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Novel combinations of climatic conditions due to climate change and prolonged fire seasons have contributed to an increased occurrence of "megafires". Such large-scale fires pose an unknown threat to biodiversity due to the increased extent and severity of burn. Assessments of wildfires often focus on terrestrial ecosystems and effects on aquatic habitats are less documented, particularly in coastal environments. In a novel application of eDNA techniques, we assessed the impacts of the 2019–2020 Australian wildfires on the diversity of estuarine benthic sediment communities in six estuaries in NSW, Australia, before and after the fires. Estuaries differed in area of catchment burnt (0–92%) and amount of vegetative buffer that remained post-fire between burnt areas and waterways. We found greater dissimilarities in the composition and abundance of eukaryotic and bacterial sediment communities in estuaries from burnt catchments with no buffer compared to those with an intact buffer or from unburnt catchments. Shifts in composition in highly burnt catchments were associated with increased concentrations of nutrients, carbon, including fire-derived pyrogenic carbon, and copper, which was representative of multiple highly correlated trace metals. Changes in the relative abundances of certain taxonomic groups, such as sulfate-reducing and nitrifying bacterial groups, in the most impacted estuaries indicate potential consequences for the functioning of sediment communities. These results provide a unique demonstration of the use of eDNA to identify wildfire impacts on ecological communities and emphasize the importance of vegetative buffers in limiting wildfire-associated impacts. [Display omitted] • Estuarine benthic eukaryotic and bacterial community composition changed post-fire. • Greater differences were observed in severely burnt compared to unburnt catchments. • Changes were associated with increased sediment py-C, TOC, Cu and nutrients. • Shifts in certain bacterial groups may have implications for sediment functioning. • EDNA is a useful tool for rapid assessment of wildfire impacts in aquatic systems. [ABSTRACT FROM AUTHOR]

Aim Non-indigenous species pose a significant threat to the environment and to global economies. Predictive and preventative measures are widely considered more effective in curtailing invasions than are eradication or control measures. Of key importance in the prediction of regional invasion risk are the environmental conditions that enable successful establishment. Location We surveyed native and non-indigenous sessile invertebrate diversity in each of two commercial (600–1500 vessels per year) and two recreational estuaries (seven to nine marinas) in New South Wales, Australia. Methods A nested hierarchical design was employed to investigate variation in sessile invertebrate diversity at the scales of site (1–3 km apart) and estuary (40–180 km apart). Settlement plates (15 × 15 cm) were used to sample invertebrates and background heavy metal loads were assessed using bioaccumulation in experimentally deployed oysters. Other physico-chemical variables were monitored monthly. Manipulative experiments were used to test the direct effects of exposure to copper and tributyltin (TBT) antifouling paints on sessile invertebrates. Results Native and non-indigenous species richness differed at various spatial scales, but showed no consistent difference between commercial and recreational estuaries. Instead, individual species distributions were strongly related to metal contamination, temperature, turbidity and pH. In experimental studies, several species (mostly invaders) were more abundant on plates exposed to copper and/or TBT antifouling paints. We found higher levels of copper (and in some instances TBT) in recreational marinas than in commercial harbours. Main conclusions Our results demonstrate the importance of metal pollution and physico-chemical variables in the establishment of invaders in new regions. We have identified several native Australian species that have been exported overseas and suggested mechanisms contributing to their transport and establishment. Combining physico-chemical information about donor and recipient regions with species tolerances could go some way to predicting where future invasions may occur. [ABSTRACT FROM AUTHOR]

Abstract: The global spread of fouling invasive species is continuing despite the use of antifouling biocides. Furthermore, previous evidence suggests that non-indigenous species introduced via hull fouling may be capable of adapting to metal-polluted environments. Using a laboratory based toxicity assay, we investigated tolerance to copper in the non-indigenous bryozoan Watersipora subtorquata from four source populations. Individual colonies were collected from four sites within Port Hacking (Sydney, Australia) and their offspring exposed to a range of copper concentrations. This approach, using a full-sib, split-family design, tests for a genotype by environment (G×E) interaction. Settlement and complete metamorphosis (recruitment) were measured as ecologically relevant endpoints. Larval sizes were also measured for each colony. Successful recruitment was significantly reduced by the highest copper concentration of 80μgL−1. While there was no difference in pollution tolerance between sites, there was a significant G×E interaction, with large variation in the response of colony offspring within sites. Larval size differed significantly both between sites and between colonies and was positively correlated with tolerance. The high level of variation in copper tolerance between colonies suggests that there is considerable potential within populations to adapt to elevated copper levels, as tolerance is a heritable trait. Also, colonies that produce large larvae are more tolerant to copper, suggesting that tolerance may be a direct consequence of larger size. [Copyright &y& Elsevier]

Intermittently Closed and Open Lakes and Lagoons (ICOLLS) are important coastal systems that are periodically separated from the ocean by a sand barrier or a berm. In urban ICOLLs, continuous inputs of organic material and nutrients into coastal lagoons are contributing to eutrophic conditions that, together with natural environmental factors have implications for the resident sediment bacterial communities. We used molecular tools to investigate the ecological communities of four ICOLLs; Narrabeen, Dee Why, Curl Curl and Manly in Sydney, Australia, which have been subjected to increasing pressure from anthropogenic activities over the last century. We used targeted gene sequencing of the prokaryotic 16S ribosomal RNA gene to describe the bacterial diversity and community structure and discuss differences with respect to environmental factors at the ICOLL scale (e.g. size, shape, normalised N loading) and site scale (e.g. water and sediment quality) within each lagoon. Due to differences in hydrological patterns, we expected that sediment bacterial communities would be more heterogenous in displacement-dominated lagoons (Curl Curl and Manly) than the mixing-dominated lagoons (Narrabeen and Dee Why). Interestingly, we did not find strong relationships between the main bacterial groups and distance from the lagoon entrance (used as a proxy for salinity and silt) in the displacement-dominated lagoons. Moreover, we found that α diversity was highest in Narrabeen and Manly lagoons despite differences in lagoon size and shape. Furthermore, while bacterial community structure was similar in Curl Curl and Dee Why, communities in Manly and Narrabeen differed along temperature/TOC and salinity/silt gradients respectively. In Manly lagoon, we found relatively more anaerobic bacteria such as Epsilonbactereota which is involved in the oxidation and reduction of sulfur compounds. Moreover, we identified several bacterial taxa (including sulfur metabolising Chlorobiaceae) related to increasing TOC that could be investigated further as potential indicators of excess enrichment., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Habitat complexity strongly affects the structure and dynamics of ecological communities, with increased complexity often leading to greater species diversity and abundance. However, habitat complexity changes as communities develop, and some species alter their environment to themselves provide habitat for other species. Most experimental studies manipulate basal substrate complexity, and while the importance of complexity likely changes during community development, few studies have examined the temporal dynamics of this variable. We used two experiments to quantify the importance of basal substrate complexity to sessile marine invertebrate community development through space and time. First, we compared effects of substrate complexity at 70 sites across ten estuaries. Sites differed in recruitment and community development rates, and after three months provided spatial variation in community development stage. Second, we tested for effects of substrate complexity at multiple times at a single site. In both experiments, complexity affected marine sessile invertebrate community composition in the early stages of community development when resource availability was high. Effects of complexity diminished through time as the amount of available space (the primary limiting resource) declined. Our work suggests the presence of a bare-space threshold, at which structural complexity of the basal substrate is overwhelmed by secondary biotic complexity. This threshold will be met at different times depending on local recruitment and growth rates and is likely to vary with productivity gradients.

Artificial structures associated with shipping and boating activities provide habitats for a diverse suite of non-indigenous marine species. Little is known about the proportion of invader success in nearby waters that is attributable to these structures. Areas close to piles, wharves and piers are likely to be exposed to increasing levels of propagule pressure, enhancing the recruitment of non-indigenous species. Recruitment of non-indigenous and native marine biofouling taxa were evaluated at different distances from a large commercial shipping pier. Since artificial structures also represent a desirable habitat for fish, how predation on marine invertebrates influences the establishment of non-indigenous and native species was also evaluated. The colonisation of several non-indigenous marine species declined rapidly with distance from the structure. Little evidence was found to suggest that predators have much influence on the colonisation success of marine sessile invertebrate species, non-indigenous or otherwise. It is suggested that propagule pressure, not predation, more strongly predicts establishment success in these biofouling assemblages.

Changes to larval fish assemblages may have far reaching ecological impacts. Correlations between habitat modification, contamination and marine larval fish communities have rarely been assessed in situ. We investigated links between the large-scale distribution of stressors and larval fish assemblages in estuarine environments. Larval fish communities were sampled using a benthic sled within the inner and outer zones of three heavily modified and three relatively unmodified estuaries. Larval abundances were significantly greater in modified estuaries, and there were trends towards greater diversity in these systems. Differences in larval community composition were strongly related to sediment metal levels and reduced seagrass cover. The differences observed were driven by two abundant species, Paedogobius kimurai and Ambassis jacksoniensis, which occurred in large numbers almost exclusively in highly contaminated and pristine locations respectively. These findings suggest that contamination and habitat alteration manifest in substantial differences in the composition of estuarine larval fish assemblages., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Disturbance can affect both the diversity and invasibility of communities. Many field studies have found correlations between diversity and susceptibility to invasion, but if both factors independently respond to disturbance then spurious non-causal relationships may be observed. Here, we show that disturbance can cause a temporal shift in the diversity-invasibility relationship. In a field experiment using sessile marine communities, disturbance strongly affected both diversity and invasion such that they were highly correlated. Disturbance facilitated initial invasion, creating a negative diversity-invasibility relationship when the invader first arrived. Over time, disturbance hindered the persistence of invaders, creating a positive diversity-invasibility relationship. We suggest that temporal changes in the diversity-invasibility relationship may have contributed to the 'invasion paradox', a term for the contrasting patterns of experimental and observational studies of the diversity-invasibility relationship., (© 2010 Blackwell Publishing Ltd/CNRS.)