| 1. |
- Adler, Sven
(author)
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Identifying reference conditions for dimictic north German lowland lakes: implications from paleoecological studies for implementing the EU-Water Framework Directive
- 2015
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 742, s. 295-312
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Journal article (peer-reviewed)abstract
- Using published paleolimnological results from 14 dimictic calcareous lakes, this study identifies total phosphorous (TP) reference values for the European lake type CB 1. The initial increase in settlement-associated pollen occurred in the catchments between ad similar to 1000 and similar to 1820. A departure from diatom-inferred TP reference conditions occurred during periods of increased human activities during Early to Late Medieval Times (ad similar to 1110-1325; four lakes), early Modern Times (ad similar to 1575-1600; two lakes), after the 30 years' war (> ad 1650; two lakes) and during the Anthropocene (after ad similar to 1850, three lakes). Only one lake continuously has TP reference values until recent days, whilst TP reference values could not be detected in two cases. Thus, we refrain from setting a fixed point in time for defining reference conditions for lakes in the European Central Plains. This study also validates TP reference levels calculated based on common lake models for CB 1-lakes and assesses the range of TP reference levels using paleolimnological diatom studies. The highly variable diatom-inferred TP reference levels only partly support the modelled levels. Thus, we recommend using two subtypes (CB 1a and 1b), based on the watershed to volume ratio to better meet the requirements of lake type-specific reference levels.
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| 2. |
- Ahlgren, Johan, et al.
(author)
-
The influence of predator regime on the behaviour and mortality of a freshwater amphipod, Gammarus pulex
- 2011
-
In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 671:1, s. 39-49
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Journal article (peer-reviewed)abstract
- In species with restricted dispersal, traits may become genetically fixed leading to local adaptations. Therefore, predator avoidance in a prey species may differ between populations experiencing different predator regimes, but also between sexes within a population due to different vulnerability to predators. In this study we used male and female Gammarus pulex from two different predator regimes: fishless ponds, where invertebrates are the dominant predators and ponds with predatory fish. In the laboratory we examined refuge use, mortality, leaf decomposition rate and pair-formation in G. pulex when exposed to predator cues from either invertebrate predators or fish. Individuals from fish ponds spent more time in refuge and had a higher mortality than those from fishless ponds independent of predator cues. There was no effect of pond predator regime or predator cues on leaf decomposition rates. Further, fewer individuals formed pairs in G. pulex from fish ponds than from fishless ponds. Male G. pulex had a higher mortality and a higher decomposition rate than females independent of predator cues. However, there was no difference in refuge use between sexes. Our study shows that there are general differences in behaviour traits, both between predator regimes and sexes in G. pulex.
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| 3. |
- Al Jawaheri, Raad, et al.
(author)
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Negative impact of lake liming programmes on the species richness of dragonflies (Odonata) : a study from southern Sweden
- 2017
-
In: Hydrobiologia. - Dordrecht : Springer Netherlands. - 0018-8158 .- 1573-5117. ; 788:1, s. 99-113
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Journal article (peer-reviewed)abstract
- Liming programmes aiming to restore fish populations are being implemented in many acidified aquatic systems in northern Europe. We studied Odonata communities in 47 forest lakes in SW Sweden, 13 that are currently being limed, and 8 that have previously been limed. Thirty-one species were recorded, with the highest mean number in untreated lakes, followed by previously treated lakes and currently treated lakes. Species communities differed between untreated and limed lakes, but only few rare species found in the untreated lakes were absent in the treated lakes. Likewise, species known to thrive in acid environments were either rare or showed no preferences. Comparing the number of records of odonate species within a large regional area to the proportion of lakes inhabited in our study, we found that seven of the most commonly observed species occurred less frequently in limed lakes than in the untreated ones, including two of the three most common taxa. Reduced species numbers in limed lakes might be due to conditions on other trophic levels, including fish predation. We argue that Odonata should be considered when developing new biological indices of water quality, although the causes of the observed occurrence patterns need to be studied further. © 2016 Springer International Publishing Switzerland
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| 4. |
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| 5. |
- Andersson, A, et al.
(author)
-
Effect of nutrient enrichment on the distribution and sedimentation of polychlorinated biphenyls (PCBs) in seawater
- 1998
-
In: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 377, s. 45-56
-
Journal article (peer-reviewed)abstract
- The effect of nutrient enrichment on the distribution of polychlorinated biphenyl's (PCBs) in the microbial food web and the residence time of PCBs in seawater was studied in an experimental mesocosm system. Two 5 m high temperature and light controlled mesocosm tubes (empty set = 0.5 m) were filled with seawater from the northern Baltic Sea. Inorganic phosphorus and nitrogen were added daily to one mesocosm, while the other served as a control. Experiments were conducted at 5, 10 and 20 degrees C. Three C-14-labelled PCBs of different degree of chlorination were added to subsamples of the mesocosms: 4-chlorobiphenyl (MCB), IUPAC # 3, 2,2',5,5'-tetrachlorobiphenyl (TCB), IUPAC # 52 and 2,2',4,4',5,5'-hexachlorobiphenyl (HCB) IUPAC # 153. The biomasses and growth rates of the microorganisms as well as the sedimentation rate of particulate organic material increased with nutrient enrichment. The size distribution of the microorganisms changed with nutrient status, from dominance of picoplankton (< 2 mu m) in the control towards increased importance of micro (> 10 mu m) and nanoplankton (2-10 mu m) in nutrient enrichment. The specific growth rate of the bacterial community was found to be more temperature dependent than that of the phytoplankton community. The relative proportion of PCBs in the > 2 mu m fraction was observed to be in the order MCB < TCB < HCB, while the opposite distribution prevailed in the < 2 mu m fraction. We hypothesize that this is due to the combined effect of the different K-ow values of the PCBs and a different composition of the particulate organic carbon in the > 2 mu m and < 2 mu m fractions (e.g. different lipid composition). The residence time of the PCBs in the mesocosm generally decreased with nutrient enrichment, but was dependent on the degree of chlorination of the PCB. Our results indicate that the transport of organic pollutants up through the food web is more important in nutrient poor than in nutrient rich waters and that the importance of sedimentation is higher in eutrophic ecosystems.
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| 6. |
- Andersson, Per, et al.
(author)
-
Sulphur isotope ratios in sulphate and oxygen isotopes in water from a small watershed in central Sweden
- 1992
-
In: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 235-236:1, s. 205-217
-
Journal article (peer-reviewed)abstract
- During 1988-89 water samples for sulphur and oxygen isotope measurements were collected in the Lake Mjösjön watershed (7.3 km2), central Sweden. Samples included: precipitation, throughfall, lakewater, shallow groundwater and inlet and outlet streams. The δ34S of sulphate in precipitation ranged from + 6.41‰ in winter to + 3.88‰ in summer, the higher winter values attributed to seasonal differences in the kinetic and equilibrium isotope fractionation during oxidation of atmospheric sulphur dioxide to sulphate. The δ34S in rain samples and in pine and spruce throughfall were similar, indicating no gain of sulphur from the trees. In the inflowing stream, the δ34S value increased as discharge decreased, from + 5.57‰ in spring to + 26.21‰ in summer, indicating bacterial sulphate reduction. The fluctuations in the inlet water were damped by the lake and in the outlet water, only a small decrease in the δ34S value during spring discharge was observed. During winter 1988-89, the near surface waters in the lake showed the same δ34S as snow indicating that meltwater governs the isotopic composition. During the winter, the δ34S in the near bottom waters increased while oxygen decreased due to bacterial sulphate reduction in the sediments. This also caused an increase in the alkalinity in the near bottom waters. Based on the δ18O data the water within the watershed is derived largely from meteoric water. During spring discharge, meltwater governs the inflow and outflow stream while additional groundwater influences occurred during the drier period. Most sulphur is derived from atmospheric deposition and the δ34S in sulphate increased during passage through the watershed due to bacterial sulphate reduction.
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| 7. |
- Arnott, Russell N., et al.
(author)
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Artificially generated turbulence : a review of phycological nanocosm, microcosm, and mesocosm experiments
- 2021
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In: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117. ; 848, s. 961-991
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Research review (peer-reviewed)abstract
- Building on a summary of how turbulence influences biological systems, we reviewed key phytoplankton-turbulence laboratory experiments (after Peters and Redondo in Scientia Marina: Lectures on plankton and turbulence, International Centre for Coastal Resources, Barcelona, 1997) and Peters and Marrase (Marine Ecology Progress Series 205:291-306, 2000) to provide a current overview of artificial turbulence generation methods and quantification techniques. This review found that most phytoplankton studies using artificial turbulence feature some form of quantification of turbulence; it is recommended to use turbulent dissipation rates (epsilon) for consistency with physical oceanographic and limnological observations. Grid-generated turbulence is the dominant method used to generate artificial turbulence with most experiments providing quantified epsilon values. Couette cylinders are also commonly used due to the ease of quantification, albeit as shear rates not epsilon. Dinoflagellates were the primary phytoplanktonic group studied due to their propensity for forming harmful algal blooms (HAB) as well as their apparent sensitivity to turbulence. This study found that a majority of experimental setups are made from acrylate plastics that could emit toxins as these materials degrade under UV light. Furthermore, most cosm systems studied were not sufficiently large to accommodate the full range of turbulent length scales, omitting larger vertical overturns. Recognising that phytoplankton-turbulence interactions are extremely complex, the continued promotion of more interdisciplinary studies is recommended.
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| 8. |
- Baho, Didier Ludovic, et al.
(author)
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The influence of nutrient loading, climate and water depth on nitrogen and phosphorus loss in shallow lakes: a pan- European mesocosm experiment
- 2016
-
In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 778, s. 13-32
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Journal article (peer-reviewed)abstract
- Losses of phosphorus (P) and nitrogen (N) have important influences on in-lake concentrations and nutrient loading to downstream ecosystems. We performed a series of mesocosm experiments along a latitudinal gradient from Sweden to Greece to investigate the factors influencing N and P loss under different climatic conditions. In six countries, a standardised mesocosm experiment with two water depths and two nutrient levels was conducted concurrently between May and November 2011. Our results showed external nutrient loading to be of key importance for N and P loss in all countries. Almost all dissolved inorganic nitrogen (DIN) and soluble reac-tive phosphorus (SRP) were lost or taken up in biomass in all mesocosms. We found no consistent effect of temperature on DIN and SRP loss but a significant, though weak, negative effect of temperature on total nitrogen (TN) and total phosphorus (TP) loss in the deeper mesocosms, probably related to higher organic N and P accumulation in the water in the warmer countries. In shallow mesocosms, a positive trend in TN and TP loss with increasing temperature was observed, most likely related to macrophyte growth.
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| 9. |
- Bakker, Elisabeth S., et al.
(author)
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Restoring macrophyte diversity in shallow temperate lakes : biotic versus abiotic constraints
- 2013
-
In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 710:1, s. 23-37
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Journal article (peer-reviewed)abstract
- Although many lake restoration projects have led to decreased nutrient loads and increased water transparency, the establishment or expansion of macrophytes does not immediately follow the improved abiotic conditions and it is often unclear whether vegetation with high macrophyte diversity will return. We provide an overview of the potential bottlenecks for restoration of submerged macrophyte vegetation with a high biodiversity and focus on the biotic factors, including the availability of propagules, herbivory, plant competition and the role of remnant populations. We found that the potential for restoration in many lakes is large when clear water conditions are met, even though the macrophyte community composition of the early 1900s, the start of human-induced large-scale eutrophication in Northwestern Europe, could not be restored. However, emerging charophytes and species rich vegetation are often lost due to competition with eutrophic species. Disturbances such as herbivory can limit dominance by eutrophic species and improve macrophyte diversity. We conclude that it is imperative to study the role of propagule availability more closely as well as the biotic interactions including herbivory and plant competition. After abiotic conditions are met, these will further determine macrophyte diversity and define what exactly can be restored and what not.
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| 10. |
- Belle, Simon, et al.
(author)
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Acidification of freshwater lakes in Scandinavia: impacts and recovery of chironomid communities under accelerating environmental changes
- 2024
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In: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 851, s. 585-600
-
Journal article (peer-reviewed)abstract
- We re-examined the effects of acidification on Scandinavian freshwater lakes using paleolimnological reconstructions focused on subfossil chironomids. Our study showed a widespread shift in chironomid community composition occurring at around 1960 and corresponding with the maximum fallout of anthropogenic SO42- deposition. Results also showed that taxonomic turn-over was higher in chironomid records from nitrogen-limited lakes, likely due to the cumulative effects of acidification and eutrophication driven by atmospheric nitrogen deposition. Despite strong evidence of chemical recovery from acidification, all lake records failed to show a return to pre-acidified community compositions and most chironomid communities instead continue to follow the trajectories triggered by acidification. We hypothesized that when SO42- deposition started to decrease after 1980, a period also marked by rapid environmental and climatic changes, the influence of pH and/or other acidification-related variables in structuring chironomid community became less important, thus, giving more relative importance to other drivers, such as brownification and climatic processes. Results, therefore, suggest the key role of acidification in shaping the response of chironomid communities to future environmental changes. Future paleolimnological studies will contribute to better manage aquatic ecosystems recovering from acidification worldwide by allowing managers to quantify the efficacy of different management actions taken to mitigate acidification as well as to redefine appropriate restoration targets.
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| 11. |
- Belle, Simon, et al.
(author)
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Effects of temperature on food isotopic integrity and trophic fractionation in Chironomus riparius in laboratory experiments
- 2020
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 847, s. 1257-1267
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Journal article (peer-reviewed)abstract
- Our experimental study was designed to assess the effects of temperature on food isotopic integrity and trophic fractionations (of carbon and nitrogen stable isotopes: Delta C-13 and Delta N-15) in chironomid larvae. A laboratory experiment was run using Chironomus riparius larvae at 15, 18 and 23 degrees C, and under three pulverized food resources. There were significant changes in the stable isotopic composition of the uneaten food, revealing the difficulty of preventing food microbial degradation in rearing experiments. C/N ratios of chironomid larvae were also affected by temperature, regardless of the food resource, suggesting changes in lipid contents and associated effects on the larval delta C-13 values. Therefore, differences in calculation methods (with vs. without lipid normalizations, fresh vs. old food isotopic baselines) induced large variability in Delta C-13 and Delta N-15 values, but our trophic fractionation estimates were similar to those previously reported in literature. Therefore, we conclude that temperature is not a major driver of the variability in trophic fractionations for chironomid larvae, and stable isotope composition of aquatic consumers can be used in food webs studies under changing temperature conditions. Variability in trophic fractionation estimates should, however, be considered to avoid misinterpretations of food web structure.
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| 12. |
- Belle, Simon
(author)
-
Glacier dynamics influenced carbon flows through lake food webs: evidence from a chironomid delta δ13C-based reconstruction in the Nepalese Himalayas
- 2018
-
In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 809, s. 285-295
-
Journal article (peer-reviewed)abstract
- Using a sediment core covering the last 3,500 years, we analysed photosynthetic pigments' concentrations in lake sediments and carbon stable isotopic composition of chironomid (Diptera, Chironomidae) remains (delta C-13(HC)). We aimed to reconstruct temporal changes in aquatic primary productivity and carbon resources sustaining chironomid larvae in a high mountain lake (Lake Pyramid Inferior; 5,067 m a.s.l.) located in the Nepalese Himalayas. Both pigments and delta C-13(HC) trends followed a similar fluctuating pattern over time, and we found significant positive relationships between these proxies, suggesting the strong reliance of benthic consumers on the aquatic primary production. Temporal trends matched well with main known climatic phases in the Eastern part of the Himalayan Mountains. Past glacier dynamics and associated in-lake solute concentrations appeared to be the main driver of autochthonous primary productivity, suggesting then the indirect impact of climate change on carbon processing in the benthic food web. During warm periods, the glacier retreat induced a rise in in-lake solute concentrations leading to an increasing primary productivity. Complementary investigations are still needed to strengthen our understanding about the response of past aquatic carbon cycling in CO2-limiting environments.
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| 13. |
- Belle, Simon, et al.
(author)
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Unravelling chironomid biodiversity response to climate change in subarctic lakes across temporal and spatial scales
- 2022
-
In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 849, s. 2621-2633
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Journal article (peer-reviewed)abstract
- We combined paleolimnological reconstructions and space-for-time substitutions to unravel chironomid biodiversity responses to climate change in subarctic mountains across temporal and spatial scales. Using sediment records, we found that long-term temporal changes in chironomid taxonomic diversity were mainly induced by the temperature tolerance/optimum of species, while little changes in functional diversity were found due to the replacement of similar functional-type taxa within the community. Overall, paleolimnological reconstructions suggested the selection of larger chironomid species by long-term climate cooling and little changes in trophic guilds. Space-for-time substitutions showed, however that low-elevation lakes with forested have more sediment-feeding taxa and larger larvae than high-elevation lakes, thus, suggesting the selection of large chironomid morphotypes with a sediment-feeding mode under warmer climate. Space-for-time substitutions and paleolimnological reconstructions, therefore, gave contrasting results for the link between climate and functional diversity of chironomid communities, likely because space-for-time substitutions failed to match the extent of both spatial and temporal climatic gradients. We suggest that future studies must address biodiversity issues across both temporal and spatial scales as an improved understanding of biodiversity responses to climate change may help us to understand how biodiversity will be affected by ongoing and future change.
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| 14. |
- Bengtsson, Mia M., et al.
(author)
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Interactive effects on organic matter processing from soils to the ocean : are priming effects relevant in aquatic ecosystems?
- 2018
-
In: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117. ; 822:1, s. 1-17
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Research review (peer-reviewed)abstract
- Organic matter (OM) is degraded during transport from soils to oceans. However, there are spatial and temporal variabilities along the aquatic continuum, which hamper the development of carbon cycling models. One concept that has been applied in this context is the priming effect (PE), describing non-additive effects on OM degradation after mixing sources of contrasting bioavailability. Studies on the aquatic PE report divergent results from positive (increased OM degradation rates) to neutral, to negative (decreased OM degradation rates) effects upon mixing. Here, we aim to condense the outcomes of these studies on aquatic PE. Based on a literature review, we discuss differences in the reported PEs across freshwater and marine ecosystems, identifying system-specific features that could favour non-additive effects on OM degradation. Using a quantitative meta-analysis approach, we evaluated the occurrence, direction (positive vs. negative) and magnitude of aquatic PE. The meta-analysis revealed a mean PE of 12.6%, which was not significantly different from zero across studies. Hence, mixing of contrasting OM sources in aquatic ecosystems does not necessarily result in a change in OM degradation rates. Therefore, we suggest to focus on molecular and microbial diversity and function, which could provide a better mechanistic understanding of processes driving OM interactions.
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| 15. |
- Bergfur, Jenny, et al.
(author)
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Effects of nutrient enrichment on C and N stable isotope ratios of invertebrates, fish and their food resources in boreal streams
- 2009
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In: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117. ; 628, s. 67-79
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Journal article (peer-reviewed)abstract
- Carbon and nitrogen stable isotopes are frequently used to study energy sources and food web structure in ecosystems, and more recently, to study the effects of anthropogenic stress on aquatic ecosystems. We investigated the effect of nutrient enrichment on d13C and d15N in fine (FPOM), coarse (CPOM) particulate organic matter, periphyton, invertebrates and fish in nine boreal streams in south-central Sweden. In addition, we analysed the diet of benthic consumers using stable isotope data. Increases in d15N of periphyton (R2 = 0.88), CPOM (0.78), invertebrates (0.92) and fish (0.89) were related to nutrient enrichment. In contrast, d13C signatures did not change along the nutrient gradient. Our results show that d15N has potential as a sensitive indicator of nutrient enrichment in boreal streams. Carbon and nitrogen isotopes failed to elucidate putative diets of selected aquatic consumers. Indeed, comparison of low- and high-impact sites showed that d13C of many consumers were found outside the ranges of basal resource d13C. Moreover, ranges of basal resource d13C and d15N overlapped at both low and high sites, making discrimination between the importance of allochthonous and autochthonous production difficult. Our findings show that a fractionation rate of 3.4% is not always be appropriate to assess trophic interactions, suggesting that more studies are needed on fractionation rates along gradients of impairment.
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| 16. |
- Bergström, Ann-Kristin, 1968-, et al.
(author)
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Effects of nitrogen enrichment on zooplankton biomass and N:P recycling ratios across a DOC gradient in northern-latitude lakes
- 2021
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In: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117. ; 848:21, s. 4991-5010
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Journal article (peer-reviewed)abstract
- We used data from whole-lake studies to assess how changes in food quantity (phytoplankton biomass) and quality (phytoplankton community composition, seston C:P and N:P) with N fertilization affect zooplankton biomass, community composition and C:N:P stoichiometry, and their N:P recycling ratio along a gradient in lake DOC concentrations. We found that despite major differences in phytoplankton biomass with DOC (unimodal distributions, especially with N fertilization), no major differences in zooplankton biomass were detectable. Instead, phytoplankton to zooplankton biomass ratios were high, especially at intermediate DOC and after N fertilization, implying low trophic transfer efficiencies. An explanation for the observed low phytoplankton resource use, and biomass responses in zooplankton, was dominance of colony forming chlorophytes of reduced edibility at intermediate lake DOC, combined with reduced phytoplankton mineral quality (enhanced seston N:P) with N fertilization. N fertilization, however, increased zooplankton N:P recycling ratios, with largest impact at low DOC where phytoplankton benefitted from light sufficiently to cause enhanced seston N:P. Our results suggest that although N enrichment and increased phytoplankton biomass do not necessarily increase zooplankton biomass, bottom-up effects may still impact zooplankton and their N:P recycling ratio through promotion of phytoplankton species of low edibility and altered mineral quality.
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| 17. |
- Blenckner, T.
(author)
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Models as tools for understanding past, recent and future changes in large lakes.
- 2008
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 599, s. 177-182
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Journal article (peer-reviewed)abstract
- Large lakes currently exhibit ecosystem responses to environmental changes such as climate and land use changes, nutrient loading, toxic contaminants, hydrological modifications and invasive species. These sources have impacted lake ecosystems over a number of years in various combinations and often in a spatially heterogeneous pattern. At the same time, many different kinds of mathematical models have been developed to help to understand ecosystem processes and improve cost-effective management. Here, the advantages and limitations of models and sources of uncertainty will be discussed. From these considerations and in view of the multiple environmental pressures, the following emerging issues still have to be met in order to improve the understanding of ecosystem function and management of large lakes: (1) the inclusion of thresholds and points-of-no-return; (2) construction of general models to simulate biogeochemical processes for a large number of lakes rather than for individual systems; (3) improvement of the understanding of spatio-temporal variability to quantify biogeochemical fluxes accurately; and (4) inclusion of biogeochemical linkages between terrestrial and aquatic ecosystems in model approaches to assess the effects of external environmental pressures such as land-use changes. The inclusion of the above-mentioned issues would substantially improve models as tools for the scientific understanding and cost-effective management of large lakes that are subject to multiple environmental pressures in a changing future.
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| 18. |
- Blenckner, Thorsten, et al.
(author)
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Preface
- 2011
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 660:1, s. 1-2
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Journal article (peer-reviewed)
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| 19. |
- Blindow, Irmgard, et al.
(author)
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Facilitation of clear-water conditions in shallow lakes by macrophytes: differences between charophyte and angiosperm dominance
- 2014
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In: Hydrobiologia. - : Springer Verlag (Germany). - 0018-8158 .- 1573-5117. ; 737:1, s. 99-110
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Journal article (peer-reviewed)abstract
- A number of mechanisms result in a feedback between water clarity and macrophytes and, consequently, the occurrence of alternative stable states in shallow lakes. We hypothesize that bottom-up mechanisms and interactions within the benthic food web are more important in a charophyte-dominated clear-water state, while top-down mechanism and interactions in the planktonic food web prevail at angiosperm dominance. Charophytes, which dominate at lower nutrient concentrations and develop higher densities than most angiosperms, can have a higher influence on sedimentation, resuspension, and water column nutrients. During dominance of dense submerged vegetation like charophytes, zooplankton can be hampered by low food quality and quantity and by high predation pressure from juvenile fish, which in turn are favoured by the high refuge potential of this vegetation. Grazing pressure from zooplankton on phytoplankton can therefore be low in charophytes, but the main feedback in angiosperm-dominated ecosystems. Charophytes offer a higher surface than most angiosperms to periphyton, which favors benthic invertebrates. These support macrophytes by grazing periphyton and constitute a central link in a trophic cascade from fish to periphyton and macrophytes. To test these hypotheses, more experiments and field measurements comparing the effect of charophytes and angiosperms on water clarity are needed.
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| 20. |
- Bohman, Irene, et al.
(author)
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The timing for winter-growing shredder species and leaf litter turnover rate in an oligotrophic lake, SE Sweden
- 2006
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 556:1, s. 99-108
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Journal article (peer-reviewed)abstract
- Small freshwater systems often depend on allochthonous organic subsidies to sustain productivity. Benthic invertebrates consuming coarse detritus maintain the energy flow by conveying dead organic matter into prey items and increase the food availability for other consumers. Compared to lotic systems, the dynamics of coarse detritus decomposition has not received much attention in lakes. The objectives of this study were to investigate the seasonality of leaf litter turnover and the timing of abundance of potential shredder species in a typical oligotrophic boreal lake. Leaf litter was experimentally exposed in litterbags in the littoral zone in Lake Välen from autumn to late spring two consecutive years. The weight loss rate of leaf litter initially followed the same pattern during both winter periods, but was markedly influenced by freezing in late winter the second year. Further, the seasonal variation patterns in abundance in litterbags were quite different among the potential shredder species. Only the limnephilid caddis larvae showed a density variation pattern possible to connect to the weight loss of leaf litter in litterbags. Otherwise frequent detritivores such as Asellus aquaticus and Leptophlebia marginata displayed lowest density in litterbags during the main weight loss period. However, after the long ice period the second winter the remaining leaf litter seemed to be consumed by A. aquaticus. With increasing knowledge of the initial leaf breakdown process and the guild of shredders in lakes, the decomposition rate may also in this habitat become a useful instrument when evaluating the impact from perturbations on ecosystem function.
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| 21. |
- Bryhn, Andreas Christoffer, 1971-
(author)
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A morphometrically based method for predicting water layer boundaries in meromictic lakes
- 2009
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 636:1, s. 413-419
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Journal article (peer-reviewed)abstract
- Many general mass-balance models that simulate processes in one or two water layers have been successfully constructed, tested and used to predict effects from remediating lake pollution and other environmental disturbances. However, these models are poorly suited for meromictic lakes which consist of yet another water layer. In order to determine a cross-systems based algorithm for the depth of the boundary between the two lowest layers (D crit2; in m), data from 24 three-layer lakes were analysed, and this depth could be predicted from the maximum depth and the lake surface area. The resulting model was tested with good results against independent data from 6 lakes which were not used for model development. Furthermore, D crit2 was predicted at a considerably lower depth than the theoretical wave base (a previously defined functional separator between the two top layers) in 110 out of 113 meromictic lakes. This indicates that the equation for D crit2 estimated in this study may be used for developing general mass-balance models for a large number of lakes which contain three stable water layers.
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| 22. |
- Brännäs, Eva
(author)
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A perspective on Salvelinus research
- 2010
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 650, s. 1-2
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Journal article (other academic/artistic)
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| 23. |
- Brönmark, Christer, et al.
(author)
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Indirect effects of fish community structure on submerged vegetation in shallow, eutrophic lakes : an alternative mechanism
- 1992
-
In: Hydrobiologia. - Dordrecht : Springer Netherlands. - 0018-8158 .- 1573-5117. ; 243/244:1, s. 293-301
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Journal article (peer-reviewed)abstract
- The loss of submerged macrophytes during eutrophication of shallow takes is a commonly observed phenomenon. The proximate reason for this decline is a reduction of available light due to increasing phytoplankton and/or epiphyton biomass. Here we argue that the ultimate cause for the transition from a macrophyte-dominated state to a phytoplankton-dominated state is a change in fish community structure. A catastrophic disturbance event (e.g. winterkill) acting selectively on piscivores, cascades down food chains, eventually reducing macrophyte growth through shading by epiphyton, an effect that is reinforced by increasing phytoplankton biomass. The transition back from the phytoplankton to the macrophyte state depends on an increase in piscivore standing stock and a reduction of planktivores. A conceptual model of these mechanisms is presented and supported by literature data and preliminary observations from a field experiment. © 1992 Kluwer Academic Publishers.
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| 24. |
- Brönmark, Christer, et al.
(author)
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Regime shifts in shallow lakes: the importance of seasonal fish migration
- 2010
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 646:1, s. 91-100
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Conference paper (peer-reviewed)abstract
- Shallow eutrophic lakes commonly exist in two alternative stable states: a clear-water state and a turbid water state. A number of mechanisms, including both abiotic and biotic processes, buffer the respective states against changes, whereas other mechanisms likely drive transitions between states. Our earlier research shows that a large proportion of zooplanktivorous fish populations in shallow lakes undertake seasonal migrations where they leave the lake during winter and migrate back to the lake in spring. Based on our past research, we propose a number of scenarios of how feedback processes between the individual and ecosystem levels may affect stability of alternative stable states in shallow lakes when mediated by fish migration. Migration effects on shallow lakes result from processes at different scales, from the individual to the ecosystem. Our earlier research has shown that ecosystem properties, including piscivore abundance and zooplankton productivity, affect the individual state of zooplanktivorous fish, such as growth rate or condition. Individual state, in turn, affects the relative proportion and timing of migrating zooplanktivorous fish. This change, in turn, may stabilize states or cause runaway processes that eventually lead to state shifts. Consequently, such knowledge of processes coupled to seasonal migration of planktivorous fish should increase our understanding of shallow lake dynamics.
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| 25. |
- Burdon, Francis
(author)
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Ecological processes mediate the effects of the invasive bloom-forming diatom Didymosphenia geminata on stream algal and invertebrate assemblages
- 2020
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 847, s. 177-190
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Journal article (peer-reviewed)abstract
- Didymosphenia geminata is a bloom-forming diatom that has invaded numerous temperate rivers globally. Proliferations of D. geminata can result in negative effects on invaded communities. Ecological theory suggests impacts may vary associated with trait variation in both invaded communities and the invader. Trait commonalities related to organism size are rarely considered, yet are expected to influence the outcomes of ecological (niche and neutral) processes and invader effects. We hypothesised that D. geminata would impact diversity and community composition, with effects varying between size classes, influenced by niche and spatial gradients. To examine this hypothesis, we surveyed 55 rivers along a gradient of D. geminata biomass in the South Island, New Zealand, collecting data on algal and invertebrate communities, 33 spatial predictors, and 111 physical and chemical predictors. Didymosphenia geminata biomass was associated with increased species richness in both algal and invertebrate assemblages, but blooms reduced beta-diversity resulting in more homogenous communities. Both niche and neutral processes influenced community assembly and invader effects, which varied between algae and invertebrates. However, D. geminata appeared to have a dominant influence on both communities, irrespective of organism size. These findings reinforce the substantial negative effect invasive species such as D. geminata can cause in invaded ecosystems.
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