Posts Tagged 'North Pacific'

Marine CO2 patterns in the northern Salish Sea

Marine carbon dioxide (CO2) system data has been collected from December 2014 to June 2018 in the Northern Salish Sea (NSS; British Columbia, Canada) and consisted of continuous measurements at two sites as well as spatially- and seasonally distributed discrete seawater samples. The array of CO2 observing activities included high-resolution CO2 partial pressure (pCO2) and pHT (total scale) measurements made at the Hakai Institute’s Quadra Island Field Station (QIFS) and from an Environment Canada weather buoy, respectively, as well as discrete seawater measurements of pCO2 and total dissolved inorganic carbon (TCO2) obtained during a number of field campaigns. A relationship between NSS alkalinity and salinity was developed with the discrete datasets and used with the continuous measurements to highly resolve the marine CO2 system. Collectively, these datasets provided insights into the seasonality in this historically under-sampled region and detail the area’s tendency for aragonite saturation state (Ωarag) to be at non-corrosive levels (i.e., Ωarag > 1) only in the upper water column during spring and summer months. This depth zone and time period of reprieve can be periodically interrupted by strong northwesterly winds that drive short-lived (∼1 week) episodes of high-pCO2, low-pH, and low-Ωarag conditions throughout the region. Interannual variability in summertime conditions was evident and linked to reduced northwesterly winds and increased stratification. Anthropogenic CO2 in NSS surface water was estimated using data from 2017 combined with the global atmospheric CO2 forcing for the period 1765 to 2100, and projected a mean value of 49 ± 5 μmol kg-1 for 2018. The estimated trend in anthropogenic CO2 was further used to assess the evolution of Ωarag and pHT levels in NSS surface water, and revealed that wintertime corrosive Ωarag conditions were likely absent pre-1900. The percent of the year spent above Ωarag = 1 has dropped from ∼98% in 1900 to ∼60% by 2018. Over the coming decades, winter pHT and spring and summer Ωarag are projected to decline to conditions below identified biological thresholds for select vulnerable species.

Continue reading ‘Marine CO2 patterns in the northern Salish Sea’

Diurnally fluctuating pCO2 modifies the physiological responses of coral recruits under ocean acidification

Diurnal pCO2 fluctuations have the potential to modulate the biological impact of ocean acidification (OA) on reef calcifiers, yet little is known about the physiological and biochemical responses of scleractinian corals to fluctuating carbonate chemistry under OA. Here, we exposed newly settled Pocillopora damicornis for 7 days to ambient pCO2, steady and elevated pCO2 (stable OA) and diurnally fluctuating pCO2 under future OA scenario (fluctuating OA). We measured the photo-physiology, growth (lateral growth, budding and calcification), oxidative stress and activities of carbonic anhydrase (CA), Ca-ATPase and Mg-ATPase. Results showed that while OA enhanced the photochemical performance of in hospite symbionts, it also increased catalase activity and lipid peroxidation. Furthermore, both OA treatments altered the activities of host and symbiont CA, suggesting functional changes in the uptake of dissolved inorganic carbon (DIC) for photosynthesis and calcification. Most importantly, only the fluctuating OA treatment resulted in a slight drop in calcification with concurrent up-regulation of Ca-ATPase and Mg-ATPase, implying increased energy expenditure on calcification. Consequently, asexual budding rates decreased by 50% under fluctuating OA. These results suggest that diel pCO2 oscillations could modify the physiological responses and potentially alter the energy budget of coral recruits under future OA, and that fluctuating OA is more energetically expensive for the maintenance of coral recruits than stable OA.

Continue reading ‘Diurnally fluctuating pCO2 modifies the physiological responses of coral recruits under ocean acidification’

Pacific geoduck (Panopea generosa) resilience to natural pH variation

Pacific geoduck aquaculture is a growing industry, however little is known about how geoduck respond to varying environmental conditions, or how production might be impacted by low pH associated with ocean acidification. Ocean acidification research is increasingly incorporating multiple environmental drivers and natural pH variability into biological response studies for more complete understanding of the effects of projected ocean conditions. In this study, eelgrass habitats and environmental heterogeneity across four estuarine bays were leveraged to examine low pH effects on geoduck under different natural regimes, using proteomics to assess physiology. Juvenile geoduck were deployed in eelgrass and adjacent unvegetated habitats for 30 days while pH, temperature, dissolved oxygen, and salinity were monitored. Across the four bays pH was lower in unvegetated habitats compared to eelgrass habitats, however this did not impact geoduck growth, survival, or proteomic expression patterns. However, across all sites temperature and dissolved oxygen corresponded to growth and protein expression patterns. Specifically, three protein abundance levels (trifunctional-enzyme β-subunit, puromycin-sensitive aminopeptidase, and heat shock protein 90-⍺) and shell 16 growth positively correlated with dissolved oxygen variability and inversely correlated with mean 17 temperature. These results demonstrate that geoduck are resilient to low pH in a natural setting, 18 and other abiotic factors (i.e. temperature, dissolved oxygen variability) may have a greater 19 influence on geoduck physiology. In addition this study contributes to the understanding of how 20 eelgrass patches influences water chemistry.

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Coastal hypoxia in the Jinhae Bay, South Korea: mechanism, spatiotemporal variation, and implications (based on 2011 survey)

Hypoxia (dissolved oxygen ≤2 mg L−1), which occurs frequently in coastal regions due to eutrophication, is a serious environmental problem in marine ecosystems. The areal extent of hypoxic regions has increased globally in recent decades. Jinhae Bay (JB) on the southeastern coast of South Korea has suffered from seasonal hypoxia due to increased anthropogenic activities since the 1970s. However, no intensive study has examined hypoxia in JB, although it is a scientific, social, and economic concern. We conducted monthly hydrographic surveys of JB in 2011 and present the mechanism of the hypoxia and its spatiotemporal variation there. The advent of hypoxic waters in the JB was initiated locally by the combination of developing stratification and increased benthic (bottom waters sediments zone) remineralization in early June. From mid-July to early September, the hypoxia extended to the entire region, despite constant organic matter content in the benthic layer, due mainly to strong stratification, resulting in stagnant water circulation. During September, the hypoxia was maintained by a combination of physical and biogeochemical effects, although the areal extent of the hypoxic regions was substantially reduced. Overall, the hypoxia was present from early June until late September, with monthly spatiotemporal variation. The hypoxic waters tended to have low pH values, indicating an association with coastal acidification. JB, a small coastal region, suffers from serious environmental problems that urgently need our attention.

Continue reading ‘Coastal hypoxia in the Jinhae Bay, South Korea: mechanism, spatiotemporal variation, and implications (based on 2011 survey)’

An ocean acidification-simulated system and its application in coral physiological studies

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 over 15 d. Correspondingly, the coral calcification of G. fascicularis gradually decreased with reduced pH.

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Sporophytic photosynthesis and gametophytic growth of the kelp Ecklonia stolonifera affected by ocean acidification and warming

Juvenile sporophytes and gametophytes of Ecklonia stolonifera were incubated in combinations of three pCO2 levels (360, 720 and 980 ppmv) and two temperatures (10 and 15°C for sporophytes; 15 and 20°C for gametophytes) to examine potential effects of climate change on photosynthesis and growth. Sporophytes had significantly higher maximum quantum yields (Fv/Fm) and maximum relative electron transport rates (rETRmax) at 720 ppmv than 360 and 980 ppmv. Also, these parameters were significantly lower at higher temperature of 15°C than at 10°C. Growth of female gametophytes was maximal at 360 ppmv rather than enriched pCO2 levels. Female gametophytes had significantly lower growth at higher temperature of 20°C than at 15°C. These results indicate effects of elevated pCO2 varied between generations: stimulating sporophytic photosynthesis and inhibiting gametophytic growth. Ocean acidification and warming would constitute a grave threat to seedling cultivation of E. stolonifera caused by growth inhibition of gametophytes at high pCO2 levels and temperatures.

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Modeled effect of coastal biogeochemical processes, climate variability, and ocean acidification on aragonite saturation state in the Bering Sea

The Bering Sea is highly vulnerable to ocean acidification (OA) due to naturally cold, poorly buffered waters and ocean mixing processes. Harsh weather conditions within this rapidly changing, geographically remote environment have limited the quantity of carbon chemistry data, thereby hampering efforts to understand underlying spatial-temporal variability and detect long-term trends. We add carbonate chemistry to a regional biogeochemical model of the Bering Sea to explore the underlying mechanisms driving carbon dynamics over a decadal hindcast (2003–2012). The results illustrate that coastal processes generate considerable spatial variability in the biogeochemistry and vulnerability of Bering Sea shelf water to OA. Substantial seasonal biological productivity maintains high supersaturation of aragonite on the outer shelf, whereas riverine freshwater runoff loaded with allochthonous carbon decreases aragonite saturation states (ΩArag) to values below 1 on the inner shelf. Over the entire 2003–2012 model hindcast, annual surface ΩArag decreases by 0.025 – 0.04 units/year due to positive trends in the partial pressure of carbon dioxide (pCO2) in surface waters and dissolved inorganic carbon (DIC). Variability in this trend is driven by an increase in fall phytoplankton productivity and shelf carbon uptake, occurring during a transition from a relatively warm (2003–2005) to cold (2010–2012) temperature regime. Our results illustrate how local biogeochemical processes and climate variability can modify projected rates of OA within a coastal shelf system.

Continue reading ‘Modeled effect of coastal biogeochemical processes, climate variability, and ocean acidification on aragonite saturation state in the Bering Sea’

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Ocean acidification in the IPCC AR5 WG II

OUP book