Monitoring submersed vegetation in a mesotrophic lake:: correlation of two spatio-temporal scales of change

The submersed vegetation of mesotrophic, alkaline Chenango Lake in New York, USA, was monitored at two spatio-ternporal scales: a 200m(2) rid censused annually from 1978 to 1993 and again in 2001 (12,800 quadrats), and a 1.8 ha littoral zone sampled every 6-10 years (1978, 1984, 1991, and 2001; 3600 quadrats). The grid vegetation fluctuated rather erratically for the first 11 years with each of the dominant species showing a different pattern of change. Frequency values for Chara vulgaris were the most dynamic, while those for Vallisneria anzericana were the most stable. After 1989, grid vegetation declined, so that by 2001, Only four of the original 11 species were present (including the original dominants), and the total number of observations declined to <10% of the maximum recorded. This decline is attributed to vigorous benthic feeding by carp (Cyprinus carpio), not noted in 1978 but relatively abundant by 2001. Frequency changes of species in the 200m(2) grid were positively correlated with corresponding frequency changes in the 1.8 ha littoral zone, indicating that a small, carefully chosen area may reflect vegetation at a larger scale. This was particularly true when vegetation change was appreciable. (C) 2004 Elsevier B.V. All rights reserved.