Due to the poor solubility of iron (III) and strong regional differences in terrestrial, riverine or airborne input, iron is a limiting micronutrient in much of the world ocean. Because of increasing living standards and climate change, rainfall is becoming more intermittent, which exacerbates drought conditions. As a result, seawater desalination has a vital and growing role in providing drinking water in many hot and arid regions of the world. Most seawater desalination plants use ferric or ferrate salts as flocculants for removing phyto- and bacterioplankton and suspended organic matter prior to the actual desalination process. Consequently, such seawater desalination plants release large amounts of suspended iron in conjunction with organic matter into coastal waters, with potentially significant consequences for the availability of this micronutrient in coastal marine ecosystems. This review paper provides important background information about the role of iron as a micronutrient in marine ecosystems, its role in the inorganic biochemistry of marine life, as well as key features of its use in seawater desalination, before providing a perspective by exploring potential implications for the physiology and biochemistry of marine life and marine ecosystem functioning.

Benthic diatoms are sensitive indicators of environmental conditions at the seabed. In this study, benthic diatom communities at two brine outfall sites of reverse osmosis (RO) seawater desalination plants in Larnaca and Dhekelia, Cyprus, were investigated using a classical, microscopy-based approach and environmental DNA metabarcoding. In general, the diversity of diatoms measured by both methods (microscopy and eDNA metabarcoding), increased by distance from the brine discharge. Increased TOC and nutrient enrichment at brine outfalls contributed to decreased diatom diversity at the Larnaca outfalls, but the diatom diversity at Dhekelia was not driven by abiotic factors. The diatom communities at the outfalls were shown to be distinct and showed temporal variation across the sampling seasons with eDNA metabarcoding, but this was the case only for Dhekelia with microscopy. The results highlight the effect of local biogeography and different brine mixing methods on diatom diversity. The results revealed that conventional morphological methods and eDNA metabarcoding rarely leads to similar conclusions. However, the complementary results emphasise that more information can be derived when combining the methods for biodiversity impact assessments.

A new species of the amphipod genus Pontocrates (Boeck 1871), family Oedicerotidae, is described from Cyprus in the south-eastern Mediterranean Sea. It is a sister taxon to Pontocrates moorei (Myers & Ashelby 2022), currently recorded solely from the British Isles. It is the third species of Pontocrates now known to occur in the Mediterranean Sea.

The Port of Rotterdam is a heavily man-modified estuarine system, Europe's major seaport and home to a large number of chemical and petrochemical plants, many of which are supplied with distilled water from two demineralized water plants in Botlek and Maasvlakte. In this study, we assessed the ecological conditions near the brine outfalls and at a reference site unimpacted by brine, focusing on the benthic macrofaunal composition. Overall, the analysis of the communities and species revealed a similar macrobenthic composition, although with lower abundance and diversity compared to the nearby North Sea environment. The outfall area of the Botlek demineralized water plant, which is a dead-end entirely marine waterway with no to little currents in contrast to the well flushed brackish environment of the outfall of the Maasvlakte demineralized water plant, was characterized by the lowest abundance of benthic macroinvertebrates, species richness and Shannon diversity index. Higher biodiversity values at the Maasvlakte demineralized water plant compared to the reference site were also associated with the presence of a large biogenic reef of the Pacific oyster Crassostrea gigas with specimens of over 8 years estimated age being observed, however with many dead individuals recorded at the time of surveys. The outfall area of the Botlek demineralized water plant also had the highest disturbance levels according to the results of AZTI's Marine Biotic Index (AMBI) in conjunction with Benthos Ecosystem Quality Index (BEQI). Its community was dominated by the opportunistic native species Capitella capitata and Varicorbula gibba, and species typical for organic matter enrichment such as Alitta succinea (native), Streblospio cf shrubsolii (native) and Theora lubrica (invasive), which correlates well with higher levels of anthropogenic pollution in this area. Generalized linear model (GLM) and distance-based multivariate linear model (DistLM) showed that the distance from the outfalls was an important factor in terms of brine impacts however explaining a small part of the variation observed. Similarity percentage analysis (SIMPER), multivariate analysis, and permutational multivariate analysis (PERMANOVA) showed low similarity between and within study sites, confirming that high levels of heterogeneity exist within the estuarine system in terms of natural conditions and anthropogenic stress.

Cyprus relies on seawater desalination for a large part of its drinking water supply, with reverse osmosis providing more than 95% of the total desalination capacity in the country. Nevertheless, the environmental impacts of desalination for the Cypriot environment remain poorly understood. Using a combination of mining existing governmental and corporate survey data and reports, this study explores the scale of desalination in Cyprus, the impacts on the coastal marine environment and its overall carbon footprint. Surveys of Posidonia oceanica seagrass meadows show strongly reduced density of shoots and leaf surface area, respectively. Analysis of the available data relating to the overall production of desalinated water and energy consumption reveals that 68.7 million m3 of desalinated water were produced in Cyprus in 2017, resulting in the release of 160 ktons of CO₂ equivalent, representing around 2% of the total carbon emissions in Cyprus. The results are directly applicable for understanding the impacts of brine discharge on seagrass meadows, one of the most common types of Mediterranean seabed ecosystems and useful for providing guidance to decision makers as they are striving to achieve a zero-carbon economy. strategies for achieving greater sustainability in terms of reduced CO₂ emissions and less brine discharge are discussed.