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Phytoplankton growth in the Ohio, Cumberland and Tennessee Rivers, USA: inter-site differences in light and nutrient limitation
Koch, R.W.; Guelda, D.L.; Bukaveckas, P.A. (2004). Phytoplankton growth in the Ohio, Cumberland and Tennessee Rivers, USA: inter-site differences in light and nutrient limitation. Aquat. Ecol. 38(1): 17-26. dx.doi.org/10.1023/b:aeco.0000021082.42784.03
In: Aquatic Ecology. Springer: Dordrecht; London; Boston. ISSN 1386-2588, more
Peer reviewed article  

Available in Authors 

Keywords
    Dams; Growth rate; Light attenuation; Limiting factors; Nutrient deficiency; Phytoplankton; Water reservoirs; USA, Cumberland R.; USA, Ohio R.; USA, Tennessee R.; Fresh water

Authors  Top 
  • Koch, R.W.
  • Guelda, D.L.
  • Bukaveckas, P.A.

Abstract
    Seasonal patterns in resource limitation of phytoplankton growth were assessed monthly within three large rivers with differing extents of water regulation. The Ohio River is regulated by low dams that do not substantially modify discharge, while the Cumberland and Tennessee Rivers are impounded by a series of high dams to enhance water storage for downstream flood control. Laboratory dilution assays with light and nutrient manipulations indicated that light was the main factor limiting phytoplankton growth at irradiances below 7 E m-2 d-1. Light limited growth was frequent in the turbid, higher discharge of the Ohio River, but was rare in the heavily regulated Tennessee and Cumberland Rivers. When irradiance exceeded 7 E -2 d-1, phytoplankton were either P-limited (Cumberland River), co-limited by P and N (Tennessee River), or Si limited (Ohio River). Site-specific differences in nutrient limitation were consistent with differences in ambient nutrient levels, with the Tennessee and Cumberland Rivers characterized by lower N and P concentrations, and the Ohio River by lower Si. Downstream nutrient depletion was evident in the Ohio River through comparison of an upstream and a downstream site, with nutrient limitation (Si) occurring more frequently downstream. Phytoplankton growth rates at ambient light and nutrient levels ranged from 0.1 to 1.5 d-1 in the Ohio River and 0.2 to 0.6 d-1 in the Tennessee and Cumberland Rivers. Growth rates were greatest at the onset of the summer base pool, as light intensities increased and nutrient levels were maximal. Our findings indicate that multiple factors regulate phytoplankton growth in regulated rivers and that spatial complexity may arise from differences in discharge and water aging.

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