By Dr Bill McGraw Aquaculture and Environmental Scientist
Losses due to toxic algal blooms are reported to be in excess of $82 million to all associated marine industries, not to mention associated illness in humans due to airborne toxins and the consumption of toxic shellfish that have consumed toxic algae. Harmful Algae Blooms (HABs) can result in a wide variety of sea life mortality from fish and plants to manatees and sea lions. Harmful algae blooms are shocking even to observe and I found the recent pictures in the Seven Seas Media article on Florida red tides very disturbing to say the least.
An understanding of how these algae blooms come about can help us in the act of prevention, as there seems to be little anyone can do once the bloom has been created. The exact mechanism of mortality of aquatic life may be a combination of oxygen depletion in water, production of deadly toxins and in some cases irritation to skin and gills which produce excess mucus that interferes with normal respiration.
One factor responsible for an increase in toxic algal growth is a natural, regular upwelling in the ocean bringing nutrient rich bottom water to the surface. However, the development of toxic algae seems to be on the rise both in severity and in the number of areas affected not subject to upwelling. The author remembers shrimp mortality due to observed toxic algae blooms in limited water exchange experimental ponds in Alabama during the late 90s. This memory was prompted by the current overwhelming amount of recent information on the decimation of $800 million worth of salmon in pens due to a toxic algae bloom off the coast of Chile during 2016-2017, where 37 out of 415 farms from the second biggest salmon producer in the world were affected. This amount is estimated to be 20% of the total production.
According to many sources, higher temps of 2-4oC above normal due to a strong el Niño, lack of rainfall and water movement, and lots of sunlight, caused the toxic algae explosion off the coast of Chile. Pseudochattonella verruculosa is the microalgae responsible for the Chile fish kill. It has been identified around Chile salmon farms as far back as 2004. According to article in the journal of Harmful Algae, this algae is “heterokont flagellate”, found as far away as Wellington Harbor in New Zealand. Complicating matters, excess rainfall from an el Niño (la Niña) in other areas can cause HAB as well. The latest information shows that heavy rains from el Niño have caused a massive fish kill from pollution washing in to local waterways.
Along with higher temps (>25oC), both variable light conditions and stable, stagnant, conditions can contribute to an increase in toxic blue green algae. Increases in available elements such as silica, iron and carbon in lesser amounts, have been known possible contributors increasing densities of toxic algae.
Another possible reason for a toxic algae problem is a change in condition and pattern in a marine ecosystem such as slower water circulation, with increase in nutrients such as nitrogen and phosphorous due to a variety of point and non-point sources of pollution. One such source of pollution often cited is agricultural runoff due to excessive use of water soluble, synthetic fertilizers.
Excess phosphorous release can also occur due to anaerobic sediments amplified by stratification in standing water bodies. In contrast to this, when phosphorous levels become low, some common algae such as Karenia brevis, which results in the red tide in the Gulf of Mexico, actually increase the toxins they produce. As soon as the algae run out of nitrogen and phosphorous they weaken and are often destroyed by viruses along with herbivorous planktivores. As more algae decay, this may result in a huge oxygen deficit causing death to most aerobic organisms that can’t get away from the anaerobic zones created.
Other interesting results from studies show that lower pH in some waters actually inhibit the toxicity of some freshwater algae. Although there are about 40 some species of well known harmful algae producing toxins which are created to ward off consumption by ubiquitous, microscopic zooplankton, toxins from algal blooms are eventually broken down by bacteria. Furthermore, harmful Cholera bacteria thrive in zooplankton blooms caused by increase in available algae and as 80% of disease is known to be water born, toxic algae have far reaching effects.
Dr Bill McGraw is a native of Pennsylvania, USA. After having competed two degrees in science from his home state, he went on to finish a Ph.D. in aquaculture in 2000 at Auburn University, and a two year post doctorate fellowship at Harbor Branch Oceanographic Institute of Florida, in 2002. Although he spent most of his time working with commercial aquaculture start-ups in South Africa, Australia, New Zealand and Panama from 2003 onward, he found time to publish over 50 articles in peer reviewed scientific journals, magazines and websites. His research interests range from the study of coral reefs in relation to El Niño and the destruction of coral reef habitat, to zero water exchange aquaculture production systems that incorporate new species and polyculture, utilizing all nutrient inputs. Dr Bill set world records in terms of zero water exchange shrimp production systems, he was the first in the world to grow the Pacific Spiny Lobster (Panuliris gracilis) in a closed aquaculture system at 5 kg/m3 , and the first to document the sea hair, Dolabella auricularia, as the fastest growing aquatic animal known. He is currently very busy with finishing writing a book on mercury toxicity, building a zero water exchange, commercial, multiple species shrimp aquaculture system in Panama, and treating people for chronic disease using Rife technology.
Sources:
- http://oceanservice.noaa.gov/facts/why_habs.html
- https://www.epa.gov/nutrientpollution/harmful-algal-blooms
- http://www.cees.iupui.edu/research/algal-toxicology/bloomfactors
- https://en.wikipedia.org/wiki/Algal_bloom
- http://www.seaweb.org/resources/briefings/algae.php
- http://www1.bio.ku.dk/staff/ndaugbjerg/pdf/2014a_moestrup_et_al_1.pdf
- http://www.theguardian.com/environment/2016/mar/10/chiles-salmon-farms-lose-800m-as-algal-bloom-kills-millions-of-fish
- https://www.sciencedaily.com/releases/2002/11/021118065830.htm
- https://www.sciencedaily.com/releases/2013/03/130312171620.htm
- https://www.sciencedaily.com/releases/2012/12/121220161753.htm