The reef at sunset

When the light fades, many parrotfish look for a place to rest. Some make a soft coat of mucus around themselves for the night. Squirrelfish are just coming out of hiding to look for food.

One shelter, two visits. Imagine watching a cavity just before sunset and again an hour later. Which animals went in? Which came out?
Day–night diagram: zooplankton deeper by day and near the surface by night.
Some small animals rise in the evening and descend in the morning. © dive.explo360.fr — All rights reserved. Reproduction requires permission.

A journey towards the surface

Some of the tiny animals we call plankton spend the day deep in the water. In the evening, they swim up to find food.

A meal carried into deep water

Near the surface, some plankton animals eat tiny algae. They take some of that meal with them when they swim back down. If a bigger animal eats them there, part of the meal passes to it.

A copepod swims towards deeper water as particles sink beside it.
Small animals carry their food downwards. Leftover material also sinks through the water. © dive.explo360.fr — All rights reserved. Reproduction requires permission.

Hunters follow their prey

Follow a copepod. As it swims up, it leaves dark water, reaches a rich feeding area and may encounter a different set of hunters.

When small prey swim up, fish and squid can follow. In dark water, some prey are harder to see, but other hunters can still find them.

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