Little Particles, Great Provision

Last month I lived an experience that will remain forever inscribed in my memories. I visited the continent that kisses the one of my origin. I fell ill with a disease commonly known as “Africa’s disease”. I saw colours that rekindled my life. I was in Namibia. I could tell you countless things about this country. I could tell you about the emotions I felt at the sight of the first elephant, I could tell you about the red of the desert in all its most fascinating and variegated shades. I could tell you how far out of the world it is to spend 14 days completely immersed in an extreme environment, feeling more at home than ever before. But I will tell you again how the ocean is capable of allowing the survival of all its living forms. On the first day of passage near the ocean, I remember being enveloped in a smell, finally the fairest one to my nose, that Africa could give me.

I think I still feel it.

But let’s get to the point. Just along the Namibian desert coast one of the usual magic happens that seawater never tires of giving us. I remember that on a day of walking on the beach, I noticed many small yellow spheres, mixed with sand. Driven by curiosity, I asked the guide for what were they. His answer was really vague, but he told me that they were sulfur accumulations.

Coming home, I really knew what it was.

Along the coast of Namibia, there is the presence of a cold current deriving from the Antarctic waters known as the Benguela. The southern winds all year round cause the deviation of the warmest coastal waters, which are replaced by the Benguela current. Here is the phenomenon of rising water from the bottom, the upwelling process, which mixes organisms and organic matter along the water column, breaking homogeneity and generating a high water enrichment.

The upwelling phenomenon is a bit like replenishing the fridge for us, but in this case, it is done constantly. Thus the marine organisms, even of large size, along these coasts have the meal secured because more nutrients imply the growth of primary producers which in turn stimulate that of the secondary ones and so on. All the upwelling areas in the world are characterized by a high biological diversity and this is no less so.

In this area, therefore, we often see large algal blooms. But the blooms also concern the phytoplankton which dies and falls to the bottom after a few days.

At this point the prokaryotic marine component acts – the bacteria, capable of decomposing the algal remains. The first bacteria to act are called sulfur bacteria. These are aerobes and use O2 as an electron acceptor. When conditions become prohibitive for these organisms due to sequential oxygen sequestration, a second class of bacteria acts: sulphate reducing bacteria. These bacteria use sulphates as electron acceptors in anaerobic respiration with the production of hydrogen sulfide.

This product, when it rises along the water column, undergoes a surprising transformation. In fact, in the presence of oxygen, along the coast it passes from being a gas to solid particles of pure sulfur.

Let us not forget that at the same time, hydrogen sulfide is toxic to marine animals and, in high concentrations, can induce fish deaths.

This for me was nothing short of a discovery. A form of production explained through one of the first forms of life. One might think that this is one of the ways in which compounds and nutrients have accumulated on earth even before the existence of eukaryotic life forms. Probably it is one of those mechanisms that has allowed us to generate and preserve life.

How many other things will we still need to understand? How many secrets will the sea still reveal to us? How many things will we still have to see? How many questions will we still have to ask and how many will be answered?

The nature of man is to ask why and there is no better way to leave you with a question mark on the future.

Maria Bruno

Credit: NASA

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