Patterns of phytoplankton productivity in two morphologically different oxbow lakes in the Black Warrior River drainage in Alabama, U.S.A.

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Many different types of oxbow lakes, created by river meandering, exist in the drainage of the Black Warrior River. Phytoplankton productivity and spatial distribution of productivity using the ¹⁴C method were studied in two morphologically different oxbow lakes. Touson Lake is a typical oxbow lake type in the region with steep basin morphometry, length (1): 1.2 km, maximum depth (Zm): 6.7 m. Cypress Pond has shallow depth and well-developed submersed aquatic plants, I: 2.25 km, Zm: 2.2 m. Daily production at Touson Lake ranged from 43 to 550 mgC/m²/day (mean: 258, n=6), while Cypress Pond showed somewhat lower productivities (range: 16 to 256 mgC/m²/day, mean: 88, n=4). In highly turbid Touson Lake, highest productivities usually occurred at the surface. In Cypress Pond productivity, which was inhibited at the surface by light, was highest at the 0.5 m depth. Spatial distribution of productivity at Touson Lake was not variable among the 5 sites (19.86 ± 6.6 mgC/m³/h, n=5). However, highly variable distributions of productivity occurred in Cypress Pond (16.51 ± 19.1 mgC/m³/h, n=6). This variability was partly supported by fluctuating underwater light conditions caused by the distribution of submersed aquatic plants. Based on phytoplankton productivity, Touson Lake and Cypress Pond appear to belong to the mesotrophic and oligotrophic lake categories, respectively.
信州大学理学部の論文