scholarly journals Nutrients attenuate the negative effect of ocean acidification on reef coral calcification in the Arabian Sea upwelling zone (Masirah Island, Oman)

2021 ◽  
Author(s):  
Philipp Michael Spreter ◽  
Markus Reuter ◽  
Regina Mertz-Kraus ◽  
Oliver Taylor ◽  
Thomas Christian Brachert
Keyword(s):  
Ocean Acidification ◽  
Bulk Density ◽  
Arabian Sea ◽  
Reference Data ◽  
Reef Coral ◽  
Extension Rate ◽  
Data Set ◽  
Reef Corals ◽  
Negative Effect ◽  
Arabian Sea Upwelling

Abstract. Tropical shallow-water reefs are the most diverse ecosystem in the ocean. Its persistence rests upon adequate calcification rates of the reef building biota, such as reef corals. Optimum calcification rates of reef corals occur in oligotrophic environments with high seawater saturation states of aragonite (Ωsw), which leads to increased vulnerability to anthropogenic ocean acidification and eutrophication. The calcification response of reef corals to this changing environment is largely unknown, however. Here, we present annually and sub-annually resolved records of calcification rates (n = 3) of the coral Porites from the nutrient rich and low Ωsw Arabian Sea upwelling zone (Masirah Island, Oman). Calcification rates were determined from the product of skeletal extension and bulk density derived from X-ray densitometry. Compared to a reference data set of coral skeletons from typical reef environments (Great Barrier Reef, Hawaii), mean annual skeletal bulk density of Porites from Masirah Island is reduced by 28 %. This density deficit prevails over the entire year and probably reflects a year-round low saturation state of aragonite at the site of calcification (Ωcf), independent of seasonal variations in Ωsw (e.g. upwelling). Mean annual extension rate is 20 % higher than for the reference data set. In particular, extension rate is strongly enhanced during the seasons with the lowest water temperatures, presumably due to a high PO43−/NO3−-ratio promoting rapid upward growth of the skeleton. Enhanced annual extension attenuates the negative effect of low density on calcification rate from −25 % to −11 %, while sub-annual calcification rates during the cool seasons even exceed those of the reference corals. We anticipate optimal nutrient environments (e.g. high PO43−/NO3−-ratios) to have significant potential to compensate the negative effect of ocean acidification on reef coral calcification, thereby allowing to maintain adequate rates of carbonate accumulation, which are essential for preserving this unique ecosystem.

scholarly journals Low Florida coral calcification rates in the Plio-Pleistocene

2016 ◽  
Vol 13 (15) ◽  
pp. 4513-4532 ◽  
Author(s):  
Thomas C. Brachert ◽  
Markus Reuter ◽  
Stefan Krüger ◽  
James S. Klaus ◽  
Kevin Helmle ◽  
...  
Keyword(s):  
Shallow Water ◽  
Bulk Density ◽  
Early Pleistocene ◽  
Extension Rate ◽  
Western Atlantic ◽  
Skeletal Density ◽  
Reef Corals ◽  
Coral Calcification ◽  
Diagenetic Alteration ◽  
Florida Platform

Abstract. In geological outcrops and drill cores from reef frameworks, the skeletons of scleractinian corals are usually leached and more or less completely transformed into sparry calcite because the highly porous skeletons formed of metastable aragonite (CaCO3) undergo rapid diagenetic alteration. Upon alteration, ghost structures of the distinct annual growth bands often allow for reconstructions of annual extension ( =  growth) rates, but information on skeletal density needed for reconstructions of calcification rates is invariably lost. This report presents the bulk density, extension rates and calcification rates of fossil reef corals which underwent minor diagenetic alteration only. The corals derive from unlithified shallow water carbonates of the Florida platform (south-eastern USA), which formed during four interglacial sea level highstands dated approximately 3.2, 2.9, 1.8, and 1.2 Ma in the mid-Pliocene to early Pleistocene. With regard to the preservation, the coral skeletons display smooth growth surfaces with minor volumes of marine aragonite cement within intra-skeletal porosity. Within the skeletal structures, voids are commonly present along centres of calcification which lack secondary cements. Mean extension rates were 0.44 ± 0.19 cm yr−1 (range 0.16 to 0.86 cm yr−1), mean bulk density was 0.96 ± 0.36 g cm−3 (range 0.55 to 1.83 g cm−3) and calcification rates ranged from 0.18 to 0.82 g cm−2 yr−1 (mean 0.38 ± 0.16 g cm−2 yr−1), values which are 50 % of modern shallow-water reef corals. To understand the possible mechanisms behind these low calcification rates, we compared the fossil calcification rates with those of modern zooxanthellate corals (z corals) from the Western Atlantic (WA) and Indo-Pacific calibrated against sea surface temperature (SST). In the fossil data, we found a widely analogous relationship with SST in z corals from the WA, i.e. density increases and extension rate decreases with increasing SST, but over a significantly larger temperature window during the Plio-Pleistocene. With regard to the environment of coral growth, stable isotope proxy data from the fossil corals and the overall structure of the ancient shallow marine communities are consistent with a well-mixed, open marine environment similar to the present-day Florida Reef Tract, but variably affected by intermittent upwelling. Upwelling along the platform may explain low rates of reef coral calcification and inorganic cementation, but is too localised to account also for low extension rates of Pliocene z corals throughout the tropical WA region. Low aragonite saturation on a more global scale in response to rapid glacial–interglacial CO2 cyclicity is also a potential factor, but Plio-Pleistocene atmospheric pCO2 is generally believed to have been broadly similar to the present day. Heat stress related to globally high interglacial SST only episodically moderated by intermittent upwelling affecting the Florida platform seems to be another likely reason for low calcification rates. From these observations we suggest some present coral reef systems to be endangered from future ocean warming.

scholarly journals Low Florida coral calcification rates in the Plio-Pleistocene

2015 ◽  
Vol 12 (24) ◽  
pp. 20515-20555 ◽  
Author(s):  
T. C. Brachert ◽  
M. Reuter ◽  
S. Krüger ◽  
J. S. Klaus ◽  
K. Helmle ◽  
...  
Keyword(s):  
Shallow Water ◽  
Reef Coral ◽  
Early Pleistocene ◽  
Extension Rate ◽  
Western Atlantic ◽  
Skeletal Density ◽  
Reef Corals ◽  
Coral Calcification ◽  
Diagenetic Alteration ◽  
Florida Platform

Abstract. In geological outcrops and drill cores from reef frameworks, the skeletons of scleractinian corals are usually leached and more or less completely transformed into sparry calcite because the highly porous skeletons formed of metastable aragonite (CaCO3) undergo rapid diagenetic alteration. Upon alteration, ghost structures of the distinct annual growth bands may be retained allowing for reconstructions of annual extension (= growth) rates, but information on skeletal density needed for reconstructions of calcification rates is invariably lost. Here we report the first data of calcification rates of fossil reef corals which escaped diagenetic alteration. The corals derive from unlithified shallow water carbonates of the Florida platform (southeastern USA), which formed during four interglacial sea level highstands dated 3.2, 2.9, 1.8, and 1.2 Ma in the mid Pliocene to early Pleistocene. With regard to the preservation, the coral skeletons display smooth growth surfaces with minor volumes of marine aragonite cement within intra-skeletal porosity. Within the skeletal structures, dissolution is minor along centers of calcification. Mean extension rates were 0.44 ± 0.19 cm yr−1 (range 0.16 to 0.86 cm yr−1) and mean bulk density was 0.86 ± 0.36 g cm−3 (range 0.55 to 1.22 g cm−3). Correspondingly, calcification rates ranged from 0.18 to 0.82 g cm−2 yr−1 (mean 0.38 ± 0.16 g cm−2 yr−1), values which are 50 % of modern shallow-water reef corals. To understand the possible mechanisms behind these low calcification rates, we compared the fossil calcification with modern zooxanthellate-coral (z-coral) rates from the Western Atlantic (WA) and Indo-Pacific (IP) calibrated against sea surface temperature (SST). In the fossil data, we found an analogous relationship with SST in z-corals from the WA, i.e. density increases and extension rate decreases with increasing SST, but over a significantly larger temperature window during the Plio-Pleistocene. With regard to the environment of coral growth, stable isotope proxy data from the fossil corals and the overall structure of the ancient shallow marine communities are consistent with a well-mixed, open marine environment similar to the present-day Florida Reef Tract, but variably affected by intermittent upwelling. Upwelling along the platform may explain low rates of reef coral calcification and inorganic cementation, but is too localized to account for low extension rates of Pliocene z-corals recorded throughout the tropical Caribbean in the western Atlantic region. Low aragonite saturation on a more global scale in response to rapid glacial/interglacial CO2 cyclicity is also a potential factor, but Plio-Pleistocene atmospheric pCO2 is believed to have been broadly similar to the present-day. Heat stress related to globally high interglacial SST, only episodically moderated by intermittent upwelling affecting the Florida platform seems to be the most likely reason for low calcification rates. From these observations we suggest some present coral reef systems to be endangered from future ocean warming.

Variability, trend and controlling factors of Ocean acidification over Western Arabian Sea upwelling region

2019 ◽  
Vol 209 ◽  
pp. 14-24 ◽  
Author(s):  
Mohanan Geethalekshmi Sreeush ◽  
Saran Rajendran ◽  
Vinu Valsala ◽  
Sreenivas Pentakota ◽  
K.V.S.R. Prasad ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Arabian Sea ◽  
Controlling Factors ◽  
Arabian Sea Upwelling

scholarly journals Evolution of the Arabian Sea Upwelling from the Last Millennium to the Future as Simulated by Earth System Models

Climate ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 72
Author(s):  
Xing Yi ◽  
Birgit Hünicke ◽  
Eduardo Zorita
Keyword(s):  
Arabian Sea ◽  
Positive Trend ◽  
Last Millennium ◽  
Earth System ◽  
System Models ◽  
Sediment Records ◽  
The Future ◽  
Water Stratification ◽  
Arabian Sea Upwelling ◽  
Earth System Models

Arabian Sea upwelling in the past has been generally studied based on the sediment records. We apply two earth system models and analyze the simulated water vertical velocity to investigate coastal upwelling in the western Arabian Sea over the last millennium. In addition, two models with slightly different configurations are also employed to study the upwelling in the 21st century under the strongest and the weakest greenhouse gas emission scenarios. With a negative long-term trend caused by the orbital forcing of the models, the upwelling over the last millennium is found to be closely correlated with the sea surface temperature, the Indian summer Monsoon and the sediment records. The future upwelling under the Representative Concentration Pathway (RCP) 8.5 scenario reveals a negative trend, in contrast with the positive trend displayed by the upwelling favorable along-shore winds. Therefore, it is likely that other factors, like water stratification in the upper ocean layers caused by the stronger surface warming, overrides the effect from the upwelling favorable wind. No significant trend is found for the upwelling under the RCP2.6 scenario, which is likely due to a compensation between the opposing effects of the increase in upwelling favorable winds and the water stratification.

scholarly journals A Physical Activity Reference Data-Set Recorded from Older Adults Using Body-Worn Inertial Sensors and Video Technology—The ADAPT Study Data-Set

Sensors ◽  
2017 ◽  
Vol 17 (3) ◽  
pp. 559 ◽  
Author(s):  
Alan Bourke ◽  
Espen Ihlen ◽  
Ronny Bergquist ◽  
Per Wik ◽  
Beatrix Vereijken ◽  
...  
Keyword(s):  
Physical Activity ◽  
Older Adults ◽  
Reference Data ◽  
Inertial Sensors ◽  
Study Data ◽  
Video Technology ◽  
Data Set

Political and Institutional Checks on Corruption

2009 ◽  
Vol 42 (9) ◽  
pp. 1217-1244 ◽  
Author(s):  
Marcus André Melo ◽  
Carlos Pereira ◽  
Carlos Mauricio Figueiredo
Keyword(s):  
Political Competition ◽  
New Democracies ◽  
Data Set ◽  
Electoral Connection ◽  
Negative Effect ◽  
Institutional Activism ◽  
Accountability Mechanism ◽  
Empirical Tests ◽  
Performance Determinants ◽  
Positive Direct

This article investigates the performance determinants of accountability institutions in new democracies. Current scholarship on accountability has identified a distinct mechanism through which the introduction of political competition may affect such institutions: the electoral connection or vertical accountability mechanism. This connection is not expected to be effective in new democracies, because political competition is found to be volatile and nonprogrammatic. Another strand of the literature focuses on the effect of power alternation. Government turnover is expected to generate incentives for the creation and strengthening of autonomous institutions. By exploring a unique data set on 33 state audit institutions, the authors bring together these distinct claims and provide systematic empirical tests for them. They find a negative effect of volatility on their institutional activism and a positive (direct and indirect) influence of power alternation on their levels of autonomy and sanctioning patterns.

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