By Meg McConville
“Every year in Australia skin cancers account for around 80% of all newly diagnosed cancers, [and] 95-99% of skin cancers are caused by exposure to the sun4.” Although ultraviolet (UV) radiation is a natural form of light, its high energy easily causes DNA damage.
In the oceans, DNA damage leads to increased mortality rate and decreased photosynthesis of phytoplankton3,5. “Phytoplankton are so numerous that they account for approximately fifty percent of all photosynthesis on earth and fifty percent of the oxygen in the air we breathe2.” These microscopic organisms also contribute greatly to ocean productivity as the basis of most food webs. It is therefore important to understand the effects elevated UV levels can have on phytoplankton populations. Yet, the topic of ultraviolet radiation is often overlooked and consequently under researched.
Most people know the oceans cover seventy percent of the earth’s surface but do not realize that the ocean helps moderate global climate. Megan McConville, a Masters student at UNCW who is currently learning about the effects of UV, explained, “The composition of the atmosphere is largely influenced by the oceans; different gases are continuously passed from ocean to atmosphere and vice versa.” In order to protect our oceans and understand global climate, scientists must study not only vital processes involving the atmosphere and the ocean, but also the sun.
Most of life on earth is dependent on solar radiation. “The different types of radiation are determined by their wavelengths, which effect their energy,” Megan explained. “UV has a smaller wavelength than visible light, or the light we see with our eyes,” she continued. “This means that the small decrease in wavelength causes a larger increase in energy, which makes UV radiation more harmful and is the reason why UV causes skin cancer.”
What does this mean for our oceans? Because oceans cover most of the earth’s surface, UV is more likely to come in contact with seawater than land. The surface waters where UV is most likely to penetrate are also where phytoplankton live. Therefore, increasing UV levels would make phytoplankton more susceptible to DNA damage, increased mortality, and decreased photosynthetic ability3,5.
Phytoplankton have some defensive strategies against elevated UV, such as DNA repair and photo-protective pigments. However, the overall efficiency of such mechanisms is uncertain. Megan added, “If phytoplankton populations die, higher trophic levels that rely on them for food will suffer. And if phytoplankton cannot convert carbon dioxide to oxygen through photosynthesis, carbon dioxide levels will increase.”
Despite the harmful effects of elevated UV levels, the Intergovernmental Panel on Climate Change admit to only a medium understanding of solar irradiance and its effects on global climate1. Megan concluded, “Excess ultraviolet radiation can cause immense damage to phytoplankton on a cellular level, but has the potential to impact global processes.” Therefore, an increased focus on ultraviolet light and its effects on climate change is essential for the future of our oceans and our planet.