Combined effects of ocean acidification and crude oil pollution on tissue damage and lipid metabolism in embryo–larval development of marine medaka (Oryzias melastigma)

Abstract

Ocean acidification (OA) and crude oil pollution have been highlighted as some of the most pervasive anthropogenic influences on the ocean.In marine teleosts, early life-history stages are particularly vulnerable to disturbance by CO-driven acidification as they lack pH-mediated intracellular regulation. Embryos exposed to trace levels of crude oil constituents dissolved in water exhibit a common syndrome of developmental abnormalities. So far, little is known about the combined effects of OA and crude oil on the early life history of marine fish. Eggs and larvae of the marine medaka (Oryzias melastigma) were treated with CO (1080 μatm atmospheric CO), the water-soluble fraction (WSF) of crude oil (500 μg/L) and a CO (1080 μatm atmospheric CO)/WSF (500 μg/L) mixture within 4 h after oviposition. Isolated and combined OA/WSF had no detectable effect on embryonic duration, egg survival rate and size at hatching. Histopathological anomalies of tissue and lipid metabolic disorder were significant when CO or WSF was given alone at 30 days of age. Combination of CO and WSF enhanced their toxicity compared to their separate administration. Since the early life-history stage of marine fish is thought to be impacted more heavily by increasing CO partial pressure (pCO) levels and crude oil pollution, OA and crude oil pollution have the potential to act as an additional source of natural mortality.

Welfare of scaleless fish, Sagor catfish ( Hexanematichthys sagor ) juveniles under different carbon dioxide concentrations

“…Elevated pCO 2 (>1000 µatm) was shown to lower the serum total triglycerides in Amazonian fish tambaqui ( Colossoma macropomum ) (de Oliveira & Val, 2017). Triglycerides make up the lipid in fish and can be used as an indicator of nutritional condition, as well serum total protein and cholesterol (Sun et al, 2019). Based on the present results, lower pCO 2 in control group may inhibit the fat accumulation in the fish's tissues therefore enhancing the quality of meat.…”

Global variation in freshwater physico‐chemistry and its influence on chemical toxicity in aquatic wildlife

“…For example, elevated environmental CO 2 provided some protection against the physiological impacts of waterborne copper in fish, both in fresh water (rainbow trout; Wang et al ., 1998) and in sea water (cod Gadus morhua ; Larsen, Portner & Jensen, 1997). Exposure of saltwater medaka ( Oryzias melastigma ) embryos to ~1000 μatm CO 2 combined with the water‐soluble fraction of crude oil resulted in greater histological damage to eyes, kidney, pancreas and liver compared to larvae from embyros treated with each stressor separately (Sun et al ., 2019).…”

CO2 induced seawater acidification impacts survival and development of European eel embryos

“…For example, in the two-spotted goby, Gobiusculus flavescens , exposure to pH 7.6 and 1400 μatm resulted in a two-fold increase in embryonic mortality compared to current day values [ 65 ]. However, many species, such as the marine medaka, Oryzias melastigma [ 66 , 67 ] and the Atlantic herring, Clupea harengus [ 68 ], are able to tolerate pCO 2 levels ranging from 1000 to 4000 μatm (~pH 7.7–7.0) in terms of embryonic survival. Differences in life-history traits may contribute to the observed differential tolerance to acidification across fish species, as inter alia , the duration of the incubation period defines the time of exposure to low pH during these early vulnerable stages [ 69 ].…”