Diversity and interaction of bacterial and microeukaryotic communities in sediments planted with different submerged macrophytes: Responses to decabromodiphenyl ether

Plastic debris mediates bacterial community coalescence by breaking dispersal limitation in the sediments of a large river

Plastic debris has recently been proposed as a novel habitat for bacterial colonization, which can raise perturbations in bacterial ecology after burial in riverine sediments. However, community coalescence, as a prevalent process involving the interrelationships of multiple communities and their surrounding environments, has been rarely discussed to reveal the impact of the plastisphere on sedimentary bacterial community. This study analyzed the bacterial community in plastic debris and sediment along the Nujiang River, elucidating the role of the plastisphere in mediating community coalescence in sediments. Our results demonstrated that the plastisphere and sedimentary bacterial communities exhibited distinct biogeography along the river (r = 0.694, p < 0.01). Based on overlapped taxa and SourceTracker, the extent of coalescence between adjacent communities was in following orders: plastic-plastic (0.589) > plastic-sediment (0.561) > sediment-sediment (0.496), indicating the plastisphere promoted bacterial community coalescence along the river. Flow velocity and geographic distance were the major factors driving the plastisphere changes, suggesting that the plastisphere were vulnerable to dispersal. The null model and the neutral model provided additional support for the higher immigration ability of the plastisphere to overcome dispersal limitation, highlighting the potential importance of the plastisphere in community coalescence. Network analysis indicated the critical role of keystone species (Proteobacteria, Bacteroidetes, and Gemmatimonadetes) in mediating the coalescence between sedimentary bacterial community and the plastisphere. In summary, the plastisphere could mediate the coalescence of bacterial communities by overcoming dispersal limitation, which provides new perspectives on the plastisphere altering bacterial ecology in riverine sediments.

Long-term contamination of decabromodiphenyl ether reduces sediment multifunctionality: Insights from nutrient cycling, microbial ecological clusters, and microbial co-occurrence patterns

Despite the widespread detection of polybrominated diphenyl ethers in aquatic ecosystems, their long-term effects on sediment multifunctionality remain unclear. Herein, a 360-day microcosm experiment was conducted to investigate how decabromodiphenyl ether (BDE-209) contamination at different levels (0.2, 2, and 20 mg/kg dry weight) affects sediment multifunctionality, focusing on carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) cycling. Results showed that BDE-209 significantly increased sediment total organic carbon, nitrate, ammonium, available phosphorus, and sulfide concentrations, but decreased sulfate. Additionally, BDE-209 significantly altered key enzyme activities related to nutrient cycling. Bacterial community dissimilarity was positively correlated with nutrient variability. Long-term BDE-209 exposure inhibited C degradation, P transport and regulation, and most N metabolic pathways, but enhanced C fixation, methanogenesis, organic P mineralization, inorganic P solubilization, and dissimilatory sulfate reduction pathways. These changes were mainly regulated by microbial ecological clusters and keystone taxa. Overall, sediment multifunctionality declined under BDE-209 stress, primarily related to microbial co-occurrence network complexity and ecological cluster diversity. Interestingly, sediment C and N cycling had greater impacts on multifunctionality than P and S cycling. This study provides crucial insights into the key factors altering multifunctionality in contaminated sediments, which will aid pollution control and mitigation in aquatic ecosystems.

Combining effects of submerged macrophytes and lanthanum-modified bentonite on sediment enzyme activity: Evidence from mesocosm study

Lanthanum-modified bentonite (LMB) combined with submerged macrophytes (SM) has been a conventional means of eutrophication management in lakes in recent years, and is one of the most important methods for P removal. However, trends in nutrients and sediment enzymes at the water-sediment interface during this process have not been systematically assessed, and there are still some gaps in how abiotic properties drive changes in enzyme activity. Here, we show changes in aquatic environmental conditions under the action of different ratios of modified bentonite (0, 10%, 20%, and 30%) in combination with SM (Vallisneria natans, Potamogeton lucens, and Hydrilla verticillate) and quantify their effects on sediment enzyme activities. The results showed that the nutrient cycling at the water-sediment interface was facilitated by the combined effect of SM and LMB, which effectively reduced the overlying water nutrient concentration, increased the sediment enzyme activity and enhanced the N cycling process. Partial least squares structural equation model (PLS-SEM) showed that sediment parameters strongly influenced changes in enzyme activity, with NO3-N as the main controlling factors. Our study fills in the process of changing environmental conditions in lake water under geoengineered materials combined with macrophyte measures, especially the changes in biological properties enzyme activities, which contributes to a clearer understanding of nutrient fluxes during the management of eutrophication in lakes.

Deciphering the impact of decabromodiphenyl ether (BDE-209) on benthic foraminiferal communities: Insights from Cell-Tracker Green staining and eDNA metabarcoding

This study investigates the ecotoxicological effects of BDE-209, a persistent organic pollutant (POP) prevalent in Kuwait's coastal-industrial areas, on benthic foraminiferal communities. We conducted a mesocosm experiment in which we exposed benthic foraminiferal communities sampled from the coastal-industrial areas of Kuwait to a gradient of BDE-209 concentrations (0.01 to 20 mg/kg). The impact of exposure was assessed using live-staining and metabarcoding techniques. Despite the significantly different taxonomic compositions detected by the two techniques, our results show that BDE-209 significantly affects foraminiferal communities, with moderately high concentrations leading to reduced α-diversity and considerable taxonomic shifts in both molecular and morphological assemblages. At concentrations of 10 and 20 mg/kg, no living foraminifera were detected after 8 weeks, suggesting a threshold for their survival under BDE-209 exposure. The parallel responses of molecular and morphological communities confirm the reliability of both assessment methods. This study is the first to investigate the reaction of eukaryotic communities, specifically foraminifera, to POPs such as BDE-209, generating valuable insights that have the potential to enhance field studies and aid the refinement of sediment quality guidelines.

Immobilization of phosphorus in water-sediment system by iron-modified attapulgite, calcite, bentonite and dolomite under feed input condition: Efficiency, mechanism, application mode effect and response of microbial communities and iron mobilization

Four kinds of iron-based materials, i.e., iron-modified attapulgite, calcite, bentonite and dolomite (abbreviated as Fe-ATP, Fe-CA, Fe-BT and Fe-DOL, respectively) were prepared and used to immobilize the phosphorus in the system of overlying water (O-water) and sediment under the feed input condition, and their immobilization efficiencies and mechanisms were investigated. The influence of application mode on the immobilization of phosphorus in the water-sediment system by Fe-ATP, Fe-CA, Fe-BT and Fe-DOL was researched. The effects of Fe-ATP, Fe-CA, Fe-BT and Fe-DOL on the concentration of labile iron in the water-sediment system and the microbial communities in sediment were also studied. The results showed that the Fe-ATP, Fe-CA, Fe-BT and Fe-DOL addition all can effectively immobilize the soluble reactive phosphorus (SRP), dissolved total phosphorus (DTP) and diffusive gradients in thin-films (DGT)-labile phosphorus in O-water under the feed input condition, and also had the ability to inactivate the DGT-labile phosphorus in the top sediment. Although the change in the application mode from the one-time addition to the multiple addition reduced the inactivation efficiencies of SRP and DTP in O-water in the early period of application, it increased the immobilization efficiencies in the later period of application. Although Fe-ATP, Fe-CA, Fe-BT and Fe-DOL had a certain releasing risk of iron into the pore water, they had negligible risk of iron release into O-water. The addition of Fe-ATP, Fe-CA, Fe-BT or Fe-DOL reshaped the sediment bacterial community structure and can affect the microorganism-driven phosphorus cycle in the sediment. Results of this work suggest that Fe-ATP, Fe-CA, Fe-BT and Fe-DOL are promising phosphorus-inactivation materials to immobilize the phosphorus in the water-sediment system under the feed input condition.

Regulatory mechanisms of submerged macrophyte on bacterial community recovery in decabromodiphenyl ether contaminated sediment: Microbiological and metabolomic perspectives

Polybrominated diphenyl ether contamination in sediments poses serious threats to human health and ecological safety. Despite the broad application of submerged macrophytes for remediating pollutants, their regulatory influence on bacterial communities in contaminated sediments remains unclear. Herein, we analyzed the effects of decabromodiphenyl ether (BDE-209) and Hydrilla verticillata on sediment bacterial community and function using 16S rRNA gene sequencing and sediment metabolomics. Results showed that BDE-209 significantly inhibited sediment bacterial diversity and metabolic functions. It also enhanced bacterial interactions and altered both the bacterial community and metabolite composition. Uridine and inosine were critical metabolites that positively co-occurred with bacterial taxa inhibited by BDE-209. Notably, planting H. verticillata effectively alleviated the adverse impacts of BDE-209 by reducing its residuals, increasing the total organic carbon, and modifying metabolic profiles. Such mitigation was evidenced by enhancing bacterial diversity, restoring metabolic functions, and attenuating bacterial interactions. However, mitigation effectiveness depended on treatment time. Additionally, propionic acid, palmitic acid, and palmitoleic acid may facilitate the restoration of phylum Proteobacteria and class Planctomycetacia in H. verticillata planted sediment. Together, these findings improve understanding of BDE-209's impacts on aquatic ecosystems and provide valuable insights for ecological restoration using submerged macrophytes.