional seas agreements (OSPAR) and EU directives including the Marine Strategy Framework Directive (MSFD). The MSFD mandates that an ecosystem-based approach be implemented such that 11, broad descriptors reach levels defined as good environmental status by 2020. VECTORS activities in the North Sea directly contribute to descriptors 1 (biodiversity), 2 (invasive species) and 4 (food webs) thus, the policy relevance extends to the EU Biodiversity Strategy, particularly on invasive alien species. Moreover, a considerable amount of VECTORS research in the North Sea has examined drivers of change in key North Sea fish and their consequences for fisheries with direct relevance to the recently reformed Common Fisheries Policy.