Osmoregulation, bioenergetics and oxidative stress in coastal marine invertebrates: raising the questions for future research

Abstract

Osmoregulation is by no means an energetically cheap process, and its costs have been extensively quantified in terms of respiration and aerobic metabolism. Common products of mitochondrial activity are reactive oxygen and nitrogen species, which may cause oxidative stress by degrading key cell components, while playing essential roles in cell homeostasis. Given the delicate equilibrium between pro-and antioxidants in fueling acclimation responses, the need for a thorough understanding of the relationship between salinity-induced oxidative stress and osmoregulation arises as an important issue, especially in the context of global changes and anthropogenic impacts on coastal habitats. This is especially urgent for intertidal/ estuarine organisms, which may be subject to drastic salinity and habitat changes, leading to redox imbalance. How do osmoregulation strategies determine energy expenditure, and how do these processes affect organisms in terms of oxidative stress? What mechanisms are used to cope with salinity-induced oxidative stress? This Commentary aims to highlight the main gaps in our knowledge, covering all levels of organization. From an energy-redox perspective, we discuss the link between environmental salinity changes and physiological responses at different levels of biological organization. Future studies should seek to provide a detailed understanding of the relationship between osmoregulatory strategies and redox metabolism, thereby informing conservation physiologists and allowing them to tackle the new challenges imposed by global climate change.

The scale‐dependent effect of environmental filters on species turnover and nestedness in an estuarine benthic community

“…These species are adapted to particular levels of salinity on which they can control osmotic pressure and ionic concentration with low energy cost (Medeiros et al. , Rivera‐Ingraham and Lignot ). Therefore, considering that each species has physiological adaptations to different levels of salinity and they are allowed to freely track those conditions (Josefson , Medeiros et al.…”

“…In accordance with this theoretical expectation, our study shows that benthic b-diversity across the whole estuarine system reflects mainly the replacement of oligohaline species in the inner by polyhaline species in the outer sector. These species are adapted to particular levels of salinity on which they can control osmotic pressure and ionic concentration with low energy cost (Medeiros et al 2016, Rivera-Ingraham andLignot 2017). Therefore, considering that each species has physiological adaptations to different levels of salinity and they are allowed to freely track those conditions (Josefson 2016, Medeiros et al 2016, the result must be a spatial change in species composition along the estuary.…”

Tolerance of disease‐vector mosquitoes to brackish water and their osmoregulatory ability

“…vs. diluted SW in our study) or from differences between strains of the same species. However, tolerance to salinity may vary in time due to the cost of osmoregulation mechanisms and salinity‐induced oxidative stress (Rivera‐Ingraham and Lignot ). Indeed, slight differences between studies might be expected due to the strain origins.…”

Combined salinity and acidity stressors alterDaphnia magnapopulation growth and structure under severe absence of photoperiod

“…Daphnids, therefore, may survive the acidity stress dependent on their acidity sensitivity/tolerance [2,74,75]. In sum, daphnid acid-sensitivity and shortage of ambient calcium in acidified water [76] with subsequent sodium deficit [2], oxidative stress, increased maintenance under stress [8], and the resulting costly bioenergetics [2,11] were the likely reasons behind the poor daphnid performance under the acidity levels of the current work. These findings contribute to our understanding of the damaging effects of low pH levels on aquatic systems that are presently vulnerable to constant change worldwide [5,45].…”

“…The genome of Daphnia may express different phenotypes in reaction to different environmental conditions; a phenomenon referred to as phenotypic plasticity [7]. Rapid responses to environmental stressors, such as ionic and osmotic regulation [8], which may be due to transgenerational epigenetic effects [9–10], are associated with high energetic costs [2,11], and may enable Daphnia to occupy a wider niche range compared to other fresh water inhabitants [12]. However, low pH levels have been shown to reduce zooplankton species richness and alter the structure of cladoceran populations [13–14], leading to diminished survival and growth of D. magna below pH 5 [15].…”