Quite often my choice of subject matter for writing about sustainability, and the health of our oceans and waterways, is triggered by personal experiences. Living onboard for most of the summer, or until the winter chill drives me ashore, is the perfect way to observe what is going on in the natural environment, and to make comparisons from one year to the next.
This summer in the Netherlands has been remarkable for the unusually extended period of dry, warm and sunny weather…No complaints there then!
However, the country now has an official nationwide water shortage due to the ongoing drought and dropping river water levels, with a lot of swimming water declared unsafe due to the presence of toxic algae. A spokesman for the infrastructure ministry said, “We have a special crisis team now assessing what measures need to be taken to cope with increasing occurrences of botulism, fish deaths and blue-green algae.”
Water greener than the grass
My own observations on this situation have been coloured (excuse the pun) by the fact that my boat has been floating in what looks like a thick cabbage soup for the last few months. I can honestly say, that in 20 years of boating on the Netherlands inland waterways, I have never witnessed anything like it. Even the wider fast flowing estuaries have taken on a green hue, and when a fast boat goes by, it leaves a stern wake which glistens bright green in the sunlight!
Two types of unprecedented biological growth have taken over in our marina, which in fairness is very protected by trees on all sides, thus concentrating the sunlight and reducing the air flow across the surface. Coming up from the muddy bottom, a tough, tangly and very fast-growing weed has reached all the way to the surface; this wraps around propellers, rudders and sterndrives, resulting in a few angry skippers!
Then, across the water surface is the thick green algae, which can have an unpleasant smell if you're downwind, and is often seen with dead eels and fish trapped in it.
Some of the causes
I am not qualified to make this a scientific thesis on waterborne biological growth, but some research online has thrown up a few things that I was not fully aware of:
Apart from the obvious effect of increased sunlight and lower water levels, it is also claimed that the water quality in the Netherlands has improved during recent years in many respects. Thus, clearer water allows more sunlight penetration and accelerates the weed growth.
Excessive nutrients are also accelerating the growth of algal blooms, for instance due to run-off from fertilisers on farming land and industrial waste output. Nutrient loads in surface water have hardly decreased since 2005, and this has adverse effects on the diversity and quality of nature. Source: Dutch Ministry of Infrastructure & Environment. (River basin management 2016 - 2021.)
A common type of blue-green algae is finding it easy to adapt to Earth's rising CO2 levels. There are many toxin-producing varieties of blue-green algae, and it seems that they are even more adept at handling changing climatic conditions than scientists previously supposed. Source: Study by team of microbiologists at the University of Amsterdam (UvA) in 2016.
Since I wrote this, we have had a few days of heavy rain and strong n.westerly winds, which has broken up and dispersed a lot of the floating algae. Proof that nature always fights back, but sadly too late to avoid a lot of damage to the eco system and marine life!