Archive for the 'Science' Category



Autonomous, ISFET-based total alkalinity and pH measurements on a barrier reef of Kāneʻohe Bay

Here we present first of its kind high frequency Total Alkalinity (AT) and pH data from a single solid-state autonomous sensor collected during a 6-day deployment at a barrier reef in Kāneʻohe Bay on the CRIMP-2 buoy. This dual parameter sensor is capable of rapid (<60 s), near simultaneous measurement of the preferred seawater carbonate system parameters, pH and AT without requiring any external reagents or moving parts inherent to the sensor. Its solid state construction, low power consumption, and low titrated volume (nanoliters) requirement make this sensor ideal for in situ monitoring of the aqueous carbon dioxide system. Through signal averaging, we estimate the pH-AT sensor is capable of achieving 2-10 μmol kg-1 precision in AT and 0.005 for pH. The CRIMP-2 site in Hawaiʻi provided an excellent means of validation of the prototype pH-AT sensor due to the extensive observations routinely collected at this site and large daily fluctuations in AT (~116 μmol kg-1) driven primarily by high calcification during the day and occasional CaCO3 mineral dissolution at night. High frequency sampling by the pH-AT sensor reveals details in the diurnal cycle that are nearly impossible to observe by discrete sampling. Greater temporal resolution of the aqueous carbon dioxide system is essential for differentiating various drivers of coral reef health and the response to external influences such as ocean warming and acidification.

Continue reading ‘Autonomous, ISFET-based total alkalinity and pH measurements on a barrier reef of Kāneʻohe Bay’

Origin and accumulation of an anthropogenic CO2 and 13C Suess effect in the Arctic Ocean

We determined the impact of anthropogenic CO2 (Cant) accumulation on the δ13C of dissolved inorganic carbon (DIC) in the Arctic Ocean (i.e., the 13C Suess effect) based on δ13C measurements during a GEOTRACES cruise in 2015. The δ13C decrease was estimated from the amount of Cant change derived by the transit time distribution (TTD) approach and the ratio of the anthropogenic δ13C/DIC change (RC). A significant Cant increase (up to 45 μmol kg−1) and δ13C decrease (up to −0.9‰) extends to ~2000 m in the Canada and Makarov Basin. We find distinctly different RC values for the intermediate water (300–2000 m) and upper halocline water (<200 m) of −0.020 and −0.012‰ (μmol kg−1)−1, respectively, which identifies two sources of Cant accumulation from North Atlantic and North Pacific. Furthermore, estimated RC for intermediate waters is the same as the RC observed in the Greenland Sea and the rate of anthropogenic DIC increase estimated for intermediate waters at 0.9 μmol kg−1 yr−1 is identical to the estimated rate in the Iceland Sea. These observations indicate that the high rate of Cant accumulation and δ13C decrease in the Arctic Ocean is primarily a result of the input of Cant, via ventilation of intermediate waters, from the Nordic Sea rather than local anthropogenic CO2 uptake within the Arctic Basin. We determine the preindustrial δ13C (δ13CPI) distributions and find distinct δ13CPI signatures of the intermediate and upper halocline waters that reflect the difference in δ13CPI–PO4 relationship of Atlantic and Pacific source water.

Continue reading ‘Origin and accumulation of an anthropogenic CO2 and 13C Suess effect in the Arctic Ocean’

Brain regions of marine medaka activated by acute and short-term ocean acidification

Highlights

• Ventricular and periventricular zones of whole brain activated by acidification.

• Cerebral hemisphere and medulla oblongata involved in rapid acid-base regulation.

• Diencephalon and mesencephalon activated by short-term acidification.

Abstract

Altered behaviors have been reported in many marine fish following exposure to high CO2 concentrations. However, the mechanistic link between elevated CO2 and activation of brain regions in fish is unknown. Herein, we examined the relative quantification and location of c-Fos expression in marine medaka following acute (360 min) and short-term (7 d) exposure to CO2-enriched water (1000 ppm and 1800 ppm CO2). In the control and two treatment groups, pH was stable at 8.21, 7.92 and 7.64, respectively. After acute exposure to seawater acidified by enrichment with CO2, there was a clear upregulation of c-Fos protein in the medaka brain (P < 0.05). c-Fos protein expression peaked after 120 min exposure in the two treatment groups and thereafter began to decline. There were marked increases in c-Fos-labeling in the ventricular and periventricular zones of the cerebral hemispheres and the medulla oblongata. After 1800 ppm CO2 exposure for 7 d, medaka showed significant preference for dark zones during the initial 2 min period. c-Fos protein expression in the ventricular and periventricular zones of the diencephalon in medaka exposed to 1000 ppm and 1800 ppm CO2 were 0.51 ± 0.10 and 1.34 ± 0.30, respectively, which were significantly higher than controls (P < 0.05). Highest doublecortin protein expression occurred in theventricular zones of the diencephalon and mesencephalon. These findings suggest that the ventricular and periventricular zones of the cerebral hemispheres and the medulla oblongata of marine medaka are involved in rapid acid-base regulation. Prolonged ocean acidification may induce cell mitosis and differentiation in the adult medaka brain.

Continue reading ‘Brain regions of marine medaka activated by acute and short-term ocean acidification’

Global environmental changes negatively impact temperate seagrass ecosystems

The oceans are increasingly affected by multiple aspects of global change, with substantial impacts on ecosystem functioning and food-web dynamics. While the effects of single factors have been extensively studied, it has become increasingly evident that there is a need to unravel the complexities related to a multiple stressor environment. In a mesocosm experimental study, we exposed a simplified, multi-trophic seagrass ecosystem (composed of seagrass, two shrimp species, and two intermediate predatory fish species) to three global change factors consisting of simulated storm events (Storms), heat shocks (Heat), and ocean acidification (OA), and the combination of all three factors (All). The most striking result indicated that when all factors were combined, there was a negative influence at all trophic levels, while the treatments with individual factors revealed species-specific response patterns. It appeared, however, that single factors may drive the multi-stressor response. All single factors (i.e., Storms, Heat, and OA) had either negative, neutral, or positive effects on fish and shrimp, whereas no effect was recorded for any single stressor on seagrass plants. The findings demonstrate that when several global change factors appear simultaneously, they can have deleterious impacts on seagrass ecosystems, and that the nature of factors and food-web composition may determine the sensitivity level of the system. In a global change scenario, this may have serious and applicable implications for the future of temperate seagrass ecosystems.

Continue reading ‘Global environmental changes negatively impact temperate seagrass ecosystems’

Effects of pH and nitrogen form on Nitzschia closterium growth by linking dynamic with enzyme activity

Highlights

• The growth of Nitzschia closterium was inhibited by ocean acidification with low growth indication.

• Acidification might induce ROS with the enzyme activities (SOD, CAT) increase under lower pH levels.

• Acidification has a more detrimental effect on the growth of N. closterium under NO3–N than NH4–N.

Abstract

In this study, Nitzschia closterium was incubated in seawater at different pH values (8.10, 7.71, and 7.45) and using different nitrogen forms (NO3–N and NH4–N) in the laboratory. The results showed that the growth of N. closterium was inhibited by ocean acidification, with individuals under lower pH levels showing lower growth rates and lower nitrogen uptake rates for both nitrogen forms. The Vmax/Ks ratio decreased with decreasing pH, indicating the inhibition of nitrogen uptake, whereas the ratios for NH4–N cultures were higher than those for NO3–N cultures, implying the highly competitive position of NH4–N. Acidification might induce reactive oxygen species based on the result that the maximum enzyme activities of SuperOxide Dismutase (SOD) and CATalase (CAT) increased under lower pH levels. The SOD and CAT activities for the NO3–N cultures were higher than those for NH4–N cultures at the low pH level, indicating that acidification might cause more oxidative stress for NO3–N cultures than for NH4–N cultures. Thus, ocean acidification might have a more detrimental effect on the growth of N. closterium under NO3–N conditions than NH4–N conditions, with a lower ratio (γ) of the maximum growth rate to the maximum nutrient uptake rate, and a drop in nitrate reductase activity under lower pH levels.

Continue reading ‘Effects of pH and nitrogen form on Nitzschia closterium growth by linking dynamic with enzyme activity’

Impact of climate change and ocean acidification on ocean-based industries and society in Norway

This report presents a review of the scientific literature on how key ecosystems, ecosystem services and ocean-based industries in Norway are affected by climate change and ocean acidification today and under future scenarios. The project has also compiled knowledge on how ocean-based actions can help mitigate and reduce the magnitude of climate change, ocean acidification and environmental problems. Further possible trade-off related to ocean-based action were identified as well as how climate change and ocean acidification may potentially affect these ocean-based opportunities. Finally, the report presents published findings on possible future impacts on society and implications for policy and management.

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ScarFace – seacarb calculations with R Shiny user interface

‘ScarFace’ is a Shiny web application that has been developed to facilitate the usage of the R-package ‘seacarb’ (http://CRAN.R-project.org/package=seacarb). ‘seacarb’ is used to calculate the carbonate chemistry of seawater requiring a command-line usage. For non-friends of bare code, ‘ScarFace’ enables to use ‘seacarb’ via an user interface (ui) without the need for digging into R. The web app implements the most frequently used functions bjerrum(), carb(), and errors(), which can be simply operated by numerical or slider inputs. In addition to single calculations, batch processing can be performed by uploading csv source tables, where there is no need for pre-defined column names or order. If required, propagated errors can be calculated based on source table or manually entered values.

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Ocean acidification in the IPCC AR5 WG II

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