Marine Biodiversity

Definition of Biodiversity: The variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems. (The Convention on Biological Diversity). This is the common definition for Biodiversity, other definitions can be discussed in the article

Marine biodiversity is the variety of life in the marine environment. It includes genetic variation within species, the diversity and relative abundance of species, and the diversity of habitats, communities and ecosystems. Biodiversity can also be described in terms of the ecological traits and functions performed by organisms. Marine biodiversity has several characteristics that distinguish it from terrestrial biodiversity; these are discussed in The distinctive features of marine biodiversity.

Importance of marine biodiversity

Marine biodiversity underpins the functioning of marine ecosystems. Different organisms contribute to primary production, food webs, decomposition, nutrient cycling, habitat formation and many other ecological processes. The diversity of species and ecological functions can also increase the capacity of ecosystems to maintain their functioning under environmental variability and disturbance. Through these processes, marine biodiversity supports ecosystem services such as fisheries production, water purification, carbon storage, coastal protection and recreational and cultural values.

Levels of marine biodiversity

Marine biodiversity can be described at different levels and from different perspectives:

• Genetic diversity refers to genetic variation within and among populations of a species.
• Species diversity (taxonomic diversity) describes the variety and relative abundance of species or other taxonomic groups in a community or ecosystem.
• Ecosystem diversity refers to the variety of habitats, biological communities and ecosystems.
• Functional diversity describes the variety and distribution of functional traits represented by organisms in a community.

Patterns of marine biodiversity

Marine environments encompass extremely diverse habitats and environmental conditions, from estuaries and tidal flats to rocky shores, seagrass beds, coral reefs, continental shelves and the deep sea. Differences in depth, substrate, light, temperature, salinity, hydrodynamic conditions and other environmental factors create habitats for very different species and communities. Major types of marine habitats are introduced in the article Marine habitats and ecosystems, which provides a gateway to Coastal Wiki articles describing these habitats and their biodiversity.

Measuring and describing biodiversity

Biodiversity is not synonymous with species number. Richness, abundance, evenness, composition, genetic variation and functional traits provide different information for describing ecosystem condition, change and functioning. This is described in the articles Measurements of biodiversity, Functional diversity and Biological Trait Analysis and references therein. Traditional sampling tools for the marine environment are increasingly complemented by new monitoring approaches, including environmental DNA (eDNA).

Biodiversity and ecosystem functioning

Biodiversity influences marine ecosystem functioning through the ecological traits, interactions and relative abundances of organisms. The role of biodiversity in ecosystem functioning and the provision of services is discussed in the article Biodiversity, ecosystem functioning and ecosystem function. The articles Resilience and resistance and Ecological thresholds and regime shifts discuss how ecosystems respond to disturbance, degradation and recovery, including the role of biodiversity in these responses.

Changes and threats to marine biodiversity

Many human activities threaten marine biodiversity, as discussed in the article Threats to the coastal zone. Particularly damaging are fisheries, eutrophication, pollution, non-native species invasions, habitat destruction and fragmentation and climate change. Biodiversity change includes much more than species extinction: abundances, community composition, traits and ecological interactions may change substantially while species richness changes little, as discussed in the article Disturbances, biodiversity changes and ecosystem stability.

Conservation, management and restoration

Conserving marine biodiversity requires protection of important habitats and species, sustainable use of marine resources, reduction of human pressures and restoration of degraded ecosystems. Marine Protected Areas (MPAs) are an important instrument for area-based conservation. For areas beyond national jurisdiction, the High Seas Treaty provides an international legal framework for the conservation and sustainable use of marine biodiversity. Integrated Coastal Zone Management (ICZM) provides a broader framework for balancing conservation and sustainable use in coastal areas, while restoration measures for particular coastal and marine habitats are discussed in articles listed in Marine habitats and ecosystems.