Red Pigment Protects Against UV Rays

snowy landscape with red pink tinted algae activated by UV rays is seen in sunlight

Biological Strategy

Snow algae

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Image: Karasev Viktor / Shutterstock / Some rights reserved

Protect From Light

Access to sunlight is crucial to living systems because it’s the primary energy source for life. However, too much sunlight in the form of ultraviolet radiation (UV) can cause damage to living tissues. Therefore, living systems have strategies to filter out some or all UV radiation. For example, some plants that live in areas exposed to long periods of direct sunlight have reflective surfaces (such as white hairs or powder) that reflect UV light.

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Protists

Kingdom Protista (“the very first”): slime molds, giant kelp, red and brown algae

Protists are a numerous, diverse group of organisms that, in the simplest definition, are defined by what they are not. Protists are not plants, animals, fungi, or bacteria. Some protists, like Plasmodium, are harmful parasites that cause malaria. While many are small, obscure, and go unnoticed, others are important foodstuffs. The largest protist in the world, giant kelp (Macrocystis pyrifera), is utilized by humans and marine species for food and shelter.

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Snow algae protects against UV damage via a red carotenoid pigment.

Introduction

Snow algae (such as Chlamydomonas nivalis) are fascinating microorganisms that thrive in the freezing and high UV-radiation environments of snowfields and glaciers. These seemingly inhospitable places expose the algae to intense sunlight and harmful UV rays. As a rare source of nutrients in such an extreme environment, the algae are a prized food source for indomitable tardigrades.

Sanguina nivaloides photographed with with a Nikon Eclipse 50i microscope, equipped with a Plan Fluor 40 × 1.3 NA oil objective at Deheyn Lab, Scripps Institution of Oceanography.

The Strategy

Snow algae have developed a unique strategy to protect themselves from the harmful effects of UV radiation. They produce a red known as astaxanthin, which acts as a sunscreen for the algae. This pigment gives the algae its distinctive red coloration and is often associated with the phenomenon called “watermelon snow.”

Astaxanthin absorbs harmful UV rays, shielding the sensitive internal structures of the algae from potential damage. This red pigment is present in a lipid droplet that surrounds the , where takes place. By absorbing UV rays, the pigment allows the algae to survive and even thrive in its extreme habitat.

The is crucial for the snow algae’s survival in high UV environments. UV radiation can cause severe damage to cellular structures and DNA, but the astaxanthin acts as a natural sunscreen, preventing such harm. It doesn’t inhibit the algae’s ability to photosynthesize, enabling them to generate energy from sunlight without the risk of UV-induced damage.

The red carotenoid pigment’s ability to absorb UV radiation and transform it into harmless energy demonstrates a sustainable strategy for protection from harmful rays. This method avoids toxic chemicals and works at ambient temperatures, in alignment with nature’s strategies.

The Potential

A harnessing of astaxanthin could lead to technological innovations in fields like cosmetics, pharmaceuticals, and the food industry.

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Last Updated August 31, 2023

References

“Other algae manage to exist in the snow itself. They live in a similar way between the individual flakes just below the surface. Their chlorophyll is masked by a red pigment. This protection against damaging ultra-violet rays is more important for them than for the sandstone algae, for sunlight shines more strongly through snow than it does through quartz. During the summer, the sun is warm enough to cause a slight melting of the surface layers, and this provides the algae with the liquid water they need. Dust, brought by the wind, supplies the necessary minerals. The algae themselves manufacture a kind of anti-freeze which keeps the contents of their bodies liquid even when the temperature of the snow falls to several degrees below zero. During the winter, the tiny cells remain largely invisible some distance below the surface, but when summer comes, they propel themselves with microscopic beating hairs and move up towards the surface, the light and the warmth. So in summer, some parts of the snow fields of both the Arctic and the Antarctic blush pink.” (Attenborough 1995:246-247)

Book

The Private Life of Plants

BBC Books | 21/08/1995 | David Attenborough

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