We all know what algae is. We see it every summer in our lakes and rivers, whether it be as floating mats, delicate strands, or something to slip on getting into the water. Algae may seem like a nuisance to some, but these microorganisms are vitally important. They are at the base of our food web, called primary producers, meaning that they consume nutrients in the water and are then eaten by creatures further up the food chain. If we didn’t have algae, the bottom of our food web would be knocked out and our food web would collapse.
In addition to being important food sources, algae are also able to adapt to changing conditions. Increases in nutrients being introduced to our Bay, from fertilizers, sewage, and a number of other sources, have had a profound effect on the way that algae grows, but also the types of algae that grow. This change to the smallest organisms affects all of us. Let’s take a dive into algae and see what happens on the microscopic level!
Phosphorus and nitrogen, the two most common nutrient pollutants, exist as natural nutrients in aquatic ecosystems and are used in the metabolic processes of most algae, meaning that algae take in these nutrients as fuel for photosynthesis: the process of taking in CO2 and converting it into energy and oxygen.
The more nutrients that are in the system, the faster algae can grow and divide; this rapid growth creates what we call an algal bloom. Since algae are plants and produce oxygen, intuitively we might think that this would be good for the environment, adding more and more oxygen into the water. Unfortunately, that’s not the case.
Algae that grow rapidly also die rapidly. These dead algae sink to the bottom of the lake and are then food for different microbes, which use up oxygen in the process of eating the dead algae. When the amount of oxygen being used up becomes greater than the amount being produced, you end up with a low-oxygen zone – this is where fish and other aquatic creatures run into trouble. If all of the oxygen in an area is used up, you end up with an anoxic zone.
When an anoxic zone is created, that doesn’t necessarily mean that there’s nothing living there. It just means that bacteria and microorganisms that use different nutrients for their fuel, ones like sulphides or iron, which don’t tend to exist in oxygen-rich areas, are able to thrive. Iron, in particular, is an important nutrient to keep track of – this is because cyanobacteria, otherwise known as blue-green algae, needs iron to bloom.
Even though we call it blue-green algae, cyanobacteria is actually a bacteria. It creates its own energy via photosynthesis like plants, and is a very important bacteria for its ability to take nitrogen from the atmosphere, and turn it into a usable nutrient for other creatures. Cyanobacteria is also not just one type of organism – it’s a whole family! Some species aren’t poisonous to us; in fact, some are incredibly beneficial! An example is the species spirulina, which is used as a health food.
Unfortunately, there are species that, when they grow in abundance, can be harmful to humans and the environment. The toxins produced by these cyanobacteria are called cyanotoxins, and they affect what’s called our regulatory enzymes, stopping them from working. These regulatory enzymes control cell death, and severe exposure to cyanotoxins can lead to liver damage, heart failure, and even death. However, these toxins take time to build up in our system, and proper safety precautions and reporting of blue-green algae blooms can keep us all safe. Check out our blog post https://www.stateofthebay.ca/a-closer-look-at-algae/ for more information!
Even though we can’t see them, the microbes in our rivers and lakes are incredibly important. They make nutrients, provide food for other creatures, and small changes to them can affect an entire ecosystem. It may take a microscope to see most of them, but paying more attention to algae, bacteria, and the hundreds of other tiny creatures in our waters helps understand the world around us that much better.
Sarah Vokey is a Science Communication Summer Intern at the GBBR. A native of Sudbury, Ontario, Sarah has a fierce love for the natural beauty of Georgian Bay, and is thrilled to be working with the GBBR. You can reach Sarah at [email protected]