Summer Communities Research Articles

Beyond blooms: the winter ecosystem reset determines microeukaryotic community dynamics in the Fram Strait

The Arctic Ocean is undergoing a major transition as a result of global warming, with uncertain consequences for its ecosystems. Our study introduces an integrated analytical approach using co-occurrence networks, convergent cross-mapping, and energy landscape analysis. Applied to four years of amplicon data from Fram Strait, located at the boundary between Arctic and Atlantic waters, our method identifies keystone species in seasonal microbial communities, elucidates causal interactions, and predicts stable configurations across changing environments. We find strong evidence for a “winter reset”, implying that organisms representing the spring bloom are largely determined by prevailing environmental conditions during winter. In addition, our analysis suggests that winter communities may adapt more readily to expected Atlantification than summer communities. These results highlight the utility of innovative time-series analyses in disentangling ecosystem dynamics. This approach provides critical insights into Arctic ecological interactions, dynamics, and resilience and aids in understanding ecosystem responses to environmental change.

Seasonal variation in metabolic profiles and microbial communities in a subarctic ore processing plant.

The mining industry strives to reduce its water footprint by recycling water in ore processing. This leads to build-up of ions, flotation chemicals and microbial biomass, which may affect the process. The Boliden Kevitsa mine in Northern Finland is exposed to seasonal change and recycles up to 90% of the process water. We studied the variation in size, composition and putative functions of microbial communities in summer and winter in the ore processing plant. The raw water, Cu and Ni thickener overflow waters had statistically significantly higher bacterial numbers in winter compared to summer, and specific summer and winter communities were identified. Metagenomic analysis indicated that Cu and Hg resistance genes, sulphate/thiosulphate, molybdate, iron(III) and zinc ABC transporters, nitrate reduction, denitrification, thiosulphate oxidation and methylotrophy were more common in winter than in summer. Raw water drawn from the nearby river did not affect the microbial communities in the process samples, indicating that the microbial communities and metabolic capacities develop within the process over time in response to the conditions in the processing plant, water chemistry, used chemicals, ore properties and seasonal variation. We propose that the microbial community structures are unique to the Boliden Kevitsa mine and processing plant.

Microbial community diversity from nearshore to offshore in the East China Sea.

The Pollution Nagasaki (PN) section of the East China Sea (ECS) is a typical area for studying the complex hydrographic dynamics between Changjiang River discharge and Kuroshio, displaying intense variations of environmental gradients from nearshore to offshore. However, the temporal and spatial changes of microbial communities along the PN section have long been overlooked. In this study, we performed a comprehensive investigation into the abundance, diversity and ecology of free-living (FL) and particle-associated (PA) microbial communities in seawater samples along the PN section during both summer and winter. Distinct hydrological conditions and resulting environmental gradients were observed between summer and winter, with clear features of intrusive Kuroshio subsurface water in summer and strong vertical mixing of seawater in winter. Bacterial abundance along the PN section was higher in summer (1.11 × 108 copies·L-1 - 7.37 × 108 copies·L-1) than in winter (1.83 × 106 copies·L-1 - 1.34 × 108 copies·L-1). Microbial diversity, as indicated by α-diversity indices, remained at relatively stable levels in summer, while a clear decreasing trend was observed in winter along the PN section. Additionally, the winter communities exhibited a more evident spatial shift along the PN section compared to the summer communities. 16S rRNA gene amplicon sequencing showed that microbial community composition varied considerably between different seasons (summer and winter) and lifestyles (FL and PA), with a notable dominance of Ralstonia species. in winter. Regarding the assembly of microbial communities, the stochastic process represented by dispersal limitation was the dominant process in summer, while the deterministic homogeneous selection was the most important process in winter. Correspondingly, distinct topological properties of the microbial co-occurrence networks were shown between different seasons and along the PN section. These results enhance our understanding of how hydrological conditions influence dynamic changes of microbial communities along the PN section, providing new insights for the microbial community assembly and interactions in such a complex environment.

Temperature Adaptation of Aquatic Bacterial Community Growth Is Faster in Response to Rising than to Falling Temperature

Bacteria are key organisms in energy and nutrient cycles, and predicting the effects of temperature change on bacterial activity is important in assessing global change effects. A changing in situ temperature will affect the temperature adaptation of bacterial growth in lake water, both long term in response to global change, and short term in response to seasonal variations. The rate of adaptation may, however, depend on whether temperature is increasing or decreasing, since bacterial growth and turnover scale with temperature. Temperature adaptation was studied for winter (in situ temperature 2.5 °C) and summer communities (16.5 °C) from a temperate lake in Southern Sweden by exposing them to a temperature treatment gradient between 0 and 30 °C in ~ 5 °C increments. This resulted mainly in a temperature increase for the winter and a decrease for the summer community. Temperature adaptation of bacterial community growth was estimated as leucine incorporation using a temperature Sensitivity Index (SI, log growth at 35 °C/4 °C), where higher values indicate adaptation to higher temperatures. High treatment temperatures resulted in higher SI within days for the winter community, resulting in an expected level of community adaptation within 2 weeks. Adaptation for the summer community was also correlated to treatment temperature, but the rate of adaption was slower. Even after 5 weeks, the bacterial community had not fully adapted to the lowest temperature conditions. Thus, during periods of increasing temperature, the bacterial community will rapidly adapt to function optimally, while decreasing temperature may result in long periods of non-optimal functioning.

Study on the Noise Reduction Effect of Vegetation Communities in Northeast China – Taking Forest Park in Yingkou City as an Example

In this study, the greenland tree and shrub communities in Forest Park, a typical park greenland in Yingkou City, Liaoning Province, were used as the research object to compare the noise reduction of different communities, and to study the degree of noise reduction of the plant communities in summer. The results show that the noise reduction level of vegetation communities in summer is in the following order: M2 cypress + cypress + acacia > M1 poplar + Euphorbia + maple > M3 cypress + yellow thorn rose + ginkgo tree.

Pan traps: An effective tool for monitoring phenological changes in insect floral visitors and their relationship with floral resources in a coastal Mediterranean forest

Precise monitoring of insect floral visitors and their relationship with floral resources throughout the flowering season provides baseline information to help us understand long-term changes in plant-pollinator interactions and improve pollinator conservation strategies. Pan traps are one of the methods most used for monitoring insect floral visitors and several studies have already linked the abundance and richness of these floral visitors with floral resources. However, less research has been conducted into the effectiveness of pan traps for monitoring phenological changes in the floral visitor community with regard to floral resources. We used pan traps to study the species composition and the abundance of insect floral visitors and their relationship with flower richness in a coastal forest throughout the entire flowering season for two consecutive years. Captures were confirmed to be floral visitors through field survey studies. Pan traps were effective for revealing changes in the abundance and species composition of floral visitor communities during and between years that correlated with changes in floral richness and species composition. Changes in floral visitor abundance showed a different bias in their association with floral richness. Thus, while Hymenoptera and Diptera abundance tended to be negatively correlated with floral richness, Coleoptera abundance tended to be positively correlated, although such correlations could change from year to year. There were two significantly different groups of flowering plant and floral visitor species: one in spring and the other in summer. Each period was characterized by unique overlap between some floral visitors and their floral resources, suggesting that to monitor floral visitors effectively both communities need to be considered. Interestingly, the floral phenology in this coastal forest extended longer than that of more inland communities, so reliable monitoring of floral visitors throughout the floral season may help us to better understand the role of coastal plant communities in the stabilization of the pollinator networks of more inland communities. Overall, phenology patterns need to be taken into account for pan trapping to become an effective methodology for monitoring floral visitor communities, considering both intra-year (spring and summer communities) and inter-year variations.

Cooling and humidification effects of coniferous and broad-leaved plant communities in urban park

As an essential part of urban parks, plant communities are of great importance in regulating the urban climate. Community structures and external elements are important factors influencing the microclimate effects of urban park communities. However, it remains unclear how these two factors affect the cooling and humidification effects of coniferous and broad-leaved communities. Taking Nanhu Park (Changchun) as a case study, we conducted measurements on the microclimate effects of 40 plant communities in summer. The results demonstrated that the optimal cooling effect of the communities occurred at about 15:00, and the humidification effect remained stable in the morning and increased after 12:00. The highest average cooling and humidification values in coniferous communities reached 3.38 °C and 17.23%, respectively, whereas those in the broad-leaved communities were 3.24 °C and 17.23%, respectively. Community structures were identified as the primary factor influencing the microclimate effects of broad-leaved communities, while the intensity of microclimate effects in coniferous communities was primarily influenced by the surrounding roads and water bodies. Our study provides insights for urban planners to comprehend the synergistic interaction between internal community structures and external elements and the microclimate effects of urban park communities.

Plankton communities of the “Pregolya River – Vistula Lagoon – Kaliningrad Sea Channel (KSC) – Baltic Sea system”

The species composition, abundance and biomass, trophic relationships of phytoplankton and zooplankton, as well as the proportion of dead individuals in zooplankton were studied in the water system "Pregolya River – Kaliningrad Sea Channel (KSC) – Vistula Lagoon – Baltic Sea" in July, August and October 2021. In total 173 taxa of phytoplankton and 73 taxa of zooplankton were found during period of investigation. The maximal species diversity was observed in the summer period, in autumn it was decreasing. The maximum number of taxa for both phyto- and zooplankton was found in the Vistula Lagoon and in the KSC, the minimum – in the Baltic Sea. In summer the 3 communities in phytoplankton, 4 in zooplankton, in autumn – 3 communities in both phyto- and zooplankton were found. The plankton communities were confined to water areas with different salinity: The Pregolya River, the KSC and the Vistula Lagoon, the Baltic Sea. The dominant complex of species at the stations differed; species of a predominantly freshwater complex were noted in the Pregolya River, brackish-water species were found in the Vistula Lagoon, and a marine complex of species was identified at the stations of the sea strait and in the Baltic Sea. More abundant plankton communities both in summer and autumn were in the KSC and the Vistula Lagoon (phytoplankton biomass varied from 1.19 g/m3 to 11.89 g/m3; zooplankton biomass varied from 305 mg/m3 to 1801 mg/m3). In this area the most optimal conditions for the development of plankton were formed such as an increased nutrient content and maximum water heating. Plankton communities both in the Pregolya River and in the Baltic Sea in summer and autumn were less abundant (phytoplankton biomass varied from 0.16 g/m3 to 2.50 g/m3; zooplankton biomass varied from 34 mg/m3 to 468 mg/m3). The most intense trophic relationships in the plankton community in the summer in the Baltic Sea, optimal – in the KSC and in the Vistula Lagoon were formed. The proportion of dead individuals in the zooplankton of the studied system in both seasons was maximal in the areas, which had the critical salinity for hydrobionts and high turbulence conditions such as KSC, the Sea strait and at the exit from Sea strait.

Multi-objective optimization design of residential area based on microenvironment simulation

In current research on old communities, less attention is given to the comfort and greenhouse gas emissions of the indoor and outdoor physical environment. Only a few studies focus on optimization strategies for these environments in old communities. Thus, the absence of suitable theoretical guidance in specific engineering practices can lead to issues. Renovated old communities still face challenges such as overheating in summer, overcooling in winter, and high energy consumption. In this article, based on the optimization of low- and medium-rise old communities in five typical cities in China, corresponding strategies such as geometric and envelope design parameters are proposed in terms of building greenhouse gas emission and indoor and outdoor thermal environment comfort. Several methods are employed in this study, including parametric simulation using Grasshopper with the Ladybug and Honeybee plugins for data collection. This research conduct sensitivity analysis using Random Forest Regressor (RFR), Gradient Boosting Regressor (GBR) and Decision Tree Regressor (DTR) to explore the relationship between design variables and environmental objectives. Predictive modeling with ensemble models and multi-objective optimization using the NSGA-2 algorithm help identify optimal design parameters for varied urban climates. The results demonstrated indoor and outdoor comfort of communities can be improved to a greater extent while reducing carbon emissions. Quantitatively, compared to the baseline model, all cities except Wuhan can improve the year-round comfort time of the outdoor thermal environment by more than 50%. Besides, communities in hot summer and warm winter regions (e.g. Shenzhen and Nanning) can reduce their annual carbon emissions by more than 300t, and communities in hot summer and cold winter regions (e.g. Hangzhou, Chengdu and Wuhan) can reduce their annual carbon emissions by more than 100t. The research results will serve as a scientific basis for energy saving and emission reduction and provide decision-making methods for the development of old communities.

Species invasions shift microbial phenology in a two-decade freshwater time series

Invasive species impart abrupt changes on ecosystems, but their impacts on microbial communities are often overlooked. We paired a 20 y freshwater microbial community time series with zooplankton and phytoplankton counts, rich environmental data, and a 6 y cyanotoxin time series. We observed strong microbial phenological patterns that were disrupted by the invasions of spiny water flea (Bythotrephes cederströmii) and zebra mussels (Dreissena polymorpha). First, we detected shifts in Cyanobacteria phenology. After the spiny water flea invasion, Cyanobacteria dominance crept earlier into clearwater; and after the zebra mussel invasion, Cyanobacteria abundance crept even earlier into the diatom-dominated spring. During summer, the spiny water flea invasion sparked a cascade of shifting diversity where zooplankton diversity decreased and Cyanobacteria diversity increased. Second, we detected shifts in cyanotoxin phenology. After the zebra mussel invasion, microcystin increased in early summer and the duration of toxin production increased by over a month. Third, we observed shifts in heterotrophic bacteria phenology. The Bacteroidota phylum and members of the acI Nanopelagicales lineage were differentially more abundant. The proportion of the bacterial community that changed differed by season; spring and clearwater communities changed most following the spiny water flea invasion that lessened clearwater intensity, while summer communities changed least following the zebra mussel invasion despite the shifts in Cyanobacteria diversity and toxicity. A modeling framework identified the invasions as primary drivers of the observed phenological changes. These long-term invasion-mediated shifts in microbial phenology demonstrate the interconnectedness of microbes with the broader food web and their susceptibility to long-term environmental change.

Seasonal succession of microbial community co-occurrence patterns and community assembly mechanism in coal mining subsidence lakes.

Coal mining subsidence lakes are classic hydrologic characteristics created by underground coal mining and represent severe anthropogenic disturbances and environmental challenges. However, the assembly mechanisms and diversity of microbial communities shaped by such environments are poorly understood yet. In this study, we explored aquatic bacterial community diversity and ecological assembly processes in subsidence lakes during winter and summer using 16S rRNA gene sequencing. We observed that clear bacterial community structure was driven by seasonality more than by habitat, and the α-diversity and functional diversity of the bacterial community in summer were significantly higher than in winter (p < 0.001). Canonical correspondence analysis indicated that temperature and chlorophyll-a were the most crucial contributing factors influencing the community season variations in subsidence lakes. Specifically, temperature and chlorophyll-a explained 18.26 and 14.69% of the community season variation, respectively. The bacterial community variation was driven by deterministic processes in winter but dominated by stochastic processes in summer. Compared to winter, the network of bacterial communities in summer exhibited a higher average degree, modularity, and keystone taxa (hubs and connectors in a network), thereby forming a highly complex and stable community structure. These results illustrate the clear season heterogeneity of bacterial communities in subsidence lakes and provide new insights into revealing the effects of seasonal succession on microbial assembly processes in coal mining subsidence lake ecosystems.

Predation risk estimated on live and artificial insect prey follows different patterns.

Models mimicking prey organisms are increasingly used in ecological studies, including testing fundamental ecological and evolutionary theories. The general consensus is that predation risk estimated on artificial models may not quantitatively correspond to predation pressure on live prey, but it still can be used in various comparisons. We tested whether the use of live and artificial prey reveals the same patterns of variation in predation risk. We exposed live prey (blowfly larvae and puparia) and plasticine models of blowfly puparia in two boreal forest sites, both openly and in ant- and bird-exclusion treatments, and we quantified attacks by both avian and invertebrate predators. Bird attack rates were always higher on live puparia than on their plasticine models, but the magnitude of this difference declined from 8.4-fold in early summer to 2-fold in mid- and late-summer. We attribute these changes to different responses to prey by experienced adult birds that dominate the bird communities in early summer versus explorative juvenile birds that are abundant later in the season. Invertebrate daily predation rates on maggots decreased from 56% in early summer to 28% in late summer, but invertebrate attacks on plasticine models showed no seasonal changes. Overall, invertebrate predation on maggots was 67-fold greater than their predation on models. Observations showed that wood ants did not attack plasticine models and did not leave on them any damage marks. Estimates based on artificial prey indicate a much greater role of bird predation than invertebrate predation, while estimates based on live prey suggest the opposite pattern. Thus, using live and artificial prey may lead to different conclusions about relative importance of different predator groups in a locality. Moreover, for both avian and invertebrate predators, predation risk based on artificial and live prey shows different seasonal changes and may potentially demonstrate different spatial patterns.

Half-century trends in alpha and beta diversity of phytoplankton summer communities in the Helsinki Archipelago, the Baltic Sea.

We analyzed phytoplankton biodiversity trends in a 52year (1967-2018) monitoring time-series from the archipelago of Helsinki, Gulf of Finland, the Baltic Sea. The community ordination revealed strong ordering of samples along the time axis (generalized additive model-gam fit: R 2 = 0.9). Species richness increased in time and was the most influential alpha diversity descriptor related to the community structure (gam fit: R 2 = 0.56-0.70). Changes in species richness accounted for 35-36% of the mean between-sample beta diversity. The remaining 64-65% was due to species turnover-the dominant component of the biodiversity trend. The temporal beta diversity trend reflected the eutrophication history of the geographically confined region, with a turning point in mid-1990s demarking the adaptation and recovery phases of the phytoplankton community. Trends in spatial beta diversity revealed homogenization of the communities in the outer archipelago zone, but not in the inner bays. The temporal decay of community similarity revealed high turnover rate, with 23.6years halving time in the outer archipelago and 11.3years in the inner bays, revealing the differences in eutrophication strength. The observed phytoplankton trends manifest the regional eutrophication history, and dispersal of new species to the unsaturated brackish species pool.

Postfire salvage logging alters impacts of recent wildfire on small mammal communities in summer

Abstract Wildfire is a natural ecosystem disturbance in forests in North America, yet fires are often at odds with human activity and affect the timber supply. Postfire salvage logging is common practice globally, but the impacts of salvage logging on wildlife, especially small mammal communities, remain unclear. We livetrapped small mammals to determine their population responses to wildfire and postfire salvage logging in central British Columbia, Canada. Postfire regenerating forest provided habitat for deer mice (Peromyscus maniculatus), southern red-backed voles (Myodes gapperi), and meadow voles (Microtus pennsylvanicus). Postfire salvage logging significantly reduced tree basal area and changed small mammal community structure by reducing southern red-backed vole populations and supporting mainly deer mice, a generalist species. Given the large scale and intensity of postfire salvage logging operations across the province, salvage logging has the potential to decrease vole populations and change small mammal communities across the province.

Occurrence of polycyclic aromatic compounds and potentially toxic elements contamination and corresponding interdomain microbial community assembly in soil of an abandoned gas station

Bacteria, archaea and fungi usually coexist in various soil habitats and play important roles in biogeochemical cycle and remediation of contamination. Despite their significance, their combined bioassembly pattern, ecological interactions and driving factors in contaminated soils still remain obscure. To fill the gap, a systemic investigation on the characteristics of microbial community including bacteria, archaea and fungi, assembly patterns and environmental driving factors was conducted in an abandoned gas station soils which were contaminated by polycyclic aromatic compounds and potentially toxic elements for decades. The results showed that the soils were contaminated excessively by benzo[a]pyrene (0.46–2.00 mg/kg) and Dibenz[a,h]anthracene (0.37–1.30 mg/kg). Multitudinous contaminant-degrading/resistant microorganisms and unigenes were detected, indicating potential of the soils to mitigate the pollution. Compared with fungi and archaea, the bacteria had higher community diversity and were more responsive to seasonal shifts. Functional genes (nidB, nahAb, nahAa, adhP, adh, adhC, etc.) involved in biodegradation were highly enriched in summer (1.96% vs 1.80%). The co-occurrence network analysis showed summer communities exhibit a more robust network structure and positive interactions than winter communities. The fungi Neocucurbitaria, Penicillium, Fusarium, Chrysosporium, Knufia, Filobasidium, Wallemia and Rhodotorula were identified as the keystone taxa, indicating that fungi also had important positions in the interdomain molecular ecological networks of both seasons. The network topological properties and |βNTI| (66.7%–93.3% greater than 2) results indicated the deterministic assembly processes of the microbial communities in the contaminated soil. Acenaphthylene, benzo[b]fluoranthene, indeno[1,2,3-cd]perylene, benzo[g,h,i]pyrene and 9-fluorenone were the key environmental factors driving the deterministic assembly processes of the interdomain microbial community in the contaminated soil. These findings extended our knowledge of interdomain microbial community assembly mechanisms and ecological patterns in natural attenuation and provide valuable guidance in associated bioremediation strategies.

Correlating the above- and belowground genotype of Pinus pinaster trees and rhizosphere bacterial communities under drought conditions

Increasing temperatures along with severe droughts are factors that may jeopardize the survival of the forests in the Mediterranean basin. In this region, Pinus pinaster is a common conifer species, that has been used as a model species in evolutionary studies due to its adaptive response to changing environments. Although its drought tolerance mechanisms are already known, knowledge about the dynamics of its root microbiota is still scarce. We aimed to decipher the structural (bacterial abundance), compositional, functional and associative changes of the P. pinaster rhizosphere bacterial communities in spring and summer, at DNA and RNA level (environmental DNA, live and dead cells, and those synthesizing proteins). A fundamental aspect of root microbiome-based approaches is to guarantee the correct origin of the samples. Thus, we assessed the genotype of host needles and roots from which rhizosphere samples were obtained. For more than 50% of the selected trees, genotype discrepancies were found and in three cases the plant species could not be determined. Rhizosphere bacterial communities were homogeneous with respect to diversity and structural levels regardless of the host genotype in both seasons. Nonetheless, significant changes were seen in the taxonomic profiles depending on the season. Seasonal changes were also evident in the bacterial co-occurrence patterns, both in DNA and RNA libraries. While spring communities switched to more complex networks, summer populations resulted in more compartmentalized networks, suggesting that these communities were facing a disturbance. These results may mirror the future status of bacterial communities in a context of climate change. A keystone hub was ascribed to the genus Phenylobacterium in the functional network calculated for summer. Overall, it is important to validate the origin and identity of plant samples in any plant-microbiota study so that more reliable ecological analyses are performed.

Freshwater Microbial Eukaryotic Core Communities, Open-Water and Under-Ice Specialists in Southern Victoria Island Lakes (Ekaluktutiak, NU, Canada).

Across much of the Arctic, lakes and ponds dominate the landscape. Starting in late September, the lakes are covered in ice, with ice persisting well into June or early July. In summer, the lakes are highly productive, supporting waterfowl and fish populations. However, little is known about the diversity and ecology of microscopic life in the lakes that influence biogeochemical cycles and contribute to ecosystem services. Even less is known about the prevalence of species that are characteristic of the seasons or whether some species persist year-round under both ice cover and summer open-water conditions. To begin to address these knowledge gaps, we sampled 10 morphometrically diverse lakes in the region of Ekaluktutiak (Cambridge Bay), on southern Victoria Island (NU, Canada). We focused on Greiner Lake, the lakes connected to it, isolated ponds, and two nearby larger lakes outside the Greiner watershed. The largest lakes sampled were Tahiryuaq (Ferguson Lake) and the nearby Spawning Lake, which support commercial sea-run Arctic char (Salvelinus alpinus) fisheries. Samples for nucleic acids were collected from the lakes along with limnological metadata. Microbial eukaryotes were identified with high-throughput amplicon sequencing targeting the V4 region of the 18S rRNA gene. Ciliates, dinoflagellates, chrysophytes, and cryptophytes dominated the lake assemblages. A Bray–Curtis dissimilarity matrix separated communities into under-ice and open-water clusters, with additional separation by superficial lake area. In all, 133 operational taxonomic units (OTUs) occurred either in all under-ice or all open-water samples and were considered “core” microbial species or ecotypes. These were further characterized as seasonal indicators. Ten of the OTUs were characteristic of all lakes and all seasons sampled. Eight of these were cryptophytes, suggesting diverse functional capacity within the lineage. The core open-water indicators were mostly chrysophytes, with a few ciliates and uncharacterized Cercozoa, suggesting that summer communities are mixotrophic with contributions by heterotrophic taxa. The core under-ice indicators included a dozen ciliates along with chrysophytes, cryptomonads, and dinoflagellates, indicating a more heterotrophic community augmented by mixotrophic taxa in winter.

Impacts of wastewater treatment plants on benthic macroinvertebrate communities in summer and winter

Treated effluent from municipal wastewater treatment plants (WWTPs) is a major source of contamination that can impact population size, community structure, and biodiversity of aquatic organisms. However, because the majority of field research occurs during warmer periods of the year, the impacts of wastewater effluent on aquatic communities during winter has largely been neglected. In this study, we assessed the impacts of wastewater effluent on aquatic benthic macroinvertebrate (benthos) communities along the effluent gradients of two WWTPs discharging into Hamilton Harbour, Canada, during summer and winter using artificial substrates incubated for 8 weeks. At the larger of the two plants, benthic macroinvertebrate abundance was higher and diversity was lower at sites downstream of the outfall compared to upstream sites in both seasons. Whereas at the smaller plant, the opposite was observed, abundance increased and diversity decreased with distance from the outfall in both seasons. While the impacts of wastewater on benthic communities were largely similar between seasons, we did detect several general seasonal trends – family diversity of macroinvertebrates was lower during winter at both WWTPs and total abundance was also lower during winter, but only significantly so at the smaller WWTP. Further, benthic macroinvertebrate community composition differed significantly along the effluent gradients, with sites closest and farthest from the outfall being the most dissimilar. Our contrasting results between the WWTPs demonstrate that plants, with different treatment capabilities and effluent-receiving environments (industrial/urban versus wetland), can dictate how wastewater effluent impacts benthic macroinvertebrate communities.

Composition and Dominance of Edible and Inedible Phytoplankton Predict Responses of Baltic Sea Summer Communities to Elevated Temperature and CO2.

Previous studies with Baltic Sea phytoplankton combining elevated seawater temperature with CO2 revealed the importance of size trait-based analyses, in particular dividing the plankton into edible (>5 and <100 µm) and inedible (<5 and >100 µm) size classes for mesozoopankton grazers. While the edible phytoplankton responded predominantly negative to warming and the inedible group stayed unaffected or increased, independent from edibility most phytoplankton groups gained from CO2. Because the ratio between edible and inedible taxa changes profoundly over seasons, we investigated if community responses can be predicted according to the prevailing composition of edible and inedible groups. We experimentally explored the combined effects of elevated temperatures and CO2 concentrations on a late-summer Baltic Sea community. Total phytoplankton significantly increased in response to elevated CO2 in particular in combination with temperature, driven by a significant gain of the inedible <5 µm fraction and large filamentous cyanobacteria. Large flagellates disappeared. The edible group was low as usual in summer and decreased with both factors due to enhanced copepod grazing and overall decline of small flagellates. Our results emphasize that the responses of summer communities are complex, but can be predicted by the composition and dominance of size classes and groups.

PSXVI-24 The succession of reindeer’ rumen symbiotic bacteria

Abstract Reindeer digestion is impossible without the symbiotic microorganisms that live in its rumen. The composition of plant fibers present in the diet of reindeer is characterized by an increased content of plant fiber, hemicellulose, lignin, and secondary lichen metabolites. The Arctic is characterized by extremely scarce food resources even in summer. In winter the nutritional value of the diet is further reduced. The digestion of such feeds is provided only by the enzyme systems of microorganisms that live in the rumen of ruminants. Therefore, the purpose of our study was to determine the changes occurring in the composition of the reindeer’ rumen bacterial community inhabiting the Nenets region of the Russian Arctic. Rumen contents were collected from 20 reindeer in winter and summer 2017. To identify the bacterial community, 16S rRNA sequencing was used on the MiSeq (Illumina). Statistical processing of the results of NGS using the PERMANOVA analysis showed that the rumen bacterial communities in winter and summer have significant differences (P = 0.001). Taxonomic analysis using the GreenGenes database showed that, in general, at the phylum level in the community, representatives of Firmicutes (29.98–52.67%) and Bacteroidetes (33.55–51.87%) dominated. Significant differences were shown for microorganisms associated with the fermentation of plant polysaccharides. In winter, a significant increase in bacteria of the genera Succiniclasticum (P &amp;lt; 0.001), Paraprevotellaceae (P &amp;lt; 0.001), Coprococcus (P &amp;lt; 0.001), Butyrivibrio (P &amp;lt; 0.001), Prevotella (P &amp;lt; 0.001), Ruminococcus (P &amp;lt; 0.001). Thus, there is a succession of the bacterial community of the reindeer rumen associated with the change of seasons, affecting minor groups of microorganisms. In turn, it is associated with the availability of various components of the diet and the predominance of more or less easily digestible substances in it. The study was supported by a grant of Russian Science Foundation Project No. 17-76-20026.