Gracilaria chilensis (named for its importance and prevalence in Chile) is a very economically and ecologically important red macroalga with varying morphology. The cylindrical, filamentous thalli are about 1 to 2 millimeters in diameter, usually purple-red, occasionally yellow-brown, and can grow quite long, up to 5 meters in length. Identification of the specific species is difficult in the field however because of a lack of unique diagnostic characteristics and the variability of species morphology. Depending of growing conditions (light availability, depth, water movement, nutrient levels), Gracilaria chilensis can take on a broad variety of overall shapes from short, bushy, and densely branched to long and sparsely branched. Gracilaria chilensis is naturally found in the intertidal or subtidal zone (up to 10 meter depth), where it can grow in sheltered harbors, bays, or estuaries on sand, mud, or rocky substrates.
Gracilaria chilensis is abundant in South America (Chile) as well as Africa, China, and the Indonesia.
Gracilaria chilensis is one of the most economically important species in the agar industry, but is also enjoyed as a food source by humans and is often seen in Japanese, Hawaiian, and Filipino cuisine.
Gracilaria chilensis is cultivated in South America (Chile) and elsewhere for the agar industry and is beginning to be incorporated into aquaculture industry in association with shrimp and fish farms especially in the Indo-Pacific. Gracilaria chilensis is the primary seaweed species cultivated in Chile (as opposed to wild harvesting or beach collection), contributing significantly to the Chilean economy.
Both subtidal and intertidal cultivation techniques are used with Gracilaria chilensis. Regardless of the planting method, production relies upon the capacity of Gracilaria chilensis to develop an underground thallus system that anchors the algae to the soft bottom. Some areas are able to achieve production capacity of 150 metric tons per hectare each year. Severe drops in productivity can occur if the same area is used for several consecutive years. Research and demonstration projects are also in progress where Gracilaria chilensis is an element of Integrated Multitrophic Aquaculture (IMTA), helping to neutralize fish wastes and still serve as a revenue-generating crop.
While fish farms provide employment and food for many in coastal regions, one of the major issues associated with these aquaculture facilities is that they produce large amounts of wastes, including dissolved inorganic phosphorus and nitrogen. These nutrients can be toxic in large amounts, creating “dead zones” around fish farms where no other organisms can exist. To reduce this problem and take advantage of the free nutrients, farmers have begun integrating algae such as Gracilaria chilensis into their fish cages. Not only does this growing algae provide a food source for the fish, but it effectively soaks up excess nutrients to protect the environment. This approach is known as Integrated Multitrophic Aquaculture (IMTA). When the algae has grown substantially it is able to be harvested for food or agar. Interestingly, it has been found that algae grown in these conditions not only grows faster but produces a better quality agar than algae grown in pure seawater.