Comparative analysis of nutrients,chlorophyll and transparency in two large shallow lakes (Lake Taihu,P.R. China and Lake Okeechobee,USA) |
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Authors: | R Thomas James Karl Havens Guangwei Zhu Boqiang Qin |
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Institution: | (1) Lake Okeechobee Division, South Florida Water Management District, West Palm Beach, FL 33411, USA;(2) Florida Sea Grant College Program, University of Florida, Gainesville, FL 32611, USA;(3) Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, People’s Republic of China |
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Abstract: | This article compares limnological attributes of two of the world’s largest shallow lakes—Lake Okeechobee in Florida, USA
and Lake Taihu in P.R. China. Both the systems support an array of ecological and societal values including fish and wildlife
habitat, public water supply, flood protection, and recreation. Both have extensive research programs, largely because of
concern regarding the lakes’ frequent cyanobacterial blooms. By evaluating these systems together, we compare and contrast
properties that can generally advance the understanding and management of large shallow lowland lakes. Because of shallow
depth, long fetch, and unconsolidated mud sediments, water chemistry, and transparency in both the lakes are strongly influenced
by resuspended sediments that affect light and nutrient conditions. In the central region of both the lakes, where depth is
the greatest, evaluation of limiting factors by a trophic state index approach indicates that light most often limits phytoplankton
biomass. In contrast, the more sheltered shoreline areas of both the lakes display evidence of nitrogen (N) limitation, which
also has been confirmed in nutrient assays conducted in earlier studies. This N limitation most likely is a result of excessive
levels of phosphorus (P) that have developed in the lakes due to high external loads over recent decades and the currently
high internal P recycling. Comparisons of these lakes show that Lake Taihu has higher N than, similar total phosphorus (TP)
and similar light conditions to that of Lake Okeechobee, but less chlorophyll a (CHL). The latter may be as a result of lower winter temperatures in Lake Taihu (around 5°C) compared to Lake Okeechobee
(around 15°C), which could reduce phytoplankton growth and abundance through the other seasons of the year. In these systems,
the important role of light, temperature, and nutrients in algal bloom dynamics must be considered, especially due to possible
adverse and unintended effects that might occur with projects such as sediment removal, and in the long term, in regard to
buffering lake responses to external load reduction.
Handling editor: D. Hamilton |
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Keywords: | Nutrients Phytoplankton Light limitation Suspended sediment Algal blooms Eutrophication Trophic state index |
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