Seasonal variation in an annually-banded coral Porites: A scanning electron microscopy investigation

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Seasonal bands of the hard coral Porites sp. collected from three different islands of Lakshadweep (Northwest Indian Ocean) are examined under a scanning electron microscope (SEM). SEM photographs reveal the presence of detrital inclusions in high density bands and their absence in low density bands. It is proposed that during the monsoon season, run-off from the island may bring detrital material that subsequently gets incorporated in coral skeleton. By contrast, calm and dry conditions prevailing during the non-monsoon period preclude such incorporation due to non-availability of detrital material in the water column. In addition to the inclusions of detrital material, the presence of low-Mg calcite and carbonate cementation in seasonal bands are also observed.