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- Physiological and morphological effects of a marine heatwave on the seagrass Cymodocea nodosaPublication . Deguette, Alizé; Barrote, Isabel; Silva, JoãoMarine heatwaves (MHWs) are increasing in frequency and intensity as part of climate change, yet their impact on seagrass is poorly known. The present work evaluated the physiological and morphological responses of Cymodocea nodosa to a MHW. C. nodosa shoots were transplanted into a mesocosm facility. To simulate a MHW, water temperature was raised from 20 to 28 degrees C, kept 7 days at 28 degrees C, cooled down back to 20 degrees C and then maintained at 20 degrees C during an 8-day recovery period. The potentially stressful effects of the simulated heatwave on the photosynthetic performance, antioxidative-stress level and area vs dry weight ratio of leaves were investigated. The maximum quantum yield of photosystem II (phi PSII) increased during the heatwave, allowing the plants to maintain their photosynthetic activity at control level. Negative effects on the photosynthetic performance and leaf biomass of C. nodosa were observed during the recovery period. No significant oxidative stress was observed throughout the experiment. Overall, although C. nodosa showed a relative tolerance to MHWs compared to other species, its population in Ria Formosa is likely to be negatively affected by the forecasted climate change scenarios.
- Glyphosate: a terrestrial threat to marine plants? a study on the seagrass zostera marinaPublication . Deguette, Alizé; Pes, Katia; Vasconcellos, Bernard; Costa, Monya; Silva, João; Barrote, IsabelGlyphosate-based herbicides (GBHs) are extensively used worldwide, raising concerns about their potential effect on non-target aquatic ecosystems. This study investigated the short-term physiological effects of a commercially available GBH on the seagrass Zostera marina under controlled mesocosm conditions. Z. marina individuals were exposed to three concentrations of glyphosate (0.165, 51, and 5100 mg L−1 ) for 4 days, and the impacts on photosynthetic performance, growth rate, photosynthetic pigments content and energy metabolism were assessed. Exposure to 5100 mg L−1 of glyphosate caused rapid water acidification and complete plant mortality within 24 h. Exposure to 51 mg L−1 of glyphosate significantly impaired photosynthetic efficiency and foliar growth rate. Energy availability, photosynthesis and photosynthetic pigments content were highly disrupted at both higher concentrations. Exposure to 0.165 mg L−1 of glyphosate decreased the foliar chlorophyll a/b ratio. These findings show that Z. marina can potentially be threatened by the presence of GBHs even at lower concentrations and underscore the necessity for monitoring herbicide pollution in coastal waters to protect seagrass habitats and associated ecosystems. Further research is needed to assess long-term effects and the role of herbicide formulations in mediating toxicity.
- White is a new shade of blue carbon: a case study of a traditional salt production pond that is a net carbon sinkPublication . Alexandre, Ana; Barrena de los Santos, Carmen; Jiménez Herrero, Javier; Deguette, Alizé; Silva, João; Martins, Márcio; Parreira, Filipe; Schubert, Nadine; Rosa, Saray P. de la; Santos, RuiTo address for the first time the carbon budget of traditional salterns, we measured the diel, seasonal, and spatial variability of water‐air CO2‐eq fluxes (CH4 and CO2) and the Organic Carbon (OC) stock and burial rate in the sediment. Temperature, salinity, dissolved oxygen, pH and wind were assessed as potential environmental drivers of the fluxes. The saltern emitted CH4 to the atmosphere throughout the year, with no significant differences among sites or seasons. On the contrary, the saltern were a sink of CO2 in summer, autumn and winter, and a source of CO2 in spring. Water temperature was the main positively related predictor variable of CH4 fluxes, explaining 29% of their variance, whereas CO2 fluxes were significantly negatively related to the concentration of O2 and pH in the seawater and positively related to wind, which explained 66% of fluxes variance. The sedimentary and OC stocks and burial rates were not significantly different among the sampled ponds and averaged 11.9 ± 2.2 Mg OC ha− 1 and 0.011 ± 0.004 Mg OC ha− 1 yr− 1 , respectively. The carbon budget of the saltern was − 35.0 g CO2‐eq m− 2 yr− 1 , corresponding to − 1.49 Mg CO2‐eq yr− 1 for the total saltern area. This suggests that the‐salt industry may function as a carbon sink as opposed to other coastal industries such as fish and shrimp aquaculture. Future studies with additional measurements across a wider range of salterns are needed to evaluate the relevance of “white carbon.”