Abstract
The early stages of intertidal mussels, including the green-lipped mussel, Perna canaliculus, face both direct and indirect environmental threats. Stressors may influence physiological status and, ultimately, survival. An understanding of the nature of stress experienced is critical to inform conservation and aquaculture efforts. Here, we investigated oxidative stress dynamics in juvenile P. canaliculus in relation to emersion duration (1–20 h) and relative humidity (RH, 29–98%) by quantifying oxidative damage (protein carbonyls, lipid hydroperoxides, 8-hydroxydeoxyguanosine) and enzymatic antioxidants (superoxide dismutase, catalase, glutathione peroxidase and reductase). Mussels held in low RH during emersion experienced severe water loss (>70%), high mortality (>80%) and increased oxidative damage (35–45% increase compared to control conditions), while mussels held at high RH were not impacted, even after 20 h of air exposure. Following re-immersion, reoxygenation stress resulted in further increases in damage markers in mussels that had experienced dryer emersion conditions; protective action of antioxidants increased steadily during the 10 h re-immersion period, apparently supporting a reduction in damage markers after 1–5 h of immersion. Clearly, conditions during emersion, as well as duration, substantially influence physiological performance and recovery of juvenile mussels. Successful recruitment to intertidal beds or survival in commercial aquaculture operations may be mediated by the nature of emersion stress experienced by these vulnerable juveniles.
Highlights
Emersion is a significant source of stress for marine organisms
This study showed that the effects of emersion and the re-immersion dynamics of juvenile Perna canaliculus are complex and mainly depend on the conditions that the mussels experience during emersion
The strongest correlation was observed for oxidative damage in the form of protein carbonyls (PCs) at low and mid relative humidity (RH), where mortality increased steadily with PC levels, as time of emersion increased (r2 = 0.9991 at low RH and r2 = 0.7273 at mid RH)
Summary
Emersion is a significant source of stress for marine organisms. During emersion, organisms can be exposed to fluctuations in temperature, irradiance, and relative humidity (RH), with many intertidal organisms having physiological and behavioural adaptions that allow them to cope with such stressors [1,2]. The capacity to tolerate emersion in marine invertebrates closely relates to their bathymetric distribution [8,9]. Some bivalve molluscs depress their metabolism during emersion [10] or rely on anaerobic pathways to maintain ATP production for short emersion periods [11,12]; air-gaping during long-term emersion exposure may subsequently assist in acid-base regulation [13]. These different strategies to deal with emersion-related hypoxia are likely to affect the organism’s responses following re-immersion in seawater
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