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  • 1
    Electronic Resource
    Electronic Resource
    The spring development of phytoplankton in Lake Erken (1977)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 7 (1977), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. In Lake Erken there is a regular phytoplankton peak at ice-breakup in the spring. Pechlaner (1970) studied the spring outburst of 1960. We carried out a similar study in 1973, when the climatic factors were completely different, with only 10 cm of ice and almost no snow. Thus, due to light penetration, there was a high phytoplankton biomass under the ice as early as March. Stephanodiscus astraea (Ehr.) Grun. and Asterionella formosa Hass. dominated the biomass during the spring development in 1973 instead of the normally dominating S. hantzschii v. pusillus Grun.The nutrient decrease was slower in 1973 than in 1960. A comparison of carbon assimilation and the decrease of nitrate and phosphate indicate sufficient nutrient supply in 1973. In 1960, the population grew logarithmically until the nutrients became limiting. In 1973, the average biomass was greater, but the mean probable primary production was only half that of 1960. From the activity coefficients for the 2 years it is also clear that, in 1960, S. hantzschii v. pusillus was highly productive during its short but intensive growth period. Its minute size and high surface/volume ratio enabled it to take up nutrients rapidly and efficiently. The chlorophyll content of S. astraea in 1973 was only half as much as that of S. hantzschii v. pusillus in 1960. Since the light conditions under the ice in March 1973 were more unfavourable than during the exponential phase of 1960, production was much lower.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1977.tb01680.x
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  • 2
    Electronic Resource
    Electronic Resource
    Spatial and temporal variation in the biomass and nutrient status of epilithic algae in Lake Erken, Sweden (2002)
    Oxford UK : Blackwell Science Ltd
    Freshwater biology 47 (2002), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The aim of this study was to estimate patchiness in biomass and in the internal nutrient status of benthic algae on hard substrata (epilithon) in Lake Erken, Sweden, over different levels of distance, depth and time. Knowledge of the sources and scale of patchiness should enable more precise estimation of epilithic biomass and nutrient status for the entire lake. We focused on the horizontal scale, about which little is known.2. We sampled epilithon by SCUBA diving and used a hierarchical sampling design with different horizontal scales (cm, dm, 10 m, km) which were nested in two temporal scales (within and between seasons). We also compared two successive years and three sampling depths (0, 1 and 4 m). Biomass was measured as particulate carbon and chlorophyll a (Chl a) and internal nutrient status as carbon : nitrogen : phosphorus (C : N : P) ratios and as specific alkaline phosphatase activity (APA).3. Horizontal variation accounted for 60–80 and 7–70% of the total variation in biomass and in nutrient status, respectively, at all depths and during both years. Both small and large scales accounted for significant variation. We also found variation with time and depth. Biomass increased in autumn after a summer minimum, and the within-season variation was very high. The lowest biomass was found at 0 m depth. Both N and P limitation occurred, being higher in 1996 than in 1997 and decreased with depth.4. As a consequence, any sampling design must address variation with distance, depth and time when estimating biomass or nutrient limitation of benthic algae for an entire lake. Based on this analysis, we calculated an optimal sampling design for detecting change in the epilithic biomass of Lake Erken between different sampling days. It is important to repeat the sampling as often as possible, but also the large scales (10 m and km) and the dm scale should be replicated. Using our calculations as an example, and after a pilot study, an optimal sampling design can be computed for various objectives and for any lake.5. Short-term impact of the wind, light and nutrient limitation, and grazing, might be important in regulating the biomass and nutrient status of epilithic algae in Lake Erken. Patchiness in the nutrient status of algae was not coupled to the patchiness of biomass, indicating that internal nutrients and biomass were regulated by different factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2002.00844.x
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanisms for internal loading of phosphorus in lakes (1998)
    Springer
    Hydrobiologia 373-374 (1998), S. 21-25 
    Details
    ISSN: 1573-5117
    Keywords: internal loading ; phosphorus ; fractionation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake sediments play an important role in the phosphorus metabolism in lakes. The impact depends on the tendencies to retain and to release phosphorus.The internal loading will often determine the eutrophication status of the lake and the time lag for recovery after reduction of the external loading. Internal loading is most important during the summer. The potential source of phosphorus in the surficial sediments is very large in comparison to the pools in the water column. This means that even if only a very small amount is released, it will have significant impact on the phosphorus concentration in the lake water. The distribution of phosphorus forms in sediments have been investigated since the 1950s. Generally, vertical profiles of sediment phosphorus content, expressed on dry weight basis, show an increasing total content towards the sediment surface. The vertical profile continues up into the water when looking at the particulate matter. A number of environmental factors are important in the mobilisation processes. Most studies indicate that sediment bacteria have a significant role in uptake, storage and release of phosphorus including anaerobic release of iron-bound phosphorus. Several phytoplankton species have resting stages overwintering on the sediment. When growth is induced, they leave their habitat in order to shift their life-form to a pelagic one. In Lake Erken the cyanobacteria Gloeotrichia echinulata has been shown to contribute significantly to the internal loading of phosphorus during the summer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017011420035
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  • 4
    Electronic Resource
    Electronic Resource
    Temporal changes in biomass specific photosynthesis during the summer: regulation by environmental factors and the importance of phytoplankton succession (1992)
    Springer
    Hydrobiologia 243-244 (1992), S. 119-135 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Measurements of phytoplankton photosynthesis vs. irradiance relationships have been made at 3–7 day intervals in Lake Erken (central Sweden) for three years during summer stratification. Both the rate of light-limited (αB) and light-saturated (Pmax B) photosynthesis per unit chlorophyll a showed distinct and similar temporal trends in each year. Seasonal trends were especially evident for Pmax B, which increased in value for several weeks following the onset of thermal stratification, and then declined in the presence of the large colonial blue-green alga, Gloeotrichia echinulata. By late summer, when the biomass of G. echinulata had decreased, Pmax B again rose to its early summer value. The covariation of biomass-specific photosynthesis with the blooming of G. echinulata was the one clear seasonal (week-month) pattern which emerged in each of 3 years. Over short (day-week) time scales, changes in αB were related to changes in irradiance exposure on the day of sampling. However, the relationship between these two parameters was variable in time, since it was superimposed upon longer term trends controlled by changes in phytoplankton species composition. Increases in G. echinulata biomass corresponded with a deepening of the thermocline, which both increased internal phosphorus loading and the transport of resting G. echinulata colonies into the epilimnion. The timing and magnitude of the yearly G. echinulata bloom was as a result related to the seasonal development of thermal stratification. These results illustrate the importance of seasonal changes in the phytoplankton community as a factor regulating rates of biomass specific photosynthesis, particularly when the successional changes involve species with very different life strategies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007027
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  • 5
    Electronic Resource
    Electronic Resource
    The influence of nitrate on the phosphorus flux to and from oxygen depleted lake sediments (1985)
    Springer
    Hydrobiologia 120 (1985), S. 207-223 
    Details
    ISSN: 1573-5117
    Keywords: nitrate ; phosphorus ; denitrification ; fractionation ; sediment ; anaerobic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Addition of nitrate to an oxygen depleted sediment leads to a stimulation of the mineralization process if a major part of the nitrate is dissimilatorily reduced. This may cause an increased release of phosphate from some sediments. Nitrate, however, maintains a high redox potential at the sediment surface and thus prevents a release of iron-bound phosphorus. These two counteracting effects of nitrate addition to sediment-water systems were demonstrated in laboratory experiments. A high supply of nitrate to a phosphorus-saturated sediment caused an increased release of phosphate and ammonium once the nitrate had been used up. However, from other sediments there was no or very little release of phosphate but an increased release of ammonium caused by high nitrate dissimilation, probably due to the very high capacity of these sediments to bind liberated phosphate or due to storage of phosphorus in an increased bacterial biomass. Phosphorus fractionation, before and after the experiments with the sediments, provided information on transfers to, from and within the sediments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00045164
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  • 6
    Electronic Resource
    Electronic Resource
    Analytical determination of orthophosphate in water (1988)
    Springer
    Hydrobiologia 170 (1988), S. 45-59 
    Details
    ISSN: 1573-5117
    Keywords: orthophosphate ; determination ; methods ; interferences ; molybdate ; enzymatic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methods for orthophosphate determination and the problems of interferences are reviewed. An important group of methods utilizes the phosphomolybdate complex. The complexation step, the reduction step and the extraction step are treated separately and alternative procedures compared. Another group of methods uses ion association complexes; they are primarily used in physiology and not commonly used in water analyses today. Enzymatic methods for orthophosphate analysis in natural waters have been developed lately and are ready for application in selected waterbodies. Flame spectroscopic, fluorometric, gas chromatographic, ion exclusion chromatographic, inductively coupled plasma and other methods are also shortly presented. Radiobiological bioassays for orthophosphate are also available. In conclusion it was emphasized that the most common and reliable technique still is the molybdenum blue method as modified by Murphy & Riley (1962). The need for more specific and sensitive methods is particularly strong in investigations of phosphorus turnover and phosphorus limitation in natural waters. For these purposes the enzymatic phosphatase methods has advantages due to their specificity for orthophosphate and they might offer an alternative to the molybdenum blue method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024898
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  • 7
    Electronic Resource
    Electronic Resource
    Phosphorus in sediments — speciation and analysis (1988)
    Springer
    Hydrobiologia 170 (1988), S. 91-101 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; sediments ; fractionation ; forms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Characterization of sediment phosphorus is commonly based on sequential chemical extractions, in which phosphorus is supposed to be selectively removed from different compounds in the sediments. The first extraction schemes were designed to quantify discrete chemical or mineralogical compounds. As extraction schemes have been tested on different sediments, several systematic errors have been detected and the schemes have been modified and simplified accordingly. Other chemical extractions or treatments have attempted to determine phosphorus bound to particles with a certain strength or binding energy, the purpose being to determine the labile, loosely bound, exchangeable, mobile or algal-available fraction of sediment phosphorus. All extraction procedures yield operationally defined fractions and cannot be used for identification of discrete phosphorus compounds. The many methodological modifications make it necessary to be cautious when comparing results from the literature in this field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024900
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  • 8
    Electronic Resource
    Electronic Resource
    Phosphorus composition and release in sediment bacteria of the genus Pseudomonas during aerobic and anaerobic conditions (1993)
    Springer
    Hydrobiologia 253 (1993), S. 131-140 
    Details
    ISSN: 1573-5117
    Keywords: pseudomonas ; sequential fractionation ; bacterial P composition ; bacterial P release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A substantial amount of sediment phosphorus can be bound in bacterial biomass. In this study the fractional composition of phosphorus in the bacteria Pseudomonas was determined by sequential extraction with ammonium chloride, sodium hydroxide and hydrochloric acid according to the scheme of Hieltjes & Lijklema (1980). Both non-labelled and 32P-labelled bacteria were used for fractionation. Up to 80% of the bacterial phosphorus was found in the NaOH-nRP fraction, which is in agreement with the results of Hupfer & Uhlman (1992) for Acinetobacter and activated sludge obtained with the sequential extraction scheme of Psenner et al. (1985). A significant correlation was found between bacterial biomass and the amount of phosphorus retained in the NaOH-nRP fraction when sediments were fractionated. Additional experiments with 32P-labelled Pseudomonas in sediment-water systems were performed in order to follow bacterial release of phosphorus under aerobic and anaerobic conditions. These studies did not sustain the hypothesis that anaerobic conditions lead to rapid release of phosphorus from bacterial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00050733
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  • 9
    Electronic Resource
    Electronic Resource
    Phosphatases; origin, characteristics and function in lakes (1988)
    Springer
    Hydrobiologia 170 (1988), S. 157-175 
    Details
    ISSN: 1573-5117
    Keywords: phosphatases ; phosphate ester ; phosphorus deficiency ; phosphate regeneration ; lake water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phosphatases catalyze the liberation of orthophosphate from organic phosphorus compounds. The total phosphatase activity in lake water results from a mixture of phosphatases localized on the cell surfaces of algae and bacteria and from dissolved enzymes supplied by autolysis or excretion from algae, bacteria and zooplankton. External lake water phosphatases usually have pH optima in the alkaline region. Acid phosphatases generally seem to be active in the internal cell metabolism. The synthesis of external alkaline phosphatases is often repressed at high phosphate concentrations and derepressed at low phosphate concentrations. Phosphatase activity has therefore been used as a phosphorus deficiency indicator in algae and in natural plankton populations. The possibilities for this interpretation of phosphatase activity in lake water are limited, however, and this is discussed. The in situ hydrolysis capacity, i.e. the rate by which orthophosphate is released from natural substrates, is unknown. However, we advocate that this process is important and that the rate of substrate supply, rather than phosphatase activity, limits the enzymatic phosphate regeneration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024903
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  • 10
    Electronic Resource
    Electronic Resource
    The role of Gloeotrichia echinulata in the transfer of phosphorus from sediments to water in Lake Erken (1993)
    Springer
    Hydrobiologia 253 (1993), S. 123-129 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; cyanobacteria ; Gloeotrichia echinulata ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The abundance of Gloeotrichia echinulata colonies in the sediments of Lake Erken and their phosphorus content were investigated to determine the contribution of Gloeotrichia colonies to total sediment phosphorus. Moreover, the potential size of the algal inoculum and the migration to the water during summer were estimated. The surplus phosphorus content of the resting colonies in the sediment was about 45% of total phosphorus, which maximized at 8.5 µg P (mg dw)−1 or 81 ng P colony−1. The C:P ratio (by weight) in the early colonies appearing in the lake water was 50:1, while the ratio stabilized at 150 during the major migration period. The internal supply of surplus phosphorus was used during the pelagic growth of the colonies. The internal phosphorus loading to the epilimnion of Lake Erken due to Gloeotrichia migration could, from the measurements of the increase in particulate epilimnetic phosphorus, be estimated at 40 mg P m −2 or 2.5 mg P m−2 d−1 in late July and early August. Determination of the number of colonies in the sediment before and during the migration verified this value to be a conservative estimate of the internal phosphorus loading due to Gloeotrichia migration to the epilimnion in Lake Erken. The sediment P content calculated from the P concentration in early epilimnion colonies resulted in a value of 35 µg P (g dw)−1 as a maximum. This corresponds to only 3% of the total phosphorus content in Lake Erken sediment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00050732
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