ISSN:
1572-9893
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geography
Notes:
Abstract Xuanwu Lake (3.7 km2) is a shallow (mean depth 1.4 m) hypereutrophic lake (annual productivity greater than 600 g cm−2) located in East China's flood plain near the N end of Nanjing, China's ninth largest city. Paleolimnological data based on a 16 cm long sediment core removed from near the center of the lake indicated that nutrient pollution tolerant diatoms have replaced pollution intolerant taxa which were common near the base of the core (approximately 35 years before present). These paleolimnological observations support the hypothesis that progressive eutrophication is occurring in Xuanwu Lake. This conclusion is corroborated by direct comparisons of the present day phytoplankton and zooplankton species composition within the lake and published accounts of its species composition during the mid 1970's. During the last decade, zooplankton density has increased 153% and zooplankton species' richness has declined by 33%. Phytoplankton biomass has increased over 10-fold and the lake's photic zone has decreased to its current (1987) condition (1% surface light intensity at 0.7 m). Xuanwu Lake, like many similar shallow polymictic lakes in E China, has not been depleted of dissolved oxygen near its bottom. This is due to frequent wind mixing, of the entire lake. Thus its progressive hypereutrophication does not result in the same suite of problems experienced by lakes whose hypolimnion is stagnant for long periods of time.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00209079
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