project II
project I

project II

project III

project IV

project V

project VI

project VII

project VIII

project IX

project X

current vacancies


project II: measurement and modelling of chemical and biological response of aquatic ecosystems to changes in Ontario hydro’s sulphur emissions

Project II is divided into 3 components - measurement and modelling of the chemical response of a set of lakes, their tributaries and groundwater in one or two representative watersheds, measurement of biological effects using simple indicators, and assessment of the changes in trace contaminant deposition, particularly mercury, related to fossil fuel use.

project IIa: chemical effects
Sulphate and base cation (calcium, magnesium, sodium, potassium) concentrations in lakes may increase while pH, alkalinity and DOC may decrease as a result of the expected increase in S and N emissions in the next several years. Statistical analysis will be used to define the minimal sampling effort needed to detect a specified change in each parameter that is considered of environmental significance. In the regions where impacts are expected to be the greatest, monitoring of a suite of chemical parameters will be carried out at 20 surface water stations (lakes and streams) and 5 ground-water sites. The basic chemical parameters will be supplemented with measurements of trace metals and other elements as identified during Project I. These measurements will be made during the ice-free season for five years. This will permit a test of the hypothesis that the effects of the increase in sulphur and nitrogen emissions will be increases in lake, stream and groundwater sulphate and base cation concentrations, and decreases in pH, DOC and alkalinity. The data will also be used to test models that link lake and watershed processes (Cosby et al. 1985, Kirchner et al. 1992, 1993) describing the chemical response to changing deposition. However, since it will take a substantial period of time,typically 5 to 15 years, for most aquatic ecosystems to reach a new steady state with respect to a change in the atmospheric deposition they receive, only the first stage of the effects of Ontario Hydro’s emissions can be evaluated in 5 years. Similarly, any improvements that may materialize following a subsequent decrease in emissions after this 5-year period will not be picked up with this relatively short-term monitoring programme. The option of continuing these measurements for an additional period of 5 years to assess more accurately both the negative and the beneficial effects of these emission changes can be considered at a later date.

project IIb: biological effects
To evaluate the impact of changes in acid deposition rates, biological assessments, in addition to chemical assessments, are important because small changes in water chemistry can have a substantial impact on some aquatic biota (Keller et al. 1992). Benthic micro- and macro-invertebrates (e.g. crayfish, caddis flies, mayflies and stone flies) are useful for these assessments because they are among the most sensitive organisms, they can be used as biological indicators of acid deposition-induced damage, and they are also good indicators of recovery following a subsequent improvement in water quality. Some historical data describing populations of these organisms at the core study sites are available. For example, information describing crayfish species presence and catch per unit effort is available for periods ranging from 5 to 8 years (Somers et al. 1996, David et al. 1997). Benthic invertebrate communities have been characterized in many of the same lakes over a shorter time period, typically 3-5 years (Reid et al. 1995, 1997) using a relatively new sampling protocol called "rapid bioassessment". This methodology is cost- and time-effective, yet can yield valuable information about the effects of changes in levels of anthropogenic stresses.

The hypothesis that will be tested is that the increase in sulphur and nitrogen deposition resulting from increased emissions and the subsequent changes in lake water chemistry will result in declines in the indicator organisms. A series of measurements using the rapid bioassessment protocol will be made to re-evaluate the current status of these invertebrate populations and to trace their response to the changes in acid deposition rates that occur over the period of this study. These measurements will be made annually for a minimum of three years. Combined with the existing data, a long-term record of an important and sensitive biological community will be available, allowing an evaluation of the effects of changing deposition.

project IIc: mercury deposition and uptake
For many years, there have been concerns about the bioaccumulation of mercury in fish and other aquatic organisms in much of eastern North America, and the subsequent risk to consumers including humans and wildlife such as waterfowl, mink and otters. Atmospheric mercury (Hg) deposition in southern Ontario was measured for several years in the late 1980’s and early 1990’s as part of an effort to quantify sources and fluxes into and out of lakes (Mierle 1990). Over the time period when these measurements were made, Ontario Hydro’s sulphur emissions declined substantially; mercury emissions likely followed the same pattern, but the data were too limited to assess whether this resulted in a change in mercury deposition. Ontario Hydro’s mercury emissions currently are estimated to be ca. 20% of all mercury emissions in the province (Sang and Lourie 1995), and may increase to two and a half times their current level in proportion to the expected increase in acid emissions. The atmospheric pool of mercury, however, is large and long-range transport from distant sources plays a major role, which may make measurement of any increase in mercury deposition difficult. Nevertheless, it will be useful to measure mercury deposition during the period when sulphur and nitrogen, and presumably mercury, emissions increase because of the current intense interest in its bioaccumulation.

The hypothesis that will be tested is that atmospheric deposition of methyl mercury (the most important species toxicologically) and total mercury will be greater in the period of this study than is was in the 1980’s and early 1990’s (Mason et al. 1997). It is also proposed to test whether small changes in mercury concentration combined with the expected changes in lake water chemistry (pH, sulphate, DOC, etc.) will result in changes in mercury speciation that lead to changes in bioavailability (Hintelmann et al. 1997). A series of measurements will be made to determine bioavailability and sub-lethal toxicity of mercury (and possibly other trace metals, depending on the results of Project I) to benthic invertebrates (the selection will be based on those studied in Project IIc). Because the anticipated changes in concentration and speciation of mercury are small, sensitive stable isotope tracer techniques using ICP-MS will be used to measure uptake (Hintelmann and Evans 1997). These measurements will be made sequentially on different species over the course of the study period.