Proportion Of Cyanobacteria Research Articles

Linking sediment geochemistry with catchment processes, internal phosphorus loading and lake water quality

Research in the field of sediment geochemistry suggests potential linkages between catchment processes (land use), internal phosphorus (P) loading and lake water quality, but evidence is still poorly quantified due to a limited amount of data. Here we address the issues based on a comprehensive data set from 27 lakes in southern Finland. Specifically, we aimed at: 1) elucidating factors behind spatial variations in sediment geochemistry; 2) assessing the impact of diagenetic transformation on sediment P regeneration across lakes based on the changes in the vertical distribution of sediment components; 3) exploring the role of the sediment P forms in internal P loading (IL), and 4) determining the impact of IL on lake water quality. The relationship between sediment P concentration and field area percentage (FA%) was statistically significant in (mainly eutrophic) lakes with catchments that included more than 10 % of fields. We found that sediment iron-bound P (Fe-P) increased with increasing FA%, which agrees with the high expected losses from the cultivated areas. Additionally, populated areas increased the pool of sediment Fe-P. Internal P loading was significantly positively related to both sediment Fe-P and sediment organic P (Org-P). However, Org-P was not significant (as the third predictor) in models that had a trophic state variable as the first predictor and Fe-P as the second predictor. Further, the vertical profiles of sediment components indicated a role of diagenetic transformations in the long-term sediment P release, especially in lakes with deeper maximum depth and longer water residence time. Finally, IL was significantly positively correlated to water quality variables including phytoplankton biomass, its proportion of cyanobacteria, chlorophyll a concentration and trophic state index. Our findings suggest that reduction of P losses from the field and populated areas will decrease internal P loads and increase water quality through a reduced pool of Fe-P.

Cyanobacterial harmful bloom lipopolysaccharides: pro-inflammatory effects on epithelial and immune cells in vitro

Cyanobacterial harmful blooms (CyanoHABs) pose a global ecological problem, and their lipopolysaccharides (LPS) are among the bioactive compounds they release. Previous studies on CyanoHAB-LPS from single cyanobacterial species have shown varying bioactivities in different in vitro cell models. In this study, we isolated LPS from 19 CyanoHAB samples collected at 18 water bodies in the Czech Republic over two consecutive seasons. The proportions of cyanobacteria, Gram-negative bacteria (G-), and other bacteria in the biomass were determined by qPCR, while the cyanobacterial genera were identified using light microscopy. In vitro models of keratinocytes (HaCaT), the intestinal epithelium (co-culture of differentiated Caco-2 cells and peripheral blood mononuclear cells — PBMC), and PBMC alone were treated with isolated LPS at concentrations of 50, 100, and 1 µg/ml, respectively. The endotoxin activities of these concentrations were within the range measured in the aquatic environment. Approximately 85–90% of the samples displayed biological activity. However, the potency of individual LPS effects and response patterns varied across the different in vitro models. Furthermore, the observed activities did not exhibit a clear correlation with the taxonomic composition of the phytoplankton community, the relative share of microbial groups in the biomass, endotoxin activity of the LPS, or LPS migration and staining pattern in SDS-PAGE. These findings suggest that the effects of CyanoHAB-LPS depend on the specific composition and abundance of various LPS structures within the complex environmental sample and their interactions with cellular receptors.

Effect of Flocks of Anseriform Birds on Seston and Phytoplankton in Lakes of the Taimyr Peninsula

The effect of molting anseriform birds on the structure and elemental composition of phytoplankton (seston) has been assessed in 20 Arctic lakes of the Taimyr Peninsula. In lakes (part of the lake) inhabited by ~50–700 birds of six species, the average stoichiometric ratio N : P (mol : mol) was statistically significantly lower than in lakes without anseriforms: 15.8 ± 1.4 and 22.4 ± 2.7, respectively. There was also a tendency of higher average specific electrical conductivity in the lakes with the birds, 113 ± 32 µS/cm, when compared with those without anseriforms, 60 ± 18 µS/cm. The differences could be explained with high probability by the effect of guanotrophication, namely, by a flow in water of metabolites of molting anseriforms. The total biomass of phytoplankton and proportions of algal taxa and cyanobacteria in the total biomass did not differ statistically significantly in lakes with and without molting anseriforms. Therefore, under guanotrophication, the main threat of eutrophication was absent: an increase of biomass of cyanobacteria, causing the nuisance “bloom” of water. Moreover, an opposite tendency occured: in lakes with molting anseriforms, the proportion of cyanobacteria in total biomass of phytoplankton was on average lower than that in lakes without the birds, 16.2 ± 5.3% and 30.8 ± 9.3%, respectively. Thus, a hypothesis was confirmed that artificial guanotrophication should be regarded as a suitable ecotechnology for the increase of productivity of oligotrophic Arctic lakes.

Spatio-temporal dynamics of phytoplankton in a diversion reservoir and the major influencing factors: taxonomic versus functional groups classification.

Identifying factors affecting phytoplankton dynamics is crucial to the management of aquatic ecosystems. A lot of scholars have conducted intensive studies on phytoplankton in lake or reservoirs, but not many studies have been conducted on diversion reservoirs. To explore the seasonal and spatial variation of phytoplankton communities and their relationship with environmental factors in the context of water diversion, a case study was carried out at XiKeng (XK) reservoir in South China. In this study, month-by-month water samples and phytoplankton were collected from this reservoir from December, 2021, to July, 2022. The results showed that the phytoplankton community was characterized by significant spatial and temporal variations. There were significant differences in phytoplankton abundance and structure in the reservoirs in terms of time. The abundance of phytoplankton cells and the proportion of Cyanobacteria in the reservoir showed a trend of increasing from autumn to spring and then decreasing from spring to summer, while the functional group evolved from S1 in autumn to SN in spring and summer. The abundance of phytoplankton was influenced by the dynamic water division and the characteristics of the reservoir itself, resulting in a spatial distribution characteristic of AIII > AII > AI. Water temperature (WT) and nutrients were the key factors driving the changes in phytoplankton abundance and community structure in the reservoir. These findings will deepen our understanding of the spatial and temporal dynamics of phytoplankton community structure in diversion reservoirs and provide a basis for freshwater water ecological management strategies.

Microecological health assessment of water environment and sediment based on metagenomics: a case study of Guixi River in Chongqing, China.

River sediment is vital in containing water pollution and strengthening water remediation. This paper has conducted a study on the microecological health assessment of the sediment and water body of Guixi River in Dianjiang, Chongqing, China, using metagenomics sequencing and microbial biological integrity index (M-IBI) technology. The analysis of physical and chemical characteristics shows that the concentration of TN varies from 2.62 to 9.76mg/L in each sampling section, and the eutrophication of the water body is relatively severe. The proportion of Cyanobacteria in the sampling section at the sink entrance is higher than that of other sites, where there are outbreaks of water blooms and potential hazards to human health. The dominant functions of each site include carbon metabolism, TCA cycle, and pyruvate metabolism. In addition, the main virulence factors and antibiotic resistance genes in sediment are Type IV pili (VF0082), LOS (CVF494), MymA operon (CVF649), and macrolide resistance genes macB, tetracyclic tetA (58), and novA. Correlation analysis of environmental factors and microorganisms was also performed, and it was discovered that Thiothrix and Acidovorax had obvious gene expression in the nitrogen metabolism pathway, and the Guixi River Basin had a self-purification capacity. Finally, based on the microecological composition of sediment and physical and chemical characteristics of the water body, the health assessment was carried out, indicating that the main pollution area was Dianjiang Middle School and the watershed near the sewage treatment plant. The findings should theoretically support an in-depth assessment of the water environment's microecological health.

Spatial variation of summer microphytoplankton and zooplankton communities related to environmental parameters in the coastal area of Djerba Island (Tunisia, Eastern Mediterranean)

In the present study, we investigated the effects of pollution and anthropization on the summer distribution of phyto-zooplanktoncommunities in relation to environmental factors in the coastal zone of DjerbaIsland. On the basis of chemical factors, theDjerba coasts can be divided into two parts: the Western Area (WA), characterized by high values of nitrogen forms of nutrients,with higher N/P ratio, and the Eastern Area (EA), poorer in inorganic nitrogen with an N/P ratio lower than the Redfield ratio (16).Strong differences in terms of plankton communities were also observed between these two areas. Bacillariophyceae was the most important microphytoplankton group in the WA whereas the proportion of Cyanobacteria was higher in the EA. High Cyanobacteria abundance in the EA may be linked to high DIP concentration. In the WA, the Bacillariophyceae Chaetoceros, Coscinodiscus, Grammatophora, Navicula and Pinnularia reached high abundance in relation with their good adaptability to adverse conditions. Copepods were the most abundant zooplankton present in the WA (54–100% of total zooplankton abundance), whereas other zooplankton were always dominant (60–90%) in the EA. The small pollution-tolerant Calanoid copepod Paracalanus parvus was dominant in the WA, illustrating its affinity for highly eutrophic sites. Despite human pressure and industrial activities, the coastal waters of Djerba showed a wide diversity of microphytoplankton and zooplankton.

Relationships between biomass of phytoplankton and submerged macrophytes and physicochemical variables of water in Lake Caohai, China: Implication for mitigation of cyanobacteria blooms by CO2 fertilization

Reducing nutrient input in aquatic ecosystems has been widely recognized as a way to mitigate eutrophication. The paradigm of nutrient limitation by N and P is pervasively accepted, without considering the possibility of C limitation. However, our assumption that C might affect the aquatic biological composition, lacks fieldwork support. We tested the co-limitation of C/N/P on the growth of submerged macrophytes and phytoplankton in the Caohai Lake, a typical shallow karst lake in southwestern China. This study documented the seasonal variations in the concentration and comparative availability of nutrients C/N/P, in addition to physicochemical parameters, submerged macrophytes biomass, and phytoplankton composition in the lake. Our results show that dissolved inorganic carbon plays a substantial role in enhancing the primary production of phytoplankton and macrophytes, which suggests that primary production can be suppressed not only by P and/or N (as generally believed) but also by C, owing to the unique physicochemical characteristics that prevail in typical karst regions. Additionally, submerged macrophytes have been found to inhibit phytoplankton growth. Further analysis showed that the proportion of Cyanobacteria over Chlorophyta and Bacillariophyta throughout the year was reduced at dissolved carbon dioxide/total nitrogen (CO2/TN) ratios (>0.2) and dissolved carbon dioxide/total phosphorus (CO2/TP) ratios (>10) in this study. Isotopic evidence further indicated that the abundance of Cyanobacteria was reduced when CO2 >30 µmol/L. In summary, the combined results suggest that when controlling N and P, CO2 fertilization may significantly affect both the growth and composition of phytoplankton communities/submerged macrophytes and carbon sequestration in karst surface water ecosystems. This implies a new “paradigm” in the mitigation of cyanobacteria blooms by adding more CO2 to aquatic ecosystems with low pCO2, during which carbon sequestration may also be enhanced.

Relationship between community composition and water infiltration of biological soil crusts in the hilly Loess Plateau, China

Biological soil crusts (biocrusts) are the mixed community composed of different ratios of cyanobacteria, mosses, and lichens at the slope scale in the Hilly Loess Plateau region. Biocrusts significantly affect water infiltration in this area. The relationship between infiltration rate and community structure of mixed biocrusts is unknown, which would hinder the assessment of soil permeability of biocrusts at the slope scale. We measured the stable infiltration rate of cyanobacteria, moss, and mixed biocrusts with different proportions of cyanobacteria and moss including moss coverage of <15%, 15%-30%, 30%-45%, 45%-60% and >60%, respectively. The principal component analysis and path analysis were used to understand the influencing factors of stable infiltration rate of mixed biocrusts, and to clarify the relationship between the stable infiltration rate and the community structure of mixed biocrusts. The results showed that the saturated hydraulic conductivity of cyanobacteria and moss crusts was 0.66 mm·min-1 and 2.40 mm·min-1, respectively. The stable infiltration rates of mixed biocrusts with moss coverage <15% to >60% were 0.80-2.30 mm·min-1. The stable infiltration rate of mixed biocrusts at the slope scale depended on moss coverage and its improvement on soil pore structure, with the correlation coefficients being 0.636 (P=0.011) and 0.835 (P=0.000) respectively. Herein, the saturated hydraulic conductivity and coverage of cyanobacteria and moss confirmed the weighted prediction of water infiltration volume (y) i.e., a significant correlation (r=0.945) with the measured water infiltration volume (x) of mixed biocrusts. The linear fitting of measured and predicted water infiltration volume of mixed biocrusts was y=0.85x (R2=0.98, P<0.05). This study clarified the relationship between water infiltration of mixed biocrust community composition and individual biocrust composition, which provided a scientific basis for accurately evaluating the hydrological process of biocrusts in this area.

Impacts of nutrient loading and fish grazing on the phytoplankton community and cyanotoxin production in a shallow tropical lake: Results from mesocosm experiments.

Given the increasing eutrophication of water bodies in Africa due to increasing anthropogenic pressures, data are needed to better understand the responses of phytoplankton communities to these changes in tropical lakes. These ecosystems are used by local human populations for multiple purposes, including fish and drinking water production, potentially exposing these populations to health threats if, for example, an increase in toxic cyanobacterial blooms is associated with increasing eutrophication. To test the short‐term response of the phytoplankton community to the addition of nutrients (phosphorus and nitrogen, alone or in combination) and Nile tilapia, we developed an in situ mesocosm experiment in a freshwater lagoon located near Abidjan (Ivory Coast). We found that phytoplankton growth (estimated by chlorophyll‐a quantification) was highly stimulated when both nitrogen and phosphorus were added, while there was no clear evidence for such colimitation by these two nutrients when considering their concentrations in the lagoon. Phytoplankton growth was accompanied by significant changes in the diversity and composition of this community and did not lead to an increase in the proportions of cyanobacteria. However, the addition of fish to some mesocosms resulted in a drastic decrease in phytoplankton biomass and a dominance of chlorophytes in this community. Finally, these experiments showed that the addition of nitrogen, alone or combined with phosphorus, stimulated microcystin production by cyanobacteria. In addition, no evidence of microcystin accumulation in the fish was found. Taken together, these data allow us to discuss strategies for controlling cyanobacterial blooms in this tropical ecosystem.

Effects of the Invasive Fish Species Ameiurus nebulosus on Microbial Communities in Peat Pools

Disturbances in the functioning of peatlands, due to growing human impact, climate change and the appearance of alien invasive species, are becoming increasingly common. Analysis of trophic relationships in the predator (invasive alien species)–prey system is extremely important for understanding the functioning of peat pools—small water bodies formed in peatlands by peat extraction. These issues are, as yet, very little understood. The aim of this study was to examine the impact of Ameiurus nebulosus, an alien and invasive fish species dominant in these pools, on the microbial communities and small metazoa (phycoflora, bacteria, heterotrophic flagellates, ciliates, and crustaceans) in peat pools. The laboratory experiment included two groups of treatments simulating natural conditions: treatments without fish and treatments with brown bullhead. The water temperature was manipulated as well. The presence of brown bullhead in combination with climate changes was shown to cause a change in the structure of microbial communities. This is reflected in a decrease in the abundance of planktonic crustaceans and an increase in ciliates. The overlapping effects of alien species and gradual climate warming may intensify the eutrophication of peatland ecosystems and the increase in the proportion of cyanobacteria, thereby affecting the carbon cycle in these ecosystems.

Detecting and modeling changes in a time series of proportions

We propose a framework to detect and model shifts in a time series of continuous proportions, that is, a vector of proportions measuring the parts of a whole. By reparameterizing the shape of a Dirichlet distribution, we can model the location and scale separately through generalized linear models. A hidden Markov model allows the coefficients of the generalized linear models to change, thus allowing for the time series to undergo multiple regimes. This framework allows a practitioner to adequately model seasonality, trends, or include covariate information as well as detect change points. The model’s behavior is studied via simulation and through the analysis of lake phytoplankton data from 1992 through 2012. Our analyses demonstrate that the model can be effective in detecting and modeling changes in a time series of proportions. Pertaining to the phytoplankton data, the overall biomass has grown with some changes to the community level dynamics occurring circa 2000. Specifically, the proportion of cyanobacteria appears to have increased to the detriment of diatoms.

Effects of suspended ecological beds on phytoplankton community structure in Baiyangdian Lake, China

To address the issues of submerged vegetation restoration in the deep-water area of Baiyangdian Lake, a type of suspended ecological bed was developed, which was constructed with aquatic plants, ropes and supporting poles. The depth of a suspended ecological bed could be adjusted based on the water level. From July to November 2019, the phytoplankton community structure in the water around the suspended beds was continually monitored, and the effects of the submerged plants present in the suspended beds on the phytoplankton community structure in the deep-water area of the lake were studied. The results showed that Myriophyllum spicatum L. grew well in the suspended beds, with 95% survival after 60 d. The maximum biomass was reached in 55 d, and the water surface coverage reached 23%. There were 71 species of phytoplankton belonging to seven phyla in the water surrounding the suspended ecological beds. Over half (36 species) were members of Prochlorophyta, and the average density and biomass of phytoplankton gradually decreased month by month. The proportion of cyanobacteria in the community showed a downwards trend, while the proportions of other phytoplankton phyla showed upwards trends. The annual average Shannon–Wiener diversity index was 0.88, the annual average Pielou evenness index was 0.32, and the annual average Margalef richness index was 1.21. The Shannon–Wiener diversity index and Pielou's evenness index both showed increasing trends. This comprehensive analysis shows that planting submerged plants in suspended beds can improve the phytoplankton community structure of the surrounding water and increase the biodiversity of phytoplankton, making this an effective measure for restoring submerged vegetation in algae-dominated northern lakes.

Effects of zinc and iron on the abundance of Microcystis in Lake Taihu under green light and turbulence conditions.

Trace element is one of the important factors affecting the growth of Microcystis. The effects of zinc (0.4mg/L) and iron (2mg/L) on the abundance of Microcystis in Lake Taihu were investigated under continuous turbulence and green light conditions in a microcosm experiment. The study results showed that the abundance of Microcystis in the zinc treatment and the iron treatment group was 8.30% and 214% of that in the control group at the end of the experiment, respectively. The proportion of Cyanobacteria in the total phytoplankton biomass in the control, iron treatment, and zinc treatment group decreased from 99.99% at the beginning of the experiment to 13%, 18%, and 1% at the end of the experiment, respectively. At the end of the microcosm experiment, the phytoplankton community was dominated by Bacillariophyta in the control group, accounting for 63%, but it was dominated by Chlorophyta in the zinc treatment and the iron treatment group, accounting for 89% and 42%, respectively. The study results showed that under green light and turbulence, 0.4mg/L zinc remarkably decreased the abundance of Microcystis, but 2mg/L iron effectively increased the number of Microcystis and other algae. This research results provided a new idea for controlling Microcystis blooms.

Phytoplankton settling quality has a subtle but significant effect on sediment microeukaryotic and bacterial communities

In coastal aphotic sediments, organic matter (OM) input from phytoplankton is the primary food resource for benthic organisms. Current observations from temperate ecosystems like the Baltic Sea report a decline in spring bloom diatoms, while summer cyanobacteria blooms are becoming more frequent and intense. These climate-driven changes in phytoplankton communities may in turn have important consequences for benthic biodiversity and ecosystem functions, but such questions are not yet sufficiently explored experimentally. Here, in a 4-week experiment, we investigated the response of microeukaryotic and bacterial communities to different types of OM inputs comprising five ratios of two common phytoplankton species in the Baltic Sea, the diatom Skeletonema marinoi and filamentous cyanobacterium Nodularia spumigena. Metabarcoding analyses on 16S and 18S ribosomal RNA (rRNA) at the experiment termination revealed subtle but significant changes in diversity and community composition of microeukaryotes in response to settling OM quality. Sediment bacteria were less affected, although we observed a clear effect on denitrification gene expression (nirS and nosZ), which was positively correlated with increasing proportions of cyanobacteria. Altogether, these results suggest that future changes in OM input to the seafloor may have important effects on both the composition and function of microbenthic communities.

The impacts of extreme climate on summer-stratified temperate lakes: Lake Søholm, Denmark, as an example

The global surface temperature has increased by about 0.74°C over the past 100 years, and the frequency of extreme weather has increased as well. We used the state-of-the-art complex, dynamic, mechanistic model GOTM-FABM-PCLake to quantify the impacts of extreme summer warming on a summer-stratified temperate Danish lake. Simulated values of all calibrated parameters (water temperature, DO, NO3, NH4, TN, PO4, TP and Chl.-a) agreed well with observed values over the whole calibration and validation period and generally exhibited the same seasonal dynamics and inter-annual variations as the monitoring data. A series of climate scenarios with different summer heat wave frequencies and duration were set up to quantify the effects on the ecosystem state of the lake. Our simulations showed that summer surface mean TN will decrease with rising summer heat wave frequencies, while summer surface mean TP and Chl.-a and the biomass and proportion of cyanobacteria will increase. Following a summer heat wave, the lake approached baseline conditions in the autumn, but with increasing frequency of heatwaves the recovery period increased. Our results suggest that compliance with existing legislation, such as EU’s Water Framework Directive, will become increasingly challenging in a future scenario with increased temperatures and more frequent heatwaves.

Impact assessment of water diversion project on urban aquatic ecological environment

Water diversion project (WDP) plays an increasingly important role in improving the water quality of urban rivers along the Yangtze Delta megalopolis of China. However, their effects on the water ecological environment has generated extensive debates. Water quality variables and phytoplankton community dynamics were tracked and monitored during the summer–winter water diversions to explore the comprehensive effects of WDP on the urban aquatic ecological environment. The multi-index comprehensive evaluation model (MCEM) was adopted for further quantitative assessment, together with a newly proposed progressive degree calculation model (PDCM), which broke the limitations of the traditional ways using Markov chains. The grade evaluation was based on the Environmental Quality Standards for Surface Water (GB 3838–2002) in China. The comprehensive water quality evaluated by MCEM was improved with the largest improvement of two grades after WDP in summer, which on the contrary was worsened because of water transfers in winter by a maximum decrement of one grade. The PDCM evaluation on water quality index indicated that WDP has improved the water quality to some extent but without grade changes. Also, the proportion of Cyanobacteria and Chlorophyta decreased in the phytoplankton community of the three rivers after WDP, whereas the proportion of Bacillariophyta increased, indicating that the community structure was more inclined to the Yangtze River. The comprehensive water pollution situation evaluated by MCEM was improved with the largest improvement from middle pollution to lower pollution (one grade) because of water transfers. The changes in aquatic biological indexes evaluated by PDCM were more obvious than those of water quality indexes, which were improved by one grade.

The effect of hydrodynamics on the succession of autotrophic and heterotrophic organisms of biofilms in river ecosystems.

Biofilms were cultivated for a 68-day period under different hydrodynamic conditions, and the effect of hydrodynamics on the succession of autotrophic and heterotrophic organisms of biofilms was investigated. Five obvious stages were observed during biofilm formation. At Stage I, the attachment of algae was delayed, especially under turbulent conditions. After Stage II, algal density and heterotrophic biomass of biofilms increased, which were obvious under turbulent flow. Therefore, the algal density and heterotrophic biomass of biofilms were largest under turbulent condition, followed by laminar condition, and then transitional condition. Diatoms were dominant in all flumes and were most abundant under turbulent conditions. The proportion of cyanobacteria was highest under laminar conditions. The ratio of aerobic to anaerobic bacteria decreased and their co-existence could facilitate the nitrification and denitrification in the biofilm. The ratio of monounsaturated fatty acids to saturated fatty acids was highest under turbulent conditions on the 15th day. While the ratio was highest under laminar condition on the 48th day, the high ratio indicates the high ability of biofilm to obtain nutrients, which affect the growth of algae. The regulation of hydrodynamics is a useful technology which can affect the growth of the microorganisms of biofilm, and further improve water quality.

Effects of changing phytoplankton species composition on carbon and nitrogen uptake in benthic invertebrates

AbstractPelagic primary production is the main input of organic energy for benthic production below the photic zone. In the Baltic Sea, spring phytoplankton blooms are dominated by diatoms that sink out rapidly and export nutritionally favorable matter to benthic secondary production, while the summer blooms have more variable sedimentation rates and nutritional profile. Changes in phytoplankton species composition and bloom dynamics, as a consequence of climate change and eutrophication are reducing high quality diatoms reaching the benthic fauna, while promoting cyanobacteria. Here, we test uptake and assimilation of changing phytoplankton composition for three common benthic invertebrates, a clam, an amphipod and a polychaete under varying degrees of spring‐bloom associated diatoms (Skeletonema costatum) and summer‐bloom associated cyanobacteria (Nodularia spumigena). The phytoplankton were labeled with stable isotopes (15N and 13C, respectively) in order to trace assimilation in consumers' tissues. We found that all three macrofauna species fed on both diatoms and cyanobacteria. A linear pattern was found for all three species in assimilation of carbon and nitrogen from diatoms, with increasing assimilation associated with higher proportion of diatoms. There was no clear pattern found between proportion of cyanobacteria and assimilation of carbon and nitrogen for any of the species. This study shows that the investigated macrofaunal species display a selective feeding behavior with preference for spring‐bloom associated diatoms. Thus, changes in phytoplankton bloom composition are likely affecting benthic species composition and production.

Metagenome Across a Geochemical Gradient of Indian Stone Ruins Found at Historic Sites in Tamil Nadu, India.

Although stone surfaces seem unlikely to be habitable, they support microbial life. Life on these surfaces are subjected to many varying harsh conditions and require the inhabitants to exhibit resistance to environmental factors including UV irradiation, toxic metal exposure, and fluctuating temperatures and humidity. Here we report the effect of hosting stone geochemistry on the microbiome of stone ruins found in Tamil Nadu, India. The microbial communities found on the two lithologies, granite and granodiorite, hosted distinct populations of bacteria. Geochemical composition analysis of sampled stones revealed quartz mineral content as a major driver of microbial community structure, particularly promoting community richness and proportions of Cyanobacteria and Deinococcus-Thermus. Other geochemical parameters including ilmenite, albite, anorthite, and orthoclase components or elemental concentrations (Ti, Fe, Mn, Na, and K) also influenced community structure to a lesser degree than quartz. Core members of the stone microbiome community found on both lithologies were also identified and included Cyanobacteria (Chroococcidiopsaceae and Dapisostemonum CCIBt 3536), Rubrobacter, and Deinococcus. A cluster of taxa including Sphingomonas, Geodermatophilus, and Truepera were mostly found in the granodiorite samples. Community diversity correlated with quartz mineral content in these samples may indicate that the microbial communities that attach to quartz surfaces may be transient and regularly changing. This work has expanded our understanding of built-stone microbial community structure based on lithology and geochemistry.

Effect of water warming on the structure of biofilm-dwelling communities

Abstract Water warming, either resulting from global or local drivers, is of growing concern for aquatic environments. Changes in thermal regimes may alter the functioning and the trophic dynamics of river ecosystems as most aquatic biota like micro-algae, invertebrates, or fish are poikilotherms. Because biofilms integrate basal and intermediate components of aquatic food webs, examination of their responses to warming should contribute to a better understanding of the effects of ongoing climate change on river ecosystems. In this study, we considered sites that were or were not exposed directly to thermal effluents from a nuclear power plant as “in situ laboratories” of the effect of climate change and water warming. To compare the structure of algal and invertebrate communities dwelling in epilithic biofilms subjected to different thermal regimes in the Garonne River, sets of concrete tiles were placed in the river and the biofilm growing on these standard substrates was sampled after two months of colonisation. The site located within the thermal plume directly downstream of the thermal effluents showed warmer average water temperature (mean ΔT of about 1.5 °C over the study period) and greater daily temperature fluctuations in comparison to the control site. Algal and invertebrate biomass did not differ significantly, but the structure of communities differed markedly between sites. At the heated site, the proportion of cyanobacteria was higher, while there were fewer micro-crustaceans and larvae of insects and bivalves. However, the population of chironomids showed a greater proportion of relatively large individuals. Interestingly, nematodes were more abundant, and their communities comprised more species at the heated site. Their feeding-types were also more diverse showing a greater proportion of algivores, large-sized omnivorous and predatory species. Changes in the abundance and age structure further showed that some bacterivore species, such as Eumonhystera vulgaris, thrived especially well at the heated site, whereas another bacterivore, Monhystrella paramacrura, thrived well at the control site. In the context of climate change, our results highlight that warmer and more fluctuating water temperatures have the potential to alter the body-size spectrum, species composition, distribution of feeding specialisations and age structure within biofilm-dwelling communities.