Vertical gradient of nutrients in two dimictic lakes ? influence of phototrophic sulfur bacteria on nutrient balance

Abstract

Vertical profiles of soluble and particulate nutrients were analyzed at the end of summer stratification in two dimictic lakes located in northeast Germany. In addition, irradiance and plankton biomass were determined. The concentrations of particulate organic carbon and phytoplankton biomass in the epilimnion were higher in Lake Tiefer than in Lake Dudinghausen, even though the apparent trophic status of Lake Tiefer was higher than Lake Dudinghausen. In Lake Dudinghausen, phototrophic sulfur bacteria accumulated in the hypolimnion between 8 and 10 m, whereas in Lake Tiefer low light penetration prevented the development of phototrophic bacteria in those horizons in which sulfide might be present. Because both lakes have anoxic hypolimnia, we assumed that in both cases phosphorus was released from the sediment Aquatic Sciences into the hypolimnion. In Lake Tiefer, redox conditions and the presence of nitrate and nitrite limited the water depth range in which P-release occurred. In Lake Dudinghausen, part of the released soluble reactive phosphorus was incorporated into the phototrophic sulfur bacteria biomass and thus transformed to particulate phosphorus. As much as 70% of the particulate phosphorus in the hypolimnion was found in the phototrophic sulfur bacterial layer, with 15 -20 % of this particulate phosphorus consisting of polyphosphate storage compounds. The low ratio of soluble reactive phosphorus to particulate phosphorus in the hypolimnion was, therefore, attributed to phototrophic sulfur bacteria. The phototrophic sulfur bacteria appear to act as an internal nutrient filter and convert soluble reactive phosphorus into particulate phosphorus.

Assessing P status and trophic level of two lakes by speciation of particulate phosphorus forms

“…Separate data for the Lake Bützow no exist. In contrast Lake Dudinghausen has a thermic stratification and anoxic hypolimnion during the summer (Selig et al 2004). The catchments area is small (<16 km 2 ) and the most input of nutrients comes from the groundwater (Dressler et al 2006).…”

“…Nutrient concentrations and phytoplankton counts were determined in the same steps in both lakes, but only presented here for the surface water (0.5 m) for the direct comparison of both lakes. Results of the vertical distribution of nutrients and plankton in Lake Dudinghausen were described in Selig et al (2004) separately. Samples were kept at 4 °C in the dark and analysed within the next 3-5 h.…”

“…The accumulation of polyP in freshwater ecosystems was observed more at the sediment-water interface (Davelaar 1993) or on the thermocline and chemocline in dimictic lakes (Selig et al 2004). In P-rich wastewater systems the absence of polyP accumulation by organisms has been discussed as reflecting stress situations (Kjeldstad et al 1991;Lawrence et al 1998).…”

Characterisation and quantification of phosphorus release from profundal bottom sediments in two dimictic lakes during summer stratification

“…by heterotrophic bacterioplankton (Morris & Lewis 1992) or by phototrophic bacterioplankton (Baneras & Garcia-Gil 1998). For Lake DUD the transformation of released SRP by the biomass of phototrophic sulfur bacteria was described by Selig et al (2003b). A calculation of the P-release using the TP-concentration of the hypolimnion was not possible, because the settling particulate phosphorus would be included.…”

Water Quality Assessment and Spatial-Temporal Distribution of Nitrogen in the Tianzhuang Reservoir

“…The special-temporal distribution of pollutants is influenced by the sources and eliminations of the contaminants [4]. Analyzing the distribution characteristics and water quality assessment can examine the key pollutants and their main sources elementarily.…”