| 1. |
- Göthe, Emma, et al.
(author)
-
Forestry affects food webs in northern Swedish coastal streams
- 2009
-
In: Fundamental and Applied Limnology. - Stuttgart : E. Schweizerbart'sche Verlagsbuchhandlung. - 1863-9135. ; 175:4, s. 281-294
-
Journal article (peer-reviewed)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.
|
|
| 2. |
- Kraemer, Benjamin M., et al.
(author)
-
Climate change drives widespread shifts in lake thermal habitat
- 2021
-
In: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 11:6, s. 521-529
-
Journal article (peer-reviewed)abstract
- Lake surfaces are warming worldwide, raising concerns about lake organism responses to thermal habitat changes. Species may cope with temperature increases by shifting their seasonality or their depth to track suitable thermal habitats, but these responses may be constrained by ecological interactions, life histories or limiting resources. Here we use 32 million temperature measurements from 139 lakes to quantify thermal habitat change (percentage of non-overlap) and assess how this change is exacerbated by potential habitat constraints. Long-term temperature change resulted in an average 6.2% non-overlap between thermal habitats in baseline (1978-1995) and recent (1996-2013) time periods, with non-overlap increasing to 19.4% on average when habitats were restricted by season and depth. Tropical lakes exhibited substantially higher thermal non-overlap compared with lakes at other latitudes. Lakes with high thermal habitat change coincided with those having numerous endemic species, suggesting that conservation actions should consider thermal habitat change to preserve lake biodiversity. Using measurements from 139 global lakes, the authors demonstrate how long-term thermal habitat change in lakes is exacerbated by species' seasonal and depth-related constraints. They further reveal higher change in tropical lakes, and those with high biodiversity and endemism.
|
|
| 3. |
- Lepori, Fabio, et al.
(author)
-
Deterministic control on community assembly peaks at intermediate levels of disturbance
- 2009
-
In: Oikos. - : Wiley-Blackwell. - 0030-1299 .- 1600-0706. ; 118:3, s. 471-479
-
Journal article (peer-reviewed)abstract
- Despite long-standing research, the processes that drive community assembly remain poorly understood. We censused macroinvertebrate communities and measured flood disturbance in 17 Scandinavian mountain streams to assess the hypothesis that communities are shaped by stochastic processes under stable conditions, and increasingly by deterministic processes as disturbance becomes more severe. Each study stream was categorized as being stable (n=5), intermediate (n=7), or disturbed (n=5) depending on the severity of scouring floods. Following spring floods, the number of potential colonisers decreased with increasing disturbance, suggesting that disturbance filtered out species unable to cope with the stress involved. Communities at stable sites had the highest beta diversity, indicating that stochastic processes of community assembly were most important under the least disturbed conditions. In partial contrast with our predictions, the lowest beta diversity occurred between intermediate (not disturbed) sites, suggesting that increasing disturbance first enhances determinism but then rekindles stochasticity at severity levels beyond intermediate. Macroinvertebrate communities were shaped by deterministic processes, which recruit potential regional colonists depending on niche differences and disturbance conditions and by stochastic processes, which distribute the selected species randomly among individual localities. Although often considered opposing, stochastic and deterministic processes interact hierarchically, with relative strength modified by disturbance.
|
|
| 4. |
|
|
| 5. |
- Nava, Veronica, et al.
(author)
-
Plastic debris in lakes and reservoirs
- 2023
-
In: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 619:7969, s. 317-322
-
Journal article (peer-reviewed)abstract
- Plastic debris is thought to be widespread in freshwater ecosystems globally(1). However, a lack of comprehensive and comparable data makes rigorous assessment of its distribution challenging(2,3). Here we present a standardized cross-national survey that assesses the abundance and type of plastic debris (>250 mu m) in freshwater ecosystems. We sample surface waters of 38 lakes and reservoirs, distributed across gradients of geographical position and limnological attributes, with the aim to identify factors associated with an increased observation of plastics. We find plastic debris in all studied lakes and reservoirs, suggesting that these ecosystems play a key role in the plastic-pollution cycle. Our results indicate that two types of lakes are particularly vulnerable to plastic contamination: lakes and reservoirs in densely populated and urbanized areas and large lakes and reservoirs with elevated deposition areas, long water-retention times and high levels of anthropogenic influence. Plastic concentrations vary widely among lakes; in the most polluted, concentrations reach or even exceed those reported in the subtropical oceanic gyres, marine areas collecting large amounts of debris(4). Our findings highlight the importance of including lakes and reservoirs when addressing plastic pollution, in the context of pollution management and for the continued provision of lake ecosystem services.
|
|
| 6. |
- Nilsson, Christer, 1951-, et al.
(author)
-
Forecasting environmental responses to restoration of rivers used as log floatways : an interdisciplinary challenge
- 2005
-
In: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 8:7, s. 779-800
-
Journal article (peer-reviewed)abstract
- Log floating in the 19th to mid 20th centuries has profoundly changed the environmental conditions in many northern river systems of the world. Regulation of flow by dams, straightening and narrowing of channels by various piers and wing dams, and homogenization of bed structure are some of the major impacts. As a result, the conditions for many riverine organisms have been altered. Removing physical constructions and returning boulders to the channels can potentially restore conditions for these organisms. Here we describe the history of log driving, review its impact on physical and biological conditions and processes, and predict the responses to restoration. Reviewing the literature on comparable restoration efforts and building upon this knowledge, using boreal Swedish rivers as an example, we address the last point. We hypothesize that restoration measures will make rivers wider and more sinuous, and provide rougher bottoms, thus improving land-water interactions and increasing the retention capacity of water, sediment, organic matter and nutrients. The geomorphic and hydraulic/hydrologic alterations are supposed to favor production, diversity, migration and reproduction of riparian and aquatic organisms. The response rates are likely to vary according to the types of processes and organisms. Some habitat components, such as beds of very large boulders and bedrock outcrops, and availability of sediment and large woody debris are believed to be extremely difficult to restore. Monitoring and evaluation at several scales are needed to test our predictions.
|
|
| 7. |
- Palm, Daniel, et al.
(author)
-
The influence of spawning habitat restoration on juvenile brown trout (Salmo trutta) density
- 2007
-
In: Canadian Journal of Fisheries and Aquatic Sciences. ; 64:3, s. 509-515
-
Journal article (peer-reviewed)abstract
- Between 1992 and 2003, we assessed the density of age-0+ brown trout (Salmo trutta) in a channelized stream in northern Sweden, which was restored using two different schemes. One section of the stream was restored by the addition of boulders and reconstruction of gravel beds (boulder + gravel section), whereas another section was restored through addition of boulders only (boulder-only section). In addition, we compared the substrate size composition of gravel beds and the egg-to-fry survival between the two stream sections, and we related the density of age-0+ brown trout to the area of reconstructed gravel beds. After the restoration, the density of age-0+ brown trout increased significantly in the boulder + gravel section and was positively correlated with the area of reconstructed gravel beds. By contrast, the density of age-0+ brown trout did not change in the boulder-only treatment. Egg-to-fry survival was significantly higher in the boulder + gravel section compared with the boulder-only section, probably because of the higher content of sand and fines in the gravel beds of the latter treatment. This study shows that the density of age-0+ brown trout was limited by the availability and quality of spawning substrate rather than by the structural habitat complexity.De 1992 à 2003, nous avons évalué la densité des truites brunes (Salmo trutta) d'âge 0+ dans un cours d'eau canalisé du nord de la Suède, qui a été restauré selon deux arrangements différents. Une section a été restaurée par l'addition de blocs de pierre et la reconstruction des lits de gravier (section blocs + gravier), alors qu'une autre section n'a reçu que des blocs (section blocs seuls). De plus, nous avons comparé la composition en taille du substrat dans les lits de gravier et la survie de l'oeuf à l'alevin dans les deux sections de cours d'eau; nous avons mis en relation la densité des truites brunes d'âge 0+ à la surface des lits de gravier reconstruits. Après la restauration, la densité des truites brunes d'âge 0+ a augmenté significativement dans la section blocs + gravier où elle est en corrélation positive avec la surface des lits de gravier reconstitués. Au contraire, la densité des truites d'âge 0+ n'a pas changé dans la section ayant reçu les blocs seuls. La survie de l'oeuf à l'alevin est significativement plus importante dans la section blocs + gravier que dans la section blocs seuls, probablement à cause du contenu plus grand de sable de de sédiments fins dans les lits de gravier de cette dernière section. Notre étude montre que la densité des truites d'âge 0+ est limitée par la disponibilité et la qualité des substrats de fraie plutôt que par la complexité structurale de l'habitat.[Traduit par la Rédaction]
|
|
| 8. |
- Pilla, Rachel M., et al.
(author)
-
Deeper waters are changing less consistently than surface waters in a global analysis of 102 lakes
- 2020
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
-
Journal article (peer-reviewed)abstract
- Globally, lake surface water temperatures have warmed rapidly relative to air temperatures, but changes in deepwater temperatures and vertical thermal structure are still largely unknown. We have compiled the most comprehensive data set to date of long-term (1970–2009) summertime vertical temperature profiles in lakes across the world to examine trends and drivers of whole-lake vertical thermal structure. We found significant increases in surface water temperatures across lakes at an average rate of + 0.37 °C decade−1, comparable to changes reported previously for other lakes, and similarly consistent trends of increasing water column stability (+ 0.08 kg m−3 decade−1). In contrast, however, deepwater temperature trends showed little change on average (+ 0.06 °C decade−1), but had high variability across lakes, with trends in individual lakes ranging from − 0.68 °C decade−1 to + 0.65 °C decade−1. The variability in deepwater temperature trends was not explained by trends in either surface water temperatures or thermal stability within lakes, and only 8.4% was explained by lake thermal region or local lake characteristics in a random forest analysis. These findings suggest that external drivers beyond our tested lake characteristics are important in explaining long-term trends in thermal structure, such as local to regional climate patterns or additional external anthropogenic influences.
|
|
| 9. |
- Pilla, Rachel M., et al.
(author)
-
Global data set of long-term summertime vertical temperature profiles in 153 lakes
- 2021
-
In: Scientific Data. - : Springer Nature. - 2052-4463. ; 8:1
-
Journal article (peer-reviewed)abstract
- Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of lake thermal structure in a time of rapid global and ecological change.
|
|
| 10. |
|
|
