58 research outputs found
How are coastal benthos fed?
Water movement can influence the distribution of benthos, in part, by increasing food delivery; however, the impact of advective transport and turbulent diffusion on organic matter flux to nearshore benthic communities is not well quantified. In this study, we measured the vertical particulate organic carbon (POC) and particulate phosphorus (PP) flux in nearshore Lake Michigan using two naturally occurring daughter/parent radionuclide pairs (234Th/238U and 90Y/90Sr) and compared these fluxes to coincident benthic chamber estimates of respiration and total phosphorus efflux by quagga mussels on the lakebed. We found that advective onshore transport and vertical convective mixing increased POC and PP flux to the nearshore benthos by a factor of ~15 and ~30 over offshore trap-derived estimates of flux. From these results, we hypothesize that high benthos population densities are related to an edge effect created when the dominant mechanism of particle delivery transitions from gravitational settling to convection
Nitrogen cycling rates and light effects in tropical Lake Maracaibo, Venezuela
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109860/1/lno19984381814.pd
The potential for CO \u3c inf\u3e 2 -induced acidification in freshwater: A great lakes case study
Ocean acidification will likely result in a drop of 0.3–0.4 pH units in the surface ocean by 2100, assuming anthropogenic CO2 emissions continue at the current rate. Impacts of increasing atmospheric pCO2 on pH in freshwater systems have scarcely been addressed. In this study, the Laurentian Great Lakes are used as a case study for the potential for CO2-induced acidification in freshwater systems as well as for assessment of the ability of current water quality monitoring to detect pH trends. If increasing atmospheric pCO2 is the only forcing, pH will decline in the Laurentian Great Lakes at the same rate and magnitude as the surface ocean through 2100. High-resolution numerical models and one high-resolution time series of data illustrate that the pH of the Great Lakes has significant spatio-temporal variability. Because of this variability, data from existing monitoring systems are insufficient to accurately resolve annual mean trends. Significant measurement uncertainty also impedes the ability to assess trends. To elucidate the effects of increasing atmospheric CO2 in the Great Lakes requires pH monitoring by collecting more accurate measurements with greater spatial and temporal coverage
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Frost and leaf-size gradients in forests: global patterns and experimental evidence
Explanations of leaf size variation commonly focus on water availability, yet leaf size also varies with latitude and elevation in environments where water is not strongly limiting. We provide the first conclusive test of a prediction of leaf energy balance theory that may explain this pattern: large leaves are more vulnerable to night-time chilling, because their thick boundary layers impede convective exchange with the surrounding air.
Seedlings of New Zealand evergreens spanning 12-fold variation in leaf width were exposed to clear night skies, and leaf temperatures measured with thermocouples. We then used a global dataset to assess several climate variables as predictors of leaf size in forest assemblages.
Leaf-minus-air temperature was strongly correlated with leaf width, ranging from -0.9 to -3.2 C in the smallest- and largest-leaved species, respectively. MAT and frost-free period were good predictors of evergreen angiosperm leaf size in forest assemblages, but no climate variable predicted deciduous leaf size.
Although winter deciduousness makes large leaves possible in strongly seasonal climates, large-leaved evergreens are largely confined to frost-free climates because of their susceptibility to radiative cooling. Evergreen leaf size data can therefore be used to enhance vegetation models, and to infer palaeotemperatures from fossil leaf assemblages
The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance
INTRODUCTION
Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic.
RATIONALE
We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs).
RESULTS
Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants.
CONCLUSION
Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century
Food partitioning among Lake Malawi nearshore fishes as revealed by stable isotope analyses
Continuous CO2 data collected in 2017 from a Lake Michigan transect between Milwaukee, WI and Muskegon MI.
Dataset: CO2Continuous CO2 data collected in 2017 from a Lake Michigan transect between Milwaukee, WI and Muskegon MI.
For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/737667NSF Division of Ocean Sciences (NSF OCE) OCE-1658390, Great Lakes Observing System (GLOS) NA16NOS012002
Lake Michigan water chemistry data, including dissolved and particulate phosphorus, chlorophyll a, carbon dioxide, total dissolved inorganic carbon, and dissolved organic carbon.
Dataset: Lake Michigan ChemistryLake Michigan water chemistry data, including dissolved and particulate phosphorus, chlorophyll a, carbon dioxide, total dissolved inorganic carbon, and dissolved organic carbon.
For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/737176NSF Division of Ocean Sciences (NSF OCE) OCE-165839
Depth profiles of temperature, conductivity, dissolved oxygen, pH, chlorophyll fluorescence, etc., collected with a SeaBird SBE 25plus CTD in Lake Michigan during 2017
Dataset: CTDDepth profiles of temperature, conductivity, dissolved oxygen, pH, chlorophyll fluorescence, etc., collected with a SeaBird SBE 25plus CTD in Lake Michigan during 2017.
For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/737534NSF Division of Ocean Sciences (NSF OCE) OCE-165839
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