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The absorption of atmospheric carbon dioxide (CO2) into the ocean lowers the pH of the waters. This so-called ocean acidification could have important consequences for marine ecosystems. To better understand the extent of this ocean acidification in coastal waters, we conducted hydrographic surveys along the continental shelf of western North America from central Canada to northern Mexico. We observed seawater that is undersaturated with respect to aragonite upwelling onto large portions of the continental shelf, reaching depths of ∼40 to 120 meters along most transect lines and all the way to the surface on one transect off northern California. Although seasonal upwelling of the undersaturated waters onto the shelf is a natural phenomenon in this region, the ocean uptake of anthropogenic CO2 has increased the areal extent of the affected area.
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DOI: 10.1126/science.1155676
, 1490 (2008); 320Science
et al.Richard A. Feely,
Water onto the Continental Shelf
Evidence for Upwelling of Corrosive "Acidified" (this information is current as of February 9, 2009 ):
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Evidence for Upwelling of Corrosive
Acidified Water onto the
Continental Shelf
Richard A. Feely,
Christopher L. Sabine,
J. Martin Hernandez-Ayon,
Debby Ianson,
Burke Hales
The absorption of atmospheric carbon dioxide (CO
) into the ocean lowers the pH of the waters.
This so-called ocean acidification could have important consequences for marine ecosystems. To
better understand the extent of this ocean acidification in coastal waters, we conducted
hydrographic surveys along the continental shelf of western North America from central Canada
to northern Mexico. We observed seawater that is undersaturated with respect to aragonite
upwelling onto large portions of the continental shelf, reaching depths of ~40 to 120 meters along
most transect lines and all the way to the surface on one transect off northern California. Although
seasonal upwelling of the undersaturated waters onto the shelf is a natural phenomenon in this
region, the ocean uptake of anthropogenic CO
has increased the areal extent of the affected area.
ver the past 250 years, the release of
carbon d ioxide ( CO
) from industrial and
agricultural activities has resulted in atmo-
spheric CO
concentrations that have increased by
about 100 parts per million (ppm). The atmo-
spheric concentration of CO
is now higher than
it has been for at least the past 650,000 years, and
is expected to continue to rise at an increasing
rate, leading to pronounced changes in our cli-
mate by the end of this century (1). Since the
beg in ni ng of the in du st ri a l era, the oceans have
absorbed ~127 ± 18 billion metric tons of carbon
as CO
from the atmosphere, or about one-third
of the anthropogenic carbon emissions released
(2). This process of absorption of anthropogenic
has benefited humankind by substantially
reducing the greenhouse gas concentrations in
the atmosphere and minimizing some of the im-
pacts of global warming. However , the oceans
daily uptake of 22 million metric tons of CO
a sizable impact on its chem i s t r y and bio l o gy.
Recent hydrogra phic surveys and modeling studies
have confirmed that the uptake of anthropogenic
by the oceans has resulted in a lowering of
seawater pH by about 0.1 since the beginning of
the industrial revolution (37). In the coming
decades, this phenomenon, called ocean acidi-
fication, could affect some of the most funda-
mental biological and geochemical processes of
the sea and seriously alter the fundamental struc-
ture of pelagic and benthic ecosystems (8).
Estimates of future atmospheric and oceanic
concentrations, based on the Intergovernmental
Panel on Climate Change (IPCC) CO
scenarios and general circulation models, indicate
that atmospheric CO
concentration s could exceed
500 ppm by the middle of this century , and 800
ppm near the end of the century . This increase would
result in a decrease in surface-wate r pH of ~ 0.4 by
the end of the century , and a corresponding 50%
decrease in carbonate ion concentration (5, 9). Such
rapid changes are likely to negatively affect marine
ecosystems, seriously jeopardizing the multifaceted
economies that currently depend on them (10).
The reaction of CO
with seawater reduces
the availability of carbonate ions that are neces-
sary for calcium carbonate (CaCO
shell formation for marine organisms such as
corals, marine plankton, and shellfish. The extent
to which the organisms are affected depends
saturation state (W), which
is the product of the concentrations of Ca
divided b y the apparent stoichiometric
solubility product for either aragonite or calcite:
= [Ca
where the calcium concentration is estimated
from the salinity, and the carbonate ion con-
Pacific Marine Environmental Laboratory/National Oceanic and
Atmospheric Administration, 7600 Sand Point Way NE, Seattle,
WA 981156349, USA.
Instituto de Investigaciones Oceano-
logicas, Universidad Autonoma de Baja California, Km. 103 Carr.
Tijuana-Ensenada, Ensenada, Baja California, Mexico.
and Oceans Canada, Institute of Ocean Science, Post Office Box
6000, Sidney, BC V8L 4B2, Canada.
College of Oceanic and
Atmospheric Sciences, Oregon State University, 104 Ocean
Administration Building, Corvallis, OR 973315503, USA.
*To whom correspondence should be addressed. E-mail:
134°W 130°W 126°W 122°W 118°W 114°W
Depth (m)
Fig. 1. Distribution of the depths of the undersaturated water (aragonite saturation < 1.0; pH < 7.75) on
the continental shelf of western North America from Queen Charlotte Sound, Canada, to San Gregorio
Baja California Sur, Mexico. On transect line 5, the corrosive water reaches all the way to the surface in the
inshore waters near the coast. The black dots represent station locations.
13 JUNE 2008 VOL 320 SCIENCE
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centration is calculated from the dissolved in-
organic carbon (DIC) and total alkalinity (TA)
measurements (11). In regions where W
is > 1.0, the formation of shells and skeletons
is favored. Below a value of 1.0, the water is
corrosive and dissolution of pure aragonite and
unprotected aragonite shells will begin to occur
(12). Recent studies have shown that in many
regions of the ocean, the aragonite saturation ho-
rizon shoaled as much as 40 to 200 m as a direct
consequence of the uptake of anthropogenic CO
(3, 5, 6). It is shallowest in the northeastern
Pacific Ocean, only 100 to 300 m from the ocean
surface, allowing for the transport of under-
saturated waters onto the continental shelf during
periods of upwelling.
In May and June 2007, we conducted the
North American Carbon Program (NACP) West
Coast Cruise on the Research Ship Wecoma along
the continental shelf of western North America,
completing a series of 13 cross-shelf transects
from Queen Charlotte Sound, Canada, to San
Gregorio Baja California Sur, Mexico (Fig. 1).
Full water column conductivity-temperature-depth
rosette stations were occupied at specified locations
along each transect (Fig. 1). Water samples were
collected in modified Niskin-type bottles and an-
alyzed for DIC, TA, oxygen, nutrients, and dis-
solved and particulate organic carbon. Aragonite
and calcite saturation, seawater pH (pH
), and
partial pressure of CO
) were calculated
from the DIC and TA data (11).
The central and southern coastal region off
western North America is strongly influenced by
seasonal upwelling, which typically begins in early
spring when the Aleutian low-pressure system
moves to the northwest and the Pacific High moves
northward, resulting in a strengthening of the
northwesterly winds (13, 14). These winds drive
net surface-water Ekman transport offshore, which
induces the upwelling of CO
-rich, intermediate-
depth (100 to 200 m) offshore waters onto the
continental shelf. The upwelling lasts until late
summer or fall, when winter storms return.
During the cruise, various stages and strengths
of upwelling were observed from line 2 off central
Vancouver Island to line 11 off Baja California,
Mexico. We observed recent upwelling on lines
5 and 6 near the Oregon-California border. Co-
incident with the upwelled waters, we found evi-
dence for undersaturated, low-pH seawater in the
bottom waters as depicted by W
values < 1.0
and pH values < 7.75. The corrosive waters
reached mid-shelf depths of ~40 to 120 m along
lines 2 to 4 and lines 7 to 13 (Fig. 1). In the region
of the strongest upwelling (line 5), the isolines of
= 1.0, DIC = 2190, and pH = 7.75 closely
followed the 26.2 potential density surface (Fig.
2). This density surface shoaled from a depth of
~150 m in the offshore waters and breached the
surface over the shelf near the 100-m bottom
contour , ~ 40 km from the coast. This shoaling of
the density surfaces and CO
-rich waters as one
approaches land is typical of strong coastal up-
welling conditions (1518). The surface-water
on the 26.2 potential density surface was
about 850 matm near the shelfbreak and higher
inshore (Fig. 2), possibly enhanced by respiration
processes on the shelf (17). These results indicate
that the upwelling process caused the entire water
column shoreward of the 50-m bottom contour to
become undersaturated with respect to aragonite,
a condition that was not predicted to occur in open-
ocean surface waters until 2050 (5). On line 6, the
next transect south, the undersaturated water was
close to the surface at ~22 km from the coast. The
lowest W
values (<0.60) observed in the near-
bottom waters of the continental shelf corre-
sponded with pH values close to 7.6. Because the
calcite saturation horizon is located between 225
and 400 m in this part of the northeastern Pacific
(19), it is still too deep to shoal onto the continental
shelf. Nevertheless, the calcite saturations values
drop in the core of the upwelled water (W
As noted, the North Pacific aragonite satura-
tion horizons are among the shallowest in the
global ocean (3). The uptake of anthropogenic
has caused these horizons to shoal by 50 to
100 m since preindustrial times so that they are
within the density layers that are currently being
upwelled along the west coast of North America.
126°W 125.5°W 125°W 124.5°W
Temp (°C)
(µmol kg
Depth (m)Depth (m)Depth (m)Depth (m)Depth (m)
Fig. 2. Vertical sections of (A) temperature, (B) aragonite saturation, (C)pH,(D)DIC,and(E) pCO
transect line 5 off Pt. St. George, California. The potential density surfaces are superimposed on the
temperature section. The 26.2 potential density surface delineates the location of the first instance in
which the undersaturated water is upwelled from depths of 150 to 200 m onto the shelf and outcropping
at the surface near the coast. The red dots represent sample locations. SCIENCE VOL 320 13 JUNE 2008
on February 9, 2009 www.sciencemag.orgDownloaded from
Although much of the corrosive character of these
waters is the natural result of respiration processes at
intermediate depths below the euphotic zone, this
region continues to accumulate more anthropogenic
and, therefore, the upwelling processes will
expose coastal organisms living in the water column
or at the sea floor to less saturated waters, exacerbat-
ing the biological impacts of ocean acidification.
On the basis of our observed O
values and es-
timated O
consumption rates on the same density
surfaces (1820), the upwelled water off northern
California (line 5) was last at the surface about
50 years ago, when atmospheric CO
was about
65 ppm lower than it is today . The open-ocean an-
thropogenic CO
distributions in the Pacific have
been estimated previously (4, 19, 21). By determin-
ing the density dependence of anthropogenic CO
distributions in the eastern-most North Pacific sta-
tions of the Sabine et al.(21)dataset,weestimate
that these upwelled waters contain ~31 ± 4 mmol kg
anthropogenic CO
(fig. S2). Removing this signal
from the DIC increases the aragonite saturation
state of the waters by about 0.2 units. Thus, without
the anthropogenic signal, the equilibrium aragonite
saturation level (W
= 1) would be deeper by
about 50 m across the shelf, and no undersaturated
waters would reach the surface. W ater already in
transit to upwelling centers carries increasing an-
thropogenic CO
and more corrosive conditions to
the coastal oceans of the future. Thus, the under-
saturated waters, which were mostly a problem for
benthic communities in the deeper waters near the
shelf break in the preindustrial era, have shoaled
closer to the surface and near the coast because of
the additional inputs of anthropogenic CO
These observations clearly show that seasonal
upwelling processes enhance the advancement of
the corrosive deep water into broad regions of the
North American western continental shelf. Because
the region experiences seasonal periods of enhanced
aragonite undersaturation, it is important to under-
stand how the indigenous organisms deal with this
exposure and whether future increases in the range
and intensity of the corrosiveness will affect their
survivorship. Presently, little is known about how
this intermittent exposure to corrosive water might
affect the development of larval, juvenile, and adult
stages of aragonitic calcifying organisms or finfish
that populate the neritic and benthic environments in
this region and fuel a thriving economy . Laboratory
and mesocosm experiments show that these changes
in saturation state may cause substantial changes in
overall calcification rates for many species of marine
calcifiers including corals, coccolithophores, foram-
inifera, and pteropods, which are a major food
source for local juvenile salmon (8, 2230). Similar
decreases in calcification rates would be expected
for edible mussels, clams, and oysters (22, 31). Other
research indicates that many species of juvenile fish
gions are highly sensitive to higher-than-normal
concentrations such that high rates of mortality
are directly correlated with the higher CO
centrations (31, 32). Although comprehensiv e field
studies of organisms and their response to sporadic
increases in CO
along the western North American
coast are lacking, current studies suggest that further
research under field condition s is warranted. Our
results show that a large section of the North Amer-
ican continental shelf is affected by ocean acidifi-
cation. Other continental sh el f regio ns may also
be affected where anthropogenic CO
water is being upwelled onto the shelf.
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Supporting Online Material
Materials and Methods
Figs. S1 and S2
25 January 2008; accepted 13 May 2008
Published online 22 May 2008;
Include this information when citing this paper.
Regulation of Hepatic Lipogenesis
by the Transcription Factor XBP1
Ann-Hwee Lee,
* Erez F. Scapa,
David E. Cohen,
Laurie H. Glimcher
Dietary carbohydrates regulate hepatic lipogenesis by controlling the expression of critical enzymes
in glycolytic and lipogenic pathways. We found that the transcription factor XBP1, a key regulator of
the unfolded protein response, is required for the unrelated function of normal fatty acid synthesis
in the liver. XBP1 protein expression in mice was elevated after feeding carbohydrates and
corresponded with the induction of critical genes involved in fatty acid synthesis. Inducible, selective
deletion of XBP1 in the liver resulted in marked hypocholesterolemia and hypotriglyceridemia,
secondary to a decreased production of lipids from the liver. This phenotype was not accompanied by
hepatic steatosis or compromise in protein secretory function. The identification of XBP1 as a regulator
of lipogenesis has important implications for human dyslipidemias.
epatic lipid synthesis increases upon in-
gestion of excess carbohydrates, which
are converted into triglyceride (TG) in
the liver and transported to adipose tissue for
energy storage. Dysregulation of hepatic lipid
metabolism is closely related to the development
of metabolic syndrome, a condition characterized
by central obesity, dyslipidemia, elevated blood
glucose, and hypertension (1). In mammals, he-
patic lipid metabolism is controlled by transcrip-
tion factors, such as liver X receptor (LXR), sterol
regulatory elementbinding proteins (SREBPs),
and carbohydrate response elementbinding pro-
tein (ChREBP), that regulate the expression of
Department of Immunology and Infectious Diseases,
Harvard School of Public Health, Boston, MA 02115,
Department of Medicine, Harvard Medical School,
Boston, MA 02115, USA.
Division of Gastroenterology, Brigham
and Womens Hospital, Boston, MA 02115, USA.
*To whom correspo ndence should be addressed. E-mail: (L.H.G.); ahlee@hsph.harvard.
edu (A.-H.L.)
13 JUNE 2008 VOL 320 SCIENCE www.sciencemag.org1492
on February 9, 2009 www.sciencemag.orgDownloaded from
... Hypercapnic conditions can already be found in modern ocean environments, including upwelling regions like the California Current Large Marine Ecosystem (CCLME) in the Northeast Pacific Ocean (Feely et al., 2018). In this region, seasonal, wind-driven upwelling along the US West Coast transports subsurface waters, naturally low in pH, Ω Ar , and dissolved oxygen (O 2 ) and elevated in pCO 2 due to prior organic matter remineralization, to the continental shelf environment (Feely et al., 2008;Gruber et al., 2012;Hauri et al., 2009Hauri et al., , 2013. Subsurface remineralization inherently links high pCO 2 and low pH values to low O 2 values, which can be intensified on the continental shelf by locally driven processes (Chan et al., 2017(Chan et al., , 2019Feely et al., 2016Feely et al., , 2018. ...
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Shallow aquatic environments are characterized by strong environmental variability. For ectotherms, temperature is the main driver of metabolic activity, thus also shaping performance. Ingestion rates in mysids are fast responses, influenced by metabolic and behavioral activity. We examined ingestion rates of the mysid Neomysis integer, collected in the Baltic Sea, after one-week exposure to different constant and fluctuating temperature regimes (5, 10, 15, 20°C and 9 ± 5, 14 ± 5°C, respectively). To investigate possible differences between sexes, thermal performance curves (TPCs) were established for female and male mysids based on ingestion rates measured at constant temperatures. TPCs of ingestion rates at constant temperatures differed between sexes, with female mysids showing a higher total ingestion rate as well as a higher thermal optimum compared to male mysids. Females showed reduced ingestion rates when exposed to fluctuating temperatures around their thermal optimum, whereas ingestion of male mysids was not reduced when exposed to fluctuating temperatures. The observed sex-specific differences might be related to potentially higher lipid and energy demands of the females. We suggest future studies should investigate males and females to improve our understanding about impacts of environmental variability on natural populations.
Jensen’s inequality predicts that the response of any given system to average constant conditions is different from its average response to varying ones. Environmental fluctuations in abiotic conditions are pervasive on Earth; yet until recently, most ecological research has addressed the effects of multiple environmental drivers by assuming constant conditions. One could thus expect to find significant deviations in the magnitude of their effects on ecosystems when environmental fluctuations are considered. Drawing on experimental studies published during the last 30 years reporting more than 950 response ratios ( n = 5,700), we present a comprehensive analysis of the role that environmental fluctuations play across the tree of life. In contrast to the predominance of interactive effects of global-change drivers reported in the literature, our results show that their cumulative effects were additive (58%), synergistic (26%), and antagonistic (16%) when environmental fluctuations were present. However, the dominant type of interaction varied by trophic level (autotrophs: interactive; heterotrophs: additive) and phylogenetic group (additive in Animalia; additive and positive antagonism in Chromista; negative antagonism and synergism in Plantae). In addition, we identify the need to tackle how complex communities respond to fluctuating environments, widening the phylogenetic and biogeographic ranges considered, and to consider other drivers beyond warming and acidification as well as longer timescales. Environmental fluctuations must be taken into account in experimental and modeling studies as well as conservation plans to better predict the nature, magnitude, and direction of the impacts of global change on organisms and ecosystems.
The California Current Marine Ecosystem is a highly productive system that exhibits strong natural variability and vulnerability to anthropogenic climate trends. Relating projections of ocean change to biological sensitivities requires detailed synthesis of experimental results. Here, we combine measured biological sensitivities with high‐resolution climate projections of key variables (temperature, oxygen, and pCO2) to identify the direction, magnitude, and spatial distribution of organism‐scale vulnerabilities to multiple axes of projected ocean change. Among 12 selected species of cultural and economic importance, we find that all are sensitive to projected changes in ocean conditions through responses that affect individual performance or population processes. Response indices were largest in the northern region and inner shelf. While performance traits generally increased with projected changes, fitness traits generally decreased, indicating that concurrent stresses can lead to fitness loss. For two species, combining sensitivities to temperature and oxygen changes through the Metabolic Index shows how aerobic habitat availability could be compressed under future conditions. Our results suggest substantial and specific ecological susceptibility in the next 80 years, including potential regional loss of canopy‐forming kelp, changes in nearshore food webs caused by declining rates of survival among red urchins, Dungeness crab, and razor clams, and loss of aerobic habitat for anchovy and pink shrimp. We also highlight fillable gaps in knowledge, including specific physiological responses to stressors, variation in responses across life stages, and responses to multistressor combinations. These findings strengthen the case for filling information gaps with experiments focused on fitness‐related responses and those that can be used to parameterize integrative physiological models, and suggest that the CCME is susceptible to substantial changes to ecosystem structure and function within this century. This work summarizes experimental results of biological responses to projected climate change in species of economic, cultural, and ecological importance along the US and Canadian west coast, and combines these with downscaled climate projections. While physiological rates generally increased with projected changes, fitness traits generally decreased, indicating that concurrent stresses can lead to fitness loss, and anticipated ecological change in the California Current Marine Ecosystem.
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This manuscript presents an inventory of the carbonate system from the main water masses comprising the marine current system on Brazil’s northeast coast (South Atlantic Ocean). For this purpose, four transects were conducted with an approximate length of 357 km (each one) through the platform and continental slope of the Sergipe–Alagoas sedimentary basin. Water samples were then collected in vertical profiles measuring from 5 to 1,799 meters depth, totaling 34 stations. Total alkalinity, calcium, and total boron were obtained analytically from these samples and by relationships with salinity. Speciation and concentration of the carbonate system were obtained by means of thermodynamic modeling. The results revealed that the empirical models used to calculate the concentrations of TA, calcium and total boron showed relevant variation when compared to the analytical values (TA: 5.0–6.5%; Ca: 0.4–4.8%; B T : 7.0–18.9%). However, the speciation and concentration of the carbonate system (CA, DIC, C O 3 2 − , CO 2(aq) , Ω Calc , and Ω Arag ) obtained from the empirical values of TA, calcium and total boron did not differ significantly from those obtained analytically (0.0–6.1%). On the other hand, the parameters of pH, H C O 3 ‐ , C O 3 ( aq ) 2 ‐ , CO 2(aq) , ρCO 2 , Ω Calc , and Ω Arag varied significantly within the different water masses (p < 0.05). This study supports and encourages acidification monitoring projects in the South Atlantic Ocean, based on modeling the carbonate system parameters generated in real-time.
Ocean and coastal acidification (OCA) present a unique set of sustainability challenges at the human-ecological interface, and the waters and communities of the Gulf of Maine are among the most vulnerable to this environmental threat. Successful adaptation and mitigation options to address myriad impacts of OCA– including actions by marine resource and water quality managers, the scientific community, and the aquaculture and fishing industry – depend strongly on the availability of monitoring that can inform decision-making and on developing and implementing best practices for resilience at the community level. Collaboration between technical experts, facilitators, and a locally engaged citizenry can help to ensure information and planning in response to OCA is relevant to stakeholder needs and that co-creative processes match best practices for social-ecological problem solving and active social learning; ultimately building public trust for adaptation measures considered. This dissertation shares extensive outreach, workshop-based training, and coordinated monitoring activities which collectively supported and assessed the regional capacity of science coalitions and stakeholders to engage with OCA monitoring and management. We show that crowdsourcing water measurements of the marine carbonate system is a viable strategy for expanding estuarine carbonate system monitoring and prioritizing regions for more targeted assessment. This work enabled a platform for dialogue about OCA among other interrelated environmental concerns and fostered a series of co-benefits relating to public participation in resource and risk management. The results demonstrate the value and readiness of diverse stakeholder audiences and community science programs in furthering monitoring capacity and political action for OCA.
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An investigation was conducted to determine the effects of elevated pCO2 on the net production and calcification of an assemblage of corals maintained under near-natural conditions of temperature, light, nutrient, and flow. Experiments were performed in summer and winter to explore possible interactions between seasonal change in temperature and irradiance and the effect of elevated pCO2. Particular attention was paid to interactions between net production and calcification because these two processes are thought to compete for the same internal supply of dissolved inorganic carbon (DIC). A nutrient enrichment experiment was performed because it has been shown to induce a competitive interaction between photosynthesis and calcification that may serve as an analog to the effect of elevated pCO2. Net carbon production, NPC, increased with increased pCO2 at the rate of 3 ± 2% (μmol CO2aq kg−1)−1. Seasonal change of the slope NPC-[CO2aq] relationship was not significant. Calcification (G) was strongly related to the aragonite saturation state Ωa. Seasonal change of the G-Ωa relationship was not significant. The first-order saturation state model gave a good fit to the pooled summer and winter data: G = (8 ± 1 mmol CaCO3 m−2 h−1)(Ωa − 1), r2 = 0.87, P = 0.0001. Both nutrient and CO2 enrichment resulted in an increase in NPC and a decrease in G, giving support to the hypothesis that the cellular mechanism underlying the decrease in calcification in response to increased pCO2 could be competition between photosynthesis and calcification for a limited supply of DIC.
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CO2-enriched seawater was far more toxic to eggs and larvae of a marine fish, silver seabream, Pagrus major, than HCl-acidified seawater when tested at the same seawater pH. Data on the effects of acidified seawater can therefore not be used to estimate the toxicity of CO2, as has been done in earlier studies. Ontogenetic changes in CO2 tolerance of two marine bony fishes (Pag. major and Japanese sillago, Sillago japonica) showed a similar, characteristic pattern: the cleavage and juvenile stages were most susceptible, whereas the preflexion and flexion stages were much more tolerant to CO2. Adult Japanese amberjack, Seriola quinqueradiata, and bastard halibut, Paralichthys olivaceus, died within 8 and 48 h, respectively, during exposure to seawater equilibrated with 5% CO2. Only 20% of a cartilaginous fish, starspotted smooth-hound, Mustelus manazo, died at 7% CO2 within 72 h. Arterial pH initially decreased but completely recovered within 1-24 h for Ser. quinqueradiata and Par. olivaceus at 1 and 3% CO2, but the recovery was slower and complete only at 1% for M. manazo. During exposure to 5% CO2, Par. olivaceus died after arterial pH had been completely restored. Exposure to 5% CO2 rapidly depressed the cardiac output of Ser. quinqueradiata, while 1% CO2 had no effect. Both levels of ambient CO2 had no effect on blood O2 levels. We tentatively conclude that cardiac failure is important in the mechanisms by which CO2 kills fish. High CO2 levels near injection points during CO2 ocean sequestration are likely to have acute deleterious effects on both larvae and adults of marine fishes.
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Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms—such as corals and some plankton—will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean–carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.
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Primary production and calcification in response to different partial pressures of CO2 (PCO2) (``glacial,'' ``present,'' and ``year 2100'' atmospheric CO2 concentrations) were investigated during a mesocosm bloom dominated by the coccolithophorid Emiliania huxleyi. The day-to-day dynamics of net community production (NCP) and net community calcification (NCC) were assessed during the bloom development and decline by monitoring dissolved inorganic carbon (DIC) and total alkalinity (TA), together with oxygen production and 14C incorporation. When comparing year 2100 with glacial PCO2 conditions we observed: (1) no conspicuous change of net community productivity (NCPy); (2) a delay in the onset of calcification by 24 to 48 hours, reducing the duration of the calcifying phase in the course of the bloom; (3) a 40% decrease of NCC; and (4) enhanced loss of organic carbon from the water column. These results suggest a shift in the ratio of organic carbon to calcium carbonate production and vertical flux with rising atmospheric PCO2.
In laboratory experiments with the coccolithophore species Emiliania huxleyi and Gephyrocapsa oceanica, the ratio of particulate inorganic carbon (PIC) to particulate organic carbon (POC) production decreased with increasing CO2 concentration ([CO2]). This was due to both reduced PIC and enhanced POC production at elevated [CO2]. Carbon dioxide concentrations covered a range from a preindustrial level to a value predicted for 2100 according to a “business as usual” anthropogenic CO2 emission scenario. The laboratory results were used to employ a model in which the immediate effect of a decrease in global marine calcification relative to POC production on the potential capacity for oceanic CO2 uptake was simulated. Assuming that overall marine biogenic calcification shows a similar response as obtained for E. huxleyi or G. oceanica in the present study, the model reveals a negative feedback on increasing atmospheric CO2 concentrations owing to a decrease in the PIC/POC ratio.
We evaluate experimentally the effect of carbonate saturation state at the sediment-water interface (SWI) on survivorship of various size classes of the juvenile bivalve Mercenaria mercenaria. Populations of 0.2-mm, 0.3-mm, 1-mm, and 2-mm M. mercenaria were introduced to sediments realistically undersaturated (experimental, saturation state with respect to aragonite = Ω aragonite = IMP/K′sp = ∼0.3) and saturated (control, Ωaragonite = ∼1.5) with respect to aragonite in order to evaluate the impact of saturation state and dissolution on survivorship. Linear regression analysis was used to examine mortality within each treatment over time and show significant mortality for each size class in experimental-undersaturated treatments only (P < 0.05). Mortality rates in experimental-undersaturated sediments were -11.8, -4.8, -1.9, and -1.1% d -1 for the 0.2-, 0.3-, 1.0-, and 2.0-mm bivalves, respectively. Analysis of covariance (ANCOVA) was used to examine differences in mortality between treatments over time and show significantly different mortality rates for the 0.2-, 0.3-, and 1-mm individuals (P < 0.05). Dissolution may represent a previously unrecognized yet significant source of mortality for "just-set" juvenile bivalves, particularly the very small individuals that have been largely ignored in recruitment studies to date. Dissolution-induced mortality may help explain the exponential losses of juvenile bivalves following their transition from the pelagic larval phase to the benthic juvenile phase.