Journal of Aquatic Ecosystem Health

Due to a fast decline in the ecological quality of watercourses combined with the threat of human functions, policy makers started to legislate water quality objectives for watercourses and to set up water purification programs. The description of universal quality objectives is too limited as a frame of reference and a policy only based on water quality cannot guarantee the goals of river restoration as a whole. In most countries the need for a more integrated approach of water management is growing. Water quantity must be managed together with water quality, surface water with groundwater, and the water economy with town and country planning. To restore and maintain the natural diversity of watercourses, together with the natural species richness, policy makers need a frame of reference based on the natural functioning of the ecosystem. The highest level of reference is called the ‘ecological naturalness’. Based on the present and the potential ecological value and on the intensity of human uses, policy makers together with a group of scientists should decide on the ecological quality objectives of watercourses. The lowest quality level that must be reached in all watercourses can be described as the ‘ecological basic quality’. Together with a frame of reference, there is a need for a refined ecological evaluation method for ecological quality as a whole, and especially to evaluate ‘potential ecological values’ in an objective way.

Ecological risk assessments provide a probabilitistic approach to analyzing and predicting ecosystem responses to stress. We are evaluating the relationship between nonpoint source (NPS) phosphorus loading and the trophic status of the aquatic ecosystem. We are using SIMPLE (the Spatially Integrated Model for Phosphorus Loading and Erosion) to identify probable phosphorus sources in a watershed, simulate the phosphorus loading to streams, and analyze the relationships between input variables and their ecological impact. The objective of this paper is to describe a risk-based paradigm using SIMPLE to characterize the probability of exceeding a critical phosphorus loading to a lotic ecosystem. We have characterized the risk of exceeding a threshold loading of 0.5 kilogram total phosphorus per hectare per year from a 2238 hectare watershed. Two-hundred-fifty random SIMPLE simulations were performed to estimate annual total phosphorus, dissolved phosphorus, and sediment-bound phosphorus loading to a lotic ecosystem from the watershed. Simulation results were analyzed statistically to determine the probabilities of exceeding the critical loadings. Based on the current land use practices in the Battle Creek watershed, the probability of exceeding the total phosphorus critical loading rate of 0.5 kg/ha/yr was approximately 11 percent, or one year in nine the total annual loading will exceed the critical loading rate. The 95 percent confidence intervals for the total phosphorus loading occurring on average once in nine years were relatively close (0.45 to 0.60 kg/ha/yr), assuming the only variability from year to year was due to natural variability in weather.

The current recognition that chemical measurements are uncertain indicators of biological consequences of pollution has shifted the emphasis away from assessing environmental chemistry alone toward the inclusion of measurements of the health of organisms. Effects of pollutants begin with the individual, have subsequent repercussions on population level processes, and ramifications for community structure and functions. Pollutants act at a molecular level and the biochemical lesions is the first step in the manifestation of effects. Technologies that operate at the cellular level assist in elucidating toxicity. Higher levels of integration include an organism's capacity for growth. Laboratory bioassays andin situ research can monitor physiological incapacities and assist in predicting population level effects. A yet higher level of organization is that of the ecological community.

Automated biomonitors operate on a real-time basis and utilize living organisms as the sensors. Traditionally, chemical monitors have been used to assess water quality. However, biological monitors respond to a greater number of toxic conditions. An overview of the various automated biomonitors, assessed by the types of biological sensors employed, is presented. The sensors used include bacteria, algae, invertebrates, and fish. Of all the systems, those monitoring the ventilatory behavior of fish have evolved the furthest with respect to their research, development, commercial availability, and field testing.

The Canada — U.S. Great Lakes Water Quality Agreement defines Areas of Concern as geographic areas that fail to meet the general or specific objectives of the Great Lakes Water Quality Agreement where such failure has caused or is likely to cause impairment of beneficial use or the area's ability to support aquatic life. Impairment of beneficial use is defined by the Agreement as a change in the physical, chemical or biological integrity sufficient to cause any one of 14 designated use impairments. In 1987 the International Joint Commission's Great Lakes Water Quality Board (GLWQB) recommended that criteria be developed to determine when ecosystem conditions have been impacted enough to warrant designation as an Area of Concern and when conditions have improved sufficiently to be delisted. Based on scientific input and policy considerations, the GLWQB adopted, in principle, a set of quantitative and qualitative listing/delisting criteria for each of the 14 use impairments. These criteria can be uniformly applied throughout the basin. Further, the GLWQB recommended future refinement of these criteria based on advances in science and public input.

We provide further insight into the reproductive ecology and spawning requirements of lake trout. New comparative information about substrate characteristics, sediment transport, quality of interstitial water at spawning substrates, and the role of temperature in site selection and time of spawning is given for lakes Simcoe and Manitou (Ontario) and Seneca Lake (New York). Spawning lake trout commonly use stable lag deposits derived from glacial sediments, or relict features such as fans, bars or submerged talus slopes. Artificial breakwaters of broken material may also provide suitable substrates. Optimal particle sizes range from 4 to 10 cm diameter but larger materials to 30 cm are also successfully utilized for spawning. The transport of finer particulates by wind generated water movements may limit the suitability of some substrates and successful spawning sites are usually remote from depositional effects. Successful embryo development is associated with low nutrient conditions, with high dissolved oxygen (>7 mg L-1) and with low un-ionized ammonia (<12.5 μg L-1) in the interstitial water of spawning substrates. Shallow-water spawning appears to be the common strategy of colonizing lake trout. Some deepwater spawning in the Great Lakes may reflect initial colonization in shallow-water and adaptation to later increases in water level, but some may also reflect unique behavioural and physiological adaptations. Temperature is an important cue, and many wild and hatchery stocks spawn at 8 to 13 °C with latitudinal shifts in the actual time of spawning. These requirements are summarized as a dichotomous key for evaluation of approaches to restoration of lost or damaged lake trout stocks.

As part of an ecological risk assessment casestudy at the Portsmouth Naval Shipyard (PNS), Kittery,Maine, USA, the population level effects of leadexposure to purple sea urchin, Arbaciapunctulata, were investigated using a stage-classifiedmatrix population model. The model divided the lifehistory of A. punctulata into five classes,incorporating both, the developmental stages of thisspecies and the endpoints from a laboratory bioassay. Finite population growth rate (λ) was themetric relating population level impact to leadexposure. An inverse relationship was observed betweenlead tissue residues in A. punctulata andλ. Bioassay treatments which resulted insignificant impacts on fertilization success and zygoteviability did not translate into significant effects onλ, unless those treatments also negativelyimpacted adult survival. These results paralleled theelasticity (relative sensitivity) analysis of themodel, which indicated that λ was mostsensitive to adult and subadult survival and wasrelatively insensitive to fecundity, fertilizationsuccess, or zygote survival. Model results indicatedthat the environmental lead levels observed at PNSshould not pose significant ecological risk to seaurchin populations. Additionally, the model resultsindicated that impacts to the early life stagesroutinely used in toxicity testing do not necessarilytranslate directly into impacts at the populationlevel.