A comparison of computational methods for estimating estuarine production and respiration from diel open water dissolved oxygen measurements

Diel dissolved oxygen (DO) data were used to characterize seasonal, inter-annual, and longitudinal variation in production and respiration for the James River Estuary. Two computational methods (Bayesian and bookkeeping) were applied to these data to determine whether inferences regarding DO metabolism are sensitive to methodology. Net metabolism was sensitive to methodology as Bayesian results indicated net heterotrophy (production \u3c respiration) while bookkeeping results indicated net autotrophy (production \u3e respiration). Differences in net metabolism among the methods was due to low seasonal variation in respiration using the Bayesian method, whereas bookkeeping results showed a strong correlation between production and respiration. Bayesian results suggest a dependence on allochthonous organic matter (OM) whereas bookkeeping results suggest that metabolism is dependent on autochthonous OM. This study highlights the importance in considering the method used to derive metabolic estimates as it can impact the assessment of trophic status and sources of OM supporting an estuary

Effects of dissolved and dietary Microcystin on clearance rates of Wedge Clams (Rangia cuneata) in the tidal fresh James River

Benthic filter feeders are important organisms in estuaries due to their ability to remove algal and non-algal particulate matter from the water column. Microcystin (MC) is a cyanotoxin that is known to have adverse effects on diverse consumers, though its effects on benthic filter-feeders are not well-studied. In this study, we examine the effects of microcystin on the filtering activities of Rangia cuneata, a common and often dominant filter-feeder in tidal freshwaters. Clams and seston obtained from the James River were used along with commercially-available microcystin to measure clearance rates of Rangia across a gradient of dissolved microcystin concentrations. We also compared clearance rates of James River clams to natural food sources in the presence and absence of microcystin. Our results show that dissolved microcystin inhibited Rangia clearance rates. Even at the lowest concentration tested (0.40 μg MC L-1) clearance rates were significantly lower than controls. Dietary experiments showed that when elevated microcystin was present in the James (September), clearance rates were lower for clams fed James River seston relative to clams fed seston from another source. Our results suggest that the presence of microcystin may diminish ecosystem service provided by benthic filter feeders.https://scholarscompass.vcu.edu/uresposters/1038/thumbnail.jp

Algal toxins in the food chain – a comparative study of Chesapeake Bay and Baltic coastal food webs

Microcystin (MC) is a hepatotoxin produced by cyanobacteria (blue-green algae) which is found globally in eutrophic waters including lakes, lagoons and estuaries (Paerl and Paul 2012). The presence of MC in food webs is of concern due to adverse effects on biota and exposure to humans via commercial and recreational fisheries (Paerl and Otten 2013). Little is known regarding the factors which determine MC accumulation in food webs. We hypothesized that dietary exposure would be determined in part by sources of organic matter supporting the food web. We undertook a comparative study of the James River Estuary, a sub-estuary of Chesapeake Bay, and the Curonian Lagoon, a sub-estuary of the Baltic Sea and largest coastal lagoon in Europe. Both sites experience cyanobacteria blooms known to produce MC (Wood et al. 2014; Lesutienė et al. 2014), but differ in their sources of organic matter. The James receives large inputs of terrestrial organic matter due to the draining of a mountainous catchment. The Curonian Lagoon is fed by a lowland river which delivers low concentrations of terrestrial organic matter. We hypothesized that high internal production in the lagoon, coupled with lower dilution by terrestrial organic matter inputs, would results in greater exposure to MC among biota of the Curonian Lagoon

Early Career Aquatic Scientists Forge New Connections at Eco-DAS XV

A sense of kuleana (personal responsibility) in caring for the land and sea. An appreciation for laulima (many hands cooperating). An understanding of aloha ’āina (love of the land). The University of Hawai’i at Manoa hosted the 2023 Ecological Dissertations in Aquatic Sciences (Eco-DAS) program, which fostered each of these intentions by bringing together a team of early career aquatic ecologists for a week of networking and collaborative, interdisciplinary project development (Fig. 1)

Targeted treatments for fragile X syndrome

Fragile X syndrome (FXS) is the most common identifiable genetic cause of intellectual disability and autistic spectrum disorders (ASD), with up to 50% of males and some females with FXS meeting criteria for ASD. Autistic features are present in a very high percent of individuals with FXS, even those who do not meet full criteria for ASD. Recent major advances have been made in the understanding of the neurobiology and functions of FMRP, the FMR1 (fragile X mental retardation 1) gene product, which is absent or reduced in FXS, largely based on work in the fmr1 knockout mouse model. FXS has emerged as a disorder of synaptic plasticity associated with abnormalities of long-term depression and long-term potentiation and immature dendritic spine architecture, related to the dysregulation of dendritic translation typically activated by group I mGluR and other receptors. This work has led to efforts to develop treatments for FXS with neuroactive molecules targeted to the dysregulated translational pathway. These agents have been shown to rescue molecular, spine, and behavioral phenotypes in the FXS mouse model at multiple stages of development. Clinical trials are underway to translate findings in animal models of FXS to humans, raising complex issues about trial design and outcome measures to assess cognitive change that might be associated with treatment. Genes known to be causes of ASD interact with the translational pathway defective in FXS, and it has been hypothesized that there will be substantial overlap in molecular pathways and mechanisms of synaptic dysfunction between FXS and ASD. Therefore, targeted treatments developed for FXS may also target subgroups of ASD, and clinical trials in FXS may serve as a model for the development of clinical trial strategies for ASD and other cognitive disorders

Ghrelin

This work was supported by grants from the NIH (DP2DK105570-01 and 2P30DK046200 to MLA, DK21397 to HJG, K01DK098319 to KMH, K01MH091222 to LH, DK093848 to RJS, R01DK082590 to LS, R01DK097550 to JT, RO1 DK 076037 to MOT, R01DA024680 and R01MH085298 to JMZ, R01AG019230 and R01AG029740 to RGS) The Wellcome Trust (MK), Science Foundation Ireland (12/YI/B2480 to CWL), the Alexander von Humboldt Foundation (MHT), the Deutsches Zentrum für Diabetesforschung (MHT), the Helmholtz Alliance ICEMED e Imaging and Curing Environmental Metabolic Diseases, through the Initiative and Networking Fund of the Helmholtz Association (MHT), and the Helmholtz cross-program topic “Metabolic Dysfunction” (MHT). Allan Geliebter was sponsored by NIH grants R01DK80153; R01DK074046; R03DK068603; P30DK26687

Increased Frequency of Sediment Heatwaves in a Virginia Seagrass Meadow

Coastal marine heatwaves have destructive and lasting impacts on foundational species and are increasing in frequency, duration, and magnitude. High atmospheric temperatures are often associated with marine heatwaves (MHW) which are defined as 5 days of water temperatures above a seasonally varying 90th percentile threshold. In this study, we consider the prevalence of MHW propagation into surficial sediments to cause sediment heatwaves (SHW). Within a shallow, subtidal seagrass meadow in Virginia, USA, sediment temperature was measured at hourly intervals at a depth of 5 cm between June 2020 and October 2022 at the meadow edge and central meadow interior. The observed sediment temperature along with a 29-year record of water temperature and water level was used to develop a sediment temperature model for each location. Modeled sediment temperatures were used to identify sediment heatwaves that may thermally stress belowground seagrass. At both meadow locations, sediment heatwave frequency increased at a rate twice that of MHWs in the average global open ocean, coinciding with a 172% increase in the annual number of SHW days, from 11 to 30 days year−1 between 1994 and 2022. Sediment heatwaves at both meadow locations co-occurred with a MHW 79–81% of the time, with nearly all SHWs having a zero day lag. The top 10% most extreme MHWs and SHWs occurred between November and April when thermal stress to seagrass was unlikely. In June 2015, a SHW co-occurred with an anomalously long duration MHW that was associated with a 90% decline in seagrass from this system, suggesting that SHWs may have contributed to the observed seagrass loss. These results document heatwave propagation across the pelagic-sediment interface which likely occur broadly in shallow systems with impacts to critical coastal ecosystem processes and species dynamics

CGG-repeat length and neuropathological and molecular correlates in a mouse model for fragile X-associated tremor/ataxia syndrome

The 5′untranslated region (UTR) of the FMR1 gene contains a CGG-repeat, which may become unstable upon transmission to the next generation. When repeat length exceeds 200, the FMR1 gene generally undergoes methylation-mediated transcriptional silencing. The subsequent absence of the gene product Fragile X Mental Retardation Protein (FMRP)causes the mental retardation seen in fragile X patients. A CGG-repeat length between 55 and 200 trinucleotides has been termed the premutation (PM). Predominantly elderly male PM carriers are at risk of developing a progressive neurodegenerative disorder: fragile X-associated tremor/ataxia syndrome (FXTAS). All PM carriers have elevated FMR1 mRNA levels, in spite of slightly decreased FMRP levels. The presence of intranuclear ubiquitin-positive inclusions in many brain regions is a neuropathological hallmark of FXTAS. Studies in humans attempting to correlate neuropathological outcomes with molecular measures are difficult because of the limited availability of tissue. Therefore, we have used the expanded CGG-repeat knock-in mouse model of FXTAS to examine the relationship between the molecular and neuropathological parameters in brain. We present Fmr1 mRNA and Fmrp levels and the presence of intranucl

Data from: On the use of climate covariates in aquatic species distribution models: are we at risk of throwing the baby out?

Species distribution models (SDMs) in river ecosystems can incorporate climate information by using air temperature and precipitation as surrogate measures of instream conditions or by using independent models of water temperature and hydrology to link climate to instream habitat. The latter approach is preferable but constrained by the logistical burden of developing water temperature and hydrology models. We therefore assessed whether regional scale, freshwater SDM predictions are fundamentally different when climate data versus instream temperature and hydrology are used as covariates. Maximum Entropy (MaxEnt) SDMs were built for 15 freshwater fishes using one of two covariate sets: (1) air temperature and precipitation (climate variables) in combination with physical habitat variables; or (2) water temperature, hydrology (instream variables) and physical habitat. Three procedures were then used to compare results from climate vs. instream models. First, equivalence tests assessed average pairwise differences (site-specific comparisons throughout each species’ range) among climate and instream models. Second, ‘congruence’ tests determined how often the same stream segments were assigned high habitat suitability by climate and instream models. Third, Schoener’s D and Warren’s I niche overlap statistics quantified range-wide similarity in predicted habitat suitability values from climate vs. instream models. Equivalence tests revealed small, pairwise differences in habitat suitability between climate and instream models (mean pairwise differences in MaxEnt raw scores for all species -4). Congruence tests showed a strong tendency for climate and instream models to predict high habitat suitability at the same stream segments (median congruence = 68%). D and I statistics reflected a high margin of overlap among climate and instream models (median D = 0.78, median I = 0.96). Overall, we found little support for the hypothesis that SDM predictions are fundamentally different when climate versus instream covariates are used to model fish species’ distributions at the scale of the Columbia Basin

Increasing heatwave frequency in streams and rivers of the United States

Abstract Heatwaves are increasing in frequency, duration, and intensity in ocean, coastal, and lake ecosystems. While positive water temperature trends have been documented in many rivers, heatwaves have not been analyzed. This study examined heatwaves in rivers throughout the United States between 1996 and 2021. Riverine heatwaves increased in frequency over the study period, with the most robust increases occurring in summer and fall, in mid‐ to high‐order streams, and at free‐flowing sites and sites above a reservoir. The increase in heatwave frequency was accompanied by an increase in moderate strength heatwaves as well as a doubling of the annual mean total number of heatwave days at a site. Riverine heatwaves were often associated with normal or below‐normal discharge conditions and at sites with a mean annual discharge ≤ 250 m3 s−1. These results provide the first assessment of heatwaves in rivers for a large geographic area in the United States