# Different _Chondrus crispus_ Aquaculture Methods and Carrageenanan Extraction
###### Abstract  
With the notable scarcity of _Chondrus crispus_ on the Portuguese coast, and interest in exploiting compounds such as carrageenanan, this study focuses on investigating different aquaculture methods and recording the yield of carrageenanan from specimens grown by different methods. We compare the growth of _Chondrus crispus_ in aquaculture using Free Floating, Cages, Attempted Fixation on Rock, and Fixed Line similar to Long Line. The best method was Free Floating where Nursery 0 had a 24-day Specific Growth Rate (SGR) of 2.08 \(\pm\) 0.47%/day. The worst method in terms of growth was Nursery 2 (Attempted Fixation on Rock) where the SGR at 28 days was 0.33 \(\pm\) 0.69%/day, and no fixation was observed. In terms of carrageenanan extraction, all culture methods gave rise to biomass that had a lower extraction yield than wild specimens, at 50.95 \(\pm\) 4.10%. However, the Free-Floating method from Nursery 1 showed an acceptable carrageenanan content (31.43 \(\pm\) 7.00%). Therefore, we demonstrate that the concept of _C. crispus_ cultivation may be key to promoting the sustainability and stability of this species. Chondrus crispus; SGR; carrageenanan; aquaculture; macroalgae 2023  
Marine macroalgae are also considered to be the plant-based food of the future and have even earned \"superfood\" status--a food market term in recognition of their health benefits, which stem from their superior nutritional profile and abundance of bioactive compounds [5]. The Asian food industry has historically demonstrated strong macroalgae interest, mostly for direct consumption. Meanwhile the same cannot be said for their western counterparts, who mainly exploit macroalgae as a source of functional polysaccharides (carrageenanan, agar, and alginates) used as biological additives to give texture and stabilize industrially produced foods, for example [6; 7]. The aquaculture of macroalgae is shown to be an efficient method of obtaining the algal biomass needed for a wide variety of products. These products fit into various industries such as food [8], cosmetics [9], pharmaceuticals [10], biofuels [11] and even biopolymers for use in solar panels [12]. The Rhodophyta group (red macroalgae) has the potential, in the future, to be a major source of natural compounds, such as phycocolloids, algal polymers as substitutes for animal gelatin, and even natural pigments for the textile industry [13; 14]. The polysaccharides found in the Rhodophyta phylum, agar and carrageenanan, are among the most studied and commercially applied algal bio-compounds, and their extraction and purification methods are more advanced in terms of cost-effectiveness and economic viability due to commercial pressure. Agar and carrageenanan are used, for example, in the food and pharmaceutical industries as multifunctional additives, such as stabilizers, emulsifiers, and homogenizers, and this has particularly promoted the growth of seaweed aquaculture [15; 16]. Within this group of seaweeds exists the species _Chondrus crispus_, also known as \"Irish Moss\". This red macroalgae grows abundantly on the rocky coasts of the northern and central Atlantic Ocean [17]. It is already widely used for the extraction of carrageenanan for food use [18] and exploited for its bioactive properties [8]. The vast majority of _C. crispus_ biomass is obtained through harvesting. In Southeast Asia, there is already an effort to produce red macroalgae in aquaculture systems with the objective of insertion into markets that value this species immensely, but there is no such effort in the western market. One of the main sectors of commercialization is the food market with direct consumption of seaweed. _C. crispus_ is also an interesting commodity for such a market, being one of the seaweeds with the highest concentration of soluble fiber (15-22%) [19]. The history of _C. crispus_ commercialization and interest is well-documented and spans a significant period of time [14; 18; 20; 21; 22; 23; 24; 25].