Water bodies, watersheds and storm water

Algal blooms: Understanding this natural phenomenon

• Introduction
• What is an algal bloom?
• Why do algal blooms appear in the St. Johns River and its tributaries?
• Who is keeping tabs on algal blooms in the St. Johns River?
• Are algal blooms harmful?
• Is it safe to swim or fish in waters containing algae?
• What is being done to eliminate algae from the river?
• What efforts are under way to reduce nutrient pollution in the river?
• What can you do to help reduce nutrients and algae blooms in the St. Johns River?

Introduction

Summer and early fall are the times of year that the St. Johns River typically exhibits its most visible response to water quality problems. Algal blooms on the river can be dramatic and are a result of excess nutrients from fertilizer, wastewater and stormwater runoff, coinciding with lots of sunlight, warm temperatures and a wide, shallow river.

Below are some common questions the District receives whenever algal blooms occur in the river, as well as information on who to contact when a bloom is observed and where to get answers about your concerns.

What is an algal bloom?

Algal blooms are natural phenomenon whose occurrence or intensity may be increased by nutrient pollution. They are caused by algae, which are photosynthetic organisms that occur in most habitats. They vary from small, single-celled forms to complex multi-cellular forms.

In the St. Johns River, bloom forming algae are most often blue-green algae, or “cyanobacteria,” which are structurally similar to bacteria but, like plants, use sunlight to grow. Blue-green algae occur naturally in both freshwater and marine (salt) water bodies. Most live with other types of algae and microscopic animals in floating “plankton.”

An algal bloom is a rapid increase in the population of algae in an aquatic system. Algae can multiply quickly in waterways with an overabundance of nitrogen and phosphorus, particularly when the water is warm and the weather is calm. This proliferation causes “blooms” of algae that turn the water green, often with floating layers of green scum. Some species of algae grow in clumps covered in a gelatinous coating and have the capability to control their buoyancy, allowing algae to stick together into large surface scums in calm weather. Others form thick mats that float on or just below the surface along the shoreline of the river.

Why do algal blooms appear in the St. Johns River and its tributaries?

The pollution causing the most harm to the river is often referred to as nutrient pollution. It comes from an overabundance of nitrogen and phosphorus entering the waterway from homes, yards, farm fields, cars, urban areas and the production of goods.

Water in the St. Johns River took on a sickly green tint during the summer and fall of 2005 as algae fed on an abundance of nutrients in the water. Here, docks on the east side of the river at Mandarin reach into the bloom.

Photo by Bill Yates
(used by permission)

When too much nitrogen and phosphorus are introduced into a waterway, increases in their concentrations may trigger algal blooms.

Nitrogen and phosphorus themselves occur naturally, but an overabundance can cause significant imbalances in the river’s ecology, which can cause blooms.

It should also be noted that masses of algae are often observed in stormwater ponds during Florida’s warmer seasons. Stormwater facilities are designed to capture polluted runoff before it gets in natural water bodies. The ponds help filter out nutrients and sediments collected by storm water as it runs over the earth’s surface before pollutants can reach fragile waterways. Stormwater ponds serve an important environmental purpose — they exist to treat pollutants and to hold floodwaters. Unlike natural waterways, they are not intended for and should not be used for swimming or fishing.

Who is keeping tabs on algal blooms in the St. Johns River?

St. Johns River Water Management District scientists regularly monitor algal growth in the river and routinely collect water and algae samples, particularly during periods when conditions are right for algal proliferation. When an algal bloom is observed and samples are collected, additional tests are conducted to determine if algal toxins are present.

District staff provide results to other agencies, including the Florida Department of Health (which is responsible for sharing the information with county health units), the Florida Department of Environmental Protection and the Florida Fish and Wildlife Conservation Commission.

To alert the District to an algal bloom, please provide your name, phone number and e-mail address, as well as any available information about the location of a current algal bloom, to algae@sjrwmd.com.You may attach photos, and GPS coordinates are welcome, too.

Are algal blooms harmful?

Algae are a natural component of the aquatic food chain and are typically not harmful to people. However, some species may cause harm through the production of toxins or by their accumulated biomass. If the types of algae that produce toxins reach high concentrations (i.e., bloom) due to nutrient enrichment, native aquatic organisms, and perhaps even people, can be affected.

Photo provided by CYPIX
(used by permission)

In the St. Johns River, harmful algal blooms have occurred and been documented in past years, including a dense, widespread bloom occurring in late summer and fall 2005 in the river’s lower basin (that portion between Welaka and Mayport).

When algal blooms block sunlight from reaching underwater plants, an ecosystem can be impacted. As with most plants, sunlight is vital for the growth of aquatic vegetation, which provides food and a place to live and grow for fish and animals. Blooms can last for months at a time, which can harm a waterway’s ecosystem by causing declines in dissolved oxygen, underwater plant growth and fish populations.

In the lower St. Johns River, as algae move downstream from freshwaters into saltier waters, they begin to become stressed and die. Dying algae lower levels of dissolved oxygen in the water, which fish and other aquatic animals breathe. Some fish species with little tolerance for low levels of dissolved oxygen may die. In addition, some algal species can directly lead to fish kills, either by ingestion of algal toxins or by clogging the gills.

While the possibility of algal toxins in the environment is a serious concern, the more common problem associated with harmful algal blooms is the impact recreational activities and commerce due to the unsightly green scum and accompanying unpleasant odor.

Is it safe to swim or fish in waters containing algae?

Some algal species are associated with the production of toxic compounds. However, the District is not a human health agency. Nor does it specialize in wildlife issues.

The District recommends contacting your local health department for direction and advice about human health issues associated with algal blooms. The Florida Department of Health provides links to the Web sites of county health departments across the state.

The Aquatic Toxins Hotline operates a 24-hour, 7-day-a-week, 365 day per year toll-free telephone number — (888) 232-8635 — for use by the public and health professionals. It is staffed by physicians, nurses and pharmacists.

For information about potential impacts to wildlife, contact the Florida Fish and Wildlife Conservation Commission.

Meantime, the World Health Organization (WHO) offers the following guidelines to follow when algal blooms are present:

Photo by Teresa Monson

• Avoid areas with visible algae and/or scums. Direct contact and ingestion are associated with the greatest health risk.
• If no scums are visible, but water shows a strong greenish discoloration such that you cannot see your feet when standing knee deep (after sediment has settled) avoid bathing (swimming), immersion of head, and/or ingestion.
• Avoid waterskiing in visible scums or waters with a strong greenish coloration as described above because of the potentially substantial risk of exposure to aerosols.
• If sailing, sailboarding or undertaking any other activity likely to involve accidental immersion, wear clothing that is loose fitting in the openings. Use of wet suits for water sports may result in greater risk of rashes, as the algal material trapped in the wet suit will be in contact with the skin for longer periods of time.
• After coming ashore, shower or wash to remove algal material.

What is being done to eliminate algae from the river?

It would be detrimental to eliminate “good” algae from the river — algae are an important part of the food web. Plankton is the base of the food chain in open water bodies; algae (phytoplankton) use sunlight to make food and are eaten by microscopic animals (zooplankton). Small fish eat the zooplankton, and larger fish and other large animals eat the small fish.

While some algal species are considered to be mostly a nuisance, certain species are toxic, difficult to eat or are of poor nutritional value for zooplankton. Consequently, zooplankton, particularly types that are the best food for fish, often decline during blooms.

Rather than trying to rid the river of all algae, the District targets its efforts to reduce the amount of pollutants entering the river, which may reduce the occurrence or intensity of harmful algal blooms.

What efforts are under way to reduce nutrient pollution in the river?

In its work to understand where nutrients are coming from, the District has dedicated significant funding to reduce nutrient pollution from entering the river, in partnership with other agencies, local governments and water utilities.

Stormwater runoff, wastewater discharges and agricultural runoff are the major threats to the basins of the St. Johns River. The District and its partners have completed or are pursuing dozens of restoration projects, from the headwaters of the St. Johns River to its mouth, 310 miles to the north.

Ongoing approaches for nutrient reduction include cities and counties addressing urban stormwater pollution and removing treated wastewater discharges from the river. Also, local and state agency partners are working toward reducing bacteria in waterways. Stormwater collection and retention improvements, sanitary sewer collection improvements, repairing or removing malfunctioning septic tanks may help reduce nutrient loading. At the same time, the District is promoting best management practices and building regional stormwater treatment facilities to assist load reduction efforts from agricultural and urban sources.

What can you do to help reduce nutrients and algae blooms in the St. Johns River?

While much is being done by the District and its partners to reduce nutrients in the St. Johns River, much can also be achieved by the public on an individual basis. Learn how you can help.