Bioaccumulation and Biomagnification of Mercury and Methylmercury in Four Sympatric Coastal Sharks in a Protected Subtropical Lagoon

Mercury bioaccumulation is frequently observed in marine ecosystems, often with stronger effects at higher trophic levels. We compared total mercury (THg) and methylmercury (MeHg) from muscle with length, comparative isotopic niche, and diet (via δ13C and δ15N) among four sympatric coastal sharks in Florida Bay (USA): blacknose, blacktip, bull, and lemon. Mercury in blacknose and blacktip sharks increased significantly with size, whereas bull and lemon sharks had a high variance in mercury relative to size. Both δ13C and δ15N were consistent with general resource use and trophic position relationships across all species. A significant relationship was observed between δ13C and mercury in blacktip sharks, suggesting an ontogenetic shift isotopic niche, possibly a dietary change. Multiple regression showed that δ13C and δ15N were the strongest factors regarding mercury bioaccumulation in individuals across all species. Additional research is recommended to resolve the mechanisms that determine mercury biomagnification in individual shark species

Nutrient Supply and Mercury Dynamics in Marine Ecosystems: A Conceptual Model

There is increasing interest and concern over the impacts of mercury (Hg) inputs to marine 32 ecosystems. One of the challenges in assessing these effects is that the cycling and trophic 33 transfer of Hg are strongly linked to other contaminants and disturbances. In addition to Hg, a 34 major problem facing coastal waters is the impacts of elevated nutrient, particularly nitrogen 35 (N), inputs. Increases in nutrient loading alter coastal ecosystems in ways that should change 36 the transport, transformations and fate of Hg, including increases in fixation of organic carbon 37 and deposition to sediments, decreases in the redox status of sediments and changes in fish 38 habitat. In this paper we present a conceptual model which suggests that increases in loading 39 of reactive N to marine ecosystems might alter Hg dynamics, decreasing bioavailabilty and 40 trophic transfer. This conceptual model is most applicable to coastal waters, but may also be 41 relevant to the pelagic ocean. We present information from case studies that both support and 42 challenge this conceptual model, including marine observations across a nutrient gradient; 43 results of a nutrient‐trophic transfer Hg model for pelagic and coastal ecosystems; observations 44 of Hg species, and nutrients from coastal sediments in the northeastern U.S.; and an analysis of 45 fish Hg concentrations in estuaries under different nutrient loadings. These case studies suggest 46 that changes in nutrient loading can impact Hg dynamics in coastal and open ocean ecosystems. 47 Unfortunately none of the case studies is comprehensive; each only addresses a portion of the 48 conceptual model and has limitations. Nevertheless, our conceptual model has important 49 management implications. Many estuaries near developed areas are impaired due to elevated 50 nutrient inputs. Widespread efforts are underway to control N loading and restore coastal 51 ecosystem function. An unintended consequence of nutrient control measures could be to 3 exacerbate 52 problems associated with Hg contamination. Additional focused research and 53 monitoring are needed to critically examine the link between nutrient supply and Hg 54 contamination of marine waters

Thermal conductivity measurement of liquids in a microfluidic device

A new microfluidic-based approach to measuring liquid thermal conductivity is developed to address the requirement in many practical applications for measurements using small (microlitre) sample size and integration into a compact device. The approach also gives the possibility of high-throughput testing. A resistance heater and temperature sensor are incorporated into a glass microfluidic chip to allow transmission and detection of a planar thermal wave crossing a thin layer of the sample. The device is designed so that heat transfer is locally one-dimensional during a short initial time period. This allows the detected temperature transient to be separated into two distinct components: a short-time, purely one-dimensional part from which sample thermal conductivity can be determined and a remaining long-time part containing the effects of three-dimensionality and of the finite size of surrounding thermal reservoirs. Identification of the one-dimensional component yields a steady temperature difference from which sample thermal conductivity can be determined. Calibration is required to give correct representation of changing heater resistance, system layer thicknesses and solid material thermal conductivities with temperature. In this preliminary study, methanol/water mixtures are measured at atmospheric pressure over the temperature range 30–50°C. The results show that the device has produced a measurement accuracy of within 2.5% over the range of thermal conductivity and temperature of the tests. A relation between measurement uncertainty and the geometric and thermal properties of the system is derived and this is used to identify ways that error could be further reduced

Jung und Alt im Hörsaal:Erfahrungen jüngerer Studierender mit dem „Studium im Alter“ an der Universität Münster

Das „Studium im Alter“ ist ein Weiterbildungsangebot der Universität Münster für Personen im mittleren und höheren Lebensalter, die als Gasthörer gemeinsam mit jüngeren, regulären Studierenden Vorlesungen und Seminare an der Hochschule besuchen. In der Presse erschienen von Zeit zu Zeit Berichte über Konflikte, die das Gaststudium der Älteren in den Hörsälen verursacht. Das nahm eine Gruppe von Teilnehmern am „Studium im Alter“ zum Anlass, in einem zweisemestrigen Forschungsprojekt zu untersuchen, inwiefern solche Berichte die Regel oder Einzelfälle beschreiben. Das Ergebnis der schriftlichen Befragung regulärer Studierender zu Ihren Erfahrungen mit Studierenden im Alter liegt mit dieser Studie vor. Abgesehen von wenigen Ausnahmen belegt sie ein grundsätzlich harmonisches Miteinander von jüngeren und älteren Studierenden in den Hörsälen der Universität Münster

What are the evolutionary constraints on larval growth in a trophically transmitted parasite?

For organisms with a complex life cycle, a large larval size is generally beneficial, but it may come at the expense of prolonged development. Individuals that grow fast may avoid this tradeoff and switch habitats at both a larger size and younger age. A fast growth rate itself can be costly, however, as it requires greater resource intake. For parasites, fast larval growth is assumed to increase the likelihood of host death before transmission to the next host occurs. Using the tapeworm Schistocephalus solidus in its copepod first intermediate host, I investigated potential constraints in the parasite’s larval life history. Fast-growing parasites developed infectivity earlier, indicating there is no functional tradeoff between size and developmental time. There was significant growth variation among full-sib worm families, but fast-growing sibships were not characterized by lower host survival or more predation-risky host behavior. Parental investment also had little effect on larval growth rates. The commonly assumed constraints on larval growth and development were not observed in this system, so it remains unclear what prevents worms from exploiting their intermediate hosts more aggressively

Toxicity of dietary methylmercury to fish: Derivation of ecologically meaningful threshold concentrations

Threshold concentrations associated with adverse effects of dietary exposure to methylmercury (MeHg) were derived from published results of laboratory studies on a variety of fish species. Adverse effects related to mortality were uncommon, whereas adverse effects related to growth occurred only at dietary MeHg concentrations exceeding 2.5 µg g −1 wet weight. Adverse effects on behavior of fish had a wide range of effective dietary concentrations, but generally occurred above 0.5 µg g −1 wet weight. In contrast, effects on reproduction and other subclinical endpoints occurred at dietary concentrations that were much lower (<0.2 µg g −1 wet wt). Field studies generally lack information on dietary MeHg exposure, yet available data indicate that comparable adverse effects have been observed in wild fish in environments corresponding to high and low MeHg contamination of food webs and are in agreement with the threshold concentrations derived here from laboratory studies. These thresholds indicate that while differences in species sensitivity to MeHg exposure appear considerable, chronic dietary exposure to low concentrations of MeHg may have significant adverse effects on wild fish populations but remain little studied compared to concentrations in mammals or birds. Environ. Toxicol. Chem. 2012; 31: 1536–1547. © 2012 SETACPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92130/1/etc_1859_sm_SupplReferences.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/92130/2/1859_ftp.pd

CD27 is required for protective lytic EBV antigen-specific CD8+ T-cell expansion

Primary immunodeficiencies in the costimulatory molecule CD27 and its ligand, CD70, predispose for pathologies of uncontrolled Epstein-Barr virus (EBV) infection in nearly all affected patients. We demonstrate that both depletion of CD27+ cells and antibody blocking of CD27 interaction with CD70 cause uncontrolled EBV infection in mice with reconstituted human immune system components. While overall CD8+ T-cell expansion and composition are unaltered after antibody blocking of CD27, only some EBV-specific CD8+ T-cell responses, exemplified by early lytic EBV antigen BMLF1-specific CD8+ T cells, are inhibited in their proliferation and killing of EBV-transformed B cells. This suggests that CD27 is not required for all CD8+ T-cell expansions and cytotoxicity but is required for a subset of CD8+ T-cell responses that protect us from EBV pathology

Fishery management plan series

Management plan discussing the three shrimp species found in the Gulf of Mexico and how to best utilize these resources for Texas