By Elsabé Brits
Healthy oceans, from coastal waters to remote high seas and deep seabed areas, are integral to human health, well-being, and survival and vital to our place in the natural world.
We don’t think about the ocean as important to our survival and health until beaches are closed because of sewage spills or we see how much plastic pollutes the seas. But they are vital: covering over 71% of the Earth’s surface, the oceans serve as an essential carbon sink.
According to an article in The Lancet, scientists tend to know more about areas near the coast. Still, it is becoming clear that the deep seas and the high seas – which comprise 64% of the ocean’s surface and nearly 95% of its volume – are equally important for human health and are increasingly affected by global environmental changes.
The deep sea is broadly defined as the ocean depth where light begins to fade, approximately 200m. Ocean waters beyond exclusive economic zones are known as the high seas. They belong to no nation and have thus far never been legally protected. All oceans have an impact on life on Earth.
The high and deep seas harbour rich biodiversity, offering human health benefits such as marine genetic resources (MGR) for pharmaceuticals and biotechnological innovations. Harnessing high-seas biodiversity is gaining momentum as marine organisms show their important medicinal value. The sponge Halichondria okadai is a source of the anticancer drug eribulin, for instance.
A vital part of human lifestyles
But the oceans don’t only serve as a food source for humans and marine life. They are also universally culturally important. It is good for our mental health to walk along the beach, play in the sand with our children, swim: to enjoy the ocean and the life it provides to us.
I am naturally averse to the cold; I like to swim in warmer water. I moved to Cape Town in 1999, and I cannot tolerate the cold water even on the hottest day. From Plettenberg Bay East, I can enjoy myself. The warmer the water, the better. Yet, many people swim in Cape Town’s cold water, an increasingly popular activity. The water temperature is between 12°C and 16°C, so not as cold as the north, but still.
The swimmers say they feel wonderful after swimming in what I deem as icy water, even though I admit it does not qualify as true ice swimming.
Immersion in cold water has long been known to majorly impact the body and trigger a shock response such as an elevated heart rate. Some studies prove that cardiovascular risk factors are improved in swimmers adapting to the cold. However, other studies suggest the workload on the heart is still increased.
The Arctic University of Norway reviewed 104 papers on cold-water swimming, where people swam in water colder than 20°C and without wet suits. The review provided insights into positive links between cold water swimming and brown adipose tissue (BAT), a type of ‘good’ body fat activated by cold. Unlike ‘bad’ white fat, which stores energy, BAT burns calories to maintain body temperature.
Cold exposure in water – or air – also appears to increase adiponectin production by adipose tissue. This protein protects against insulin resistance, diabetes and other diseases.
Repeated cold-water immersions during the winter months significantly increased insulin sensitivity and decreased insulin concentrations, according to the review. This was for both inexperienced and experienced swimmers.
Other theories suggest that regular open water swimming also results in a post-swim ‘high’, triggered by the release of beta-endorphins, dopamine and serotonin.
Furthermore, facial immersion in cold water stimulates the vagus nerve, resulting in an anti-inflammatory response. This anti-inflammatory effect may underlie the clinical benefits of vagal nerve stimulation.
According to the authors of the review study, education is also needed on the health risks associated with taking a dip in icy water. These include the consequences of hypothermia and heart and lung issues often related to the shock from the cold. And never do it alone, even if you are an experienced swimmer.
Probably the most intriguing organisms in the sea are those that are tiny. Without them, we would not be able to survive. Next time you swim in either warm or cold water, think about the air you breathe: half of the oxygen production on Earth comes from the ocean.
The microbes in the oceans represent more than two-thirds of the marine biomass, yet very little is known about their health status and how climate change impacts this first critical link in the food chain. Little is really known about the deep and high seas, yet it is affected by our actions.
Most oxygen production is from oceanic plankton – drifting plants, algae, and some bacteria that can photosynthesise. These tiny little creatures all play their important part on this fragile earth, and so must we, interconnected as we are, and dependent on each other for our health and survival.
Views expressed are the writer’s.