WHAT MAKES
THE COLORS OF THE SEA?

Read this paragraph
and put the verbs in brackets
in the SIMPLE PRESENT.

To the human senses, the most obvious patterning of the surface water is indicated by color. The deep blue water of the open sea far from land is the color of emptiness and barrenness; the green water of the coastal areas with all its varying hues, (be) the color of life.
The sea is blue because the sunlight is reflected back to our eyes from the water molecules or from very minuscule particles suspended in the sea. In the journey of the light rays into deep water all the red rays and most of the yellow rays of the spectrum have been absorbed, so when the light (return) to our eyes it is chiefly the cool blue rays we (see).

Where the water is rich in plankton, it (lose) the glassy transparency that (permit) this deep penetration of the light rays. The yellow, brown and green hues of the coastal waters (be) derived from the minute algae, and other microorganisms, so abundant there.

Seasonal abundance of certain forms containing reddish or brown pigments may cause the "red water" known from ancient times in many parts of the world, and so common (be) that condition in enclosed waters they (owe) their names to it - the Red Sea and the Vermilion Sea are examples. The colors of the sea (be) only indirect signs of the presence or absence of conditions needed to support the surface life. Other zones, invisible to the eye, are the ones that largely (determine) where marine creatures may live.