| 1. |
- Abeysinghe, Kasun S., et al.
(author)
-
Mercury flow through an Asian rice-based food web
- 2017
-
In: Environmental Pollution. - : ELSEVIER SCI LTD. - 0269-7491 .- 1873-6424. ; 229, s. 219-228
-
Journal article (peer-reviewed)abstract
- Mercury (Hg) is a globally-distributed pollutant, toxic to humans and animals. Emissions are particularly high in Asia, and the source of exposure for humans there may also be different from other regions, including rice as well as fish consumption, particularly in contaminated areas. Yet the threats Asian wildlife face in rice-based ecosystems are as yet unclear. We sought to understand how Hg flows through rice-based food webs in historic mining and non-mining regions of Guizhou, China. We measured total Hg (THg) and methylmercury (MeHg) in soil, rice, 38 animal species (27 for MeHg) spanning multiple trophic levels, and examined the relationship between stable isotopes and Hg concentrations. Our results confirm biomagnification of THg/MeHg, with a high trophic magnification slope. Invertivorous songbirds had concentrations of THg in their feathers that were 15x and 3x the concentration reported to significantly impair reproduction, at mining and non-mining sites, respectively. High concentrations in specialist rice consumers and in granivorous birds, the later as high as in piscivorous birds,, suggest rice is a primary source of exposure. Spiders had the highest THg concentrations among invertebrates and may represent a vector through which Hg is passed to vertebrates, especially songbirds. Our findings suggest there could be significant population level health effects and consequent biodiversity loss in sensitive ecosystems, like agricultural wetlands, across Asia, and invertivorous songbirds would be good subjects for further studies investigating this possibility.
|
|
| 2. |
- Catalán, Núria, 1985-, et al.
(author)
-
Effects of beaver impoundments on dissolved organic matter quality and biodegradability in boreal riverine systems
- 2017
-
In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 793:1, s. 135-148
-
Journal article (peer-reviewed)abstract
- Beaver impoundments modify the structure of river reaches and lead to changes in ecosystem function and biogeochemical processes. Here, we assessed the changes in dissolved organic matter (DOM) quality and the biodegradation patterns in a set of beaver systems across Sweden. As the effect of beaver impoundments might be transient and local, we compared DOM quality and biodegradability of both pond and upstream sections of differentially aged beaver systems. Newly established dams shifted the sources and DOM biodegradability patterns. In particular, humic-like DOM, most likely leached from surrounding soils, characterized upstream sections of new beaver impoundments. In contrast, autochthonous and processed compounds, with both higher biodegradation rates and a broader spectrum of reactivities, differentiated DOM in ponds. DOM in recently established ponds seemed to be more humic and less processed compared to older ponds, but system idiosyncrasies determined by catchment particularities influenced this ageing effect.
|
|
| 3. |
- Herrero Ortega, Sonia, et al.
(author)
-
High methylmercury formation in ponds fueled by fresh humic and algal derived organic matter
- 2018
-
In: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 63, s. S44-S53
-
Journal article (peer-reviewed)abstract
- Neurotoxic methylmercury causes adverse effects to ecosystem viability and human health. Previous studies have revealed that ponding alters natural organic matter (NOM) composition and increase methylmercury concentrations in rivers, especially in the first years after flooding. Here, we investigate the influence of NOM composition (i.e., sources and degradation status) on mercury methylation rate constants in nine boreal beaver ponds of different ages across Sweden. We show that increased methylmercury concentrations in surface waters is a consequence of enhanced mercury methylation in the pond sediments. Moreover, our results reveal that during the first years after the initial flooding, mercury methylation rates are fueled by the amount of fresh humic substances released from the flooded soils and by an increased production of algal-derived NOM triggered by enhanced nutrient availability. Our findings indicate that impoundment-induced changes in NOM composition control mercury methylation processes, causing the raise in MeHg levels in ponds.
|
|
| 4. |
- Wu, Pianpian, et al.
(author)
-
Diet influence on mercury bioaccumulation as revealed by polyunsaturated fatty acids in zoobenthos from two contrasting environments: Chinese reservoirs and Swedish lakes
- 2021
-
In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 782
-
Journal article (peer-reviewed)abstract
- The bioaccumulation of mercury (Hg) and polyunsaturated fatty acids (PUFA) in zoobenthos varies across aquatic food webs. In this field study, contents of total Hg (THg), methylmercury (MeHg) and PUFA were investigated in zoobenthos of Chinese reservoirs and Swedish lakes, with contrasting environmental characteristics and algal diet sources, which can result in difference of Hg and PUFA in zoobenthos from these two habits. Using PUFA as dietary biomarkers of algae in zoobenthos, we evaluated effects of environmental factors and algal diet sources on the accumulation of THg, MeHg, and the highly required PUFA eicosapentaenoic (EPA, 20: 5n-3) and docosahexaenoic acid (DHA, 22:6n-3) in zoobenthos. Average THg and MeHg in zoobenthos were higher in Chinese reservoirs than Swedish lakes (p < 0.05). Average EPA content of zoobenthos was similar in these two habitats (p > 0.05), yet average DHA content of zoobenthos was higher in Chinese reservoirs than Swedish lakes (p < 0.05). Total Hg and MeHg contents of zoobenthos in Swedish lakes were predicted by environmental factors; e.g., negatively with pH and positively with dissolved organic carbon (DOC) concentrations, yet had no significant relationship with the algal dietary. In Chinese reservoirs, however, no environmental factor correlated well with THg contents in zoobenthos, and only DOC concentrations showed positive correlation with MeHg contents in zoobenthos. Besides, the algal dietary was also positively correlated with MeHg contents in zoobenthos. EPA and DHA contents of zoobenthos in Swedish lakes primarily associated with algal diet. By contrast, in Chinese reservoirs, EPA and DHA contents of zoobenthos were affected by both environmental factors and algal diet. (C) 2021 Elsevier B.V. All rights reserved.
|
|
| 5. |
- Wu, Pianpian, et al.
(author)
-
Does forest harvest increase the mercury concentrations in fish? : Evidence from Swedish lakes
- 2018
-
In: Science of the Total Environment. - : ELSEVIER SCIENCE BV. - 0048-9697 .- 1879-1026. ; 622-623, s. 1353-1362
-
Journal article (peer-reviewed)abstract
- A number of studies have evaluated the effects of forest harvest on mercury (Hg) concentrations and exports in surface waters, but few studies have tested the effect from forest harvest on the change in fish Hg concentrations over the course of several years after harvest. To address this question, mercury (Hg) concentrations in perch (Perca fluviatilis) muscle tissue from five lakes were analyzed for two years before (2010-2011) and three years after (2013-2015) forest harvest conducted in 2012. Fish Hg concentrations in the clear-cut catchments (n = 1373 fish specimens) were related to temporal changes of fish Hg in reference lakes (n = 1099 fish specimen) from 19 lakes in the Swedish National Environmental Monitoring Programme. Small (length < 100 mm) and large perch (length >= 100 mm) were analyzed separately, due to changing feeding habitats of fish over growing size. There was considerable year-to-year and lake-to-lake variation in fish Hg concentrations (-14%-121%) after forest harvest in the clearcut lakes, according to our first statistical model that count for fish Hg changes. While the effect ascribed to forest harvest varied between years, after three years (in 2015), a significant increase of 26% (p < 0.0001) in Hg concentrations of large fish was identified in our second statistical model that pooled all 5 clearcut lakes. The large fish Hg concentrations in the 19 reference lakes also varied, and in 2015 had decreased by 7% (p = 0.03) relative to the concentrations in 2010-2011. The majority of the annual changes in fish Hg concentrations in the clearcut lakes after harvest were in the lower range of earlier predictions for high-latitude lakes extrapolated primarily from the effects of forest harvest operations on Hg concentrations in water. Since the risk of forest harvest impacts on Hg extends to fish and not just surface water concentrations, there is even more reason to consider Hg effects in forestry planning, alongside other ecosystem effects.
|
|
| 6. |
- Wu, Pianpian, et al.
(author)
-
Effect of aquaculture on mercury and polyunsaturated fatty acids in fishes from reservoirs in Southwest China
- 2020
-
In: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 257
-
Journal article (peer-reviewed)abstract
- Aquaculture can affect the polyunsaturated fatty acids (PUFA) and mercury (Hg) in fish by altering their diet. Here, planktivorous (silver carp and bighead carp), omnivorous and carnivorous fish with different dietary strategies were selected from two reservoirs, one with on-going aquaculture (WJD) and another without aquaculture (HF) in Southwest China. We compared the total mercury (THg), methylmercury (MeHg) contents and PUFA profiles of fish and their potential diets in these two reservoirs. THg and MeHg contents in omnivorous and carnivorous fish were lower from the WJD Reservoir, which is related to the lower THg and MeHg contents in the artificial fish food. THg and MeHg contents in silver carp from the WJD Reservoir were lower than those from the HF Reservoir, while they were similar in bighead carps from the two reservoirs. The Hg variation in planktivorous fish were inconsistent with that in plankton. THg contents in phyto- and zooplankton from the HF Reservoir were higher than those from the WJD Reservoir, yet their MeHg contents were similar. Artificial fish food which contained higher total PUFA eicosapentaenoic (EPA; 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), significantly increased the total PUFA and EPA + DHA contents in carnivorous fish, but had less effect on that in omnivorous fish from the WJD Reservoir. Eutrophication caused by aquaculture reduced total PUFA and EPA + DHA contents of plankton in WJD, yet did not reduce those in planktivorous fish. The impacts of aquaculture on Hg and PUFA accumulated in fish were varied among different fish species, and the mechanism needs further exploration. (C) 2019 Elsevier Ltd. All rights reserved.
|
|
| 7. |
- Wu, Pianpian, et al.
(author)
-
Elevated temperature and browning increase dietary methylmercury, but decrease essential fatty acids at the base of lake food webs
- 2021
-
In: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
-
Journal article (peer-reviewed)abstract
- Climate change scenarios predict increases in temperature and organic matter supply from land to water, which affect trophic transfer of nutrients and contaminants in aquatic food webs. How essential nutrients, such as polyunsaturated fatty acids (PUFA), and potentially toxic contaminants, such as methylmercury (MeHg), at the base of aquatic food webs will be affected under climate change scenarios, remains unclear. The objective of this outdoor mesocosm study was to examine how increased water temperature and terrestrially-derived dissolved organic matter supply (tDOM; i.e., lake browning), and the interaction of both, will influence MeHg and PUFA in organisms at the base of food webs (i.e. seston; the most edible plankton size for zooplankton) in subalpine lake ecosystems. The interaction of higher temperature and tDOM increased the burden of MeHg in seston (< 40 mu m) and larger sized plankton (microplankton; 40-200 mu m), while the MeHg content per unit biomass remained stable. However, PUFA decreased in seston, but increased in microplankton, consisting mainly of filamentous algae, which are less readily bioavailable to zooplankton. We revealed elevated dietary exposure to MeHg, yet decreased supply of dietary PUFA to aquatic consumers with increasing temperature and tDOM supply. This experimental study provides evidence that the overall food quality at the base of aquatic food webs deteriorates during ongoing climate change scenarios by increasing the supply of toxic MeHg and lowering the dietary access to essential nutrients of consumers at higher trophic levels.
|
|
| 8. |
- Wu, Pianpian, et al.
(author)
-
Investigating the diet source influence on freshwater fish mercury bioaccumulation and fatty acids : experiences from Swedish lakes and Chinese reservoirs
- 2024
-
In: Ecotoxicology. - : Springer Nature. - 0963-9292 .- 1573-3017. ; 33:4-5, s. 415-424
-
Journal article (peer-reviewed)abstract
- Dietary uptake is key for transferring potentially toxic contaminants, such as mercury (Hg) and essential dietary nutrients, such as polyunsaturated fatty acids (PUFA), to consumers at higher trophic levels of aquatic food webs. We evaluated the role of diet sources for Hg bioaccumulation and PUFA retention in fish across lake food webs in seven Swedish lakes and two Chinese reservoirs. Fish total Hg (THg) and methyl-Hg (MeHg) differed greatly between the two countries: the Chinese fish contained less than 300 ng g−1 dry weight (d.w.) THg with less than 50% as MeHg, versus the Swedish fishes which contained approximately 2000 ng g−1 d.w. THg and nearly 100% as MeHg. Fatty acids enrichment of linoleic acids (LIN) were more prevalent in the Chinese fishes regardless of size (p < 0.05). Here we examined food web length, fish growth rates, and fatty acids patterns in relation to the quality of fish as a food source for both Hg and FA. Contrary to the expectation that biodilution of Hg throughout the food chain would explain these differences, a more complex picture emerged with high levels of Hg at the base of the food web in the Chinese reservoirs, a decoupling of fatty acid and Hg bioaccumulation, and a major role for both fish stocking and fish feed. It is hoped that this work will provide a nuanced picture of fish quality as a food source in different ecosystems.
|
|
| 9. |
- Wu, Pianpian
(author)
-
Methylmercury in boreal freshwater food webs
- 2017
-
Doctoral thesis (other academic/artistic)abstract
- Mercury (Hg) and bioaccumulation of its organic form methylmercury (MeHg) has long been regarded as a global issue for human and wildlife health. This is of particular concern for Sweden, where forest harvests and wetlands remain hotspots of MeHg export to boreal freshwaters. The aim of the study was to better understand how environmental change impacts MeHg bioavailability and bioaccumulation with a focus on the base of the food web in Swedish freshwaters. In the thesis, I first examined the impacts of forest harvest on Hg bioaccumulation in fish. From analysis of more than a thousand fish samples from six lakes, it was clear that there was a large variation of fish Hg levels over time and between lakes. The study emphasizes the need for long-term studies to assess the influences on Hg levels in biota. Beaver ponds were also studied to understand the processes influencing MeHg concentrations in water. Increased MeHg production in the sediment was stimulated shortly after flooding by new beaver dams, and that stimulation was related to the quality of the organic carbon. To explore the basis for large discrepancies between aqueous MeHg exposure and the ultimate degree of MeHg bioaccumulation in different aquatic ecosystems, a literature review was conducted on MeHg bioaccumulation from water into the base of the food web. The bioconcentration factor for MeHg, that is the ratio of MeHg concentrations in water and seston or zooplankton, was found to be critical for subsequent MeHg bioaccumulation. To better identify linkages between MeHg uptake and different nutrient sources at the base of the food web, fatty acids were used to distinguish specific diet sources in aquatic primary consumers of plankton and macroinvertebrates. Correlation of Hg bioaccumulation with specific fatty acids confirmed that Hg content increased simultaneously with the retention of polyunsaturated fatty acids in primary consumers. These findings contribute to a better focus on the role of the base of aquatic food webs in transferring MeHg upwards along trophic cascades, as well as landscape influences on elevated MeHg bioaccumulation. Further advances in understanding how the structures at the base of aquatic food webs function with respect to mercury cycling are needed to better predict how changes in the landscape, climate and water chemistry will alter Hg bioaccumulation in fish.
|
|
| 10. |
- Wu, Pianpian, et al.
(author)
-
Terrestrial diet influences mercury bioaccumulation in zooplankton and macroinvertebrates in lakes with differing dissolved organic carbon concentrations
- 2019
-
In: Science of the Total Environment. - : ELSEVIER SCIENCE BV. - 0048-9697 .- 1879-1026. ; 669, s. 821-832
-
Journal article (peer-reviewed)abstract
- Dietary uptake is a key step in conveying both toxic mercury (Hg; particularly as highly bioavailable methylmercury, MeHg) and essential dietary biochemicals, such as polyunsaturated fatty acids (PUFA), across trophic levels within aquatic food webs. Using stable isotopes and fatty acids we evaluated the role of food sources in size-fractioned plankton and littoral macroinvertebrates for the bioaccumulation of total Hg and MeHg in six oligotrophic and one mesotrophic Swedish lakes with differing concentrations of dissolved organic carbon (DOC). We found that the consumption of both algal and terrestrial diets (assessed by PUFA and long-chain saturated fatty acids, respectively) predicted >66% of the Hg concentration variability in meso- (100-500 mu m) and macrozooplankton (>500 mu m) in oligotrophic lakes. In the mesotrophic lake, total Hg bioaccumulation in higher trophic level biota, carnivorous macroinvertebrates was also significantly related to terrestrial diet sources (R-2 = 0.65, p < 0.01). However, lake pH and DOC correlated to total Hg bioaccumulation and bioconcentration across all lakes, suggesting the consumption of different diet sources is mediated by the influence of lake characteristics. This field study reveals that using dietary biomarkers (stable isotopes and fatty acids) together with the physico-chemical lake parameters pH and nutrients together improve our ability to predict Hg bioaccumulation in aquatic food webs. Fatty acids used as dietary biomarkers provide correlative evidence of specific diet source retention in consumers and their effect on Hg bioaccumulation, while pH and nutrients are the underlying physico-chemical lake parameters controlling differences in Hg bioaccumulation between lakes.
|
|
