Abstract
We have measured the water quality and bio-optical parameters of 94 samples from Taihu Lake in situ and/or in the lab between June 10-18, 2007. A transparency-assisted decision tree was developed to more accurately divide the aquatic vegetation zone into a floating vegetation-dominated zone and a submerged vegetation-dominated zone, whose respective present biomass retrieval models were easily developed with an empirical approach because of the quasi-concurrence of ground field investigations with the satellite sensor flight over the lake. The significant quantitative relationships between the vegetation index NDVI (Normalized Difference Vegetation Index) of different images at different times were used to help develop the past biomass retrieval model on the basis of the present developed model. In Taihu Lake, the total covering area of aquatic vegetations decreased from 454.6 km2 in 2001 to 364.1 km2 in 2007. Correspondingly, the total biomass decreased from 489,000 tons in 2001 to 406,000 tons in 2007, suggesting that a great change in the ecological environment has been taking place in Taihu Lake over this period.
Highlights
Aquatic vegetation, generally existing in the shallow near-shore area, is a key component of lake ecosystems
Since traditional quantitative ground investigations on the scale of a whole lake are laborious, remote sensing methods are increasingly being used for mapping aquatic vegetation and estimating their distribution and biomass [6,7,8,9]
This paper aims to present an approach to estimate the past biomass of aquatic vegetation in a shallow inland lake using the historical satellite imageries without any corresponding field investigations, based on the present satellite imagery provided along with concurrent or quasiconcurrent ground field investigations, and to determine the historical change of the aquatic vegetation in Taihu Lake
Summary
Generally existing in the shallow near-shore area, is a key component of lake ecosystems. This vegetation provides food, shelter and breeding habitats for aquatic animals like. Sensors 2008, 8 invertebrates, fish and wading birds, and helps maintain the balance of the lake ecosystem. It plays an important role in maintaining a clean lake water quality by stabilizing sediments and providing a substrate for periphyton that actively removes nitrogen and phosphorus from the water column. Since traditional quantitative ground investigations on the scale of a whole lake are laborious, remote sensing methods are increasingly being used for mapping aquatic vegetation and estimating their distribution and biomass [6,7,8,9]
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