Biologists from the Louisiana Fish & Wildlife Department have determined that a massive fish kill that occurred in the mouth of the Mississippi River -- that resulted in grisly pictures like the one above ricocheting around the web -- was not caused by the BP spill. So what was to blame?Low tide and high temperatures were the true culprit, according to the state's report. The combination of the two lead to low oxygen levels that suffocated the thousands of fish. The Associated Press reports:
Department biologists found the fish kill in Bayou Chaland had nothing to do with the Gulf of Mexico oil spill, Olivia Watkins (a spokesperson for the Louisiana F&W; Dept.) said. Watkins said the area is bounded on one side by a rock dam, with a shallow pass to the Gulf of Mexico on the other.After the fish kills were first discovered, there were concerns that the chemical dispersents dumped in large quantities into the Gulf may have played a role, or that the microbes busy breaking down the oil in the water may have usurped the oxygen and created a dead zone. These fears, according to the state's report, appear unfounded.
"When the tide is low, it becomes a pool," she said. "We had a low tide and all the fish got trapped" in water less than 2 feet deep. Hot water holds less oxygen than cold water, and heat speeds metabolisms so plants and animals need more oxygen. The fish suffocated because the water held too little oxygen to keep them alive, Watkins said. Such fish kills are common in Louisiana's shallow waters in late summer and early fall.
But it is worth noting that though the Fish & Wildlife Dept. has ruled this fish kill a result of natural causes, the Gulf of Mexico has a severe problem with marine dead zones, as New Scientist explains: "Summer dead zones are common in the Gulf of Mexico, caused by the large amounts of fertiliser that get flushed down the Mississippi river, which triggers a dramatic drop in the amount of oxygen dissolved in the water."