. The Canadian field-naturalist. 1983 Fraser and Morton: Aquatic Plants 183. 1—I—I—I—I—1—I—I—I—r 40 50 "T" 10 -1—I—I—I 1—r 20 30 TA (ppm) Figure 1. Relation between Ca and TA in the water of 14 lakes in Lake Superior Provincial Park. The regression line is based on 11 lakes, omitting( 1) Moose Lake, (2), Mijin Pond, and (3) Boulder Lake, which had unusually high levels of Ca relative to TA. The anomaly is likely related to the high levels of Na and CI, presumably derived from highway salt, in these three lakes. Lakes of lower alkalinity generally included typical softwater species su
. The Canadian field-naturalist. 1983 Fraser and Morton: Aquatic Plants 183. 1—I—I—I—I—1—I—I—I—r 40 50 "T" 10 -1—I—I—I 1—r 20 30 TA (ppm) Figure 1. Relation between Ca and TA in the water of 14 lakes in Lake Superior Provincial Park. The regression line is based on 11 lakes, omitting( 1) Moose Lake, (2), Mijin Pond, and (3) Boulder Lake, which had unusually high levels of Ca relative to TA. The anomaly is likely related to the high levels of Na and CI, presumably derived from highway salt, in these three lakes. Lakes of lower alkalinity generally included typical softwater species such as Lobelia dortmanna, Erio- caulon septangulare, Scirpus subterminalis, and Isoetes echinospora (Table 3). Potamogeton epihy- drus was one of the most abundant pondweeds. These features are similar to the softwater Shield flora de- scribed in Minnesota by Moyle (1945), in softwater Ontario lakes by Miller and Dale (1979), and in the three most mineral-poor lakes studied by Crowder et al. (1977). Also, Keddy( 1981) noted similar species in the very soft water of Axe Lake near Georgian Bay, Ontario, and Swindale and Curtis (1957) included Eriocaulon septangulare, Potamogeton epihydrus, and Myriophyllum tenellum in their group of plants with softwater affinities. Sparganium anguslifolium, Nuphar variegatum and Nymphaea odorata were common in the softwater lakes studies here, but are also common in more alkaline waters in the Lake Superior area and elsewhere (unpublished data). Despite their high NaCl content and high specific conductivity. Moose Lake, Mijin Pond, and Boulder Lake retained a flora fairly typical of other lakes of similar alkalinity. However, Scirpus subterminalis, Isoetes echinospora and Lobelia dortmanna were absent from the three salt-rich lakes although com- mon in other lakes, including Rabbit Blanket Lake which had similar alkalinity. This may have been a chance effect, or it may be related to the salt content of these lakes. In so
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