Effects of water column nutrient enrichment on the growth of Potamogeton maackianus A. Been

Laboratory aquarium experiments were conducted to study the effects of water column nutrient enrichment on the growth of Potamogaeton maackianus A. Been, a dominant submersed macrophyte in Lake Donghu before the 1970s. The plant was grown in fertile sediment, gradients of water nutrients and different shade intensities for 40 days. At the end of the experiment, redox potential of the sediment was negatively related to the water nutrient concentration, while nitrogen and phosphorus concentration, and peroxidase activity of the plant tissue was positively related to the nutrient gradient. Plant growth reduced at light levels corresponding approximately to the depth range of 0.9-1.5 m given current water transparency within Lake Donghu. Within this stress zone, plant chlorophyll content, total shoot length increased primarily with the increased stress and peaked at 1.2 to 1.3 m depths, showing a narrower adaptive range of the plant than the low light stress range. The present study indicates that growth of P maackianus is strongly inhibited by consequences of nutrient enrichment in water. Thus, eutrophication in Lake Donghu during 1970s may have played an important role in the disappearance of this species from the lake