Marine benthos refers to organisms living in, on or near the seabed, which can be rocky or sedimentary. Benthic communities can be subdivided by size (from smallest to largest microbenthos, meiobenthos, macrobenthos, megabenthos) or in terms of where organisms live in relation to surface of the sea bed (infauna, epibenthos, hyperbenthos). In deeper water, benthic communities generally derive their food by filtering plankton from the seawater or by eating detritus deposited on the sea bed. In intertidal areas or shallow seas where the water is clear enough for light to penetrate to the seabed, photosynthetic microbes or large plants or algae such as seagrasses and seaweeds, can also provide food to grazers and therefore support food-webs. Algal beds can be among the most productive habitats on earth and can also provide food as detritus to habitats in deeper water.  Benthos in turn are preyed on by other benthic organisms or by demersal fish.  The activity of benthic organisms affects pelagic-benthic fluxes of materials and chemicals. Many benthic organisms are commercially important themselves (e.g. crabs, lobsters, shrimps, scallops, mussels, oysters), or gain commercial importance by underpinning food-chains involving commercially important demersal fish (e.g. sole, plaice, cod).

The benthos is particularly affected by human activities that use, impact or alter the seabed, such as trawling, dredging and aggregate extraction, or the development of new structures including wind turbines. It is also sensitive to activities that alter water quality or clarity, or influence concentrations of nutrients or toxins.  Changes in community structure or biodiversity driven by physical, chemical or biological factors (including invasive species) can alter ecosystem processes and influence provision of ecosystem services and benefits to society.

VECTORS research has investigated many of these drivers and their impacts through a number of studies, including systematic reviews of impacts on biodiversity and ecosystem functioning of algal blooms, invasive seaweeds and bioengineers, and experimental case studies on impacts of invasive crabs, seaweeds, amphipods and mussels in different parts of Europe. In the North Sea, there has been a particular focus on invasive Pacific oysters, including assessment of their impacts on ecosystem services and consideration of the practicalities and economics of management options. Researchers also modelled changes in distribution and productivity of commercial flatfish such as sole.