Ann Kristin Schartau

Littoral Microcrustacean (Cladocera and Copepoda) Indicators of Acidification in Canadian Shield Lakes

Abstract We identify littoral microcrustacean indicators of acidification in 2 surveys of Canadian Shield lakes conducted 10 years apart. We found a total of 90 cladoceran and copepod species with richness increasing severalfold from acidic to nonacidic lakes. The fauna of the nonacidic lakes differed between the surveys. The 1987 survey employed activity traps, and caught more littoral taxa than the more recent, net-haul-based survey. Similar faunas were identified in the acidified lakes in both surveys, and several good indicator species were identified. For example, Acanthocycops vernalis was restricted to lakes with pH < 6. Sinobosmina sp. was very common but only in lakes with pH > 4.8. Tropocyclops extensus, Mesocyclops edax, and Sida crystallina were commonly found but only at pH > 5, and Chydorus faviformis only at pH > 5.9. These indicators showed promise in gauging the early stages of recovery from acidification in 3 lakes that were included in both surveys.

Metal and proton toxicity to lake zooplankton: A chemical speciation based modelling approach

The WHAM-FTOX model quantifies the combined toxic effects of protons and metal cations towards aquatic organisms through the toxicity function (FTOX), a linear combination of the products of organism-bound cation and a toxic potency coefficient for each cation. We describe the application of the model to predict an observable ecological field variable, species richness of pelagic lake crustacean zooplankton, studied with respect to either acidification or the impacts of metals from smelters. The fitted results give toxic potencies increasing in the order H(+) < Al < Cu < Zn < Ni. In general, observed species richness is lower than predicted, but in some instances agreement is close, and is rarely higher than predictions. The model predicts recovery in agreement with observations for three regions, namely Sudbury (Canada), Bohemian Forest (Czech Republic) and a subset of lakes across Norway, but fails to predict observed recovery from acidification in Adirondack lakes (USA).

Crustacean Communities in Canada and Norway: Comparison of Species along A pH Gradient

Increased pH in acid lakes changes the crustacean fauna from communities dominated by acid-tolerant species to communities dominated by more acid-sensitive species. Studies from Canada (Killarney) and southeastern Norway (Østfold county) have demonstrated that planktonic and littoral crustaceans can be used as indicators of such recoveries. In both places the cladocerans Alona rustica and Acantholeberis curvirostris were found in acidic lakes, whereas Alona costata and the copepod Eucyclops macrurus were found in near neutral lakes. The calanoids Diaptomus minutus in North America and Eudiaptomus gracilis in Europe, both dominate in acidic water, and may ecologically be equivalent species. Sometimes the same species occur at different pH in the two continents. Bosmina longirostris and Alonella excisa may serve as examples, but a pertinent question is whether or not they are really the same species.

Correlation between Microcrustaceans and Environmental Variables Along an Acidification Gradient in Sudbury, Canada

Multivariate methods were used to relate microcrustacean (pelagic and littoral) richness and composition (presence/absence) to water quality and other environmental variables. All acidification variables (pH, aluminium, ANC) snowed significant correlation with both species richness and composition. The variation in microcrustacean richness was best explained by the combination of dissolved organic carbon (DOC), fish species richness and lake area. Of 16 variables tested, pH showed strongest correlation with the main gradient in the crustacean composition explaining between 13 and 16% of the variance in the species data (CCA). pH, elevation, lake area, average depth, DOC., conductivity and fish species richness explained 30–54% of the total variance. Stronger correlation was obtained between species composition and environmental data in analyses which included the between-year differences than analyses based on the cumulative species records. Analyses based on the pelagic species exclusively gave similarly stronger correlation than analyses based on all crustacean species. Small changes in the species composition during the three years of study may be an indication of recovery of microcrustaceans in Killarney lakes.

Low Success Rate in Re-Establishing European Perch in Some Highly Acidified Lakes in Southernmost Norway

In order to test whether major reductions in acid inputs had improved water quality sufficiently for fish populations to recover, we stocked wild European perch (Perca fluviatilis) in three highly acidified lakes that had previously supported this species, and in one limed lake. The fish, which were introduced from a local lake (donor lake), generally ranged from 12 to 16 cm in total length, and were stocked at densities of 117–177 fish ha-1. The untreated lakes were highly acid, with minimum pH values and maximum inorganic aluminium concentrations (Ali) during the spring of 4.6–4.7 and 118–151 μg L-1 respectively. In the limed lake, the corresponding values for pH and Ali ranged between 5.8 and 6.6 and 5 and 19μig L-1 respectively. Gill-netting in two subsequent years after the introduction yielded only a few recruits (0+) and one adult in one of the three acidified lakes in one year only. However, stocked perch reproduced successfully in both years in the limed lake. There was a significant linear relationship between the catches (CPUE) of juvenile perch (age 0+) in the different lakes in the autumn and the water quality in May (time of hatching), both in terms of Ali (r 2=0.934, P 60 μg L-1.

Acanthodiaptomus Tibetanus Daday, 1908 (Copepoda, Calanoida, Diaptomidae): New Records of a Very Rare Species

[In 1992 Acanthodiaptomus tibetanus was found in material from northern Norway sampled in 1979, 1992, and 1993, and in 1992 also in Sor-Trondelag, Central Norway. This species has previously been recorded from only a few other localities, and has a very sparse and scattered distribution. In this paper, we discuss the distribution of this rare species and the reasons for its puzzling distribution pattern., In 1992 Acanthodiaptomus tibetanus was found in material from northern Norway sampled in 1979, 1992, and 1993, and in 1992 also in Sor-Trondelag, Central Norway. This species has previously been recorded from only a few other localities, and has a very sparse and scattered distribution. In this paper, we discuss the distribution of this rare species and the reasons for its puzzling distribution pattern.]