Endangered monk seals and sea turtles are known to frequent waters off Waikiki but experts say so far there has been no sign the massive sewage spill spreading out from the Ala Wai Canal has affected marine life in the area.

The Department of Land and Natural Resources is planning "a quick survey" next Monday of the shallow reef area on both sides of the canal opening to look for any effects on marine life, department spokesman Clifford Inn said. No one has reported fish die-offs or sick marine animals in connection with the spill, which occurred when the city diverted 48 million gallons of raw sewage into the canal beginning March 24 after a sewer main break.

Bacteria levels in connection with the sewage spill have been a major concern since the death of a Honolulu man from a virulent bacterial infection after a plunge into the Ala Wai Harbor. Because they are mammals, monk seals would be most susceptible to the bacterial infections that afflict humans, said Charles Littnan, a scientist with the National Marine Fisheries Service.

Littnan just finished a two-year study that tracked monk seal movements in Hawai'i. "They do tend to spend a lot of time very near to shore and that puts them in potential contact with sewage spills," particularly in areas such as Kailua Bay and Kewalo Basin that have a history of water quality issues.

"We know that they spend a lot of time in these areas that happen to have sewage spills or overflows but what we don't have from the results of this study is any evidence linking sick seals or seal mortality with a sewage spill event," he said.

That doesn't mean there couldn't be effects from long-term exposure to polluted waters, Littnan said. But with so few seals to study in the main Hawai'i islands and restrictions on research because of the animal's endangered status, more definitive studies on seal health are difficult, he said.

Littnan said he will be submitting the results of his study soon, with the data providing a baseline for future research that could provide a clearer picture of the effects of human activities on seals.

Turtle expert George Balazs with the National Marine Fisheries Service said researchers "have never seen a correlation between sewage spills" and the potentially fatal tumors that have been plaguing sea turtles in Hawai'i. "But that doesn't mean there's no impact," he said.

Runoff containing fertilizer has been more of a concern for marine turtle health, according to Balazs.

Melody Heidel of the Sierra Club's Blue Water Campaign said her group doesn't conduct water quality studies but will be monitoring the response by government agencies to reduce the environmental effects of the sewage spill and prevent further occurrences.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.