Immunomodulatory response of Asian seabass Lates calcarifer in an ex situ environment: implications for future ocean acidification scenario

Global warming and ocean acidification (OA) are being brought on by an increase in atmospheric carbon dioxide (CO2) concentration (Feely et al., 2004Orr et al., 2005), and both are now widely acknowledged as significant factors in modulating physiological systems in the marine organism (Srinivasan et al., 2022). Increased CO2 levels in the surface waters result in a drop in seawater pH, and changes in the chemistry of carbonates, and can have an impact on the bioavailability of contaminants (Bijma et al., 2013). Although OA has a significant impact on the acid-base balance, energy metabolism, and biomineralization of marine organisms (Kroeker et al., 2010), its effects on immune functions are still poorly understood (Calder-Potts et al., 2008), which makes it difficult to predict how susceptible marine fish to overcome the parasites and diseases attack as the ocean physicochemical concentration changes.

The survival of marine organisms are significantly influenced by good seawater quality (Jha et al., 2013), diseases and parasites free suitable locations, which are regarded as the main risk factor in both fish farms and the open ocean (Kumar et al., 2009Jha et al., 2017). The resistance of aquatic organisms to parasites and diseases can be modulated by environmental stresses, such as fluctuations in temperature, salinity, and pollution (Galloway and Depledge, 2001Marcogliese, 2008). Fish that live in water are constantly exposed to a variety of pathogenic and non-pathogenic microorganisms; as a result, they may evolve powerful defence systems that aid in their survival. Aquatic organism immune systems, like that of fish, are constantly impacted by periodic or unanticipated changes in their surroundings. Fish health status may be negatively impacted by adverse environmental circumstances either acutely or chronically, either by changing certain biochemical parameters or by regulating innate and adaptive immune responses (Domingueza et al., 2004). Fish may therefore serve as significant indicator in the biomonitoring of water quality, particularly immunotoxic environmental contaminants, depending on their biological factors related to immunity.

The available literature regarding the alteration of immunity in shellfish because of ocean acidification shows that earlier studies were focused on marine invertebrates since the shellfish are more vulnerable to acidified environment since most of the higher invertebrates rely more on these environment for calcification (Ivanina et al., 2014). Our previous study documented that acidified environment impairs haematological and serum biochemical parameters in Lates calcarifer (Srinivasan et al., 2022). In the present study, it was further observed that long-term chronic exposure to acidified medium modulated the immunocompetence of fish in terms of the change in immune-associated parameters tested. To our knowledge, negligible work has been carried out to observe the impact of seawater acidification on immunomodulation in fish with different size groups. Therefore the present study investigated the effect of acidification on the nonspecific immune-associated parameters, including respiratory burst, myeloperoxidase (MPO) activity, bactericidal activity, circulating total immunoglobulin, and on cellular components (leukocytes) in two different size groups (fish fry and fingerlings) of Lates calcarifer.

Marcus P. N., Sivakumar P., Srinivasan G., Sivakumar R., Harikrishnan T., Balasubramaniam S. & Singaram G., 2022. Immunomodulatory response of Asian seabass Lates calcarifer in an ex situ environment: implications for future ocean acidification scenario. Frontiers in Marine Science 9: 1011149. doi: 10.3389/fmars.2022.1011149. Article.

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