Desalination brine effects beyond excess salinity: Unravelling specific stress signaling and tolerance responses in the seagrass Posidonia oceanica

Evaluating physico-chemical and biological impacts of brine discharges for a sustainable desalination development on South America's Pacific coast

The expansion of seawater desalination is presented as a new way to supply fresh water for many coastal regions as an effort to counteract the increasing water scarcity. However, brine discharges also pose significant environmental challenges regarding their potential environmental impacts of marine ecosystems. The main objective of this study was to assess the physico-chemical impact of the brine discharges from Seawater Reverse Osmosis (SWRO) desalination plants on South America pacific coastal ecosystems, assessing its potential physical-chemical impact (temperature, salinity, density and dissolved oxygen) on the receiving marine environment, and evaluating the oxidative and osmotic stress responses of the red macroalgae Rhodymenia corallina through diagnostic biomarkers in field-transplantation experiments. Our results showed that the increase over natural salinity in the affected area was less than 3.5 % in a radius of 50 m from the discharge point. Also, we demonstrated that the brine discharges increase the density but not significant affect the temperature and dissolved oxygen of the marine environment. In addition, diagnostic biomarkers showed a negative effect on oxidative, osmotic and antioxidant stress responses in R. corallina after two days of brine exposure, particularly at the nearest brine diffuser transplantation site. However, after five days, antioxidant and osmotic parameters exhibited full recovery, indicating the cessation of the redox imbalance. Based on the results obtained, we demonstrated that the use of appropriate mitigation measures combined with an appropriate oceanographic location of the submarine outfall, would ensure a sustainable desalination operation without generating significant environmental impacts on the coastal ecosystems.

BVOC emissions from Posidonia oceanica, the most abundant Mediterranean seagrass species

Biogenic Volatile Organic Compounds (BVOCs) are important precursors of tropospheric atmospheric pollutants such as ozone and secondary organic aerosols. Thus, it is crucial to characterize BVOCs sources at regional and global scales. Marine environments, especially benthic ecosystems, are still overlooked although they can produce a wide range of BVOCs. In this study, BVOCs emissions from Posidonia oceanica, the main seagrass species in the Mediterranean Sea, were characterised over several days using dynamic enclosure systems. A total of 105 different compounds were detected through PTR-ToF-MS and GC-MS analyses (after checking compounds correspondence between both analyses) and included terpenoids (isoprene), sulfur- (dimethyl sulfide (DMS)), halogenenated- (chloromethane), and oxygenated compounds (methanol, acetone). High BVOCs emissions were measured (up to 10 and 4 μg.gDW-1.h-1 for DMS and acetone, respectively), in the same ranges reported for terrestrial plant species. Most BVOCs followed diurnal cycles with higher emissions during the day compared to night, although nocturnal emissions were also detected. Surprisingly, DMS emissions showed an opposite pattern with higher emissions at night. Uptakes were recorded for formic acid all through the day, at night for acetonitrile and only punctually for most other BVOCs. Our results strongly suggest that P. oceanica meadows are important contributors to the regional BVOCs budget in the Mediterranean basin.

A review of the potential of seawater brine for enhancing food security in hot arid climates: A case study of Qatar

This study explores Qatar's utilisation of seawater to support food security, emphasising the innovative strategies and technological advancements to address the environmental and agricultural challenges posed by rejected brine from desalination processes. It examines various brine treatment and disposal methodologies, highlighting the environmental impacts and proposing sustainable solutions to mitigate these effects. The discussion further explores the potential of electrodialysis and other emerging technologies for converting rejected brine into valuable agricultural resources, thereby contributing to food security in arid regions. Through a comprehensive review of current research and potential innovations, this study highlights the critical intersection of water resource management, environmental sustainability, and food production, particularly in Qatar's unique geographical and climatic conditions.

Early signals of Posidonia oceanica meadows recovery in a context of wastewater treatment improvements

Natural ecological restoration is a cornerstone of modern conservation science and managers need more documented "success stories" to lead the way. In French mediterranean sea, we monitored Posidonia oceanica lower limit using acoustic telemetry and photogrammetry and investigated the descriptors driving its variations, at a national scale and over more than a decade. We showed significant effects of environmental descriptors (region, sea surface temperature and bottom temperature) but also of wastewater treatment plant (WWTP) effluents proxies (size of WWTP, time since conformity, and distance to the closest effluent) on the meadows lower limit progression. This work indicates a possible positive response of P. oceanica meadows to improvements in wastewater treatment and a negative effect of high temperatures. While more data is needed, the example of French wastewater policy should inspire stakeholders and coastal managers in their efforts to limit anthropogenic pressures on vulnerable ecosystems.

Exploring priming strategies to improve stress resilience of Posidonia oceanica seedlings

Seagrasses' ability to store information after exposure to stress (i.e. stress memory) and to better respond to further stress (i.e. priming) have recently been observed, although the temporal persistence of the memory and the mechanisms for priming induction remain to be defined. Here, we explored three priming strategies in Posidonia oceanica seedlings, each inducing a different level of stress, for temperature and salinity. We investigated changes in morphometry, growth rate and biomass between primed and non-primed seedlings. The results showed similar behaviour of seedlings when exposed to an acute stress event, regardless of whether they had been primed or not and of the priming strategy received. This opens the debate on the level of stress necessary for inducing a priming status and the persistence of the stress memory in P. oceanica seedlings. Although no priming-induced stress resistance was observed, seedlings showed unexpectedly high resilience to extreme levels of both abiotic stressors.

Ecocriminological analysis of brine in aquatic ecosystems: impacts on Posidonia oceanica and the search for restorative justice solutions

The consumption of fresh water has generated additional problems in certain territories, along with the consequences of global warming. This has meant that in the most vulnerable areas, such as the Balearic archipelago in the Mediterranean, alternative water supply systems have been established: desalination plants. However, the ecological impact of these infrastructures is great, mainly affecting aquatic ecosystems. In light of the above, this paper addresses the ecological harm caused by desalination and brine discharges on a protected and priority species, P. Oceanica. Taking as ethico-legal foundation the theory of ecological justice, a multilevel analysis was carried out from an ecocriminology perspective on the impacts of this authorized practice on P. Oceanica and other species. Finally, a restorative justice view will allow us to understand and envision possible solutions to this ecological harm.