Wave‐induced shear stresses, plant nutrients and chlorophyll in seven shallow lakes

Abstract

1. Sediment resuspension dynamics were investigated in relation to changes in water column nutrients (TP, TN, PO4‐P, NO3‐N and NH4‐N), chlorophyll a and phaeopigment in seven shallow (Zm < 1.5 m) lakes in South Island, New Zealand, ranging in area from 0.1 to 180 km2. 2. Benthic shear stress, calculated from wind speed, effective fetch and depth, was a considerably better predictor of nutrient and pigment concentrations than wind speed. 3. For TP, TN, chlorophyll a and phaeopigment, sixteen of the possible twenty‐eight linear correlations with benthic shear stress were significant at P < 0.05, with 16–87% of the variation being explained by shear stress. 4. Wind decreased the ratios of TN : TP, with ratios exponentially approaching those of the sediments as shear stress increased in four of the lakes. 5. Relationships of dissolved inorganic nutrients to shear stress were considerably weaker than those for total nutrients and showed no consistent trend over the seven lakes. 6. Estimated annual mean TP inclusive of resuspension was over four times higher than that derived from measured calm samples in two lakes. 7. The number of nutrient and pigment parameters that were significantly correlated with shear stress and the strengths of the relationships varied widely from lake to lake. We could establish no simple relationships between these effects and any single characteristic of the lake, sediment, or water. 8. A function is developed to predict the rate of entrainment of TN and TP in response to an applied shear stress, where the independent variables are sediment nutrient content and particle size, and the macrophyte density in the lake.

Recent occurrence ofCylindrospermopsis raciborskiiin Waikato lakes of New Zealand

“…These three lakes appear to provide ideal conditions for the proliferation of C. raciborskii, with high concentrations of nutrients and low water clarity (Table 1). Other shallow lakes in New Zealand which have changed to an "alternative stable state" (Scheffer 1998) signalled by nutrient enrichment, high turbidity, and loss of macrophytes (Hamilton & Mitchell 1997), could also be expected to be susceptible to blooms of C. raciborskii, depending on water temperature. C. raciborskii does not appear to be favoured by a specific thermal stratification regime (Antenucci et al 2002) whereas bloom formation in many other species of cyanobacteria (e.g., Microcystis sp.…”

Nutrient Concentration Distribution in Sediment and Overlying Water at Bukit Merah Reservoir, Perak

“…However, compared with other studies, including shallow eutrophic lakes in northern Europe [11][12][13], New Zealand [14] and Estonia and Russia [15], phosphorus and nitrogen in sediments are still low. This may be caused by the large surface area of BMR.…”

Improvement of water quality by sediment capping and re-vegetation with Vallisneria natans L.: A short-term investigation using an in situ enclosure experiment in Lake Erhai, China

“…Moreover, the variation in Chl-a due to algal growth and death led to transformation and greater dynamics of nutrients in the control. The experimental enclosures were located in shallow water in the windy Lake Erhai, and thus wave-induced resuspension of soft sediment might have contributed to the release of nutrients from the sediment into the water column in the control (Hamilton and Mitchell, 1997), in contrast to the other two treatments with sediment capping, which stabilized the surface sediments (Vopel et al, 2008;Lin et al, 2011). The synchronic changes in DIN, N-NO 3 , N-NH 4 , SRP, SD and K suggested that abiotic factors (i.e., wind-induced waves) were affecting the three treatments simultaneously, in contrast to Chl-a, TN and TP, which were closely related to algal growth and N and P found in the algal biomass, and thus differed significantly between the control and the other two treatments.…”