Spatial and temporal variability in water temperatures in the littoral zone of a multibasin lake

Current models of the offshore thermal structure in lakes suggest that the thermal regime inshore should vary seasonally, and should vary systematically from upwind to downwind littoral sites. To test these hypotheses, we measured mean temperature and short-term (<2 days) temporal variability in water temperature at 23 shallow littoral sites in four basins of Lake Opeongo, Ontario, Canada. Water temperature in the littoral zone was most variable, both spatially and temporally, in the spring. Spring water temperature differed by as much as 7–15°C among littoral sites in different basins (median difference among sites = 2–4°C). Downwind sites were generally warmer and had more constant temperature than upwind sites, but the magnitude of these differences varied among basins of different sizes and shapes. Simple calculations of growth rates and of fish hatching times suggest that the observed variability in water temperature would result in differences in the productivity of different portions of the littoral zone.