rent general misuse of the term algae will be followed through inclusion of heterotrophic dinoflagellates under the broad umbrella of harmful algae, although they more correctly should be considered as animal-like protozoans.
Harmful algal blooms have received a great deal of attention, but remarkably little is known about them. This discussion first addresses remote sensing techniques for detecting harmful algae, as requested, and then focuses mostly on critical research needs regarding toxic algal species, as opposed to other types of harmful species that cause oxygen deprivation or other undesirable conditions but do not produce toxins.
Various remote sensing techniques are available for detecting certain harmful algal blooms, but their value is limited. Remote sensing has helped scientists to track several types of established surface blooms formed by organisms such as certain cyanobacteria, chrysophytes, and dinoflagellates. For example, the toxic dinoflagellate, Gymnodinium breve, has been forming blooms in Florida waters for more than 100 years, and it also once bloomed in North Carolina's coastal waters during 1987 (Landsberg and Steidinger 1998; Steidinger and others 1998). In the latter case, it was determined retrospectively that this bloom originated from G. breve cells that were transported northward with the Gulf Stream (Steidinger and others 1998). An extremely unusual set of weather conditions allowed small eddies from the Gulf Stream to drift to North Carolina shores basically intact during early autumn. The G. breve inoculum increased enough to contaminate shellfish that concentrated them by filter feeding, thus requiring widespread shellfish harvest closures throughout most of the next winter season. That event caused about $26 million of damage to North Carolina; some fishermen never recovered from the losses they sustained.
The analysis tracking G. breve northward from Florida (through sea surface temperature patterns) was retrospective. That is, the origin of G. breve, once detected in North Carolina waters, was determined belatedly from remote sensing records of temperature patterns from the Gulf Stream. Dense blooms of other toxic algae have also been tracked retrospectively with remote sensing (e.g., Pelaez 1987). However, in general, very little is known about how to prevent blooms, or even to track blooms as they begin to develop. Remote sensing techniques, which would permit design of improved early warning systems for mitigation efforts, are not available to enable detection of initial phases of these blooms. From the perspective of setting early warning systems in motion or mitigating