Sensitive Life Stages Research Articles

Coral larvae increase nitrogen assimilation to stabilize algal symbiosis and combat bleaching under increased temperature.

Rising sea surface temperatures are increasingly causing breakdown in the nutritional relationship between corals and algal endosymbionts (Symbiodiniaceae), threatening the basis of coral reef ecosystems and highlighting the critical role of coral reproduction in reef maintenance. The effects of thermal stress on metabolic exchange (i.e., transfer of fixed carbon photosynthates from symbiont to host) during sensitive early life stages, however, remains understudied. We exposed symbiotic Montipora capitata coral larvae in Hawai'i to high temperature (+2.5°C for 3 days), assessed rates of photosynthesis and respiration, and used stable isotope tracing (4 mM 13C sodium bicarbonate; 4.5 h) to quantify metabolite exchange. While larvae did not show any signs of bleaching and did not experience declines in survival and settlement, metabolic depression was significant under high temperature, indicated by a 19% reduction in respiration rates, but with no change in photosynthesis. Larvae exposed to high temperature showed evidence for maintained translocation of a major photosynthate, glucose, from the symbiont, but there was reduced metabolism of glucose through central carbon metabolism (i.e., glycolysis). The larval host invested in nitrogen cycling by increasing ammonium assimilation, urea metabolism, and sequestration of nitrogen into dipeptides, a mechanism that may support the maintenance of glucose translocation under thermal stress. Host nitrogen assimilation via dipeptide synthesis appears to be used for nitrogen limitation to the Symbiodiniaceae, and we hypothesize that nitrogen limitation contributes to retention of fixed carbon by favoring photosynthate translocation to the host. Collectively, our findings indicate that although these larvae are susceptible to metabolic stress under high temperature, diverting energy to nitrogen assimilation to maintain symbiont population density, photosynthesis, and carbon translocation may allow larvae to avoid bleaching and highlights potential life stage specific metabolic responses to stress.

New insights into a sensitive life stage: hydraulics of tree seedlings in their first growing season.

The first year in a tree's life is characterized by distinct morphological changes, requiring constant adjustments of the hydraulic system. Despite their importance for the natural regeneration of forests and future vegetation composition, little has been known about the hydraulics of tree seedlings. At different times across the first growing season, we analysed xylem area-specific (Kshoot_Axyl) and leaf area-specific (Kshoot_L) shoot hydraulic conductance, as well as embolism resistance of three temperate conifer trees, two angiosperm trees and one angiosperm shrub, and related findings to cell osmotic parameters and xylem anatomical traits. Over the first 10 wk after germination, Kshoot_Axyl and Kshoot_L sharply decreased, then remained stable until the end of the growing season. Embolism resistance was remarkably low in the youngest stages but, coupled with an increase in cell wall reinforcement, significantly increased towards autumn. Contemporaneously, water potential at turgor loss and osmotic potential at saturation decreased. Independent of lineage, species and growth form, the transition from primary to secondary xylem resulted in a less efficient but increasingly more embolism-resistant hydraulic system, enabling stable water supply under increasing risk for low water potentials.

Intraspecific variation in thermal performance curves for early development in Fundulus heteroclitus.

Thermal performance curves (TPCs) provide a framework for understanding the effects of temperature on ectotherm performance and fitness. TPCs are often used to test hypotheses regarding local adaptation to temperature or to develop predictions for how organisms will respond to climate warming. However, for aquatic organisms such as fishes, most TPCs have been estimated for adult life stages, and little is known about the shape of TPCs or the potential for thermal adaptation at sensitive embryonic life stages. To examine how latitudinal gradients shape TPCs at early life stages in fishes, we used two populations of Fundulus heteroclitus that have been shown to exhibit latitudinal variation along the thermal cline as adults. We exposed embryos from both northern and southern populations and their reciprocal crosses to eight different temperatures (15°C, 18°C, 21°C, 24°C, 27°C, 30°C, 33°C, and 36°C) until hatch and examined the effects of developmental temperature on embryonic and larval traits (shape of TPCs, heart rate, and body size). We found that the pure southern embryos had a right-shifted TPC (higher thermal optimum (Topt) for developmental rate, survival, and embryonic growth rate) whereas pure northern embryos had a vertically shifted TPC (higher maximum performance (Pmax) for developmental rate). Differences across larval traits and cross-type were also found, such that northern crosses hatched faster and hatched at a smaller size compared to the pure southern population. Overall, these observed differences in embryonic and larval traits are consistent with patterns of both local adaptation and countergradient variation.

Habitat persistency analysis with HEM‐PEAK: A novel approach for the assessment of hydropeaking impacts and mitigation measure design

AbstractHydropeaking is one of the most severe pressures of hydropower on aquatic ecosystems. The discharge fluctuations due to turbine operations cause frequent shifts in hydraulic habitat characteristics such as flow velocity and water depth. Those rapid changes on a daily or sub daily basis, however, are beyond the possibilities of evolutionary adaptations of aquatic organisms, especially for fish in their sensitive early life stages. Thus, one central aim in terms of the evaluation of hydropeaking impacts or the design of mitigation measures is the analysis or establishment of hydraulically stable habitat conditions. This study presents a novel habitat assessment tool to quantify hydraulically stable habitat conditions in the form of a persistency of suitable habitats in hydropeaking reaches. The HEM‐PEAK tool determines areas that contain equal ranges of depth‐averaged flow velocity and water depth for both base flow and peak flow in three categories. Those areas also exclude dewatering sites, which have to be seen as ‘residual risk for stranding’. In the present study, the model was used to evaluate the YOY habitats of brown trout and grayling. The model was tested for 14 hydropeaking reaches to evaluate the quantity of habitat persistency for different morphological characteristics, such as straight, winding, alternating gravel bars and bifurcation reaches. The findings reveal that there is no relationship between hydraulically stable habitat conditions with reach scale bed slope or the magnitude of dewatering areas. However, the changes in specific discharge in relation to bankfull width could be negatively related to the magnitude of hydraulically stable habitat conditions independent of the morphological type. This relationship is minor for summer scenarios compared to spring, as the initial habitat quality during the increased base flow conditions is already limiting the availability of suitable habitats which might have persistency during peak flow. In detail, several self‐forming bars like point bars and artificial structures like groins and coarse rip‐rap could be determined, which could be explicitly addressed in terms of mitigation measure design based on the application of the HEM‐PEAK tool.

Outbreeding reduces survival during metamorphosis in a headwater stream salamander.

Assessing direct fitness effects of individual genetic diversity is challenging due to the intensive and long-term data needed to quantify survival and reproduction in the wild. But resolving these effects is necessary to determine how inbreeding and outbreeding influence eco-evolutionary processes. We used 8 years of capture-recapture data and single nucleotide polymorphism genotypes for 1906 individuals to test for effects of individual heterozygosity on stage-specific survival probabilities in the salamander Gyrinophilus porphyriticus. The life cycle of G. porphyriticus includes an aquatic larval stage followed by metamorphosis into a semi-aquatic adult stage. In our study populations, the larval stage lasts 6-10 years, metamorphosis takes several months, and lifespan can reach 20 years. Previous studies showed that metamorphosis is a sensitive life stage, leading us to predict that fitness effects of individual heterozygosity would occur during metamorphosis. Consistent with this prediction, monthly probability of survival during metamorphosis declined with multi-locus heterozygosity (MLH), from 0.38 at the lowest MLH (0.10) to 0.06 at the highest MLH (0.38), a reduction of 84%. Body condition of larvae also declined significantly with increasing MLH. These relationships were consistent in the three study streams. With evidence of localised inbreeding within streams, these results suggest that outbreeding disrupts adaptations in pre-metamorphic and metamorphic individuals to environmental gradients along streams, adding to evidence that headwater streams are hotspots of microgeographic adaptation. Our results also underscore the importance of incorporating life history in analyses of the fitness effects of individual genetic diversity and suggest that metamorphosis and similar discrete life stage transitions may be critical periods of viability selection.

Global habitat predictions to inform spatiotemporal fisheries management: Initial steps within the framework

Tuna Regional Fishery Management Organizations (tRFMOs) are increasingly interested in spatiotemporal management as a tool to reduce interaction rates with vulnerable species. We use blue shark (Prionace glauca) as a case study to demonstrate the critical first steps in the implementation process, highlighting how predictions of global habitat for vulnerable life stages can be transformed into a publicly-accessible spatial bycatch mitigation tool. By providing examples of possible management goals and an associated threshold to identify essential habitats, we show how these key areas can represent a relatively low percentage of oceanic area on a monthly basis (16–24% between 50°S and 60°N), yet can have relatively high potential protection efficiency (∼ 42%) for vulnerable stages if fishing effort is redistributed elsewhere. While spatiotemporal management has demonstrable potential for blue sharks to effectively mitigate fishing mortality on sensitive life stages, we identify inherent challenges and sequential steps that require careful consideration by tRFMOs as work proceeds. We also discuss how our single-species framework could be easily extended to a multispecies approach by assigning relative conservation risk before layering habitat model predictions in an integrated analysis. Such broader application of our approach could address the goals of tRFMOs related to reducing the ecosystem effects of fishing and pave the way for efficient fisheries co-management using an ecosystem-based approach.

The development of an egg-soaking method for delivering dsRNAs into spider mites

Recently, the first sprayable RNAi biopesticide, Ledprona, against the Colorado potato beetle, Leptinotarsa decemlineata, has been registered at the United States Environmental Protection Agency. Spider mites (Acari: Tetranychidae), a group of destructive agricultural and horticultural pests, are notorious for rapid development of insecticide/acaricide resistance. The management options, on the other hand, are extremely limited. RNAi-based biopesticides offer a promising control alternative to address this emerging issue. In this study, we i) developed an egg-soaking dsRNA delivery method; ii) evaluated the factors influencing RNAi efficiency, and finally iii) investigated the potential mode of entry of this newly developed egg-soaking RNAi method. In comparison to other dsRNA delivery methods, egg-soaking method was the most efficient, convenient/practical, and cost-effective method for delivering dsRNAs into spider mites. RNAi efficiency of this RNAi method was affected by target genes, dsRNA concentration, developmental stages, and mite species. In general, the hawthorn spider mite, Amphitetranychus viennensis, is more sensitive to RNAi than the two-spotted spider mite, Tetranychus urticae, and both of them have dose-dependent RNAi effect. For different life stages, egg and larvae are the most sensitive life stages to dsRNAs. For different target genes, there is no apparent association between the suppression level and the resultant phenotype. Finally, we demonstrated that this egg-soaking RNAi method acts as both stomach and contact toxicity. Our combined results demonstrate the effectiveness of a topically applied dsRNA delivery method, and the potential of a spray induced gene silencing (SIGS) method as a control alternative for spider mites.

Perinatal interventions to prevent Adverse Childhood Experiences (ACEs): A scoping review.

Preventing Adverse Childhood Experiences (ACEs) is a public health priority, and the perinatal period is a sensitive life stage when preventive interventions could be particularly effective. Protecting and buffering pregnant persons and infants from exposure to adversity can optimize children's development and health trajectories, reduce future morbidity and mortality, and even break intergenerational cycles of adversity, but no study has synthesized experimental evidence on effectiveness of interventions to address ACEs in the perinatal period. To (1) identify perinatal ACE prevention interventions, tested in high quality randomized control trials, with a dyadic perspective examining outcomes for mother and child; (2) describe their (a) place on the public health prevention continuum and (b) incorporation of life course characteristics that aim to optimize life health trajectories; and (3) determine which interventions show evidence of effectiveness. We undertook a scoping review, using a modified PRISMA-Sc approach, of articles published in English between January 2000 and November 2023 identified through Psych info and PubMed using search terms for a broad range of adversities, with additional capture of articles from relevant reference lists. Interventions were included if they targeted an identified ACEs exposure or risk; were tested in randomized controlled trials (RCTs); reported outcome measures for both mother and child and were initiated during pregnancy. Interventions were further analyzed using the public health prevention continuum and Life Course Intervention Research (LCIR) characteristics frameworks. A two-tailed t test was used to ascertain the association between LCIR characteristics, and the outcomes achieved. Of 2148 articles identified, 57 were in scope for detailed analysis, yielding 53 unique interventions. Overall, 42 (74%) reported some positive impact; 37 (65%) for mothers; 37 (65%) for the child, and 32 (56%) for both. Interventions with the strongest evidence based on study quality and reported outcomes were co-parenting programs designed to improve the quality and function of the co-parenting relationship, home visiting interventions, and integrative health interventions incorporating baby massage and/or yoga. Half of effective interventions were secondary prevention focused. The mean number of life course characteristics was significantly higher in the studies that reported a positive impact on the mother and/or child (p = 0.003). Few studies specifically addressed ACEs as a defined set of adversities, yet a range of perinatal interventions showed positive impacts on individual ACE risks or exposures. Intentional incorporation of life course characteristics and bundling of evidence-based components into comprehensive perinatal interventions hold promise for future ACEs prevention.

Assessment of Lifecourse Social Exposome in Brain Bank Decedents

AbstractBackgroundThere is increasing evidence that the social exposome impacts the development of Alzheimer’s disease and related dementias (ADRD). The social exposome includes factors such as neighborhood disadvantage, and is thought to impact brain health across the lifecourse, particularly during sensitive life stages such as early childhood. Residential histories are required to assess dosage and timing of exposures, yet are rarely categorized and linked to brain bank cohorts. Our objective was to characterize the lifecourse neighborhood disadvantage across two Alzheimer’s Disease Research Center (ADRC) brain banks.MethodAfter abstracting publicly available residential data, we constructed residential histories using validated metrics of neighborhood disadvantage, nationwide Area Deprivation percentile rankings (ADI), constructed for each census timeframe from 1910‐present, to measure lifecourse social exposome time‐concordantly aligned to participant life‐year. ADIs were linked for all available years between birth and death, ranging from age 0 to 103. Greater ADI values denote living in higher neighborhood disadvantage. These ADIs were linked to the residential histories for each decedent and used to calculate two sensitive life stages: ages 0‐19 and 40‐60. A repeated measures one‐way ANOVA determined variance in ADI both within and between these sensitive life stages.ResultThis sample contained 1309 decedents from two brain. To date, 1230 decedents have been linked to at least one ADI timepoint, with an average of 81% (71‐88%) of all life‐course years accounted for via ADI linkage. The mean ADI for the 0‐19 period was 23.5 (SD = 22.3, 5.0‐36.9), while the 40‐60 period was 22.0 (21.6, 5.0‐34.0). A repeated measures one‐way ANOVA found a statistically significant difference in ADI between the two windows of time.ConclusionTissue banked samples are not typically characterized on social determinants of health. Here we show that determining lifecourse social exposomes are feasible using publicly available data. To our knowledge, this is the first time such characterization has been successfully performed. Efforts to link decedents to ADI timepoints are still ongoing, which will reduce missingness, enhance measurement precision, and allow for comparison between all life stages. This work provides a unique methodology for assessing the social exposome in relation to ADRD brain pathology.

Growth and fatty acid composition of pikeperch (Sander lucioperca L., 1758) larvae under altered feeding protocol including the copepod Apocyclops panamensis (Marsh, 1913)

Alternative live feeds for small and sensitive fish early life stages such as pikeperch (Sander lucioperca L., 1758) can improve the larval quantity, quality and performance in aquaculture. Therefore, this study evaluated the cyclopoid copepod Apocyclops panamensis (Marsh, 1913) as live feed for pikeperch larviculture from day 11 post hatch (dph) in two independent experiments. In both experiments, pikeperch larvae had the highest specific growth rate (SGR) when they fed on Brachionus plicatilis until dph 11 and A. panamensis until dph 16–18. SGR was related to a decrease in total fatty acids (FAs), saturated FAs and monounsaturated FAs in pikeperch larvae, indicating their use as energy for growth. Within the polyunsaturated FAs, docosahexaenoic acid (DHA) increased in larvae fed with A. panamensis and coincided with the highest SGR suggesting that DHA is accumulated in larvae as structural FA. Our study demonstrated a suitable pikeperch larval fatty acid composition for growth after feeding A. panamensis compared with Artemia sp. from dph 11 until dph 16 and previously fed with B. plicatilis. Moreover, it highlighted the importance of the dietary PUFAs in pikeperch rearing, specifically of linoleic acid (LA) from dph 4 until dph 11 and of DHA from dph 11 onwards.

Food in my life: How Australian adolescents perceive and experience their foodscape

Food choice has long been recognized as an interaction between psychological, social, cultural, economic, and biological forces through life course events and experiences. Adolescence is a particularly sensitive life stage during which personal and external environments influence food decisions and attitudes that can have long-term implications. Young people represent future households, yet little is understood about their perspectives on, and experiences of, their foodscape. To address this, a photovoice study with thirty-two students was undertaken at three state high schools with differing foodscapes in South East Queensland (Australia). Adolescent perspectives on foodscapes highlighted the food in front of them (either common or favourite foods), food routines, their emotional relationship with food, and the important role that family has in shaping their relationship with food (in particular mothers). Adolescents demonstrated an astute awareness of healthy/good and unhealthy/bad foods in relation to ingredients, ways of eating and different types of foods. Yet they expressed noticeable confusion on this matter, referring to some foods as “healthy-ish”, or describing a "balanced" diet as consuming something healthy followed by something unhealthy. We found that adolescents are inundated by discretionary foods on a daily basis, however, are not particularly cognisant of them. These findings have direct implications for preventative health messages targeting adolescents.

Environmental hazards of WELGRO® Cu+Zn: A nano-enabled fertilizer

Nanoagrochemicals have the potential to revolutionize agriculture towards a precision farming system, able to reduce application rates and consequently their environmental footprint, while keeping efficacy. Several nanoagrochemicals (including nanopesticides (Npes) and nanofertilizers (Nfer)) are already commercialized but the environmental risk assessment of these advanced materials is often lacking. In the present study, we studied the commercial fertilizer WELGRO® Cu + Zn and assessed its ecotoxicity to the soil invertebrate species Enchytraeus crypticus (Oligochaeta), further comparing it to its individual active substances CuO and ZnO. To get a comprehensive picture of possible effects, we used four types of highly relevant tests in LUFA 2.2 soil: 1) avoidance behaviour (2 days), 2) reproduction (OECD standard, 28 d), 3) its extension (56 d), and 4) the full life cycle (FLC) (46 d) – this high level of hazard screening allows for increased interpretation. The results confirmed the nano-features of WELGRO® and a higher toxicity than the mixture of the individual components CuO + ZnO. E. crypticus avoided the soil spiked with WELGRO® and CuO + ZnO, this being the most sensitive endpoint - avoidance behaviour. Both WELGRO® and the active substances were little to non-toxic based on the OECD standard test. However, the toxicity dramatically increased in the tests focussing on longer-term sustainability measures, i.e., 56 days, ca. 170 for WELGRO®. This seems related to the nano-features of WELGRO®, e.g., slow release of ions from the nanoparticles throughout time. The FLCt results showed WELGRO® affected hatching and juveniles’ survival, being these the most sensitive life stages. Hence, under actual real world field usage scenarios, i.e., based on the recommended application rates, nanoenabled WELGRO® can affect oligochaete populations like enchytraeids, both via the immediate avoidance behaviour and also via prolonged exposure periods.

Examining the reproductive success of bull kelp (Nereocystis luetkeana, Phaeophyceae, Laminariales) inclimate change conditions.

Climate change is affecting marine ecosystems in many ways, including raising temperatures and leading to ocean acidification. From 2014 to 2016, an extensive marine heat wave extended along the west coast of North America and had devastating effects on numerous species, including bull kelp (Nereocystis luetkeana). Bull kelp is an important foundation species in coastal ecosystems and can be affected by marine heat waves and ocean acidification; however, the impacts have not been investigated on sensitive early life stages. To determine the effects of changing temperatures and carbonate levels on Northern California's bull kelp populations, we collected sporophylls from mature bull kelp individuals in Point Arena, CA. At the Bodega Marine Laboratory, we released spores from field-collected bull kelp, and cultured microscopic gametophytes in a common garden experiment with a fully factorial design crossing modern conditions (11.63 ± 0.54°C and pH 7.93 ± 0.26) with observed extreme climate conditions (15.56 ± 0.83°C and 7.64 ± 0.32 pH). Our results indicated that both increased temperature and decreased pH influenced growth and egg production of bull kelp microscopic stages. Increased temperature resulted in decreased gametophyte survival and offspring production. In contrast, decreased pH had less of an effect but resulted in increased gametophyte survival and offspring production. Additionally, increased temperature significantly impacted reproductive timing by causing female gametophytes to produce offspring earlier than under ambient temperature conditions. Our findings can inform better predictions of the impacts of climate change on coastal ecosystems and provide key insights into environmental dynamics regulating the bull kelp lifecycle.

Comparative Toxicity of Seven Aqueous Film-Forming Foam to In Vitro Systems and Mus.

The comparative toxicity of six per- and polyfluoroalkyl substance (PFAS)-free and one PFAS-containing aqueous film-forming foam (AFFF) was evaluated in an outbred mouse species as well as several in vitro assays. The in vivo toxicological profile of PFAS-free AFFFs in short-term, high-concentration exposures is different than that of a PFAS-containing AFFF. The PFAS-containing reference product induced increased liver weights, while the PFAS-free AFFFs were linked to either decreased or unaffected relative liver weights. The in vitro toxicological profile across PFAS-free AFFFs was uniform except in the Microtox® assay, where thresholds were variable and spanned several orders of magnitude. This direct comparison of products through short-term toxicity tests and in vitro screenings represents early data to support evaluation of potential regrettable substitutions when selecting alternative PFAS-free AFFFs. Further work in diverse taxa (e.g., aquatic organisms, terrestrial invertebrates, birds) and mammalian studies capturing sensitive life stages will refine and expand this data set across a range of risk-relevant toxicological endpoints. Environ Toxicol Chem 2023;42:2364-2374. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

Spawning time in adult polar cod (Boreogadus saida) altered by crude oil exposure, independent of food availability

ABSTRACT Fish early life stages are well known for their sensitivity to crude oil exposure. However, the effect of crude oil exposure on adults and their gametes during their spawning period is not well studied. Polar cod, a key arctic fish, may be at risk for crude oil exposure during this potentially sensitive life stage. Additionally, this species experiences lower food availability during their spawning season, with unknown combined consequences. In the present study, wild-caught polar cod were exposed to decreasing levels of a water-soluble fraction (WSF) of crude oil or control conditions and fed either at a low or high feed ration to assess the combined effect of both stressors. Samples were taken during late gonadal development, during active spawning (spawning window), and in the post-spawning period. Histology analysis of gonads from fish sampled during the spawning window showed that oil-exposed polar cod were more likely to have spawned compared to controls. Oil-exposed females had 947 differentially regulated hepatic genes, and their eggs had a higher polycyclic aromatic hydrocarbon body burden compared to controls. Feed ration did not consistently affect polar cod’s response to oil exposure for the endpoints measured, however, did alone result in decreases in some sperm motility parameters. These results suggest that polar cod’s spawning period is a sensitive life event to crude oil exposure, while feed limitation may play a minor role for this supposedly capital breeder. The effects of adult exposure to crude oil on gamete quality and the next generation warrant further investigation.

Invited Perspective: PFAS in Breast Milk and Infant Formula-It's Time to Start Monitoring.

Invited Perspective: PFAS in Breast Milk and Infant Formula-It's Time to Start Monitoring.

Chemical hazard of robotic hull in-water cleaning discharge on coastal embryonic fish

In-water cleaning (IWC) involves the removal of biofilms and foulants from the hull of a ship using brush or water jet. During IWC, several factors associated with the harmful chemical contaminants release to the marine environment, which can create “hotspots” of chemical contamination in coastal areas. To elucidate the potential toxic effects of IWC discharge, we investigated developmental toxicity in embryonic flounder, which are sensitive life stage to chemical exposure. Zinc and copper were the dominant metals, while zinc pyrithione was the most abundant biocide associated with IWC discharge in two remotely operated IWC. Discharge from IWC carried by both remotely operated vehicles (ROVs) produced developmental malformations including pericardial edema, spinal curvature, and tail-fin defects. In an analyses of differential gene expression profiles (fold-change of genes with a cutoff < 0.05) as assessed by high-throughput RNA sequencing, genes associated with muscle development were commonly and significantly changed. The gene ontology (GO) of embryos exposed to IWC discharge from ROV A activities highly enriched muscle and heart development, while cell signaling and transport were evident in embryos exposed to IWC discharge of ROV B. We analyzed the gene network by significant GO terms. In the network, TTN, MYOM1, CASP3, and CDH2 genes appeared to be key regulators of the toxic effects on muscle development. In embryos exposed to ROV B discharge, HSPG2, VEGFA, and TNF genes related to the nervous system pathway were affected. These results shed light on the potential impacts of muscle and nervous system development in non-target coastal organisms exposed to contaminants found in IWC discharge.

Toxicity risks associated with trace metals call for conservation of threatened fish species in heavily sediment-laden Yellow River

Trace metals and metalloids in aquatic ecosystems may lead to adverse effects on the survival of fish, especially in the sensitive life stages of vulnerable species. It is still unknown whether threatened fish species in the heavily sediment-laden Yellow River are exposed to toxicity risks associated with multiple trace metals. Herein, we analyzed the concentrations of trace metals in aquatic environmental media and fish tissues across the Yellow River mainstream and assessed the level of metal toxicity to threatened fish. Significantly different concentrations of trace metals in fish tissues were measured between at least two categories among near-threatened, vulnerable, endangered, and critically endangered fish. No metal showed a higher concentration in demersal fish than in pelagic fish. Substantially low metal toxicity was observed for the gill of Rhinogobio nasutus (near-threatened) in the upper reaches, as well as for the gill and liver of Silurus lanzhouensis (endangered) in the middle reaches. High contents of suspended sediment in water and high metal concentrations in sediment and suspended matter could influence the survival and reproduction of fish, especially those already with threatened status.

Life Cycle Model Reveals Sensitive Life Stages and Evaluates Recovery Options for a Dwindling Pacific Salmon Population

AbstractPopulation models, using empirical survival rate estimates for different life stages, can help managers explore whether various management options could stabilize a declining population or restore it to former levels of abundance. Here we used two decades of data on five life stages of the population of Sockeye SalmonOncorhynchus nerkain the Cedar River to create and parameterize a life cycle model. This formerly large but unproductive population is now in steep decline despite hatchery enhancement. We gathered population‐specific data on survival during five stages: (1) egg to fry, (2) fry to presmolt, (3) presmolt to adult return from the ocean, (4) adult en route from the ocean to the spawning grounds, and (5) reproduction. We ground‐truthed the model to ensure its fit to the data, and then we modified survival and other parameters during various stages to examine future scenarios. Our analyses revealed that low survival of juveniles in Lake Washington (stage 2: averaging only 3% over the past 20 years), survival of adults returning to freshwater to spawn (stage 4), and survival of adults on spawning grounds to reproduce (stage 5) are likely limiting factors. Combined increases in these stages and others (specifically, the proportion of fish taken into the hatchery to be spawned) might also recover the population. As in other integrated hatchery populations, managers must weigh options relating to balancing the fraction of natural‐ and hatchery‐origin fish, and our results showed that increasing the fraction of fish taken into the hatchery alone will not recover the population. Our model brings together population‐specific data to help managers weigh conservation strategies and understand which stages and habitats are most limiting and how much survival must increase to achieve recovery targets. By extension, our analyses also reveal the utility of such models in other cases where stage‐specific data are available.

Natural and synthetic microfibers alter growth and behavior in early life stages of estuarine organisms

Increasing shares of microfibers are being detected in environmental samples and a closer look to identify the risk associated with them using ecologically relevant endpoints, especially at sensitive early life stages, is needed. To assess exposure hazards, we used rope samples representative of fiber types ubiquitous in coastal systems, where microfibers are often the most common debris type found in the water column. To compare responses to natural vs. synthetic microfibers, we used rinsed “natural” cotton, polyester, and polypropylene microfibers (80-150 µm length, 8-20 µm width) created from the rope. Larval and juvenile estuarine indicator species Inland Silverside (Menidia beryllina) and mysid shrimp (Americamysis bahia), respectively, were exposed to these three microfiber types at three concentrations (3, 10, 30 particles/ml) along a 5-25 PSU salinity gradient to mimic estuarine conditions. Behavioral responses, growth, and ingestion were measured. The cotton microfibers were not detected in the digestive tracts of Silversides, however, both the polyester and polypropylene microfibers were detected in the Silversides’ stomach and gut lining. None of the fiber types were detected in mysid shrimps. Mysids exposed to cotton microfibers had fewer behavioral effects compared to Silversides, who responded more to cotton. Cotton exerted no effect on growth in Silversides but did cause reduced growth in the mysids at the two lower salinities. In contrast, polyester and polypropylene were identified to have a significant dose dependent effect on mysid and Silverside behavior as well as growth was affected in at least one of the three salinities at concentrations as low as 3 particles/ml. Cotton impacted both the organism’s behavior more at higher salinities, whereas polyester and polypropylene had more impacts at lower salinities. This raises concerns for microfiber impacts on estuarine ecosystems and the need for policies to limit microfiber production and outfall into the aquatic environment.