Explain why estuaries are very productive ecosystems

Estuaries are very biologically productive. The salinity gradient and the changes in tides, fresh water and accompanying flux in nutrients within estuaries create a variety of habitats that support a diverse food web. ... Because these gradients exist, estuaries are transition zones for many species of wildlife and fish.

Explanation:

Estuaries are very productive ecosystems because they constantly receive fresh nutrients from the river; the pollutants that damage estuaries are the same pollutants that damage other aquatic ecosystems: sewage, industrial waste, and agricultural run off.

the answer is; comparing the frequency of collisions with and without the device

this makes the anti-collision system an independent variable and the collisions a dependent variable. if there are fewer collisions with an anti-collision system that without, then it can be stated that the system is a success. essentially, collisions under an anti-collision system are compared with the frequency of collisions by cars with the human drivers.