Texas Fish Kill: Thousands of Dead Fish Along Coast Caused by Low Dissolved Oxygen

Thousands of dead fish along the Texas gulf coast have been reported over the weekend in a case previously thought as mysterious.

Local officials asserted the 'fish kills' event was likely caused by low dissolved oxygen caused by warming ocean temperatures. Other theories point out algae for such oxygen-depriving phenomenon.

Officials have warned residents to stay out of the beach, particularly along the Brazoria County coastline in Texas due to 'increased bacteria levels.' The fish death toll is expected to increase in the coming days.

In the past, similar incidents have been reported in other parts of the world either due to human-induced marine pollution or climate change-driven ocean warming.

Dead Fish Texas Gulf Coast

Texas residents were urged by local authorities to stay out of the coastline following the discovery of a colossal number of dead fish along Brazoria County during the weekend. Now, officials and AccuWeather meteorologists have provided insights as what is behind the mass fish deaths, according to AccuWeather on Tuesday, June 13.

The U.S. weather forecasting company described the number of dead fish in "biblical proportions" as the waters in the Gulf of Mexico was covered with seemingly countless fish carcasses. Authorities linked the cause of deaths due to lack or absence of oxygen in the sea. While assertions have been made, it is still unclear if marine debris or pollution, as well as algae, also contributed to the event.

Probable Causes

The Texas Parks & Wildlife (TPWD) Kills and Spills Team reported "low dissolved oxygen" was behind the swarms of dead fish, citing that both natural and anthropogenic factors could cause the event, in what some people deemed as an ecological disaster.

In terms of human activities, nutrient run-off from agriculture and those coming from treated and untreated sewage waste are major contributors the depletion of oxygen in coastal waters, the International Union for Conservation of Nature (IUCN) says.

The IUCN calls such phenomenon as 'ocean deoxygenation' which drives the over-enrichment of waters with nutrients. According to the organization, the world's oxygen content in the ocean has decreased by approximately 2% since the mid-20^th century. It adds the amount of ocean waters depleted of oxygen has quadrupled since the 1960s.

Meanwhile, the low dissolved oxygen can also be caused excessive algae growth due to the presence of phosphorus, as well as nitrogen. Dissolved oxygen is consumed when algae die and decompose, according to the Minnesota Pollution Control Agency.

Fish Kill Events

Fish kill events and other deaths of marine animals have been linked to various environmental factors, in addition to anthropogenic causes.

In Australia, a related event caused the deaths of millions of fish in the lower Darlin-Baaka River near Menindee. This succeeded an earlier incident in the same area in 2019 when a million fish died due to drought conditions, according to The Guardian.