Hello explorers, today’s topic of discussion – harmful algal blooms (HAB). Algae seem so harmless, being so small and unnoticeable. Until their numbers increase to such extremity, they change the colour of the water body! One particular phenomenom is called Red Tide, when algal blooms become so massive, the coastal waters are stained red! Professor David mentioned this in class and I remember learning about this in my polytechnic course as well so I decided to write about it for today’s post.

Algae and other smaller organisms depend on phosphorus (P) and nitrogen (N), two important nutrients for growth. When these nutrients are in high supply from sources such as farmlands or any land that use a lot of fertilisers, the algal population has the capacity to grow (NOAA, 2018). The polluted water that enters into the rivers, lakes and seas is a result of over application of fertilisers at a rate much higher than the soil would normally uptake in its natural state. It has been noted too that phosphorous is not as soluble as the nitrates and hence adsorb onto soil particles that get washed into the sea too along with the water during soil erosion (FAO, 2017). That means the seas are getting double the dose of pollution, just in case it was not getting enough. The FAO cites, from their global review of water pollution from agriculture, that crops and livestock contribute the most to excess nutrient pollution; aquaculture does too but about a third less than the other two sources.

Unfortunately these algal blooms do not occur for its aesthetic appeal. Algae in red tides actually produce a toxin, known as brevetoxins, that have been proven to be the cause of demise in fish and make shellfish unsafe for consumption! A review study on the Florida red tide and its effects on human health mentions that the brevetoxins do not have a taste, an odour and are not affected by heat or acidity! Florida red tides are linked to the toxic dinoflagellate, Karenia brevis, a photosynthetic oragnism that produce a natural neurotoxin (brevetoxin) which apparently is potent. Reported effects of the toxin on other bigger animals (manatees, turtles etc) include immune system impairment, DNA damage and a lot more of which I do not have the relevant background to understand.

For us humans, there are two ways in which we could interact with Florida red tide (and not in a good way): eating contaminated seafood and inhaling it. Consuming contaminated seafood could cause what scientists are calling neurotoxic shellfish poisoning (NSP), of which its effects on the human body still has so much capacity for medical research. Not much is known about the subchronic and chronic effects of the disease since it is relatively rare and/or underdetected. Inhalation exposure is no better – a study of healthy nonasthmatic lifeguards found that they had respiratory symptoms after working for 8hours in close vicinity to the Florida red tide (Fleming et al., 2011; original source:Backer et al., 2005b).

Another form of shellfish poisoning, mentioned during lecture, is known as paralytic shellfish poisoning (PSP), which is also caused by eating shellfish contaminated with the dinoflagellate algae. The effects on the human body include paralysis in the chest muscles, nausea and if the concentration of toxins taken in were high, death could incur in 2 hours (Alaska Div of Public Health, 2012).

More research needs to be done on new technologies to detect and treat NSP. Also, if we could tap into new technologies to find a way to collect and treat agricultural runoff before it enters the ocean, perhaps we could lower the rate of their growth

That’s all for today mates!

References:

NOAA, Why do harmful algal blooms occur?, National Ocean Service website. https://oceanservice.noaa.gov/facts/why_habs.html, 25/6/2018.

FAO, Water Pollution from Agriculture: a global review – executive summary. Food and Agricultural Organisation http://www.fao.org/3/a-i7754e.pdf, 2017.

Alaska Division of Publich Health, Paralytic Shellfish Poisoning Fact Sheet, Alaska Dept of Health and Social Services website. http://dhss.alaska.gov/dph/Chronic/Documents/02-Internal/ParalyticShellfishPoisoningFactSheet.pdf, 2012.