Temperature and salinity are well-known environmental factors that affect the growth and carrageenan content of Kappaphycus alvarezii (Lobban, et al. 1994). In addition, this is also due to the fact that seaweed at a temperature of 29 0C-310C and salinity of 30–31 psu is protected from exposure to sunlight which has a negative impact, namely ultra violet radiation on the carrageenan content of seaweed. According to Oedjoe et al (2020), the quantity and quality of carrageenan produced from mariculture because difference sunlight intensity, temperature, nutrients, and salinity. The difference in average growth of K. alvarezii seaweed at each temperature change was thought to be due to the effect of temperature on enzyme activity. Hung, et al (2019) explain that the content of nutrients that are responded to by seaweed according to changes in temperature, the higher the temperature, the enzymes do not work properly, besides that it is also influenced by the different ecological characteristics of the waters, which is one of the factors for the difference in average growth at each temperature change. According to Fikri et al (2015) that seaweed is a plant which in its metabolic process requires the suitability of physical and chemical factors of the waters such as water movement, temperature, salt content, nutrients or nutrients (such as nitrate and phosphate), and light lighting. The low growth of seaweed at a temperature of 34 0C-35 0C is suspected because the water is clean with nutrients, besides that at a temperature of 34 0 C-350 C the evaporation is high. While Parenrengi et al. (2010) stated that currents carrying solid particles that will stick to the seaweed thallus will interfere with the photosynthesis process. According to Raikar et al (2001), seaweed is strongly influenced by water conditions such as: waves are needed by seaweed to accelerate nutrients into plant cells, While Pong-Masak & Sarira (2018 ) explained that currents are needed for growth because currents can carry nutrients for seaweed and wash away dirts attached to seaweed, so that seaweed that gets a large supply of nutrients or food will accelerate its growth. The content of nutrients that are responded to by seaweed according to changes in temperature, the higher the temperature, the enzymes do not work properly, besides that it is also influenced by the different ecological characteristics of the waters, which is one of the factors for the difference in average growth at each temperature change (Gerung & Ohno ,1997)
Table 1, showed the chemical nutrition of Carrageenan product that was processed from temperatue and salinity from waters Akle. The carrageenan showed variation in the nutrient content which were related to environmental parameters where seaweed growth (Dewi et al, 2018). As described by Manuhara, et al. (2016) that the nutrition composition can be influenced by the growing parameters (water temperature, salinity, light and nitrate as a nutrient compound), since macroalgae can be considered bioreactor that may able to provide different polysaccharides at different quantity (Manivannan, et.al 2009). Reaffirmed by Periyasamy et al (2016) that carrageenan and chemical nutrition affected by different temperature and salinity. carrageenan and nutrition quality were affected by the growth of hydrocolloid compound in the thallus, where the growths of thallus were influenced by nitrates compound (Matanjun, et al, 2009). Nitrates were carried into the thallus cells by the use of nitrate reductase and was transformed into nitrites (Silkin,et al. 2014). Carrageenan and nutrition show variations in the nutritional content related to environmental factors seaweed growing waters (Wenno et al, 2012). As stated by (Zucchi and Necchi 2001., Paula,et al,2002.) the quantity and quality of carrageenan produced from marine culture varies due to differences in varieties or species, planting age, sunlight intensity, temperature, nutrition, and salinity. Supported by (Hayashi, et al 2007) that the quantity of carrageenan is affected by environmental factors. The salinity, temperature, nutrients and intense irradiance causes high rate of growth. The positive correlation may be due to higher biomass and nutrients in water (Li et al, 2019). The moisture content is an important criterion in determining the quality and shelf-life of processed seaweed meals where high moisture may hasten the growth of microorganisms (Rohani et al., 2012).
The results explain that temperature and salinity influence production and growth. The water temperature observed during the study was from 29 0C to 35 0C. At water temperature 29 0C to 31 0C the growth of K.alvarezii was not affected by ice-ice disease, while there was ice-ice disease at water temperature 320C − 35 0C. Temperature ranges from 29 0C to 31 0C is very supportive to the growth and production of seaweed. According to Radiarta et al., (2013), the water temperature that supports the growth of seaweed is from 29 0C to 31 0C. Temperature and salinity affect the life of biota as they relate to the level of oxygen solubility, the respiration process of aquatic biota, and the rate of degradation of pollutants (Amin et al., 2005). It was also supported by Nur et al (2016) which mentioned that temperature, salinity, turbidity, pH, and dissolved oxygen affect the growth and production. Seaweeds are found in a wide range of teremperature and salinity therefore Seaweeds can live in the littoral and sublittoral zone. Seaweeds are protists and are protected by a layer, which protects them from harmful salinity and acidification of the sea Li et al, (2019). The temperature primarily controls the biogeography of seaweed specie. Mudeng et al ( 2015) Seawater temperature has been increasing annually due to the global warming, which is directly related to the amount of light reaching the sea. These climate changes have caused measurable effects on thallus near their thermal limit, whereas blades may decay or even drop away from floating twines. The temperature can also affect reproduction through its effects on metabolism rates. The reproduction and sorus induction time, and the enhancement of the reproductive traits are dependent from temperature, being a few examples within the brown seaweed (Marinho-Soriano, et al 2006. Abdullah, et al 2020.). Temperature also affects the morphology of the seaweed. Neksidin et al. (2013) explained that the different temperatures will affect the growth and production of seaweed both morphologically and physiologically (Figs. 4 and 5 shown the different responses to temperatures changes). Additionally, Choi et al. (2010) argue that temperature has a significant role in the growth, callus formation, and morphogenetic development of seaweed because of osmoregulation events in cells. They argue that different fluid concentrations between the inside and outside cells encourage the cell's Golgi apparatus to keep trying to balance until it becomes isotonic. As a result, this has an impact on greater energy utilization so that it affects the low growth and development of seaweed (Xiong and Zhu, 2002). At high temperatures, water inside of cells seaweed was lower or shrinking, which is an indication of a hypertonic event resulting from the concentration of the water fluid being more concentrated than the concentration of fluid in the seaweed cells. According to Choi et al. (2010), a more concentrated external environment causes the fluid to flow out. The cell then size decreases as it undergoes plasmolysis, marked by the membrane release from the wall. Xiong and Zhu (2002), Oedjoe et al. (2020) explain that temperature on plants is very complex, such as ionic stress, osmotic stress, and secondary stress. Ion stress due to high-temperature results in Na+ poisoning. Excessive Na+ ions on the thallus surface can inhibit K+ uptake from the environment, even though K+ ions play a role in maintaining cell flaccid and enzyme activity. Meanwhile, osmotic stress caused by an increase in temperature which affects the high osmotic pressure so that it inhibits the absorption of water and the elements that take place through the osmosis process. If the amount of water that enters the cell is reduced, it will reduce the amount of water supply in the cell (Choi et al., 2010 Akib et al. (2015) explained that temperature affects plant growth and development; Andi et al. (2016) also discussed further that temperature affects metabolism, photosynthesis, respiration, and plant transpiration. High temperatures on 33 0C to 35 0C can damage the enzymes so that metabolism does not work well, as well as low temperatures can cause enzymes to be inactive and metabolism to stop (Yoppy et al., 2015) (as shown in Fig. 5).This is due to the number of cells at high temperatures (> 34 0C) is lower than it is in 29 0C-30 0C. Many cells are damaged due to the concentration of media that is too concentrated (hypertonic). According to Amri & Arifin (2016) if the temperature range has exceeded the life span of algae, the growth and development of algal cells is linear and inversely (negative) with an increase in temperature and salinity. High temperature affects the growth and structural changes of algae, among others, the smaller size of the stomata, so that the absorption of nutrients and water is reduced, ultimately inhibiting algae growth at the level of organs, tissues and cells. The impact of temperature changes that are too high or low causes an increase in pressure for aquaculture, including seaweed farming (Sofri et al., 2018). According to Apriyana (2006), the enzymes in K. alvarezii cannot function at temperatures that are too hot or too cold. Supported by Mudeng & Ngangi (2014), that seaweed has a specific temperature range due to the presence of enzymes in seaweed that cannot function at temperatures that are too cold or too hot. High water temperatures affect the rate of photosynthesis and can damage enzymes and cell membranes which are unstable. At low temperatures, membrane proteins and fats can be damaged as a result of the formation of crystals in cells, thus affecting seaweed life, such as loss of life, growth and development, reproduction, photosynthesis, and respiration (Kumar et al, 2020). The impact of rising sea water temperatures clearly influences seaweed production compared to the optimum temperatures around 29 0C to 31 0C (Oedjoe et al., 2020).
Each marine organism has a different tolerance range to salinity, including K. alvarezii. Therefore, salinity is one of the key factors affecting organisms' survival and growth (Choi et al., 2010). The results of salinity measurements during the study ranged from 30 to 36 psut. Pongarrang et al. (2013) stated that K. alvarezii is a seaweed that cannot withstand a range of high salinity (stenohaline). The salt content that is suitable for growth ranges from 28 to 35 psu Meanwhile, according to Ding et al (2013) the range of seaweed growth can thrive in tropical areas with a water salinity of 32 to 34 psu. Changes in temperature can increase changes in salinity, resulting in physiological stresses on aquatic organisms and affect productivity and also increase disease susceptibility (Radiarta et al., 2013). As also supported by Amin et al. (2005), explaining that coastal waters are most easily affected by changes in temperature and salinity. In addition, it also affects temperature and salinity; it can cause bleaching seaweed disease (ice-ice) and will impact seaweed production (as the enzymes' work in forming new cells is disrupted, as shown in Fig. 4).