| 1. |
- Bergfur, Jenny
(författare)
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Temporal variation in carbon and nitrogen isotope ratios of aquatic biota in two contrasting boreal streams
- 2013
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Ingår i: Fundamental and Applied Limnology. - : E. Schweizerbart'sche Verlagsbuchhandlung. - 1863-9135. ; 182:3, s. 205-218
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Tidskriftsartikel (refereegranskat)abstract
- Natural abundant isotopes of carbon and nitrogen are frequently used to elucidate food webs and trace energy flows in aquatic ecosystems. Seasonal events such as leaf fall and algal blooms can influence temporal patterns and hence also affect interpretations of isotope data. This study examined such patterns in two contrasting streams in Sweden: Vadsbacken, which is heavily impacted by agriculture and has high nitrogen levels, and Pinnarpsbacken, which has a primarily forested catchment and lower nitrogen levels. Different organic compartments (e.g., detritus, biofilm, and invertebrates) were sampled in September, November, April, and June. Effects of sampling date on isotope signatures of leaf litter (delta N-15: p = 0.0001, delta C-13: p = 0.03), seston (delta N-15: p = 0.001, delta C-13: p = 0.001), FPOM (delta N-15: p = 0.03, delta C-13: p = 0.003), wood (delta C-13: p = 0.05) and invertebrates (delta N-15: p = 0.04) were found. However, there were site-specific temporal patterns in isotope signatures, probably reflecting disparate origins of allochthonous material related to the differences in catchment land use. Mixing models revealed no changes in resource partitioning that could be attributed to the above-mentioned seasonal events. The site-specific patterns recorded here indicate that generalisation regarding ecosystems with different perturbations should be done with caution.
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| 2. |
- Hancke, Marnie, et al.
(författare)
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Genetic diversity of Monoporeia affinis in relationship to environmental and spatial factors in Sweden’s largest lakes
- 2012
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Ingår i: Fundamental and Applied Limnology. - : Schweizerbart. - 1863-9135. ; 181, s. 183–195-
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Tidskriftsartikel (refereegranskat)abstract
- The glacial relict species Monoporeia affinis undergoes pronounced population fluctuations in Sweden's three largest lakes, which may be due to multiple forms of environmental stress, including eutrophication and subsequent hypoxia. In this study, we use cytochrome c oxidase subunit I (COI) and 16srRNA (16 S) sequence data to assess the genetic diversity of this freshwater amphipod, and study their spatial and environmental correlates. The populations in the three lakes were genetically differentiated with haplotype diversity of the 16 S gene being lower in populations from Lake Malaren compared to those in Lake Vattern and Lake Vanern; however, a broad-scale spatial analysis did not detect significant spatial patterns in genetic diversity across the lakes. Within lakes, however, subtle spatial effects were detected in the form of a significant distance decay of genetic diversity in some lakes, highlighting the importance of considering different spatial scales for studying genetic diversity. From the environmental variables studied, a biologically relevant impact of both oxygen and total phosphorus levels on haplotype diversity levels was found, indicating the negative consequences of eutrophication on genetic diversity of M. affinis. Despite significant decreases and fluctuations in population sizes, the demographic history of M. affinis populations is best described by a model of constant population size over time, suggesting a sufficiently large effective population size.
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| 3. |
- Mcgoff, Elaine, et al.
(författare)
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Catchment land-use effects on littoral macroinvertebrates in response to local habitat structure and trophic state
- 2012
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Ingår i: Fundamental and Applied Limnology. - : Schweizerbart. - 1863-9135. ; 180, s. 111-121
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Tidskriftsartikel (refereegranskat)abstract
- Lake habitat alteration is a major stressor for lakes worldwide, and physical habitat alteration is likely the biggest threat to aquatic ecosystems, exceeding all other anthropogenic pressures. This study sought to elucidate which group of variables was the most important for describing Swedish macroinvertebrate community structure: trophic status, substrate variables or riparian variables. We also investigated what influence each of these groups of variables has on the other. The impact of large scale land use patterns was also investigated, to determine if macroinvertebrates responded differently in two different catchment land use types: impaired and unimpaired. Partial canonical ordination analysis showed that substrate variables were the most important for describing macroinvertebrate community variation in both catchment land use classes, followed by riparian descriptors, with the trophic signal only becoming clear when lakes were more strongly stratified for coarseness of substrate. This trophic effect was only evident in the impaired lakes, as the trophic gradient was much shorter in the lakes with an unimpaired catchment. Our results suggest that trophic effects on benthic invertebrates are nested within substrate habitat effects, and were masked by local habitat heterogeneity. This indicates that, at least in the Swedish situation, greater care needs to be taken in stratifying the substrate sampled in order to see this nutrient pressure-macroinvertebrate response relationship. The macroinvertebrate community composition was also responding to changes in riparian vegetation, specifically the presence of riparian trees and canopy cover. These variables, or lack of, are possible proxies for anthropogenic alteration of lake shores. Therefore, although macroinvertebrates may not be strong indicators of trophic pressure in all cases or habitats, they may be useful indicators for other anthropogenic pressures (e.g. hydromorphology) on lake shores.
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| 4. |
- Pilotto, Francesca, et al.
(författare)
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Spatial variance of profundal and sublittoral invertebrate benthic communities in response to eutrophication and morphological pressures
- 2012
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Ingår i: Fundamental and Applied Limnology. - : Schweizerbart. - 1863-9135. ; 180:2, s. 101-110
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Tidskriftsartikel (refereegranskat)abstract
- Invertebrate communities inhabiting different lake zones are expected to respond differently to natural environmental variation and anthropogenic stressors. We used multivariate statistical methods in order to quantify the effects of eutrophication and morphological pressures on the spatial structure of the invertebrate benthic communities at two depth zones (profundal and sublittoral) in subalpine lakes in Italy, Germany and Austria . In both lake zones, environmental variables related to eutrophication pressures (mid-lake total phosphorus and chlorophyll-a) were significant in structuring the invertebrate community (permutation test: p < 0.01). Three variables relating to morphological pressures (diversity of macrophyte growth forms, sum of pressures in the lake shore, and percentage of natural land cover within a 200 m stretch from the lake shore) were significant (permutation test: p < 0.01) in the sublittoral zone, while in the profundal zone none of the variables included in the analysis related to morphological pressures were significant in structuring the invertebrate community. Variance partitioning analysis showed that profundal communities were mainly affected by eutrophication (8.6 % of total variance; p = 0.005), while in the sublittoral zone eutrophication accounted for only 0.5 % (p = 0.04) of total variance. The effects of morphological pressures could be tracked only in the sublittoral zone, where it accounted for 0.8 % of total variance (p = 0.015). The spatial component was responsible for a large part of the total variance (58.7 % in the profundal, p = 0.005; 44.2 % in the sublittoral zone, p = 0.005) and had interactions with stressor variables in both lake zones. Therefore the analysis of spatial patterns should be included in assessment systems relating invertebrate assemblages to pressures.
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| 5. |
- Andrén, C, et al.
(författare)
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Benthic diatoms as indicators of acidity in streams
- 2008
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Ingår i: Fundam. Appl. Limnol.. - : Schweizerbart. ; 173, s. 237-253
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Tidskriftsartikel (refereegranskat)abstract
- As acidification changes from chronic to more episodic in nature, study focus shifts from lakes, where the basin moderates acidity, to streams where acid episodes occur. To assess the effects of acid stress, several macroinvertebrate indices have been used in Scandinavia and elsewhere, based on the presence or absence of species. Benthic diatoms are strongly linked to water quality with small spatial influence, and display a broad spectrum of species. An acidity index for streams based on benthic diatoms could refine assessment resolution, which is required as the acidification declines. During the autumns of 2004 and 2005, 99 benthic diatom samples were collected from 75 humic streams in Sweden that were monitored by monthly water sampling. The relationships between benthic diatoms and measured environmental variables were explored using canonical correspondence analysis. Acidity was the principal factor influencing the diatoms, with the highest eigenvalues noted for pH, alkalinity, and inorganic aluminium. Several weighted averaging (WA) models were developed to infer stream pH, both using 50 streams from 2004 as a calibration dataset cross-validated with 49 streams from 2005 as an independent dataset, and by modeling all 99 streams. The predictive power of the WA models was good. The model with all streams showed a high correlation for mean pH (r2 = 0.85) and minimum pH (r2 = 0.74) values. An acidity index for diatoms, ACID, was proposed. The correlations to mean and minimum pH values were strong, at r2 = 0.85 and 0.77, respectively. Our results confirmed a strong link between benthic diatoms and water quality, particularly acidity. By employing different approaches we demonstrated that diatoms are excellent acidity indicators. The proposed ACID index can be used to assess the acidity state of a stream. ACID is more convenient to use than a WA model for pH and has equal precision.
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| 6. |
- Angeler, David
(författare)
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Phytoplankton community structure along saline and trophic state gradients in urban clay-pit ponds (Austria)
- 2011
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Ingår i: Fundamental and Applied Limnology. - : Schweizerbart. - 1863-9135. ; 178, s. 301-314
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Tidskriftsartikel (refereegranskat)abstract
- We quantified interactive effects of human activities and ionic composition on algal community patterns. The work was done in ten urban clay-pit ponds within the vicinity of Vienna (Austria), characterized by gradients of clay-rich geological deposits and different trophic states caused by multiple sources of anthropogenic stress like nutrient input, swimming or shoreline destruction. A total number of 397 algal taxa were found with some halotolerant species occurring in high abundance like the diatom taxa Entomoneis paludosa, Chaetoceros muelleri, Navicula halophila or the rare Gyrosigma parkerii. Halophil and halotolerant taxa were insensitive to eutrophication. Although the ponds showed on average only moderately elevated electric conductivities (1833 +/- 580 (SD) mu S cm(-1)), taxa number were negatively related to ion concentration. SO(4)(2-) and HCO(3)(-) were the most important anions, with SO(4)(-2) dominating at most sites. Ca(2+) was the major cation in six ponds; four more had Ca(2+) and Na(+) as co-dominant cations. The Viennese sites experienced higher nutrient loadings than the ponds located in Lower Austria. Cluster analysis revealed eight significant groups which represented both spatial and temporal differences among individual ponds. For these groups 32 indicator species were defined. With only two exceptions no halophil nor halotolerant taxa were found as indicator species because these were highly abundant in all investigated ponds. Canonical correspondence analysis showed a strong spatial separation of the ponds with 20 % of the species variation being explained by environmental variables. Variance partitioning revealed the composite variables eutrophication as a function of anthropogenic pressure and ion concentration of equal importance for species variability data.
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| 7. |
- Beier, Sara, et al.
(författare)
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Betaproteobacterial ammonia oxidizers in root zones of aquatic macrophytes
- 2010
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Ingår i: Fundamental and Applied Limnology. - : Schweizerbart. - 1863-9135. ; 177:4, s. 241-255
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Tidskriftsartikel (refereegranskat)abstract
- Enhanced nitrification and coupled denitrification in macrophyte root zones may contribute to the depletion of nitrogen from the rhizosphere and are both critical processes for agriculture and rhizoremediation. We examined one factor likely to affect these processes: the ammonia oxidizing betaproteobacterial community composition, and whether or not it is influenced by plant species (Eleocharis acicularis, Eleocharis palustris, Typha angustifolia) or sediment characteristics. Genes coding for ammonia monooxygenase (amoA) and 16S rRNA of betaproteobacterial ammonia oxidizers were targeted. The betaproteobacterial ammonia oxidizing community in root surface biofilms was distinct from the surrounding rhizosphere sediment. In contrast, communities in rhizosphere and bulk sediment samples were very similar. Our results showed the occurrence of Nitrosomonas europaea-like bacteria nearly exclusively in the rhizoplane biofilms, while sequences affiliated with the Nitrosomonas oligotropha, Nitrosomonas communis and Nitrosospira-lineages were more frequently detected in the surrounding sediment. Our results further suggest that the presence of N. europaea on macrophyte roots depends on the sampling site rather than on the studied macrophyte species. We propose that the rhizoplane of aquatic macrophytes is a natural habitat for N. europaea.
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| 8. |
- Göthe, Emma, et al.
(författare)
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Forestry affects food webs in northern Swedish coastal streams
- 2009
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Ingår i: Fundamental and Applied Limnology. - Stuttgart : E. Schweizerbart'sche Verlagsbuchhandlung. - 1863-9135. ; 175:4, s. 281-294
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Tidskriftsartikel (refereegranskat)abstract
- We investigated how riparian logging affects the food webs of coastal streams in northern Sweden by comparing streams surrounded either by clear-cuts or old-growth forests. Specific hypotheses were that: (i) algal standing stocks are higher in clear-cut streams, whereas detrital standing stocks are higher in old-growth streams; (ii) algal-based (autotrophic) pathways contribute more to consumer (aquatic insect) body carbon in clear-cut streams than in old-growth streams; (iii) a higher autotrophic contribution reflects a combination of numerical (increased abundance of herbivore taxa) and functional (shift in diet by generalist taxa) responses of insect taxa to logging; and (iv) potential predators function more strictly as true predators, and reduce propensity to omnivory in clear-cut relative to old-growth streams. The standing stocks of algae and fine particulate organic matter (FPOM) were similar between treatments, whereas the standing stock of coarse particulate organic matter (CPOM) was higher in old-growth streams. Stable isotope analysis suggested that the autochthonous contribution to aquatic insect carbon per individual taxon was greater in clear-cut than in old-growth streams; although the difference was not statistically conclusive the large effect size suggests that it is biologically meaningful. Greater reliance on autotrophic pathways in clear-cut streams seemed to be caused by a decrease in the relative consumption of detritus by the generalist species Leuctra hippopus, an increase in the abundance of the specialist herbivore Baetis rhodani, and a diffuse increase in the consumption of algae across all functional feeding groups except gathering-collectors. Resources and consumers were enriched in (15)N in clear-cut relative to old-growth streams, suggesting that forestry affects the microbial processing of organic nitrogen, which in turn causes an increased availability of (15)N to algae. The enrichment in (15)N in clear-cut relative to old-growth streams was apparent in all functional feeding groups except for gathering-collectors. In summary, our results show that riparian logging affects the balance of aquatic vs. terrestrial carbon sources and the cycling of nutrients in streams, with effects reverberating to the aquatic consumers.
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| 9. |
- Hirsch, Philipp Emanuel, et al.
(författare)
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A previously undescribed set of Saprolegnia spp. In the invasive spiny-cheek crayfish (Oronectes limosus, Rafinesque)
- 2008
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Ingår i: Fundamental and Applied Limnology. - : Schweizerbart. - 1863-9135. ; 172:2, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- Coinciding with a population decline in the invasive spiny-cheek crayfish Orconectes limosus in Lake Constance. SW Germany, we found crayfish specimens with a fungus-like Aufwuchs which after DNA-isolation and sequencing was identified as consisting of a set of previously undescribed Saprolegnia species. This finding may have implications for the farming and conservation of native crayfish as well as for the lake's ecosystem. We propose that spiny-cheek crayfish might function as a disease vector for these potential pathogens.
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| 10. |
- Palm, Fredrik, 1975, et al.
(författare)
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Subfossil Chaoborus mandibles confirm historical fish decline in two acidified lakes, SW Sweden
- 2010
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Ingår i: Journal of Fundamental and Applied Limnology. - : Schweizerbart. - 1863-9135. ; 177:4, s. 313-320
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Tidskriftsartikel (refereegranskat)abstract
- Sediment cores from acidified Lake Gaffeln and Lake Lilla Hastevatten, SW Sweden, were analysed to test if the occurrence of subfossil Chaoborus mandibles were coupled to extinction of fish in the early 1970s. Mandibles of C. flavicans were found throughout the sediment cores while mandibles of C. obscuripes occurred in more recent sediments only. The appearance of C. obscuripes mandibles was accompanied by an increase of C. flavicans mandibles in both lakes, indicating reduced fish predation and eventual fish loss. The increase in Chaoborus flavicans density confirms earlier studies that this species is favoured by the loss of fish in acidified lakes. Since C. obscuripes is a strong indicator of fish-free conditions, we propose that this species can be used in paleo-studies as an indicator of fish absence in the same way as C. americanus in North America. However, mandibles of C. obscuripes were scarce in the sediment cores, and it will likely be of best use as indicator in shallow and humic lakes, i.e. its preferred lake type.
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