Lake comes alive with bizarre tiny creatures at night

This is a remote lake in Northern Ontario, but it's much like any other lake in cottage country North America. During the day, the water is clear and clean and there is no sign of tiny creatures that are shown in this video. At night, shining a flashlight on the water will bring a swarm of tiny animals that too small to see clearly. As a group, they fill the water like a black cloud of rapidly swirling organisms.

Investigation reveals that these are spiny water fleas, small and ferocious creatures that consume enormous amounts of daphnia, the naturally existing animals that are critical to the health of freshwater lakes across the continent. The daphnia consume algae, making the water clear, allowing sunlight to penetrate deeper. The daphnia are also a source of food for small fish and fish larvae. The spiny water fleas also consume algae, competing with the daphnia. However, the spiny water flea is an animal that fish larvae cannot consume.

The presence of the spiny water flea is a threat to the daphnia and other organisms that are critical to the balance of the food chain. They negatively impact fish populations, which will also affect other food chains. Because of the spines and hooks on their tails, these water fleas are impossible for the smaller creatures to eat. They grow larger than daphnia and they have stronger and larger mandibles, making them titans of the water flea world. They are capable of completely eradication some species of zooplankton in a lake. Zooplankton are the backbone of the food chain.

It is believed that the spiny water flea was brought to North America in ballast water of cargo ships prior to the 1980s. As recreational fishing increases in popularity, further spread of the animals and their eggs is taking place at an alarming rate. The eggs can survive being dried out in the sun, as well as the digestive tract of fish. The eggs are nearly indestructible and the proliferation of a lake is unavoidable once the spiny water flea takes up residence. Since the arrival of these ferocious little animals, the numbers of other larger species have declined, although the exact correlation is difficult to accurately measure.

An interesting experiment involves shining a light into the water for a minute or more to see what comes to the surface. In many fresh water lakes, it is these invasive spiny water fleas that can be seen.