Uwe Selig

Phosphorus storage in Chlorella vulgaris (Trebouxiophyceae, Chlorophyta) cells and its dependence on phosphate supply

S. Eixler, U. Karsten and U. Selig. 2006. Phosphorus storage in Chlorella vulgaris (Trebouxiophyceae, Chlorophyta) cells and its dependence on phosphate supply. Phycologia 45: 53–60. DOI: 10.2216/04-79.1 It has been postulated that the content of polyphosphates in microalgae can be used as a biological indicator for eutrophication. Therefore the total cellular phosphorus (TCP) and polyphosphate concentration in the green alga Chlorella vulgaris were investigated in relation to the amount of available inorganic phosphorus in the medium. Phosphorus starvation was induced by diluting the cultures with P-free medium to study the impact of this stress situation on phosphorus storage after phosphorus resupply. Increased activity of alkaline phosphatases was used as an indicator for actual phosphorus starvation of algal cells. After a P-starvation phase a significant increase in polyphosphate content could be observed. This effect was detected by using an extraction method and microscopic analysis. The variation in phosphate concentration in the medium of a well-supplied culture had much less effect on the degree of polyphosphate storage than a preceding P-starvation phase. Therefore, the amount of polyphosphate granules in algal cells is not suitable as an indicator for eutrophication (P-loading) of surface waters. The influence of P-starvation on subsequent P-uptake varied between experiments.

Particle size-related phosphate binding and P-release at the sediment–water interface in a shallow German lake

Phosphate binding and P-release in the sediment of the eutrophic shallow Lake Bützow are described based on sediment profiles, particle size fractions and incubation experiments. Total phosphorus was about 15% higher in the upper 0.5 cm layer than in the 0.5–1 cm layer. Phosphorus binding varied with sediment depth. Hot P→NaOH and P→HCl were the dominant fractions in all sediment horizons down to 10 cm depth, with values ranging from 20 to 30%. The P→H2O, P→BD, o-P→NaOH and nr-P→NaOH decreased with depth. The P→BD contributed 21% to Tot-P in the horizon 0–0.5 cm and decreased by half in 1–2 cm. The greatest proportion of particles (35%) was found in the 100–200 μm fraction. This size fraction also accumulated most of the phosphate. Moreover, P-forms were differently distributed in the various particle sizes of the sediment. Sediment particles <40 μm can be resuspended by a wind velocity of 2 m s−1, whereby 17% of the Tot-P from the topmost sediment were transported into the water column. The proportions of released labile phosphate, organic phosphate and hydrolysable phosphate were higher, with values of 24, 33 and 26%, respectively. Dissolved P was released under oxic and anoxic incubation, but anoxic release was higher. Comparison of the results shows that the P-release under anoxic conditions was equal to the P-release by resuspension, but under anoxic conditions the release of bioavailable P was higher.

Dissolved and particulate phosphorus forms in a eutrophic shallow lake

Abstract. Soluble and particulate phosphorus forms in the surface water of the eutrophic shallow Lake Bützow were investigated from March to November 1998. Soluble reactive phosphorus (SRP) and dissolved organic phosphorus (DOP) of the filtered water were analysed. Suspended particulate matter (SPM) was characterized by particulate organic matter (POM), particulate organic carbon (POC), particulate phosphorus (PP), particulate iron (PFe), phytoplankton biomass (PB) and Chl a. PP was investigated in more detail by means of sequential chemical extraction (Psenner et al., 1984) and the analysis of polyphosphates and phospholipids.¶ In spring, the lowest SRP values and highest PP values were recorded. Over the course of the year, SRP did not decline, whereas DOP increased and became the dominant P-pool in the lake in autumn. Polyphosphate, as a reserve compound in algae, was present only until July. Its decline was accompanied by an increase in phospholipids and a decrease in the easily available PP and the sorptive-bound PP. The levels of iron-bound phosphorus and the apatite-phosphorus remained stable over the year. The available phosphorus declined, although the SRP level never dropped below 0.015 mg L-1. Thus, insufficient phosphorus was available in this eutrophic lake to allow formation of polyphosphate granules in algae in the second half of the year. Neither SRP nor the elemental composition of seston is suitable to describe the P-status and deficiency for algal growth in the shallow Lake Bützow.

Extraction and detection methods for polyphosphate storage in autotrophic planktonic organisms

Different extraction procedures were employed to characterise the polyphosphate granules in autotrophic planktonic organisms, the green microalgae Chlorella vulgaris and the cyanobacterium Synechocystis sp. strain PPC 6803. The effectiveness of these methods was assessed using epifluorescence microscopic analysis of DAPI stained specimens as well as by electron spectroscopic imaging. The results clearly indicate that NaOH and hot water treatment followed by filtration of the extracts are suitable to obtain a cell free suspension of intact polyphosphate granules without hydrolysing the polymers. The methods described are useful to gain physiological information on the phosphorus status of autotrophic planktonic organisms.

Longitudinal patterns of phosphorus and phosphorus binding in sediment of a lowland lake–river system

In the Warnow River and its tributaries in North Germany, measurements were made to characterise the longitudinal patterns of nutrients in the riverbed and lake sediments. The sediment composition was analysed based on dry weight, organic matter, mean grain size and concentration of carbon, nitrogen, phosphorus, iron, aluminium and sulfur. Sediment phosphate was investigated in more detail by means of a sequential chemical extration. The phosphate was differently bound to the sediment particles in the upstream region than in the impounded section of the Warnow River and ist tributaries. Accumulation of fine sediment with high P-concentrations was recorded in the lake sediments and in the impounded section of the river. These impounded sections were the most important P-pool in the whole catchment area and played an important role in P-retention in the river system. Organic matter concentration, P-accumulation and P-binding in the sediment of the impounded section is corresponding with those of lake sediments. During the summer, anoxic P-release from the sediment in the impounded section was measured and calculated. The reductant-soluble fraction of the P-fractionation underestimated the release under anoxic condition. Adsorbed phosphorus and organic phosphate play an important role in P-release in the impounded part of the river.

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 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.

Distribution of three submersed macrophytes in coastal lagoons of the German Baltic Sea: comparison of laboratory and field data

Abstract The distributions of three submersed macrophytes Najas marina, Myriophyllum spicatum and Zostera noltii were surveyed in the inner coastal lagoons of the German Baltic Sea. Growth and photosynthetic performances of these species were investigated in crossed laboratory experiments (salinity × irradiance). Z. noltii showed the potential to grow in mesohaline lagoons, while N. marina seemed to be restricted to oligohaline areas. The potential distribution area of M. spicatum overlapped with those of the other two species. The laboratory results for N. marina and M. spicatum correspond with the recent distribution of the two species in the investigation area. However, neither historical nor recent distribution records of Z. noltii match the potential of this species to grow at 3 and 8 psu. Potential depth limits were calculated for the three species at their collection sites. Accordingly, N. marina had the potential to grow at 0.9–1.1 m depth in the Saaler Bodden, M. spicatum at 1.1–2.1 m depth in the Großer Jasmunder Bodden and Z. noltii down to 2.5–5.1 m depth in the Salzhaff. N. marina grows maximally at 1.0 m in the Saaler Bodden, M. spicatum at 2.0 m in the Großer Jasmunder Bodden and Z. noltii at 3.0 m in the Salzhaff. Thus, recent and modelled historical values of all three species do not differ, and recent distribution limits do not indicate an eutrophication-induced decrease in depth distributions of these species at their respective collection sites.

Phosphorus in sediments from coastal waters of Mecklenburg-Vorpommern(southern Baltic Sea)

Abstract The aim of this study was to investigate the seasonal and spatial gradients in thecontents of phosphorus and its bound forms in sediments of the Rassower Strom and the Kirr-Bucht (southern Baltic Sea). Sediment cores were collected in summer and autumn in 1996, and they were cut into layers 1 cm thick. With 9–11 g P/m 2 , the Kirr-Bucht showed a generally larger phosphorus pool. In overlaying waters, the effective phosphorus potential depends on the content of phosphorus as well as biochemical reactivity and sediment mobility. Biochemical reactivity was assessed by phosphorus fractionation in the present study. The contents of phosphorus easily available to algae were very low, with values of only 1% being recorded at both study sites. The phosphorus potentially available to algae in the Rassower Strom decreased from about 40% at the surface to 15–20% of total phosphorus at a depth of 10 cm. In the Kirr-Bucht, the values were 30–50% at the surface, and 7–14% of total phosphorus at a depth of 10 cm. Pore-water analyses show that, in the Rassower Strom, ortho-phosphate and total dissolved phosphorus concentrations were 10 times higher than values recorded in the Kirr-Bucht. The exchange between the pore water and the overlying water was characterized by sediment resuspension at these study sites.

Brackish water as an environment

1. Water is the most abundant compound on the surface of the Earth and the chemical basis for life on Earth. 2. The strong polarity of the water molecule assigns special physical and chemical properties to water as the direct environment in which aquatic organisms live, propagate and interact. 3. The surface tension of water creates the pleuston habitat and the viscosity of water requires adaptations, but it is also utilised by organisms for their life functions. 4. Water remains liquid over a broad range of temperatures, and the density anomaly of water makes ice float, which allows life to exist below the ice even when the water surface freezes. 5. In the brackish water of the Baltic Sea the ionic composition and the marine carbonate system deviate from marine water, which requires physiological adaptations of the organisms living in the Baltic Sea. 6. Natural brackish waters are classified according to ecologically relevant salinity ranges.

Transformation of particulate phosphorus at the sediment- water interface in a shallow coastal water on the Baltic Sea

Coastal waters are transitional zones between limnic waters and marine systems characterised by a morphological diversity, but also by a considerable natural variability of abiotic and biotic parameters. In addition to this high natural variation, coastal waters are subjected to extremely high anthropogenic impacts. Since the early 1960s, nutrient influx has increased from the catchment area of the coastallagoons on the German Baltic Coast. For the shallow coastallagoon DarB Zingst Bodden Chain (DZBC) on the southern Baltic Sea, the highest external phosphorus input was between 200 t a-1 and 300 t a-1 in the 1970s (SELIG et al. 2006). The input ofphosphorus and nitrogen was reduced in the 1990s by rebuilding of the wastewater treatment plants (BEHRENDT et al. 1999). Despite the reduced external nutrient inputs, no decrease in eutrophication or primary production could be documented. One reason is the high accumulation of nutrients, especially o f phosphorus, in the sediments. The P-release from the sediment was between 360 and 480 t a-1 for the DZBC (ScHLUNGBAUM et al. 2001). Today, the interna! P-load is higher than the external P-input of the coastallagoon; therefore, after the reduction of external nutrient input, the P-release and P-binding at the sediment-water interface play the dominant role in sustaining the eutrophication of the shallow coastallagoons. This study describes the seasonal variation of dissolved and particulate phosphorus in a shallow coastal lagoon. The particulate phosphorus in the water body, sediment traps, surface sediment layers, and sediment were characterised by sequential fractionation techniques. The field studies were complemented by laboratory experiments to identify the size frationation of phosphorus-bearing particles by sedimentation and resuspension processes.