Effect of Red Tide on Sea Turtles

Tommy J. Saenz Red Tide on SPI
For the majority of the month of October, red tide plagued the coastline along South Padre Island. Although the deceased fish and shrimp count was been high over the past month, thankfully, due to its limited range and low concentrations, we saw no turtle strandings directly related to the harmful algae bloom.

The effects of red tide are widespread, affecting people, fish, shellfish, marine mammals, and birds. These harmful algae blooms run like a ribbon along the coastline, occurring when colonies of algae grow out of control, producing toxins, and often turning the affected water red. When these masses of algae decompose, oxygen is depleted causing animals to leave the area or die because of the event. Waves can cause these toxins to become airborne, and with the ever-shifting winds on SPI, these toxins can trigger irritation among residents and beachgoers.

Sea turtles appear to be able to detect the harmful algae and subsequently respond by avoiding areas with high concentrations of toxins. Unfortunately, the toxins can remain in the marine environment for months. Due to their diet, some turtles, especially our native Kemp's ridley, have tested positive for toxins during red tide events.

Residents of SPI felt the effects of the red tide with difficulty breathing and eye, nose, and throat irritation. At Sea Turtle, Inc., we closely monitored the beach for turtles exhibiting symptoms, primarily lethargy and upper respiratory issues, caused by the harmful algae but did not encounter any affected turtles. The few deceased turtles that were found were sent to the National Oceanic and Atmospheric Administration (NOAA) for toxicology testing, however, we do not believe the incidents to be related to the red tide.

Thankfully, recent winds and high tides from the remnants of Hurricane Patricia have helped to dissapate the red tide and have drastically reduced concentrations in the area.