As usual, there have been several reports of red tide along Southwest Florida’s coastline this year. This harmful algal bloom, known as Karenia brevis, is a higher than normal concentration of microscopic plant-like organisms which can turn the water a reddish or brown hue. The toxins found in this bloom can affect the central nervous system of fish and other animals and can cause disorientation and possibly death. In humans, the cells can release toxins in the air causing respiratory irritation. Red tide is nothing new to the area, and has been documented back to the 1700s.
Red tides usually develop about 10 to 40 miles offshore and drift to the coastlines via winds and currents. Since they develop so far out, the answer to the question if red tide is a result of man-made nutrients is a “no.” However, once this algal bloom reaches the coastlines it can use the artificial nutrients to sustain their growth. So red tide is not killing our Gulf waters, but these man-made nutrients are.
As we approach summer, the annual appearance of a “dead zone” has become a fact of life. This happens when a specific area of water does not have enough oxygen for fish to survive. Each year the National Oceanic and Atmospheric Administration (NOAA ) sends a cast of scientists into the Gulf to measure it.
In 2017 the dead zone was the largest ever recorded and covered 8,776 square miles! That’s an area the size of New Jersey. A debate whether state and federal agencies are doing enough to cut pollution entering the Gulf has been going on for more than 30 years. Here, the problem is the use of man-made nutrients.
This “dead zone” is found in our northern Gulf, along the coastlines of Texas, Louisiana and Florida. Scientists knew it would be there because they are aware of the heavy load of nutrient pollution that enters the area waters from the Mississippi River. Most of the nitrogen and phosphorus that drives this problem come from agriculture and as far away as the upper Midwest.
Farmers use the nutrients as fertilizer, which is washed into nearby streams and rivers and then emptied into the mighty Mississippi. As the major tributary meets the Gulf these nutrients unleash blooms of algae which then die and decompose. This now uses up the oxygen in a thick, lower layer of water at the bottom of the Gulf.
Unusually heavy rains in the Midwest prior to last summer’s record breaking dead zone report is probably responsible, as it pushed more “dirty water” down river. Action plans are in place to help reduce the nutrients that reach the Gulf.
A similar problem occurred in the Chesapeake Bay. They also had a “dead zone” problem but, despite fierce objections by farmers, mandatory limits on nutrient pollutants entering the Bay were enforced. Wildlife is now recovering and pollution is way down.
Closer to home, we might reflect on our own Everglades, where nutrients and pollutants are redirected to the east and west coastlines, dumping into the St. Lucie River and the Caloosahatchee.
Are there “dead zones” in Lee and Collier counties? Not yet, but be aware, be very aware, of more serious problems unless we remain vigilant about our own backyard.
Bob is the owner of Stepping Stone Ecotours, conducting educational walks in the western Everglades. He is also a naturalist for a dolphin survey team, on board the Dolphin Explorer. Bob loves his wife very much!