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2 Functions and benefits of aquatic ecosystems
Aquatic ecosystems are numerous and diverse and they also provide several roles and
functions, benefiting tomankind. This chapter briefly describes their composition and
functioning, theways to characterise them but also their functions to related services.
2.1Role and functions of aquatic ecosystems (rivers, lakes&wetlands)
2.1.1 Varied ecosystems involving constant exchanges
Aquatic ecosystems are a subset of ecosystems (see definition in Introduction) inwhichwater
is a key component. Awide variety of aquatic ecosystems exist, and although they represent a
low percentage of the Earth’s surface, their roles and functionsmake them crucial.
Wewill focus here on inland surfacewater aquatic ecosystems. Threemain types can be
distinguished:
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Rivers, wherewater flows from source tomouth;
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Lakes, in the broad sense from small ponds to large lakeswherewater is stored according
to the specific landscape and topography;
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Wetlands directly depending on aquatic ecosystems. The Ramsar Convention gives awide
definition of wetlands - “Areas of marshes, fen, peatland or water, whether natural or
artificial, permanent or temporary, withwater that is flowing or static, fresh, brackish or
salty, including areas of marinewater the depth of which at low tide does not exceed six
metres.”We focus here on inlandwetlands.
More specifically, rivers, lakes andwetlands are complex systems that contain a richly
diversity of living species that interact in variedways by establishing relationships of
cohabitation, competition, predation and parasitism. These species cannot survive on their
own. To grow, they need energy and food, which they obtain from the outside environment
comprisingwater, soil and atmosphere.
The composition of these populations therefore depends closely on the living conditions
available to them, such as thewater’s current and depth, the temperature, oxygenation and
chemical composition of thewater, the nature of the beds, landform and vegetation of the
catchment area, atmospheric conditions, etc. Conversely, thewater’s chemical composition is
constantlymodified by the living species present in the environment, especially themineral
and dissolved gas content.
Thus, biological species live in close interdependence andwith their surrounding physical
environment. Themultiple exchanges of energy andmatter constitute a delicate balance to
maintain.
2FUNCTIONSANDBENEFITSOFAQUATICECOSYSTEMS
THEHANDBOOK FORMANAGEMENT
ANDRESTORATIONOF AQUATIC ECOSYSTEMS INRIVERAND LAKE BASINS
KEYPOINTS:
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An aquatic ecosystem in good condition can carry out diverse functions:
production, regulation and organization.
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Ecosystem services are provisioning, regulatory, cultural and support
services.
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Human action and activities often disturb the structure of the biotope, and
cause organic pollution.
