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Geology LibreTexts

12.8 Sandy / Mudflat

Mudflats (tidal flats) are areas in which coastline shores are separated from the destructive forces of the ocean’s waves.  They are created through the deposit of sediments originating from the oceans and rivers.  These calm environments, also known as estuaries, are commonly susceptible to the ever changing sea levels, otherwise known as the ocean tides, which consists of low and high tides.  During the event of a high tide, sea water level rises to engulf the entire area bringing in nutrients from the oceans.  As the sea water extracts during the low tide, a vast amount of nutrient is left behind making the mudflat a rich feeding ground for a plethora of organisms that it hosts.  The ecosystem that exists within the area heavily revolves around this nutrient delivery system.  The abundance of nutrients make mudflats one of the world’s most productive ecosystems, and as such, produces one of the most diversified range of living organisms. 

The notorious sand bubbler crab is a specie that depends on the mechanism that brings in nutrients from the sea.  They only emerge during periods of low tide, right after the sea water has retreated back into the ocean, to feed.  They sift rapidly through the fine sediments (sand) for food and throw aside the rest in the form of a small ball.  The entire surface of the area in which these crabs inhabit can be covered in these balls just as the high tide is about to come in, to which now the crabs are the ones retreating back underneath the sands.