Why is the productivity of ocean ecosystems generally greater in coastal waters compared to the open ocean?

The productivity of ocean ecosystems is generally greater in coastal waters primarily due to greater nutrient availability resulting from processes such as upwelling. Upwelling occurs when deep, nutrient-rich water rises to the surface, bringing essential nutrients like nitrogen and phosphorus to areas where they can support phytoplankton growth, the foundation of marine food webs. This nutrient influx significantly enhances the growth rates of these primary producers, leading to higher overall productivity in coastal ecosystems.

In contrast to the open ocean, where nutrient concentrations can be quite low, coastal regions are more dynamic and are often influenced by factors such as continental shelf interactions, river discharge, and ocean currents, all of which help circulate nutrients. This biological productivity supports a diverse range of marine life, making coastal areas more biologically rich compared to the often oligotrophic (nutrient-poor) regions of the open ocean.