Matt has found a book on various marine zones. A picture illustrates a zone that shows diffused penetration of sunlight in water, but no marine plants. There are a few marine fish though. Which zone is illustrated?

the mesopelagic, dysphotic, or twilight zone

Explanation:

Marine zones are the divisions of the ocean. The ocean is divided into two basic parts; the pelagic or open ocean, and the benthic or sea floor.

The pelagic zone is further divided into five broad zones according to how far down sunlight penetrates and they are:

1) the epipelagic, euphotic, or sunlit zone: the top layer of the ocean where enough sunlight penetrates for plants to carry on photosynthesis.

2) the mesopelagic, dysphotic, or twilight zone: a dim zone where some light penetrates, but not enough for plants to grow.

3) the bathypelagic, aphotic, or midnight zone: the deep ocean layer where no light penetrates.

4) the abyssal zone: the pitch-black bottom layer of the ocean; the water here is almost freezing and its pressure is immense.

5) the hadal zone: the waters found in the ocean's deepest trenches.

h let me think

dynamic equilibrium is the answer.