The sun shining on a tidal pool during a hot day heats the water. as some water evaporates, the pool becomes saltier, causing _____. the sun shining on a tidal pool during a hot day heats the water. as some water evaporates, the pool becomes saltier, causing _____. a decrease in the water's density a decrease in its oxygen content an increase in its ability to sustain aerobic organisms an increase in its carbon dioxide content