How Climate Change Wreaks Havoc on Marine Life

Laura Maisvoreva

Location: Zimbabwe

Laura is a medical student studying at the University of Zimbabwe. She is passionate about working towards achieving the United Nations Sustainable Development Goals, particularly Good Health and Well-being, and Life Below Water. She enjoys researching, reading and playing tennis in her free time.

Climate change has become a global threat to many ecosystems, and one such system under stress is the marine ecosystem. The effects of climate change are more noticeable on land, but the effects below water are catastrophic. Some effects include, but are not limited to ocean acidification, increased water temperatures, loss of biodiversity and reduced oxygen supply. These are all the result of increasing global temperatures and if left unchecked, could change what we know of our oceans. This article highlights some key effects of climate change on marine life, illustrating the depth of the issue at hand, and hence why climate change needs to be addressed as a matter of urgency. 

Atmospheric carbon dioxide has increased over the last couple of years, owing to more carbon emissions from factories, vehicles and other sources. Water bodies absorb this gas, which, through some chemical reactions, produces hydrogen ions, which decrease pH [2]. A decrease in pH means an increase in acidity, and acidic water conditions are detrimental to many fish species. Shellfish eaten as a delicacy in some countries are most at risk, such as mussels and oysters, as their shells are prone to degradation [3]. This has an effect on global fisheries too; economies that depend on the fishing industry have felt the impacts of reduced quality quantity of produce. Economic losses due to reduced supply have been felt especially in parts of the United States, where the Dungeness crab generates significant revenue through sales [4]. 

Imagine how many people are impacted by a declining economy reliant on marine species, which, through human activity, are under threat. Nature is an interesting thing, and this is one such example how our activities will come back to hurt us if we do not take the necessary steps to reverse the damage and actively work to build a sustainable world where a mutually beneficial relationship exists between humans and the environment. One can only imagine if we do not work towards reducing atmospheric carbon dioxide to preserve and conserve our oceans; food insecurity will increase, leading to issues that will leave populations with hunger and poverty in the near future. A sad reality exists, however, that efforts to reverse the damage will take years before significant progress in the right direction can be observed [5], which only emphasizes the extent of damage our oceans have sustained. 

Increased Water Temperatures

Ocean warming has been increasing exponentially over the years, with the highest recorded temperatures being just last year [6]. Increased water temperatures are a direct result of global warming, with disastrous effects on marine life. Unfavorable water conditions are an evolutionary problem, as fish are becoming smaller and smaller [7] and are unable to reproduce optimally, because fish are sensitive to even the slightest temperature changes [8].

“Sea turtles are just one of the numerous species at risk of the effects of ocean warming. A report published by the  International Union for Conservation of Nature  stated that increasing water temperatures are affecting sea turtle” breeding; at such temperatures, the probability of producing female offspring is much higher, leading to ‘feminization’ of the species [9]. 

Female hatchlings are less suited for the marine environment, and an increase in female offspring will result in a decline in the species population, a decline which is predicted to decrease by approximately sixty percent in the next 80 years [9]. This shows how ocean warming can lead to mass eradication of marine species. While some will be able to adapt, some may not adapt sufficiently to survive the tragedy, and this is not only a threat to biodiversity, but to fisheries as well, and food security will become a big issue to deal within coastal areas.  

Figure 2: Sea turtle in Mexico [10]

Warmer waters are also less suited to hold oxygen, which also threatens marine wildlife such as tuna that depends on it for respiration and survival. It is said that 700 ocean sites are currently suffering from low oxygen levels [11], and are estimated to decrease by about 4% of dissolved oxygen in 2100 [12]. The plethora of problems associated with climate change are intimately liked and ultimately mean one very important thing – species are under threat and biodiversity is at risk of ‘global homogenization’ [13]. This is a phenomenon that explains how species migration to better water conditions, leaving some areas of the oceans underpopulated and some overpopulated. This would lead to biodiversity loss as species are concentrated in one particular area and other areas are void of marine wildlife. 

Biodiversity Loss

Ultimately, the consequences of ocean acidification, water temperature increase and ocean deoxygenation create an unsuitable environment for marine species to live or breed. Disturbances in the marine ecosystem create an inhabitable ocean space, altering species abundance and distribution [14]. 

Polar bears move around and live in icy areas, and global warming is melting ice caps, causing habitat destruction for these animals, and habitat displacement. Eventually, if all ice caps melt, the inevitable will occur – decimation of populations of species such as walruses, seals and polar bears.  Melted ice also flows into oceans and seas increasing sea water levels, to the detriment of species such as coral that thrive in shallow water [16].  

“Climate change is disrupting the normal balance that exists in the marine ecosystems, harming fish and other wildlife. The state of the ocean at present will only depreciate even further if no action is taken to repair the damage and protect the threatened species. It is evident, through studies, analysis and prediction that in less than a century, what we know of our oceans today will completely change.”

It is hardly an exaggeration to say that human activity is directly impacting marine wildlife and calls to action need to be made to address the issue, in a bid to achieve the United Nations sustainable development goals. Goal 13 (Climate Action) can be achieved by targeting a combination of other goals, ultimately with the hope of helping life below water (Goal 14).