AccuWeather.com has examined some of the past incidents of "Red Tide," and most recently the situation along the Maine coast during July 2009. While the direct cause of the phenomena is specific micro-organisms or algal blooms, we offer some insight to the weather that may affect red tides periodically impacting swimming and the fishing and shellfish industry.
Red tides have been documented since the era of exploration of the Americas. It is the toxin produced by these various forms of algae that can kill fish and poison shellfish.
The organism causing a particular red tide in one geographic area is typically different from, say, the organism causing a red tide on another part of the globe. So too, the weather that varies from place to place may be more favorable for one troublesome species than the next.
Changes in freshwater coming into the ocean can lead to fluctuations in normal ocean currents, in turn resulting in changes in salinity and local ocean water temperatures. Hurricanes, large non-tropical storms and upwelling are some other weather-related examples that can influence coastal water temperatures and salinity to some extent.
A key player to the blooms throughout the globe appears to be the availability of nutrients to the organisms. The greater the nutrients and the more ideal the water temperature, the greater the chance of a red tide. The most common form of nutrients comes from silt, dust and what may be considered as pollutants.
In the case of the red tide along a portion of the Maine coast this month, excess rain over New England has been washing extra silt into the ocean via streams and rivers. Additionally, while the climate on land may be cooler than average this summer, the rain water washing into the ocean is, in some cases, warmer than the existing ocean water.
Interestingly, we have seen a significant amount of Saharan dust blowing off Africa westward through the tropical Atlantic in recent weeks. While there is no measure of the amount of dust compared to other years, it appears to be the greatest amount in recent memory. This dust is rich in iron. It is possible this could also provide extra nutrients for various other organisms in the tropical Atlantic, Caribbean and areas as far west as the Gulf of Mexico.
We have no control over the storms and seasonal red tide issues. At present, there is no way to predict a red tide. However, careful management of runoff into streams and rivers could help minimize the impact to the shellfish industry and keep more money in your wallet, if you consume clams, oysters and mussels. Think about the amount of fertilizer you are putting on your lawn, or what you dump down the drain because it eventually ends up in the ocean.