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Monitoring and Studying Harmful Algae

Efforts continue to track and understand harmful algal blooms

Image of dead fish in Florida from red tide of 2018, credit Meaghan Faletti/USF
Courtesy of USF College of Marine Science/Meaghan Faletti

Red tides may be called a “bloom,” but their similarities with flowers mostly end there. Red tides are harmful algal blooms that do much more damage than coloring the water. This phenomenon requires the work of many groups, including NOAA, to monitor and study.

Harmful algal blooms (HAB) are the proliferation of algae that occurs when coastal conditions are conducive to rapid growth. Scientists continue to study why HABs occur, but water temperature, wind, agricultural runoff, extreme weather events, and other factors can contribute to their development. Every U.S. coastal and Great Lakes state experiences HABs. Depending on the type of algae, blooms can be any number of colors or be colorless. The common culprit in the Gulf of Mexico is known for its red tinge.

The Gulf Culprit: Karenia brevis

The harmful Karenia brevis algae are common in the Gulf of Mexico, occurring nearly every year along the Gulf coast of Florida and with increasing frequency along the coast of Texas. Commonly called red tides, the blooms get their name from the cloudy red or rust-colored swaths caused by Karenia brevis growing in overabundance.

HABs in the Gulf of Mexico arise more often between August and October and end between December and February, but events have lasted longer, some for more than a year. The intensity and the extent of the area impacted by a bloom can also vary significantly, although HABs typically impact a small section of water for a short period. However, recent blooms have broken previous patterns.

The Gulf of Mexico is not the only area dealing with this serious coastal hazard. HABs have been reported in every U.S. coastal state, and their occurrence may be on the rise. The impact of a HAB event can adversely affect the environment, the health of humans and marine life, and the economy. HABs can contaminate water and shellfish, deter fishing and tourism, kill marine life, and make humans sick. Though rare, some human deaths have been attributed to HABs.

Monitoring Red Tides

NCEI receives HAB data from partner state agencies and maintains the Harmful Algal BloomS Observing System (HABSOS). The HABSOS website disseminates information and maps of the Gulf of Mexico to give environmental managers, scientists, and the public a data-driven resource for HAB events. NOAA National Ocean Service also provides official forecasts for Gulf of Mexico coastal communities as they respond to red tide. NOAA issues Conditions Reports and Bulletins for southwest and eastern Florida, northwest Florida to Louisiana, and Texas.

Forecasts rely on satellite imagery, field observations, models, public health reports, and buoy data to provide the data required. Many stakeholders—from partner agencies and numerous organizations—contribute to monitoring the Gulf of Mexico and the Great Lakes region. They participate in the national HAB Operational Forecast System (OFS), an ongoing project that depends on many contributors’ dedication, energy, and feedback. Several NOAA organizations support the effort, including the National Weather Service, the National Data Buoy Center, and CoastWatch.

NCEI archives collected data as part of HABSOS with data as far back as 1953. Historical data can be used to determine geographical areas affected, movement of red tide from offshore to inshore, and movement alongshore. In some cases, red tide data are combined with other observations, such as salinity, temperature, winds, currents, hurricane paths, and even mortalities and morbidities of aquatic organisms, to look for patterns.

The Florida Fish and Wildlife Conservation Commission provides data to HABSOS and maintains one of the longest records of blooms in its HAB Monitoring Database. In Florida, blooms form more frequently offshore of the southwest coast of Florida between Tampa Bay and Naples. Occasionally, a harmful algal bloom that forms offshore the west coast of Florida can be transported to the east coast by ocean currents.