Climate change is causing an increase in the frequency and intensity of marine heatwaves (MHWs) and mass mortality events (MMEs) of marine organisms are one of their main ecological impacts. Here, we show that during the 2015–2019 period, the Mediterranean Sea has experienced exceptional thermal conditions resulting in the onset of five consecutive years of widespread MMEs across the basin. These MMEs affected thousands of kilometers of coastline from the surface to 45 m, across a range of marine habitats and taxa (50 taxa across 8 phyla). Significant relationships were found between the incidence of MMEs and the heat exposure associated with MHWs observed both at the surface and across depths. Our findings reveal that the Mediterranean Sea is experiencing an acceleration of the ecological impacts of MHWs which poses an unprecedented threat to its ecosystems' health and functioning. Overall, we show that increasing the resolution of empirical observation is critical to enhancing our ability to more effectively understand and manage the consequences of climate change.

Vegetated marine and freshwater habitats are being increasingly lost around the world. Habitat restoration is a critical step for conserving these valuable habitats, but new approaches are needed to increase restoration success and ensure their survival. We investigated interactions between plants and bivalves through a review and analysis of 491 studies, determined the effects, mechanisms and key environmental variables involved in and driving positive and negative interactions, and produced guidelines for integrating positive interactions into restoration efforts in different habitats. Fifty per cent of all interactions (both correlative and experimental studies) were positive. These were predominant between epifaunal bivalves and plants in all habitats, and between infaunal bivalves and plants in subtidal habitats. Plants primarily promoted bivalve survival and abundance by providing substrate and shelter, while bivalves promoted plant growth and survival by stabilizing and fertilizing the sediment, and reducing water turbidity. The prevalence of positive interactions increased with water temperature in subtidal habitats, but decreased with water temperature in intertidal habitats. The subset of studies conducted in a restoration context also showed mostly positive interactions. Twenty‐five per cent of all interactions were negative, and these were predominant between plants and infaunal bivalves in intertidal habitats, except sulphide‐metabolizing bivalves, which facilitated plant survival. Interactions involving non‐native species were also mostly negative. Synthesis and applications. Promoting facilitative interactions through plant–bivalve co‐restoration can increase restoration success. The prevalence of positive interactions depends on habitat and environmental conditions such as temperature, and was especially important in subtidal habitats (involving both infaunal and epifaunal bivalves) and in intertidal habitats (involving only epifaunal bivalves). Thus sites and species for co‐restoration must be carefully chosen to maximize the chances of success. If done properly, co‐restoration could increase initial survival, persistence and resilience of foundation species, and promote the recovery of associated biodiversity and ecosystem services.

We used seven biotic indices to determine the water quality of Karabal Stream (Gediz River) in West Anatolia, Turkey. The indices were based on benthic macroinvertebrate and physicochemical parameters: Saprobi Index (SI), Biological Monitoring Working Party (BMWP), Average Score per Taxon (ASPT), Family Biotic Index (FBI), Belgian Biotic Index (BBI), EPT-Taxa [%] were used as biotic indices and Shannon-Weaver index (SWDI), Simpsons index (SDI) and Margalef index (MDI) for diversity. Ten taxonomic groups were found in Karabal Stream consisting of Crustacea, Oligochaeta, Gastrapoda, Ephemeroptera, Plecoptera, Trichoptera, Odonata, Coleoptera, Diptera, and Hemiptera. The water quality along the stream varied from good class in the upstream stations, to moderate in downstream stations according to the most suitable indices. According to canonic correspondence analysis (CCA), the distributions of Diptera, Oligochaeta, and Hemiptera species are positively correlated to EC, Cl, Turbidity, Temperature, NH4-N, NO2-N, and NO3-N while they are negatively correlated to DO, DOS and pH. The distributions of EPT species are positively correlated to DO, DOS and pH. According to Pearson’s correlation, the BBI, BMWP (Original), BMWP (Spanish), and EPT-Taxa [%] metrics were sufficient in the estimation of water quality in the examined watercourse. Considering studies in surface waters of Turkey, the BMWP and EPT-Taxa [%] indices reflect the water quality as correctly in all studies we examined, however, BBI did not always show reliable results. Therefore there is a need for the establishment of a Turkish Biotic Index which takes into account country-specific macroinvertebrates, their abundance, biology, and ecology.

The members of the family Scenedesmaceae has the most widely used microalgae species in algal biotechnology studies because of their fast growth rate, quality of nutrition content and lipid accumulation under nutrient-limiting conditions. However, the biochemical responses of the species under phosphorus (P) limiting conditions are still unknown. The growth and biochemical composition of Desmodesmus communis in response to different phosphorus concentrations were investigated in this research. Five different phosphorus conditions were used: control (BG11); excess treatments (50% P+, 75% P+) and limited treatments (50% P−, 75% P-The highest cell concentration was observed in 75% P+ (725.6 × 104 cells/mL), whereas the highest dry weight concentration (1.81 mg/L) was found in 50% P- medium. The highest total lipid (4.94%) accumulation was found in the 50% P + medium and the maximum protein (49.5%) content was detected in 50% P- medium. Fatty acid and amino acid compositions change according to P concentration. PUFAs concentrations are higher than SFAs and MUFAs. Therefore the microalgae biomass obtained from this study cannot be used for biodiesel production although it is more suitable for nutritional supplement productions.

The effects of high nitrate concentrations on alterations in maximal photochemical efficiency of PSII ratio (Fv/Fm), chlorophyll content, chlorophyll degradation, growth rate and proline accumulation in Chlorella vulgaris Beyerinck [Beijerinck] were investigated in this study. The Fv/Fm ratio was observed in response to the increased nitrate concentration. The Fv/Fm ratio decreased in C. vulgaris following 44 h in 12.99 mM NaNO3-enriched media. Experimental results showed that, growth rates and chlorophyll content declined by increasing nitrate concentration. The decrease in the ratio of chlorophyll a/b with enrichment of high nitrate concentration (6.5 mM and 12.99 mM NaNO3) was also caused by a decrease in chlorophyll a and an increase in chlorophyll b concentration in C. vulgaris cultures. The results showed that 6.5 and 12.99 mM nitrate concentration increased proline content in treated cells, which suggests that nitrate stress lead to proline accumulation in C. vulgaris.