Lecture: Sensitivity of coral trout (Plectropomus) to increasing temperature, ocean acidification and habitat degradation

Presented by: Prof Morgan Pratchett, ARC CoE Coral Reef Studies, Townsville
When: Thursday, 24th of July 2014; 12:00 to 13:00 hrs
Where: Building 19 (Kevin Stark Research Building), Room #106 (upstairs), JCU, Townsville. Video-linked to the University of Queensland (GCI Boardroom, Level 7, Gehrmann Building 60.

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Processes determining the marine alkalinity and carbonate saturation distributions

We introduce a composite tracer, Alk*, that has a global distribution primarily determined by CaCO3 precipitation and dissolution. Alk* also highlights riverine alkalinity plumes that are due to dissolved calcium carbonate from land. We estimate the Arctic receives approximately twice the riverine alkalinity per unit area as the Atlantic, and 8 times that of the other oceans. Riverine inputs broadly elevate Alk* in the Arctic surface and particularly near river mouths. Strong net carbonate precipitation lowers basin mean Indian and Atlantic Alk*, while upwelling of dissolved CaCO3 rich deep waters elevates Northern Pacific and Southern Ocean Alk*. We use the Alk* distribution to estimate the carbonate saturation variability resulting from CaCO3 cycling and other processes. We show regional variations in surface carbonate saturation are due to temperature changes driving CO2 fluxes and, to a lesser extent, freshwater cycling. Calcium carbonate cycling plays a tertiary role. Monitoring the Alk* distribution would allow us to isolate the impact of acidification on biological calcification and remineralization.

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The thing you can’t measure: ocean acidification threatens culture and identity in New Zealand

These last two weeks, I have shared stories of how ocean acidification could affect economies around the world. These tangible impacts can be measured by changes in jobs, access to resources and overall economic condition. But what about the impacts you can’t measure? What will those changes be, and how will they affect people?

Throughout my Watson Fellowship, I sought to understand these intangible impacts. These hard-to-measure threats to things like one’s sense of place, identity and culture may not have dollar signs behind them, but to many of the people I spoke with, they were of utmost importance.

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Race on to save endangered Cayman corals

Local and international marine experts are joining forces in the ocean around Little Cayman on an important conservation project to try and understand and then save endangered local coral species. The plight of the now critically endangered staghorn coral, which was once one of the most abundant corals on Caribbean reefs, is at the top of the agenda. A mysterious die-off starting in the 1980s resulted in a loss of almost 90% of the population. As a result both staghorn and elkhorn coral, in the genus Acropora, are listed as criticalely Endangered on the IUCN Red List of threatened species. The Central Caribbean Marine Institute and the Department of Environment have been using a grant from the Darwin Initiative to fund research on the biodiversity of coral and what they can do to increase this species.

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Coping with climate change? Copepods experience drastic variations in their physicochemical environment on a diurnal basis

Migratory zooplankton, such as copepods experience widely varying conditions in their physicochemical environment on a diurnal basis. The amplitude of the fluctuations may affect the copepods’ ability to respond to climate change. The environment in coastal areas is naturally fluctuating and the effects of ocean acidification are difficult to predict. Negative effects on copepods may affect the whole food web as they are the most abundant zooplankton, constituting a major part of the diet of fish. In this study, we determined the vertical profiles of an array of environmental variables and the vertical distribution of common copepods in a shallow coastal area of the Baltic Sea. We sampled once a month, in June, July and August, every sixth hour during 24 h. We found that copepods experience a change in pH of more than 0.5 units and 5 °C change in temperature during migration. Thus, on diurnal time scales copepods experience a range in their physicochemical environment that is equal to or larger than the predicted climate change scenarios.

Continue reading ‘Coping with climate change? Copepods experience drastic variations in their physicochemical environment on a diurnal basis’

Effects of different salinities and pH on the growth and proximate composition of Nannochloropsis sp. and Tetraselmis sp. isolated from South China Sea cultured under control and natural condition

Nannochloropsis sp. and Tetraselmis sp. are widely used in aquaculture as a source of protein, lipid and carbohydrate. The growth and proximate composition of microalgae could be affected by different culture conditions especially salinity, temperature and light. Thus, this study was aimed to compare the growth and proximate composition of Nannochloropsis sp. and Tetraselmis sp. cultured in different salinities and pH under different culture conditions. In this study Nannochloropsis sp. and Tetraselmis sp. were isolated from South China Sea and cultured at different salinities of 20, 30 and 40 ppt and different pH of 5.5, 7.5, 8.5 and 9.5 under natural and control condition until stationary phase. Results showed that Nannochloropsis sp. and Tetraselmis sp. had significantly higher (p < 0.05) cell density, lipid and carbohydrate content under control condition at 30 ppt. However, protein content was significantly higher (p < 0.05) in Nannochloropsis sp. when cultured under natural condition at 30 ppt. High cell density, protein, lipid and carbohydrate content was obtained when cultured at pH 7.5 and 8.5 for both species. The output of this study could be considered for Nannochloropsis sp. and Tetraselmis sp. cultivation to provide appropriate levels of protein, lipid and carbohydrate as feed supplement for aquaculture organisms.

Continue reading ‘Effects of different salinities and pH on the growth and proximate composition of Nannochloropsis sp. and Tetraselmis sp. isolated from South China Sea cultured under control and natural condition’

Laboratory experiment investigating the impact of ocean acidification on calcareous organisms

The increase in ocean acidity since preindustrial times may have deleterious consequences for marine organisms, particularly those with calcareous structures. We present a laboratory experiment to investigate this impact with general, introductory, environmental, and nonmajors chemistry students. For simplicity and homogeneity, calcite was substituted for calcareous organisms and placed in buffer solutions of variable acidity. After 30 min, students quantified the percent mass loss of calcite in their buffer. Individual student data was then pooled into a class spreadsheet for further analysis. This experiment could enable a class discussion on ocean acidification supplemented with primary and secondary literature.

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