Methylmercury in boreal freshwater food webs

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

Elevated temperature and browning increase dietary methylmercury, but decrease essential fatty acids at the base of lake food webs

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 (\u3c 40 μm) and larger sized plankton (microplankton; 40–200 μm), 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

Elevated temperature and browning increase dietary methylmercury, but decrease essential fatty acids at the base of lake food webs

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

Beneficial yet Risky : Evaluate Risks of Fish Diet of Mercury Exposure to Consumers in Sweden

            For a long time, fish is regarded as an important food source beneficial for human health. But there’s nowadays an increasing concern of fish consumption for increasing existence of mercury (Hg) and methylmercury (MeHg), which can be accumulated upon fish intake and pose health threats to human.  It is suggested that children and pregnant women are more vulnerable to effects due to accumulation of Hg. There have been continuous efforts done by governments and researchers all over the world, e.g. publishing national and regional advisories on fish consumption, in order to inform public related risks aroused by excess fish consumption. Sweden, as one of the earliest countries abandons the use of Hg (Regeringskansliet, http://www.sweden.gov.se), has published a national advisory on fish consumption for pregnant and breastfeeding women (Swedish National Food Agency, SLV, http://www.slv.se/). Hg level in edible fish organs is also limited for safe consumption.  In order to picture a better image of this, we investigated existed databases in Sweden on Hg levels in fish, fishery statistics, consumption data, and observed Hg level in human in recent decades for human exposure to Hg in Sweden. Though mercury emission decreased, the exposure to mercury via fish consumption is still high. We believe there’s a potential risk for Swedish inhabitants, especially pregnant women and women in breastfeeding, as well as young children. It is strongly recommended a safer limit of Hg in fish products for consumption in Sweden.             We hope for more synthesized knowledge of safe fish consumption that benefit for the public and promote regional/national policy in having an up-to-date fish consumption advisory in Sweden

Risks of Cadmium Nanoparticles on Estuarine Organisms : Ecotoxicological Effects of Engineered Cadmium Nanoparticles through Biochemical and Behavioral Responses in Two Marine Invertebrates, Nereis diversicolor and Scrobicularia plana

There is an increasing concern over the safety of engineered nanoparticles (ENPs) to humans and the environment. It is important that the environmental risks of these particles to be tested under research and regulatory schemes, e.g. Nano Risks to the environment &amp; Human Health (NanoReTox) under Seventh Framework Programme (FP7) in EU. Due to their unique properties and the fact that their detection and characterization in complex matrices is challenging, classic analytical methods and test approaches for assessing environmental risk may not be appropriate for ENPs. In this paper I present the challenges associated with ENPs exposure to the estuarine environment and the testing of a chosen ENPs to generate data on ecotoxicity in the test estuarine organisms for further consideration of risk assessment of marine environment. Careful consideration was given to the selection of the test materials (benthic organisms Nereis diversicolor and Scrobicularia plana), the test system and the test exposure conditions (CdS ENPs and aqueous CdS added to filtered natural seawater with a concentration of 10 µg L-1). Evaluation of the exposure effects was carried out by behavioral tests (burrowing kinetics and feeding rate) and biochemical responses (quantification of biomarkers). Multispecies Freshwater Biomonitor®  (MFB) tests and GST analysis results show significant differences in between control group and CdS NPs exposure one, indicating that CdS NPs are potential to cause sublethal effects in test organisms. Our knowledge in environmental risk assessment of ENPs is still limited. Coordinated research is required to gain a better understanding of the factors and processes affecting ENP fate and effects in the environment as well as to develop more usable, robust and sensitive methods for characterization and detection of ENPs in environmental systems.NanoReTox, FP7 NMP Work Programm

Beneficial yet Risky : Evaluate Risks of Fish Diet of Mercury Exposure to Consumers in Sweden

            For a long time, fish is regarded as an important food source beneficial for human health. But there’s nowadays an increasing concern of fish consumption for increasing existence of mercury (Hg) and methylmercury (MeHg), which can be accumulated upon fish intake and pose health threats to human.  It is suggested that children and pregnant women are more vulnerable to effects due to accumulation of Hg. There have been continuous efforts done by governments and researchers all over the world, e.g. publishing national and regional advisories on fish consumption, in order to inform public related risks aroused by excess fish consumption. Sweden, as one of the earliest countries abandons the use of Hg (Regeringskansliet, http://www.sweden.gov.se), has published a national advisory on fish consumption for pregnant and breastfeeding women (Swedish National Food Agency, SLV, http://www.slv.se/). Hg level in edible fish organs is also limited for safe consumption.  In order to picture a better image of this, we investigated existed databases in Sweden on Hg levels in fish, fishery statistics, consumption data, and observed Hg level in human in recent decades for human exposure to Hg in Sweden. Though mercury emission decreased, the exposure to mercury via fish consumption is still high. We believe there’s a potential risk for Swedish inhabitants, especially pregnant women and women in breastfeeding, as well as young children. It is strongly recommended a safer limit of Hg in fish products for consumption in Sweden.             We hope for more synthesized knowledge of safe fish consumption that benefit for the public and promote regional/national policy in having an up-to-date fish consumption advisory in Sweden

Risks of Cadmium Nanoparticles on Estuarine Organisms : Ecotoxicological Effects of Engineered Cadmium Nanoparticles through Biochemical and Behavioral Responses in Two Marine Invertebrates, Nereis diversicolor and Scrobicularia plana

There is an increasing concern over the safety of engineered nanoparticles (ENPs) to humans and the environment. It is important that the environmental risks of these particles to be tested under research and regulatory schemes, e.g. Nano Risks to the environment &amp; Human Health (NanoReTox) under Seventh Framework Programme (FP7) in EU. Due to their unique properties and the fact that their detection and characterization in complex matrices is challenging, classic analytical methods and test approaches for assessing environmental risk may not be appropriate for ENPs. In this paper I present the challenges associated with ENPs exposure to the estuarine environment and the testing of a chosen ENPs to generate data on ecotoxicity in the test estuarine organisms for further consideration of risk assessment of marine environment. Careful consideration was given to the selection of the test materials (benthic organisms Nereis diversicolor and Scrobicularia plana), the test system and the test exposure conditions (CdS ENPs and aqueous CdS added to filtered natural seawater with a concentration of 10 µg L-1). Evaluation of the exposure effects was carried out by behavioral tests (burrowing kinetics and feeding rate) and biochemical responses (quantification of biomarkers). Multispecies Freshwater Biomonitor®  (MFB) tests and GST analysis results show significant differences in between control group and CdS NPs exposure one, indicating that CdS NPs are potential to cause sublethal effects in test organisms. Our knowledge in environmental risk assessment of ENPs is still limited. Coordinated research is required to gain a better understanding of the factors and processes affecting ENP fate and effects in the environment as well as to develop more usable, robust and sensitive methods for characterization and detection of ENPs in environmental systems.NanoReTox, FP7 NMP Work Programm

Beneficial yet Risky : Evaluate Risks of Fish Diet of Mercury Exposure to Consumers in Sweden

            For a long time, fish is regarded as an important food source beneficial for human health. But there’s nowadays an increasing concern of fish consumption for increasing existence of mercury (Hg) and methylmercury (MeHg), which can be accumulated upon fish intake and pose health threats to human.  It is suggested that children and pregnant women are more vulnerable to effects due to accumulation of Hg. There have been continuous efforts done by governments and researchers all over the world, e.g. publishing national and regional advisories on fish consumption, in order to inform public related risks aroused by excess fish consumption. Sweden, as one of the earliest countries abandons the use of Hg (Regeringskansliet, http://www.sweden.gov.se), has published a national advisory on fish consumption for pregnant and breastfeeding women (Swedish National Food Agency, SLV, http://www.slv.se/). Hg level in edible fish organs is also limited for safe consumption.  In order to picture a better image of this, we investigated existed databases in Sweden on Hg levels in fish, fishery statistics, consumption data, and observed Hg level in human in recent decades for human exposure to Hg in Sweden. Though mercury emission decreased, the exposure to mercury via fish consumption is still high. We believe there’s a potential risk for Swedish inhabitants, especially pregnant women and women in breastfeeding, as well as young children. It is strongly recommended a safer limit of Hg in fish products for consumption in Sweden.             We hope for more synthesized knowledge of safe fish consumption that benefit for the public and promote regional/national policy in having an up-to-date fish consumption advisory in Sweden

Morphology and structure of Homo erectus humeri from Zhoukoudian, Locality 1

Background Regional diversity in the morphology of the H. erectus postcranium is not broadly documented, in part, because of the paucity of Asian sites preserving postcranial fossils. Yet, such an understanding of the initial hominin taxon to spread throughout multiple regions of the world is fundamental to documenting the adaptive responses to selective forces operating during this period of human evolution. Methods The current study reports the first humeral rigidity and strength properties of East Asian H. erectus and places its diaphyseal robusticity into broader regional and temporal contexts. We estimate true cross-sectional properties of Zhoukoudian Humerus II and quantify new diaphyseal properties of Humerus III using high resolution computed tomography. Comparative data for African H. erectus and Eurasian Late Pleistocene H. sapiens were assembled, and new data were generated from two modern Chinese populations. Results Differences between East Asian and African H. erectus were inconsistently expressed in humeral cortical thickness. In contrast, East Asian H. erectus appears to exhibit greater humeral robusticity compared to African H. erectus when standardizing diaphyseal properties by the product of estimated body mass and humeral length. East Asian H. erectus humeri typically differed less in standardized properties from those of side-matched Late Pleistocene hominins (e.g., Neanderthals and more recent Upper Paleolithic modern humans) than did African H. erectus, and often fell in the lower range of Late Pleistocene humeral rigidity or strength properties. Discussion Quantitative comparisons indicate that regional variability in humeral midshaft robusticity may characterize H. erectus to a greater extent than presently recognized. This may suggest a temporal difference within H. erectus, or possibly different ecogeographical trends and/or upper limb loading patterns across the taxon. Both discovery and analysis of more adult H. erectus humeri are critical to further evaluating and potentially distinguishing between these possibilities