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Twenty-six chrysophycean stomatocyst morphotypes were described from the postglacial sediments of a small, rock basin lake near Baird Inlet, Ellesmere Island. Scanning electron and light microscopy were used to classify the stomatocysts, following the guidelines of the International Statospore Working Group. None of the stomatocysts could be related with certainty to the chrysophyte species that produced them, but sufficient morphological detail is present in most of the stomatocysts to allow for taxonomic differentiation. A stratigraphic analysis of the dominant stomatocyst morphotypes revealed that chrysophyte species composition changed most markedly during the lake's early development but then remained relatively constant. This study demonstrated that chrysophycean stomatocysts provide useful paleoecological information in High Arctic lakes, but further taxonomic and ecological research is required to fully exploit these microfossils.

The distributions of chrysophyte stomatocysts in the sediments of 221 lakes from four study areas located in British Columbia, Canada (two datasets), New York, U.S.A., and south central Siberia were examined. The combined lake set spanned a wide range of chemical and morphometric variables. Approximately 400 cyst morphotypes were identified, from which we selected sixty‐three common types for further analysis. Canonical ordination (detrended canonical correspondence analysis (DCCA) and constrained DCCA) showed that four environmental variables (pH, conductivity, depth and total phosphorus (TP) ) were significant (Monte Carlo permutation test, P=0.01 for all four variables) and independent determinants of the cyst distributions. Weighted averaging (WA) inference models were developed for each variable. The best models, in terms of their r2, were developed for pH and conductivity (r2=0.78 and 0.73, respectively). The models for depth and TP were less robust (r2=0.47 and 0.46, respectively). We discuss the relative importance of conductivity and salinity, lakewater acidity and metal concentrations, lake morphometry and trophic status as determinants of chrysophyte population distributions, and possible causal mechanisms for each variable. We identify assemblages of cysts that appear to be associated with six different groups of lakes: (1) very acidic (pH <6.5) lakes; (2) acidic (pH <7.0), softwater lakes; (3) circumneutral (pH 7–8), oligo‐ to mesotrophic lakes; (4) alkaline, hardwater, meso‐ to eutrophic lakes; (5) shallow, alkaline (pH 8–8.5), meso‐ to eutrophic lakes; and (6) shallow, very alkaline (pH >8.5) lakes, including sub‐ and hyposaline lakes. Finally, we suggest further possible avenues for research that will improve the usefulness of chrysophyte stomatocysts as paleolimnological indicators.

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1992. Chrysophyte cysts in 36 Canadian high arctic ponds. -Nord. J. Bot. 12: 471499. Copenhagen. ISNN 0107-055X.Chrysophyte stomatocysts were described from the surface sediments and other habitats (moss, rocks, and open water) of 36 ponds located on Cape Herschel, Ellesmere Island in the Canadian high Arctic (78"37'N). Thirty-five distinct stomatocyst types were described using scanning electron microscopy (SEM); 1 other cyst was common, but was not observed with SEM. Our study ponds were diverse limnologically and contained distinct cyst floras, but the cause(s) of the floristic differences are as yet unclear. Two ponds with extreme values of water chemistry (i.e. high salinity and low pH) supported unique cyst floras. Distinctive cyst floras were also observed in ponds with high nutrient input from nesting birds and/or with diverse microhabitats (e.g. moss banks), which may provide substrate for periphytic chrysophytes. Arctic pond cyst floras are typically less diverse than those from temperate regions. Highly ornamented cysts are also less common in arctic waters, but the reason for this is unknown. Stomatocysts could be used to augment paleolimnological research in arctic ponds, if the environmental factors controlling cyst distributions and possibly degree of ornamentation can be elucidated. MethodsThe 36 study ponds were sampled over the 1983, 1984, 1986 and 1987 field seasons. Algal samples covering a variety of habitats, including net tows, rock scrapes, and moss samples, were collected and preserved in Lugol's 472 N o d . J . Bot. I2 (4) (lYY2) solution (Lind 1974). Surface sediment samples, which sumption of normality necessary for parametric statistirepresent an integrated sample from many microhabitats, including in situ benthic growth, were collected from each pond. Conductivity and pH measurements were made in the field; additional water chemistry analyses were performed by the National Water Research Institute (Burlington, Ontario, Canada). Full details of field sampling methods, water chemistry, and other analyses are provided in Douglas (1989).Aliquots of samples were treated in a mixture of sulphuric acid and potassium dichromate (5% w/v) to remove organic compounds. For scanning electron microscopy (SEM), some of the treated slurry was evaporated onto 12 mm circular cover glasses, which were affixed to aluminum stubs using double-sided trans-cal analyses, and most of the 11 ponds were identified as unusual, or outlier, samples when direct ordination analysis was applied.N o d J Bot. 12 (4) (1992) 473 Tab. 1. Environmental variables in 36 Canadian High Arctic ponds. All names except Elison L. are unofficial. Major ions (Ca2+, rock or sediment bottom cover; Moss = approximate YO of perimeter occupied by moss; Depth = maximum depth (cm); Area = chrysophyte cysts, expressed as % of total fossils. Lake name Lake code Ca Mg Na K so4 CI SiO,