Time-averaged copper concentrations from continuous exposures predicts pulsed exposure toxicity to the marine diatom, Phaeodactylum tricornutum: importance of uptake and elimination

Intermittent, fluctuating and pulsed contaminant discharges result in organisms receiving highly variable contaminant exposures. Current water quality guidelines are predominantly derived using data from continuous exposure toxicity tests, and most frequently applied by regulators with the assumption that concentrations from a single sampling event will provide a meaningful approach to assessing potential effects. This study investigated the effect of single and multiple (daily) dissolved copper pulses on the marine diatom, Phaeodactylum tricornutum, including measurements of copper uptake and elimination to investigate the toxic mechanism. Copper pulses of between 0.5 and 24 h and continuous exposures with equivalent 72-h time-averaged concentrations (TACs) resulted in similar biomass inhibition of P. tricornutum, with continuous exposures often being marginally more toxic. Rates of cell division generally recovered to control levels within 24 h of the copper pulse removal. Upon resuspension in clean seawater, the extracellular copper per cell decreased rapidly, whereas the intracellular copper per cell decreased slowly. Negligible loss of copper from the total algal biomass indicated that P. tricornutum did not have an effective mechanism for eliminating copper from cells, rather the intracellular copper decreased as a result of dilution by cellular division as the algal growth rate recovered. The measurement of copper uptake after 72-h exposure and kinetics of elimination thereafter suggest that continuous exposures are marginally more toxic to P. tricornutum than pulsed copper exposures with equivalent TACs because slow internalization and saturation of algal membrane transport sites results in less copper uptake into pulse-exposed cells than continuously-exposed cells coupled with dilution of internalized copper via cellular division in the post-exposure period. In the case of P. tricornutum, the results indicate that water quality guidelines for copper based on continuous exposure will be conservative when applied to short-term discharges

Using Bayesian Networks to Predict Risk to Estuary Water Quality and Patterns of Benthic Environmental DNA in Queensland

Predictive modeling can inform natural resource management by representing stressor-response pathways in a logical way and quantifying the effects on selected endpoints. This study demonstrates a risk assessment model using the Bayesian network-relative risk model (BNRRM) approach to predict water quality and; for the first time, eukaryote environmental DNA (eDNA) data as a measure of benthic community structure. Environmental DNA sampling is a technique for biodiversity measurements that involves extracting DNA from environmental samples, amplicon sequencing a targeted gene, in this case the 18s rDNA gene which targets eukaryotes, and matching the sequences to organisms. Using a network of probability distributions, the BN-RRM model predicts risk to water quality objectives and the relative richness of benthic taxa groups in the Noosa, Pine, and Logan estuaries in South East Queensland (SEQ), Australia. The model predicts Dissolved Oxygen more accurately than the Chlorophyll-a water quality endpoint, and photosynthesizing benthos more accurately than heterotrophs. Results of BN-RRM modeling given current inputs indicate that the water quality and benthic assemblages of the Noosa are relatively homogenous across all sub risk regions, and that the Noosa has a 73 – 92 percent probability of achieving water quality objectives, indicating a low relative risk. Conversely, the Middle Logan, Middle Pine, and Lower Pine regions are much less likely to meet objectives (15 – 55 percent probability), indicating a relatively higher risk to water quality in those regions. The benthic community richness patterns associated with risk in the Noosa are high Diatom relative richness and low Green Algae relative richness. The only benthic pattern consistently associated with the relatively higher risk to water quality is high richness of fungi species. The BN-RRM model provides a basis for future predictions and adaptive management at the direction of resource managers

Forest top canopy bacterial communities are influenced by elevation and host tree traits

Background: The phyllosphere microbiome is crucial for plant health and ecosystem functioning. While host species play a determining role in shaping the phyllosphere microbiome, host trees of the same species that are subjected to different environmental conditions can still exhibit large degrees of variation in their microbiome diversity and composition. Whether these intra-specific variations in phyllosphere microbiome diversity and composition can be observed over the broader expanse of forest landscapes remains unclear. In this study, we aim to assess the variation in the top canopy phyllosphere bacterial communities between and within host tree species in the temperate European forests, focusing on Fagus sylvatica (European beech) and Picea abies (Norway spruce).Results: We profiled the bacterial diversity, composition, driving factors, and discriminant taxa in the top canopy phyllosphere of 211 trees in two temperate forests, Veluwe National Parks, the Netherlands and Bavarian Forest National Park, Germany. We found the bacterial communities were primarily shaped by host species, and large variation existed within beech and spruce. While we showed that there was a core microbiome in all tree species examined, community composition varied with elevation, tree diameter at breast height, and leaf-specific traits (e.g., chlorophyll and P content). These driving factors of bacterial community composition also correlated with the relative abundance of specific bacterial families.Conclusions: While our results underscored the importance of host species, we demonstrated a substantial range of variation in phyllosphere bacterial diversity and composition within a host species. Drivers of these variations have implications at both the individual host tree level, where the bacterial communities differed based on tree traits, and at the broader forest landscape level, where drivers like certain highly plastic leaf traits can potentially link forest canopy bacterial community variations to forest ecosystem processes. We eventually showed close associations between forest canopy phyllosphere bacterial communities and host trees exist, and the consistent patterns emerging from these associations are critical for host plant functioning

Invertebrate traits, diversity and the vulnerability of groundwater ecosystems

Funding Information: This manuscript evolved from a workshop titled Trait‐based analyses in groundwater ecology and bioassessment held as part of the 24th International Conference on Subterranean Biology, 20–24th August 2018, University of Aveiro, Portugal. The workshop was supported by the conference organisers and the Macquarie University Species Spectrum Research Centre. Financial support was also provided to M.A.D. by the Portuguese government (Fundação para a Ciência e Tecnologia; FCT) through the research unit UIDB/04085/2020 (CENSE). A.S.P.S.R. was supported by the VILLUM FONDEN (research grant 15471) and by Portuguese National Funds through Fundação para a Ciência e a Tecnologia within the cE3c Unit funding UIDB/00329/2020. S.I.S. acknowledges funding through EU Operational Programme Research, Development and Education No. CZ.02.2.69/0.0/0.0/16_027/0008357, and by the Ministry of Education, Youth and Sports of the Czech Republic [grant number CZ.02.1.01/0.0/0.0/16 025/0007417]. K.L.K. was supported in part by Australian Research Council grant LP190100927. The comments of the Editor, Associate Editor and an anonymous reviewer greatly improved the MS. Open access publishing facilitated by Macquarie University, as part of the Wiley ‐ Macquarie University agreement via the Council of Australian University Librarians. Publisher Copyright: © 2022 The Authors. Functional Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.Groundwater comprises the largest freshwater ecosystem on the planet. It has a distinct regime of extreme, yet stable environmental conditions that have favoured the development of similar morphological and functional traits in the resident invertebrate fauna (stygofauna). The analysis of community traits is increasingly used as an alternative to taxonomy-based assessments of biodiversity, especially for monitoring ecosystem status and linking the functions of organisms to ecological processes, yet it has been rarely applied to stygofauna and groundwater ecosystems. In this paper, we review the variation in functional traits among the invertebrate fauna of this important ecosystem. We focus on the stygofauna and processes of alluvium and fractured rock aquifers that are typified by small voids and fissures that constrain the habitats and environmental conditions. As a first step, we compare trait variability between groundwater and surface water invertebrate communities and then examine the significance of the ranges of these traits to the vulnerability of the ecosystem to change. Fifteen potentially useful functional traits are recognised. Eight of these have narrower ranges (i.e. exhibit fewer states, or attributes, of a particular trait) in groundwater than they do in surface water. Two traits have wider ranges. Our synthesis suggests that the relative stability of groundwater environments has led to low trait variability. The low biomass and low reproductive rate of stygofauna suggest that recovery potential following disturbance is likely to be low. For the purposes of both improved understanding and effective management, further work is needed to document additional functional traits and their states in groundwater fauna, enabling a better understanding of the relationship between response and effect traits in these ecosystems. Read the free Plain Language Summary for this article on the Journal blog.publishersversionpublishe

Ecosystems monitoring powered by environmental genomics: a review of current strategies with an implementation roadmap

A decade after environmental scientists integrated high-throughput sequencing technologies in their toolbox, the genomics-based monitoring of anthropogenic impacts on the biodiversity and functioning of ecosystems is yet to be implemented by regulatory frameworks. Despite the broadly acknowledged potential of environmental genomics to this end, technical limitations and conceptual issues still stand in the way of its broad application by end-users. In addition, the multiplicity of potential implementation strategies may contribute to a perception that the routine application of this methodology is premature or “in development”, hence restraining regulators from binding these tools into legal frameworks. Here, we review recent implementations of environmental genomics-based methods, applied to the biomonitoring of ecosystems. By taking a general overview, without narrowing our perspective to particular habitats or groups of organisms, this paper aims to compare, review and discuss the strengths and limitations of four general implementation strategies of environmental genomics for monitoring: (a) Taxonomy-based analyses focused on identification of known bioindicators or described taxa; (b) De novo bioindicator analyses; (c) Structural community metrics including inferred ecological networks; and (d) Functional community metrics (metagenomics or metatranscriptomics). We emphasise the utility of the three latter strategies to integrate meiofauna and microorganisms that are not traditionally utilised in biomonitoring because of difficult taxonomic identification. Finally, we propose a roadmap for the implementation of environmental genomics into routine monitoring programmes that leverage recent analytical advancements, while pointing out current limitations and future research needs.publishedVersio

Direct and indirect effects of copper-contaminated sediments on the functions of model freshwater ecosystems

Copper is acutely toxic to, and directly affects, primary producers and decomposers, which are key players in essential processes such as the nutrient cycle in freshwater ecosystems. Even though the indirect effects of metals (for example effects due to changes in species interactions) may be more common than direct effects, little is known about the indirect effects of copper on primary producers and decomposers. The effects of copper on phytoplankton, macrophytes, periphyton and organic matter decomposition in an outdoor lentic mesocosm facility were assessed, and links between the responses examined. Copper directly decreased macrophyte growth, subsurface organic matter decomposition, and the potential for high phytoplankton Chlorophyll a concentrations. However, periphyton cover and organic matter decomposition on the surface of the sediment were stimulated by the presence of copper. These latter responses were attributed to indirect effects, due to a reduction in grazing pressure from snails, particularly Physa acuta, in the higher copper-contaminated mesocosms. This permitted the growth of periphyton and other heterotrophs, ultimately increasing decomposition at the sediment surface. The present study demonstrates the pronounced influence indirect effects may have on ecological function, findings that may not be observed in traditional laboratory studies (which utilize single species or simplistic communities).10 page(s

Invertebrate community responses to a particulate - and dissolved - copper exposure in model freshwater ecosystems

Historical contamination has left a legacy of high copper concentrations in the sediments of freshwater ecosystems worldwide. Previous mesocosm studies have focused on dissolved-copper exposures in the overlying waters, which, because of altered exposure pathways, may not accurately predict the effects of copper exposure on invertebrate communities at historically contaminated sites. The present study assessed the effects of copper on the establishment of invertebrate communities within a large outdoor pond mesocosm facility containing environmentally relevant copper-spiked sediments. High particulate copper concentrations (>400mg/kg dry wt) caused a pronounced effect on the benthic community richness, abundance, and structure in the mesocosms, but particulate copper concentrations below 100mg/kg dry weight had no effect. Furthermore, there were no effects of copper on the invertebrate communities within the water column, even in the highest copper treatment. The response of the benthic community to copper was influenced by interspecific interactions, the stage of ecological succession, and interspecies variation in sensitivity to copper. The present study demonstrates the importance of using environmentally realistic exposure scenarios that provide both particulate and dissolved exposure pathways. It also emphasizes that risk assessments for aquatic ecosystems should consider the influence of interspecific interactions and interspecies variation in driving the biotic response to contamination.9 page(s

Improving aquatic ecological assessments

2 page(s

Influence of the choice of physical and chemistry variables on interpreting patterns of sediment contaminants and their relationships with estuarine macrobenthic communities

A primary objective of contaminated sediment risk assessments is to identify if contaminant enrichment is eliciting an ecological response. Using complementary environmental and biotic datasets, we examined five scenarios with respect to: dataset complexity; metal extraction; normalisation of organics; the inclusion/exclusion of acid-volatile sulfide data, and iron and manganese concentrations. Spatial distributions of abiotic variables were examined by principal components analysis, with canonical correspondence analysis used to examine the total and partitioning of biological variation. Metals were the dominant contaminant and explained the largest proportion of variation in the macrobenthic data. Extraction procedure and carbon normalisation of organics had little influence on the overall analysis. Porewater metal data was essential for interpretation, with excess of acid-volatile sulfide over simultaneously extractable metals being a poor surrogate. In the canonical correspondence analyses, the inclusion of Fe/Mn accentuated the covariation between the ecological and contaminant variables. Multimodel comparisons aided interpretation by emphasising specific relationships among environmental variables and their interactions with the biotic data. Furthermore, for future examinations of the described system, the findings can be used to reduce the collection of redundant environmental variables or variables that are poorly correlated with changes in macrobenthic assemblages.14 page(s