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Water: Monitoring & Assessment

Appendix A. Summary of Advantages and Disadvantages of Use of Major Taxa in Monitoring Wetland Ecological Condition

Impacts on Quality of Inland Wetlands of the United States:
A Survey of Indicators, Techniques, and Applications of Community Level Biomonitoring Data
Excerpts from Report #EPA/600/3-90/073
(now out of print)

Microbial Communities

ADVANTAGES

  • tight linkage to fundamental processes (eg, decomposition, denitrification, respiration)

  • samples easily collected, transported, and analyzed

  • some taxa linked to animal welfare (eg, streptococci)

  • EPA protocols available

  • immediate response to contamination

  • measurable in wetlands which lack surface water

  • sensitive to presence of some contaminants (eg, Ames test, Microtox test)

  • "indicator taxa" relatively well-known (especially protozoans)

  • some culture bioassay data are available

DISADVANTAGES

  • response is often not identifiably stressor-specific

  • laborious and slow (plate culture) identification; process measurements difficult to interpret with regard to ecological significance

  • general absence of existing regional field databases

  • rapid turnover requires frequent sampling; do not integrate conditions over time very well

  • naturally great micro-spatial variation, especially in tidal wetlands

  • drifting cells in riverine wetlands complicate interpretation

  • low social recognition of their importance

  • bioaccumulation is irrelevant and impractical to detect

Algae

ADVANTAGES

  • tight linkage to fundamental processes (eg, photosynthesis, respiration)

  • pivotal relationships in food webs

  • EPA protocols available (may need modification to wetlands)

  • measurable in some wetlands which lack surface water

  • tolerances and indicator value are relatively well-known, particularly to nutrients, and most are very sensitive to herbicides

  • simple collection procedures with minimal wetland impact

  • response to stressors is usually immediate

  • generally immobile and thus reflective of site conditions, useful for in situ exposure assessments and whole-effluent bioassays

DISADVANTAGES

  • response is often not identifiably stressor-specific

  • laborious identification

  • some regional field databases exist, but not for wetlands

  • rapid turnover requires frequent sampling

  • cannot be effectively sampled during dormant season

  • low social recognition of their importance

  • bioaccumulation is unmeasurable

  • drifting cells of unattached species complicate interpretation

  • most relatively insensitive to heavy metals and pesticides (Hellawell 1986)

Mosses, Liverworts, Ferns

ADVANTAGES

  • a few taxa are reputed indicator species for physicochemical contaminants

  • perhaps the most sensitive indicator of hydric regimes

  • the only integrator of the long-term geologic record (ie, peat core analyses for metals accumulation, land cover change, ground water flow reversals)

  • immobile and thus reflective of site conditions, useful for in situ exposure assessments

DISADVANTAGES

  • response is often not identifiably stressor-specific

  • laborious sampling and identification

  • low social recognition of their importance

  • few regional field databases exist

Submersed Aquatic Vascular Plants

ADVANTAGES

  • extremely sensitive to turbidity, eutrophication, hydroperiod

  • sensitivities of several indicator species are well known

  • relatively important in food webs (eg, waterfowl)

  • immobile and thus reflective of site conditions, useful for in situ exposure assessments

  • patterns interpretable using remote sensing

DISADVANTAGES

  • difficult to sample systematically throughout a wetland

  • cannot be effectively sampled during dormant season

  • absent from wetlands that lack standing water (eg, bogs)

  • tolerant of intermittent pollution

  • laborious identification

  • low social recognition of their importance

  • few regional field databases exist

Non-rooted Aquatic Vascular Plants

ADVANTAGES

  • extremely sensitive to nutrient additions

  • sensitivities of some indicator species (eg, Lemna) are well known

  • important in food webs (eg, waterfowl)

  • mostly immobile and thus reflective of site conditions, useful for in situ exposure assessments

  • patterns sometimes interpretable using remote sensing

DISADVANTAGES

  • difficult to sample systematically throughout a wetland

  • limited bioaccumulation due to short lifespan

  • absent from wetlands that lack standing water (eg, bogs)

  • laborious identification

  • low social recognition of their importance

  • few regional field databases exist

  • cannot be effectively sampled during dormant season

Emergent (Herbaceous) Vascular Plants

ADVANTAGES

  • occur in virtually all wetlands

  • sensitivities of some indicator species (eg, Typha, Phragmites, Phalaris) to nutrients/sediment are well known

  • immobile and thus reflective of site conditions, useful for in situ exposure assessments

  • bioaccumulate to a moderate degree

  • patterns interpretable using remote sensing

  • sampling techniques and community metrics well-developed

  • moderately sensitive to nutrients and hydroperiod alteration

  • some regional field databases exist

DISADVANTAGES

  • not highly sensitive to contaminants and sedimentation

  • lagged response to stressors (episodic contamination may not be reflected)

  • low social recognition of importance

  • sampling and identification is laborious

  • community cannot be completely characterized during the dormant season

  • dispersal, herbivory, soil type and other factors often overshadow contaminant effects

Forested/Shrub (Woody) Vascular Plants

ADVANTAGES

  • occur widely

  • sensitivities of many species to hydroperiod change are relatively well known

  • immobile and thus reflective of site conditions

  • bioaccumulate to a moderate degree

  • patterns interpretable using remote sensing

  • sampling techniques and community metrics well-developed

  • some regional field databases exist

  • trends can be inferred (with care) using tree ring analyses

  • signs of stress (eg, die-offs) are socially recognized

  • sampling and identification are fairly easy

  • community can be characterized even in the dormant season

DISADVANTAGES

  • not highly reflective of contaminants and sedimentation

  • long lagged response to stressors (episodic contamination may not be reflected); in situ experimentation is impractical

  • response difficult to interpret where past management (eg, silviculture) has been practiced

Aquatic Insects (eg, dragonflies, midges)

ADVANTAGES

  • occur in all wetland types, even those lacking surface water

  • community metrics/indices well-developed (eg, Index of Biotic Integrity) but may need adaptation for wetlands

  • intermediate lifespans reflect episodic events without requiring extremely frequent sampling

  • bioaccumulate to a moderate degree

  • can be caged for whole-effluent bioassays or in situ assessments

  • relatively important in food webs

  • community can usually be sampled year-round

  • some regional field databases exist, though few for wetlands

  • show characteristic response to all major wetland stressors (hydroperiod, sediment, nutrients, contaminants)

  • some taxa linked to human welfare (eg, mosquitoes)

  • EPA sampling protocols available, but need modification for wetlands

  • contaminants may induce identifiable deformities

DISADVANTAGES

  • occurrence in isolated wetlands may be strongly tied to sources of colonizers and their dispersal mechanisms

  • sampling difficult and true densities very difficult to determine in wetlands with herbaceous vegetation

  • laborious identification

  • low social recognition of their importance

  • naturally great micro-spatial variation

  • community composition potentially affected by selective predation (eg, by fish, waterfowl)

Benthic/Epiphytic Macro-crustaceans (eg, amphipods, crayfish, oligochaetes, isopods)

ADVANTAGES

  • less subject to dispersal than aquatic insects (and thus more reflective of conditions in a particular wetland)

  • may be more sensitive than aquatic insects to contaminants

  • fairly simple sampling and identification

  • social recognition of some species (eg, crayfish, sandworms)

  • other advantages --- similar to Aquatic Insects, above

DISADVANTAGES

  • mostly absent from wetlands which lack standing water

  • naturally great micro-spatial variation

  • community composition potentially affected by selective predation (eg, by fish, waterfowl)

Mollusks

ADVANTAGES

  • highly immobile and thus most reflective of site conditions, useful for in situ exposure assessments

  • highly bioaccumulative (eg, clams, mussels)

  • depuration procedures can indicate potential contaminant uptake rates

  • bioassay data fairly extensive

  • contaminants may induce identifiable deformities

  • can be sampled year-round

  • historic recreation of growth is possible (with care)

  • presumptive indicator of hydroperiod (complete, sustained wetland drawdown)

  • EPA protocols available

  • high social importance of coastal species (shellfish)

DISADVANTAGES

  • very localized occurrence, related largely to dissolved solids rather than contaminants

  • laborious sampling and (in freshwater) identification

Fish

ADVANTAGES

  • community metrics well-developed (Index of Biotic Integrity), though not for wetlands; many reputed indicators (eg, carp)

  • most comprehensive set of bioassay data

  • can be caged for whole effluent bioassay and in situ studies, or avoidance measured using radiotelemetry

  • moderately bioaccumulative

  • fairly simple identification (except larval stages)

  • population characteristics, growth fairly easy to discern

  • contaminants may induce identifiable deformities

  • can be sampled year-round

  • presumptive indicator of hydroperiod (absent from isolated wetlands with complete, sustained drawdown)

  • EPA protocols available

  • integrate broad, longer-term, landscape-level impacts because of their mobility, high trophic position, and longer life span

  • high social importance of most species; existing water quality standards for aquatic life focus on fish

DISADVANTAGES

  • mobility makes it difficult to locate specific contaminant sources

  • absent (or present for only brief periods) in most wetlands

  • laborious sampling

  • early life stages and non-game species may be difficult to identify

Amphibians and Reptiles

ADVANTAGES

  • small home range relative to larger vertebrates

  • highly (eg, snapping turtle, alligator) to moderately bioaccumulative; can be caged for in situ assessments

  • some social recognition

  • fairly simple identification

  • fairly well-established sampling protocols

  • sensitive to hydroperiod alteration

  • present in most inland wetland types

DISADVANTAGES

  • sampling limited to certain seasons in some regions

  • mostly absent from tidal wetlands

  • sampling can be laborious

  • presence can be strongly influenced by natural dispersal conditions

Birds

ADVANTAGES

  • high social recognition, particularly waterfowl

  • have the only relatively extensive nationwide databases on trends, habitat needs, distribution

  • moderately extensive bioassay data

  • some species (eg, wading birds, harrier) are highly bioaccumulative

  • avoidance is measurable using radiotelemetry, and in situ assessments are possible (caged or clipped individuals)

  • simple sampling and identification

  • present in all wetland types

  • established sampling protocols are available

  • the only suitable indicator of degradation occurring at the landscape scale

DISADVANTAGES

  • in general, community structure is highly controlled by physical habitat, and perhaps hunting mortality, rather than contaminants

  • mobility makes it difficult to locate specific causes of mortality sources (could be thousands of miles away)

  • essentially absent from some wetlands in winter

Mammals

ADVANTAGES

  • many (eg, otter) are highly bioaccumulative

  • high social recognition and value (eg, muskrat)

  • avoidance is measurable using radiotelemetry, and in situ assessments are possible (caged individuals)

  • fairly simple sampling and identification

  • some sign (eg, beaver dams) can be remotely sensed

  • present in all wetland types

  • established sampling protocols are available

  • an extensive database of acute toxicity data for mice/rats may be partially transferable

DISADVANTAGES

  • great temporal and spatial variation (many species are cyclic) makes data interpretation difficult

  • in general, community structure is highly controlled by physical habitat, and perhaps trapping mortality, rather than contaminants

  • mobility (and frequent use of non-wetland habitat) makes it difficult to locate specific causes of mortality sources

Biological Processes (Functions)

Definition: Whole-wetland measurement of photosynthesis, primary productivity, respiration, denitrification, nitrogen fixation, decomposition, leaching, and/or similar processes

ADVANTAGES

  • most important indicators of wetland sustainability and life support function

DISADVANTAGES

  • not as sensitive to contamination as is community structure or tissue analysis (Schindler 1987)

  • measurement is laborious, time-consuming (eg, isotopes)

  • social recognition of importance is weak

  • extreme spatial and temporal variation

  • measured values may reflect natural successional stage rather than human-induced stress


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