Estuarine ecosystems are degraded through anthropogenic development, leading to reduced habitat suitability for biological communities. The Skeena River estuary (British Columbia, Canada) is ...undergoing passive reclamation from historical salmon canneries and pulp mills, while localized disturbances continue at present. To reveal both current impacts and the trajectory of passive reclamation from historical activities, the intertidal mudflat surrounding the longest operating salmon cannery, Cassiar Cannery, within the Skeena estuary was surveyed. Nutrient availability (chlorophyll a concentration/organic matter content), sediment variables (particle size, water content, penetrability, woody debris/macroalgae cover, apparent redox potential discontinuity depth), and infaunal community composition varied spatiotemporally, and suggest that an old dock may be influencing the infaunal community given the abundance of disturbance indicating taxa below the dock. However, with populations of amphipods, mobile polychaetes, and a complex community structure, the mudflat as a whole appears to be relatively healthy. Therefore, cessation of historic activities has allowed for passive reclamation to a reasonably unstressed state, though a threshold of recovery may exist for intertidal mudflats beyond which passive reclamation will not be effective.
•No evidence of log scour impacting the mudflat surrounding Cassiar Cannery.•Old dock structure appears to be impacting the infaunal invertebrate community•Evidence of passive recovery from historical activities (pulp mills and canneries)•Mudflat has not yet fully returned to the state prior to historic activities.
Global climate change is leading to a significant increase in flooding events in many countries. Current practices to prevent damage to downstream urban areas include allowing the flooding of ...upstream agricultural land. Earthworms are ecosystem engineers, but their abundances in arable land are already reduced due to pressure from farming practices. If flooding increases on agricultural land, it is important to understand how earthworms will respond to the dual stresses of flooding and agricultural land use. The earthworm populations under three land uses (pasture, field margin, and crops), across two UK fields, were sampled seasonally over an 18-month period in areas of the fields which flood frequently and areas which flood only rarely. Earthworm abundance in the crop and pasture soils and total earthworm biomass in the crop soils was significantly lower in the frequently flooded areas than in the rarely flooded areas. The relative percentage difference in the populations between the rarely and frequently flooded areas was greater in the crop soils (−59.18% abundance, −63.49% biomass) than the pasture soils (−13.39% abundance, −9.66% biomass). In the margin soils, earthworm abundance was significantly greater in the frequently flooded areas (+140.56%), likely due to higher soil organic matter content and lower bulk density resulting in soil conditions more amenable to earthworms. The findings of this study show that earthworm populations already stressed by the activities associated with arable land use are more susceptible to flooding than populations in pasture fields, suggesting that arable earthworm populations are likely to be increasingly at risk with increased flooding.
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•We surveyed earthworms in frequently and rarely flooded areas of UK fields.•Flooding increased soil organic matter and reduced soil bulk density.•Earthworm abundance in regularly flooded soils was lower than in rarely flooded soils.•Populations decreased due to flooding relatively more in crop than pasture soils.•Earthworm populations in arable soils are susceptible to future flooding.
Earthworms are an integral part of soil ecosystems, especially for their role in soil functions such as organic matter (OM) decomposition and nutrient cycling. Earthworms and microorganisms are ...interdependent, and a considerable portion of the contribution earthworms make to influencing OM fate is through interactions with microorganisms. However, the importance of the earthworm-associated microbiome is not fully understood, because it is difficult to separate the direct influence of the earthworms from the indirect influence of their microbiome. Here, we evaluated an antibiotic-based procedure to suppress the microbiome of individuals of ecologically-contrasting earthworm species (Eisenia fetida, Lumbricus terrestris, Allolobophora chlorotica) as the first step towards soil studies aimed at understanding the importance of the earthworm microbiome for host health and function. Individual earthworms were exposed to antibiotics: cycloheximide (150 μg ml−1), ampicillin (100 μg ml−1), ciprofloxacin (50 μg ml−1), nalidixic acid (50 μg ml−1), and gentamicin (50 μg ml−1) either singly or in a cocktail via culture (96 h) in a semi-solid agar carrier. Compared to the non-antibiotic treated control, the cocktail (for all three species) and ciprofloxacin (for E. fetida and A. chlorotica) treatments significantly reduced (P < 0.05) culturable microbial abundance on nutrient agar and potato dextrose agar. The microbial counts were reduced to below detection (<50 CFU individual−1) for E. fetida and A. chlorotica receiving the cocktail. Illumina 16S rDNA amplicon sequence analysis of culturable L. terrestris -associated bacteria showed that antibiotic treatment influenced community composition revealing putative sensitive (Comomonas, Kosakonia and Sphingobacterium) and insensitive (Aeromonas, Pseudochrobactrum) taxa. Overall, we report a rapid, with minimal earthworm-handling, process of creating suppressed-microbiome E. fetida, A. chlorotica and L. terrestris as a tool to be used in future ecological studies of earthworm microbial interactions affecting host health and function.
•Antibiotic-based method for producing axenic earthworms is evaluated•Contrasting species tested: E. fetida (Ef), L. terrestris (Lt), A. chlorotica (Ac)•Culturable earthworm-associated microbial abundance reduced by antibiotic treatment•High Lt microbiome variability and antibiotic-sensitive and -resistant taxa found•Microbiome-suppressed Ef, Ac and Lt for use in future ecological study
Biochars have been proposed for remediation of metal-contaminated water due to their low cost, high surface area and high sorption capacity for metals. However, there is a lack of understanding over ...how feedstock material and pyrolysis conditions contribute to the metal sorption capacity of biochar. We produced biochars from 10 different organic materials by pyrolysing at 450 °C and a further 10 biochars from cedar wood by pyrolysing at 50 °C intervals (250–700 °C). Batch sorption experiments were conducted to derive the maximum Cu and Zn sorption capacity of each biochar. The results revealed an exponential relationship between Cu and Zn sorption capacity and the feedstock C/N ratio and a sigmoidal relationship between the pyrolysis temperature and the maximum Cu and Zn sorption capacity. FTIR analysis revealed that as temperature increased, the abundance of functional groups reduced. We conclude that the high sorption capacity of high temperature biochars is due to an electrostatic attraction between positively charged Cu and Zn ions and delocalised pi-electrons on the greater surface area of these biochars. These findings demonstrate a method for predicting the maximum sorption capacity of a biochar based on the feedstock C/N ratio and the pyrolysis temperature.
We investigated the impact of managed retreat on mercury (Hg) biogeochemistry at a site subject to diffuse contamination with Hg. We collected sediment cores from an area of land behind a dyke one ...year before and one year after it was intentionally breached. These sediments were compared to those of an adjacent mudflat and a salt marsh. The concentration of total mercury (THg) in the sediment doubled after the dyke was breached due to the deposition of fresh sediment that had a smaller particle size, and higher pH. The concentration of methylmercury (MeHg) was 27% lower in the sediments after the dyke was breached. We conclude that coastal flooding during managed retreat of coastal flood defences at this site has not increased the risk of Hg methylation or bioavailability during the first year. As the sediment becomes vegetated, increased activity of Hg-methylating bacteria may accelerate Hg-methylation rate.
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•We collected cores behind a dyke before and after it was intentionally breached.•Mercury concentration in inundated sediment doubled after the dyke was breached.•Methylmercury concentration decreased in inundated sediment by 27% after breaching.•The freshly deposited sediment adsorbed more Hg and decreased its bioavailability.•Coastal managed retreat did not increase risk of Hg methylation during first year.
Mercury concentration doubled in sediments after coastal flooding but methylmercury concentration deceased.
This study aims to investigate the effect of sieving on ex situ soil respiration (CO
2
flux) measurements from different land use types. We collected soils (0–10 cm) from arable, grassland and ...woodland sites, allocated them to either sieved (4-mm mesh, freshly sieved) or intact core treatments and incubated them in gas-tight jars for 40 days at 10 °C. Headspace gas was collected on days 1, 3, 17, 24, 31 and 38 and CO
2
analysed. Our results showed that sieving (4 mm) did not significantly influence soil respiration measurements, probably because micro aggregates (< 0.25 mm) remain intact after sieving. However, soils collected from grassland soil released more CO
2
compared with those collected from woodland and arable soils, irrespective of sieving treatments. The higher CO
2
from grassland soil compared with woodland and arable soils was attributed to the differences in the water holding capacity and the quantity and stoichiometry of the organic matter between the three soils. We conclude that soils sieved prior to ex situ respiration experiments provide realistic respiration measurements. This finding lends support to soil scientists planning a sampling strategy that better represents the inhomogeneity of field conditions by pooling, homogenising and sieving samples, without fear of obtaining unrepresentative CO
2
flux measurements caused by the disruption of soil architecture.
To assess the risks that contaminated soils pose to the environment properly a greater understanding of how soil biota influence the mobility of metal(loid)s in soils is required.
Lumbricus ...terrestris L. were incubated in three soils contaminated with As, Cu, Pb and Zn. The concentration and speciation of metal(loid)s in pore waters and the mobility and partitioning in casts were compared with earthworm-free soil. Generally the concentrations of water extractable metal(loid)s in earthworm casts were greater than in earthworm-free soil. The impact of the earthworms on concentration and speciation in pore waters was soil and metal specific and could be explained either by earthworm induced changes in soil pH or soluble organic carbon. The mobilisation of metal(loid)s in the environment by earthworm activity may allow for leaching or uptake into biota.
► Earthworms increase the mobility and availability of metals and metalloids in soils. ► We incubated
L. terrestris in three soils contaminated with As, Cu, Pb and Zn. ► Earthworms increased the mobility of As, Cu, Pb and Zn in their casts. ► The mechanisms for this could be explained by changes in pH or organic carbon.
Lumbricus terrestris change the partitioning of metal(loid)s between soil constituents and increase the mobility of metal(loid)s in casts and pore water.
Population assessment techniques for soft-sediment infauna (invertebrates within the substrate) requires excavation of specimens, damaging or killing the specimen and surrounding habitat, while being ...time-consuming and costly. Rapid population assessments of some marine burrowing decapods have been possible by counting burrow openings to estimate abundance, and while they may be used as indicator species, these decapods are not ubiquitous to environments requiring monitoring. Additionally, the presence of other burrowing macrofauna (invertebrates living in the sediment and retained on 1 mm mesh such as clams or large worms) may reduce the efficacy of burrow openings in estimating macrofauna abundance. As such, we assessed mudflats along the north coast of British Columbia, Canada, during summer 2017 to determine if macrofauna abundances could be estimated from burrow openings on the sediment surface in regions of low (n = 1 species) and high (n = 8 species) biodiversity. Abundance could not be estimated at the low diversity sites where only one macrofaunal species created burrows. At the high diversity site, species-specific models estimating abundance from burrow openings could not be constructed; however, the total number of burrow openings observed was useful in estimating total infaunal community abundance. As such, burrow openings may not be an effective tool in assessing species-specific abundances, but may be appropriate to estimate overall community changes.
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