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

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

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

Biotransport of Algal Toxins to Riparian Food Webs

The occurrence of harmful algal blooms has resulted in growing worldwide concern about threats to aquatic life and human health. Microcystin (MC), a cyanotoxin, is the most widely reported algal toxin in freshwaters. Prior studies have documented its presence in aquatic food webs including commercially important fish and shellfish. In this paper we present the first evidence that algal toxins propagate into riparian food webs. We show that MC is present in emerging aquatic insects (Hexagenia mayflies) from the James River Estuary and their consumers (Tetragnathidae spiders and Prothonotary Warblers, Protonotaria citrea). MC levels in Prothonotary Warblers varied by age class, with nestlings having the highest levels. At the site where nestlings received a higher proportion of aquatic prey (i.e., mayflies) in their diet, we observed higher MC concentrations in liver tissue and fecal matter. Warbler body condition and growth rate were not related to liver MC levels, suggesting that aquatic prey may provide dietary benefits that offset potential deleterious effects of the toxin. This study provides evidence that threats posed by algal toxins extend beyond the aquatic environments in which blooms occur

McGarvey_EtAl_RawData

These are raw data files (.csv) for the 15 freshwater fishes modeled in "On the use of climate covariates in aquatic species distribution models: are we at risk of throwing the baby out?" (McGarvey et al.). The files are formatted for MaxEnt ('species with data' format) and include MaxEnt batch files that can be used to re-run the models

Better Together: 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 developmen

Ghrelin receptor expression and colocalization with anterior pituitary hormones using a GHSR-GFP mouse line

Ghrelin is the endogenous ligand for the GH secretagogue receptor (GHSR) and robustly stimulates GH release from the anterior pituitary gland. Ghrelin also regulates the secretion of anterior pituitary hormones including TSH, LH, prolactin (PRL), and ACTH. However, the relative contribution of a direct action at the GHSR in the anterior pituitary gland vs. an indirect action at the GHSR in the hypothalamus remains undefined. We used a novel GHSR-enhanced green fluorescent protein (eGFP) reporter mouse to quantify GHSR coexpression with GH, TSH, LH, PRL, and ACTH anterior pituitary cells in males vs. females and in chow-fed or calorie-restricted (CR) mice. GHSR-eGFP-expressing cells were only observed in anterior pituitary. The number of GHSR-eGFP-expressing cells was higher in male compared with females, and CR did not affect the GHSR-eGFP cell number. Double staining revealed 77% of somatotrophs expressed GHSR-eGFP in both males and females. Nineteen percent and 12.6% of corticotrophs, 21% and 9% of lactotrophs, 18% and 19% of gonadotrophs, and 3% and 9% of males and females, respectively, expressed GHSR-eGFP. CR increased the number of TSH cells, but suppressed the number of lactotrophs and gonadotrophs, expressing GHSR-eGFP compared with controls. These studies support a robust stimulatory action of ghrelin via the GHSR on GH secretion and identify a previously unknown sexual dimorphism in the GHSR expression in the anterior pituitary. CR affects GHSR-eGFP expression on lactotrophs, gonadotrophs, and thyrotrophs, which may mediate reproductive function and energy metabolism during periods of negative energy balance. The low to moderate expression of GHSR-eGFP suggests that ghrelin plays a minor direct role on remaining anterior pituitary cells