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1.
In this paper, we present the results of the first automated continuous multi-year high temporal frequency study of CO2 dynamics in a coastal coral reef ecosystem. The data cover 2.5?years of nearly continuous operation of the CRIMP-CO2 buoy spanning particularly wet and dry seasons in southern Kaneohe Bay, a semi-enclosed tropical coral reef ecosystem in Hawaii. We interpret our observational results in the context of how rapidly changing physical and biogeochemical conditions affect the pCO2 of surface waters and the magnitude and direction of air–sea exchange of CO2. Local climatic forcing strongly affects the biogeochemistry, water column properties, and gas exchange between the ocean and atmosphere in Kaneohe Bay. Rainfall driven by trade winds and other localized storms generates pulses of nutrient-rich water, which exert a strong control on primary productivity and impact carbon cycling in the water column of the bay. The “La Ni?a” winter of 2005–2006 was one of the wettest winters in Hawaii in 30?years and contrasted sharply with preceding and subsequent drier winter seasons. In addition, short-term variability in physical forcing adds complexity and helps drive the response of the CO2–carbonic acid system of the bay. Freshwater pulses to Kaneohe Bay provide nutrient subsidies to bay waters, relieving the normal nitrogen limitation of this system and driving phytoplankton productivity. Seawater pCO2 responds to the blooms as well as to physical forcing mechanisms, leading to a relatively wide range of pCO2 in seawater from about 250 to 650?μatm, depending on conditions. Large drawdowns in pCO2 following storms occasionally cause bay waters to switch from being a source of CO2 to the atmosphere to being a sink. Yet, during our study period, the southern sector of Kaneohe Bay remained a net source of CO2 to the atmosphere on an annualized basis. The integrated net annual flux of CO2 from the bay to the atmosphere varied between years by a factor of more than two and was lower during the wet “La Ni?a” year, than during the following year. Over the study period, the net annualized flux was 1.80?mol?C?m?2?year?1. Our CO2 flux estimates are consistent with prior synoptic work in Kaneohe Bay and with estimates in other tropical coral reef ecosystems studied to date. The high degree of climatological, physical, and biogeochemical variability observed in this study suggests that automated high-frequency observations are needed to capture the short-, intermediate-, and long-term variability of CO2 and other properties of these highly dynamic coastal coral reef ecosystems.  相似文献   

2.
Storm runoff in the steep watersheds in Hawaii leads to sediment and freshwater pulses to coastal waters that quickly affect nearshore water quality. This is particularly true in semi-enclosed embayments, such as Kaneohe Bay, Oahu, where water has a relatively long residence time compared to more open coastal areas of the islands. In this paper the authors discuss water quality and productivity in Kaneohe Bay after back-to-back rain events in late November and early December 2003, following a particularly dry summer. The short-term biogeochemical response of coastal waters and the ecosystem to runoff and physical forcing was evaluated through a combination of continuous in situ measurements and adaptive synoptic sampling carried out on a variety of temporal and spatial scales.  相似文献   

3.
An array of MAPCO2 buoys, CRIMP-2, Ala Wai, and Kilo Nalu, deployed in the coastal waters of Hawaii, have produced multi-year high temporal resolution CO2 records in three different coral reef environments off the island of Oahu, Hawaii. This study, which includes data from June 2008 to December 2011, is part of an integrated effort to understand the factors that influence the dynamics of CO2–carbonic acid system parameters in waters surrounding Pacific high-island coral reef ecosystems and subject to differing natural and anthropogenic stresses. The MAPCO2 buoys are located on the Kaneohe Bay backreef, and fringing reef sites on the south shore of Oahu, Hawaii. The buoys measure CO2 and O2 in seawater and in the atmosphere at 3-h intervals, as well as other physical and biogeochemical parameters (conductivity, temperature, depth, chlorophyll-a, and turbidity). The buoy records, combined with data from synoptic spatial sampling, have allowed us to examine the interplay between biological cycles of productivity/respiration and calcification/dissolution and biogeochemical and physical forcings on hourly to inter-annual time scales. Air–sea CO2 gas exchange was also calculated to determine whether the locations were sources or sinks of CO2 over seasonal, annual, and interannual time periods. Net annualized fluxes for CRIMP-2, Ala Wai, and Kilo Nalu over the entire study period were 1.15, 0.045, and ?0.0056 mol C m?2 year?1, respectively, where positive values indicate a source or a CO2 flux from the water to the atmosphere, and negative values indicate a sink or flux of CO2 from the atmosphere into the water. These values are of similar magnitude to previous estimates in Kaneohe Bay as well as those reported from other tropical reef environments. Total alkalinity (AT) was measured in conjunction with pCO2, and the carbonic acid system was calculated to compare with other reef systems and open ocean values around Hawaii. These findings emphasize the need for high-resolution data of multiple parameters when attempting to characterize the carbonic acid system in locations of highly variable physical, chemical, and biological parameters (e.g., coastal systems and reefs).  相似文献   

4.
The distributions of the partial pressure of carbon dioxide (pCO2) and total alkalinity (TA) were examined for a 6-month period in the Wailuku and Wailoa rivers and coastal waters of Hilo Bay on the west coast of the Island of Hawaii, USA. Main results for the largest and turbulent Wailuku River show in the watershed an oversaturation in CO2 with respect to atmospheric equilibrium and a CO2 undersaturation in the estuary. In the Wailoa river-estuary system, extremely high pCO2 values ranging from 1500 to 10500 ppm were measured with significant shifts in pCO2 from drought to flood period. In the two rivers, water residence time, groundwater inputs and occasional flood events are the predominant drivers of the spatial and temporal patterns in the distribution of pCO2. In Hilo Bay, CO2 oversaturation dominates and the bay was a source of CO2 to the atmosphere during the study period. TA is conservative along the salinity gradient, indicating calcification in the bay is not a significant source of CO2 to the atmosphere.  相似文献   

5.
Fluvial effects on nutrient and phytoplankton dynamics were evaluated in southern Kaneohe Bay, Oahu, Hawaii. Fluvial inputs occurred as small, steady baseflows interrupted by intense pulses of storm runoff. Baseflow river inputs only affected restricted areas around stream mouths, but the five storm events sampled during this study produced transient runoff plumes of much greater spatial extent. Nutrient loading via runoff generally led to an increase of the phytoplankton biomass and gross primary productivity in southern Kaneohe Bay, but the rapid depletion of nutrients resulted in a decline of the algal populations in the relatively short time of days. Under baseline conditions, water column primary productivity in southern Kaneohe Bay is normally nitrogen limited. Following storm events, the high ratio of dissolved inorganic nitrogen to dissolved inorganic phosphorus (DIN:DIP, 25–29) fluxes of runoff nutrients drove bay waters towards phosphorus limitation. A depletion of phosphate relative to DIN in surface waters was observed following all storm events. Due to high flushing rates, recovery times of bay waters from storm perturbations ranged from 3 to 8 d and appeared to be correlated with tidal range. Storm inputs have a significant effect on the water column ecosystem and biogeochemistry in southern Kaneohe Bay. The perturbations were only transient events and the system rapidly recovered to prestorm conditions.  相似文献   

6.
Annually integrated air-water CO2 flux data in 44 coastal environments were compiled from literature. Data were gathered in 8 major ecosystems (inner estuaries, outer estuaries, whole estuarine systems, mangroves, salt marshes, coral reefs, upwelling systems, and open continental shelves), and up-scaled in the first attempt to integrate air-water CO2 fluxes over the coastal ocean (26×106 km2), taking into account its geographical and ecological diversity. Air-water CO2 fluxes were then up-scaled in global ocean (362×106 km2) using the present estimates for the coastal ocean and those from Takahashi et al. (2002) for the open ocean (336×106 km2). If estuaries and salt marshes are not taken into consideration in the up-scaling, the coastal ocean behaves as a sink for atmospheric CO2(−1.17 mol C m−2 yr−1) and the uptake of atmospheric CO2 by the global ocean increases by 24% (−1.93 versus −1.56 Pg C yr−1). The inclusion of the coastal ocean increases the estimates of CO2 uptake by the global ocean by 57% for high latitude areas (−0.44 versus −0.28 Pg C yr−1) and by 15% for temperate latitude areas (−2.36 versus −2.06 Pg C yr−1) At subtropical and tropical latitudes, the contribution from the coastal ocean increases the CO2 emission to the atmosphere from the global oceam by 13% (0.87 versus 0.77 Pg C yr−1). If estuaries and salt marshes are taken into consideration in the upscaling, the coastal ocean behaves as a source for atmospheric CO2 (0.38 mol C m−2 yr−1) and the uptake of atmospheric CO2 from the global ocean decreases by 12% (−1.44 versus −1.56 Pg C yr−1) At high and subtropical and tropical latitudes, the coastal ocean behaves as a source for atmospheric CO2 but at temperate latitudes, it still behaves as a moderate CO2 sink. A rigorous up-scaling of air-water CO2 fluxes in the coastal ocean is hampered by the poorly constrained estimate of the surface area of inner estuaries. The present estimates clearly indicate the significance of this biogeochemically, highly active region of the biosphere in the global CO2 cycle.  相似文献   

7.
Ocean acidification due to anthropogenic CO2 emissions is a dominant driver of long-term changes in pH in the open ocean, raising concern for the future of calcifying organisms, many of which are present in coastal habitats. However, changes in pH in coastal ecosystems result from a multitude of drivers, including impacts from watershed processes, nutrient inputs, and changes in ecosystem structure and metabolism. Interaction between ocean acidification due to anthropogenic CO2 emissions and the dynamic regional to local drivers of coastal ecosystems have resulted in complex regulation of pH in coastal waters. Changes in the watershed can, for example, lead to changes in alkalinity and CO2 fluxes that, together with metabolic processes and oceanic dynamics, yield high-magnitude decadal changes of up to 0.5 units in coastal pH. Metabolism results in strong diel to seasonal fluctuations in pH, with characteristic ranges of 0.3 pH units, with metabolically intense habitats exceeding this range on a daily basis. The intense variability and multiple, complex controls on pH implies that the concept of ocean acidification due to anthropogenic CO2 emissions cannot be transposed to coastal ecosystems directly. Furthermore, in coastal ecosystems, the detection of trends towards acidification is not trivial and the attribution of these changes to anthropogenic CO2 emissions is even more problematic. Coastal ecosystems may show acidification or basification, depending on the balance between the invasion of coastal waters by anthropogenic CO2, watershed export of alkalinity, organic matter and CO2, and changes in the balance between primary production, respiration and calcification rates in response to changes in nutrient inputs and losses of ecosystem components. Hence, we contend that ocean acidification from anthropogenic CO2 is largely an open-ocean syndrome and that a concept of anthropogenic impacts on marine pH, which is applicable across the entire ocean, from coastal to open-ocean environments, provides a superior framework to consider the multiple components of the anthropogenic perturbation of marine pH trajectories. The concept of anthropogenic impacts on seawater pH acknowledges that a regional focus is necessary to predict future trajectories in the pH of coastal waters and points at opportunities to manage these trajectories locally to conserve coastal organisms vulnerable to ocean acidification.  相似文献   

8.
While the physical forcing mechanisms that govern the outflows of major rivers throughout the world are well documented in the literature, comparably less research has been done to examine the mechanisms that govern the contributions of small rivers and streams to coastal ocean systems. These rivers and streams provide a direct means for the transport of anthropogenic and terrigenous materials from watersheds to coastal oceans. This study describes the temporal and spatial variability of freshwater plumes from Kaneohe Stream, Hawaii, USA, after storm events in the Kaneohe Bay watershed. Freshwater plumes were examined using a combination of fixed moorings, synoptic shipboard surveys, and lagrangian surface drifters. Data sets were collected over the course of 19 months from August 2005 to March 2007 with particular attention paid to storms during the boreal winters. Stream discharge and duration were found to exert a primary control on plume persistence in the southern Kaneohe Bay system. Time series data show a strong coherence between wind forcing and surface currents, which, in combination with data derived from shipboard and aerial surveys, indicate that the spatial variability of freshwater plumes is primarily determined by atmospheric forcing.  相似文献   

9.
The global coastal zone is characterized by high biological productivity and serves as an important channel through which materials are transferred from land to the open ocean, yet little is known how it will be affected by climate change. Here, we use Kaneohe Bay, Hawaii, a semi-enclosed subtropical embayment partially surrounded by a mountainous watershed and fed by river runoff as an example to explore the potential impact of climate change on the pelagic and benthic cycling of nitrogen. We employ a nine-compartment nitrogen cycle biogeochemical box model and perturb it with a set of four idealized climate scenarios. We find that hydrological changes play a dominant role in determining the ecosystem structure, while temperature changes are more important for the trophic state and stability of the ecosystem. The ecosystem stability against storm events does not significantly change under any scenario. The system remains autotrophic in the future; however, it becomes significantly less autotrophic under drier climate, while it turns slightly more autotrophic under wetter climate. These findings may have implications for other high island watershed and coastal ecosystems in the tropics and subtropics.  相似文献   

10.
The partial pressure of CO2 (pCO2) and concentration of dissolved CH4 in surface waters have been studied in three coastal systems connected to Cadiz Bay (southwestern coast of Spain) over different time scales. The concentration of CH4 varied from 1 to 4200 nmol kg?1 (192.1 ± 463.6 nmol kg?1) and the saturation percent from 19 to 159,577% (6645 ± 16,921%), and pCO2 from 315 to 3240 μatm (841.9 ± 466.3 μatm), with saturation percent values varying between 72 and 981% (220 ± 133%). The seasonal variation of pCO2 mainly depends on the temperature. On the contrary, the annual distribution of dissolved CH4 is associated with the precipitation regime. In addition, pCO2 and dissolved CH4 showed spatial variation. pCO2 increased toward the inner part of the systems, with the proximity to the discharge points from human activities. Dissolved CH4 is influenced by both anthropogenic inputs and natural processes such as benthic supply and exchange with the adjacent salt marshes. pCO2 and dissolved CH4 also varied with the tides: The highest concentrations were measured during the ebb, which suggests that the systems export CO2 and CH4 to the Bay and adjacent Atlantic Ocean.  相似文献   

11.
Mangrove ecosystems play an important, but understudied, role in the cycling of carbon in tropical and subtropical coastal ocean environments. In the present study, we examined the diel dynamics of seawater carbon dioxide (CO2) and dissolved oxygen (DO) for a mangrove-dominated marine ecosystem (Mangrove Bay) and an adjacent intracoastal waterway (Ferry Reach) on the island of Bermuda. Spatial and temporal trends in seawater carbonate chemistry and associated variables were assessed from direct measurements of dissolved inorganic carbon, total alkalinity, dissolved oxygen (DO), temperature, and salinity. Diel pCO2 variability was interpolated across hourly wind speed measurements to determine variability in daily CO2 fluxes for the month of October 2007 in Bermuda. From these observations, we estimated rates of net sea to air CO2 exchange for these two coastal ecosystems at 59.8 ± 17.3 in Mangrove Bay and 5.5 ± 1.3 mmol m−2 d−1 in Ferry Reach. These results highlight the potential for large differences in carbonate system functioning and sea-air CO2 flux in adjacent coastal environments. In addition, observation of large diel variability in CO2 system parameters (e.g., mean pCO2: 390–2,841 μatm; mean pHT: 8.05–7.34) underscores the need for careful consideration of diel cycles in long-term sampling regimes and flux estimates.  相似文献   

12.
Understanding of the role of oceanic input in nutrient loadings is important for understanding nutrient and phytoplankton dynamics in estuaries adjacent to coastal upwelling regions as well as determining the natural background conditions. We examined the nitrogen sources to Yaquina Estuary (Oregon, USA) as well as the relationships between physical forcing and gross oceanic input of nutrients and phytoplankton. The ocean is the dominant source of dissolved inorganic nitrogen (DIN) and phosphate to the lower portion of Yaquina Bay during the dry season (May through October). During this time interval, high levels of dissolved inorganic nitrogen (primarily in the form of nitrate) and phosphate entering the estuary lag upwelling favorable winds by 2 days. The nitrate and phosphate levels entering the bay associated with coastal upwelling are correlated with the wind stress integrated over times scales of 4–6 days. In addition, there is a significant import of chlorophyll a to the bay from the coastal ocean region, particularly during July and August. Variations in flood-tide chlorophyll a lag upwelling favorable winds by 6 days, suggesting that it takes this amount of time for phytoplankton to utilize the recently upwelled nitrogen and be transported across the shelf into the estuary. Variations in water properties determined by ocean conditions propagate approximately 11–13 km into the estuary. Comparison of nitrogen sources to Yaquina Bay shows that the ocean is the dominant source during the dry season (May to October) and the river is the dominant source during the wet season with watershed nitrogen inputs primarily associated with nitrogen fixation on forest lands.  相似文献   

13.
Six synoptic samplings of nutrient concentrations of the water column and point-source inputs (rivers, sewage treatment plants) were conducted in the Seekonk-Providence River region of Narragansett Bay. Concentrations of nutrients (NH4 +, NO2 ?+NO3 ?, PO4 ?3, dissolved silicon, particulate N, particulate C) were predicted using a conservative, two-layer box model in order to assess the relative influence of external inputs and internal processes on observed concentrations. Although most nutrients were clearly affected by processes internal to the system, external input and mixing explained most of the variability in and absolute magnitude of observed concentrations, especially for dissolved constituents. In the bay as a whole, two functionally distinct regions can now be identified: the Seekonk-Providence River, where dissolved nutrient concentrations are externally controlled and lower Narragansett Bay where internal processes regulate the behavior of nutrients. A preliminary nitrogen budget suggests that the Seekonk-Providence River exports some 95% of the nitrogen entering the system via point sources and bottom water from upper Narragansett Bay.  相似文献   

14.
Epochs of changing atmospheric CO2 and seawater CO2–carbonic acid system chemistry and acidification have occurred during the Phanerozoic at various time scales. On the longer geologic time scale, as sea level rose and fell and continental free board decreased and increased, respectively, the riverine fluxes of Ca, Mg, DIC, and total alkalinity to the coastal ocean varied and helped regulate the C chemistry of seawater, but nevertheless there were major epochs of ocean acidification (OA). On the shorter glacial–interglacial time scale from the Last Glacial Maximum (LGM) to late preindustrial time, riverine fluxes of DIC, total alkalinity, and N and P nutrients increased and along with rising sea level, atmospheric PCO2 and temperature led, among other changes, to a slightly deceasing pH of coastal and open ocean waters, and to increasing net ecosystem calcification and decreasing net heterotrophy in coastal ocean waters. From late preindustrial time to the present and projected into the 21st century, human activities, such as fossil fuel and land-use emissions of CO2 to the atmosphere, increasing application of N and P nutrient subsidies and combustion N to the landscape, and sewage discharges of C, N, P have led, and will continue to lead, to significant modifications of coastal ocean waters. The changes include a rapid decline in pH and carbonate saturation state (modern problem of ocean acidification), a shift toward dissolution of carbonate substrates exceeding production, potentially leading to the “demise” of the coral reefs, reversal of the direction of the sea-to-air flux of CO2 and enhanced biological production and burial of organic C, a small sink of anthropogenic CO2, accompanied by a continuous trend toward increasing autotrophy in coastal waters.  相似文献   

15.
The Service d’Observation de la Rade de Villefranche-sur-Mer is designed to study the temporal variability of hydrological conditions as well as the abundance and composition of holo- and meroplankton at a fixed station in this bay of the northwest Mediterranean. The weekly data collected at this site, designated as “Point B” since 1957, represent a long-term time series of hydrological conditions in a coastal environment. Since 2007, the historical measurements of hydrological and biological conditions have been complemented by measurements of the CO2–carbonic acid system parameters. In this contribution, CO2–carbonic acid system parameters and ancillary data are presented for the period 2007–2011. The data are evaluated in the context of the physical and biogeochemical processes that contribute to variations in CO2 in the water column and exchange of this gas between the ocean and atmosphere. Seasonal cycles of the partial pressure of CO2 in seawater (pCO2) are controlled principally by variations in temperature, showing maxima in the summer and minima during the winter. Normalization of pCO2 to the mean seawater temperature (18.5 °C), however, reveals an apparent reversal of the seasonal cycle with maxima observed in the winter and minima in the summer, consistent with a biogeochemical control of pCO2 by primary production. Calculations of fluxes of CO2 show this area to be a weak source of CO2 to the atmosphere during the summer and a weak sink during the winter but near neutral overall (range ?0.3 to +0.3 mmol CO2 m?2 h?1, average 0.02 mmol CO2 m?2 h?1). We also provide an assessment of errors incurred from the estimation of annual fluxes of CO2 as a function of sampling frequency (3-hourly, daily, weekly), using data obtained at the Hawaii Kilo Nalu coastal time-series station, which shows similar behavior to the Point B location despite significant differences in climate and hydrological conditions and the proximity of a coral reef ecosystem.  相似文献   

16.
Measurements of CO2 to air ratios in the gas trapped in bubbles in ice of glacial age suggest that the CO2 content of the atmosphere was considerably lower during peak glacial time than during Holocene time. The purpose of this paper is to show that such a change must in all likelihood be the result of alterations in the nutrient element chemistry of sea water. Two possible scenarios are presented. One involves alternate storage and erosion of phosphorous leaving residues from shelf sediments. The other involves changes in the CP ratio in the organic debris falling to the deep sea. Means of verifying the nutrient cycle hypothesis are also given. It is shown that the 13C record as we know it in planktonic and benthic foraminifera, the oxygen record as inferred from benthic foraminifera species distributions, and the early post glacial CaCo3 preservation event as recorded by aragonitic pteropods are consistent with both of the hypotheses presented. Only if an early post glacial spike in the 13C record for planktonic shells could be found would it be possible to eliminate one of these hypotheses (i.e., that involving shelf storage). The implications of these nutrient hypotheses to climate theory are as follows. If shelf storage is responsible for the glacial to interglacial CO2 increase, then the CO2 change must be considered an amplifier of some primary cause. The reason is that sea level changes are needed to drive deposition on (and erosion from) the shelves. On the other hand, if changes in the CP ratio for falling debris are responsible, then the CO2 change could either be an amplifier or a primary cause for the major glacial to interglacial climatic cycle. The latter is possible as self-sustained oscillations in ocean chemistry might be driven by interactions between ocean ecology and ocean nutrient chemistry.  相似文献   

17.
Repeated surveys of the Kennebec estuary, a macrotidal river estuary in Maine, USA, between 2004 and 2008 found spatial and temporal variability both in sources of carbon dioxide (CO2) to the estuary and the air–sea flux of estuary CO2. On an annual basis, the surveyed area of the Kennebec estuary had an area-weighted average partial pressure of CO2 (pCO2) of 559 μatm. The area-weighted average CO2 flux to the atmosphere was 3.54 mol C m?2 year?1. Overall, the Kennebec estuary was an annual source of 7.2?×?107 mol CO2 to the atmosphere. Distinct seasonality in estuarine pCO2 was observed, with shifts in the seasonal pattern evident between lower and higher salinities. Fluxes of CO2 from the estuary were elevated following two summertime storms, and inputs of riverine CO2 outweighed internal estuarine CO2 inputs in nearly all months. River and estuarine inputs of CO2 represented 68 and 32 % of the total CO2 contributions to the estuary, respectively. This study examines the variability of CO2 in a large New England estuary, and highlights the comparatively high contribution of CO2 from riverine sources.  相似文献   

18.
Using coupled terrestrial and coastal zone models, we investigated the impacts of deglaciation and anthropogenic inputs on the CO2–H2O–CaCO3 system in global coastal ocean waters from the Last Glacial Maximum (LGM: 18,000 year BP) to the year 2100. With rising sea level and atmospheric CO2, the carbonate system of coastal ocean water changed significantly. We find that 6 × 1012 metric tons of carbon were emitted from the coastal ocean, growing due to the sea level rise, from the LGM to late preindustrial time (1700 AD) because of net heterotrophy and calcification processes. This carbon came to reside in the atmosphere and in the growing vegetation on land and in uptake of atmospheric CO2 through the weathering of rocks on land. It appears that carbonate accumulation, mainly, but not exclusively, in coral reefs from the LGM to late preindustrial time could account for about 24 ppmv of the 100 ppmv rise in atmospheric CO2, lending some support to the “coral reef hypothesis”. In addition, the global coastal ocean is now, or soon will be, a sink of atmospheric CO2. The temperature rise of 4–5°C since the LGM led to increased weathering rates of inorganic and organic materials on land and enhanced riverine fluxes of total C, N, and P to the coastal ocean of 68%, 108%, and 97%, respectively, from the LGM to late preindustrial time. During the Anthropocene, these trends have been exacerbated owing to rising atmospheric CO2, due to fossil fuel combustion and land-use practices, other human activities, and rising global temperatures. River fluxes of total reactive C, N, and P are projected to increase from late preindustrial time to the year 2100 by 150%, 380%, and 257%, respectively, modifying significantly the behavior of these element cycles in the coastal ocean, particularly in proximal environments. Despite the fact that the global shoal water carbonate mass has grown extensively since the LGM, the pHT (pH values on the total proton scale) of global coastal waters has decreased from ~8.35 to ~8.18 and the carbonate ion concentration declined by ~19% from the LGM to late preindustrial time. The latter represents a rate of decline of about 0.028 μmol CO3 2? per decade. In comparison, the decrease in coastal water pHT from the year 1900 to 2000 was about 8.18–8.08 and is projected to decrease further from about 8.08 to 7.85 between 2000 and 2100, according to the IS92a business-as-usual scenario of CO2 emissions. Over these 200 years, the carbonate ion concentration will fall by ~120 μmol kg?1 or 6 μmol kg?1 per decade. This decadal rate of decline of the carbonate ion concentration in the Anthropocene is 214 times the average rate of decline for the entire Holocene. Hence, when viewed against the millennial to several millennial timescale of geologic change in the coastal ocean marine carbon system, one can easily appreciate why ocean acidification is the “other CO2 problem”.  相似文献   

19.
While inputs from land are recognized as important resources supporting production in estuaries, the role that storm events play in resource delivery and the response of estuarine systems to pulsed inputs are less well appreciated. Temporal variations in (1) watershed export via the Mission and Aransas rivers and (2) nutrient and organic matter dynamics in Copano Bay were examined in the Mission?CAransas National Estuarine Research Reserve, south Texas. Inorganic nutrient, dissolved organic matter (DOM), and particulate organic matter (POM) concentrations in the rivers varied substantially with discharge, as did carbon and nitrogen stable isotope ratios of POM. Accounting for these variations was critical for calculating robust watershed export estimates. In Copano Bay, soluble reactive phosphorus, POM, and DOM remained elevated for several months following major runoff events, whereas inorganic nitrogen was rapidly depleted. Chlorophyll-a concentrations and POC-??13C in Copano Bay showed that increased POM concentrations were linked to enhanced in situ production.  相似文献   

20.
Groundwater may be highly enriched in dissolved carbon species, but its role as a source of carbon to coastal waters is still poorly constrained. Exports of deep and shallow groundwater-derived dissolved carbon species from a small subtropical estuary (Korogoro Creek, Australia, latitude ?31.0478°, longitude 153.0649°) were quantified using a radium isotope mass balance model (233Ra and 224Ra, natural groundwater tracers) under two hydrological conditions. In addition, air-water exchange of carbon dioxide and methane in the estuary was estimated. The highest carbon inputs to the estuary were from deep fresh groundwater in the wet season. Most of the dissolved carbon delivered by groundwater and exported from the estuary to the coastal ocean was in the form of dissolved inorganic carbon (DIC; 687 mmol m?2 estuary day?1; 20 mmol m?2 catchment day?1, respectively), with a large export of alkalinity (23 mmol m?2 catchment day?1). Average water to air flux of CO2 (869 mmol m?2 day?1) and CH4 (26 mmol m?2 day?1) were 5- and 43-fold higher, respectively, than the average global evasion in estuaries due to the large input of CO2- and CH4-enriched groundwater. The groundwater discharge contribution to carbon exports from the estuary for DIC, dissolved organic carbon (DOC), alkalinity, CO2, and CH4 was 22, 41, 3, 75, and 100 %, respectively. The results show that CO2 and CH4 evasion rates from small subtropical estuaries surrounded by wetlands can be extremely high and that groundwater discharge had a major role in carbon export and evasion from the estuary and therefore should be accounted for in coastal carbon budgets.  相似文献   

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