Chesapeake Bay Coastal Bays Rivers and Streams Watersheds
Maryland Department of Natural Resources

Frequently Asked Questions about Harmful Algae Blooms, HABs.

View current map of key species (Microcystis sp., Prorocentrum minimum and Karlodium veneficum).

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What are harmful algae?
Algae are a natural and critical part of our Chesapeake and Coastal Bays ecosystems.  Algae, like land plants, capture the sun’s energy and support the food web that leads to fish and shellfish.  They occur in a size range from tiny microscopic cells floating in the water column (phytoplankton) to large mats of visible “macroalgae” that grow on bottom sediments.

Algae may become harmful if they occur in an unnaturally high abundance or if they produce a toxin.  A high abundance of algae can block sunlight to underwater bay grasses, consume oxygen in the water leading to fish kills, produce surface scum and odors, and interfere with the feeding of shellfish and other organisms that filter water to obtain their food.  Some algal species can also produce chemicals that are toxic to humans and aquatic life.  Fortunately, of the more than 700 species of algae in Chesapeake Bay, less than 2% of them are believed to have the ability to produce toxic substances.

Who do I contact to report a harmful algal bloom?
To report harmful algal blooms, please call the Department of Natural Resources, Tidewater Ecosystem Assessment Division at (410) 260-8630 during normal business hours. If there are fish kills, fish health, or human health concerns associated with the observed algal bloom, please contact the Fish Health Hotline at (877) 224-7229 at any time.

How have Harmful Algae affected Maryland?
There are a number of algal species that have caused problems in Maryland for many years and others that have only been recognized recently. For example, there have been long standing problems with algal overabundance in Marylandís Chesapeake and Coastal Bays, especially in some of the tidal tributaries, due to nutrient over-enrichment and subsequent blooms of numerous species of algae.

Economic losses from the effects of HABs may affect the commercial fishing industry, tourism, cultural traditions, recreational and subsistence harvests. During 1997 in Maryland across all seafood industry segments, instead of continuing a pace of a 7.4% gain over 1996, 1997 sales for all industry segments combined had declined by over 10% (Maryland Sea Grant). Lost sales volume was estimated at $43 million due to Pfiesteria panic with estimated sales without Pfiesteria panic of $253 million in the State. Additionally, a medical team found neurological problems in persons exposed to localized toxic outbreaks of Pfiesteria in Maryland during 1997.

Maryland has experienced severe Mahogany tides due to blooms of Prorocentrum, most notably in 2000. The widely distributed and significant bloom levels resulted in some reduced growth and mortality of hatchery shellfish and reduced seagrass bed distribution within bloom regions. Indirect effects of such a bloom often lead to low dissolved oxygen that can affect a broad array of living resources; several fish and shellfish kills were evident in the bloom region under such 2000 bloom conditions.

The blue-green algae Microcystis aeruginosa also had significant blooms in the summer of 2000 in Chesapeake Bay. Algal bloom samples tested toxic and resulted in temporary, precautionary beach closures in the upper Bay. A bloom of Dinophysis acuminata was detected in the Potomac River during the winter 2001 and resulted in a temporary closure of shellfish waters. The shellfish waters were reopened as toxin levels in oysters were found to be below threshold levels by the U.S. Food and Drug Administration. The Coastal Bays experienced macroalgae blooms that concerned citizens about their effects on boating, Pfiesteria and Brown tide blooms occurred, and potentially toxic species of Chattonella, Fibrocapsa and Heterosigma were identified in the region for the first time between 2000 and 2002.

What is Maryland doing to monitor for the occurrence of harmful algal blooms (HABs)?
Maryland DNR operates a longstanding comprehensive Chesapeake Bay Monitoring Program that includes the regular measurement of algae. A similar program is now being implemented for the Coastal Bays. Both of these programs provide a “safety net” to insure that major HABs are identified and appropriate actions taken which can include anything from providing the public with general information about what is happening to following up with public health officials to protect human health.

These programs alone are not sufficient to track all HABs or their impacts because of the lack of monitoring stations in many areas and the need for special techniques to identify HABs and their toxins. Localized monitoring has been put in place in areas where potential HABs such as Chattonella, Heterosigma, Brown Tide or Pfiesteria have been found to reoccur during monitoring. In 2003, a shallow-water monitoring program linked with nearshore continuous monitoring network will further enhance our abilities to follow HABs and their effects on the Bays. Citizens have participated in monitoring by reporting on obvious water discolorations, odors, fish disease events and fish kills to the Fish Health Hotline (877) 224-7229 which prompts further investigations into algal species present and conditions related to the report.

What is Maryland doing to reduce the likelihood of HABs in the future?
In addition to monitoring, Maryland is working with researchers to determine the factors that initiate and maintain bloom events. Many of these HABs are related to nutrient enrichment. Management actions are being addressed to reduce nutrient inputs in meeting new Chesapeake 2000 goals for improving water quality conditions including the reduction of HAB events. In the Chesapeake Bay, Tributary Strategy teams are working on regional nutrient management plans in support of the Chesapeake 2000 agreement. In the Coastal Bays, the State is a partner in the MD Coastal Bays Program and is working to help implement nutrient reduction strategies outlined in the Coastal Bays Comprehensive Management Plan.


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