B. R. Niederlehner

A proposed framework for developing indicators of ecosystem health

Considerations involved in developing a suite of indicators to monitor regional environmental health, similar in conception to management use of ‘leading economic indicators’, are described. Linkages between human activities and well being and the state of the environment are considered essential to the evaluation of general environmental health. Biogeochemical and socioeconomic indicators are mutually affected by environmental degradation and examples of both categories of indicators are described. Desirable properties in indicators of environmental health vary with their specific management use. Different indicators are called for when collecting data to assess the adequacy of the environment, monitor trends over time, provide early warning of environmental degradation, or diagnose the cause of an existing problem. Tradeoffs between desirable characteristics, costs, and quality of information are inevitable when choosing indicators for management use. Decisions about what information to collect for which purpose can be made more rationally when available indicators are characterized and matched to management goals.

Effects of atrazine on freshwater microbial communities.

A multispecies toxicity test system using naturally derived microbial communities on polyurethane foam substrates was used to evaluate the toxic effects of the herbicide atrazine. Both structural (e.g., protozoan species number, biomass) and functional (e.g., colonization rate, oxygen production) community responses were measured. Oxygen production and the ability of communities to sequester magnesium and calcium were the most sensitive measures of toxic stress due to atrazine (maximum allowable toxicant concentrations [MATCs]=17.9 μg/L). Dissolved oxygen was 33% lower, and there was 15% less calcium and magnesium in communities at and above 32.0 μg/L atrazine compared to controls. Species richness and estimates of biomass (total protein and chlorophyll a) were less sensitive (MATCs=193) to atrazine. At the highest atrazine concentration (337 μg/L), species numbers were 30% lower than controls, and protein and chlorophyll a content of communities were reduced by 38 and 91%, respectively. Low levels of atrazine (3.2–32.0 μg/L) resulted in a 46% increase in species numbers and a greater concentration of total protein and chlorophyll a (41 and 57%, respectively). Results compared well with other estimates of chronic toxicity for effects of atrazine on aquatic communities. Reported MATCs ranged from 70.7 to 3,400 μg/L. The results from this test emphasize the importance of monitoring both structural and functional measures of community integrity in toxicity testing with multispecies.

Problems associated with selecting the most sensitive species for toxicity testing

When the field of aquatic toxicity testing began its first major expansion about 40 years ago, it was uncommon to use more than one test species (usually a fish). Later, it became customary to use individual microorganisms (usually algae) and macroinvertebrates as well. Most attention was then given to the response of the most sensitive species in that test series when calculating the ‘biologically safe’ concentration acceptable for use in natural systems. However, in recent years, there has been an attempt to equate the most sensitive species in a laboratory test series to the most sensitive species in natural systems. Since laboratory test species represent only a tiny part of natural systems and since response variability is well established, that can be a dangerous assumption. The purpose of this discussion is to re-examine the scientific support for this practice.

Developing a Field of Landscape Ecotoxicology

Since toxicants are spread over ecological landscapes, it seems likely that they have effects at that level of ecological organization. Landscape ecotoxicology examines the effects of toxic chemicals on larger scales than traditional environmental toxicology. This approach is characterized by the use of endpoints appropriate to the spatial scale across which a toxicant is dispersed, attention to interactions between physical and temporal patterns and the process of ecological impairment, and integration of multiple lines of evidence for toxicity at various scales. In addition, landscape ecotoxicology seeks predictive models in order to influence human actions before environmental damage occurs. Integrating information from damaged systems, toxicity tests, simulation models, and biomonitoring of healthy systems provides the best basis for decisions. Rapid progress in landscape ecotoxicology is expected as scientists incorporate tools, such as remote sensing and spatially explicit simulation models, and then calibrate these models using data from long-term biomonitoring of large areas. Further integration into combined socio-economic-ecological models is also possible.

Use of grass shrimp in toxicity tests

The literature pertaining to the use of grass shrimp in toxicity testing is reviewed. Information on the life history, species differences, collection, culture, handling, effects of toxicants, standard methods for toxicity testing, and potential problems in experimental design is presented. Suggestions for future research are made.

Evaluation of joint toxicity of chlorine and ammonia to aquatic communities

Abstract Periphytic communities on artificial substrates were exposed to chlorine and ammonia, alone and in combinations. The species richness of protozoans decreased with increasing toxicant concentrations. Species richness was reduced by 20% in 2.7 μg/l chlorine, 15.4 μg/l un-ionized ammonia, and a combination of 1.2 μg/l chlorine and 16.8 μg/l ammonia. Interaction between toxicants was significant and effects of mixtures were less-than-additive, especially at higher concentrations. Multiple regression was used to derive a response surface model accounting for 73.4% of the variation in species richness. Algal biomass and community metabolism measures were less sensitive to stress and showed different patterns of joint action.

A simple, cost-effective multispecies toxicity test using organisms with a cosmopolitan distribution

Difficulties in making accurate, ecosystem-level predictions of environmental effects of chemicals, mixtures, and effluents based solely on the results of tests on single species have necessitated the development of more environmentally realistic, predictive testing methods. This paper describes a multispecies, community-level toxicity test based on the colonization of artificial substrates by microbial species. Tests examined the colonization of initially barren polyurethane foam artificial substrates by Protozoa from a species source colonized in a natural system. Differences in colonization were examined in microecosystems amended with low levels of cadmium, a very toxic heavy metal, and TFM, an organic biocide used against larval sea lamprey. Tests examined differences in colonization over 28 days. For cadmium, effect levels were estimated to be near 1 μg 1−1, in the low range of effect levels determined from chronic single species tests. For TFM, effect levels were estimated to be between 1 and 10 ppm, overlapping the concentrations used in environmental applications. The colonization response, which depends on naked microbial cells reproducing and migrating through toxicant amended water to new substrates, is very sensitive. Tests based on colonization can be adapted to use species from a target receiving system or can use species from a designated natural source. Field validation of these tests can employ nearly identical methods to those used in laboratory studies to assess the accuracy of predictions based on test system data.

Estimating ecotoxicological risk and impact using indigenous aquatic microbial communities

Emphasis has increased on accuracy in predicting the effect that anthropogenic stress has on natural ecosystems. Although toxicity tests low in environmental realism, such as standardized single species procedures, have been useful in providing a certain degree of protection to human health and the environment, the accuracy of such tests for predicting the effects of anthropogenic activities on complex ecosystems is questionable. The use of indigenous communities of microorganisms to assess the hazard of toxicants in aquatic ecosystems has many advantages. Theoretical and practical aspects of microbial community tests are discussed, particularly in related to widely cited problems in the use of multispecies test systems for predicting hazard. Further standardization of testing protocols using microbial colonization dynamics is advocated on the basis of previous studies, which have shown these parameters to be useful in assessing risk and impact of hazardous substances in aquatic ecosystems.

Field evaluation of predictions of environmental effects from a multispecies-microcosm toxicity test

The predictive validity of a multispecies-microcosm toxicity test was evaluated. Predictions of biological response to a complex effluent were made from dose-response curves in laboratory tests and compared to observed effects in the receiving system. No effects on protozoan or macroinvertebrate communities were observed at the field site with effluent concentrations less than the chronic value of 1.7% effluent determined in laboratory tests. In addition, the microcosm test accurately predicted the magnitude of decreases in species richness in protozoan and macroinvertebrate communities in the receiving system at the first downstream site. Predictions of environmental effects for stations farther downstream were generally less accurate and too high, perhaps due to lack of persistence in the toxicity of the effluent. Stimulation of total biomass and algal growth were observed in both laboratory and field tests, but laboratory tests greatly overestimated the magnitude of enrichment responses in the receiving system.

Effects of ammonia on periphytic communities.

Laboratory tests were conducted to evaluate the chronic effects of ammonia on periphytic communities. Species richness of the protozoan component of these communities was affected at un-ionized ammonia concentrations of </= 0.01 mg NH3 litre(-1). A biologically important concentration was defined as the concentration of ammonia affecting 20% of species and was estimated from a concentration-response regression as 0.011 mg litre(-1). A comparable value based on literature reports of chronic toxicity to fish and invertebrates was 0.0126 mg litre(-1). Other non-taxonomic responses were equally sensitive to ammonia. Biomass (ash-free dry weight) and algal biomass (in vivo fluorescence) were significantly reduced even at the lowest tested ammonia treatment, 0.01 mg litre(-1), but the abundance of bacteria was reduced only in the highest treatment group, 0.43 mg litre(-1). Net community metabolism was reduced in all ammonia treatments. Periphyton communities were affected at levels below the USEPA chronic criterion of 0.027 mg litre(-1) (temperature = 8.8 degrees C and pH = 8.1). Successional maturity or age of the periphytic community affected the amount of biomass and algal biomass, but did not modify sensitivity to ammonia.