Influence of Feeding Habits on Organochlorine Contaminant Accumulation in Waterfowl on the Great Lakes

Zebra mussels (Dreissena polymorpha) are an important component of benthic communities in the Great Lakes and are exploited by a host of predators, including waterfowl. In this study, we analyze diet content and stable isotope and organochlorine contaminant patterns in Lesser Scaup (Aythya affinis), Greater Scaup (Aythya marila), Bufflehead (Bucephala albeola), Redhead (Aythya americana), Canvasback (Aythya valisineria), and Mallard (Anas platyrhynchos) collected from three sites (Fighting Island, western Lake Erie, Big Creek) in the lower Great Lakes. Lesser and Greater Scaup from Fighting Island were classified as either zebra mussel ( ≥ 67% of diet) or macrophyte ( ≥ 85% of diet) consumers. Bufflehead, Canvasback, Mallard, and Redhead consumed mainly ( ≥ 89%) macrophyte at Fighting Island. Zebra mussel was the principal food of Lesser Scaup ( \u3e 99%), Greater Scaup (97%), and Bufflehead (72%) in western Lake Erie. Stable isotope analysis revealed enrichment of δ15N in Lesser Scaup ( ≥ 2.24‰), Greater Scaup ( ≥ 1.28‰), and Bufflehead ( ≥ 0.63‰) that exploited mussels relative to conspecifics with macrophyte diets and relative to mussel prey. Representative contaminants of low (hexachlorobenzene [HCB]), moderate (PCB [polychlorinated biphenyl] 153), and high (PCB 180) hydrophobicity were examined in waterfowl. Lipid-normalized concentrations of PCBs 153 and 180 were significantly higher in scaup and Bufflehead that consumed Dreissena than in individuals that ate mainly macrophytes. Among taxa that consumed primarily Dreissena concentrations of PCBs 153 and 180 were significantly higher in individuals from Lake Erie than in those Fighting Island. Principal components analysis revealed broad differences in contaminant patterns of waterfowl based principally on diet. Results from this study illustrate that Dreissena has become a primary food source of some waterfowl in the lower Great Lakes and serves as an effective conduit for transfer of persistent organic contaminants to higher trophic levels

Multiple tracers demonstrate distinct sources of dissolved organic matter to lakes of the Mackenzie Delta, western Canadian Arctic

Author Posting. © American Society of Limnology and Oceanography, 2011. This article is posted here by permission of American Society of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 56 (2011): 1297-1309, doi:10.4319/lo.2011.56.4.1297.Lakes of the Mackenzie Delta occur across a gradient that contains three clear end members: those that remain connected to river-water channels throughout the summer; those that receive only brief inputs of river water during an annual spring flood but contain dense macrophyte stands; and those that experience significant permafrost thaw along their margins. We measured dissolved organic carbon (DOC) concentration, dissolved organic matter (DOM) absorption and fluorescence, and stable isotopes of DOM, DOM precursor materials, and bacteria to elucidate the importance of river water, macrophytes, and thermokarst as DOM sources to Mackenzie Delta lakes. Despite standing stocks of macrophyte C that are sevenfold to 12-fold greater than those of total DOC, stable isotopes indicated that autochthonous sources contributed less than 15% to overall DOM in macrophyte-rich lakes. Instead, fluorescence and absorption indicated that the moderate summertime increase in DOC concentration in macrophyte-rich lakes was the result of infrequent flushing, while bacterial δ13C indicated rapid bacterial removal of autochthonous DOC from the water column. In thermokarst lakes, summertime increases in DOC concentration were substantial, and stable isotopes indicated that much of this increase came from C released as a result of thermokarst-related processes. Our results indicate that these distinct sources of DOM to neighboring arctic Delta lakes may drive between-lake differences in C cycling and energy flow. Rapidly assimilated macrophyte DOM should be an important contributor to microbial food webs in our study lakes. In contrast, the accumulation of thermokarst-origin DOM allows for a significant role in physico-chemistry but indicates a lesser contribution of this DOM to higher trophic levels.This study was supported by a Discovery Grant and Northern Research Supplement from the Natural Sciences and Engineering Research Council of Canada (NSERC) to L.F.W.L.; funds from the Science Horizons Youth Internship Program, Northern Scientific Training Program, and NSERC Northern Research Internship. Personal financial support to S.E.T. was provided by a Simon Fraser University CD Nelson Memorial Graduate Scholarship, an NSERC Canada Graduate Scholarship-Doctoral, and a Garfield Weston Award for Northern Research

Evaluating Ecological Sustainability For The Planning and Operations Of Storage Technologies

With an expected future increase of costs for carbon emissions the logistics industry is targeting to design sustainable warehouses to reduce their carbon footprints. To do so, it is required that every aspect of a warehouse from its general design to the transport processes and technologies must be assessed in terms of its carbon footprint. In this article the carbon footprint, which can be traced back to the storage technology employed within a storage area is analysed. The approach includes surface, material, and technology-related data to calculate the carbon footprint of a logistics concept. Firstly, different dimensions of storage technology carbon footprints are identified. A comprehen-sive model is provided to calculate the carbon footprint of alternative storage technologies in a warehouse. The model is applied in a case study with actual data from a warehouse planning project in the German production industry comparing three alternative storage technologies for a small part storage solution. The author's find highest carbon footprint in the application of an autonomous guided vehicle shelving system compared to automatic storage and retrieval system and manual storage solution using Kanban racks

Contribution of anadromous fish to the diet of European catfish in a large river system

Many anadromous fish species, when migrating from the sea to spawn in fresh waters, can potentially be a valuable prey for larger predatory fish, thereby efficiently linking these two ecosystems. Here, we assess the contribution of anadromous fish to the diet of European catfish (Silurus glanis) in a large river system (Garonne, southwestern France) using stable isotope analysis and allis shad (Alosa alosa) as an example of anadromous fish. Allis shad caught in the Garonne had a very distinct marine delta(13)C value, over 8 per thousand higher after lipid extraction compared to the mean delta(13)C value of all other potential freshwater prey fish. The delta(13)C values of European catfish varied considerably between these two extremes and some individuals were clearly specializing on freshwater prey, whereas others specialized on anadromous fish. The mean contribution of anadromous fish to the entire European catfish population was estimated to be between 53% and 65%, depending on the fractionation factor used for delta(13)C

Ligand dimensions are important in controlling NK-cell responses

Size-dependent protein segregation at the cell–cell contact interface has been suggested to be critical for regulation of lymphocyte function. We investigated the role of ligand dimensions in regulation of mouse NK-cell activation and inhibition. Elongated forms of H60a, a mouse NKG2D ligand, were generated and expressed stably in the RMA cell line. RMA cells expressing the normal size H60a were lysed efficiently by both freshly isolated and IL-2 stimulated C57BL/6 mouse-derived NK cells; however the level of lysis decreased as the H60a ligand size increased. Importantly, H60a elongation did not affect NKG2D binding, as determined by soluble NKG2D tetramer staining, and by examining NK-cell target cell conjugate formation. CHO cells are efficient at activating NK cells from C57BL/6 mice, and expression of a single chain form of H-2Kb, a ligand for the mouse inhibitory receptor Ly49C, strongly inhibited such activation of Ly49C/I positive NK cells. Elongation of H-2Kb resulted in decreased inhibition of both lysis and IFN-γ production by NK cells. These results establish that small ligand dimensions are important for both NK-cell activation and inhibition, and suggest that there are shared features between the mechanisms of receptor triggering on different types of lymphocytes

Ly49H signaling through DAP10 is essential for optimal natural killer cell responses to mouse cytomegalovirus infection

The activating natural killer (NK) cell receptor Ly49H recognizes the mouse cytomegalovirus (MCMV) m157 glycoprotein expressed on the surface of infected cells and is required for protection against MCMV. Although Ly49H has previously been shown to signal via DAP12, we now show that Ly49H must also associate with and signal via DAP10 for optimal function. In the absence of DAP12, DAP10 enables Ly49H-mediated killing of m157-bearing target cells, proliferation in response to MCMV infection, and partial protection against MCMV. DAP10-deficient Ly49H+ NK cells, expressing only Ly49H–DAP12 receptor complexes, are partially impaired in their ability to proliferate during MCMV infection, display diminished ERK1/2 activation, produce less IFN-γ upon Ly49H engagement, and demonstrate reduced control of MCMV infection. Deletion of both DAP10 and DAP12 completely abrogates Ly49H surface expression and control of MCMV infection. Thus, optimal NK cell–mediated immunity to MCMV depends on Ly49H signaling through both DAP10 and DAP12

Distinct contracted conformations of the Tcra/Tcrd locus during Tcra and Tcrd recombination

Studies have suggested that antigen receptor loci adopt contracted conformations to promote long-distance interactions between gene segments during V(D)J recombination. The Tcra/Tcrd locus is unique because it undergoes highly divergent Tcrd and Tcra recombination programs in CD4−CD8− double negative (DN) and CD4+CD8+ double positive (DP) thymocytes, respectively. Using three-dimensional fluorescence in situ hybridization, we asked whether these divergent recombination programs are supported by distinct conformational states of the Tcra/Tcrd locus. We found that the 3′ portion of the locus is contracted in DN and DP thymocytes but not in B cells. Remarkably, the 5′ portion of the locus is contracted in DN thymocytes but is decontracted in DP thymocytes. We propose that the fully contracted conformation in DN thymocytes allows Tcrd rearrangements involving Vδ gene segments distributed over 1 Mb, whereas the unique 3′-contracted, 5′-decontracted conformation in DP thymocytes biases initial Tcra rearrangements to the most 3′ of the available Vα gene segments. This would maintain a large pool of distal 5′ Vα gene segments for subsequent rounds of recombination. Thus, distinct contracted conformations of the Tcra/Tcrd locus may facilitate a transition from a Tcrd to a Tcra mode of recombination during thymocyte development

A Functional Analysis of the Spacer of V(D)J Recombination Signal Sequences

During lymphocyte development, V(D)J recombination assembles antigen receptor genes from component V, D, and J gene segments. These gene segments are flanked by a recombination signal sequence (RSS), which serves as the binding site for the recombination machinery. The murine Jβ2.6 gene segment is a recombinationally inactive pseudogene, but examination of its RSS reveals no obvious reason for its failure to recombine. Mutagenesis of the Jβ2.6 RSS demonstrates that the sequences of the heptamer, nonamer, and spacer are all important. Strikingly, changes solely in the spacer sequence can result in dramatic differences in the level of recombination. The subsequent analysis of a library of more than 4,000 spacer variants revealed that spacer residues of particular functional importance are correlated with their degree of conservation. Biochemical assays indicate distinct cooperation between the spacer and heptamer/nonamer along each step of the reaction pathway. The results suggest that the spacer serves not only to ensure the appropriate distance between the heptamer and nonamer but also regulates RSS activity by providing additional RAG:RSS interaction surfaces. We conclude that while RSSs are defined by a “digital” requirement for absolutely conserved nucleotides, the quality of RSS function is determined in an “analog” manner by numerous complex interactions between the RAG proteins and the less-well conserved nucleotides in the heptamer, the nonamer, and, importantly, the spacer. Those modulatory effects are accurately predicted by a new computational algorithm for “RSS information content.” The interplay between such binary and multiplicative modes of interactions provides a general model for analyzing protein–DNA interactions in various biological systems