Biosphere Contents

3. Photosynthesis

In aquatic ecosystems, a set of decomposition processes analogous to those for leaf litter on land takes place

In aquatic ecosystems, the percentage of material consumed by herbivores and secondary consumers, which range in size from zooplankton to blue whales, tends to be greater than in terrestrial ecosystems. Nevertheless, dead plant and animal material is decomposed by bacteria and dissolved nutrients (ammonia, nitrate and phosphate), dissolved organic matter and particulate organic matter are released into the water column. Where there is sufficient light for photosynthesis, the nutrients can be immediately utilised for new plant growth. However, a certain fraction tends to drop down to deeper layers in the water column where light can no longer reach. In these layers the dissolved nutrients simply accumulate. A further fraction of organic matter reaches the sediment and there it can also decompose. Some of the carbon present is precipitated into the deep oceans as insoluble calcium carbonate. This is an important mechanism for removing carbon dioxide from the atmosphere.

What does decomposition of aquatic organisms entail?