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

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 2 -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 2 (1080 μatm atmospheric CO 2 ), the water-soluble fraction (WSF) of crude oil (500 μg/L) and a CO 2 (1080 μatm atmospheric CO 2 )/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 2 or WSF was given alone at 30 days of age. Combination of CO 2 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 2 partial pressure ( p CO 2 ) levels and crude oil pollution, OA and crude oil pollution have the potential to act as an additional source of natural mortality.