Ocean acidification impact on haematological and serum biochemical parameters in Lates calcarifer

Introduction

Ocean acidification (OA) is a long-term drop in the pH of the ocean caused mostly by atmospheric carbon dioxide (CO2). It is a consequence of climate change that poses a direct threat to life on earth by affecting the marine ecosystem (Panchang and Ambokar, 2021). The ocean has absorbed around 30% of the carbon dioxide emitted by human activities since the beginning of the industrial revolution (Sabine et al., 2004). The elevated partial pressure of carbondioxide (pCO2) causes seawater pH and CaCO3 staturation to decrease (Feely et al, 2004). The pCO2 value is now at 375 atm (Rhein et al., 2013) which is expected to reach 420 to 940 atm by 2100, and pH may decline by 0.13 to 0.42 units scenario (Rhein et al., 2013). The pH of sea water has declined from 8.17 units in pre-industrial periods (Key et al., 2004) to 8.06 units now (Rhein et al., 2013), indicating a decrease of 34.91%. Due to eutrophication and amplification of natural CO2 some coastal locations may see shifts H+ that are at least 2–3 times the world average (Melzner et al., 2012). Many marine organisms’ physiological activities are predicted to be influenced by such changes in ocean chemistry, potentially having far-reaching effects on marine biodiversity and ecological processes (Murugan et al., 2005Vijayakumaran et al., 2005Fabry et al., 2008Pörtner, 2008Kumar et al., 2009Gattuso et al., 2011).

Ocean acidification thought to harm marine fish performance, owing to changes in oxygen availability and delivery capabilities (Pörtner, 2008). Individual survival may be harmed by acidic pH because less energy is allocated to digestion, growth, and reproduction (Munday et al., 2009Munday et al., 2014). The OA has the ability to change the outcomes of ecologically important processes and the structure of ecological communities (Pörtner, 2008). Given that abiotic variables such as oxygen availability, temperature, and salinity are known to have the greatest influence on aquatic species’ early life stages (Bonk, 2005), the possible impact of acidified seawater on their development should be taken into account. Only a few studies on the impact of OA on early life stages of aquatic animals have been conducted, with the majority focusing on invertebrates (Kurihara et al., 2004Havenhand et al., 2008Dupont and Thorndyke, 2009Ellis et al., 2009 Dupont et al., 2010) indicating that the impact of OA on the early life history of vertebrates is scanty.

Because blood is the channel of intercellular transfer and comes into direct contact with multiple organs and tissues of the body, it plays an important part in all physiological systems and hence, an animal’s physiological status at any given time is reflected in its blood. Any type of environmental stress induces oxidative stress in a normal organism, which is reflected in blood proteins and causes haematological changes, and may be used as a method for biological monitoring (Martinez and Souza, 2002). Although organisms are resistant to the harmful effects of oxidative stress caused due to reactive oxygen species, prolonged exposure can cause oxidative damage, including the loss of compensatory mechanisms due to changes in enzyme function (Galloway and Handy, 2003Dogan and Can, 2011Narra, 2017). Adverse changes in the haematological and biochemical markers indicate toxicity, and their use in environmental monitoring and aquatic biota health has a wide variety of applications (Thilagam et al., 2009Narra, 2017).

A few research on the consequences of hypercapnia on various life stages of marine teleosts have been published in recent years (Checkley et al., 2009Munday et al., 2009Munday et al., 2014). Increased pCO2 levels were employed by Kikkawa et al. (2003) to explore the acute lethal effect of pCO2 on the early life stages of marine fishes. The whole world’s seas, especially coastal estuaries and streams, are being affected by OA. Many economies rely on fish and shellfish, and people all over the world use seafood as their major source of protein. Considering the need of the hour and importance of fisheries sector, an experiment was designed to study seawater acidification impacts on the growth rate of Indian seabass at various stages of their lives (Fry and Fingerlings). In both fry and fingerlings, we investigated how acidified medium alter haematological, biochemical markers in blood and consequently affect the growth. Thus, this study will help in designing the long-term effects of ocean acidification on the growth of Indian seabass, which might have implications on coastal and marine ecosystem organisms.

Gomathi S., Niranjani M. P., Priya S., Pandi P., Rekha S., Thilagam H. & Sujatha B., 2022. Ocean acidification impact on haematological and serum biochemical parameters in Lates calcarifer. Frontiers in Marine Science 9: 940573. doi: 10.3389/fmars.2022.940573. Article.


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