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| 2. |
- Adler, Sven
(författare)
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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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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 742, s. 295-312
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Ahlgren, Johan, et al.
(författare)
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The influence of predator regime on the behaviour and mortality of a freshwater amphipod, Gammarus pulex
- 2011
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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 671:1, s. 39-49
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Al Jawaheri, Raad, et al.
(författare)
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Negative impact of lake liming programmes on the species richness of dragonflies (Odonata) : a study from southern Sweden
- 2017
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Ingår i: Hydrobiologia. - Dordrecht : Springer Netherlands. - 0018-8158 .- 1573-5117. ; 788:1, s. 99-113
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Tidskriftsartikel (refereegranskat)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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| 5. |
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| 6. |
- Andersson, A, et al.
(författare)
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Effect of nutrient enrichment on the distribution and sedimentation of polychlorinated biphenyls (PCBs) in seawater
- 1998
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Ingår i: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 377, s. 45-56
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Tidskriftsartikel (refereegranskat)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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| 7. |
- Andersson, Per, et al.
(författare)
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Sulphur isotope ratios in sulphate and oxygen isotopes in water from a small watershed in central Sweden
- 1992
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Ingår i: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 235-236:1, s. 205-217
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Arnott, Russell N., et al.
(författare)
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Artificially generated turbulence : a review of phycological nanocosm, microcosm, and mesocosm experiments
- 2021
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Ingår i: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117. ; 848, s. 961-991
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Forskningsöversikt (refereegranskat)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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| 9. |
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| 10. |
- Baho, Didier Ludovic, et al.
(författare)
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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
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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 778, s. 13-32
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Tidskriftsartikel (refereegranskat)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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