Emil Rydin

Cultural Oligotrophication: Causes and Consequences for Fisheries Resources

Abstract Research on the impacts and processes of eutrophication has dominated limnological research for several decades, and it is only recently that implications of nutrient removal and declining ecosystem production (oligotrophication) on fisheries and food chains have been reported. To many persons, oligotrophication is synonymous with “clean”water and aesthetic improvements, but to others, it often implies an unproductive and declining fisheries resource. In this article we use a phosphorus (P) mass-balance approach to provide a historic perspective for the ongoing oligotrophication of highland terrestrial and aquatic ecosystems and the concurrent eutrophication of lowland, coastal ecosystems. Because mined sources of P for fertilizer production are declining and costs are likely to increase substantially within the next century, we opine that it is time to reconsider the ways we manage our nutrient resources. We should recommence all means of recycling P, and consider ways to reintroduce recycled nu...

Dosing Alum to Wisconsin Lake Sediments Based on in vitro Formation of Aluminum Bound Phosphate

ABSTRACT The dose of aluminum (Al) needed to deplete mobile inorganic sediment phosphorus (P) [loosely-sorbed P and Iron (Fe)-bound P] and transform it to Al-P was estimated in vitro in Lake Delavan, Wind Lake, and Bass Bay sediments. The formation of Al-P was logarithmically related to increased Al added as buffered alum. Results of the in vitro treatments were compared with the observed effect on sediment-P composition from the 1991 alum treatment (12 g Al·m−2) in Lake Delavan. That 1991 dose resulted in the formation of 2.2 g P·m−2, measured as Al-P, which was apparently the maximum amount of P that could be adsorbed with that alum dose. Based on in vitro alum additions, 150 g Al·m−2, twelve times that added, would have been required to nearly deplete mobile P in surface (0–4 cm) sediment of Lake Delavan (16 m). Wind Lake contained less mobile P, so a dose of 80 g Al·m−2 was required to remove mobile P in sediments from its deep hole (14m), while an addition of only 20 g Al·m−2 was needed for sediments...

Characterization of phosphorus in sequential extracts from lake sediments using 31P nuclear magnetic resonance spectroscopy

Phosphorus (P) compounds in three different lake surface sediments were extracted by sequential P extraction and identified by P-31 nuclear magnetic resonance (P-31 NMR) spectroscopy. The extractio ...

Release of Organic P Forms from Lake Sediments

The effects of different physical and chemical conditions on the decomposition and release of organic and inorganic P compound groups from the sediment of Lake Erken were investigated in a series of laboratory experiments. Conditions investigated were temperature, oxygen level, and the effects of additions of carbon substrate (glucose) and poison (formalin). The effects on the P compound groups were determined by measurements with (31)P NMR before and after the experiments, as well as analysis of P in effluent water throughout the experiment. Phosphate analysis of the effluent water showed that oxygen level was the most influential in terms of release rates, with the sediments under anoxic conditions generally releasing more phosphate than the other treatments. (31)P NMR showed that the various treatments did influence the P compound group composition of the sediment. In particular, the addition of glucose led to a decrease in orthophosphate and polyphosphate while the addition of formalin led to a decrease in phosphorus lipids, DNA-phosphate and polyphosphate. Oxic conditions resulted in an increase in polyphosphates, and anoxic conditions in a decrease in these. Temperature did not seem to affect the composition significantly.

Longevity and effectiveness of aluminum addition to reduce sediment phosphorus release and restore lake water quality.

114 lakes treated with aluminum (Al) salts to reduce internal phosphorus (P) loading were analyzed to identify factors driving longevity of post-treatment water quality improvements. Lakes varied greatly in morphology, applied Al dose, and other factors that may have affected overall treatment effectiveness. Treatment longevity based on declines in epilimnetic total P (TP) concentration averaged 11 years for all lakes (range of 0-45 years). When longevity estimates were used for lakes with improved conditions through the end of measurements, average longevity increased to 15 years. Significant differences in treatment longevity between deeper, stratified lakes (mean 21 years) and shallow, polymictic lakes (mean 5.7 years) were detected, indicating factors related to lake morphology are important for treatment success. A decision tree developed using a partition model suggested Al dose, Osgood index (OI, a morphological index), and watershed to lake area ratio (related to hydraulic residence time, WA:LA) were the most important variables determining treatment longevity. Multiple linear regression showed that Al dose, WA:LA, and OI explained 47, 32 and 3% respectively of the variation in treatment longevity. Other variables (too data limited to include in the analysis) also appeared to be of importance, including sediment P content to Al dose ratios and the presence of benthic feeding fish in shallow, polymictic lakes.

Bacterial and phosphorus dynamics in profundal Lake Erken sediments following the deposition of diatoms: a laboratory study

The benthic microbial response to the deposition of naturalseston and the microbial impact on nutrient dynamics wasstudied in an experimental system using whole sediment coresequipped with flow-through systems for the overlying water. For20 days, changes in sediment bacterial activity, totalmetabolic activity (heat production), bacterial biomass,phosphorus fractions and basic chemistry were followed, as wellas the exchange of nutrients between sediment and water.Microbial activity and biomass increased immediately inresponse to the deposition of seston, peaked after seven daysand then decreased linearly over the remaining time of theexperiment. Co-settled bacteria were suggested to play animportant role in the microbial response. Changes in bacterialbiomass production, bacterial biomass and the NaOH-nrPextractable phosphorus fraction were concurrent in response toseston additions. The sediment acted as a trap for SRP from theoverlying water when bacterial activity was high and as asource when the bacterial activity decreased. Altogether, theresults suggest an important role of bacteria in theregeneration of seston P. Mineralization rates estimated fromsediment heat production showed that ca. 11% of the addedseston carbon was oxidized in the sediments during theexperiment.

Geo-Engineering in Lakes-A Call for Consensus

A climate change researchers hotly debate the values and risks associated with atmospheric geo-engineering, aquatic ecologists are all too aware of a stark contrast between the two camps. Unlike proposals for atmospheric manipulations, geo-engineering in lakes and reservoirs using phosphorus(P)-removing materials has been implemented at a global scale as a eutrophication management tool for decades (Figure 1), in the absence of scientific consensus on its use. The technique, known as “P-capping”, can be used to control legacy P stores in bed sediments that have built up over decades of anthropogenic pollution. If left untreated, these legacy P stores can prolong water quality improvements for decades following catchment management. As well as accelerating recovery of nutrient-impacted waterbodies, geo-engineering is often considered in isolation of catchment nutrient management measures due to its low relative cost and ability to produce rapid short term improvements in water quality. However, many knowledge gaps exist with respect to the technique’s efficacy, and the scientific evidence is not yet available with which wide scale application can be supported. We argue that a comprehensive analysis of data and increased coherence across future geo-engineering research programs is necessary to deliver advances in theoretical and practical knowledge needed to improve the efficacy of the approach. With the recent introduction of water quality targets and deadlines for standing waters, e.g. as part of the EU Water Framework Directive (WFD) or the Clean Water Act in the United States, the scale of the geo-engineering debate in aquatic ecosystems is rapidly increasing. In the EU around 36% (i.e., 31,819 km total lake surface area; http://www.eea.europa.eu/ data-and-maps/data/wise_wfd) of all reported WFD lakes fail water quality targets based on ecological condition. The main driver of ecological deterioration in lakes within urban and rural catchments is P pollution, although it is unlikely that P will be the only pressure requiring management in most lakes. Given that current cost estimates of treating lakes with popular geoengineering products range between €0.3 million and €0.8 million per km lake surface area (i.e., for aluminum and lanthanum based products, respectively), it is important that the application of this technique be based on sound scientific understanding. Failure to achieve these water quality targets can attract significant financial penalties for water authorities and regulators. Of increasing concern is the lack of tested theory and empirical data upon which decisions of field-scale geoengineering in lakes can be based. This is due mainly to the rarity of long-term ecosystem scale experiments that are needed to produce the relevant data. For most of the waterbody scale trials conducted to date, the norm is that geo-engineering was selected by water managers for application and researchers find themselves trying to interpret the effects of the treatment based on a too-short preand post-treatment monitoring program. Such investigations do not capture long-term impacts on biota. In addition, data from ecosystem experiments that have adequate design are often confined to the gray literature and should be made available, and reports of failed applications are extremely rare. The ability of researchers to publish their findings is limited by the time taken for lakes to respond following perturbation and by the speed of the peer review process; single year observations can rarely be used to infer the longer term effects of such techniques. And so we find ourselves relying heavily on results from laboratory based experiments that may not reflect ecosystem scale responses. The understandable disconnects between the needs of product suppliers, water managers, researchers, regulators, and policy makers can be bridged through coherent and transparent analysis of existing and future data. Disconnects are manifest within a lack of consensus on how to assess the need for geo-engineering at the site-specific scale, the potential negative impacts of geo-engineering on lake ecology and biogeochemical cycling, the expected effective period of treatment, the physical and chemical conditions of receiving waterbodies that may retard operational performance of products, the methods of estimating effective dose and therefore cost of treatment, and appropriate application

RECRUITMENT AND PELAGIC GROWTH OF GLOEOTRICHIA ECHINULATA (CYANOPHYCEAE) IN LAKE ERKEN1

Different parameters in the life cycle of the colony forming cyanobacterium Gloeotrichia echinulata (J.E. Smith) Richter was evaluated in Lake Erken, Sweden. Recruitment of colonies from the sediments and pelagic abundance were measured during 2 years. These data were then used in a model to evaluate and estimate parameters of the life cycle. In our study, recruitment alone only contributed to a small part (<5%) of the maximum G. echinulata abundance that occurred during late summer. However, recruitment from shallow sediments forms the important seed for the pelagic population. Together with measured rates of migration from the sediment, variations in either pelagic colony division rate or pelagic residence time could explain variations in the measured abundance of G. echinulata in situ.

Phosphorus inactivation by aluminum in Lakes Gårdsjön and Härsvatten sediment during the industrial acidification period in Sweden

Acidification of lakes exposed to acid deposition is generally accompanied by a severe decrease in production (oligotrophication). In this study, we examined sediment from Lakes Gardsjon and Harsvatten, Sweden, to determine whether sediment phosphorus (P) retention increased during the years corresponding to lake acidification. Sediment from both lakes had increases in aluminum (Al) in the upper 10 cm, and dating of Lake Gardsjon sediment revealed that the Al increase occurred from 1950 to 2001 in this lake. The increase in Al input caused an increase inAl-bound P (Al–P) formation and overall sediment total phosphorus retention during the same period. Lake Gardsjon received an additional 12.9 g·m–2 of Al, above preacidification background levels, that bound 1.1 g·m–2 of P and removed it from the in-lake P cycle from 1950 to 2001. A substantial portion (up to 76%) of the total external P load eventually was converted to Al–P and buried in the sediment over this period. The increase in sediment P burial due to increased formation of Al–P in systems similar to Lake Gardsjon may have detrimental effects on nutrient cycling, and as a result, on productivity within the lake, leading to acido-oligotrophication.

Diagenesis of settling seston : identity and transformations of organic phosphorus

Solution (31)phosphorus NMR spectroscopy and sequential fractionation were used to follow diagenetic changes in phosphorus forms during decomposition of settling seston in Lake Nordborg, a shallow eutrophic lake in Denmark. In a decomposition experiment, seston released >60% of their total phosphorus during ~50 days incubation, although seston collected during summer contained more phosphorus and released it over a longer period compared to seston collected during spring. Seston decomposition increased concentrations of potentially bioavailable polyphosphate and phosphodiesters, but also promoted the formation of refractory phosphorus forms that might be buried permanently in the sediment. Combining these results with in situ measurements of phosphorus concentrations in lake water and sediment traps revealed that the release from settling seston plays only a minor role in the accumulation of phosphorus in the hypolimnion of Lake Nordborg.