Total Abundance Research Articles

Role of Bioavailability in Compost Maturity During Aerobic Composting of Chicken Manure

To evaluate the effects of the type and proportion of bulking agents on compost maturity, chicken manure feedstock (J) was selected as the main raw material for aerobic composting, and wood chips (M), straw (S), and cornmeal (Y) were used as bulking agents. The ratios of chicken manure feedstock to the three bulking agents were set at 1:3, 1:1, and 3:1, respectively. The compost mixture composed of wood chips (M) and feedstock (J) in a 1:1 ratio exhibited the highest temperature (75 °C). The treatment with a bulking-agent-to-feedstock ratio of 3:1 exhibited the lowest temperature (52 °C) and the longest high-temperature period (about 10 days). Moreover, the compost mixture composed of wood chips (M) and feedstock (J) in a 3:1 ratio exhibited the highest seed germination index (1.32), while the GI values for all cornmeal treatments did not meet the standard requirements (0.4). The predominant microorganisms in all three treatments included Firmicutes, Bacteroidetes, Actinobacteria, and Proteobacteria. The total carbon transformation-related microorganism abundance in MJ31, SJ31, and YJ31 was 1.65%, 10.69%, and 3%, respectively. Further analysis showed that the bioavailability of feedstock was strongly correlated with compost maturity. The treatment with a bulking-agent-to-feedstock ratio of 3:1, with the highest GI, also exhibited the highest bioavailability. These results can guide the selection of the appropriate bulking agent and the optimal bulking-agent-to-feedstock ratio, offering a new direction for the optimization of the composting process.

Recurrent Swarms of Planktonic Shrimp Luciferidae De Haan, 1849 (Order: Decapoda) in the Neritic Waters of Tamil Nadu, Southeast Coast of India

ABSTRACTLuciferidae (Decapoda) are an important component of mesozooplankton in pelagic food webs. This study investigated the spatiotemporal distribution and frequency of Luciferidae swarms along the Tamil Nadu coast, as observed during coastal monitoring cruises conducted between 2019 and 2022. Data were collected on various hydrobiological factors, including surface water temperature, salinity, chlorophyll a, zooplankton biomass, and the abundance of other mesozooplankton (such as copepods, cladocerans, and others) across eight locations in the coastal waters of Tamil Nadu, India. Salinity values were generally low (< 30 PSU) throughout the study period, except in September 2019. Microscopic analysis identified Belzebub hanseni Nobili, 1905, as the only organism responsible for swarm formation, with its occurrence peaking in January 2022. During this period, B. hanseni reached a maximum abundance of 3294 ind. m−3 for adults and 4056 ind. m−3 for larvae, together contributing approximately 27% of the total zooplankton abundance. Swarms of B. hanseni were observed a total of seven times over the course of the study, correlating with periods of low sea surface temperature and high food availability. Pearson's correlation analysis revealed a significant relationship between the abundance of copepods and B. hanseni (r = 0.84; p < 0.001), suggesting that both groups may be influenced by similar environmental factors, such as physical transport, food availability, and favorable conditions. This study indicates that the frequent swarming of B. hanseni in the nearshore waters of the Tamil Nadu coast is largely driven by food availability and optimal environmental conditions, including water temperature and monsoonal influences. The findings also suggest that geographical features, such as mangrove habitats, may contribute to the occurrence of B. hanseni swarms in this region.

The biogeography of gastrointestinal mucosal microbiota of beef cattle at harvest

IntroductionThe gastrointestinal microbiota profoundly influences the health and productivity of animals. This study aimed to characterize microbial community structures of the mouth, gastrointestinal tract (GIT), and feces of cattle.MethodsSamples were collected from 18 Akaushi crossbred steers at harvest from multiple locations, including the oral cavity, rumen, abomasum, duodenum, jejunum, ileum, cecum, spiral colon, distal colon, and feces. These cattle were raised without exposure to antimicrobial drugs or hormone implants. Total microbial abundance was assessed using qPCR targeting the V3–V4 region of the 16S rRNA gene, and microbial community composition was evaluated through 16S rRNA gene sequencing.ResultsTotal microbial abundance was lesser in the small intestine than in other GIT regions (p ≤ 0.05). Additionally, microbial communities in the small intestine had lower richness and diversity than other regions (p ≤ 0.05). Microbial community compositions were measurably different along the GIT, with greater relatedness in adjacent GIT sections when progressing from oral to aboral locations. Firmicutes, Bacteroidota, and Actinobacteria were the dominant phyla in all samples. However, variations in composition were evident at lower taxonomic levels within these dominant phyla among samples from different regions. Genera previously associated with healthy gut microbiome communities were observed in low abundance across GIT regions. Taxa historically associated with liver abscesses (e.g., Fusobacterium and Trueperella) were detected in low abundance (≤0.02% relative abundance) throughout the GIT. In contrast, Bacteroides, which recently has been identified as a dominant feature in many liver abscesses, was observed in greater relative abundance (5.2% on average) in the hindgut.DiscussionThis study provides an in-depth evaluation of the GIT of harvest-ready Akaushi crossbred cattle of varying growth rates. Clear differences exist in the abundance and composition of microbial populations at different points of the GIT. Unfortunately, no single GIT location can adequately represent the microbial communities of the entire GIT, which has important implications for future research. Additionally, examining microbiome data only at the phylum level likely oversimplifies important complexities of the microbial community structures, and investigations of lower taxonomic ranks should be included.

Composition and dynamics of macroinvertebrates community in relation to physicochemical parameters of hydrogeologically connected wetlands in Abbay River basin, Ethiopia.

Assessing the macroinvertebrate assemblage in relation to physicochemical parameters can provide insight into the ecological state of aquatic environments. Therefore, this study aimed to assess macroinvertebrate assemblage of hydrogeologically connected wetlands in relation to physicochemical water quality parameters. Data were collected between June 2022 and April 2023 from twelve purposively selected sampling sites following established procedures. A total of 1,211 macroinvertebrates were collected from 18 orders and 44 families. The majority (72.83%) are generally pollution-tolerant families of the order Hemiptera, Odonata, Coleoptera and Diptera. There was significant spatio-temporal variation (P < 0.05, One-way ANOVA) in total macroinvertebrate abundance and bioindices. There were more individual macroinvertebrates collected during the dry season. The CCA and correlation analysis indicated that the physicochemical parameters had an effect on the distribution and abundance of macroinvertebrates. The size of the wetlands andthe intensity of anthropogenic interventionmight also result difference in macroinvertebrate abundance across the wetlands. The higher nutrient concentrations, the low DO level, the higher abundance of tolerant taxa and the medium Shannon_Hvalue (range: 2.13 to 2.68) all indicate the wetlands' poor ecological status. Therefore, regular water quality monitoring, identification of the macroinvertebrate at the lower taxonomic level and the development of macroinvertebratebased multimetric indices are recommended for their sustainable management.

Diversity of Mosquitoes (Diptera: Culicidae) in Urban Areas of the Federal District, 2014-2018

Objective: To describe and analyze the diversity of mosquitoes in urban areas of the Federal District (DF), Brazil, the types of breeding sites, and the relationships between climatic variables and the abundance of the main vector species. Theoretical Framework: The potential distribution, endemicity, emergence, and re-emergence of pathogens transmitted by mosquitoes is regulated by fluctuations in potential vector Culicidae communities. Studies on the diversity of culicids are important to understand the ecological relationships between species and the environment they occupy. However, information on diversity patterns and the structure of the culicid fauna in the DF is still scarce and dispersed in the literature. Method: Mosquito larvae collected and identified in urban areas of the DF between January 2014 and December 2018 were evaluated for abundance, constancy, dispersal capacity, similarity of specific composition among Administrative Regions, and abundance by type of breeding site. The influence of macroclimatic factors was verified using the Spearman coefficient. Results and Discussion: The results revealed 12 species of mosquitoes, with higher abundance, constancy, and dispersion among Aedes aegypti and Culex quinquefasciatus. Precipitation and relative humidity were the abiotic factors that most influenced total abundance, with similar results recorded in other studies. Research Implications: Understanding the structure of the Culicidae fauna, and in particular, the identification of local parameters that shape these communities are important for adequate approaches to control vector species. Originality/Value: Shows the benefits that disease-vectoring mosquito species find in the Federal District.

Field Trials of Wild Entomopathogenic Fungi and Commercial Steinernema carpocapsae on the Large Pine Weevil (Hylobius abietis [L.]) Including an Assessment of Non-Target Effects

The large pine weevil (Hylobius abietis L.) is a major pest in European and Asian coniferous forests, particularly in managed plantations where clear-felling practices create ideal conditions for its population growth. Traditional management practices involving synthetic insecticides have limited efficacy in terms of reducing pest populations and pose environmental risks. This study evaluated the effectiveness of a wild entomopathogenic fungus (EPF) and the commercial entomopathogenic nematode Steinernema carpocapsae (EPN) as biological control agents (BCAs) against H. abietis in clear-felled spruce plantations in Wales and Scotland. Field trials used a randomised block design with three treatments (EPN full dose, EPF full dose and a combination of EPF+EPN at half doses each) compared to a control. Emergence trapping and destructive sampling were employed to assess treatment efficacy. All treatments significantly reduced weevil emergence, with the mixed treatment showing the greatest impact. Destructive sampling revealed strong associations between treatment type and infection outcomes in H. abietis, with a small but significant relationship between weevil developmental stages and infection types. Importantly, the treatments had no significant impact on the total abundance or taxon richness of non-target invertebrates. These findings suggest that wild EPFs alone and combined with EPNs are effective and environmentally safe alternatives to synthetic insecticides for managing H. abietis populations in managed forests.

Regional Biomes outperform broader spatial units in capturing biodiversity responses to land‐use change

Biogeographic context, such as biome type, has a critical influence on ecological resilience, as climatic and environmental conditions impact how communities respond to anthropogenic threats. For example, land‐use change causes a greater loss of biodiversity in tropical biomes compared to temperate biomes. Furthermore, the nature of threats impacting ecosystems varies geographically. Therefore, monitoring the state of biodiversity at a high spatial resolution is crucial to capture variation in threat–responses caused by biogeographical context. However such fine‐scale ecological data collection could be prohibitively resource intensive. In this study, we aim to find the spatial scale that could best capture variation in community‐level threat responses whilst keeping data collection requirements feasible. Using a database of biodiversity records with extensive global coverage, we modelled species richness and total abundance (the responses) across land‐use types (reflecting threats), considering three different spatial scales: biomes, biogeographical realms, and regional biomes (the interaction between realm and biome). We then modelled data from three highly sampled biomes to ask how responses to threat differ between regional biomes and taxonomic group. We found strong support for regional biomes in explaining variation in species richness and total abundance compared to biomes or realms alone. Our biome case studies demonstrate that there is variation in magnitude and direction of threat responses across both regional biomes and taxonomic group, although the interpretation is limited by sampling bias in the literature. All groups in tropical forest showed a consistently negative response, whilst many taxon‐regional biome groups showed no clear response to threat in temperate forest and tropical grassland. Our results provide the first empirical evidence that the taxon‐regional biome unit has potential as a reasonable spatial unit for monitoring how ecological communities respond to threats and designing effective conservation interventions to bend the curve on biodiversity loss.

Seasonal changes in the structure of the bog taxocene of Collembola of the «Zalizna voda» forest park (Lviv)

An analysis of the taxonomic and ecological structure of the bog taxocene of collembola of the «Zalizna voda» forest park in the city of Lviv in different seasons of the year was carried out. 36 species of collembola belonging to 24 genera and 12 families were found in the investigated urboecosystem. It has been established that a characteristic feature of the studied bog collembolan taxocene is its great species diversity, super-specialization and super-dominance, which are preserved in different seasons of the year. It was found that the point alpha-diversity in different seasons of the year varies from 6 to 16 species, and the coenotic alpha-diversity - 23-27 species, which indicates a large capacity of the soil environment for collembola in this bog urboecosystem, compared to the natural bog ecosystems of Roztochchia region. The investigated taxocene of collembola are also characterized by high population density in different seasons of the year, from 11.34 to 15.48 thousand inhabitants/m2. In certain seasons of the year, from 3 to 5 mass (dominant) species were established, which account for 66.4-83.6% of the collembolan population. Over the entire period of research, the invasive species D. trispinata was superdominant, the share of which in certain seasons of the year was 57.4-68.6% of the population. The analysis of the ecological structure showed that in terms of species richness and abundance, it is dominated by complexes of hygro-mesophilic (11 species, 76.8% of the total abundance), hygrophilic (9, 11.3%) and mesophilic (9, 7.7%) springtails. The studied taxocene includes seven biotope groups of species. Among them, representatives from the group of meadow-bog (65.4% of the population), erytopic (10%), forest and forest-meadow (18% in total) species of Collembola predominate in terms of relative abundance. It has been established that a super-specialized bog taxocene of Collembola is formed in the studied ecosystem, where the share of specialized species to this bog edaphotope (meadow-bog, bog and arroundwater) is more than 70% of the total abundance.

Prevalence of invasive fish and plants in the winter diet of the rakali (Hydromys chrysogaster)

AbstractUnderstanding the dietary components of a species can help reveal complex ecological interactions within an ecosystem. We analysed the diet of a native semi‐aquatic predator, the rakali (Hydromys chrysogaster), to investigate its reported preference for invasive species in a regulated freshwater system. We used faecal metabarcoding analysis to identify key dietary items consumed during winter in the Yanco Creek System of southern New South Wales. While rakali did not display a significant difference in the consumption of invasive and native fish, 79.5% of total fish relative read abundance were invasive. The common carp (Cyprinus carpio) comprised 16.8% of the total diet relative read abundance and was present in 78.6% of samples. Plant matter was present in all samples and over half of the total relative read abundance of the diet. The prevalence of plants in the winter diet of rakali indicates that they are an important dietary supplement when other resources are limited. We show that the prevalence of invasive fish consumed by rakali is likely a result of their greater abundance in the system, rather than a direct preference. Further research is needed to determine the extent to which rakali can control invasive prey populations.

Weichang' an pill alleviates functional dyspepsia through modulating brain-gut peptides and gut microbiota.

To evaluate the effect of Weichang'an pill (, WCAP) on functional dyspepsia (FD) and explore its regulation of brain-gut peptides (BGPs) and gut microbiota balance as a potential treatment mechanism. The "0 ℃ saline gavage + irregular feeding and tail clamp" method was used to establish the FD rat model, excluding the normal group. The successfully established FD rat models were randomly divided into the model group and the WCAP1 (WC1), WCAP2 (WC2), WCAP3 (WC3), WCAP4 (WC4), WCAP5 (WC5), and Domperidone (Dom) groups (n = 10 per group). The unhandled rats were designated as the control group. The gastrointestinal motility of the rats was evaluated using the charcoal propulsion test. Histopathology was assessed by hematoxylin and eosin (HE) staining. The enzyme-linked immunosorbnent assay method was used to detect the levels of motilin (MTL), gastrin (GAS), vasoactive intestinal peptide (VIP), and somatostatin (SS) in the serum from each group. In addition, the gut microbiota composition of fecal samples was analyzed using 16S rRNA sequencing. Rat models were successfully established according to data from rat state, gastrointestinal motility assessments, and HE staining. WCAP improved FD symptoms by accelerating the gastric emptying and small intestinal transit of FD rats. Mechanistically, WCAP increased the levels of GAS and MTL and reduced the levels of VIP and SS. Moreover, WCAP treatment restored the total relative abundance of Firmicutes and Bacteroidetes, increased the species richness of the gut flora, and modulated the changes in the composition and function of the gut microbiota. WCAP can effectively promote the recovery of gastrointestinal motility disorders in FD rats. The mechanism may be related to regulating the secretion of BGPs and the composition of the gut microbiota.

Effects of heavy metal concentration on zooplankton community composition and abundance in the Yellow Sea coast

The coastal area of the Yellow Sea is a highly urbanized and industrialized region in China, which has been severely polluted because of intensive human activities. And the heavy metals (HMs) pollution has posed a serious threat to aquatic environments and ecosystem health. However, most studies have focused on the toxicity and bio-accumulation of HMs in zooplankton, while neglecting their effects on the overall community structure. To address the gap in this field, four research cruises was conducted in 2022 to analyze the concentrations of representative HMs (Hg, As, Cu, Zn, Pb, and Cd) in surface seawater along the Yellow Sea coast, as well as the composition and abundance of zooplankton communities, aiming to assess the potential ecological impacts in the region. The results indicated that the concentrations of the six HMs in the seawater were in the low to moderate range. Analytical results showed that Zn and As were key metals influencing the abundance and community composition of zooplankton along the Yellow Sea coast: an increase in Zn concentration, coupled with a decrease in As concentration, was associated with an increase in total zooplankton abundance and a more diverse community. The most frequently occurring zooplankton in the survey were copepods, which exhibited a higher tolerance to HMs. Additionally, the significant fluctuations of Zn, As, and Hg during spring and autumn led to explosive growth of Noctiluca scintillans. We observed that the influence of HMs on marine zooplankton was not isolated but rather interacts with multiple factors. Overall, this study highlights the possibility of alterations in marine ecological structures due to changes in HMs concentration levels. It underscores the importance of continuous monitoring of heavy metal concentrations in the Yellow Sea for the long-term protection of marine ecosystems.

Alkalothermophilic Iron-Reducing Bacteria of the Goryachinsk Thermal Water Basin

A study of iron-reducing prokaryotes that use the poorly crystalline mineral ferrihydrite as an electron acceptor revealed their widespread occurrence on the planet. However, the ability of iron reducers to develop under polyextreme conditions (at elevated values of pH and temperature) has not been previously demonstrated. To confirm the existence of alkalothermophilic iron reducers, we studied the water and sediment samples from the Goryachinsk nitrogen-rich thermal water basin. These springs are associated with young tectonic fractures in the Baikal rift zone; their water is characterized by low salinity, alkaline pH (8.8‒9.2) and temperature of 53‒55°C. Enrichment cultures reducing synthesized ferrihydrite were obtained by adding this mineral to the water and sediment samples from the Goryachinsk thermal springs, followed by anaerobic incubation at 50 and 55°C. The 16S rRNA gene profiling of the water and sediment samples and of the primary enrichment cultures revealed high taxonomic diversity, almost exclusively represented by bacterial taxa. Subsequent transfers with ferrihydrite and organic acids or hydrogen as electron donors resulted in stable enrichment cultures of organo- and lithotrophic alkalothermophilic iron reducers. Members of the genus Parvivirga, one of the first cultured representatives of the OPB41 group (now the order Anaerosomatales, phylum Actinomycetota), constituted 30 to 50% of the total abundance.

Epidemiological Study of Parasites of the Edible Scallop Aequipecten tehuelchus in Patagonia, Southwest Atlantic Ocean.

This study assesses the health status of the edible Tehuelche scallop, Aequipecten tehuelchus, reporting the epidemiological results of the parasites and their infection levels by histopathological analysis and transmission electron microscopy. Environmental factors (site: West and East domains of the San José gulf, seawater temperature) and host traits (size, physiological condition index, gonad development stages) associated with parasite load (prevalence, mean intensity, parasite abundance and total parasite abundance) were tested with generalised linear models (GLMs). Histopathological results revealed Rickettsia-like organisms (RLOs), several protozoans (Trichodina sp., Nematopsis sp. and APXSc apicomplexans) and metazoans (turbellarians and Tumidotheres maculatus pea crabs) as well as inflammatory lesions in form of granulomas and hemocytic infiltration. The prevalence of the parasitofauna did not vary significantly between gulf domains, except the apicomplexan APXSc that was significantly most prevalent in scallops from the East Domain. However, the mean intensity of infection seemed to be determined by the gulf domains, which present distinct hydrographic regimes, where RLO's, Trichodina sp. and T. maculatus were significantly more intense in scallops from the West, opposite with Nematopsis sp. infection. Total parasite abundance was influenced by seasonal variations, it was negatively correlated with warmer temperatures. The physiological condition index of A. tehuelchus seemed not to be affected by the presence or abundance of any of the parasites. Nevertheless, the apicomplexan APXSc would represent a significant risk to the health of A. tehuelchus due to the pathological conditions, and surveillance of this parasite is needed for a sustainable A. tehuelchus fishery.

Impact of shallow hydrothermal vent waters on monsoonal copepod distribution and abundance around active volcanic island off northeast Taiwan, West Pacific

Extreme oceanic environments such as shallow hydrothermal vents (HVs) have rarely been investigated with respect to their impact on the water column and its organisms, such as zooplankton. We collected mesozooplankton from the near shore shallow HV areas off northeast Taiwan during three distinct monsoonal periods in 2022. The results showed the occurrence of 99 copepod species belonging to 24 families and 49 genera from a one-year study. The results from similarity percentage (SIMPER) and indicator species analysis (IndVal) identified that top 5 species namely Temora turbinata, Oncaea venusta, Clausocalanus furcatus, Macrosetella gracilis, and Canthocalanus pauper showed variations in their abundance between HV and non-HV sites which contributed to 72.12 % dissimilarity with only four of the species with significantly higher contributions during the SW monsoon season. This distinction is explained by the fact that copepods were negatively affected by HV water. Furthermore, Temora turbinata (3530.7 ± 4967.83 ind. m−3), Calanus sinicus (70.86 ± 163.78 ind. m−3), and Paracalanus parvus (40.47 ± 85.67 ind. m−3) emerging as the dominant species with a clear seasonal succession pattern during the southwest monsoon, northeast-southwest monsoon transition, and northeast monsoon prevailing phase, respectively. The total abundance of copepod was significantly higher during the southwest monsoon than during the other two monsoonal periods (p < 0.01, one-way ANOVA). In contrast, the number of species and the richness index were significantly higher during the northeast-southwest and northeast monsoon than during the southwest monsoon period (p < 0.05, one-way ANOVA) indicating temporal succession in the copepod community.

A coupled model of zebra mussels and chlorine in collective pressurized irrigation networks

Zebra mussel infestation has become a serious problem affecting pressurized networks. Larvae settle in pipeline walls creating relevant obstructions to flow as they grow and develop shells. Oxidant injections in the stream are commonly used to control the infestation. A model is proposed for simulating the transportation, settlement and death of mussels in pressurized networks. This model is coupled to a solute transport, diffusion, and decay model of oxidant chemicals. During the analyzed irrigation campaigns, the larvae entry was monitored at various intervals. These data, showing high variability, were used as input to the model using different scenarios averaging and modifying the time distribution of larvae concentration. Simulations predicted similar mussel settlement patterns across all scenarios, suggesting that network morphology and total larval abundance primarily influence settlement distribution. We compared the effectiveness of continuous and intermittent oxidant applications. Continuous treatments were the most effective (up to 99%), but required up to 3.5 kg ha−1 of chlorine. Reasonable control could also be attained with short injections (1 to 3 h) just before the peak irrigation service discharge, leading to up to 93% of chlorine savings and reaching similar mortality rates. The model was also used to estimate the larvae and chlorine export to on-farm irrigation systems through hydrants and to evaluate strategies for mitigating the risks of on-farm infestation and environmental impact. The protection of on-farm irrigation systems required additional chlorine input. The model can be parametrized to simulate similar species in different types of pressurized networks, using different chemicals for treatment.

Effect of Cow Bone Addition on the Humification, Heavy Metals Passivation and Fate of Resistance Genes During Swine Manure Composting

Bone meal has been used as economic and effective additive for heavy metals (HMs) pollution remediation due to the distinct components and structures that enable their favorable properties, such as its low cost, high adsorption capacity, acid-base adjustability, and ion-exchange capability. However, no attempt has been made to establish whether cow bone could promote the passivation of HMs and the removal of metal resistance genes (MRGs) and antibiotics resistance genes (ARGs) during the composting process. Two sizes of cow bone (meal (T2) and granule (T3)) were added to investigate their effects on humification, HMs passivation and the abundance of ARGs and MRGs during swine manure composting. Excitation-emission matrix (EEM)-parallel factor analysis showed that the percentage of maximum fluorescence intensity of humic-like substances were higher in T2 (91.82%) than in T3 (88.46%), implying that T2 could promote the humification process compared to T3. In comparison with control (T1), the addition of T2 and T3 could promote the change of exchangeable Cu and reducible Cu into oxidizable Cu, thus reducing the mobility factors (MF) of Cu in T2 and T3 treatments by 10.48% and 6.98%, respectively. In addition, T2 and T3 could increase exchangeable Zn into reducible Zn and oxidizable Zn, thereby reducing the MF of Zn in T2 and T3 treatments by 18.80% and 2.0%, respectively. Quantitative Real-time PCR (qPCR) analysis revealed that the total abundances of MRGs were decreased by 100% in T2 and T3 treatments, and T2 decreased the total relative abundance of ARGs. Furthermore, the relative abundance of ARGs and MRGs had significantly correlated with intI1 and bio-available of Cu and Zn, which was triggered by selective pressure of HMs and horizontal gene transfer. The present study suggested that cow bone meal as additives can be a feasible approach to promote the passivation of HMs and enhance the removal of MGRs and ARGs by decreasing horizontal gene transfer and selective pressure by bioavailable HMs.

The Effects of Predominantly Chemoautotrophic Versus Heterotrophic Biofloc Systems on Nitrifying Bacteria, Planktonic Microorganisms, and Growth of Penaeus vannamei, and Oreochromis niloticus in an Integrated Multitrophic Culture

The aim of this study was to evaluate the effect of predominantly chemoautotrophic and heterotrophic biofloc systems on ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and planktonic microorganisms in an integrated Penaeus vannamei and Oreochromis niloticus integrated multitrophic culture. Shrimp and tilapia were stocked at a density of 400 shrimp m−2 and 45 fish m−3, respectively. The trial consisted of two biofloc treatments, with three replicates each: chemoautotrophic and heterotrophic. The identification and quantification of the planktonic microorganisms (ciliates, flagellates, microalgae, and total bacteria) and nitrifying bacteria were carried out through direct counting and fluorescence in situ hybridization, respectively. At the end of the trial, heterotrophic treatment had resulted in higher total abundance of bacteria. The relative abundance of AOB and NOB in relation to the total abundance was less than 0.1% for both treatments. The system was dominated by flagellates in both treatment groups. The abundance of microalgae and ciliates was higher with chemoautotrophic treatment. After 43 days, the shrimp weights were higher in the chemoautotrophic group, while the final weights of the tilapia were not significantly different between the two treatments. The type of biofloc system (Chemoautotrophic vs. Heterotrophic) did not significantly alter the establishment of AOB and NOB in a Penaeus vannamei and Oreochromis niloticus integrated multitrophic culture. The two treatments proved to be equally efficient for maintaining good water quality, but the chemoautotrophic treatment resulted in better shrimp growth. Thus, our study demonstrated that chemoautotrophic biofloc is a promising approach in integrated multitrophic aquaculture.

Spatiotemporal Variation in Dissolved, Bioavailable, and Particulate Elements and the Abundance of Harmful Algae in Grand Lake.

Harmful algal blooms (HABs) are often linked to the increased loading of limiting nutrients such as nitrogen and phosphorus. Little is known about the relevance of other biogenic elements, the supplies of which are spatiotemporally heterogeneous, on HABs. We measured the dissolved, bioavailable, and particulate concentrations of 26 elements at four locations draining different catchments of a large reservoir during three seasons, in addition to the total abundance of phytoplankton and % of cyanobacteria. Finally, we manipulated a key element (Fe) in microcosms to test its effect on the community. Phytoplankton abundance and community structure varied spatiotemporally, with minimal variation in N/P. The variation in environmental supplies of several other elements was correlated with phytoplankton abundance, as well as up to 3 orders of magnitude differences in cyanobacterial yield. Bioassays manipulating Fe impacted total phytoplankton as well as the abundance of cyanobacteria, with Fe-chelated treatments resulting in a significant decline in phytoplankton as well as cyanobacterial yield. In summary, we found substantial heterogeneity in elemental supplies that are relevant to the phytoplankton community. Exploring the relevance of the entire system of elements in the context of HABs may be more rewarding than studies emphasizing a subset of elements.

Wheat field earthworms under divergent farming systems across a European climate gradient.

Earthworms are a key faunal group in agricultural soils, but little is known on how farming systems affect their communities across wide climatic gradients and how farming system choice might mediate earthworms' exposure to climate conditions. Here, we studied arable soil earthworm communities on wheat fields across a European climatic gradient, covering nine pedo-climatic zones, from Mediterranean to Boreal (S to N) and from Lusitanian to Pannonian (W to E). In each zone, 20-25 wheat fields under conventional or organic farming were sampled. Community metrics (total abundance, fresh mass, and species richness and composition) were combined with data on climate conditions, soil properties, and field management and analyzed with mixed models. There were no statistically discernible differences between organic and conventional farming for any of the community metrics. The effects of refined arable management factors were also not detected, except for an elevated proportion of subsurface-feeding earthworms when crop residues were incorporated. Soil properties were not significantly associated with earthworm community variations, which in the case of soil texture was likely due to low variation in the data. Pedo-climatic zone was an overridingly important factor in explaining the variation in community metrics. The Boreal zone had the highest mean total abundance (179 individuals m-2) and fresh mass (86 g m-2) of earthworms while the southernmost Mediterranean zones had the lowest metrics (<1 individual m-2 and <1 g m-2). Within each field, species richness was low across the zones, with the highest values being recorded at the Nemoral and North Atlantic zones (mean of 2-3 species per field) and declining from there toward north and south. No litter-dwelling species were found in the southernmost, Mediterranean zones. These regional trends were discernibly related to climate, with the community metrics declining with the increasing mean annual temperature. The current continent-wide warming of Europe and related increase of severe and rapid onsetting droughts will likely deteriorate the living conditions of earthworms, particularly in southern Europe. The lack of interaction between the pedo-climatic zone and the farming system in our data for any of the earthworm community metrics may indicate limited opportunities for alleviating the negative effects of a warming climate in cereal field soils of Europe.

When does spillover from marine protected areas indicate benefits to fish abundance and catch?

Spillover is a term commonly applied to the dispersal of fish and/or larvae from inside a closed area to areas open to fishing. The presence of spillover is often quantified by measuring gradients in attributes such as abundance or catch rates near the boundaries of closed areas or by measuring higher abundance inside closed areas compared to outside. It is commonly assumed that such gradients or ratios indicate that the closed area has benefitted the fishery and the total abundance of fish. We explore this assumption using a spatially explicit model of closed areas with different intensities of fishing and fish movement, and we find that such gradients will be expected any time there is higher abundance inside the closed area. However, such gradients do not necessarily indicate a benefit to the fishery either in terms of total catch or catch rate, and unless pre-closure fishing was intense, total abundance is not expected to rise significantly. We examine case studies that argue that spillover exists and leads to fishery benefits. We then evaluate the evidence for net benefits in these case studies and find those with evidence of net benefits all come from places where fishing pressure was intense. While most analysis come from quite small coastal closed areas, two studies of very large open-ocean closed areas are discussed, and we find that both suggest little overall impact on the tuna populations that support the main commercial fisheries affected by the closures in question.