考洲洋牡蛎养殖海域海-气界面CO2交换通量的时空变化

根据2018年7月、11月和2019年1月、4月对广东考洲洋牡蛎养殖海域进行4个季节调查获得的p H、溶解无机碳(DIC)、水温、盐度、溶解氧(DO)及叶绿素a(Chla)等数据,估算该区域表层海水溶解无机碳体系各分量的浓度、初级生产力(PP)、表层海水CO₂分压[p(CO₂)]和海-气界面CO₂交换通量(FCO₂),分析牡蛎养殖活动对养殖区碳循环的影响。结果表明:牡蛎养殖区表层海水中Chl a、DIC、HCO₃^–和PP显著低于非养殖区;养殖淡季表层海水中pH、DO、DIC、HCO₃^–、和CO₃^2–显著大于养殖旺季,养殖旺季的p(CO₂)和FCO₂显著大于养殖淡季。牡蛎养殖区表层海水夏季、秋季、冬季和春季的海-气界面CO₂交换通量FCO₂平均值分别是(42.04±9.56)、(276...     

Sub-Lethal Effects of Elevated Concentration of CO<Subscript>2</Subscript> on Planktonic Copepods and Sea Urchins

Data concerning the effects of high CO₂ concentrations on marine organisms are essential for both predicting future impacts of the increasing atmospheric CO₂ concentration and assessing the effects of deep-sea CO₂sequestration. Here we review our recent studies evaluating the effects of elevated CO₂ concentrations in seawater on the mortality and egg production of the marine planktonic copepod, Acartia steueri, and on the fertilization rate and larval morphology of sea urchin embryos, Hemicentrotus pulcherrimus and Echinometra mathaei. Under conditions of +10,000 ppm CO₂ in seawater (pH 6.8), the egg production rates of copepods decreased significantly. The survival rates of adult copepods were not affected when reared under increased CO₂ for 8 days, however longer exposure times could have revealed toxic effects of elevated CO₂ concentrations. The fertilization rate of sea urchin eggs of both species decreased with increasing CO₂ concentration. Furthermore, the size of pluteus larvae decreased with increasing CO₂ concentration and malformed skeletogenesis was observed in both larvae. This suggests that calcification is affected by elevated CO₂ in the seawater. From these results, we conclude that increased CO₂ concentration in seawater will chronically affect several marine organisms and we discuss the effects of increased CO₂ on the marine carbon cycle and marine ecosystem. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effects of elevated-CO2 on physiological performance of Bryopsis plumosa

An increase in the level of atmospheric carbon dioxide (CO2) and the resultant rise in CO2 in seawater alter the inorganic carbon concentrations of seawater. This change, known as ocean acidification, ...     

海洋酸化模拟控制系统及其在珊瑚生理研究中的应用

Due to the elevated atmospheric carbon dioxide, ocean acidification(OA) has recently emerged as a research theme in marine biology due to an expected deleterious effect of altered seawater chemistry on calcification. A system simulating future OA scenario is crucial for OA-related studies. Here, we designed an OA-simulated system(OASys) with three solenoid-controlled CO2 gas channels. The OASys can adjust the pH of the seawater by bubbling CO2 gas into seawaters via feedback systems. The OASys is very simple in structure with an integrated design and is new-user friendly with the instruction. Moreover, the OASys can monitor and record real-time pH values and can maintain pH levels within 0.02 pH unit. In a 15-d experiment, the OASys was applied to simulate OA in which the expected target pH values were 8.00, 7.80 and 7.60 to study the calcifying response of Galaxea fascicularis. The results showed daily mean seawater pH values held at pH 8.00±0.01, 7.80±0.01 and 7.61±0.01 over15 d. Correspondingly, the coral calcification of G. fascicularis gradually decreased with reduced pH.     

The international at-sea intercomparison of fCO2 systems during the R/V Meteor Cruise 36/1 in the North Atlantic Ocean

The ‘International Intercomparison Exercise of fCO₂ Systems’ was carried out in 1996 during the R/V Meteor Cruise 36/1 from Bermuda/UK to Gran Canaria/Spain. Nine groups from six countries (Australia, Denmark, France, Germany, Japan, USA) participated in this exercise, bringing together 15 participants with seven underway fugacity of carbon dioxide (fCO₂) systems, one discrete fCO₂ system, and two underway pH systems, as well as systems for discrete measurement of total alkalinity and total dissolved inorganic carbon. Here, we compare surface seawater fCO₂ measured synchronously by all participating instruments. A common infrastructure (seawater and calibration gas supply), different quality checks (performance of calibration procedures for CO₂, temperature measurements) and a common procedure for calculation of final fCO₂ were provided to reduce the largest possible amount of controllable sources of error. The results show that under such conditions underway measurements of the fCO₂ in surface seawater and overlying air can be made to a high degree of agreement (±1 μatm) with a variety of possible equilibrator and system designs. Also, discrete fCO₂ measurements can be made in good agreement (±3 μatm) with underway fCO₂ data sets. However, even well-designed systems, which are operated without any obvious sign of malfunction, can show significant differences of the order of 10 μatm. Based on our results, no “best choice” for the type of the equilibrator nor specifics on its dimensions and flow rates of seawater and air can be made in regard to the achievable accuracy of the fCO₂ system. Measurements of equilibrator temperature do not seem to be made with the required accuracy resulting in significant errors in fCO₂ results. Calculation of fCO₂ from high-quality total dissolved inorganic carbon (C_T) and total alkalinity (A_T) measurements does not yield results comparable in accuracy and precision to fCO₂ measurements.     

Effects of acidified seawater on calcification,photosynthetic efficiencies and the recovery processes from strong light exposure in the coral Stylophora pistillata

The aim of this study was to investigate whether coral photosynthetic efficiencies and recovery processes are affected by CO₂‐driven ocean acidification in symbiont photosynthesis and coral calcification. We investigated the effects of five CO₂ partial pressure (pCO₂) levels in adjusted seawater ranging from 300 μatm (pre‐industrial) to 800 μatm (near‐future) and strong and weak light intensity on maximum photosynthetic efficiency and calcification of a branching coral, Stylophora pistillata, as this species has often been used in rearing experiments to investigate the effects of acidified seawater on calcification and photosynthetic algae of corals. We found that, the photosynthetic efficiencies and recovery patterns under different light conditions did not differ among pCO₂ treatments. Furthermore, calcification of S. pistillata was not affected by acidified seawater under weak or strong light conditions. Our results indicate that the photosynthetic efficiency and calcification of S. pistillata are insensitive to changes in ocean acidity.     

Effects of CO<Subscript>2</Subscript> Enrichment on Marine Phytoplankton

Rising atmospheric CO₂ and deliberate CO₂ sequestration in the ocean change seawater carbonate chemistry in a similar way, lowering seawater pH, carbonate ion concentration and carbonate saturation state and increasing dissolved CO₂ concentration. These changes affect marine plankton in various ways. On the organismal level, a moderate increase in CO₂ facilitates photosynthetic carbon fixation of some phytoplankton groups. It also enhances the release of dissolved carbohydrates, most notably during the decline of nutrient-limited phytoplankton blooms. A decrease in the carbonate saturation state represses biogenic calcification of the predominant marine calcifying organisms, foraminifera and coccolithophorids. On the ecosystem level these responses influence phytoplankton species composition and succession, favouring algal species which predominantly rely on CO₂ utilization. Increased phytoplankton exudation promotes particle aggregation and marine snow formation, enhancing the vertical flux of biogenic material. A decrease in calcification may affect the competitive advantage of calcifying organisms, with possible impacts on their distribution and abundance. On the biogeochemical level, biological responses to CO₂ enrichment and the related changes in carbonate chemistry can strongly alter the cycling of carbon and other bio-active elements in the ocean. Both decreasing calcification and enhanced carbon overproduction due to release of extracellular carbohydrates have the potential to increase the CO₂ storage capacity of the ocean. Although the significance of such biological responses to CO₂ enrichment becomes increasingly evident, our ability to make reliable predictions of their future developments and to quantify their potential ecological and biogeochemical impacts is still in its infancy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Stable isotope composition of modern bryozoan skeletal carbonate from the Otago Shelf,New Zealand

The oxygen (δ¹⁸O) and carbon (δ¹³C) isotope ratios of 10 species of living Bryozoa collected from the Otago Shelf, New Zealand were analysed to assess the extent to which isotopic equilibrium (relative to inorganic equilibrium isotope fractionation) is attained during the precipitation of skeletal calcium carbonate. The data reveal that whereas eight species of Bryozoa synthesise skeletal carbonate in apparent oxygen isotope equilibrium with respect to environmental conditions, two species (Celleporina grandis and Hippomonavella flexuosa) yield δ¹⁸O_calcite values which indicate significant disequilibrium oxygen isotope fractionation during calcification. Sufficient data are available from one species (C. grandis) to demonstrate that disequilibrium is probably related to kinetic factors associated with diffusion‐controlled transport of HCO₃‐ to the site of calcite precipitation. Carbon isotope signatures indicate significant departures from inorganic isotope equilibrium in all but one bryozoan species (Hippomenella vellicata). Although greater uncertainties are associated with estimates of the isotopic composition of total dissolved inorganic carbon (δ¹³C_SDIC), the data suggest that two factors—kinetic fractionation and incorporation of respiratory CO₂—are important in controlling carbon isotope disequilibrium. Where bryozoan species exhibit evidence for disequilibrium in both oxygen and carbon isotope systems (C. grandis, H. flexuosa), it is likely that kinetic factors are primarily responsible for observed departures from carbon isotope equilibrium. In contrast, the probable explanation for those species which display evidence for carbon isotope disequilibrium only, is that skeletal carbonate is precipitated from a DIC pool modified by the incorporation of respiratory CO₂. Differences between the carbon isotope composition of skeletal elements from the same species and co‐existing species living in the same community suggests that significant variations may occur in the extent to which marine DIC and respiratory CO₂ are utilised during calcification. Additional studies of carbon pathways associated with calcification are required to assess the relative effects of kinetic, metabolic, and environmental factors on the carbon isotopic composition of bryozoan skeletal carbonate.     

Effects of seawater acidification by ocean CO<Subscript>2</Subscript> sequestration on bathypelagic prokaryote activities

We investigated the effects of seawater acidification induced by ocean CO₂ sequestration on bathypelagic prokaryotes. We simulated acidification conditions by bubbling high-CO₂ air or adding chemical buffer solutions to seawater samples in order to examine changes in total cell counts, heterotrophic production rate, direct viable cell count, and relative abundance of Bacteria and Archaea. Considerable suppression of prokaryotic activities was observed at pH 7.0 or lower, especially in samples enriched with organic matter. The relative abundance of Archaea increased with increasing CO₂ concentration. We found that seawater acidification can potentially alter heterotrophic activities and community structure of bathypelagic prokaryotes.     

Coulometric total carbon dioxide analysis for marine studies: maximizing the performance of an automated gas extraction system and coulometric detector

A global survey of the distribution of dissolved CO₂ taking advantage of sampling opportunities provided by the World Ocean Circulation Experiment: World Hydrographic Program (WOCE-WHP) is being carried out through 1995. Goals include the measurement of oceanic inorganic carbon transport and the development of a data base from which future fossil-fuel CO₂ build-up can be monitored. The analytical method selected for total carbon dioxide (C_T) is gas extraction of acidified seawater with coulometric titration of the acid formed by the resultant carbon dioxide and monoethanolamine. To combine high accuracy and precision (± 1.5 μmol/kg for C_T ≥ 2000 μmol/kg) with a high rate of analysis, we have modified an automated single-parameter system. Following prototype development between 1987 and 1990, an instrument emerged with the acronym Somma standing for single-operator multiparameter metabolic analyzer. Improved functional and operating procedures have integrated electronic calibration, CO₂ gas calibration, and sample analysis with automated pressure, temperature, and conductivity (salinity) sensing into a single convenient transportable package.     

Uptake of atmospheric carbon dioxide in Arctic shelf seas: evaluation of the relative importance of processes that influence pCO2 in water transported over the Bering–Chukchi Sea shelf

The uptake of atmospheric carbon dioxide in the water transported over the Bering–Chukchi shelves has been assessed from the change in carbon-related chemical constituents. The calculated uptake of atmospheric CO₂ from the time that the water enters the Bering Sea shelf until it reaches the northern Chukchi Sea shelf slope (1 year) was estimated to be 86±22 g C m⁻² in the upper 100 m. Combining the average uptake per m³ with a volume flow of 0.83×10⁶ m³ s⁻¹ through the Bering Strait yields a flux of 22×10¹² g C year⁻¹. We have also estimated the relative contribution from cooling, biology, freshening, CaCO₃ dissolution, and denitrification for the modification of the seawater pCO₂ over the shelf. The latter three had negligible impact on pCO₂ compared to biology and cooling. Biology was found to be almost twice as important as cooling for lowering the pCO₂ in the water on the Bering–Chukchi shelves. Those results were compared with earlier surveys made in the Barents Sea, where the uptake of atmospheric CO₂ was about half that estimated in the Bering–Chukchi Seas. Cooling and biology were of nearly equal significance in the Barents Sea in driving the flux of CO₂ into the ocean. The differences between the two regions are discussed. The loss of inorganic carbon due to primary production was estimated from the change in phosphate concentration in the water column. A larger loss of nitrate relative to phosphate compared to the classical ΔN/ΔP ratio of 16 was found. This excess loss was about 30% of the initial nitrate concentration and could possibly be explained by denitrification in the sediment of the Bering and Chukchi Seas.     

The contribution of atmospheric acid deposition to ocean acidification in the subtropical North Atlantic Ocean

The absorption of anthropogenic CO₂ and atmospheric deposition of acidity can both contribute to the acidification of the global ocean. Rainfall pH measurements and chemical compositions monitored on the island of Bermuda since 1980, and a long-term seawater CO₂ time-series (1983–2005) in the subtropical North Atlantic Ocean near Bermuda were used to evaluate the influence of acidic deposition on the acidification of oligotrophic waters of the North Atlantic Ocean and coastal waters of the coral reef ecosystem of Bermuda. Since the early 1980's, the average annual wet deposition of acidity at Bermuda was 15 ± 14 mmol m^− 2 year^− 1, while surface seawater pH decreased by 0.0017 ± 0.0001 pH units each year. The gradual acidification of subtropical gyre waters was primarily due to uptake of anthropogenic CO₂. We estimate that direct atmospheric acid deposition contributed 2% to the acidification of surface waters in the subtropical North Atlantic Ocean, although this value likely represents an upper limit. Acidifying deposition had negligible influence on seawater CO₂ chemistry of the Bermuda coral reef, with no evident impact on hard coral calcification.     

Alterations in seawater pH and CO2 affect calcification and photosynthesis in the tropical coralline alga, Hydrolithon sp. (Rhodophyta)

Calcification in the marine environment is the basis for the accretion of carbonate in structures such as coral reefs, algal ridges and carbonate sands. Among the organisms responsible for such calcification are the Corallinaceae (Rhodophyta), recognised as major contributors to the process world-wide. Hydrolithon sp. is a coralline alga that often forms rhodoliths in the Western Indian Ocean. In Zanzibar, it is commonly found in shallow lagoons, where it often grows within seagrass beds and/or surrounded by green algae such as Ulva sp. Since seagrasses in Zanzibar have recently been shown to raise the pH of the surrounding seawater during the day, and since calcification rates are sensitive to pH, which changes the saturation state of calcium carbonate, we measured the effects of pH on photosynthetic and calcification rates of this alga. It was found that pH had significant effects on both calcification and photosynthesis. While increased pH enhanced calcification rates both in the light and in the dark at pH >8.6, photosynthetic rates decreased. On the other hand, an increase in dissolved CO₂ concentration to 26 μmol kg⁻¹ (by bubbling with air containing 0.9 mbar CO₂) caused a decrease in seawater pH which resulted in 20% less calcification after 5 days of exposure, while enhancing photosynthetic rates by 13%. The ecological implications of these findings is that photosynthetically driven changes in water chemistry by surrounding plants can affect calcification rates of coralline algae, as may future ocean acidification resulting from elevated atmospheric CO₂.     

Theoretical considerations about the reactions of calcification in sea water

We examine the concentration variations of the different parameters X of the carbonate system in seawater when calcium carbonate precipitation occurs. Variations are expressed as ∂[X]/∂[Ca²⁺]. Four different cases are considered: spontaneous chemical precipitation; calcification combined with photosynthetic activity under a constant ΔCT/Δ[Ca²⁺] ratio; precipitation under constant p_CO2 and precipitation under constant [Ca²⁺]·[CO₃²⁻] ionic concentration product. The last condition should be maintained by an ecosystem which, thanks to the regulation of its calcifying and photosynthetic activity, would absorb 1 mol of carbon for organic tissue each time 1 mol of CaCO₃ is formed. This stoichiometric ratio would allow the activity of these biological communities to go on in practically closed systems during periods compatible with their growth or development cycles.     

Recent increase in surface fCO<Subscript>2</Subscript> in the western subtropical North Pacific

We observed unusually high levels (> 440 μatm) of carbon dioxide fugacity (fCO₂) in surface seawater in the western subtropical North Pacific, the area where Subtropical Mode Water is formed, during summer 2015. The NOAA Kuroshio Extension Observatory moored buoy located in this region also measured high CO₂ values, up to 500 μatm during this period. These high sea surface fCO₂ (fCO_2SW) values are explained by much higher normalized total dissolved inorganic carbon and slightly higher normalized total alkalinity concentrations in this region compared to the equatorial Pacific. Moreover, these values are much higher than the climatological CO₂ values, even considering increasing atmospheric CO₂, indicating a recent large increase in sea surface CO₂ concentrations. A large seasonal change in sea surface temperature contributed to higher surface fCO_2SW in the summer of 2015.     

Partial Pressure of Carbon Dioxide in Coral Reef Lagoon Waters: Comparative Study of Atolls and Barrier Reefs in the Indo-Pacific Oceans

Factors controlling the CO₂ system parameters, including the partial pressure of CO₂ (PCO₂) in coral reef waters, were investigated in three mid-oceanic reefs of the Indo-Pacific region. Surface water PCO₂ in the lagoons of Majuro Atoll and Palau barrier reef in the Pacific were 25 µatm and 48 µatm higher than those of the offshore waters, respectively, while South Male Atoll lagoon of the Maldives in the Indian Ocean exhibited relatively small difference in PCO₂ compared to the offshore water. Observations from Majuro Atoll and Palau barrier reef are consistent with the view that calcium carbonate production predominates in coral reefs. On the other hand, results from South Male Atoll can be attributed to the thorough flushing of the lagoon, which is connected to the open ocean by numerous deep channels. The offshore-lagoon PCO₂ difference depends on system-level net organic-to-inorganic carbon production ratio while reef topography, especially residence time of the lagoon, has a secondary effect on the magnitude of the offshore-lagoon difference. A potential for releasing CO₂ might be more evident in an enclosed atoll where the reef water has a longer residence time. Oceanic atoll and barrier reef lagoons, which are in the terminal stage of evolutionary history of oceanic volcanic islands, have the potential to release CO₂ to the atmosphere.     

天津近岸浮游植物群落对海洋酸化和硝酸盐加富的响应

为了评估海洋酸化和富营养化耦合作用对近海浮游生态环境的影响,本研究以天津市近岸海域浮游植物群落的生物地球化学指标为研究对象,分别采用一次性及连续培养的方式模拟自然水华及稳态条件,探究其对二氧化碳(CO₂)和硝酸盐浓度变化及二者耦合作用的响应。实验条件设置如下:1)对照:二氧化碳分压p(CO₂)40.53 Pa、无硝酸盐添加;2)酸化:p(CO₂)101.3 Pa、无硝酸盐添加;3)加N:p(CO₂)40.53 Pa、添加硝酸盐50 μmol·L^–1;4)酸化加N:p(CO₂)101.3 Pa、添加硝酸盐50 μmol·L^–1。实验结果表明,硝酸盐加富比酸化更加显著地促进浮游植物群落总叶绿素(Chl a)生物量及颗粒有机碳(POC)和颗粒有机氮(PON)积累,酸化和加N使浮游植物群落粒径大小升高。连续培养实验表明,酸化和N加富对Chl a、生物硅(BSi)、PON浓度、PON与颗粒有机磷(POP)比值(N/P)、POC与BSi比值(C/BSi)及沉降速率有协同交互作用,对POP和POC浓度及POC与PON比值(C/N)有拮抗性交互作用。在一次性培养后,酸化显著降低了浮游植物群落的沉降速率;而在连续培养后,酸化和N加富使浮游植物群落沉降速率显著升高。这些结果表明酸化和N加富对与近岸浮游植物相关的生物地球化学循环及在不同生长阶段的种群碳沉降存在不同的潜在影响及交互效应。     

The influence of macronitrogen (NO3- and NH4+) addition with Ulva pertusa on dissolved inorganic carbon system

The influence of macronitrogen (NO - 3 and NH + 4 ) addition with Ulva pertusa on dissolved inorganic carbon system in seawater was studied. The results indicate that p(CO 2 ) and HCO 3 concentration decrease significantly, while pH and CO 2- 3 concentration increase significantly. When the concentration of NO 3 was less than 71 μmol/dm 3 or NH + 4 was less than 49.7 μmol/dm 3 , dissolved inorganic carbon (DIC) absorption rates by Ulva pertusa generally increased with the increasing of nitrogen concentration. The DIC decreased 151 μmol/dm 3 with the addition of 71 μmol/dm 3 NO 3 and decreased 232 μmol/dm 3 with the addition of 49.7 μmol/dm 3 NH + 4 after the experiment compared with DIC measured without nitrogen addition. A significant negative-correlation was found between c(DIC) and growth rate (μ) of Ulva pertusa (r = -0.91, P <0.000 1, n=11). NH + 4 had more influence on the species of inorganic carbon system than NO 3 .     

Annual cycle of fCO2 under sea-ice and in open water in Prydz Bay, East Antarctica

The annual cycle of dissolved nutrients and the fugacity of CO₂ (fCO₂), calculated from the concentration of dissolved inorganic carbon (DIC) and pH, was studied over a 14-month long period (December 1993 to February 1995) at a site in Prydz Bay near Davis Station, Vestfold Hills, East Antarctica. Significant spring decreases in fCO₂ began under the sea-ice in mid-October, when both water column and sea-ice algal activity resulted in the removal of nutrients and DIC and increased pH. Minimum fCO₂ (<100 μatm) and lowest nutrient and DIC concentrations occurred in December and January. The low summer fCO₂ values were clearly the result of biological activity. The seasonal depletion of dissolved nitrate reached 85% in mid-summer when chlorophyll-a concentrations exceeded 15 mg m⁻³. Oceanic uptake of carbon dioxide from the atmosphere, calculated from the fugacity difference and daily wind speeds, averaged more than 30 mmol m⁻² day⁻¹ during the summer ice-free period. This exchange replaced approximately half of the DIC consumed by biological activity. Apparent nutrient utilisation ratios (C/N/P) were close to Redfield values. In autumn fCO₂ began to rise, continuing slowly well into winter, and reaching a maximum close to modern atmospheric values between July and September. This increase can be attributed to a combination of local remineralisation of organic carbon in the water column and the steady increase in the mixing depth of the water column. At first glance, this suggests that air–sea equilibration occurred in winter despite the sea-ice cover, perhaps by horizontal circulation from regions outside the pack ice, or through openings in the ice. However, the persistent 15 to 20% undersaturation of dissolved oxygen throughout the winter suggests an alternate explanation. The late winter fCO₂ level may represent a characteristic established by global circulation, so that as a result of increasing atmospheric CO₂ concentrations, these Antarctic waters are in transition from being a winter-time source of CO₂ to the atmosphere to becoming a sink. Our fCO₂ observations emphasize the need to address seasonal variations in assessing Antarctic contributions to the oceanic control of atmospheric CO₂.     

The inorganic carbon system in the coastal upwelling region west of Vancouver Island,Canada

We present inorganic carbon data from the coastal upwelling region west of Vancouver Island, Canada $\text{(∼48.5°}\text{N}\text{,}\text{126°}\text{W}\text{)}$ directly after an upwelling event and during summer downwelling in July 1998. The inner-shelf buoyancy current, the outer-shelf and the slope regions are contrasted for both wind regimes (up- and downwelling). Results show strong biological drawdown of the partial pressure of carbon dioxide (pCO₂) in response to upwelling over the outer-shelf. In contrast, measured pCO₂ is exceptionally high $\text{(p}\text{CO}{}_2\text{>1000}\text{ppm}\text{)}$ in the inner-shelf current, where biological uptake of carbon is consistently large. The biological C:N uptake ratio appears to increase when nitrogen becomes limiting (during downwelling), while the POC:PON ratio is relatively constant (slightly lower than the Redfield ratio) suggesting that excess carbon uptake does not go into the POC pool. As expected, large cells dominate where measured primary productivity is greatest. Sub-surface inorganic carbon (and pCO₂) is high over the shelf. We suggest that carbon concentrations may be higher in coastal waters because of remineralization associated with high productivity that is confined to a smaller volume of water by bathymetry. At the coast these sub-surface concentrations are more efficiently mixed into the surface (especially during winter) relative to deeper offshore regions. Thus, despite high primary production, coastal waters may not aid in sequestration of atmospheric carbon.