Use of time-series analysis to demonstrate advection rates of different variables in a small lake

Abstract

Time-series analysis of daily data from 3 stations (maximum separation – 1 km) in a small lake (Guelph Lake, Ontario) has demonstrated the existence of (0 strong horizontal advection within the basin at a time scale of 2–3 d and (ii) longer term periodicities (10–20 d) associated with the passage of atmospheric weather systems. Different rates and directions of horizontal advection were observed for different variables. Fluctuations in integral SRP concentrations at station 1 (outflow end) consistently occurred 3 d later than at station 3 (inflow end). The algal biomass (chlorophyll a) at station 1 lagged that at station 3 by half a day. The time lag between station 1 and station 3 for Aphanizomenon flos-aquae was 7 d, whereas for Ceratitun hirundinella station 1 led station 3 by 3 d indicating motion by the species in opposite directions. The distribution of the algal biomass in space and time was a composite of the individual species patterns. Longer term (10–20 d) periodicities were also observed. Examination of the periodicities in the average daily wind speed and water column stability showed that such lags or leads were likely due to periods of vertical mixing. The significance of these results is then discussed in relation to sampling schemes for the analysis of phytoplankton dynamics in small basins.