In coastal lagoons, marine benthic macrophyte meadows can be an important element in the resistance to eutrophication of the ecosystem, as they can function as temporary nitrogen sinks, limiting the ...availability of this nutrient for opportunistic organisms. The role of nitrogen sinks for two dominant macrophyte species of Mediterranean coastal lagoons, the seagrass Cymodocea nodosa and the seaweed Caulerpa prolifera, was analysed by two different approaches: (i) studying nitrate (NOsub.3 sup.-) and ammonium (NHsub.4 sup.+) uptake kinetics of aboveground tissues in a laboratory and (ii) estimating nitrogen stocks and demands of meadows under natural conditions. The studies were carried out in the coastal lagoon of the Mar Menor, which has been subjected to high anthropogenic nitrogen inputs for decades. While both macrophytes were efficient in exploiting NHsub.4 sup.+ from the water column, only C. prolifera showed a high NOsub.3 sup.- uptake capacity. Large N pools in the C. nodosa and C. prolifera meadows of the Mar Menor were detected, suggesting that these habitats may have the potential to be essential reservoirs for this nutrient. However, the major role of belowground tissues of the seagrasses in nitrogen accumulation may determine important differences between the two species in temporary N storage and sequestration. The data on N demands for the meadows of both macrophytes in the Mar Menor suggest an important contribution of these habitats in controlling the inputs of this nutrient into the lagoon. We conclude that C. nodosa and C. prolifera meadows can play a key role as a sink for dissolved inorganic nitrogen in temperate coastal lagoons, being an important mechanism of resistance to eutrophication.
Dense aggregations of serpulid worms were encountered in the Daymaniyat Islands (Gulf of Oman) from 10 to 20 m depth, over the period January–March, 2021. The species responsible for these ...aggregations belongs to the Filograna/Salmacina-complex (Annelida: Serpulidae). This species has been present in the area and observed along the Oman coastline, but high-density aggregates like this have not been reported before. The most probable cause of the aggregations, supported by field observations and Aqua-MODIS satellite data, was natural eutrophication with a subsequent algal bloom linked to the local winter monsoon. This observation emphasises the importance of documenting biodiversity and dynamics of reef communities along the Oman coastline.
The eutrophication of lowland lakes in Europe by excess nitrogen (N) and phosphorus (P) is severe because of the long history of land‐cover change and agricultural intensification. The ecological and ...socio‐economic effects of eutrophication are well understood but its effect on organic carbon (OC) sequestration by lakes and its change overtime has not been determined. Here, we compile data from ~90 culturally impacted European lakes ~60% are eutrophic, Total P (TP) >30 μg P l−1 and determine the extent to which OC burial rates have increased over the past 100–150 years. The average focussing corrected, OC accumulation rate (C ARFC) for the period 1950–1990 was ~60 g C m−2 yr−1, and for lakes with >100 μg TP l−1 the average was ~100 g C m−2 yr−1. The ratio of post‐1950 to 1900–1950 C AR is low (~1.5) indicating that C accumulation rates have been high throughout the 20th century. Compared to background estimates of OC burial (~5–10 g C m−2 yr−1), contemporary rates have increased by at least four to fivefold. The statistical relationship between C ARFC and TP derived from this study (r2 = 0.5) can be used to estimate OC burial at sites lacking estimates of sediment C‐burial. The implications of eutrophication, diagenesis, lake morphometry and sediment focussing as controls of OC burial rates are considered. A conservative interpretation of the results of the this study suggests that lowland European meso‐ to eutrophic lakes with >30 μg TP l−1 had OC burial rates in excess of 50 g C m−2 yr−1 over the past century, indicating that previous estimates of regional lake OC burial have seriously underestimated their contribution to European carbon sequestration. Enhanced OC burial by lakes is one positive side‐effect of the otherwise negative impact of the anthropogenic disruption of nutrient cycles.
The use of lanthanum (La)-based materials for phosphate removal from water and wastewater has received increasing attention. However, challenges remain to enhance phosphate sorption capacities and ...recover La-based sorbents. In this study, magnetic La(OH)3/Fe3O4 nanocomposites with varied La-to-Fe mass ratios were synthesized through a precipitation and hydrothermal method. Based upon preliminary screening of synthesized La(OH)3/Fe3O4 nanocomposites in terms of phosphate sorption capacity and La content, La(OH)3/Fe3O4 nanocomposite with a La-to-Fe mass ratio of 4:1 was chosen for further characterization and evaluation. Specifically, for these materials, magnetic separation efficiency, phosphate sorption kinetics and isotherm behavior, and solution matrix effects (e.g., coexisting ions, solution pH, and ionic strength) are reported. The developed La(OH)3/Fe3O4 (4:1) nanocomposite has an excellent magnetic separation efficiency of >98%, fast sorption kinetics of 30 min, high sorption capacity of 83.5 mg P/g, and strong selectivity for phosphate in presence of competing ions. Phosphate uptake by La(OH)3/Fe3O4 (4:1) was pH-dependent with the highest sorption capacities observed over a pH range of 4–6. The ionic strength of the solution had little interference with phosphate sorption. Sorption-desorption cyclic experiments demonstrated the good reusability of the La(OH)3/Fe3O4 (4:1) nanocomposite. In a real treated wastewater effluent with phosphate concentration of 1.1 mg P/L, 0.1 g/L of La(OH)3/Fe3O4 (4:1) efficiently reduced the phosphate concentration to below 0.05 mg P/L. Electrostatic attraction and inner-sphere complexation between La(OH)3 and P via ligand exchange were identified as the sorption mechanisms of phosphate by La(OH)3/Fe3O4 (4:1).
Display omitted
•La(OH)3/Fe3O4 nanocomposites with high sorption capacity of 83.5 mg P/g are obtained.•La(OH)3/Fe3O4 exhibits 98% separation efficiency and fast sorption kinetics (30 min).•Highly efficient removal of phosphate from real wastewater effluent is achieved.•Electrostatic attraction and ligand exchange contribute to high phosphate sorption.
Here we report the long-term (13-year) dynamics of surface pCO.sub.2 and its response to episodic eutrophication and acidification events in two contrasting tropical coastal lakes, one clear-water ...and the other humic. A short-term nutrient addition experiment was also conducted in mesocosms in the humic lake where in situ eutrophication was moderate. Our objective was to elucidate the response of pCO.sub.2 to interannual changes in key limnological conditions, such as nutrient concentrations and pH. The humic waters showed a median pCO.sub.2 almost ninefold higher across the 13-year study than the clear waters, supporting pCO.sub.2 values about tenfold above atmospheric equilibrium. Eutrophication of the clear-water lake resulted in a decrease in pCO.sub.2 to median values below atmospheric equilibrium, producing a strong sink for atmospheric CO.sub.2. In contrast, pCO.sub.2 increased by over tenfold in both lakes during the acidification phase, resulting in very large CO.sub.2 emissions to the atmosphere. Experimental nutrient additions in the humic lake showed a strong persistence of high pCO.sub.2. The extreme variability in pCO.sub.2 observed here might be a characteristic of tropical lakes and may have important consequences for regional carbon budgets.
The harmful algal bloom (HAB) species Pseudo-nitzschia multiseries is widely distributed worldwide and is known to produce the neurotoxin domoic acid, which harms marine wildlife and humans. Early ...detection and preventative measures are more critical than late management. However, the major challenge related to early detection is the accurate and sensitive detection of microalgae present in low abundance. Therefore, developing a sensitive and specific method that can rapidly detect P. multiseries is critical for expediting the monitoring and prediction of HABs. In this study, a novel assay method, recombinase polymerase amplification combined with lateral flow dipstick (RPA-LFD), is first developed for the detection of P. multiseries. To obtain the best test results, several important factors that affected the amplification effect were optimized. The internal transcribed spacer sequence of the nuclear ribosomal DNA from P. multiseries was selected as the target region. The results showed that the optimal amplification temperature and time for the recombinase polymerase amplification (RPA) of P. multiseries were 37 °C and 15 min. The RPA products could be visualized directly using the lateral flow dipstick after only 3 min. The RPA-LFD assay sensitivity for detection of recombinant plasmid DNA (1.9 × 10sup.0 pg/μL) was 100 times more sensitive than that of RPA, and the RPA-LFD assay sensitivity for detection of genomic DNA (2.0 × 10sup.2 pg/μL) was 10 times more sensitive than that of RPA. Its feasibility in the detection of environmental samples was also verified. In conclusion, these results indicated that the RPA-LFD detection of P. multiseries that was established in this study has high efficiency, sensitivity, specificity, and practicability. Management measures made based on information gained from early detection methods may be able to prevent certain blooms. The use of a highly sensitive approach for early warning detection of P. multiseries is essential to alleviate the harmful impacts of HABs on the environment, aquaculture, and human health.
Greenhouse gases (GHGs) have long received public attention because they affect the Earth's climate by producing the greenhouse effect. Freshwaters are an important source of GHGs, and the ...enhancement in their eutrophic status affects GHG emissions. Along with the increasing eutrophication of water bodies, the relevant quantitative and qualitative studies of the effects of freshwater eutrophication on GHG emissions have made substantial progress, particularly in the past 5 years. However, to our knowledge, this is the first critical review to focus on the role of freshwater eutrophication in GHG emissions. In this review, the emissions of common GHGs from freshwater are quantitatively described. Importantly, direct (i.e., dissolved oxygen, organic carbon, and nutrients) and indirect factors (i.e., dominant primary producer and algal blooms) affecting GHG emissions from eutrophic freshwater are systematically analyzed. In particular, the existence and significance of feedback loops between freshwater eutrophication and GHG emissions are emphasized considering the difficulties managing freshwater ecosystems and the Earth's climate. Finally, several future research directions as well as mitigation measures are described to provide useful insight into the dynamics and control of GHG emissions.
Display omitted
•Role of freshwater eutrophication on greenhouse gas emissions was reviewed.•Significance of freshwater as a source of greenhouse gases was quantitatively stated.•Factors affecting greenhouse gas emissions from eutrophic freshwaters were analyzed.•Feedback loops between freshwater eutrophication and gas emissions were emphasized.
PDF
