Interactive effects of phosphorus and copper on Hyalella azteca and periphyton

Eutrophication is known to be frequently associated with metal pollution in aquatic ecosystems. This research examined the interaction between dissolved copper and phosphorus, with respect to their effects on the growth of a freshwater amphipod Hyalella azteca feeding on periphyton. The study design included two tiers: (1) a laboratory stream experiment where natural periphyton communities accumulated Cu under a gradient of Cu and P concentrations; and (2) a beaker experiment where H.azteca were exposed to water and periphyton from laboratory streams. There was rapid Cu accumulation by periphyton but the total Cu concentration of periphyton was not directly related to the dissolved P treatment in the stream experiment. In terms of Hyalella growth, an interactive effect was found between Cu and P as high phosphorus concentration was related to reduced growth at relatively lower Cu concentration. Our findings suggest that eutrophication may result in greater Cu toxicity to benthic macroinvertebrates as a result of dietary exposure from periphyton.  Master of ScienceNatural Resources and EnvironmentUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/85782/1/Miling Li Thesis.pd

Decadal Changes in the Edible Supply of Seafood and Methylmercury Exposure in the United States

Background: Methylmercury (MeHg) exposure is associated with adverse effects on neurodevelopment and cardiovascular health. Previous work indicates most MeHg is from marine fish sold in the commercial market, but does not fully resolve supply regions globally. This information is critical for linking changes in environmental MeHg levels to human exposure in the U.S. population. Objectives: We used available data to estimate the geographic origins of seafood consumed in the United States (major ocean basins, coastal fisheries, aquaculture, freshwater) and how shifts in edible supply affected MeHg exposures between 2000–2002 and 2010–2012. Methods: Source regions for edible seafood and MeHg exposure in the United States were characterized from national and international landing, export and import data from the Food and Agricultural Organization of the United Nations and the U.S. National Marine Fisheries Service. Results: Our analysis suggests 37% of U.S. population-wide MeHg exposure is from mainly domestic coastal systems and 45% from open ocean ecosystems. We estimate that the Pacific Ocean alone supplies more than half of total MeHg exposure. Aquaculture and freshwater fisheries together account for an estimated 18% of total MeHg intake. Shifts in seafood types and supply regions between 2000–2002 and 2010–2012 reflect changes in consumer preferences (e.g., away from canned light meat tuna), global ecosystem shifts (e.g., northern migration of cod stocks), and increasing supply from aquaculture (e.g., shrimp and salmon). Conclusion: Our findings indicate global actions that reduce anthropogenic Hg emissions will be beneficial for U.S. seafood consumers because open ocean ecosystems supply a large fraction of their MeHg exposure. However, our estimates suggest that domestic actions can provide the greatest benefit for coastal seafood consumers. https://doi.org/10.1289/EHP264

Detection and differentiation of Borrelia burgdorferi sensu lato in ticks collected from sheep and cattle in China

<p>Abstract</p> <p>Background</p> <p>Lyme disease caused by <it>Borrelia burgdorferi </it>sensu lato complex is an important endemic zoonosis whose distribution is closely related to the main ixodid tick vectors. In China, isolated cases of Lyme disease infection of humans have been reported in 29 provinces. Ticks, especially ixodid ticks are abundant and a wide arrange of <it>Borrelia </it>natural reservoirs are present. In this study, we developed a reverse line blot (RLB) to identify <it>Borrelia </it>spp. in ticks collected from sheep and cattle in 7 Provinces covering the main extensive livestock regions in China.</p> <p>Results</p> <p>Four species-specific RLB oligonucleotide probes were deduced from the spacer region between the 5S-23S rRNA gene, along with an oligonucleotide probe which was common to all. The species specific probes were shown to discriminate between four genomic groups of <it>B. burgdorferi </it>sensu lato i.e. <it>B. burgdorferi </it>sensu stricto, <it>B. garinii, B. afzelii</it>, and <it>B. valaisiana</it>, and to bind only to their respective target sequences, with no cross reaction to non target DNA. Furthermore, the RLB could detect between 0.1 pg and 1 pg of <it>Borrelia </it>DNA.</p> <p>A total of 723 tick samples (<it>Haemaphysalis, Boophilus, Rhipicephalus </it>and <it>Dermacentor</it>) from sheep and cattle were examined with RLB, and a subset of 667 corresponding samples were examined with PCR as a comparison. The overall infection rate detected with RLB was higher than that of the PCR test.</p> <p>The infection rate of <it>B. burgdoreri </it>sensu stricto was 40% in south areas; while the <it>B. garinii infection rate </it>was 40% in north areas. The highest detection rates of <it>B. afzelii </it>and <it>B. valaisiana </it>were 28% and 22%, respectively. Mixed infections were also found in 7% of the ticks analyzed, mainly in the North. The proportion of <it>B. garinii </it>genotype in ticks was overall highest at 34% in the whole investigation area.</p> <p>Conclusion</p> <p>In this study, the RLB assay was used to detect <it>B. burgdorferi </it>sensu lato in ticks collected from sheep and cattle in China. The results showed that <it>B. burdorferi senso stricto </it>and <it>B. afzelii </it>were mainly distributed in the South; while <it>B. garinii </it>and <it>B. valaisiana </it>were dominant in the North. <it>Borrelia </it>spirochaetes were detected in <it>Rhipicephalus </it>spp for the first time. It is suggested that the <it>Rhipicephalus </it>spps might play a role in transmitting <it>Borrelia </it>spirochaetes.</p

Hg isotope in fish

Compiled Hg isotope data of world fish, shellfish, marine mammals

Environmental Origins of Methylmercury in Aquatic Biota and Humans

Methylmercury (MeHg) is a neurotoxin found in fish and shellfish, that poses risks to human and ecological health. Exposure to MeHg adversely affects neurodevelopment of children and cardiovascular health in adults. Seafood consumption is the primary exposure route to MeHg in North America. An understanding of the link between environmental MeHg sources and human exposures is needed to determine the impacts of ongoing environmental change. However, few data exist for relating environmental exposures to human health outcomes. Imprecision in dietary recall data on fish consumption and variability in MeHg concentrations within and across seafood species consumed have made it challenging to accurately identify sources of human MeHg exposure. In addition, the diverse environmental sources of MeHg production in ecosystems make it more difficult to quantitatively attribute human exposures to specific environments where methylation is taking place. My doctoral dissertation uses naturally occurring mercury (Hg) stable isotopes to characterize sources of MeHg exposure in aquatic biota and human populations. The objectives of my work are to (1) explore the utility of Hg stable isotopes in human hair as a novel method for tracing sources of MeHg exposure to humans; (2) examine drivers of the internal body burden of MeHg in frequent seafood consumers; (3) refine understanding of environmental MeHg sources for estuarine fish. My first dissertation chapter characterizes the magnitude of mass-dependent fractionation between seafood and consumers and shows Hg stable isotopes in human hair is a promising tool for estimating different Hg exposure sources (e.g., coastal vs. oceanic fish). My second chapter uses dietary survey data and Hg isotopes in hair from high-frequency seafood consumers to show that differences in in vivo demethylation do not explain variability in biomarker concentrations. I infer that absorption efficiencies for MeHg in seafood are very low for some high-frequency fish consumers and hypothesize that this is caused by interactions with co-ingested foods. The last chapter investigates diverse Hg stable isotope signatures in benthic, riverine and pelagic estuarine fish and uses these signatures to better characterize the relative importance of different environmental MeHg sources.Methylmercury; Source; Exposure; Human; Aquatic biota

Hg isotope in fish

Compiled Hg isotope data of world fish, shellfish, marine mammals

Making a Place for the Next Generation of Geoscientists

Early-career scientists from the AGU Mentoring Network discuss how the global pandemic has exacerbated long-standing issues with the availability of positions in and the diversity of the geosciences.</jats:p