Plant Pigments in Bottom Sediment Cores as Indicators of the Trophic State in Large Shallow Lakes Vozhe and Lacha (Russia)

Abstract

The first data on the content of plant pigments is presented for the cores of bottom sediments sampled in large shallow lakes Vozhe and Lacha located in the upper reaches of the Onega River. In the 1-m core of olive silts, the total concentration of chlorophyll a and pheopigments varied within 35–236 (94.2 ± 3.3) in Lake Vozhe and 58–118 (83.8 ± 1.3) μg/g dry sediment in Lake Lacha. The degree of chlorophyll destruction in the cores from Lake Lacha (98.7 ± 0.2%) was higher than in Lake Vozhe (85.2 ± 0.7%). Considering the average long-term sedimentation rate of 0.2 and 0.4 mm/year in Lakes Vozhe and Lacha, respectively, the annual vertical flux of chlorophyll a and pheopigments is 4.0 and 6.2 mg/(m2 · year) for the last 2500 years, respectively. Nowadays, the average annual rate of pigment accumulation is almost the same in the lakes (5.6 and 5.3 mg/(m2 · year)). Over the period under consideration until now, different patterns of long-term dynamics of pigment accumulation in the studied lakes have been revealed; in particular, there is a positive trend in Lake Vozhe and a negative trend in Lake Lacha.