Marine food webs

Marine food webs describe the linkages between all living organisms found in the marine environment. At a basic level, every plant and animal species depends on another plant or animal species for its survival. This interdependency can be explored in predator–prey relationships or food chains.

Individual food chains operate within much larger and more complex networks called food webs. In turn, food webs are one of the main regulators of ecosystem dynamics. They play a role in the way ecosystems respond to natural and human-induced changes.

A simplified marine food web

Source: © JNCC/ Alejandra Bize

Slight changes in food webs can lead to dramatic changes in an ecosystem and food web dynamics. They are referred to as ecological regime shifts, and several have been observed in a number of Europe's regional seas over the past century. Since the late 1980s, climate-caused regime shifts may have made the seas less resilient to other anthropogenic pressures influencing each regional sea, thereby contributing to the patterns of change that have been subsequently observed.

Several pressures influence the marine food webs, e.g. extraction of fish and shellfish, eutrophication, and marine climate change.

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Relevant MSFD Descriptors

Descriptor 1. Biodiversity is maintained

 The quality and occurrence of habitats and the distribution and abundance of species are in line with prevailing physiographic, geographic and climatic conditions.

Descriptor 3. The population of commercial fish species is healthy

Populations of all commercially exploited fish and shellfish are within safe biological limits, exhibiting a population age and size distribution that is indicative of a healthy stock

Descriptor 4. Elements of food webs ensure long-term abundance and reproduction

All elements of the marine food webs, to the extent that they are known, occur at normal abundance and diversity and levels capable of ensuring the long-term abundance of the species and the retention of their full reproductive capacity