About Trichodesmium
Trichodesmium is a marine cyanobacteria that occurs in surface waters of tropical and subtropical oceans globally, including the Gulf of Mexico. Capt. Cook described Trichodesmium blooms in the 1700s and larger blooms can be seen from the space shuttle. Sailors sometimes refer to Trichodesmium as sea sawdust, because it forms colonies that can be quite large (up to 1 cm) and is visible to the naked eye. Small blooms resemble sawdust floating on the water surface, while larger blooms can look like oil slicks on the surface or slightly foamy pollution. The amount of Trichodesmium on the surface may vary with time of day, as this species is capable of migrating up and down in the water column. Trichodesmium blooms every year in the Gulf, but generally offshore in oligotrophic waters. Only occasionally do blooms reach nearshore areas in eastern Florida after currents and winds push an established offshore bloom to shore (e.g. May 2000, St. Pete Beach).
Although it can take up NH4, Trichodesmium meets the majority of its nutritional needs by fixing N2 gas and can get most/all of its phosphorus from recycled sources, so Trichodesmium blooms are not related to coastal nutrient sources. High biomass Trichodesmium blooms in the Gulf of Mexico tend to occur in the May-Sept period, because nitrogenase, the enzyme it used to fix N2 has a high iron requirement. Most of the iron it takes up is derived from Saharan dust (high in Fe), which gets blown up into the atmosphere in storms in Africa, then transported across the Atlantic and deposited in the Gulf of Mexico. In general, Trichodesmium is not a good food source for zooplankton or fish and are actively grazed only by a few specialized zooplankton species.
Trichodesmium has a unique “sweet” smell when it decays and large blooms can turn the water red or pink when stressed cells leaks out water soluble, accessory pigments (phycoerythryns). At various times in their development, Trichodesmium blooms can appear brown (healthy bloom), green (blooms in initial decay state after accessory pigments have leached out, making the chlorophyll a visible in cells) or white (after chlorophyll a decays).
Trichodesmium blooms are not harmful to humans, just aesthetically displeasing.
Mote Marine Laboratory has been a leader in marine research since it was founded in 1955. Today, we incorporate public outreach as a key part of our mission. Mote is an independent nonprofit organization and has seven centers for marine research, the public Mote Aquarium and an Education Division specializing in public programs for all ages.
