Estuarine Invertebrates Research Articles

Microplastics and 17α Ethinylestradiol: How Do Different Aquatic Invertebrates Respond to This Combination of Contaminants?

The synthetic hormone 17α ethinyl estradiol (EE2) is a molecule widely used in female contraceptives and recognized as a contaminant of attention (Watch List) in the European Union due to its high consumption, endocrine effects and occurrence in aquatic environments. Its main source of introduction is domestic sewage where it can be associated with other contaminants such as microplastics (MPs). Due to their characteristics, they can combine with each other and exacerbate their isolated effects on biota. This study evaluated the combined effects of microplastics (MPs) and 17α ethinylestradiol (EE2) on two tropical estuarine invertebrate species: Crassostrea gasar and Ucides cordatus. Polyethylene particles were spiked with EE2 and organisms were exposed to three treatments, categorized into three groups: control group (C), virgin microplastics (MPs), and spiked microplastics with EE2 (MPEs). All treatments were evaluated after 3 and 7 days of exposure. Oysters exhibited changes in phase 2 enzymes and the antioxidant system, oxidative stress in the gills, and reduced lysosomal membrane stability after exposure to MPs and MPEs. Crabs exposed to MPs and MPEs after seven days showed changes in phase 1 enzymes in the gills and changes in phases 1 and 2 enzymes in the hepatopancreas, such as disturbed cellular health. The combined effects of microplastics and EE2 increased the toxicity experienced by organisms, which may trigger effects at higher levels of biological organization, leading to ecological disturbances in tropical coastal ecosystems.

Comparing the effect of larval dispersal strategies on morphological versus genetic differentiation in two neotropical fiddler crabs

AbstractThe dispersal mode of estuarine invertebrates has a strong effect on genetic variability and phenotypic expression, potentially maintaining gene flow among widely separated populations or limiting connectivity among close ones. Understanding the dispersal strategies effects can support adequate strategies for environment management and understand the evolutionary history of the studied species. A comparative study on the effect of larval dispersal strategies (export vs retention) along the overall geographic distribution ranges of adult populations of two co‐distributed fiddler crab species was performed. Geometric morphometric techniques were used to evaluate morphological differentiation in the shape of the carapace and major cheliped propodus in 10 populations of Minuca mordax and five populations of Leptuca leptodactyla. Potential genetic differentiation was assessed using DNA sequence data from up to 170 fiddler crab specimens, corresponding to the mitochondrial gene cytochrome c oxidase subunit 1 (COX1). Patterns of genetic and morphological characteristics diverged among populations of both species. In terms of morphology, populations of both species showed intraspecific variation in the shape of the carapace and, to a lesser extent, in the major cheliped propodus. This observed intraspecific variation followed a clear geographic pattern of morphometric differentiation, in which the geographic origin is associated with a phenotypic response to the environmental diversity along the extended Brazilian coast. In contrast, there are shared haplotypes in populations separated by more than 4000 km, but with significant ΦST values among most populations of L. leptodactyla and M. mordax, suggesting a moderate to high level of gene flow. Therefore, it can be concluded that the split of the Central South Equatorial Current has not acted as an efficient long‐term barrier to the dispersal of larvae in both species. In M. mordax, a slight limitation of genetic exchange can be observed between the southernmost populations and the remaining ones. This first evidence of genetic structuring within this widely distributed species is consistent with its documented strategy to retain larvae in the estuarine environments. However, occasional transport of larvae to more open coastal waters seems to maintain stepwise gene flow between neighboring populations. Overall, our results still provide evidence of more pronounced genetic homogeneity in a species with a larval export strategy (L. leptodactyla) compared to a species with a larval retention strategy (M. mordax). This suggests that larval dispersal strategies, coupled with the microhabitat in which the respective species occur, have a noticeable effect on the degree of gene flow. Most likely, these biological aspects are further influenced by the estuarine and coastline geomorphology.

A horizon scan exercise for aquatic invasive alien species in Iberian inland waters

As the number of introduced species keeps increasing unabatedly, identifying and prioritising current and potential Invasive Alien Species (IAS) has become essential to manage them. Horizon Scanning (HS), defined as an exploration of potential threats, is considered a fundamental component of IAS management. By combining scientific knowledge on taxa with expert opinion, we identified the most relevant aquatic IAS in the Iberian Peninsula, i.e., those with the greatest geographic extent (or probability of introduction), severe ecological, economic and human health impacts, greatest difficulty and acceptability of management. We highlighted the 126 most relevant IAS already present in Iberian inland waters (i.e., Concern list) and 89 with a high probability of being introduced in the near future (i.e., Alert list), of which 24 and 10 IAS, respectively, were considered as a management priority after receiving the highest scores in the expert assessment (i.e., top-ranked IAS). In both lists, aquatic IAS belonging to the four thematic groups (plants, freshwater invertebrates, estuarine invertebrates, and vertebrates) were identified as having been introduced through various pathways from different regions of the world and classified according to their main functional feeding groups. Also, the latest update of the list of IAS of Union concern pursuant to Regulation (EU) No 1143/2014 includes only 12 top-ranked IAS identified for the Iberian Peninsula, while the national lists incorporate the vast majority of them. This fact underlines the great importance of taxa prioritisation exercises at biogeographical scales as a step prior to risk analyses and their inclusion in national lists. This HS provides a robust assessment and a cost-effective strategy for decision-makers and stakeholders to prioritise the use of limited resources for IAS prevention and management. Although applied at a transnational level in a European biodiversity hotspot, this approach is designed for potential application at any geographical or administrative scale, including the continental one.

Multi-omics eco-surveillance of complex legacy contamination with a locally adapted estuarine invertebrate

Complex legacy contamination from human use is a major issue for estuaries globally. In particular, contamination of water and sediments with bioavailable metals/metalloids, in addition to other industrial contaminants, such as hydrocarbons. Yet, understanding of complex toxicity and local adaptation in field exposed, non-model, invertebrate communities is limited. Herein, we apply multi-omics (metabolomics, lipidomics, proteomics) coupled to traditional sediment quality analyses, to better characterise molecular and cellular responses necessary for application to monitoring, as an eco-surveillance tool. Using these approaches, we characterise functional phenotypes of a sediment associated invertebrate (sipunculid), from an estuary exposed to complex legacy contamination (metals: Zn, Hg, Cd, Pb, Cu, As; and polycyclic aromatic hydrocarbons, PAHs). We sampled individuals at a range of exposure sites, highly (NTB5), moderately (NTB13), and lesser-influenced reference sites. Size differences were observed in sampled individuals between sites, with smaller individuals collected from NTB13. Analysis of environmental variables that correlated with change in the metabolite data revealed that the metabolism of smaller individuals at medium exposure NTB13 was highly differentiated by sediment concentrations of Hg, despite higher concentrations at more exposed NTB5. Functional phenotypes of these smaller individuals were characterised by sulphur and aromatic amino acid metabolism, increases in oxidised intermediates, upregulation of protein responses to oxidative stress, and melanin synthesis, and saturation of membrane and storage of lipids; in addition to the metabolism of naphthalene (PAH). Such widespread change was not observed in the metabolite and lipid profiles of larger individuals at high exposure NTB5, suggesting possible differences in effects between sites may also be associated with size (developmental stage, or age) and/or PAH exposure. This study serves to further understanding of differing modes of toxicity and local adaptation to multiple contaminants, and drivers of functional change in a complex estuary environment.

Multi-and transgenerational synergistic effects of glyphosate and chlorpyrifos at environmentally relevant concentrations in the estuarine rotifer Proales similis

We evaluated the multi-and transgenerational effects of single and combined environmentally relevant concentrations of glyphosate (GLY) and chlorpyrifos (CPF) in the estuarine rotifer Proales similis. The acute and chronic toxicities of GLY and CPF were determined as individual compounds and as a mixture. Rotifers were exposed to environmental concentrations of GLY (1, 10, 100, and 1000 μg/L) and CPF (0.1, 1, 5, and 10 μg/L). The main findings were as follows: (i) the LC50 values were 33.91 mg/L (GLY) and 280 μg/L (CPF); (ii) the toxic unit (TU50) of the mixture was 0.30, corresponding to 10.17 mg/L GLY and 83 μg/L CPF; (iii) the multigenerational study indicated that the tested concentrations of GLY and CPF, both single and combined, significantly and consistently decreased the growth rates of P. similis from the F0 to F6 generations; (iv) in most cases, GLY and CPF mixtures induced a strong synergistic effect; and (v) transgenerational effects were detected in the F4 generation, especially GLY and CPF in higher equitoxic proportions. These effects seem to dissipate in F5. Across multigeneration, a slight recovery could indicate population resilience to pollution. Our findings suggest that a mixture of GLY and CPF at environmental concentrations is likely to occur under real field conditions, increasing the risk to marine and estuarine invertebrates such as rotifers.

Tyre particle exposure affects the health of two key estuarine invertebrates

Tyre wear particles may be the largest source of microplastic to the natural environment, yet information on their biological impacts is inadequate. Two key estuarine invertebrates; the clam Scrobicularia plana and the ragworm Hediste diversicolor were exposed to 10% tyre particles in sediment for three days. Both species consumed the particles, although S. plana consumed 25x more than H. diversicolor (967 compared with 35 particles.g−1 wet weight, respectively). We then investigated the impact of 21 days exposure to different concentrations of tyre particles in estuarine sediments (0.2, 1, and 5% dry weight sediment) on aspects of the health of S. plana and H. diversicolor. Reductions in feeding and burial rates were observed for S. plana but not H. diversicolor, whilst both species showed a decrease in protein content in response to the greatest tyre particle concentration (5%), linked to an 18% decrease in energy reserves for H. diversicolor. Five percent tyre particle exposure led to an increase in total glutathione in the tissues of H. diversicolor, whilst lipid peroxidation decreased in the digestive glands of S. plana, possibly due to an increase in cell turnover. This study found that S. plana's health was impacted at lower concentrations than H. diversicolor, likely due to its consumption of large quantities of sediment. At the high exposure concentration (5%), the health of both invertebrates was impacted. This study did not separate the effects caused by the microplastic particles versus the effects of the chemical additives leaching from these particles, but our results do indicate that future studies should investigate effects in isolation and in combination, to determine the main drivers of toxicity.

Potential impacts from simulated vessel noise and sonar on commercially important invertebrates.

Human usage of coastal water bodies continues to increase and many invertebrates face a broad suite of anthropogenic stressors (e.g., warming, pollution, acidification, fishing pressure). Underwater sound is a stressor that continues to increase in coastal areas, but the potential impact on invertebrates is not well understood. In addition to masking natural sound cues which may be important for behavioral interactions, there is a small but increasing body of scientific literature indicating sublethal physiological stress may occur in invertebrates exposed to high levels of underwater sound, particularly low frequency sounds such as vessel traffic, construction noise, and some types of sonar. Juvenile and sub-adult blue crabs (Callinectes sapidus) and American lobsters (Homarus americanus) were exposed to simulated low-frequency vessel noise (a signal was low-pass filtered below 1 kHz to ensure low-frequency content only) and mid-frequency sonar (a 1-s 1.67 kHz continuous wave pulse followed by a 2.5 to 4.0 kHz 1-s linear frequency modulated chirp) and behavioral response (the animal’s activity level) was quantified during and after exposure using EthoVision XT™ from overhead video recordings. Source noise was quantified by particle acceleration and pressure. Physiological response to the insults (stress and recovery) were also quantified by measuring changes in hemolymph heat shock protein (HSP27) and glucose over 7 days post-exposure. In general, physiological indicators returned to baseline levels within approximately 48 h, and no observable difference in mortality between treatment and control animals was detected. However, there was a consistent amplified hemolymph glucose signal present 7 days after exposure for those animals exposed to mid-frequency sound and there were changes to C. sapidus competitive behavior within 24 h of exposure to sound. These results stress the importance of considering the impacts of underwater sound among the suite of stressors facing marine and estuarine invertebrates, and in the discussion of management actions such as protected areas, impact assessments, and marine spatial planning efforts.

Multi-Omics Eco-Surveillance of Complex Legacy Contamination with a Locally Adapted Estuarine Invertebrate

Multi-Omics Eco-Surveillance of Complex Legacy Contamination with a Locally Adapted Estuarine Invertebrate

Tyre Particle Exposure Affects the Health of Two Key Estuarine Invertebrates

Tyre Particle Exposure Affects the Health of Two Key Estuarine Invertebrates

Metabolomics as a tool for in situ study of chronic metal exposure in estuarine invertebrates

Estuaries are subject to intense human use globally, with impacts from multiple stressors, such as metal contaminants. A key challenge is extending beyond traditional monitoring approaches to understand effects to biota and system function. To explore the metabolic effects of complex metal contaminants to sediment dwelling (benthic) fauna, we apply a multiple-lines-of-evidence approach, coupling environmental monitoring, benthic sampling, total metals analysis and targeted metabolomics.We characterise metabolic signatures of metal exposure in three benthic invertebrate taxa, which differed in distribution across sites and severity of metal exposure: sipunculid (very high), amphipod (high), maldanid polychaete (moderate). We observed sediment and tissue metal loads far exceeding sediment guidelines where toxicity-related adverse effects may be expected, for metals including, As, Cd, Pb, Zn and Hg.Change in site- and taxa-specific metabolite profiles was highly correlated with natural environmental drivers (sediment total organic carbon and water temperature). At the most metal influenced sites, metabolite variation was also correlated with sediment metal loads. Using supervised multivariate regression, taxa-specific metabolic signatures of increased exposure and possibility of toxic effects were characterised against multiple reference sites. Metabolic signatures varied according to each taxon and degree of metal exposure, but primarily indicated altered cysteine and methionine metabolism, metal-binding and elimination (lysosomal) activity, coupled to change in complex biosynthesis pathways, responses to oxidative stress, and cellular damage.This novel multiple-lines-of-evidence approach combining metabolomics with traditional environmental monitoring, enabled detection and characterisation of chronic metal exposure effects in situ in multiple invertebrate taxa. With capacity for application to rapid and effective monitoring of non-model species in complex environments, these approaches are critical for improved assessment and management of systems that are increasingly subject to anthropogenic drivers of change.

Microplastic characteristics in organisms of different trophic levels from Liaohe Estuary, China

Microplastics are a growing concern globally due to their small size and easy ingestion by terrestrial and aquatic organisms, resulting in potential adverse impacts on wildlife. However, current data regarding microplastics in wild organisms in different trophic levels is limited. This study investigated microplastic characteristics, including their abundance, size, shape and polymer type, in estuarine invertebrates and vertebrates. Resultantly, polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) were the predominant microplastics found, as confirmed by a Fourier transform infrared spectrometer (FT-IR). An average microplastic abundance of 0.83 ± 0.99 to 3.87 ± 2.18 items/individual was detected across all species, including sandworm, mollusks, crustacean and fish, but they were not found in all individuals. Microplastics ranged from 52 μm to 5392 μm in size, and the shapes were consisted of fiber, fragment, and pellet. Moreover, the detection ratio (91.95%) and abundance (3.34 ± 2.17 items/individual) of microplastics in fish were significantly higher than in sandworm (42.86%, 0.88 ± 1.04 items/individual), mollusks (66.97%, 1.42 ± 1.41 items/individual) and crustaceans (66.66%, 1.33 ± 1.32 items/individual) (p < 0.05). Furthermore, a positive relationship was identified between microplastic abundance and the trophic level of organisms. These findings imply that microplastics might transfer along the food chain and accumulate at organisms in higher trophic levels.

Acute Polychlorinated Biphenyl Benthic Invertebrate Toxicity Testing to Support the 2017 Chronic Dose-Response Sediment Injury Model.

As managers and decision makers evaluate pollutant risk, it is critical that we are able to measure an assessment of the injury. Often, these estimates are difficult to determine for benthic organisms, so in 2017 a chronic polychlorinated biphenyl (PCB) sediment dose-response model to predict benthic invertebrate injury was proposed. Given both natural resource trustee and consultant questions following publication concerning that the aqueous chronic toxicity testing data used in the 2017 model development were primarily from the 1970s and 1980s, this follow-up short communication is meant to provide the user some additional data that are more recent. With the advances in analytical and quantitative environmental chemistry (i.e., better detection limits and congener separation), we chose to complete acute aquatic toxicity testing using 3 estuarine invertebrates and lethal endpoints (20 and 50% lethal concentrations). This acute testing was selected because chronic aquatic testing for PCBs outside of the data used in the 2017 study was not available to us. The aquatic results used in the present study were changed to sediment using equilibrium partitioning, as done in the 2017 chronic model, after using the same organic-carbon partition coefficient and total organic carbon for our equilibrium partitioning (EqP)-measured calculations. Based on these acute aquatic toxicity results and a general acute-to-chronic injury concentration ratio of approximately 10, we found that the 2017 model was valid and, hence, that a 1.0 µg/g chronic PCB sediment criterion is a reasonable estimation of potential benthic invertebrate injury. This was followed by spiked sediment tests where percent acute sediment injury was compared to the EqP-derived chronic value and the results from 2017; modest agreement is shown. Environ Toxicol Chem 2021;40:1188-1193. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Diet shift of Chinese mitten crab (Eriocheir sinensis) during its upstream migration indicated by stable isotopes and fatty acid composition

ABSTRACT The Chinese mitten crab (Eriocheir sinensis) is the largest estuarine invertebrate and one of the most important fishery resources in China. Diet significantly affected survival of the crab. To study the diet of this species during its upstream migration, larvae and juvenile crabs as well as their potential food sources were sampled from three regions along the Changjiang River. Stable isotopes (δ13C and δ15N) in and fatty acid compositions of the samples were analysed to elucidate the crabs’ dietary shift during upstream migration. With upstream migration from the Changjiang Estuary, the average δ13C value in crabs decreased from −20.6 to −25.2‰, and the δ15N value increased from 3.0 to 11.8‰. The fatty acid compositions also changed significantly, with levels of C20:4n-6, C18:2n-6, and C18:3n-3 increasing during upstream migration. However, the levels of C15:0, C17:0, C16:1n-7, and 20:1n-9 exhibited the opposite trend. Pelagic marine prey items (e.g. zooplankton and bacteria) were the dominant food sources of megalopae and early juvenile crabs. The contribution of benthic terrigenous origin carbon sources (e.g. macrophytes and zoobenthos) to the juvenile crab diet sharply increased. The dietary information on the Chinese mitten crab can promote the restoration of wild population and sustainable development of crab aquaculture.

Effects of prolonged mouth closure in a temporarily open/closed estuary: a summary of the responses of invertebrate communities in the uMdloti Estuary, South Africa

Prolonged mouth closure in estuaries is often associated with hypersalinity, mainly as a result of reduced freshwater inflow. However, on the KwaZulu-Natal coast, South Africa, temporarily open/closed estuaries have a tendency towards hyposalinity during closed mouth conditions, primarily because of their perched nature reducing saltwater intrusion, but also due to persistent freshwater inputs, together with seepage of saline water through the sand berm into the sea. We investigated a system, the uMdloti Estuary, experiencing extended periods of mouth closure over two years with the aim of documenting the response of invertebrates to such conditions. Specifically, estuarine invertebrate biodiversity was severely diminished, which was attributed to persistently low salinity, rather than poor water quality due to the absence of flushing. Secondly, a distinct brackish/freshwater community established itself within the mesozooplankton and benthic invertebrate assemblages, including invasive species. Marine overwash of the berm and a short mouth breaching aided the return of estuarine species for only very brief periods (weeks). We conclude that although estuarine species are quick to re-colonise the estuary after a breach, prolonged mouth closure along extended stretches of coast might severely reduce estuarine invertebrate biodiversity. Management options are preferably the provision of an adequate freshwater inflow to allow natural breaching, or else artificial breaching, to facilitate several openings per year as well as for a long enough tidal phase to permit the establishment of an estuarine salinity gradient.

Thermal exposure and transgenerational plasticity influence embryonic success in a bivoltine estuarine sea hare

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 634:199-211 (2020) - DOI: https://doi.org/10.3354/meps13207 Thermal exposure and transgenerational plasticity influence embryonic success in a bivoltine estuarine sea hare Richelle L. Tanner1,2,5,*, Rauri C. K. Bowie1,3, Jonathon H. Stillman1,2,4 1Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA 2Estuary and Ocean Science Center, San Francisco State University, Tiburon, CA 94920, USA 3Museum of Vertebrate Zoology, University of California, Berkeley, Berkeley, CA 94720, USA 4Department of Biology, San Francisco State University, San Francisco, CA 94132, USA 5Present address: School of Biological Sciences, Washington State University, Pullman, WA 99163, USA *Corresponding author: richelle.tanner@richelletanner.com ABSTRACT: Phenotypic plasticity has the potential to influence environmental adaptation on extremely short evolutionary timescales. Transgenerational plasticity (TGP) allows parents to provision their offspring for rapid environmental shifts in as little as one generation. We hypothesized that organisms that produce multiple generations of offspring each year use TGP to maximize their fitness under predictable fluctuations in seasonal environments. Using the direct-developing bivoltine eelgrass sea hare Phyllaplysia taylori as a test case, we examined the impacts of seasonal thermal variation (i.e. average temperature and acute heat stress) on physiological tolerance, maternal provisioning, and developmental plasticity across multiple generations. In the laboratory, we acclimated seasonally acclimatized adults from successive generations at 13, 17, and 21°C in order to assess plasticity of thermal tolerance limits. We also examined the effects of thermal acclimation and heat stress on reproductive output within a single generation in order to characterize TGP. Physiological plasticity, including but not limited to TGP, successfully maintained the viability of offspring under 2 seasonal conditions regularly experienced in the wild, despite differences in the density of offspring per clutch and large individual differences in offspring numbers under these conditions. These results indicate that warmer conditions (21°C) disrupt current patterns of plasticity and warrant further investigation of the long-term effects of chronic stress on TGP under climate change. KEY WORDS: Phyllaplysia taylori · Physiological plasticity · Seasonal variation · Estuarine invertebrate · Thermal tolerance Full text in pdf format Supplementary material PreviousNextCite this article as: Tanner RL, Bowie RCK, Stillman JH (2020) Thermal exposure and transgenerational plasticity influence embryonic success in a bivoltine estuarine sea hare. Mar Ecol Prog Ser 634:199-211. https://doi.org/10.3354/meps13207 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 634. Online publication date: January 23, 2020 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2020 Inter-Research.

New insights on the impacts of e-waste towards marine bivalves: The case of the rare earth element Dysprosium

With the technological advances and economic development, the multiplicity and wide variety of applications of electrical and electronic equipment have increased, as well as the amount of end-of-life products (waste of electrical and electronic equipment, WEEE). Accompanying their increasing application, there is an increasing risk to aquatic ecosystems and inhabiting organisms. Among the most common elements present in WEEE are rare earth elements (REE) such as Dysprosium (Dy). The present study evaluated the metabolic and oxidative stress responses of mussels Mytilus galloprovincialis exposed to an increasing range of Dy concentrations, after a 28 days experimental period. The results obtained highlighted that Dy was responsible for mussel’s metabolic increase associated with glycogen expenditure, activation of antioxidant and biotransformation defences and cellular damage, with a clear loss of redox balance. Such effects may greatly impact mussel’s physiological functions, including reproduction capacity and growth, with implications for population conservation. Overall the present study pointed out the need for more research on the toxic impacts resulting from these emerging pollutants, especially towards marine and estuarine invertebrate species.

Moderate reductions in dissolved oxygen may compromise performance in an ecologically-important estuarine invertebrate.

Coastal ecosystems, including estuaries, are increasingly pressured by expanding hypoxic regions as a result of human activities such as increased release of nutrients and global warming. Hypoxia is often defined as oxygen concentrations below 2 mL O2 L-1. However, taxa vary markedly in their sensitivity to hypoxia and can be affected by a broad spectrum of low oxygen levels. To better understand how reduced oxygen availability impacts physiological and molecular processes in invertebrates, we investigated responses of an estuarine amphipod to an ecologically-relevant level of moderate hypoxia (~2.6 mL O2 L-1) or severe hypoxia (~1.3 mL O2 L-1). Moderate hypoxia elicited a reduction in aerobic scope, and widespread changes to gene expression, including upregulation of metabolic genes and stress proteins. Under severe hypoxia, a marked hyperventilatory response associated with maintenance of aerobic performance was accompanied by a muted transcriptional response. This included a return of metabolic genes to baseline levels of expression and downregulation of transcripts involved in protein synthesis, most of which indicate recourse to hypometabolism and/or physiological impairment. We conclude that adverse ecological effects may occur under moderate hypoxia through compromised individual performance and, therefore, even modest declines in future oxygen levels may pose a significant challenge to coastal ecosystems.

Response of estuarine benthic invertebrates to field applications of insecticide

The response of estuarine invertebrates to the neonicotinoid insecticide imidacloprid following field applications in Willapa Bay, Washington (U.S.A.) was examined using Principal Response Curve (PRC) Analysis. A total of 60 analyses was conducted to examine responses of six taxonomic assemblages (polychaetes, non-juvenile polychaetes only, mollusks, non-juvenile mollusks only, crustaceans, and all invertebrates combined). Eight trials were conducted among five sites over the course of three years. Five of the eight featured a liquid formulation of imidacloprid and three a granular formulation. Both the response and treatment effects were significant (p < 0.05) among 49 of the analyses, but pre-treatment differences in the abundance and composition of the assemblages at test and control plots often confounded interpretation of results. In the majority of analyses, the response of the treated assemblage relative to the control assemblage remained relatively stable over time, indicating a neutral treatment effect. Only six of the 60 PRCs indicated a negative effect from imidacloprid application. Five of the six were assemblages of mollusks and one was an assemblage of crustaceans. Polychaetes were never negatively affected. The low frequency of a negative effect was likely due to imidacloprid exposures that were limited to low concentrations and short time periods, low toxicological susceptibility to imidacloprid for many taxa, and natural resilience to disturbance and extreme environmental events. The long-term use of imidacloprid to suppress burrowing shrimp in Willapa Bay would likely increase the diversity of benthic invertebrates.

Short-term acclimation in adults does not predict offspring acclimation potential to hypoxia

The prevalence of hypoxic areas in coastal waters is predicted to increase and lead to reduced biodiversity. While the adult stages of many estuarine invertebrates can cope with short periods of hypoxia, it remains unclear whether that ability is present if animals are bred and reared under chronic hypoxia. We firstly investigated the effect of moderate, short-term environmental hypoxia (40% air saturation for one week) on metabolic performance in adults of an estuarine amphipod, and the fitness consequences of prolonged exposure. We then reared the offspring of hypoxia-exposed parents under hypoxia, and assessed their oxyregulatory ability under declining oxygen tensions as juveniles and adults. Adults from the parental generation were able to acclimate their metabolism to hypoxia after one week, employing mechanisms typically associated with prolonged exposure. Their progeny, however, did not develop the adult pattern of respiratory regulation when reared under chronic hypoxia, but instead exhibited a poorer oxyregulatory ability than their parents. We conclude that species apparently hypoxia-tolerant when tested in short-term experiments, could be physiologically compromised as adults if they develop under hypoxia. Consequently, we propose that the increased prevalence of hypoxia in coastal regions will have marked effects in some species currently considered hypoxia tolerant.

Chemical encoding of risk perception and predator detection among estuarine invertebrates

An effective strategy for prey to survive in habitats rich in predators is to avoid being noticed. Thus, prey are under selection pressure to recognize predators and adjust their behavior, which can impact numerous community-wide interactions. Many animals in murky and turbulent aquatic environments rely on waterborne chemical cues. Previous research showed that the mud crab, Panopeus herbstii, recognizes the predatory blue crab, Callinectus sapidus, via a cue in blue crab urine. This cue is strongest if blue crabs recently preyed upon mud crabs. Subsequently, mud crabs suppress their foraging activity, reducing predation by blue crabs. Using NMR spectroscopy- and mass spectrometry-based metabolomics, chemical variation in urine from blue crabs fed different diets was related to prey behavior. We identified the urinary metabolites trigonelline and homarine as components of the cue that mud crabs use to detect blue crabs, with concentrations of each metabolite dependent on the blue crab's diet. At concentrations found naturally in blue crab urine, trigonelline and homarine, alone as well as in a mixture, alerted mud crabs to the presence of blue crabs, leading to decreased foraging by mud crabs. Risk perception by waterborne cues has been widely observed by ecologists, but the molecular nature of these cues has not been previously identified. Metabolomics provides an opportunity to study waterborne cues where other approaches have historically failed, advancing our understanding of the chemical nature of a wide range of ecological interactions.