Environmental Engineering Reference
In-Depth Information
5.1
Levels of Biological Organization to Protect
Officials must decide what level of biological organization (defined in Table 5)
their water quality criteria are intended to protect. Several derivation methodologies
seek to protect individuals or species, expecting that by doing so, they will protect
ecosystems. Canada's guiding principles for the development of freshwater aquatic
life guidelines state that guidelines will consider all components of the ecosystem,
and will be “set at such values as to protect all forms of aquatic life and all aspects
of the aquatic life cycle” (CCME 1999). Similarly, the UK derives aquatic life
EQSs for the protection of all aquatic species. The Netherlands has the goal of
protecting all species in ecosystems from adverse effects (RIVM 2001).
Most of the reviewed methodologies specifically seek to protect aquatic eco-
systems. Water quality criteria in South Africa “allow for the sustainable functioning
of healthy and balanced aquatic ecosystems.” This is achieved by developing
criteria that are protective of representative key species from a variety of trophic
groups (Roux et al. 1996). France derives threshold levels that will maintain water's
suitability to support its biological function and other uses (Lepper 2002). The
USEPA criteria are intended to protect “aquatic organisms and their uses,” without
specifically aiming to protect ecosystems. However, the methodology states that eco-
systems can tolerate some stress and it is not necessary to protect all species at all
times (USEPA 1985). Arguing that this feature of the USEPA methodology (1985)
Table 5 Definitions for levels of biological organization
Level
Definition
Reference
Individual
A single organism
Webster's New Collegiate
Dictionary (1976)
Species
A taxonomic grouping of morphologically similar indi-
viduals who actually or potentially interbreed
Curtis and Barnes (1981)
Population
A group of individuals of one species that occupy a
given area at the same time
Curtis and Barnes (1981)
Community
All of the organisms inhabiting a common environ-
ment and interacting with one another
Curtis and Barnes (1981)
Ecosystem
All organisms in a community plus the associated
abiotic environmental factors with which they interact
Curtis and Barnes (1981)
Ecosystem
structure
The spatial and temporal relationships of biotic and
abiotic components that support energy flow and bio-
geochemical processes in an ecosystem
Curtis and Barnes (1981)
Ecosystem
function
The processes by which energy flows and materials
are cycled through an ecosystem
Curtis and Barnes (1981)
Ecosystem
engineer
Species that directly or indirectly modulates the
availability of resources to other species
Lawton (1994)
Keystone
species
Species whose removal from a community would
precipitate a further reduction in species diversity
or produce other significant changes in community
structure and dynamics
Daily et al. (1993)
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