General patterns in the seasonal development of chlorophyll a for temperate lakes

Abstract

The seasonal cycle of phytoplankton biomass in temperate lakes is often represented as spring and fall blooms with intervening biomass minima, but the generality of this pattern has never been critically evaluated. Chlorophyll a time series from 56 north‐temperate lakes and reservoirs were collected and general patterns in the seasonal distribution of Chl a determined for oligotrophic and eutrophic lakes separately. The magnitude of temporal variation is greater in eutrophic lakes (mean [Chl a] > 12 mg m−3) and is partitioned into discrete spring and fall blooms. Chlorophyll a concentrations in oligotrophic lakes (mean [Chl a] < 7 mg m−3) are low for the first 4 months of the year, then increase through April and May. Synchronous summer depressions and fall blooms are not evident for oligotrophic lakes overall. Mean [Chl a] and mean annual air temperature were negatively correlated with the date of spring bloom. The date of spring bloom was not correlated with mean depth.