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Steinman A, Abdimalik M, Ogdahl ME, Oudsema M. 2016. Understanding planktonic vs. benthic algal response to manipulation of nutrients and light in a eutrophic lake. Lake Reserve Manage. 32:402-409. We examined the environmental factors influencing the growth of benthic and planktonic algae in Lake Macatawa, a hypereutrophic lake located in west Michigan. Turbidity may limit planktonic growth in the main body of the lake, despite high P concentrations, whereas shallow water depths in the littoral regions of the lake may allow benthic algal growth. We experimentally amended nutrients to benthic algae using nutrient diffusing substrates near the sediment surface and to phytoplankton using nitrogen (N) and phosphorus (P) spikes into 10 L carboys suspended from a PVC-constructed frame near the water surface to test how nutrient and light regimes influence these potentially competing autotrophic communities. Benthic algae were co-limited by N and P, whereas phytoplankton were P-limited. The N-only treatments resulted in negative algal growth. In addition, microcystin concentration (phytoplankton only) also responded positively to P additions and negatively to N-only treatments. We speculate that much of the P in this lake is bound to sediment and not bioavailable, so despite the high total P concentrations, the algae are P-limited at certain times of the year. Irradiance levels did not seem to be photosynthetically limiting during this study. Our results have management implications: (1) use of TP as an indicator of P limitation may be flawed without concomitant measurement of bioavailable P; and (2) control of external P loading is critical to directly limit phytoplankton abundance but also can result in indirect control of benthic algae if internal P loading from the sediment is a key source of P to this community.
- 出版日期2016
