| 1. |
- Choudhury, Maidul I., et al.
(författare)
-
Charophytes collapse beyond a critical warming and brownification threshold in shallow lake systems
- 2019
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 661, s. 148-154
-
Tidskriftsartikel (refereegranskat)abstract
- Charophytes play a critical role for the functioning of shallow lake ecosystems. Although growth of charophytes can be limited by many factors, such as temperature, nutrients and light availability, our understanding about concomitant effects of climate warming and other large-scale environmental perturbations, e.g. increases in humic matter content (‘brownification’) is still limited. Here we conducted an outdoor mesocosm experiment during 71 days with a common charophyte species, Chara vulgaris, along an increasing gradient of temperature and brownification. We hypothesized the growth of C. vulgaris to increase with temperature, but to level off along the combined temperature and brownification gradient when reaching a critical threshold for light limitation via brownification. We show that C. vulgaris increases the relative growth rate (RGR), main and total shoot elongation, as well as number of lateral shoots when temperature and brownification increased by +2 °C and + 100%, respectively above today's levels. However, the RGR, shoot elongation and number of lateral shoots declined at further increment of temperature and brownification. Macrophyte weight-length ratio decreased with increased temperature and brownification, indicating that C. vulgaris allocate more resources or energy for shoot elongation instead of biomass increase at warmer temperatures and higher brownification. Our study shows that C. vulgaris will initially benefit from warming and brownification but will then decline as a future scenario of increased warming and brownification reaches a certain threshold level, in case of our experiment at +4 °C and a 2-fold increase in brownification above today's levels.
|
|
| 2. |
- Ekvall, Mikael, et al.
(författare)
-
Diel vertical migration, size distribution and photoprotection in zooplankton as response to UV-A radiation
- 2015
-
Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 60:6, s. 2048-2058
-
Tidskriftsartikel (refereegranskat)abstract
- The transparency regulator hypothesis (TRH) proposes that ultraviolet radiation (UVR) is a main driving force behind diel vertical migration (DVM) of zooplankton in clearwater systems. While previous studies have mainly studied DVM in relation to the TRH on a spatial scale across systems we here focus on long-term trends in a single system in order to assess if UVR explains observed patterns in DVM. We show that the strength of DVM in Daphnia is to a large extent explained by UVR and we demonstrate a tipping point at which the UVR intensity drastically affects the strength of DVM in Daphnia. In contrast, the strength of DVM could not be explained by the level of UVR among calanoid copepods. The amount of photoprotective compounds did not differ between zooplankton found at different depths indicating that zooplankton do not change their vertical position in relation to the amount of accumulated photoprotective compounds. In addition, we show that both Daphnia and calanoid copepods display patterns of size structured migration.
|
|
| 3. |
- Ekvall, Mikael T., et al.
(författare)
-
Long-term effects of tungsten carbide (WC) nanoparticles in pelagic and benthic aquatic ecosystems
- 2018
-
Ingår i: Nanotoxicology. - : Taylor & Francis. - 1743-5390 .- 1743-5404. ; 12:1, s. 79-89
-
Tidskriftsartikel (refereegranskat)abstract
- As the production and usage of nanomaterials are increasing so are the concerns related to the release of the material into nature. Tungsten carbide (WC) is widely used for its hard metal properties, although its use, in for instance tyre studs, may result in nano-sized particles ending up in nature. Here, we evaluate the potential long-term exposure effects of WC nanoparticles on a pelagic (Daphnia magna) and a benthic (Asellus aquaticus) organism. No long-term effects were observed in the benthic system with respect to population dynamics or ecosystem services. However, long-term exposure of D. magna resulted in increased time to first reproduction and, if the particles were resuspended, strong effects on survival and reproductive output. Hence, the considerable differences in acute vs. long-term exposure studies revealed here emphasize the need for more long-term studies if we are to understand the effects of nanoparticles in natural systems.
|
|
| 4. |
- Hansson, Lars Anders, et al.
(författare)
-
Instantaneous threat escape and differentiated refuge demand among zooplankton taxa
- 2016
-
Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 97:2, s. 279-285
-
Tidskriftsartikel (refereegranskat)abstract
- Most animals, including aquatic crustacean zooplankton, perform strong avoidance movements when exposed to a threat, such as ultraviolet radiation (UVR). We here show that the genera Daphnia and Bosmina instantly adjust their vertical position in the water in accordance with the present UVR threat, i.e., seek refuge in deeper waters, whereas other taxa show less response to the threat. Moreover, Daphnia repeatedly respond to UVR pulses, suggesting that they spend more energy on movement than more stationary taxa, for example, during days with fluctuating cloud cover, illustrating nonlethal effects in avoiding UVR threat. Accordingly, we also show that the taxa with the most contrasting behavioral responses differ considerably in photoprotection, suggesting different morphological and behavioral strategies in handling the UVR threat. In a broader context, our studies on individual and taxa specific responses to UVR provide insights into observed spatial and temporal distribution in natural ecosystems.
|
|
| 5. |
- Hedberg, Jonas, 1979-, et al.
(författare)
-
Tungsten carbide nanoparticles in simulated surface water with natural organic matter : dissolution, agglomeration, sedimentation and interaction with Daphnia magna
- 2017
-
Ingår i: Environmental Science: Nano. - : Royal Society of Chemistry. - 2051-8153 .- 2051-8161. ; 4:4, s. 886-894
-
Tidskriftsartikel (refereegranskat)abstract
- Even though anthropogenic nano-sized tungsten carbide nanoparticles (WC NPs) have been found in the environment, there are currently no investigations on their environmental fate. This work studies the interaction between natural organic matter (NOM) and WC NPs, as well as the potential uptake by the aquatic model organism Daphnia magna. We here show that the affinity between WC NPs and humic acid or dihydroxybenzoic acid (DHBA), which are model molecules of NOM, is very low with no observed surface adsorption. The lack of a stabilizing effect of these organic molecules, in combination with a relatively high effective density of WC NP agglomerates in humic acid, resulted in the substantial agglomeration and sedimentation of the WC NPs. A higher stability of the smaller sized WC NP agglomerates (<150 nm) means that this fraction is mobile and can be transported to other settings, suggesting that this particle fraction should be considered in further studies. The dissolution of tungsten from WC NPs was continuous and the relatively slow dissolution rate (on the order of 0.03 mg m-2 h-1) implies that particle transport will not be severely limited from a dissolution perspective. Uptake of tungsten (dissolved tungsten and WC particles) by D. magna was observed although this did not induce any acute toxic effects.
|
|
| 6. |
- Heuschele, Jan, et al.
(författare)
-
Context-dependent individual behavioral consistency in Daphnia
- 2017
-
Ingår i: Ecosphere. - : John Wiley & Sons. - 2150-8925 .- 2150-8925. ; 8:2
-
Tidskriftsartikel (refereegranskat)abstract
- The understanding of consistent individual differences in behavior, often termed “personality,” for adapting and coping with threats and novel environmental conditions has advanced considerably during the last decade. However, advancements are almost exclusively associated with higher-order animals, whereas studies focusing on smaller aquatic organisms are still rare. Here, we show individual differences in the swimming behavior of Daphnia magna, a clonal freshwater invertebrate, before, during, and after being exposed to a lethal threat, ultraviolet radiation (UVR). We show consistency in swimming velocity among both mothers and daughters of D. magna in a neutral environment, whereas this pattern breaks down when exposed to UVR. Our study also, for the first time, illustrates how the ontogenetic development in swimming and refuge-seeking behavior of young individuals eventually approaches that of adults. Overall, we show that aquatic invertebrates are far from being identical robots, but instead they show considerable individual differences in behavior that can be attributed to both ontogenetic development and individual consistency. Our study also demonstrates, for the first time, that behavioral consistency and repeatability, that is, something resembling “personality,” is context and state dependent in this zooplankter taxa.
|
|
| 7. |
- Langer, Sina M., et al.
(författare)
-
A three-dimensional perspective of Daphnia’s swimming behavior with and without predator cues
- 2019
-
Ingår i: Limnology and Oceanography. - : Wiley. - 1939-5590 .- 0024-3590. ; 64:4, s. 1515-1525
-
Tidskriftsartikel (refereegranskat)abstract
- Behavioral adaptations play an important role in predator–prey interactions as they reduce predation risk. Prey organisms have therefore evolved a tremendous variability in behavioral adaptations. In case of small crustaceans of the genus Daphnia, which are common and important herbivores transferring energy from primary producers to higher trophic levels, such as predatory fish, and insects, altered migration patterns, swarming, or adaptive swimming speeds may increase survival rates. However, hitherto it has been difficult to analyze predator-induced behavioral adaptations as the small body size, as well as the low contrast between the transparent animals and their environment, most often impede behavioral movement analysis of individual animals. Therefore, we worked with a newly established technique providing higher contrast. We tagged daphniids with fluorescent nanoparticles and used a three-dimensional movement analysis system. We analyzed behavioral defense strategies of Daphnia clones from three species against different types of predators by measuring their behavior in presence and absence of predator cues. We analyzed swimming speed, depth selection, and motion patterns of Daphnia, as well as swarming behavior. We observed differences in the general swimming behavior in all analyzed aspects and show that daphniids change their behavioral strategies in the presence of predator cues, e.g., decrease their swimming speed as well as their vertical position or increase their nearest neighbor distance. Based on the observed changes in behavioral patterns, we conclude that the swimming behavior of daphniids may play an important role as inducible defense strategy that has the potential to improve prey survival chances.
|
|
| 8. |
- Li, Zhongqiang, et al.
(författare)
-
Climate warming and heat waves affect reproductive strategies and interactions between submerged macrophytes
- 2017
-
Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 23:1, s. 108-116
-
Tidskriftsartikel (refereegranskat)abstract
- Extreme climatic events, such as heat waves, are predicted to increase in frequency and intensity during the next hundred years, which may accelerate shifts in hydrological regimes and submerged macrophyte composition in freshwater ecosystems. Since macrophytes are profound components of aquatic systems, predicting their response to extreme climatic events is crucial for implementation of climate change adaptation strategies. We therefore performed an experiment in 24 outdoor enclosures (400 L) separating the impact of a 4 °C increase in mean temperature with the same increase, that is the same total amount of energy input, but resembling a climate scenario with extreme variability, oscillating between 0 °C and 8 °C above present conditions. We show that at the moderate nutrient conditions provided in our study, neither an increase in mean temperature nor heat waves lead to a shift from a plant-dominated to an algal-dominated system. Instead, we show that species-specific responses to climate change among submerged macrophytes may critically influence species composition and thereby ecosystem functioning. Our results also imply that more fluctuating temperatures affect the number of flowers produced per plant leading to less sexual reproduction. Our findings therefore suggest that predicted alterations in climate regimes may influence both plant interactions and reproductive strategies, which have the potential to inflict changes in biodiversity, community structure and ecosystem functioning.
|
|
| 9. |
- Mattsson, Karin, et al.
(författare)
-
Altered Behavior, Physiology, and Metabolism in Fish Exposed to Polystyrene Nanoparticles
- 2015
-
Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 1520-5851 .- 0013-936X. ; 49:1, s. 553-561
-
Tidskriftsartikel (refereegranskat)abstract
- The use of nanoparticles in consumer products, for example, cosmetics, sunscreens, and electrical devices, has increased tremendously over the past decade despite insufficient knowledge about their effects on human health and ecosystem function. Moreover, the amount of plastic waste products that enter natural ecosystems, such as oceans and lakes, is increasing, and degradation of the disposed plastics produces smaller particles toward the nano scale. Therefore, it is of utmost importance to gain knowledge about how plastic nanoparticles enter and affect living organisms. Here we have administered 24 and 27 nm polystyrene nanoparticles to fish through an aquatic food chain, from algae through Daphnia, and studied the effects on behavior and metabolism. We found severe effects on feeding and shoaling behavior as well as metabolism of the fish; hence, we conclude that polystyrene nanoparticles have severe effects on both behavior and metabolism in fish and that commonly used nanosized particles may have considerable effects on natural systems and ecosystem services derived from them.
|
|
| 10. |
- Mattsson, Karin, et al.
(författare)
-
Translocation of 40 nm diameter nanowires through the intestinal epithelium of Daphnia magna
- 2016
-
Ingår i: Nanotoxicology. - : Informa UK Limited. - 1743-5390 .- 1743-5404. ; 10:8, s. 1160-1167
-
Tidskriftsartikel (refereegranskat)abstract
- Nanowires (NWs) have unique electrical and optical properties of value for many applications including lighting, sensing, and energy harnessing. Consumer products containing NWs increase the risk of NWs being released in the environment, especially into aquatic ecosystems through sewage systems. Daphnia magna is a common, cosmopolitan freshwater organism sensitive to toxicity tests and represents a likely entry point for nanoparticles into food webs of aquatic ecosystems. Here we have evaluated the effect of NW diameter on the gut penetrance of NWs in Daphnia magna. The animals were exposed to NWs of two diameters (40 and 80 nm) and similar length (3.6 and 3.8 μm, respectively) suspended in water. In order to locate the NWs in Daphnia, the NWs were designed to comprise one inherently fluorescent segment of gallium indium phosphide (GaInP) flanked by a gallium phosphide (GaP) segment. Daphnia mortality was assessed directly after 24 h of exposure and 7 days after exposure. Translocation of NWs across the intestinal epithelium was investigated using confocal fluorescence microscopy directly after 24 h of exposure and was observed in 89% of Daphnia exposed to 40 nm NWs and in 11% of Daphnia exposed to 80 nm NWs. A high degree of fragmentation was observed for NWs of both diameters after ingestion by the Daphnia, although 40 nm NWs were fragmented to a greater extent, which could possibly facilitate translocation across the intestinal epithelium. Our results show that the feeding behavior of animals may enhance the ability of NWs to penetrate biological barriers and that penetrance is governed by the NW diameter.
|
|
