| 1. |
- Adrian, Rita, et al.
(författare)
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Lakes as sentinels of climate change
- 2009
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 54:6(2), s. 2283-2297
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Tidskriftsartikel (refereegranskat)abstract
- While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biological responses to climate. However, the efficacy of the different indicators is affected by regional response to climate change, characteristics of the catchment, and lake mixing regimes. Thus, particular indicators or combinations of indicators are more effective for different lake types and geographic regions. The extraction of climate signals can be further complicated by the influence of other environmental changes, such as eutrophication or acidification, and the equivalent reverse phenomena, in addition to other land-use influences. In many cases, however, confounding factors can be addressed through analytical tools such as detrending or filtering. Lakes are effective sentinels for climate change because they are sensitive to climate, respond rapidly to change, and integrate information about changes in the catchment.
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| 2. |
- Hansson, Lars-Anders, et al.
(författare)
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Escape from UV threats in zooplankton: A cocktail of behavior and protective pigmentation
- 2007
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 88:8, s. 1932-1939
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Tidskriftsartikel (refereegranskat)abstract
- In order to avoid environmental threats, organisms may respond by altering behavior or phenotype. Using experiments performed in high-latitude Siberia and in temperate Sweden, we show for the first time that, among freshwater crustacean zooplankton, the defense against threats from ultraviolet radiation (UV) is a system where phenotypic plasticity and behavioral escape mechanisms function as complementary traits. Freshwater copepods relied mainly on accumulating protective pigments when exposed to UV radiation, but Daphnia showed strong behavioral responses. Pigment levels for both Daphnia and copepods were generally higher at higher latitudes, mirroring different UV threat levels. When released from the UV threat, Daphnia rapidly reduced (within 10 days) their UV protecting pigmentation-by as much as 40%-suggesting a cost in maintaining UV protective pigmentation. The. evolutionary advantage of protective pigments is, likely, the ability to utilize the whole water column during daytime; conversely, since the amount of algal food is generally higher in surface waters, unpigmented individuals are restricted to a less preferred feeding habitat in deeper waters. Our main conclusion is that different zooplankton taxa, and similar taxa at different latitudes, use different mixes of behavior and pigments to respond to UV radiation.
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| 3. |
- Peter, Hannes, et al.
(författare)
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An evaluation of methods to study the gut bacterial community composition of freshwater zooplankton.
- 2008
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 30:9, s. 997-1006
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Tidskriftsartikel (refereegranskat)abstract
- The occurrence of gut bacteria in freshwater and marine zooplankton has long been recognized, but knowledge about the composition of the gut "microflora" and its permanent presence in different zooplankters is still inadequate. In this study, we tested the suitability of fluorescence in situ hybridization (FISH), catalysed reporter deposition (CARD)-FISH, cultivation and transmission electron microscopy (TEM) on homogenates and whole-specimen sections to assess the presence and identity of gut bacteria in several freshwater copepod and cladoceran species. Unambiguous results about the presence of a permanent gut "microflora" were obtained for freshly caught Daphnia pulex by TEM. CARD-FISH on gut homogenates from Acanthodiaptomus denticornis and D. pulex revealed a very similar bacterial composition to that present in the water column. Major bacterial groups found in cladocerans and copepods were alpha-, beta-, gamma-Proteobacteria and Cytophaga–Flavobacteria. The high contribution of alpha-Proteobacteria in A. denticornis suggested a specific niche for this group, but probably in association with its carapace. FISH on paraffin semithin sections had the potential to provide quantitative and qualitative information about the composition of the gut "microflora", but loss of bacteria and gut content was significant.
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