harmful algae
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Those harmful algae that are destroying our oceans...

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UNESCO publishes the world's first compendium of data on harmful algal blooms, the micro-organisms that deplete fish stocks, destroy fish farms and can carry disease and even cause the death of humans and large marine animals.
Photo: Vast planktonic bloom off the coast of Brittany, seen from space (more than 20 000 km2) ©NASA

 
Dn a case-by-case review of harmful algal bloom data (harmful algal blooms, HAB)This book sounds the alarm: this phenomenon is tending to develop, as has been observed, for example, along the coast of Florida (United States), where data have been recorded since the mid-19th century, as well as in India and Oman. In the Adriatic and Baltic regions, harmful algal incidents are increasing despite government awareness and decisions to limit the production and release of phosphate and other toxic chemicals.
 
This phenomenon may be natural or encouraged by terrigenous pollution, which leads to intense and long-lasting proliferations that can lead to "dead zones" due to the consumption of all the oxygen dissolved in the water at night and/or the emission of toxins by certain species of plankton: They greatly destructure and impoverish the food chain due to a high night-time consumption of dissolved oxygen and/or by the production and emission into the environment of ecotoxic molecules.
Their annual cost has been estimated to be between $2.2 and $4.6 billion per year for the United States alone and only for freshwater blooms according to a study by Dodds et al. (2009). (1).
Harmful algal blooms grow rapidly due to the scarcity of oxygen in the water and block the sunlight that many marine plants and animals need. Harmful algal blooms can be green, brown or even orange-red in colour.
Some harmful algal blooms release toxins as they grow, which can harm other species and create public health hazards for humans. Cyanobacteria, in particular, produce toxins and taint drinking water, lakes and oceans. Swimming in drinking water or water tainted with cyanobacteria can cause stomach flu, skin irritation and even liver damage.
But these harmful marine algae can harm or kill fish and other marine animals. If humans eat these contaminated fish, they may have neurological symptoms. And if the toxins are inhaled, some people suffer asthma attacks.

 
"Harmful and toxic microalgae of the world ocean"... (Intergovernmental Oceanographic Commission Guides and Manuals No. 68, 523 pages), written by marine biologists and chemists Patrick Lassus, Nicolas Chomérat, Philipp Hess and Elizabeth Nézan, examines trends in the proliferation of these toxic marine micro-organisms and assesses policies to limit their spread.
 
The increase in HABs is closely linked to the intensive exploitation of coastal areas through aquaculture, tourism and other human activities, which brings people and resources into contact with toxic microalgae. These activities promote the development of HABs due to excess nutrients from human waste and chemicals, overfishing and increased shipping traffic. 
 
Some observations are more encouraging. Decreases have been observed where measures have been taken to improve wastewater treatment and fish farming technologies. The Seto Inland Sea in Japan, where a HAB monitoring programme has been in place for 50 years, is an example. HAB incidents in Seto have stabilized at around 100 per year, thanks to national regulations to control nutrient and waste discharges.
In many European countries (2)In the case of the HABs, reductions in HABs are primarily due to management measures based on regular observations and early warnings. Thanks to European legislation adopted in 1991, these countries implemented effective monitoring after serious cases of intoxication in the 1980s.
 
This UNESCO monograph presents data identifying 174 algae and 100 toxin-producing species grouped in 24 different chemical classes for 11 different human pathologies. Some 50 photos show 62 species. The authors hope that this publication will stimulate research and the identification of new species.
Available in English and French, this publication is intended for a wide audience, including fish and shellfish farmers, monitoring agencies and scientists.
This book is a joint publication of the Intergovernmental Oceanographic Commission of UNESCO and the International Society for the Study of Harmful Algae. It has received support from the Prince Albert II of Monaco Foundation and several regional, national and international bodies.

What solutions?

In cases where the inputs are terrigenous and agricultural, urban and industrial, the aim will be to eliminate discharges of polluted water into the sea, to reduce nitrate and phosphate discharges at source and to build treatment plants and/or natural lagoon systems capable of treating these discharges before discharging the water into the natural environment.
 
The fight against soil erosion and a policy of de-eutrophication of surface waters, renaturation of banks (tree roots fix the banks and take nitrates directly from the water), strategies to combat flash floods (source of turbidity and nitrate transfers) can be assisted by ecological engineering (e.g. laying fascine, creation of renatured buffer basins, or reintroduction of beavers which, through their dams, regulate the flow of certain rivers...). These measures can help make runoff water cleaner from the source to the estuary. (Source Wikipedia).
 
Restoring natural and healthy populations of filter-feeding organisms (corals, sponges, bivalves and other filter feeders, etc.) can also contribute to good water ecological status.

Source : Unesco - Digital Library, 2015
 
 
(1)    Dodds, W.K., Bouska, W.W., Eitzmann, J.L., Pilger, T.J., Pitts, K.L., Riley, A.J., Schloesser, J.T., Thornbrugh, D.J. (2009) Eutrophication of U.S. freshwaters: analysis of potential economic damages. Environ. Technol Sci 43, 12-19
(2) Denmark, France, Germany, Ireland, Norway, Spain, Sweden, United Kingdom.

 
 

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