Chapter 02 · Nature, land & waterBiodiversity & Nature
Aquatic ecosystem
Definition
A community of organisms interacting with each other and with a water-based environment. Aquatic ecosystems divide broadly into freshwater systems — standing (lentic) waters such as lakes and ponds, and flowing (lotic) waters such as rivers and streams, plus wetlands — and marine systems, which cover most of the biosphere.
References
Freshwater/marine division; lentic, lotic and wetland types; 3% of net primary production and 41% of fish species in freshwater; ecosystem functions.
Overview
What it means
Though freshwater bodies hold only a small fraction of Earth's water, they contain a disproportionate share of biodiversity — freshwater ecosystems generate nearly 3% of net primary production and contain about 41% of known fish species. Aquatic systems recycle nutrients, attenuate floods, regulate climate and supply food and water to human societies.
How it is used
The term structures environmental assessment and management: water quality standards, protected-area design, fisheries management and freshwater biodiversity monitoring are all organised around aquatic ecosystem types. Corporate water and nature disclosures increasingly require site-level assessment of aquatic ecosystem condition.
Why it matters
Aquatic ecosystems are among the most threatened on Earth — freshwater species populations have declined faster than terrestrial or marine ones — yet they underpin drinking water, food, flood control and carbon cycling. Their degradation propagates directly into human water and food security.