Effects of invasive watermilfoil on primary production in littoral ones of north-temperate lakes

Species invasions are changing aquatic ecosystems worldwide. Submerged aquatic macrophytes control lake ecosystem processes through their direct and indirect interactions with other primary producers, but how these interactions may be altered by macrophyte species invasions in temperate lakes is poorly understood. We addressed whether invasive watermilfoil (IWM) altered standing crops and gross primary production (GPP) of other littoral primary producers (macrophytes, phytoplankton, attached algae, and periphyton) in littoral zones of six Michigan lakes through a paired-plot comparison study of sites with IWM (standardized abundance 7–56%) compared to those with little or no IWM (standardized abundance 0–2%). We found that primary producer standing crops and the GPP of epiphytes, phytoplankton, and benthic periphyton were variable among lakes and not significantly different between paired study plots. Macrophyte standing crops predicted rates of benthic periphyton GPP, and standing crops of all other primary producers across all study plots. Overall, our results suggest that the effects of IWM on other primary producers in littoral zones may be lake-specific, and are likely dependent on the density of IWM, or whether it is functionally similar to other native species that it replaces or co-exists with. Moreover, in lakes where IWM is established but does not dominate macrophyte assemblages, the effects on littoral zone productivity may be minimal. Instead, overall macrophyte biomass is the primary factor controlling the rates of production and biomass of the other littoral zone primary producers, as has long been understood and observed in lake ecosystems

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2–4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Associations between large wood and streambed complexity in headwater streams in the western Upper Peninsula, Michigan

Habitat complexity is an important feature of fluvial ecosystems, and in forested streams large wood can indirectly and directly contribute to complexity that supports biota. In this study of six forested streams of Michigan\u27s western Upper Peninsula we quantified large instream wood and streambed morphology analyzed as variograms to describe the complexity of the streambed. Our goal was to determine the extent to which the streambed complexity could be explained by the volume and number of instream large wood objects. Based on previous studies in other systems, we expected a positive relationship between large wood volume and streambed complexity within the channel. Across the study sites, large wood volumes (standardized by area) ranged from approximately 0.0036 m3 m−2 to 0.029 m3 m−2 and the sites aligned into three groups based on overall complexity in channel morphology as derived from variograms. However, variation in streambed complexity was not clearly associated with the volume of large wood present in the channels. In contrast to our hypothesis, the two sites with the highest substrate complexity did not also have the greatest wood volume. Complexity was inversely related to large wood abundance and the relationship between standardized wood volume and complexity also appeared to follow this trend. Our findings may be a result of the low stream power that likely occurs in these streams, as well as because wood in the study streams was generally smaller and in lower abundance than typically reported for other streams and rivers. We suspect that the smaller diameter wood measured in these actively managed forests of northern Michigan would have shorter lifespans (i.e., degrade more quickly) and weaker hydrological influence, and thus a less significant influence on streambed complexity

Migrations and biological characteristics of adfluvial coaster brook trout in a south shore Lake Superior tributary

We used fish traps and electrofishing surveys to characterize the biology, life history traits, and potential biotic interactors important to the rehabilitation of native, adfluvial coaster brook trout Salvelinus fontinalis in Lake Superior. This study focused on the Salmon Trout River, Michigan, which is the site of the last known remnant population of adfluvial brook trout on the south shore of Lake Superior. The brook trout captured in passive traps (weirs) in the river ranged from 56 to 554 mm in total length (TL) and from 0 (young of the year) to 6 years of age. This population displayed a protracted 5-month migration into the river but one that included relatively few fish. Coaster brook trout in this population appear to initiate adfluvial migrations near age 3 and 300 mm TL. Relative weight values increased with fish length and therefore reproductive life stage, possibly indicating the shift from river to lake habitats. This population of coaster brook trout is small and subject to potential biotic interactions with exotic species and population limitation because of an active fishery in the lake and river. Migratory runs of brook trout coincided with large runs of coho salmon Oncorhynchus kisutch, and the instream juvenile salmonid composition included proportionately high densities of coho salmon and rainbow trout O. mykiss. In addition, Floy tag return data indicated that exploitation of reproductive-age Salmon Trout River coaster brook trout was at least 12% and may have been as high as 50% in the open waters of Lake Superior. A recent increase in the legal minimum length limit and reduction of the daily bag limit for recreational harvest may slow or reverse this trend. © Copyright by the American Fisheries Society 2008

Evaluation of suitability and comparability of stream assessment indices using macroinvertebrate data sets from the Northern Lakes and Forests Ecoregion

Researchers and managers within the Upper Midwest currently use a variety of sampling methodologies and biological indices to assess ecological condition of stream systems. With multiple entities collecting bioassessment data it is important that we determine the comparability of data and the indices derived from these data for effective assessment of natural systems. In this study we assessed the similarity of data collected by different agencies and we focused on data from one watershed to examine the outputs of different indices for stream assessment, and the temporal variation of index score within sites. We compared duplicate macroinvertebrate community data collected by the Little River Band of Ottawa Indians and the Michigan Department of Environmental Quality for overall community composition and index scores derived from these data. Duplicate samples were similar in composition index scores. Taxonomic resolution was addressed and indicated that genus level resolution gives a more favorable score when using indices. We also evaluated the utility of currently available macroinvertebrate indices of biotic integrity to assess data from the Big Manistee River watershed. The indices evaluated were the Hilsenhoff biotic index, the benthic community index for the Northern Lakes and Forests (NLFBCI), the Great Lakes Environmental Assessment Survey (GLEAS) procedure 51 for macroinvertebrates and a biological condition gradient model for the Upper Midwest. Outputs from the indices were moderately correlated (Spearman rank order correlation, r = 0.35-0.698) though they indicated different assessments of overall site integrity. Compared with larger scale regional indices, locally calibrated indices generally classified sites as having better biological condition. Replicate samples collected within sites indicated the GLEAS had higher levels of variability (0-265%CV) within sites than the other indices ( \u3c 10%CV). Data from long-term (10 year) monitoring stations were used to evaluate seasonal and long-term index performance. There were differences in index score classifications from spring and fall samples indicating that standardization of sampling time is necessary for comparative analysis. Temporal trends over 10 years reveal natural variation and set the baseline for evaluating the influence of anthropogenic effects. Overall, results indicate that choice of index can alter assessment of site condition. For bioassessment in the Big Manistee River watershed the NLFBCI performs well and accurately reflects site condition. © 2014 Elsevier Ltd. All rights reserved

Sand aggradation alters biofilm standing crop and metabolism in a low-gradient Lake Superior tributary

Sediment deposition changes the physical characteristics of river beds, and may alter the production and/or processing of allochthonous and autochthonous organic matter, with potential consequences for stream food webs. We conducted a comparative study of biofilm standing crop and metabolism in the Salmon Trout River, a tributary of Lake Superior where watershed disturbances have led to 3-fold increases in streambed fine sediments, predominately sand, in the past decade. We compared biofilm standing crop and metabolism rates using light–dark chambers in reaches where substrate consisted of predominately exposed rock or sand substrates. Biofilm chlorophyll a was 4.2-fold greater on rock substrates, but ash-free dry mass was 8-fold greater on sand substrates. Rates of gross primary production were 2 to 25-fold greater on rock versus sand substrates, and differences persisted whether rates were scaled for area or biofilm standing crop. In contrast, rates of respiration were similar on rock and sand substrates when scaled per unit area but 7–13 times lower on sand when scaled for biofilm standing crop. Together, these results suggest that sand aggradation in this river alters organic matter processing during the summer from net production to net consumption and storage of organic matter. Sand aggradation may alter the availability and processing of both allochthonous and autochthonous food resources in this forested river, with potential far-reaching impacts on the food web