Cladocera in shallow lakes from the Ecuadorian Andes show little response to recent climate change

Floating-leaved rhizophytes and pleustophytes are the first barrier to Sun’s rays and significantly affect the light regime of the water column. To evaluate these effects on light attenuation, the reflectance and transmittance spectra variability were examined according to the leaf traits within three plant groups: (1) seed plants with green abaxial surfaces; (2) seed plants with red abaxial surfaces; and (3) ferns with trichomes. Specific leaf area (SLA), chlorophyll a and b, and UV-B and UV-A-absorbing substances differed between these three groups. The ‘spectral signatures’ of floating-leaved seed plants are similar to those of terrestrial seed plants, with a peak in the green region and a pronounced ‘red edge’. Ferns transmitted more light along the whole spectrum compared to other species. Most reflectance and transmittance spectra variability of the first group was explained by SLA. In the second group, 36% of the reflectance spectra variability was explained by tissue density and carotenoids, and 48% of the transmittance spectra variability by carotenoids, anthocyanins and SLA. In ferns, the reflectance spectra variability was mainly explained by chlorophylls, and partly by trichome length and mesophyll thickness, with the transmittance spectra variability significantly affected by chlorophyll b.     

Seabird-driven shifts in Arctic pond ecosystems

Migratory animals such as seabirds, salmon and whales can transport large quantities of nutrients across ecosystem boundaries, greatly enriching recipient food webs. As many of these animals biomagnify contaminants, they can also focus pollutants at toxic levels. Seabirds arguably represent the most significant biovectors of nutrients and contaminants from the ocean to the land, given their sheer numbers and global distribution. However, long-term census data on seabirds are rare. Using palaeolimnological proxies, we show that a colony of Arctic seabirds has experienced climate-induced population increases in recent decades. We then document increasing concentrations of contaminants, including polychlorinated biphenyls and cadmium, in pond sediments that are linked to biotransport by seabirds. Our findings suggest that climate-related shifts in global seabird populations will have the unexpected consequence of restructuring coastal ecosystems.     

Surveys reveal a complex association of phytoplasmas and viruses with the blueberry stunt disease on Canadian blueberry farms

Surveys for phytoplasmas and viruses were conducted during September 2014 and 2015 on highbush blueberry farms in the Région Montérégie, Quebec. Total DNA and RNA were extracted from blueberry bushes showing blueberry stunt (BBS) symptoms and from symptomless blueberry bushes, and utilised as templates for PCR and RT‐PCR assays, respectively. Phytoplasma DNA was amplified with universal phytoplasma primers that target the 16S rRNA, secA and secY genes from 12 out of 40 (30%) plants tested. Based on 16S rRNA, secA and secY gene sequence identity, phylogenetic clustering, actual and in silico RFLP analyses, phytoplasma strains associated with BBS disease in Quebec were identified as ‘Candidatus Phytoplasma asteris’‐related strains, closely related to the BBS Michigan phytoplasma strain (16SrI‐E). The secY gene sequence‐based single nucleotide polymorphism analysis revealed that one of the BBS phytoplasma strains associated with a leaf marginal yellowing is a secY‐I RFLP variant of the subgroup 16SrI‐E. Two viruses were detected in blueberry bushes. The Blueberry Red Ringspot Virus (BRRV) was found in a single infection in the cultivar Bluecrop with no apparent typical BRRV symptoms. The Tobacco Ringspot Virus (TRSV) was found singly infecting blueberry plants and co‐infecting a BBS phytoplasma‐infected blueberry cv. Bluecrop plant. This is the first report of TRSV in the cv. Bluecrop in Quebec. The Quebec BBS phytoplasma strain was identified in the leafhopper Graphocephala fennahi, which suggests that G. fennahi may be a potential vector for the BBS phytoplasma. The BBS disease shows a complex aetiology and epidemiology; therefore, prompt actions must be developed to support focused BBS integrated management strategies.     

Chironomid assemblages from seabird-affected High Arctic ponds

Seabirds can shunt nutrients and contaminants from marine to terrestrial ecosystems by forming dense breeding colonies and releasing wastes to these sites. A large colony of seabirds at Cape Vera (Devon Island, High Arctic Canada) has resulted in eutrophic conditions and potentially toxic concentrations of sedimentary metals in several freshwater ponds that drain their nesting sites. Here, we investigated the effects of elevated nutrient and sedimentary metal concentrations on the distribution of subfossil chironomids in surface sediments from 21 ponds that span a gradient of seabird influence. Although many ponds registered high nutrient concentrations (e.g., mean TP = 45 μg l ⁻¹), eutrophic taxa typical of temperate waters were not common, with most assemblages being dominated by morphotypes of Psectrocladius and Tanytarsina, as well as Corynoneura arctica-type, and Metriocnemus hygropetricus-type. Although the ponds within and outside the area influenced by seabirds contained largely similar taxa, variations did exist in the relative abundances of the different species. Lakewater pH was the only measured environmental variable that explained statistically significant amounts of variation in the chironomid assemblages. Although direct effects of pH on chironomids cannot be ruled out, pH is likely tracking production-related changes driven by limnetic dissolved inorganic carbon dynamics. Sediment cores collected from seabird-affected and seabird-free ponds showed a greater number of chironomid taxa and higher head capsule abundances in the pond receiving seabird inputs. Chironomid assemblages in both cores recorded increased abundances in recent decades, likely in response to warmer conditions and lengthened growing seasons.     

PERIPHYTIC DIATOM ASSEMBLAGES FROM ULTRA‐OLIGOTROPHIC AND UV TRANSPARENT LAKES AND PONDS ON VICTORIA ISLAND AND COMPARISONS WITH OTHER DIATOM SURVEYS IN THE CANADIAN ARCTIC1

Periphytic diatoms are potentially powerful indicators of environmental change in climatically‐sensitive high latitude regions. However, only a few studies have examined their taxonomic and ecological characteristics. We identified and enumerated diatom assemblages from sediment, rock, and moss habitats in 34 ultra‐oligotrophic and highly transparent lakes and ponds on Victoria Island, Arctic Canada. The similar limnological characteristics of the sites allowed us to examine the influence of habitat, independent of water chemistry, on the diatom assemblages. As is typical in shallow arctic water bodies, benthic taxa, including species of Achnanthes, Caloneis, Cymbella, Navicula, and Nitzschia, were most widely represented. Minor gradients in our measured environmental variables did not significantly explain any variance in diatom species, but there were marked differences in diatom assemblages among sites. Pond ephemerality seems to explain some diatom variation, because aerophilic taxa such as Achnanthes kryophila Petersen and A. marginulata Grunow were dominant in shallow sites that had undergone appreciable reductions in volume. We identified several taxa that exhibited strong habitat preferences to sediment, moss, or rock substrates and also found significant differences (P < 0.01) in diatom composition among the three habitats. In comparisons with three similar diatom surveys extending over 1200 km of latitude, we determined that surface sediment assemblages differed significantly (P < 0.001) among all regions examined. Diatom species diversity was inversely related to latitude, a result likely explained by differences in the lengths of growing seasons. These data contribute important ecological information on diatom assemblages in arctic regions and will aid in the interpretation of environmental changes in biomonitoring and paleolimnological studies.     

Long‐term limnological changes in the Ecuadorian páramo: Comparing the ecological responses to climate warming of shallow waterbodies versus deep lakes

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Determining diatom ecotones and their relationship to terrestrial ecoregion designations in the central Canadian Arctic Islands

Ecotones are key areas for the detection of global change because many are predicted to move with shifts in climate. Prince of Wales Island, in the Canadian Arctic Archipelago, spans the transition between mid‐ to high‐Arctic ecoregions. We analyzed limnological variables and recent diatom assemblages from its lakes and ponds to determine if assemblages reflected this ecotone. Limnological gradients were short, and water chemistry explained 20.0% of diatom variance in a redundancy analysis (RDA), driven primarily by dissolved organic carbon, Ca and SO₄. Most taxa were small, benthic forms; key taxa such as planktonic Cyclotella species were restricted to the warmer, southern portion of the study area, while benthic Staurosirella were associated with larger, ice‐dominated lakes. Nonetheless, there were no significant changes in diatom assemblages across the mid‐ to high‐Arctic ecoregion boundary. We combined our data set with one from nearby Cornwallis Island to expand the study area and lengthen its environmental gradients. Within this expanded data set, 40.6% of the diatom variance was explained by a combination of water chemistry and geographic variables, and significant relationships were revealed between diatom distributions and key limnological variables, including pH, specific conductivity, and chl‐a. Using principal coordinates analysis, we estimated community turnover with latitude and applied piecewise linear regression to determine diatom ecotone positions. A pronounced transition was present between Prince of Wales Island and the colder, more northerly Cornwallis Island. These data will be important in detecting any future northward ecotone movement in response to predicted Arctic climate warming in this highly sensitive region.     

Categorizing the influences of two large seabird colonies on island freshwater ecosystems in the Northwest Atlantic Ocean

Hydrobiologia - Seabird colonies influence ecosystems by releasing high concentrations of nutrients, metals, and contaminants via their wastes. Here, we examined seven lentic waterbodies impacted...     

B-cell subsets in the joint compartments of seropositive and seronegative rheumatoid arthritis (RA) and No-RA arthritides express memory markers and ZAP70 and characterize the aggregate pattern irrespectively of the autoantibody status

The aim of the present study was to determine whether different subsets of B cells characterize synovial fluid (SF) or synovial tissue (ST) of seropositive or seronegative rheumatoid arthritis (RA) with respect to the peripheral blood (PB). PB, SF and ST of 14 autoantibody (AB)-positive (rheumatoid factor [RF]-IgM, RF-IgA, anti-citrullinated peptide [CCP]), 13 negative RA and 13 no-RA chronic arthritides were examined for B-cell subsets (Bm1-Bm5 and IgD-CD27 classifications), zeta-associated protein kinase-70 (ZAP70) expression on B cells and cytokine levels (interleukin [IL]-1β, tumor necrosis factor [TNF]-α, IL-6, IL-8 and monocyte chemotactic protein [MCP]-1). Synovial tissues were classified as aggregate and diffuse patterns. No differences were found in B-cell percentages or in subsets in PB and SF between AB(+) and AB(-) RA and no-RA. In both AB(+) and AB(-) RA (and no-RA), the percentage of CD19(+)/ZAP70(+) was higher in SF than in PB (AB(+): P = 0.03; AB(-): P = 0.01; no-RA: P = 0.01). Moreover, SF of both AB(+) and AB(-) RA (and no-RA) patients was characterized by a higher percentage of IgD-CD27(+) and IgD-CD27(-) B cells and lower percentage of IgD(+)CD27(-) (P < 0.05) B cells compared to PB. In SF, ZAP70 positivity is more represented in B cell CD27(+)/IgD(-)/CD38(-). The aggregate synovitis pattern was characterized by higher percentages of Bm5 cells in SF compared with the diffuse pattern (P = 0.05). These data suggest that no difference exists between AB(+) and AB(-) in B-cell subset compartmentalization. CD27(+)/IgD(-)/ZAP70(+) memory B cells accumulate preferentially in the joints of RA, suggesting a dynamic maturation of the B cells in this compartment.