Response of ocean acidification to atmospheric carbon dioxide removal

Artificial CO_(2)removal from the atmosphere(also referred to as negative CO_(2)emissions)has been proposed as a potential means to counteract anthropogenic climate change.Here we use an Earth system model to examine the response of ocean acidification to idealized atmospheric CO_(2)removal scenarios.In our simulations,atmospheric CO_(2)is assumed to increase at a rate of 1%per year to four times its pre-industrial value and then decreases to the pre-industrial level at a rate of 0.5%,1%,2%per year,respectively.Our results show that the annual mean state of surface ocean carbonate chemistry fields including hydrogen ion concentration([H^(+)]),pH and aragonite saturation state respond quickly to removal of atmospheric CO_(2).However,the change of seasonal cycle in carbonate chemistry lags behind the decline in atmospheric CO_(2).When CO_(2)returns to the pre-industrial level,over some parts of the ocean,relative to the pre-industrial state,the seasonal amplitude of carbonate chemistry fields is substantially larger.Simulation results also show that changes in deep ocean carbonate chemistry substantially lag behind atmospheric CO_(2)change.When CO_(2)returns to its pre-industrial value,the whole-ocean acidity measured by[H^(+)]is 15%-18%larger than the pre-industrial level,depending on the rate of CO_(2)decrease.Our study demonstrates that even if atmospheric CO_(2)can be lowered in the future as a result of net negative CO_(2)emissions,the recovery of some aspects of ocean acidification would take decades to centuries,which would have important implications for the resilience of marine ecosystems.

Biocalcification crisis in the continental shelf under ocean acidification

Ocean acidification(OA)is a persistent challenge for humans and is predicted to have deleterious effects on marine organisms,especially marine calcifiers such as coral and foraminifera.Benthic foraminifera is an important component of sediment in the continental shelf,while little is known about the impact of ocean acidification on benthic foraminifera both at the community and individual level and associated calcium carbonate deposition.We conducted eight months continued culture experiment under the scenario of 400,800,1200 and 1600 ppm pCO_(2)gradients on living benthic foraminifera from four stations in the continental shelf of the West Pacific Ocean.Statistic results showed OA had a negative effect on the abundance of benthic foraminifera.In contrast,the diversity increased roughly under OA conditions implying OA might stimulate the emergence of rare species and promote community diversity to some extent.In addition,we confirmed that the offshore area wasn’t the refuge for benthic foraminifera while the nearshore one had more resistance to moderate acidification.Calcareous species Protelphidium tuberculatum was the dominant species occupying on average 75%in all treatments and its shell diameter,weight and thickness showed a decrease,indicating the decrease of calcification of benthic foraminifera.A relationship between the weight of P.tuberculatum and pCO_(2)(R^(2)=0.96)was established.Based on the present work,calcareous benthic foraminifera deposited 8.57104 t calcium carbonate per year and this might reduce by nearly half and 90%under 800 and 1200 ppm scenarios,which indicates a biocalcification crisis under ongoing OA.This work shows an analogy for palaeoceanic OA and also provides new insights into the sediment of calcium carbonate in the future.

海洋酸化对泥蚶精子运动的影响及作用机理初探

研究分析了未来海洋酸化情景(pH7.8和pH7.4)对典型滩涂贝类泥蚶(Tegillarca granosa)精子运动活力的影响,并从精子运动供能角度探究了其作用机理。研究结果表明,海洋酸化可以显著削弱泥蚶的精子运动速度。由于精子的三磷酸腺苷(ATP)水平与其活力呈显著的正相关,研究检测了不同酸化条件下泥蚶精子的ATP含量及其合成关键酶酶活,实验结果显示精子的ATP含量以及磷酸果糖激酶和丙酮酸激酶活力在酸化条件下均显著下降。此外,精子内的Ca^2+-ATP酶(Ca^2+-ATPase)调节了精子的运动能力,因此实验也探究了海洋酸化对泥蚶精子Ca^2+-ATPase酶活的影响,结果证实该酶活力在海水pH为7.4时被显著抑制。综合本研究结果可以得出,海洋酸化很可能会通过干扰精子细胞内ATP的合成及Ca^2+的调控进而削弱精子的运动速度。

Temperature coefficient of seawater pH as a function of temperature,pH,DIC and salinity

pH is a measure of the hydrogen ion activity in a solution,which is a function of temperature.Under normal seawater conditions,it is well constrained.Nowadays,with an increasing interest in complex environments(e.g.,sea ice),a better understanding of the temperature change on pH under extreme conditions is needed.The objective of this paper was to investigate the temperature coefficient of the seawater pH(△pH/△T)over a wide range of temperature,pH,dissolved inorganic carbon(DIC)and salinity by a method of continuous pH measurement with the temperature change,and to verify the application of CO2SYS for pH conversion under extreme conditions(on the National Bureau of Standards(NBS)scale and the total proton scale).Both experimental results and CO2SYS calculations showed that△pH/△T was slightly affected by temperature over the range of 0℃ to 40℃ and by pH(at 25℃)from 7.8 to 8.5.However,when pH was out of this range,△pH/△T varied greatly with pH value.According to the experimental results,changes in DIC from 1 mmol/kg to 5 mmol/kg and salinity from 20 to 105 had no significant effect on△pH/△T.CO2SYS calculations showed a slight increase in△pH/△T with DIC on both the NBS scale and the total proton scale;and underestimated△pH/△T at high salinity(i.e.,beyond the oceanographic range)on the NBS scale.Nevertheless,CO2SYS is still suitable for pH conversion even under extreme conditions by simply setting the input values of DIC and salinity in CO2SYS within the oceanographic range(e.g.,DIC=2 mmol/kg and S=35).