Desalination effects on macroalgae (part A): Laboratory-controlled experiments with Dictyota spp. from the Pacific Ocean and Mediterranean Sea

Abstract

Desalination brines from direct seawater intake that get discharged to coastal areas may produce stress responses on benthic marine communities, mostly due to its excess salinity, and especially on sessile organisms; in this context, macroalgae have been understudied in desalination ecotoxicological investigations. In this study, we assessed the short- and long-term cellular tolerance responses in two brown species of the macroalgae genus Dictyota through controlled laboratory conditions. Dictyota kunthii was collected from the eastern Pacific Ocean (average salinity, ~34 psu), whereas Dictyota dichotoma was from the Mediterranean Sea (average salinity, ~37 psu). Each macroalgae species was exposed for up to 7 days to two conditions with increased salinity values: +2 and +7 psu above their natural average salinity. Photosynthetic parameters and oxidative stress measurements were determined. The results showed that, in both Dictyota species, high salinity values induced reduced photoinhibition (Fv/Fm) but increased the primary productivity (ETRmax) and light requirement (EkETR) especially after 7 days. Conversely, the photosynthetic efficiency (αETR) decreased in hypersalinity treatments in D. dichotoma, while there were no changes in D. kunthii. The reactive oxygen species hydrogen peroxide (H2O2) was greater at high salinity values at 3 days for D. dichotoma and after 7 days in D. kunthii, while lipid peroxidation decreases under hypersalinity with time in both species. Despite the evident H2O2 accumulation in both species against hypersalinity, it did not produce oxidative damage and important impairment in the photosynthetic apparatus. These results contribute to understanding the tolerance strategies at the cellular level of Dictyota spp., which may be considered as potential candidates for biomonitoring of desalination impacts in the field.

Metabolic responses to desalination brine discharges in field-transplanted Posidonia oceanica: Advances for the development of specific early warning biomarkers

“…Overall, the data obtained in this study point to the presence of a battery of biochemical and molecular biomarkers that represent cellular stress, which can be extrapolated to higher levels of biological organization (e.g., physiology, population). The present study comprehensively described a set of reliable brine-monitoring biomarkers in P. oceanica, and this strategy can be also applied to other habitat-forming organisms in different temperate and tropical latitudes, such as corals (Marques et al, 2023), macroalgae (Muñoz et al, 2023;Rodríguez-Rojas et al, 2020), and other seagrasses (Blanco-Murillo et al, 2023a;Capó et al, 2020). Moreover, compared with previous mesocosmderived data, our results showed that using biomarkers related to osmotic and oxidative stress can provide information on brine-specific responses and also identify other potential combined effects when more stressors are present, respectively.…”

“…Moreover, the field studies have mainly focused on population metrics (e.g., percentage cover, shoot density), shoot morphometry (e.g., growth, foliar surface, necrosis marks), or physiology (e.g., nutrient concentration, carbohydrate content), while information is lacking about the effects of brine-associated hypersalinity at the sub-cellular and metabolic levels (biomarkers) (Roca et al, 2016;Sandoval-Gil et al, 2023;Tsioli et al, 2022). In this regard, the use of experimental transplants may allow the most reliable simulation of natural conditions while modifying the intensity of the studied stressor (Garrote-Moreno, Fernández-Torquemada, et al, 2014;Muñoz et al, 2023;Rodríguez-Rojas et al, 2020). Moreover, it has been demonstrated that the combination of a well-designed field transplantation with the analysis of sub-cellular and metabolic responses is the most effective strategy serving as an early warning tool.…”

“…Moreover, it has been demonstrated that the combination of a well-designed field transplantation with the analysis of sub-cellular and metabolic responses is the most effective strategy serving as an early warning tool. Specifically, these responses can be linked to physiological and ecological effects caused by adverse phenomena at the individual or population levels (Ankley et al, 2010) and can be also used to attribute the consequences of a response to specific stressors when several are present at the same time (Muñoz et al, 2023;Rodríguez-Rojas et al, 2020;Sáez et al, 2015). Most of these experiments have been conducted using macroalgae; therefore, it is necessary to address the potential usefulness of biomarkers in transplanted seagrasses as environmental biotechnology tools, especially in the context of desalination discharges.…”