4. The hunt for green snow: chasing the mystery of how snow algae bloom
Over the next few weeks spring will begin its slow creep up the mountains, arriving in the high alpine by late summer. The arrival of spring to an alpine region can be marked by the appearance of coloured snow, sometimes bright red ‘watermelon snow’, other times a more subtle pink, orange or green tinge that is easy to miss.
Many different things, including mineral deposits and animal waste can colour snow. One of the most striking is Penguin poo, coloured by the abundant carotenoids in the birds’ krill diet. Blooms of snow algae are the predominant cause of coloured snow in our local mountains. But what exactly is a bloom of snow algae?
Snow algae are unicellular organisms. When conditions are good (liquid water, sunlight and nutrients) the individual cells grow in volume until big enough to divide into two cells. We don’t yet know how fast snow algae grow and divide, but their temperate cousins divide up to four times in a day. One cell becomes two, two become four, four eight and eight sixteen. Thus in a single day, the population grows sixteen-fold. After four days of optimal growth, one cell has become 65,536 cells. It is easy to understand how a pond can turn green after a few warm days. But what is happening on the snow?
One of the enigmas of snow algae is that both in the lab and in field samples, we and others have only managed to catch green cells dividing. Do green cells proliferate and then turn red after the population has exploded? Or do red cells divide so quickly that they are less likely to be caught in the act of division? Or are the red cells undergoing a unique process of division that happens underneath their shield of fatty red pigment? Are the green cells and red cells different stages of the same species, or are they different species? While we are addressing some of these questions in the lab, we are keen to see whether our crack team of citizen scientists can find any blooms of green snow algae as they follow spring up the mountains in the upcoming backcountry season.
Follow the BC Snow Algae Project at Snow Algae Reports.