Posts Tagged 'chemistry'

Acoustic signal and noise changes in the Beaufort Sea Pacific Water duct under anticipated future acidification of Arctic Ocean waters

It is predicted that Arctic Ocean acidity will increase during the next century as a result of carbon dioxide accumulation in the atmosphere and migration into ocean waters. This change has implications for sound transmission because low-pH seawater absorbs less sound than high-pH water. Altered pH will affect sound in the 0.3−10 kHz range if the criterion is met that absorption is the primary cause of attenuation, rather than the alternatives of loss in the ice or seabed. Recent work has exploited sound that meets the criterion, sound trapped in a Beaufort Sea duct composed of Pacific Winter Water underlying Pacific Summer Water. Arctic pH is expected to drop from 8.1 to 7.9 (approximately) over the next 30−50 yr, and effects of this chemical alteration on the intensity levels of this ducted sound, and on noise, are examined here. Sound near 900 Hz is predicted to undergo the greatest change, traveling up to 38% further. At ranges of 100−300 km, sound levels from a source in the duct may increase by 7 dB or more. Noise would also increase, but noise is ducted less efficiently, with the result that 1 kHz noise is predicted to rise approximately 0.5 dB.

Continue reading ‘Acoustic signal and noise changes in the Beaufort Sea Pacific Water duct under anticipated future acidification of Arctic Ocean waters’

The regulation of coralline algal physiology, an in situ study of Corallina officinalis (Corallinales, Rhodophyta) (update)

Calcified macroalgae are critical components of marine ecosystems worldwide, but face considerable threat both from climate change (increasing water temperatures) and ocean acidification (decreasing ocean pH and carbonate saturation). It is thus fundamental to constrain the relationships between key abiotic stressors and the physiological processes that govern coralline algal growth and survival. Here we characterize the complex relationships between the abiotic environment of rock pool habitats and the physiology of the geniculate red coralline alga, Corallina officinalis (Corallinales, Rhodophyta). Paired assessment of irradiance, water temperature and carbonate chemistry, with C. officinalis net production (NP), respiration (R) and net calcification (NG) was performed in a south-western UK field site, at multiple temporal scales (seasonal, diurnal and tidal). Strong seasonality was observed in NP and night-time R, with a Pmax of 22.35 µmol DIC (g DW)−1 h−1, Ek of 300 µmol photons m−2 s−1 and R of 3.29 µmol DIC (g DW)−1 h−1 determined across the complete annual cycle. NP showed a significant exponential relationship with irradiance (R2 = 0.67), although was temperature dependent given ambient irradiance  > Ek for the majority of the annual cycle. Over tidal emersion periods, dynamics in NP highlighted the ability of C. officinalis to acquire inorganic carbon despite significant fluctuations in carbonate chemistry. Across all data, NG was highly predictable (R2 = 0.80) by irradiance, water temperature and carbonate chemistry, providing a NGmax of 3.94 µmol CaCO3 (g DW)−1 h−1 and Ek of 113 µmol photons m−2 s−1. Light NG showed strong seasonality and significant coupling to NP (R2 = 0.65) as opposed to rock pool water carbonate saturation. In contrast, the direction of dark NG (dissolution vs. precipitation) was strongly related to carbonate saturation, mimicking abiotic precipitation dynamics. Data demonstrated that C. officinalis is adapted to both long-term (seasonal) and short-term (tidal) variability in environmental stressors, although the balance between metabolic processes and the external environment may be significantly impacted by future climate change.

Continue reading ‘The regulation of coralline algal physiology, an in situ study of Corallina officinalis (Corallinales, Rhodophyta) (update)’

Advancing ocean acidification biology using Durafet® pH electrodes

Research assessing the biological impacts of global ocean change often requires a burdensome characterization of seawater carbonate chemistry. For laboratory-based ocean acidification research, this impedes the scope of experimental design. Honeywell Durafet® III pH electrodes provide precise and continuous seawater pH measurements. In addition to use in oceanographic sensor packages, Durafets can also be used in the laboratory to track and control seawater treatments via Honeywell Universal Dual Analyzers (UDAs). Here we provide performance data, instructions, and step-by-step recommendations for use of multiple UDA-Durafets. Durafet pH measurements were within ±0.005 units pHT of spectrophotometric measurements and agreement among eight Durafets was better than ±0.005 units pHT. These results indicate equal performance to Durafets in oceanographic sensor packages, but methods for calibration and quality control differ. Use of UDA-Durafets vastly improves time-course documentation of experimental conditions and reduces person-hours dedicated to this activity. Due to the versatility of integrating Durafets in laboratory seawater systems, this technology opens the door to advance the scale of questions that the ocean acidification research community aims to address.

Continue reading ‘Advancing ocean acidification biology using Durafet® pH electrodes’

Pteropods are excellent recorders of surface temperature and carbonate ion concentration

Pteropods are among the first responders to ocean acidification and warming, but have not yet been widely explored as carriers of marine paleoenvironmental signals. In order to characterize the stable isotopic composition of aragonitic pteropod shells and their variation in response to climate change parameters, such as seawater temperature, pteropod shells (Heliconoides inflatus) were collected along a latitudinal transect in the Atlantic Ocean (31° N to 38° S). Comparison of shell oxygen isotopic composition to depth changes in the calculated aragonite equilibrium oxygen isotope values implies shallow calcification depths for H. inflatus (75 m). This species is therefore a good potential proxy carrier for past variations in surface ocean properties. Furthermore, we identified pteropod shells to be excellent recorders of climate change, as carbonate ion concentration and temperature in the upper water column have dominant influences on pteropod shell carbon and oxygen isotopic composition. These results, in combination with a broad distribution and high abundance, make the pteropod species studied here, H. inflatus, a promising new proxy carrier in paleoceanography.

Continue reading ‘Pteropods are excellent recorders of surface temperature and carbonate ion concentration’

The potential future contribution of shipping to acidification of the Baltic Sea

International regulation of the emission of acidic sulphur and nitrogen oxides from commercial shipping has focused on the risks to human health, with little attention paid to the consequences for the marine environment. The introduction of stricter regulations in northern Europe has led to substantial investment in scrubbers that absorb the sulphur oxides in a counterflow of seawater. This paper examines the consequences of smokestack and scrubber release of acidic oxides in the Baltic Sea according to a range of scenarios for the coming decades. While shipping is projected to become a major source of strong acid deposition to the Baltic Sea by 2050, the long-term effect on the pH and alkalinity is projected to be significantly smaller than estimated from previous scoping studies. A significant contribution to this difference is the efficient export of surface water acidification to the North Sea on a timescale of 15–20 years.

Continue reading ‘The potential future contribution of shipping to acidification of the Baltic Sea’

Ocean acidification in New Zealand waters: trends and impacts

The threat posed by ocean acidification (OA) to the diversity and productivity of New Zealand marine ecosystems is assessed in a synthesis of published trends and impacts. A 20-year time series in Subantarctic water, and a national coastal monitoring programme, provide insight into pH variability, and context for experimental design, modelling and projections. A review of the potential impact of changes in the carbonate system on the major phyla in New Zealand waters confirms international observations that calcifying organisms, and particularly their early life-history stages, are vulnerable. The synthesis considers ecosystem and socio-economic impacts, and identifies current knowledge gaps and future research directions, including mechanistic studies of OA sensitivity. Advanced ecosystem models of OA, that incorporate the indirect effects of OA and interactions with other climate stressors, are required for robust projection of the future status of New Zealand marine ecosystems.

Continue reading ‘Ocean acidification in New Zealand waters: trends and impacts’

Quantifying metabolically driven pH and oxygen fluctuations in US nearshore habitats at diel to interannual time scales

We compiled and examined 15 years (2002–2016) of high-frequency monitoring data from the National Estuarine Research Reserve System (NERRS) to characterize diel to interannual variability of pH and dissolved oxygen (DO, % saturation) across 16 diverse, shallow-water habitats along the US Atlantic, Gulf of Mexico, Caribbean, and Pacific coasts. We asked whether these systems exhibit a common pH/DO relationship, whether there were detectable interannual trends in temperature, pH, and DO within and across systems, and how pH/DO dynamics would relate to measured levels of nutrients and chlorophyll. Our analyses confirmed that large, metabolically driven, and thus concurrent fluctuations of pH and DO are a unifying feature of nearshore habitats. Moreover, we derived well-constrained relationships that predict (i) monthly mean pH or (ii) mean diel pH fluctuations across systems based on habitat mean salinity and (i) mean DO or (ii) mean diel DO fluctuations. This suggests that common metabolic principles drive diel to seasonal pH/DO variations within as well as across a diversity of estuarine environments. Yearly pH and DO anomalies did not show monotonous trends over the study period and differed considerably between sites and regions. However, weekly anomalies of means, diel minima, and diel ranges of pH and DO changed significantly over time and were strongly correlated to temperature anomalies. These general patterns lend strong empirical support to the notion that coastal acidification—in addition to being driven by eutrophication and atmospheric CO2 increases—is exacerbated simply by warming, likely via increasing community respiration. Nutrient and chlorophyll dynamics were inversely related in these shallow, well-mixed systems, but higher nutrient levels were still associated with lower pH and lower DO levels in most, but not all, systems. Our analyses emphasize the particular dynamics of nearshore habitats and the critical importance of NERRS and its system-wide monitoring program.

Continue reading ‘Quantifying metabolically driven pH and oxygen fluctuations in US nearshore habitats at diel to interannual time scales’

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Ocean acidification in the IPCC AR5 WG II

OUP book