Spatial heterogeneity in whole lake sediments — towards a loading estimate

Abstract

Studies of nutrient loadings, to shallow culturally eutrophied Alberta lakes, suggest internal inputs are significant. In this regard, estimation of bottom sediment P loads to Lake Wabamun (80 km 2 , 5.5 m x depth) were examined. Initially we determined the spatial variability in Total Organic Content (% loss on ignition) and Total Phosphorus, as indicators. Phosphorus fractions and biologically available phosphorus (BAP) were measured at specific stations. These data showed a very uniform distribution in sediment type with a Total Organic Content of 40.6 ± 3.3 (95% C.L.) at the west end, gradually declining to 26.3 ± 0.9 at the east end. Transects performed at routine monitoring stations indicate the representativeness of each station, e.g., station 2, 40.8 ± 1.3 (10 sites). One explanation of this uniformity is provided from 2 10Pb analysis of shallow cores which indicate mixing to a depth of 16 cm. This is also thought to explain the mechanics of P loading to the water phase. Finally, Total Organic Content relates well to BAP (r 2 = 0.80). It is hoped that this simple technique may well permit more precise extrapolation to whole lake BAP estimates at least on this lake.

Spatial patchiness in the lacustrine sedimentary environment1

“…This finding is in basic agreement with Reynoldson and Hamilton (1982). Most other sediment characteristics require greater sampling effort near the minimum concentrations that we encountered: 300 samples for pigments, 80 samples for organic matter (dry mass), 20 samples for water content.…”

“…Twinch and Peters 1984) or station (e.g. Reynoldson and Hamilton 1982). Although some researchers have shown high coefficients of variation, C.V. = 100 (s2/mean), among replicate cores taken at the same site (Hargrave and Nielsen 1977;Slater and Boag 1978;Anderson et al 1982), it is unclear whether this "heterogeneity" results from spatial variation or analytical error (cf.…”

“…Sediment patchiness may result from the activities of aggregated animals, sediment transport by deep currents, and small-scale variations in bottom profile. Reynoldson and Hamilton (1982) studied the spatial variation of phosphorus in the sediments of one lake and concluded that homogeneity is the most apparent feature of the spatial pattern of the sediments. …”

Eutrophication of Freshwaters

“…The increased phosphorus loading of the experimental period was 'diluted' and thus little was returned even under anaerobic conditions. Shallow eutrophic lakes in Alberta showed mixing to a depth of 16 cm (Reynoldson and Hamilton, 1982) which regulated phopshorus release .. Lakes which have been eutrophic for longer periods would, on this explanation, be expected to show progressively greater phosphorus return from internal loading because their sediments are saturated.…”

Spatial variability and the controlling mechanisms of surface sediments from Nam Co, central Tibetan Plateau, China

“…Some mechanisms affecting sedimentary processes have also been distinguished, such as turbidity currents from delta foreslopes that affect deep water depositional pattern (Lamoureux, 1999). Reynoldson and Hamilton (1982) suggested that wind action could disturb bottom sediment, resulting in homogeneous sediments, whereas other studies suggested wind was a forcing factor for uneven sediment distribution patterns (Odgaard, 1993;Whitemore et al, 1996). Bacterial oxidation (Hilton and Gibbs, 1984), benthic animals' activity (Downing and Rath, 1988), industrial distribution and land use conditions Rose et al, 1998;Gälman et al, 2006) are all influencing factors that can affect the distribution of sediments.…”