I came across this information in passing which struck me as both fascinating and potentially useful. It is that blooms of plankton have been found to increase as a precursory response to earthquakes. The phenomenon is apparent from satellite images of ocean coastal areas close to the epicentres of four recent earthquakes. The blooming of the plankton is thought to be due to increases in chlorophyll, which they use as an essential part of their photosynthetic (light-harvesting) apparatus to provide the energy for them to grow.
It is speculated that the increase in chlorophyll is a result of a rise in temperature of the waters due to a release of heat energy immediately before an earthquake occurs. Concomitantly, there is an upwelling of cold water from the ocean depths, high in nutrients, to the surface. A combination of warmth and nourishment conspires to raise specifically concentrations of chlorophyll-a. It is interesting that one of the two common isomers of chlorophyll should be selected, over the other, namely chlorophyll-b. In nature, the two kinds of chlorophyll have different absorption wavelengths and the overlap of their absorption bands effectively widens the window of energy through which light can be harvested by plants, resulting in a greater photosynthetic efficiency.
As tectonic plates grind together, energy is released, thus thermally coupling the land and the sea and creating suitable conditions to encourage plankton growth. Dr Ramesh Singh, from the Indian Institute of Technology at Kanpur, said:
"I do not think scientists expected such anomalous behaviour of chlorophyll-a. If the epicentre of a quake lies very close to the coast, then anomalous chlorophyll-a concentrations are clearly visible along that coast."
For their study, the researchers chose four earthquakes: Gujarat, India, in 2001; Algeria, in 2002; the Andaman Islands, in 2002; Bam, Iran, in 2003. On the basis of satellite images and measurements of sea-temperatures, they noted a correspondence between peaks in chlorophyll concentration and an impending earthquake.
It is debatable just how much advance warning the method can provide, which seems to depend mainly on the precise distance from the epicentre and also on the ocean depth, but it is argued that the combined measurement of seawater temperature may provide an alternative means to detect an impending quake on those occasions when cloud-cover prevents good satellite measurements being made.