Hot, Sour and Breathless: Ocean Under Stress

As part of our project, Joe and I are focusing on the human impact on the planet's oceans. To this end, I found this pdf document through the organization Biological Impacts of Ocean Acidification (BIOACID), sponsored by the German Federal Ministry of Education and Research. It describes the three major anthropogenic stressors the oceans face, which I thought would be right on track with the topic of our project. The document itself is a six page brochure outlining these stressors, including ocean warming, ocean acidification, ocean deoxygenation, and the combined effects of these.

A graphic showing the change in sea temperature
from 1901 to 2014.

Beginning with ocean warming, the document ties this to the increase in greenhouse gases in our atmosphere caused by human activities. The increased temperature of the oceans causes less mixing of nutrient rich and nutrient poor water in the warmer ocean, putting the ecosystems there at risk of starvation. Ocean warming also has an effect on the geographic placement of species, forcing cold water fish near to the point of extinction with enough warming, and putting warm water fish where they've never been before, causing an incredible amount of stress for these fish. Warming also harms calcium based organisms, specifically coral, by stressing them to the point of bleaching, which we've spoken about earlier.

Moving to with ocean acidification. The document explains that this is directly caused by increased carbon dioxide levels in the atmosphere. When carbon dioxide is absorbed into the ocean, it goes through a series of chemical reactions (which I won't explain here because I don't think I could do the science justice) that increase the acidity of the surface seawater. This will cause problems not only for sea creatures and plants, but for humans as well. Decreased pH in the oceans can harm shellfish, like oysters and mussels, by interfering with their young's ability to develop shells, and even dissolve the shells of adult shellfish. This is bad news for the oceans, as it decreases biodiversity, making it even harder for ecosystems to bounce back from disasters. This also directly affects the approximately 3 billion people worldwide who rely on seafood as their primary source of protein, putting their way of life in jeopardy.

Moving on now to ocean deoxygenation. This area is the least studied of the three, being a relatively new discovery on the part of scientists. Deoxygenation is essentially a reduction in the levels of dissolved oxygen in seawater. This is caused by a few things, but it is mainly related to ocean warming, which decreases the ability of the oceans to absorb oxygen and decreases ocean mixing, which limits oxygen to the deep ocean. Deoxygenation can also be caused by nutrient run-off from fertilizers and pesticides. These products contain chemicals that increase the production of algae beyond the point that a body of water can handle. The algae float on top of the water and absorb any oxygen they can in order to survive, essentially suffocating the life below. Many ocean species are very specialized in terms of the oxygen levels they can tolerate, and a drop in oxygen levels can lead to the decrease or even extinction of many ocean dwelling organisms.  

All three of these effects have yet to be truly studied in tandem, but suffice to say that the combination of these would be, and is now, disastrous to the oceans.

That's all for now.

Write to you soon.

Danielle K.