What happens to the carbon atom during photosynthesis

 the carbon dioxide that is,CO2 is split into carbon and oxygen ,the some of the oxygen is released and the carbon is mixed with water that is H20,if you construct and equation for the reaction between carbon and water you will see that the product is glucose(sugar) 
that is why we say that during photosynthesis plants take in water and carbon dioxide in order to manufacture their food(which is glucose) and to release oxygen

Need a picture to do this

The zone your looking for is the intertidal zone.