Water column organic carbon in a Pacific marginal sea (Strait of Georgia, Canada)

Johannessen, Sophia C.; Potentier, G.; Wright, Cynthia; Masson, Diane; Macdonald, Robie W.

doi:10.1016/j.marenvres.2008.07.008

Cited by 16 publications

(14 citation statements)

References 35 publications

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“…PON and biogenic Si detritus are estimated to be 0.2 of the microphytoplankton biomass and DON is 0.1 of PON. Semilabile DON is generally higher than PON in the SoG [ Johannessen et al ., ], however, model DON is not sensitive to the initialization value and exceeds model PON after 30 days. Since model pH and Ω A are not sensitive to initial carbon conditions after 30 days, IOS carbon profiles from the 11 September 2011 cast date are used to initialize DIC and TA.…”

Section: Methodsmentioning

confidence: 99%

Locally driven interannual variability of near‐surface pH and Ω_A in the Strait of Georgia

2016

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Declines in mean ocean pH and aragonite saturation state (ΩA) driven by anthropogenic CO2 emissions have raised concerns regarding the trends of pH and ΩA in estuaries. Low pH and ΩA can be harmful to a variety of marine organisms, especially those with calcium carbonate shells, and so may threaten the productive ecosystems and commercial fisheries found in many estuarine environments. The Strait of Georgia is a large, temperate, productive estuarine system with numerous wild and aquaculture shellfish and finfish populations. We determine the seasonality and variability of near‐surface pH and ΩA in the Strait using a one‐dimensional, biophysical, mixing layer model. We further evaluate the sensitivity of these quantities to local wind, freshwater, and cloud forcing by running the model over a wide range of scenarios using 12 years of observations. Near‐surface pH and ΩA demonstrate strong seasonal cycles characterized by low pH, aragonite‐undersaturated waters in winter and high pH, aragonite‐supersaturated waters in summer. The aragonite saturation horizon generally lies at ∼20 m depth except in winter and during strong Fraser River freshets when it shoals to the surface. Periods of strong interannual variability in pH and aragonite saturation horizon depth arise in spring and summer. We determine that at different times of year, each of wind speed, freshwater flux, and cloud fraction are the dominant drivers of this variability. These results establish the mechanisms behind the emerging observations of highly variable near‐surface carbonate chemistry in the Strait.

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Section: Methodsmentioning

confidence: 99%

Locally driven interannual variability of near‐surface pH and Ω_A in the Strait of Georgia

2016

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“…In addition, although the tryptophan-like component C6, represents a minor proportion of total fluorescence, even a small proteinaceous fraction of the overall DOM pool can play a major role in overall bioavailability and bacterial utilization of DOM (Berggren et al, 2010;Guillamette and Giorgio, 2011). These contributions of stream-exported DOM may represent a relatively fresh, seasonally consistent contribution of terrestrial subsidy from streams to the coastal ecosystem, which in this region is relatively lower in carbon and nutrients throughout much of the year (Whitney et al, 2005;Johannessen et al, 2008).…”

Section: Doc Export From Small Catchments To the Coastal Oceanmentioning

confidence: 99%

A global hotspot for dissolved organic carbon in hypermaritime watersheds of coastal British Columbia

et al. 2017

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Abstract. The perhumid region of the coastal temperate rainforest (CTR) of Pacific North America is one of the wettest places on Earth and contains numerous small catchments that discharge freshwater and high concentrations of dissolved organic carbon (DOC) directly to the coastal ocean. However, empirical data on the flux and composition of DOC exported from these watersheds are scarce. We established monitoring stations at the outlets of seven catchments on Calvert and Hecate islands, British Columbia, which represent the rain-dominated hypermaritime region of the perhumid CTR. Over several years, we measured stream discharge, stream water DOC concentration, and stream water dissolved organic-matter (DOM) composition. Discharge and DOC concentrations were used to calculate DOC fluxes and yields, and DOM composition was characterized using absorbance and fluorescence spectroscopy with parallel factor analysis (PARAFAC). The areal estimate of annual DOC yield in water year 2015 was 33.3 Mg C km −2 yr −1 , with individual watersheds ranging from an average of 24.1 to 37.7 Mg C km −2 yr −1 . This represents some of the highest DOC yields to be measured at the coastal margin. We observed seasonality in the quantity and composition of exports, with the majority of DOC export occurring during the extended wet period (September-April). Stream flow from catchments reacted quickly to rain inputs, resulting in rapid export of relatively fresh, highly terrestrial-like DOM. DOC concentration and measures of DOM composition were related to stream discharge and stream temperature and correlated with watershed attributes, including the extent of lakes and wetlands, and the thickness of organic and mineral soil horizons. Our discovery of high DOC yields from these small catchments in the CTR is especially compelling as they deliver relatively fresh, highly terrestrial organic matter directly to the coastal ocean. Hypermaritime landscapes are common on the British Columbia coast, suggesting that this coastal margin may play an important role in the regional processing of carbon and in linking terrestrial carbon to marine ecosystems.

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“…Hofmann et al (2009) found that adding a biogeochemical model to a prescribed physical mixing scenario in the highly polluted Scheldt estuary decreased the low-salinity pH minimum due to strong remineralization of abundant anthropogenic organic carbon (Frankignoulle et al, 1996) and increased pH at higher salinity due to intense outgassing (Schiettecatte et al, 2006). In contrast the Fraser River estuary is biologically productive and 20 deep (model site is deeper than 300 m) and much of the organic matter produced locally sinks and is remineralized well below the surface layer (Johannessen et al, 2008) resulting in increased estuarine pH across the salinity range during summer (Ianson et al, 2016) compared with the two-endmember mixing model. Still, this simplified case reproduces the overall estuarine pH sensitivity that we observe in the coupled model.…”

Section: Two-endmember Conservative Mixingmentioning

confidence: 99%

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

Moore-Maley¹,

Ianson²,

Allen³

2017

Preprint

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Abstract.Ocean acidification threatens to reduce pH and aragonite saturation state (Ω A ) in estuaries, potentially damaging their ecosystems. However, the impact of highly variable river total alkalinity (TA) and dissolved inorganic carbon (DIC) on pHand Ω A in these estuaries is unknown. We assess the sensitivity of estuarine surface pH and Ω A to river chemistry using a 1-dimensional, biogeochemical-coupled model of the Strait of Georgia on the Canadian Pacific coast and generalize the results 5 in the context of global rivers. The productive Strait of Georgia estuary has a large, seasonally variable freshwater input from the glacially fed, undammed Fraser River. Analyzing TA and pH observations from this river and its estuary, we find that the Fraser is moderately alkaline (TA 500-1350 µmol kg −1 ) but relatively DIC-rich, especially during winter (low flow). Model results show that estuarine pH and Ω A , while sensitive to freshwater DIC and TA, do not vary in synchrony. Instead, rivers with high DIC and TA produce lower estuarine pH due to an increased estuarine DIC:TA ratio, but higher estuarine Ω A because of 10 DIC contributions to the carbonate ion. This estuarine pH sensitivity decreases with increasing mean river TA, but the zone of maximum pH sensitivity also moves to higher salinity which could impact a larger areal extent of the estuary. Many temperate rivers, such as the Fraser, are expected to experience weaker freshets and stronger winter flows under climate change, reducing the extent of the river plume and the impact of river chemistry in much of the estuary. However, increasing carbon in rivers will move the highest sensitivity zone to higher salinities that cover larger areas under present-day flow regimes.

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Water column organic carbon in a Pacific marginal sea (Strait of Georgia, Canada)

Abstract: International audienc

Cited by 16 publications

References 35 publications

Locally driven interannual variability of near‐surface pH and Ω_A in the Strait of Georgia

Locally driven interannual variability of near‐surface pH and Ω_A in the Strait of Georgia

A global hotspot for dissolved organic carbon in hypermaritime watersheds of coastal British Columbia

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

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Water column organic carbon in a Pacific marginal sea (Strait of Georgia, Canada)

Abstract: International audienc

Cited by 16 publications

References 35 publications

Locally driven interannual variability of near‐surface pH and ΩA in the Strait of Georgia

Locally driven interannual variability of near‐surface pH and ΩA in the Strait of Georgia

A global hotspot for dissolved organic carbon in hypermaritime watersheds of coastal British Columbia

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

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Product

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Locally driven interannual variability of near‐surface pH and Ω_A in the Strait of Georgia

Locally driven interannual variability of near‐surface pH and Ω_A in the Strait of Georgia