Effects of elevated CO2 in the early life stages of summer flounder, Paralichthys dentatus, and potential consequences of ocean acidification

[摘要] The limited available evidence about effects on marine fishes of highCO₂ and associated acidification of oceans suggests that effects willdiffer across species, be subtle, and may interact with other stressors. Thisreport is on the responses of an array of early life history features ofsummer flounder (Paralichthys dentatus), an ecologically andeconomically important flatfish of the inshore and nearshore waters of theMid-Atlantic Bight (USA), to experimental manipulation of CO₂ levels.Relative survival of summer flounder embryos in local ambient conditions(775 μatm pCO₂, 7.8 pH) was reduced to 48% whenmaintained at intermediate experimental conditions(1808 μatm pCO₂, 7.5 pH), and to 16% when maintainedat the most elevated CO₂ treatment (4714 ppm pCO₂, 7.1 pH).This pattern of reduced survival of embryos at high-CO₂ levels atconstant temperature was consistent among offspring of three females used asexperimental subjects. No reduction in survival with CO₂ was observedfor larvae during the first four weeks of larval life (experiment ended at28 d post-hatching (dph) when larvae were initiating metamorphosis).Estimates of sizes, shapes, and developmental status of larvae based onimages of live larvae showed larvae were initially longer and faster growingwhen reared at intermediate- and high-CO₂ levels. This pattern of longerlarvae – but with less energy reserves at hatching – was expressed throughthe first half of the larval period (14 dph). Larvae from thehighest-CO₂ conditions initiated metamorphosis at earlier ages andsmaller sizes than those from intermediate- and ambient-CO₂ conditions.Tissue damage was evident in larvae as early as 7 dph from bothelevated-CO₂ levels. Damage included dilation of liver sinusoids andveins, focal hyperplasia on the epithelium, and separation of the trunkmuscle bundles. Cranio-facial features changed with CO₂ levels in anage-dependent manner. Skeletal elements of larvae from ambient-CO₂environments were comparable or smaller than those from elevated-CO₂environments when younger (7 and 14 dph) but were larger at developmentalstage at older ages (21 to 28 dph), a result consistent with the acceleratedsize-development trajectory of larvae at higher-CO₂ environments basedon analysis of external features. The degree of alterations in the survival,growth, and development of early life stages of summer flounder due toelevated-CO₂ levels suggests that this species will be increasinglychallenged by future ocean acidification. Further experimental studies onmarine fishes and comparative analyses among those studies are warranted inorder to identify the species, life stages, ecologies, and responses likelyto be most sensitive to increased levels of CO₂ and acidity in futureocean waters. A strategy is proposed for achieving these goals.

[学科分类] 地球化学与岩石