Index of Biological Integrity
What is an Index of Biological Integrity (IBI)?
An index of biological integrity (IBI)
is a method of assessing the health of a water body. An IBI
is made of combining several
biological indicators, called metrics,
into a summary index. The summary can then be used to measure the condition
of a water body as well as diagnose the type of stressors
damaging the organisms living in the water. Measuring
the biota (organisms) within a water body provides
a good assessment of resource condition because the characteristics of the
biota reflect the degree of human influence in the surrounding
watershed. This information
can then be used to minimize the negative impacts and improve the health
of the water and the surrounding habitat.
Benthic
macroinvertebrates (bottom-dwelling) are most commonly used
because they are an important part of a river or stream habitat
and
directly
reflect the broad range of physical, chemical, and biological conditions that
make up its health. For instance, some benthic macroinvertebrates are found
only in water that is generally very clean and unpolluted by organic wastes.
These benthic macroinvertebrates need high levels of oxygen, which is available
to them only in streams and rivers with high water quality. Other factors may
inhibit the growth or survival of certain macroinvertebrates including toxic
chemicals, nutrients and habitat quality. Other assemblages that are used to
develop an IBI include algae, bacteria, fish and other invertebrates.
IBIs are useful tools for volunteer
water quality monitoring at New England
Land Grant Universities. Volunteers need minimal equipment
and
once trained,
identification of
benthic macroinvertebrates to major group level and calculation of relative
abundance is easy. IBI training for volunteer watershed monitoring groups in New England is available
through New
England Regional Monitoring Collaborative.
University of Vermont researchers are examining macroinvertebrates
that may be sensitive to agricultural specific runoff to improve
the use of biological indices. The
outcome of this study will be improved knowledge of watershed
health in agriculturally influenced areas. It also will support
more informed selection and use of indicators in the future
water quality monitoring programs.