Posts Tagged 'chemistry'

Ecological and functional consequences of coastal ocean acidification: perspectives from the Baltic-Skagerrak System

Ocean temperatures are rising; species are shifting poleward, and pH is falling (ocean acidification, OA). We summarise current understanding of OA in the brackish Baltic-Skagerrak System, focussing on the direct, indirect and interactive effects of OA with other anthropogenic drivers on marine biogeochemistry, organisms and ecosystems. Substantial recent advances reveal a pattern of stronger responses (positive or negative) of species than ecosystems, more positive responses at lower trophic levels and strong indirect interactions in food-webs. Common emergent themes were as follows: OA drives planktonic systems toward the microbial loop, reducing energy transfer to zooplankton and fish; and nutrient/food availability ameliorates negative impacts of OA. We identify several key areas for further research, notably the need for OA-relevant biogeochemical and ecosystem models, and understanding the ecological and evolutionary capacity of Baltic-Skagerrak ecosystems to respond to OA and other anthropogenic drivers.

Continue reading ‘Ecological and functional consequences of coastal ocean acidification: perspectives from the Baltic-Skagerrak System’

Decadal‐scale increases of anthropogenic CO2 in Antarctic Bottom Water in the Indian and western Pacific sectors of the Southern Ocean

We determined decadal‐scale increases of anthropogenic CO2 in the water column using data sets collected 17 years apart (1994‐1996 and 2012‐2013) along a transect at nominal 62°S in the Indian and western Pacific sectors of the Southern Ocean. Large increases of anthropogenic CO2 (up to 9.1 ± 1.5 μmol kg–1), closely following atmospheric CO2 increases, were found in Antarctic Bottom Water (AABW), previously considered a small sink of anthropogenic CO2. Vertical distributions of anthropogenic CO2 increases showed significant positive correlations with those of changes in CFC‐12 and SF6, implying that the distributions were mainly controlled by physical processes such as ventilation and circulation. Calculated uptake rates of anthropogenic CO2 by AABW were between 0.29 and 0.39 mol m–2 yr–1 in five longitudinal segments of the transect. In accounting for the large increase of anthropogenic CO2 in AABW, sea surface conditions in the formation region of AABW are important.

Continue reading ‘Decadal‐scale increases of anthropogenic CO2 in Antarctic Bottom Water in the Indian and western Pacific sectors of the Southern Ocean’

Examining the impact of tropical cyclones on air‐sea CO2 exchanges in the Bay of Bengal based on satellite data and in‐situ observations

The impact of tropical cyclones (TCs) on the CO2 partial pressure at the sea surface (pCO2sea) and air‐sea CO2 flux (FCO2) in the Bay of Bengal (BoB) was quantified based on satellite data and in‐situ observations between November 2013 and January 2017. The in‐situ observations were made at the BoB Ocean Acidification (BOBOA) mooring buoy. A weak time‐mean net source of 55.78±11.16 mmol CO2 m–2 yr–1 at the BOBOA site was estimated during this period. A wide range in increases of pCO2sea (1.0–14.8 μatm) induced by TCs occurred in post‐monsoon (October–December), and large decreases of pCO2sea (–14.0 μatm) occurred in pre‐monsoon (March–May). Large vertical differences in the ratio of dissolved inorganic carbon (DIC) to total alkalinity (TA) in the upper layer (∆DIC/TA) were responsible for increasing pCO2sea in post‐monsoon. Relatively small values of ∆DIC/TA were responsible for decreasing pCO2sea in pre‐monsoon. Five TCs (Hudhud, Five, Kyant, Vardah and Roanu) were considered. Hudhud significantly enhanced CO2 efflux (18.49±3.70 mmol CO2 m–2) in oversaturated areas due to the wind effect during the storm and ‘wind‐pump’ effects after the storm. Vardah insignificantly changed FCO2 (1.22±0.24 mmol CO2 m–2) in undersaturated areas because of the counteraction of these two effects. Roanu significantly enhanced CO2 efflux (19.08±3.82 mmol CO2 m–2) in highly oversaturated conditions (∆pCO2 > 20 μatm) since the wind effect greatly exceeded the ‘wind‐pump’ effects. These five TCs were estimated to account for 55±23% of the annual‐mean CO2 annual efflux, suggesting that TCs have significant impacts on the carbon cycle in the BoB.

Continue reading ‘Examining the impact of tropical cyclones on air‐sea CO2 exchanges in the Bay of Bengal based on satellite data and in‐situ observations’

The ocean-atmospheric condition around Pieh Islands – Western Sumatra, Indonesia and its role on coral reef resilience

Pieh Islands located at the Western Sumatra is one of the most affected areas by massive coral bleaching during 2015-2016. The persistence warming or cooling of sea surface temperature due to regional climate phenomena such as El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) put the coral reef into stress condition leading into coral bleaching. However, corals have an ability to recover from such bleaching condition into normal state by reducing its stressors. A suitable oceanographic condition such as normal range of temperature and salinity, low nutrient concentration, and low sedimentation rate could support corals recovery process. This study aims to understand the variability of the ocean and atmospheric data and its role in coral reef recovery. Data gained from in situ measurements of water quality at Pieh Marine Conservation Area (PMCA) on June 2018. Several historical ocean-atmospheric data were collected to analyze their temporal variability. It is confirmed that the bleaching event was caused by positive IOD and El Niño condition in 2015-2016. However, there is the sign of coral reef recovery during 2017-2018 which is suggested due to the relatively normal condition of the ocean and atmospheric parameters in Pieh Islands.

Continue reading ‘The ocean-atmospheric condition around Pieh Islands – Western Sumatra, Indonesia and its role on coral reef resilience’

The invisible carbon footprint as a hidden impact of peatland degradation inducing marine carbonate dissolution in Sumatra, Indonesia

In Indonesia, land use change (LUC) in the form of peatland degradation induces carbon loss through direct CO2 emissions, but also via soil leaching of which circa 50% is decomposed and emitted as CO2 from the rivers. However, the fate of the remaining exported leached carbon is uncertain. Here, we show that the majority of this carbon is respired in the estuaries and emitted to the atmosphere. However, a portion is adsorbed into the marine carbon pool where it favors CaCO3 dissolution and can therefore be seen as the invisible carbon footprint. We conclude that the effects of LUC stretch beyond the terrestrial realm and are not limited to CO2 emissions, but also affect marine ecosystems. Considering the ecological and economical importance of these ecosystems, it is important that this so far invisible carbon footprint, as well as the aquatic and marine CO2 emissions, are included in climate mitigation strategies.

Continue reading ‘The invisible carbon footprint as a hidden impact of peatland degradation inducing marine carbonate dissolution in Sumatra, Indonesia’

Fast and stable optical pH sensor materials for oceanographic applications

Highlights

• 4 novel optical sensor materials for pH measurements in seawater.
• 3 strategies for covalent immobilization of pH indicator into a hydrogel.
• Fast response times, excellent stability and low cross sensitivities to temperature and salinity.
• Successful application demonstration in several deployments.

Abstract

The study reports preparation and detailed comparison of four new pH sensor materials for seawater measurements. The composition of the sensors is optimized in several iterations to ensure optimal dynamic range, fast response time at low temperatures, low cross-sensitivities to temperature (dpKa/dT ∼ -0.013 pH units/K) and negligible cross sensitivity to ionic strength above salinity 15 PSU. The first generation (material “pH-1″) utilizes a pH indicator which is physically entrapped into a polyurethane hydrogel. This material shows satisfactory performance only at comparably high temperatures with response times being extremely long at low temperatures (t95 > 2 h at 5 °C). The three other materials utilize cross-linked hydrophilic polymers based on poly(acryloylmorpholine) with indicator dye covalently coupled to the polymer. They feature fast response times at low temperatures (t90 < 1 min at 5 °C). Moreover, the last two generations (“pH-3″ and “pH-4″) showed no drift over 54 days at 10 °C and only a drift of 0.003 pH units/day at 25 °C. Although the stability and the sensing properties of these materials are rather similar, the synthetic effort varies considerably. The material of the fourth generation “pH-4″ explores a novel approach of covalent coupling via B–O linkage and is characterized by low synthetic effort and the pKa value optimal for seawater measurements (8.05 at 20 °C). Importantly, all new sensor materials are spectrally compatible to a recently presented seawater optode system for combined pH, pO2 and pCO2 measurements which facilitates their application in marine environment.

Continue reading ‘Fast and stable optical pH sensor materials for oceanographic applications’

Suitability of the shallow water hydrothermal system at Ambitle Island (Papua New Guinea) to study the effect of high pCO2 on coral reefs

Highlights

• Volcanic CO2vents and seeps acidify Tutum Bay
• HCorals survive at pH levels lower than climate change projected levels for the end of this century
• Hydrothermal vents in Tutum Bay are enriched in some metals, but concentrations are quickly diluted by mixing with seawater
• Surface water was enriched in arsenic and silica, although reef values were found to be lower

Abstract

Volcanic CO2 seeps were successfully used to predict coral reef response to ocean acidification, although toxic elements, often characteristic of hydrothermal vents were rarely reported. We measured the physicochemical conditions, seawater carbonate chemistry and trace elements in Tutum Bay, Papua New Guinea. There, intense emission of hydrothermal fluids and CO2 expose the coral reef to a seawater pHT between 7.6 and 7.7.
Arsenic and silica were enriched by up to six times in surface seawater, while bottom concentrations were lower and thus similar to coral reefs worldwide. Manganese, cesium, iron and zinc concentrations fell into the range of other coastal environments. Our measurements suggest that Tutum Bay is a suitable site to study the response of coral reefs to high pCO2. Considering that arsenic is a common metal in hydrothermal fluids, its characterization should be included in any study that uses volcanic CO2 seeps as natural laboratories for ocean acidification.

Continue reading ‘Suitability of the shallow water hydrothermal system at Ambitle Island (Papua New Guinea) to study the effect of high pCO2 on coral reefs’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book