About 30 microorganisms are capable of causing large numbers of fish to die, said Wolfgang von Baumgart, a spokesman for Solutions to Avoid Red Tide Inc., an environmental organization with about 200 members. Pfiesteria , and so-called red and brown tides, are the most likely to cause kills like Monday's, he said. Monday's fish kill may also have been caused by low dissolved oxygen levels, he added. While researchers found dissolved oxygen levels near the surface of Pepper Creek to be nearly twice normal, a sign microorganisms are active in the water, the oxygen in water near the creek's bottom was a suffocating 0.6 parts per million, Mr. Williams said. Fish cannot survive without dissolved oxygen, which is taken from the water by feeding microorganisms.
Microorganisms thrive in nutrient-rich water.
The state has tested the water to determine if nutrients played a role in Monday's fish kill, Mr. Williams said. Results are not yet available. State researchers used nets to collect marine animals, including menhaden, spot, weak fish, anchovies and blue crabs, near Pepper Creek Tuesday morning, he said. Among the nearly 200 fish caught, only two had healing scars that may have been the result of lesions, he said. All of the fish caught were alive and healthy.