Alterations in the macrobenthic fauna from Guadarranque River (Southern Spain) associated with sediment-seawater acidification deriving from CO2 leakage

Taxonomic and functional structure of macrobenthic invertebrate communities and their response to environmental variables along the subbranches of the Nile River (rayahs), Egypt

Macrobenthic invertebrate communities serve as markers of anthropogenic stress in freshwater ecosystems. In this study, 17 sampling sites were selected from two Nile river subbranches (El-Rayah El-Behery and El-Rayah El-Nassery) and subjected to different anthropogenic influences to explore the ecological environment and characteristics of macrobenthos communities. Macrobenthos were studied using taxonomic diversity and biological trait analysis to investigate how human activity and variation in water quality affect their structure and function. A total of 37 taxa represented by 43,389 individuals were recognized. The communities are composed chiefly of Oligochaeta and aquatic insects. Multivariate statistical analyses found that the most influential environmental variables in the structural and functional community were sodium, dissolved oxygen, silicate, pH, calcium, and cadmium. At high levels of pollution, notably sewage and industrial pollution in the northern part of El-Rayah El-Behery, characteristics such as larger body size, detritus feeders, burrowers, and high tolerance to pollution predominated, whereas at low levels of pollution, features such as small body sizes, scraper and predator feeders, intolerant and fairly tolerant of pollution, and climber and swimmer mobility are predominant. The results confirm our prediction that the distribution of macroinvertebrate traits varies spatially in response to environmental changes. The diversity-based method distinguished impacted sewage and industrial sites from thermal effluent sites, while the trait-based approach illustrated an apparent variance between the ecological status of contaminated regions. Therefore, the biological features should be employed in addition to structural aspects for assessing the biodiversity of macroinvertebrate communities under environmental stressors.

Spatiotemporal correlations between water quality and microbial community of typical inflow river into Taihu Lake, China

Changxing River, which is a typical inflow river into Taihu Lake and occurs severe algae invasion, is selected to study the effect of different pollution sources on the water quality and ecological system. Four types of pollution sources, including the estuary of Taihu Lake, discharge outlets of urban wastewater treatment plants, stormwater outlets, and nonpoint source agricultural drainage areas, were chosen, and next-generation sequencing and multivariate statistical analyses were used to characterize the microbial communities and reveal their relationship with water physicochemical properties. The results showed that ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) were the main pollutants in Changxing River, especially at stormwater outlets. At the same time, the diversity of microbial communities was the highest in the summer, and dominant microbes included Proteobacteria (40.9%), Bacteroidetes (21.0%), and Euryarchaeota (6.1%). The results of BIOENV analysis showed that the major seasonal differences in the diversity of microbial community of Changxing river were explained by the combination of water temperature (T), air pressure (P), TP, and COD_Mn. From the perspective of different pollution types, relative abundances of Microcystis and Nostocaceae at the estuary of Taihu Lake were correlated positively with dissolved oxygen (DO) and pH, and relative abundances of Pseudomonas and Arcobacter were correlated positively with concentrations of TN and nitrate nitrogen (NO₃^--N) at stormwater outlets. This study provided a reference for the impact of pollution types on river microbial ecosystem under complex hydrological conditions and guidance for the selection of restoration techniques for polluted rivers entering the important lake.

The Application of the Environment Act 2021 Principles to Carbon Capture and Storage

Carbon Capture and Storage (CCS) is a new technology considered to have the potential to decarbonise economies. However, nationally and internationally the use of CCS has also been raising concerns about its potential global risks and adverse impacts on the environment. CCS was part of the discussions at the fourth United Nations Environment Assembly (UNEA) in March 2019 and in side-events in the 26th UN Climate Change Conference that took place in Glasgow in November 2021. The UK Government aims to deploy CCS at scale during the 2030s, subject to cost reduction. At the same time, the UK Government has recently enacted the Environment Act 2021, which provides a set of five environmental principles: the integration principle, the principle of preventative action, the precautionary principle, the rectification at source principle and the polluter pays principle. This work seeks to analyse the application of the UK environmental law principles to carbon capture and storage policies in the United Kingdom and its balance with other considerations. Given the concerns surrounding the use of CCS, the debate about its legality may arise in the United Kingdom and in other countries. To this end, this paper initially carries out a systematic review of CCS policy documents to discover the policy considerations that support the development of CCS. It then examines the application of the UK environmental law principles to CCS initiatives and its balance with other considerations, such as reduction of carbon emissions, security of energy supply, economic growth and technological leadership. In doing so, this paper aims at contributing to the debate surrounding recent technological developments that have been utilised to help address climate change and some of the legal challenges emerging through the use of CCS under UK environmental law.

Intraspecific variation in the response of the estuarine European isopod Cyathura carinata (Krøyer, 1847) to ocean acidification

In the present study the model isopod, Cyathura carinata were exposed to four pH_NIST treatments (control: 7.9; 7.5, 7, 6.5) in order to determine the tolerance and pH threshold value this estuarine species withstand under future acidification scenarios. Seawater acidification significantly affected the lifespan of C. carinata, where population density was remarkably reduced at the lowest pH treatment. The longevity, survivorship and swimming activity (related to the acquisition of energy) of these isopods decreased with decreasing pH. Furthermore, to determine the possible metabolic plasticity of this species, the swimming activity, the Na+/K + -ATPase activity (relevant for osmoregulation process), and the RNA:DNA ratio (an indicator of fitness) were measure from two populations of C. carinata, one inhabiting a stable environment (pH_NIST 7.5-8.0) and one inhabiting a fluctuating pCO₂ regimes (pH 3.3-8.5) subjected to three pH treatments (7.9, 7.0 and 6.5). The population from high fluctuating pCO₂ conditions showed capacity to withstand to pH 6.5, as well as higher longevity and metabolic plasticity, when compared with the population from the habitat with slight pCO₂ variation. These results indicate that Cyathura population from stable environments could be vulnerable to ocean acidification because it could trigger detrimental effects on its survival energy budget, and growth. However, ocean acidification has limited effect on the energy budget and survival of C. carinata population from highly variable habitats, suggesting that they are able to cope with the elevated energy demand. The difference showed between populations is likely an indication of genetic differentiation in tolerance to ocean acidification, possibly attributable to local adaptations, which could provide the raw material necessary for adaptation to future conditions. In addition, our results suggest that when assessing marine crustacean responses to changing environments on a global scale, variability in population and metabolic responses need to be considered.

Using a mesocosm approach to evaluate marine benthic assemblage alteration associated with CO2 enrichment in coastal environments

The effects of acidification related to the CO₂ enrichment in the coastal environments on marine macrobenthic abundance, diversity and richness were analyzed in a medium- term (21 days) using mesocosm experiments. Two sampling sites located in the Bay of Cadiz - SW, Spain were selected and tested at pH values ranged from 7.9 to 6.0 (± 0.1). Moreover, variations in the concentrations of metals in the sediment samples were analyzed at the end of each experiment. The results showed low variation in the concentrations of metals in the sediment among the pH treatments. A significant decrease (p < 0.05) in the abundance, diversity and richness of assemblages were measured between the control and the lowest pH level in both sampling sites tested in this study (Rio San Pedro and El Trocadero). The majority of species were found in all samples except in pH 6.0 which only two species were found (Hydrobia ulvae and Scrobicularia plana,) in Rio San Pedro sediment fauna. In general, the results of cluster analysis showed 60% and 40% similarity in all replicated tests in El Trocadero and Rio San Pedro of sediment fauna, respectively. The results of the Principal Component Analysis (PCA) showed that both sediment parameters and pH reduction can interfere in the benthic assemblage indices. Although the assemblages' indices have shown decreases only in the lower pHs, the organisms also could be impacted by chronic effects. Therefore, the extension of this study is important in order to improve the knowledge about the risks associated with CO₂ enrichment in on marine organisms.

What is the best endpoint for assessing environmental risk associated with acidification caused by CO2 enrichment using mussels?

Carbon capture and storage is a technology that has been widely determined to be one of the best choices for the short-term reduction of atmospheric CO₂ emissions. The aim of this study was to analyze the effects of CO₂ enrichment in the ocean on the mussel species Mytilus galloprovincialis using three different endpoints: mortality, embryo-larval development, and neutral red retention time assays (NRRT). Acute effects were found to be associated with a pH values of 6.0 while citotoxity effects and embryo-larval development were associated with a pH value of 7.0. The NRRT assay and embryo-larval development can be recommended as good endpoints for assessing the environmental risk associated with acidification by CO₂ enrichment because they provide sensitive responses on the effects of changes in seawater pH on mussels in a short period of time. Moreover, this study may support policymakers in finding appropriate solutions for the conservation of marine ecosystems.

Assessing the influence of ocean acidification to marine amphipods: A comparative study

CO₂ increases in the ocean may occur both by the capacity of CO₂ exchanges with its dissolved form between atmosphere and surface seawater as well by CO₂ leaks during the carbon capture and storage (CCS) process. The decrease in seawater pH may result in a reduction in the concentration of both hydroxide and carbonate (OH^- and CO₃^2-). The main aim of this work is to conduct an ecotoxicology comparative survey using two amphipod species from Europe and Brazil exposed to different acidification (CO₂) scenarios. For it, an integrative approach based on the weight of evidence was used for comparative proposes to identify the effects on the amphipods association with the acidification and with the related mobility of metals. The results demonstrate that the Ampelisca brevicornis species is more sensitive to pH reductions than the Hyale youngi species. Furthermore, this study has demonstrated that the CO₂ enrichment in aquatic ecosystems would cause changes on the mobility of certain metals (Zn, Cu and As). The results of Principal Component Analysis (PCA) showed that the dissolved Zn in overlying water was strongly correlated with the decrease in the pH and was associated with increased toxicity of the sediment to the exposed organisms, mainly for the A. brevicornis species from Spain. Nevertheless, similar results were found in relation to the mortality of amphipods in low pH values for all sediment tested. Concluding, it is highlighted the importance of comparative studies in different types of environment and improve the understood of the risks associated with the ocean acidification.

Comparative evaluation of sea-urchin larval stage sensitivity to ocean acidification

Changes in the marine carbonate system may affect various calcifying organisms. This study is aimed to compare the sensitivity of embryo-larval development of two species of sea urchins (Paracentrutos lividus and Lytechinus variegatus) collected and exposed to samples from different coastal zone (Spain and Brazil) to ocean acidification. The results showed that the larval stages are very sensitive to small changes in the seawater's pH. The larvae from P. lividus species showed to be more sensitive to acidified elutriate sediments than larvae from L. variegatus sea urchin. Furthermore, this study has demonstrated that the CO₂ enrichment in aquatic ecosystems cause changes on the mobility of the metals: Zn, Cu, Fe, Al and As, which was presented different behavior among them. Although an increase on the mobility of metals was found, the results using the principal component analysis showed that the pH reduction show the highest correlations with the toxicity and is the main cause of embryo-larval development inhibition. In this comparative study it is demonstrated that both species are able to assess potential effects of the ocean acidification related to CO₂ enrichment by both near future scenarios and the risk associated with CO₂ leakages in the Carbon Capture and Storage (CCS) process, and the importance of comparative studies in different zones to improve the understanding of the impacts caused by ocean acidification.

Estuarine sediment resuspension and acidification: Release behaviour of contaminants under different oxidation levels and acid sources

Carbon dioxide (CO₂) Capture and Storage (CCS) is a technology to reduce the emissions of this gas to the atmosphere by sequestering it in geological formations. In the case of offshore storage, unexpected CO₂ leakages will acidify the marine environment. Reductions of the pH might be also caused by anthropogenic activities or natural events such as acid spills and dredging operations or storms and floods. Changes in the pH of the marine environment will trigger the mobilisation of elements trapped in contaminated shallow sediments with unclear redox boundary. Trace element (As, Cd, Cr, Cu, Ni, Pb and Zn) release from anoxic and oxic estuarine sediment is analysed and modelled under different laboratory acidification conditions using HNO₃ (l) and CO₂ (g): acidification at pH = 6.5 as worst-case scenario in events of CO₂ leakages and acid spills, and acidification at pH = 7.0 as a seawater scenario under CO₂ leakages, acid spills, as well as sediment resuspension. The prediction of metal leaching behaviour appear to require sediment specific and site specific tools. In the present work it is demonstrated that the proposed three in-series reactions model predicts the process kinetics of the studied elements under different simulated environmental conditions (oxidation levels and acid sources). Differences between HNO₃ and CO₂ acidification are analysed through the influence of the CO₂ gas on the ionic competition of the medium. The acidification with CO₂ provokes higher released concentrations from the oxic sediment than from the anoxic sediment, except in the case of Zn, which influences the release of the other studied elements. Slight acidification can endanger the aquatic environment through an important mobilisation of contaminants. The obtained prediction of the contaminant release from sediment (kinetic parameters and maximum concentrations) can contribute to the exposure assessment stage for risk management and preincidental planning in accidental CO₂ leakages and chemical spills scenarios.

Bacterial community responses during a possible CO2 leaking from sub-seabed storage in marine polluted sediments

Carbon capture and storage (CCS) is a viable option to reduce high concentrations of CO₂ and mitigate their negative effects. This option has associated risks such as possible CO₂ leakage from the storage sites. So far, negative effects deriving from a CO₂ release have been reported for benthic macrofauna in both polluted and nonpolluted sediments. However, bacterial communities has no considered. In this work, risk assessment was carried out in order to evaluate the possible effects in a contaminated area considering bacterial responses (total number of cells, respiring activity, changes in the bacterial community composition and diversity). Four microcosms were placed into an integrated CO₂ injection system with a non-pressurized chamber to simulate four different pH treatments (pH control 7.8, 7, 6.5 and 6). Results showed an impact on bacterial communities because of the CO₂ treatment. Changes in respiring activity, community composition groups and diversity were found. This study highlights the use of respiring bacteria activity not only as bioindicator for environmental risk assessment and monitoring purposes but also as a bioindicador during a CO₂ leakage event or CO₂ enrichment process among all the responses studied.

A possible CO2 leakage event: Can the marine microbial community be recovered?

Bacterial communities have been studied to a much lesser degree than macrofauna in the case of a CO₂ release. The resistance capacity of marine bacteria is well known, but their possible responses and their ability to recover after a CO₂ release has not been investigated. Therefore, this work evaluated the responses of a marine bacterial community after 96h of CO₂ exposure under diverse pH treatments (7.8 as control without CO₂, 7.0, 6.5, and 6.0) and 24h after CO₂ exposure. Results showed that the respiration activity and the diversity of the community were affected in all pH treatments. However, after 24h without CO₂ enrichment, the respiration activity and diversity increased, showing a partial recovery. Consequently, bacterial responses have the potential to be used as a monitoring tool for risk assessment related to carbon capture and storage techniques or in any similar CO₂ enrichment situations.

Simulating CO2 leakage from sub-seabed storage to determine metal toxicity on marine bacteria

CO₂ storage in sub-seabed marine geological formations has been proposed as an adequate strategy to mitigate high CO₂ concentration from the atmosphere. The lack of knowledge about the potential risks of this technology on marine bacteria population in presence of metals has lead us to perform laboratory-scale experiments in order to evaluate its consequences. Thus, the effects of Zn and Cd were studied under acid conditions on Roseobacter sp. and Pseudomonas litoralis. Bacterial abundance (cellsmL^-1), growth rates (μ, h^-1), relative inhibitory effects of CO₂ (RI_CO2), and production of Extracellular Polysaccharides Substances (EPS) (μgGlucosecells^-1) were evaluated. A decreasing exopolysaccharides (EPS) production was found under low pH. Bacterial abundance as well as growth rates showed negative effects. Data obtained in this work are useful to determine the potential effects associated with enrichment of CO₂ and metals on the marine ecosystem.

CO2 leaking from sub-seabed storage: Responses of two marine bacteria strains

Carbon capture and storage (CCS) in stable geological locations is one of the options to mitigate the negative effects of global warming produced by the increase in CO2 concentrations in the atmosphere. A CO2 leak is one of the risks associated with this strategy. Marine bacteria attached to the sediment may be affected by an acidification event. Responses of two marine strains (Roseobacter sp. CECT 7117 and Pseudomonas litoralis CECT 7670) were assessed under different scenarios using a range of pH values (7.8, 7, 6.5, 6, and 5.5) to mimic a CO2 leak. A CO2 injection system was used to simulate an escape from a stable sub-seabed. Growth rate (μ), cell number, inhibition of Relative Inhibitory Effect (RI CO2) and inhibited population were analysed as endpoints. P. litoralis showed more sensitivity to high CO2 concentrations than Roseobacter sp. Our results highlight the diversity and resistance in marine bacteria and their capacity to adapt under a stressful CO2 leakage.

Carbon Capture and Storage (CCS): Risk assessment focused on marine bacteria

Carbon capture and storage (CCS) is one of the options to mitigate the negative effects of the climate change. However, this strategy may have associated some risks such as CO2 leakages due to an escape from the reservoir. In this context, marine bacteria have been underestimated. In order to figure out the gaps and the lack of knowledge, this work summarizes different studies related to the potential effects on the marine bacteria associated with an acidification caused by a CO2 leak from CSS. An improved integrated model for risk assessment is suggested as a tool based on the rapid responses of bacterial community. Moreover, this contribution proposes a strategy for laboratory protocols using Pseudomona stanieri (CECT7202) as a case of study and analyzes the response of the strain under different CO2 conditions. Results showed significant differences (p≤0.05) under six diluted enriched medium and differences about the days in the exponential growth phase. Dilution 1:10 (Marine Broth 2216 with seawater) was selected as an appropriate growth medium for CO2 toxicity test in batch cultures. This work provide an essential and a complete tool to understand and develop a management strategy to improve future works related to possible effects produced by potential CO2 leaks.