At this time of the year, South Florida is often threatened with either blue-green algae or red algae blooms or both, collectively known as harmful algal bloom (HAB). We have been spared the wrath of both so far this year.

Although they are lumped together under HAB, the two are not technically algae. The blue-green organism is a single-cell bacterium called cyanobacteria, whereas the red tide organism is a single-cell dinoflagellate called Karenia brevis (K.brevis). The former has chlorophyll and can synthesize its own food, and the latter has flagella that help it to be mobile and swim around. This misnomer will perhaps be corrected by the scientific community someday.

Between May and June of this year, 330 elephants were reported dead in Botswana, a land-locked country in southern Africa, according to wildlife officials there. The cause of their death has been attributed to the ingestion of cyanobacterial neurotoxins through drinking water from a lake loaded with cyanobacteria (blue-green algae). This news raises a red flag for those of us who live on the islands and get our water supply from Lake Okeechobee, which is laden with cyanobacteria.

The cyanobacteria flourish in polluted water rich in excess phosphorous and nitrogen. The lake has plenty of both. The lake is fed by water from the Kissimmee River from the north that is laden with organic and inorganic nutrients from ranches, farms, and septic tanks along its basin; and, during the wet season, back-pumping of the chemically polluted excess water from the Everglades Agricultural Area (EAA) in the south.

Just a century ago, water flowed down the Kissimmee River into Lake Okeechobee, then south to the Everglades marsh into the flats of Florida Bay. These days, there is very little southerly flow of water from Lake Okeechobee. More than two-thirds of the rainwater that used to flow south into Florida Bay is instead being flushed untreated into the St Lucie estuary on the east and Caloosahatchee River estuary on the west. Unfortunately, these releases devastate the downstream Caloosahatchee River, estuary, and coastal ecosystems by spreading toxic blue-green algae. The excess nutrients fuel the growth of blue-green algae, impacting our drinking water supplies, and making the local beaches unsafe for swimming and fishing. Last week the U.S. Army Corps of Engineers was scheduled to announce discharges from Lake Okeechobee in order to bring down the water level in the lake to protect the Herbert Hoover Dike. Hopefully the discharge will not affect the water quality as the lake is mostly free of blue green algae this year.

Unlike cyanobacteria, the red tide organisms prefer saltwater and do not do well in lower salinity waters. They multiply rapidly in the open ocean and reach epidemic proportions about 10 miles to 40 miles offshore where there are limited nutrients. The high tides or other events bring them to the shore where the toxin is released, wreaking havoc with marine life and human health. The polluted waters along the coast probably have an effect on their multiplication, but more research is needed to determine the impact of nutrients on their multiplication and growth.

From 2017-2019, toxic red tide was a lot in the news because of its severity, long duration, large-scale kill of marine life, respiratory problems in humans, and the financial loss from the decline in tourism.

Dr. Cynthia Heil, director of the Red Tide Institute at Mote Marine Laboratory in Sarasota, has discovered “helper” type saltwater cyanobacteria that show up as a precursor to red tide. This can fix atmospheric nitrogen into digestible food for the red tide in the open ocean.

Both blue-green algae and red tide organisms produce toxins that are harmful to humans and wildlife. The blue-green toxins are called microcystins, and BMAA. The ingestion of microsystins in significant amounts can lead to skin irritations, trigger allergies, vomiting, and even liver failure. People and animals can become sick by drinking or bathing in water contaminated with cyanobacteria. Apparently this is what happened to the elephants in Botswana, as an elephant can drink an average of 50 gallons of water per day.

The ingestion of BMAA can lead to neurological diseases such as Lou Gehrig’s (ALS), Alzheimer’s, and Parkinson’s, as per Howard Simon, a Sanibel resident and the president of the Clean Okeechobee Waters Foundation, and Dr. Walter Bradley, former chairman of the University of Miami’s Department of Neurology.

Red tide produces toxin called brevetoxins. In high concentrations, it affects the central nervous system of fish and other marine wildlife. This toxin also causes fish kills. When there is red tide, one can see dead fish littered on the beaches. In 2018, many dolphins died from red tide poison, and as a result their sightings have become infrequent while boating in the estuaries. Their populations have yet to come back to pre-2018 levels.

More research on HABs is needed to develop polices to mitigate their impact. Considering the seriousness of the problem, researchers at various institutes, such as Mote Laboratory, Florida Gulf Coast University, and Florida Fish and Wildlife Institute are developing technologies to mitigate it. But none of the controls suggested so far, whether biological, chemical, or mechanical, are economically feasible. The only feasible strategy is to maintain a balanced salinity level with a minimum flow level of water from the lake all year around and decreasing the number of high discharge flood control events in the wet season. Also, it is more important that nitrogen and phosphate levels stay within acceptable limits for good estuary health.

Recognizing the problem, Gov. Ron DeSantis reactivated the dormant Blue-Green Algae Task Force in 2019 to prioritize actions and make recommendations to reduce impacts of HABs in Florida waters. Florida legislators incorporated some but not all recommendations of the task force in Senate Bill 712. The governor signed SB712 “The Clean Waterways Act” earlier this year. Professor Mike Parsons, of the FGCU, calls this a good first step in addressing water quality problems, but a lot more needs to be done considering the severity of the problem.

Captiva resident Dr. Suri Sehgal has a long career as a crop scientist, seedsman, entrepreneur and leading expert in the global hybrid seed industry and now operates two nonprofit organizations with his wife, Edda. He is a member of the Captiva Sea Level Rise Committee and chairs the Captiva Island Yacht Club’s Environmental Awareness Committee.

Source: Sanibel Captiva https://www.captivasanibel.com/opinion/

The post Harmful algal blooms: Cyanobacteria, dinoflagellate organisms appeared first on S M Sehgal Foundation.

Those of us who live on islands realize the threat of sea level rise (SLR) to our homes. We also know that a healthy mangrove ecosystem is the first line of defense as they protect coasts against erosion and protect coastal inhabitants against storm surges, high winds, and high tides. For visitors to the islands, mangroves are a striking attraction. We admire their beauty as we peddle through estuaries or visit the Everglades and see how they nurture rich biodiversity.

A mangrove tree has a rich underwater component that harbors a large variety of fish, crab, shrimp, and mollusk species; a surface component and a tangled root system that prevents coastal erosion from storm surges and high tides; and an aerial component that moderates wind flow and serves as a nesting and roosting site for birds. Of the three types of mangroves found in Florida, red mangroves thrive closest to the shore (mostly seaward). Black mangroves grow immediately inland of red mangroves in sites that may periodically be inundated. White mangroves grow inland as well and are found above the high tide line. They range in height from 2 to 10 meters depending upon the species. Defending against storm surges and high tides, mangroves act as a natural barrier, mitigating flooding by reducing wave energy, slowing down storm surges, and providing stabilization. A healthy deep and wide mangrove forest can help significantly in breaking up wave energy and decreasing storm surges, thus protecting property and people. A mangrove forest can considerably reduce wind velocity of hurricane. It is estimated that a healthy forest can reduce the effects of a Category 5 hurricane to a Category 3 hurricane. Further study is required to determine to what extent wind velocity decreases with the health and depth of the mangrove forest. Florida has 469,000 acres of mangrove forest, making it a stable ecosystem of coastal zones. Mangroves are adapted to shallow brackish water and have other special adaptations that allow them to live in sediment with high salinity and low oxygen. If the water becomes too deep or too high in salt content, they can’t survive. Mangroves have coexisted for centuries with the sea level rise. Dr. Erica Ashe, a researcher at Rutgers University, states that SLR has been modest historically (1.2 mm per year) as compared to now (3.4 mm per year), and mangroves have kept up with the SLR and are still growing upward. The SLR rate that has accelerated in recent years is likely to go much higher, causing a concern as to whether mangroves will be able to cope if it goes above 5 mm per year. The threshold for their growth is 7 mm or less per year, according to Dr. Neil Saintilan, a professor at the Macquaire University in Sydney, Australia.

For mangroves to keep pace with rising sea levels, they rely on buildup of organic sediments, according to Jeremy Conrad of the J.N. “Ding” Darling National Wildlife Refuge. Sediment buildup is largely attributed to root growth, decomposition of leaf litter, and deposition of mineral sediments from tides and waves. To maximize the buildup of sediments, the mangrove forest must be healthy, protected, and restored wherever possible. Root production and leaf decomposition rates are altered in stressed mangrove forests, reducing the ability to build up sediments and keep pace with rising sea levels. Eventually, these stressed forests can begin to die off and result in a loss of sediment and the conversion of forest to open water.With projected SLR, the question being asked is if mangroves will move inward if there are no barriers in the way? Or will they simply die off if the water becomes too deep or too acidic? Further study of the entire subject is needed.Mangroves are an excellent carbon sink. Recent studies have found that the sequestration rate of carbon dioxide is several times that of terrestrial plants — as much as four times more than a tropical rainforest. Their ability to absorb carbon dioxide from the atmosphere and store it in their roots and sediment for centuries is sizable and makes mangroves important for mitigating climate change. However, when mangrove trees die, the carbon trapped in their roots and in the sediments is released back into atmosphere creating a new carbon source which has a negative impact on climate.Mangrove forests can play an important role in carbon removals because they are among the most carbon-dense ecosystems in the world, and if kept undisturbed, mangrove forest soils act as long-term carbon sinks.More comparative data on carbon sequestration efficiency of mangroves is essential to make the most of their important role in climate mitigation. We would do well to learn as much as possible about this scientific wonder so that we do not lose this vital coastal relationship.Captiva resident Dr. Suri Sehgal is an India-born American philanthropist with a long career as a crop scientist, seedsman, entrepreneur and leading expert in the global hybrid seed industry. Along with his wife, Edda, he now operates two nonprofit organizations that focus on water security, food security and social justice. He is a member of the Captiva Sea Level Rise Committee and chairs the Captiva Island Yacht Club’s Environmental Awareness Committee.

Source: Sanibel Captiva https://www.captivasanibel.com/2020/09/29/mangroves-the-first-line-of-defense/

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