Limnological succession in reservoirs: a paleolimnological comparison of two methods of reservoir formation

Abstract

Analysis of diatoms, algal pigments, and chironomids in sediment cores from two otherwise similar prairie reservoirs demonstrated that differences in reservoir formation (river valley impoundment versus lake inundation) and hydrological regime (variable versus stable water level) resulted in distinct patterns of aquatic community change. Lake Diefenbaker, a 500-km2 reservoir created by damming the South Saskatchewan River in 1968, experiences water level fluctuations of 6 m·year-1. In contrast, impoundment of Buffalo Pound Lake in 1952 flooded a natural lake, raised mean water levels ~2.0 m, and reduced water level fluctuations from ~3 to <1 m·year-1. Comparison of fossil records showed that reservoir formation did not inevitably lead to eutrophication. Lake Diefenbaker exhibited typical reservoir ontogeny with three trophic periods, including an initial ~4-year period of eutrophy, a decade of mesotrophy, and a gradual shift to modern productive conditions. Planktonic taxa dominated diatom communities at all times, whereas benthic chironomid and algal remains were rare. In contrast, pigment analyses suggested that phytoplankton standing crops declined after impoundment in Buffalo Pound Lake but that chironomid and macrophyte populations expanded. Such site specificity in trophic development appears to result from differences in the extent of inundation (500 versus ~5 km2) and the magnitude of subsequent water level fluctuations (6.3 versus <1 m).

Spatial variation of nitrogen fixation in lakes of the northern Great Plains

“…1 in Hall et al 1999b). Land use within the Qu'Appelle basin is 75% cropland and 12% natural grasslands (Hall et al 1999b) while main urban centers include the cities of Regina and Moose Jaw.…”

“…1 in Hall et al 1999b). Land use within the Qu'Appelle basin is 75% cropland and 12% natural grasslands (Hall et al 1999b) while main urban centers include the cities of Regina and Moose Jaw. Under natural conditions, the Qu'Appelle River originates near Eyebrow Lake, Saskatchewan, and flows through Buffalo Pound Lake, a central chain of four basins (Pasqua, Echo, Mission, and Katepwa lakes), and two downstream lakes (Crooked and Round).…”

“…Algal composition during 1994-2004 was also estimated by analyzing algal pigment concentrations in integrated water-column samples (Graham 1997;Hall et al 1999b). Carotenoid, chlorophyll, and derivative pigment concentrations were quantified using a Hewlett Packard model 1050 HPLC system following standard procedures detailed in Leavitt and Hodgson (2001).…”

“…Biomarker concentrations (nmol pigment L 21 ) were estimated for pigments characteristic of total algal abundance (Chl a, pheophytin a, bcarotene), siliceous algae and some dinoflagellates (fucoxanthin), mainly diatoms (diatoxanthin), cryptophytes (alloxanthin), chlorophytes (Chl b, pheophytin b), chlorophytes and cyanobacteria (lutein-zeaxanthin), total cyanobacteria (echinenone), colonial cyanobacteria (myxoxanthophyll), Nostocales (canthaxanthin), and potentially N 2 -fixing cyanobacteria (aphanizophyll). In this HPLC system, carotenoids from Aphanizomenon (aphanizophyll), Anabaena (4-keto-myxoxanthophyll), and the Oscillatoriaceae (oscillaxanthin) were incompletely resolved and were presented together as ''aphanizophyll'' (Hall et al 1999b).…”

Modelling Dissolved Oxygen/Sediment Oxygen Demand under Ice in a Shallow Eutrophic Prairie Reservoir

“…Air temperatures range between a daily minimum of −17.7 °C in January to a daily maximum of 26.2 °C in July [25]. Over 95% of the drainage basin is agricultural land [26] suggesting that non-point nutrient sources (diffuse pollution, overland run-off) may factor significantly in nutrient loading to BPL. Water quality issues such as eutrophication remain a challenge, and the reservoir has persistent problems with taste, odour, and algal blooms [27,28].…”