Limnology of Shallow Lakes in the Yukon Flats National Wildlife Refuge, Interior Alaska

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ABSTRACT Data from 129 shallow riverine lakes within the Yukon Flats National Wildlife Refuge (between 65° 45'N and 67° 30'N and 142° 30'W and 150° 00'W) are presented as a baseline contribution to the regional limnology of Alaska. Ion composition reflected the composition of carbonate alluvium within the region; in most lakes Ca > Mg and bicarbonate dominated the anions (~90%). In lakes where alkali deposits occurred, Na, Mg and bicarbonate were the principal ions. Some 25% of the lakes were slightly brackish (conductivity >500 μS) to brackish. The lakes are colored, with 18 to 447 Pt-units. And, they are fertile, with over 70% classified as eu-or hypereutrophic on the basis of their nutrient content. Ratios of N:P suggested nitrogen was potentially limiting in about half the study lakes and was increasingly important at high P values. The yield of algal chlorophyll (Chl) per unit of plant nutrient was low in these lakes and Chl-nutrient relations explained less of the variance relative to published models. Invertebrate grazing potentially regulates Chi in some lakes. Typically these lakes freeze to the sediments and most do not support a permanent fishery. High ratios of organic suspended solids to Chl indicate detrital carbon contributes to the filterable carbon pool of these shallow lakes.