All of us here at Our City Forest works with trees and shrubs every day. Today on this blog we will be discussing plants’ closely related friends: Algae! In particular, algaculture.
So what is algaculture? Algaculture is the farming of various algae species. But let’s start with the basics; what even is algae? Algae is defined as “a plant or plantlike organism of any of several phyla, divisions, or classes of chiefly aquatic usually chlorophyll-containing nonvascular organisms of polyphyletic origin that usually include the green, yellow-green, brown, and red algae in the eukaryotes and especially formerly the cyanobacteria in the prokaryotes” (Merriam-Webster Dictionary). Now you may be a bit confused by that definition, and honestly, you should be. Truth be told, there’s a lot of vague blanket terminology used to define algae, and that’s because the taxonomical classifications of algae are still changing all the time!
Basically to sum it all up: algae is similar to a plant, but not actually a plant. The main reason why being that all plants belong to the Kingdom Planate, while all algae does not. In addition, plants are multicellular, vascular, and mostly on land. Algae on the other hand is multi or unicellular, non-vascular, and mostly aquatic. It also belongs to various Kingdoms. Kingdom Plantae includes the chlorophytes and rhodophytes (green and red algae), the Kingdom Chromista contains phaeophytes (brown algae), the Kingdom Protista is home to Euglenophytes (Euglena), and the Kingdom Bacteria is where cyanobacteria (blue green algae) can be found. Plants and algae do have two major characteristics in common though, one being that they are both eukaryotes, and the other being that they are both photosynthetic and therefore contain chlorophyll/chloroplasts.
Taking a moment to dive deeper into the details of algae, two major types emerge: Macroalgae and Microalgae. Macroalgae is large and often multicellular. Common examples include kelp and seaweed.
Pictured: herbarium pressing of Giant Kelp.
Conversely, microalgae is microscopic and unicellular, or in chains / groups. A common example would be phytoplankton.
Pictured: various types of microalgae.
Some of the most popular species used in Algaculture are: Seaweed (Nori, etc.), Spirulina, Chlorella, Kelp, Chondrus Crispus aka ‘Irish sea moss’, and many of the red alga (Rhodophyta) because they produce carrageenan.
But how is algae farmed? To grow the alga aquaculture techniques are used. It is produced in ponds or tanks by adding nutrients and carbon dioxide to the system. Once harvested, the alga must be dried. There are three major methods to accomplish this by: Flocculation, Centrifugation, and Microscreening.
Flocculation is when solids come out of suspension (in a floc/flake) spontaneously or due to an added clarifying agent. A big downfall of this is that it is very costly and therefore only utilized by large scale industries.
Centrifugation is a process that separates algae from water. The machine spins and forces the algae up against the sides, forming a paste. The water flies to the top as it spins rather than staying with the algae against the sides. This is a medium cost operation.
Microscreening is a process of membrane separation via filtration system. It utilizes the properties of water – cohesion and tension – to induce the Capillary effect, thus allowing water to “climb up” / work against gravity and separate out from the alga. Then, a fine mesh screen is used to sift algae out.
Now what happens the all this algae once it is isolated and dried? It has an unbelievable number of purposes! Algae is in the food we eat, colorants/dyes, fertilizer, beauty products, pharmaceuticals, traditional medicine, and more. For example, spirulina and chlorella specifically are dubbed as “Superfoods”. Carrageenan and Agar are extracted and used in many food products as a stabilizer/thickener. In the beauty industry algae is hailed as a miracle worker due to its vitamins, minerals, antioxidants, cell renewal (anti-aging) ability, and its anti-inflammatory and clarifying properties. Beta Carotene is extracted for use from the carotenoids in the algae. When it comes to medicinal properties, algae contains Omega 3s, antioxidants, and it is anticancer and antiviral. Many of these properties can be seen listed on ingredient labels of hundreds of products! It can also be used to make bioplastic - such as biodegradable water bottles or utensils - as well as biofuel. A major benefit of all this algae is carbon sequestration. Ocean-based algae account for 45% to 50% of carbon dioxide absorbed by the biosphere! Although they are small, their short life cycles make them efficient. Research has found that algae powered bioreactors are 400x times more effective than trees at absorbing CO2.
Pictured: a photo from the article “The crop that put women on top in Zanzibar” from BBC.
A final note about how cool algae is, is what the rise in demand is doing for women in other countries! It has become an innovative income for women who have traditionally not worked and been placed in a role which leaves them indoors. As men have chosen to stick with fishing and tourism, the women have started to farm algae nearshore in places like Zanzibar and the Bengali Coast. This allows them to get out of the house, socialize with one another, and make a profit. An article that I like very much regarding this can be read at the following link: https://www.bbc.com/news/stories-44688104.