Key Trophic Groups Research Articles

Environmental DNA for assessing impact and recovery of aquatic communities in an invaded mountain lake

Beaulieu J, Yates MC, Astorg L, Trépanier-Leroux D, Jeon H, Rudko SP, Humphries S, Fraser DJ, Cristescu ME, Derry AM. 2024. Environmental DNA for assessing impact and recovery of aquatic communities in an invaded mountain lake. Lake Reserv Manage. 40:111–131. The eradication of invasive species and associated side effects that influence the reestablishment of biological communities is a major challenge for conservation management of invaded ecosystems. We present a before-and-after-disturbance whole lake manipulation study from a high-elevation mountain lake in which we applied a 2-pronged approach to environmental DNA (eDNA) for assessing (1) impact and recovery of aquatic communities to the chemical eradication of invasive brook trout (Salvelinus fontinalis) and (2) the success of chemical eradication of the invasive fish. Using 18S and cytochrome oxidase I (COI) eDNA metabarcoding, we contribute to a paucity of literature that has comprehensively addressed nontarget effects of rotenone for invasive fish eradication on aquatic communities. We found that key trophic groups (phytoplankton, fungi, zooplankton, and macroinvertebrates) changed in community composition in response to rotenone applications. Fungi and macroinvertebrates, but not zooplankton and phytoplankton, reverted back toward pre-rotenone communities over the time scale of 2 yr. However, COI failed to detect several key species for food web reestablishment that were detected using physical specimen collection, likely due to low primer efficiency. We also found that quantitative polymerase chain reaction (qPCR), using species-specific primers, was effective for detecting brook trout presence/absence, although strong eDNA signals likely produced from carcasses in the ecosystem limited the utility of eDNA immediately following rotenone treatment. We provide specific recommendations for lake managers for the future application of eDNA approaches to monitor invasive fish eradication efforts and nontarget community effects for lake ecosystem restoration.

Macrobenthos in the estuary of a typical «salmon» river of Sakhalin Island (on example of the Manuy River)

Species composition, structure, density and biomass of macrobenthos in the estuary of the Manuy River are described, its main communities are defined and their trophic characteristics, production, and distribution along the river channel are determined on the materials collected in July 2021. Three main biotopic zones of the estuary are identified by their hydrological features and parameters of macrobenthos: the river mouth, the lower estuary, and the upper estuary. Bilateral structure of salinity with 0.8–5.0 psu in the upper layer and > 27 psu near the bottom was observed in the lower estuary, whereas the upper estuarine zone was filled mostly by oligohaline water (0.8–1.6 psu), with only a thin refugial layer of the seawater (23.1 psu) at the depth of 0.9 m. In total, 24 species of benthic invertebrates and cyclostomes were presented in the macrobenthos. The species richness varied insignificantly across the estuary, from 4 species/section in its upper part to 9 species/section in the lower part, with lowered richness at the border between the lower and the upper estuarine zones, that corresponded to the theory of critical salinity. The density of macrobenthos distribution decreased from the river mouth to the boundary between the lower and upper zones (from 808.0 ± 162.0 ind./m2 to 16.0±2.8 ind./m2), then increased sharply in the upper estuary (up to 1384 ± 160 ind./m2). The total biomass had two peaks: in the lower estuary (4.381 ± 0.589 g/m2) and in the upper estuary (up to 28.950 g/m2), with the minimum of 0.076 ± 0.015 g/m2 between. The boundary between the meso-, polyhaline lower estuary and the oligohaline upper estuary had the width of several hundred meters. Four benthic communities were identified by various methods of cluster and ordination analysis, regardless of the method: two communities in the upper estuary (communities of Eogammarus kygi and Neomysis awatschensis), one community in the lower estuary (community of Hediste japonica) and the community of Haustorioides at the river mouth. Gathering detritivores formed the basis of biomass and macrobenthic production at the river mouth; collecting detritophages — sestonophages were the most significant in the lower estuary; while three key trophic groups were presented in the upper estuary: 1) collecting detritivores — macrogrinders — scavengers, 2) collecting detritivores, and 3) ground feeders — collecting detritivores. Daily production of macrobenthos was low at the river mouth and in the lower part of the lower estuary but increased in its upper part and in the upper estuary.

Size Shapes the Active Microbiome of Methanogenic Granules, Corroborating a Biofilm Life Cycle.

Methanogenic archaea are key players in cycling organic matter in nature but also in engineered waste treatment systems, where they generate methane, which can be used as a renewable energy source. In such systems in the built environment, complex methanogenic consortia are known to aggregate into highly organized, spherical granular biofilms comprising the interdependent microbial trophic groups mediating the successive stages of the anaerobic digestion (AD) process. This study separated methanogenic granules into a range of discrete size fractions, hypothesizing different biofilm growth stages, and separately supplied each with specific substrates to stimulate the activity of key AD trophic groups, including syntrophic acid oxidizers and methanogens. Rates of specific methanogenic activity were measured, and amplicon sequencing of 16S rRNA gene transcripts was used to resolve phylotranscriptomes across the series of size fractions. Increased rates of methane production were observed in each of the size fractions when hydrogen was supplied as the substrate compared with those of volatile fatty acids (acetate, propionate, and butyrate). This was connected to a shift toward hydrogenotrophic methanogenesis dominated by Methanobacterium and Methanolinea Interestingly, the specific active microbiomes measured in this way indicated that size was significantly more important than substrate in driving the structure of the active community in granules. Multivariate integration studywise discriminant analysis identified 56 genera shaping changes in the active community across both substrate and size. Half of those were found to be upregulated in the medium-sized granules, which were also the most active and potentially of the most important size, or life stage, for precision management of AD systems.IMPORTANCE Biological wastewater conversion processes collectively constitute one of the single biggest worldwide applications of microbial communities. There is an obvious requirement, therefore, to study the microbial systems central to the success of such technologies. Methanogenic granules, in particular, are architecturally fascinating biofilms that facilitate highly organized cooperation within the metabolic network of the anaerobic digestion (AD) process and, thus, are especially intriguing model systems for microbial ecology. This study, in a way not previously reported, provoked syntrophic and methanogenic activity and the structure of the microbial community, using specific substrates targeting the key trophic groups in AD. Unexpectedly, granule size more strongly than substrate shaped the active portion of the microbial community. Importantly, the findings suggest the size, or age, of granules inherently shapes the active microbiome linked to a life cycle. This provides exciting insights into the function of, and the potential for additional modeling of biofilm development in, methanogenic granules.

Measuring the long-term success of small-scale marine protected areas in a Philippine reef fishery

Tropical coral reefs are subject to multiple pressures from both natural and anthropogenic sources. These pressures have caused widespread declines in reef health, resulting in the increased use of spatial management tools such as marine protected areas (MPAs). MPAs have proven generally effective if well designed and enforced, but there are limited long-term studies investigating how the presence of small-scale MPAs affects fish populations and reef communities. Using a 12-year time series, we found that small-scale (10–50 ha) community-managed MPAs along the Danajon Bank of the Philippines preserved average fish biomass within their boundaries over time relative to surrounding fished reefs. Unprotected areas are, however, showing significant long-term biomass decline. MPAs were also found to preserve more key trophic groups and larger-bodied commercially targeted reef fish families. Fish biomass of piscivore, scavenger and invertivore trophic groups inside individual MPAs is, however, still declining at a similar rate as outside. Surprisingly, long-term benthic cover and growth form composition were not significantly affected overall by MPA presence, despite the sporadic use of highly destructive dynamite fishing in this region. Coral cover has remained historically low (21–28%) throughout the study, following widespread bleaching mortality. While management tempered overall abundance declines, we found that irrespective of MPA presence, there was a generalised decline of both large- and small-bodied fish size groups across the study region, most steeply within the 20–30 cm length fish, and a shift towards proportionally higher abundances of small (5–10 cm) fish. This indicates a combination of over-exploitation, inadequate MPA size and coverage for larger fish, and the lingering effects of the 1998 bleaching event. Generalised shifts in body size and trophic structure reported here could lead to future reductions in fishery productivity and stability and will be further exacerbated unless broader fishery regulations and enforcement is instated.

Inglés

This study identifed and quantifed microbial populations in cattle manure slurry, responsible for anaerobic degradation of kitchen waste using activity tests and Most Probable Number for key trophic groups in the process. Hydrolytic, acidogenic, acetogenic, specifc methanogenic acetoclastic and hydrogenotrophic activities were evaluated using as model substrates starch, glucose, propionate-butyrate mix, acetate and formate, respectively. Anaerobic digestion from kitchen waste was developed for 35 days in batch reactors of 50mL containing an inoculums/substrate ratio of 3. Samples were taken from digesters every 7 days to evaluate microbial populations by counting metabolic groups. This study demonstrates that there is an association between biomass activity and population of trophic groups related. Additionally, CMS is an inoculum with high quality to start-up the anaerobic process with kitchen waste. On the other side, MA/FB ratio and MA/SRB ratio are important microbial parameters to evaluate performance of reactor. Finally, AD from kitchen waste reached a yield coeffcient of 0.41m3 CH4/kgVS using cattle manure sludge as inoculum. Keywords: trophic groups, metabolic groups, kitchen waste, cattle manure slurry, MPN, microbial activities.

Interannual variability in the Northern California Current food web structure: Changes in energy flow pathways and the role of forage fish, euphausiids, and jellyfish

The Northern California Current (NCC) is a seasonally productive and open ecosystem. It is home to both a diverse endemic community and to seasonally transient species. Productivity and food web structure vary seasonally, interannually, and decadally due to variability in coastal upwelling, climate-scale physical processes, and the migratory species entering the system. The composition of the pelagic community varies between years, including changes to mid-trophic level groups that represent alternate energy-transfer pathways between lower and upper trophic levels (forage fishes, euphausiids, jellyfish). Multiple data sets, including annual spring and summer mesoscale surveys of the zooplankton, pelagic fish, and seabird communities, were used to infer NCC trophic network arrangements and develop end-to-end models for each of the 2003–2007 upwelling seasons. Each model was used to quantify the interannual variability in energy-transfer efficiency from bottom to top trophic levels. When each model was driven under an identical nutrient input rate, substantial differences in the energy available to each functional group were evident. Scenario analyses were used to examine the roles of forage fishes, euphausiids, and jellyfish (small gelatinous zooplankton and large carnivorous jellyfish) as alternate energy transfer pathways. Euphausiids were the more important energy transfer pathway; a large proportion of the lower trophic production consumed was transferred to higher trophic levels. In contrast, jellyfish acted as a production loss pathway; little of the production consumed was passed upwards. Analysis of the range of ecosystem states observed interannually and understanding system sensitivity to variability among key trophic groups improves our ability to predict NCC ecosystem response to short- and long-term environmental change.

Methanogenic community development in anaerobic granular bioreactors treating trichloroethylene (TCE)-contaminated wastewater at 37 °C and 15 °C

Four expanded granular sludge bed (EGSB) bioreactors were seeded with a mesophilically-grown granular sludge and operated in duplicate for mesophilic (37 °C; R1 & R2) and low- (15°; R3 & R4) temperature treatment of a synthetic volatile fatty acid (VFA) based wastewater (3 kg COD m −3 d −1) with one of each pair (R1 & R3) supplemented with increasing concentrations of trichloroethylene (TCE; 10, 20, 40, 60 mg l −1) and one acting as a control. Bioreactor performance was evaluated by % COD removal efficiency and % biogas methane (CH 4) content. Quantitative Polymerase Chain Reaction (qPCR) was used to investigate the methanogenic community composition and dynamics in the bioreactors during the trial, while specific methanogenic activity (SMA) and toxicity assays were utilized to investigate the activity and TCE/dichloroethylene (DCE) toxicity thresholds of key trophic groups, respectively. At both 37 °C and 15 °C, TCE levels of 60 mg l −1 resulted in the decline of % COD removal efficiencies to 29% (Day 235) and 37% (Day 238), respectively, and in % biogas CH 4 to 54% (Day 235) and 5% (Day 238), respectively. Despite the inhibitory effect of TCE on the anaerobic digestion process, the main drivers influencing methanogenic community development, as determined by qPCR and Non-metric multidimensional scaling analysis, were (i) wastewater composition and (ii) operating temperature. At the apical TCE concentration both SMA and qPCR of methanogenic archaea suggested that acetoclastic methanogens were somewhat inhibited by the presence of TCE and/or its degradation derivatives, while competition by dechlorinating organisms may have limited the availability of H 2 for hydrogenotrophic methanogenesis. In addition, there appeared to be an inverse correlation between SMA levels and TCE tolerance, a finding that was supported by the analysis of the inhibitory effect of TCE on two additional biomass sources. The results indicate that low-temperature anaerobic digestion is a feasible approach for the treatment of TCE-containing wastewater.

Trophic network model of the Northern Adriatic Sea: Analysis of an exploited and eutrophic ecosystem

A quantitative model of the trophic network of Northern Adriatic Sea marine ecosystem during the 1990s has been constructed, with the goal of analysing its trophic structure, identifying the key trophic groups and assessing the anthropogenic impacts on the ecosystem using the Ecopath modelling protocol. The Northern Adriatic Sea is an eutrophic, shallow basin, and one of the most heavily fished areas in the Mediterranean Sea. The network aggregation into discrete trophic levels sensu Lindeman shows that low trophic levels dominate biomass and energy flows, with 40% of the total system throughput flowing out from trophic level 2. Instead, upper trophic levels appear bottom-up controlled, highly depleted and not exerting any control on the trophic network, as shown by mixed trophic impact-based analyses. Microbial loop is comparable to grazing with respect to the magnitude of flows involved, as 66% of the trophic network flows originate from detritus, which is mainly consumed by bacteria. Key trophic groups are plankton groups, macro-crustaceans and detritus, and other r-selected organisms like squids and small pelagics, which have a great influence on the ecosystem. In particular, zooplankton acts as a bottleneck for energy flows, limiting the energy from the low trophic levels effectively reaching the upper food web. The high pelagic production caused by eutrophication sustains high fishery landings and impressive discard quantities, as well as the benthic compartment. Overall, the ecosystem appears quite productive and in a stressed and developmental status. Model results and comparisons with few existing historical data suggest that the low maturity and stressed state of the Northern Adriatic Sea are not only due to natural characteristics, but mainly to anthropogenic pressures.

Bait attraction affects the performance of remote underwater video stations in assessment of demersal fish community structure

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 350:245-254 (2007) - DOI: https://doi.org/10.3354/meps07192 Bait attraction affects the performance of remote underwater video stations in assessment of demersal fish community structure Euan S. Harvey1,4,*, Mike Cappo2, James J. Butler1, Norm Hall3, Gary A. Kendrick1,4 1School of Plant Biology (Botany M090), University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia 2Australian Institute of Marine Science, PMB 3, Townsville MC, Queensland 4810, Australia 3Centre for Fish and Fisheries Research, School of Biological Sciences and Biotechnology, Murdoch University, Murdoch, Western Australia 6150, Australia 4CRC for Coastal Zone, Estuary and Waterway Management, School of Plant Biology (Botany M090), University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia *Email: euanh@cyllene.uwa.edu.au ABSTRACT: Discriminating marine fish assemblages at broad scales can be difficult because of heterogeneity within their habitats, variability in patterns of behaviour and abundance of fish between habitats, and sampling biases in extractive fishing techniques when used across a range of habitats. Remote underwater video stations have recently been developed to help overcome these problems, but the use of bait as an attractant raises questions about bias towards scavengers and predators in samples of fish communities. We compared the ability of baited and unbaited underwater video stations to discriminate between fish assemblages inhabiting distinct benthic habitats in temperate and tropical continental shelf waters in Australia, to help test whether the bait attracted predatory and scavenging species to the video in disproportionate numbers in comparison to other trophic groups, such as herbivores. Data from baited video cameras displayed a clearer discrimination in constrained canonical analysis of principal coordinates of fish assemblages between marine habitats in both tropical and temperate environments. Analysis of the key trophic groups indicated that bait attracted greater numbers of predatory and scavenging species without decreasing the abundances of herbivorous or omnivorous fishes. There was greater similarity between replicate samples from baited video within habitats, implying that the use of bait will provide better statistical power to detect spatial and temporal changes in the structure of fish assemblages and the relative abundances of individual species within them. KEY WORDS: Demersal fish assemblages · Underwater video stations · Bait · Remote sampling Full text in pdf format PreviousNextCite this article as: Harvey ES, Cappo M, Butler JJ, Hall N, Kendrick GA (2007) Bait attraction affects the performance of remote underwater video stations in assessment of demersal fish community structure. Mar Ecol Prog Ser 350:245-254. https://doi.org/10.3354/meps07192Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 350. Online publication date: November 22, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Low-temperature anaerobic biological treatment of toluene-containing wastewater

Two expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactors, R1 and R2, were operated at 15 °C for the treatment of toluene-contaminated volatile fatty acid-based wastewater. The seed inoculum and the R1 reactor were unexposed to toluene, prior to and during the trial, respectively. Both reactors were operated at a hydraulic retention time of 24 h at applied organic loading rates of 0.71–1.43 kg chemical oxygen demand (COD) m −3 d −1. Toluene was supplemented to the R2 influent at concentrations of 5–104 mg toluene l −1 (solubilised in ethanol). Bioreactor performance was evaluated by COD and toluene removal efficiency, and the methane content of biogas (%). Specific methanogenic activity and toxicity assays were employed to investigate the activity and toluene toxicity thresholds of key trophic groups, respectively, within the seed and reactor biomass samples. COD and toluene removal efficiencies of 70–90% and 55–99%, respectively, were achieved during the 630-d trial. Metabolic assays suggested that a psychrotolerant H 2/CO 2-utilizing methanogenic community developed in the toluene-degrading biomass. The results indicate the viability of low-temperature anaerobic digestion for the treatment of wastewater containing toluene.

Low-temperature anaerobic biological treatment of solvent-containing pharmaceutical wastewater

Low-temperature or psychrophilic (<20 °C) anaerobic digestion (PAD) has recently been demonstrated as a cost-effective option for the treatment of a range of wastewater categories. The aim of this work was 2-fold: (1) to screen three anaerobic sludges, obtained from full-scale reactors, with respect to suitability for PAD of pharmaceutical-like, solvent-contaminated wastewater; (2) to assess the feasibility of PAD of this wastewater category. Toxicity thresholds of key trophic groups within three candidate biomass samples were assessed against solvents prevalent in pharmaceutical wastewaters (propanol, methanol and acetone). Specific methanogenic activity (SMA) assays indicated that the metabolic optimum of each candidate biomass was within the mesophilic range. One biomass sample exhibited higher SMA assays than the other candidate samples and was also the sample least methanogenically inhibited by the addition of solvents to batch cultures. This sludge was selected as the biomass of choice for laboratory-scale trials. Two identical expanded granular sludge bed (EGSB)-based anaerobic reactors were used for the treatment of solvent-contaminated wastewater at 15 °C, and at applied organic loading rates (OLRs) of 5–20 kg chemical oxygen demand (COD) m −3 d −1. COD removal efficiencies of 60–70% were achieved during the 450 day trial. In addition, SMA assays carried out at the conclusion of the trial indicated the development of a putatively psychrophilic hydrogenotrophic methanogenic community.