Assessing Sediment Accumulation in a Eutrophic Lake in Northern New York

ABSTRACT

We determined the pattern, rate, and extent of deposition of bulk sediments and sediment-bound phosphorus (P) in Black Lake. Vertical gradients in total phosphorus (TP) and ¹³⁷Cs often were irregular within cores and variable among cores, reflecting sediment disturbances including bioturbation, resuspension, and lateral transport. Surface sediments exhibited a horizontal spatial gradient in TP content, with P levels that declined downstream from the lake inlet, which reflected a large input of settleable P from the primary tributary. Sediment ¹³⁷Cs and TP data suggested an average lake-wide sediment accumulation rate of approximately 0.6 cm yr⁻¹ since the early 1960s and greater accumulation of TP in 1975–90 than during 1960–75. The mean depth of sediment accumulation over bedrock was estimated to be at least 3.6 m. These data indicate the contemporary rate of water depth decrease due to sediment accumulation in Black Lake is much greater than the lake's postglacial average, and the rate of sediment P accumulation may have increased recently.

Key Words:

• sediments
• sediment accumulation
• phosphorus
• radioisotopic dating
• organic matter
• eutrophication
• ground-penetrating radar