Exciting research has revealed new insights into coral bleaching. By studying the pest anemone Aiptasia pallida, scientists found how Cnidarians induce their own bleaching after exposure to high temperatures!
The intensive use of powerful lighting above marine aquaria is common practice amongst aquarists nowadays. This is now regarded as a necessity for keeping healthy and fast growing corals. Recent studies have indicated that this philosophy is just part of the story…
Coral reefs; what exactly are they? Read this article and step into the wonderful world of tropical coral reefs, supported by beautiful images from photographer Hans Leijnse!
The use of supplements in the (marine) aquarium has always been controversial, dividing hobbyists into two camps. The question is; do supplements really matter? Let's take a look at amino acids; a popular additive nowadays.
Global warming is seen as the number one threat to the world's coral reefs, next to overfishing, pollution and eutrophication. It is common knowledge that elevated sea surface temperatures may cause coral bleaching. That an increase in atmospheric CO2 could be just as threatening, is not.
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| Coral reefs as a calcium reactor? |
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| Written by Tim Wijgerde | |
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global warming is seen as the number one threat to the world's coral reefs, next to overfishing, pollution and eutrophication. It is widely accepted that anthropogenic CO2-emissions are the main cause behind the acceleration of global warming, although there is still some controversy. Ice core drillings have revealed that our planet has seen dramatic climate changes before1, along with increased temperatures and atmospheric CO2 concentrations. It is common knowledge that elevated sea surface temperatures may cause coral bleaching. That an increase in atmospheric CO2 could be just as threatening, is not. The CO2 equilibrium Today, the planet's CO2 concentration is roughly 385 parts per million (ppm), although this value fluctuates (fig.1). This fluctuation is caused by the fact that the majority of the earth's vegetation grows on the northern hemisphere, resulting in a higher total photosynthesis during our summer. During the fall on the northern hemisphere, the CO2 level rises gradually.  Figure 1: Monthly mean CO2 concentrations in ppm as measured at Mauna Loa, Hawaii, at approx. 11,000 feet (3400m). Cycles in the graph can be clearly seen, caused by the summer to winter switch on the northern hemisphere (Courtesy of the National Oceanic and Atmospheric Administration, www.noaa.gov). These fluctuations occur in our oceans as well, given the fact that our atmosphere is constantly 'dosing' CO2 into the seas. In short, when CO2 levels increase in the atmosphere, so too will they in the oceans. We call this process Henry's Law . As a consequence, the oceans have actually inhibited global warming by taking up vast amounts of CO2. Marine water is a natural buffer, which means that it can be regarded as a solution, able to retain a relatively constant pH value. This ability can be quantified, and it is called alkalinity, which is mainly determined by bicarbonate ions (HCO3-). When CO2 dissolves into marine water, the chemical reaction is this:  The paradox here is that CO2 produces alkalinity, which seems to be beneficial. However, for every bicarbonate ion which is produced, a proton is produced as well. These protons are the acidic atoms which cause a drop in pH level. This counterbalancing is responsible for a phenomenon which we call the law of constant alkalinity2. The acidification of the oceans Oceanic pH value has been measured over time (fig.2), and shows a significant decrease over the years.  Figure 2: a: History and future of atmospheric CO2 using two different climate models, IS92a and S650. Using the worst-case scenario model, IS92a, atmospheric CO2 will double over the next 100 years. b: History and future of oceanic pH levels at various latitudes. A significant decrease in oceanic pH can be expected, even using optimistic models (Modified from Orr et al, Nature, 2005) |