Why are so many dead fish winding up in Newark?

NEWARK, Calif. - Hundreds of dead carp have been turning up in a lake in Newark. 

Visitors to Lakeshore Park have taken pictures of the fish floating on the surface of the man-made lake.

Cassandra Trejo documented the deaths and was concerned as she watched the fish "all gasping for air." 

Preliminary findings from the city of Newark show the fish are dying because of low oxygen levels in the water, exacerbated by the recent heat wave.

The Noble Research Institute points out that warm water physically cannot hold as much dissolved oxygen as cold water. So the maximum potential for dissolved oxygen is lower during the summer than other times of year. 

Second, there are plants growing during the summer that are less abundant during the rest of the year and a byproduct of photosynthesis is oxygen, the institute states. So when the sun is shining, plants put oxygen into the water. But at night, plants use oxygen along with everything else in the water, including fish, which creates a high demand for oxygen at night. 

If the plants and animals use more oxygen during the night than is available, a fish kill occurs. 

Dissolved oxygen levels are highest in the afternoon and lowest right before dawn. A common sight in a pond with low levels of dissolved oxygen is fish piping, which (looks like gulping, at the surface of the water in the early morning. After photosynthesis starts back up, oxygen levels increase and the fish stop piping.

Trejo took video of this "fish piping," right before she took images of the dead fish. 

The Public Works Department said they are adding fresh, oxygenated water to the lake.