Chemical and physical characteristics of carrageenan extracted from Eucheuma spinosum harvested from three different Indonesian coastal sea regions

Carrageenan extracted from Eucheuma spinosum harvested from three different coastal sea regions, where this alga has been mainly cultivated, were determined for their chemical and physical characteristics. The carrageenan was extracted from the seaweed using hot alkali followed by precipitation, drying, and milling. The carrageenan properties were determined in terms of yield, ash, mineral, sulfate content, functional group, molecular weight, and viscosity profile. Physical characteristics of carrageenan were evaluated by a texture analyzer for gel strength and a rapid visco analyzer for viscosity. The yield of carrageenan from Sumenep (34.81 ± 5.83%) and Takalar (37.16 ± 3.26%) was found to be relatively higher than that of Nusa Penida (25.81 ± 1.93%). The calcium content was higher than magnesium, potassium and sodium content, and no cadmium, lead, mercury, and arsenic detected in all carrageenan. The ash content was around 29%; while, the sulfate content was in the range of 30–32%, and those were not different in all carrageenan. The presence of sulfate content was identified by FTIR at absorption band of 1373 cm^?1. It was found that the molecular weight of carrageenan from Takalar were relatively higher and the gel strength of carrageenan from Takalar were significantly higher than that of carrageenan from Nusa Penida and Sumenep. Likewise, upon cooling from 80 to 20°C, the viscosity profile of carrageenan from Takalar characterized by higher viscosity compared to that of carrageenan from Sumenep and Nusa Penida. These results indicated that carrageenan from Nusa Penida, Sumenep, and Takalar were identified as iota‐carrageenan with similar physico‐chemical characteristics except for the gel strength, viscosity profile upon cooling from 80 to 20°C and the yield.     

Nutritional study of Kapparazii powderTM as a food ingredient

Kappaphycus alvarezii is one of the most important commercial sources of carrageenan. Red seaweeds are found in tropical areas, and K. alvarezii is famous for its high growth rate among other tropical red seaweeds. This study was conducted to produce Kapparazii powder^TM, a product comprised of high amount of carrageenan with valuable nutrients from K. alvarezii found in Sabah, Malaysia. Spray drying and an environmentally friendly process without using chemicals were employed to produce Kapparazii powder^TM. Physicochemical properties of Kapparazii powder^TM such as proximate composition (moisture, protein, lipid, ash, and crude fiber), mineral content, heavy metals, vitamins, amino acid, color, viscosity, gel strength, swelling capacity, and water and oil holding capacity were evaluated. Kapparazii powder^TM contained moisture (4.69?±?0.03 %), protein (5.11?±?0.02 %), lipid (1.00?±?0.02 %), ash (14.52?±?0.01 %), and crude fiber (0.93?±?0.02 %). Color analysis of Kapparazii powder^TM showed that lightness (L ^*)?=?89.51?±?0.02, redness (a ^*)?=??1.27?±?0.03, and yellowness (b^*)?=?5.49?±?0.02. The value of viscosity, gel strength, swelling capacity, and water and oil holding capacity of the Kapparazii powder^TM were 0.06?±?0.00 Pa.s, 82.77?±?3.66 gf, 100?±?0.00 mL.g^?1, 4.67?±?0.58 g.g^?1, and 5.11?±?0.36 g.g^?1, respectively. Moreover, Kapparazii powder^TM did not inhibit proliferation of L929 cells after 24 h of exposure at the highest concentration (2 mg.mL^?1). In conclusion, the Kapparazii powder^TM as a source of high nutrient hydrocolloid suggested on the point of healthy ingredient for food industry application.     

DIFFERENTIAL LOCALIZATION OF CARRAGEENAN GELLING SEQUENCES IN KAPPAPHYCUS ALVAREZII VAR. TAMBALANG (RHODOPHYTA) WITH FITC-CONJUGATED CARRAGEENAN OLIGOSACCHARIDES1

The ability of kappa (κ) and iota (ι) carrageenans to form gels is dependent upon the regular repeat of disaccharide units along the carbohydrate chain. Short, chemically- and enzymatically-purified fragments of κ and ι carrageenan were conjugated to fluorescein and used as specific hybridization probes for localization of κ and ι carrageenan gelling sequences within the cells walls and intercellular matrices of Kappaphycus alvarezii (Doty) Doty. The probes label cell walls and intercellular matrices under ionic conditions appropriate for gelation of κ and ι carrageenans. The distribution of κ and ι carrageenans in the matrix and cell walls of K. alvarezii was determined with respect to cell type (epidermis, cortex, medulla, and central axis) and age. The κ-probe labels the cell walls of all cell types except epidermal in both young and old tissues. In contrast, the ι-probe labels the cell walls of the epidermis in both young and old tissue and the cell walls of the thylles only in old tissue. Both probes label intercellular matrix material; however, ι-probe labelling is very much weaker than κ-probe labelling. The results indicate that FITC-conjugated carrageenan oligosaccharides are useful tools that provide information on gelling subunit distribution.     

Optimization of culture conditions for the direct regeneration of Kappaphycus alvarezii (Rhodophyta,Solieriaceae)

Cultivation of seaweeds on a commercial scale requires a large number of propagules with desirable phenotypic traits which include high growth rates and resistance to diseases. Seaweed micropropagation can be considered as one of the best methods to provide a large amount of seedlings for commercial cultivation. This study was carried out to optimize the parameters known to affect the growth of Kappaphycus alvarezii in vitro and subsequently improve the production of seedlings through micropropagation. Suitability of media, concentration of phytoregulators, types and concentration of fertilizers, culture density, light intensity, interval of aeration activity, salinity, and pH were found to be critical factors for the growth of K. alvarezii. The optimum condition for direct regeneration of K. alvarezii in a culture vessel was found to be cultivation of explants in Provasoli's enriched seawater (PES) media supplemented with 2.5 mg L^?1 6-benzylaminopurine (BAP), 1.0 mg L^?1 indole-3-acetic acid (IAA), and 3.0 mg L^?1 natural seaweed extract (NSE) with culture density of 0.4 %?w/v, under light intensity of 75 μmol photons m^?2 s^?1, continuous aeration of 30.0 L h^?1, salinity of 30.0 ppt, and pH 7.5. An airlift photobioreactor was constructed for the mass propagation of K. alvarezii explants with optimum culture conditions obtained from the study. The optimum growth rates of the K. alvarezii explants in culture vessels (5.5 % day^?1) and photobioreactor (6.5 % day^?1) were found to be higher than the growth rate observed in field trials in the open sea (3.5 % day^?1). The information compiled during the course of this study will be of utility to commercial seaweed cultivators.     

Effects of improved post-harvest handling on the chemical constituents and quality of carrageenan in red alga,Kappaphycus alvarezii Doty

Red alga Kappaphycus alvarezii Doty is an important commercial species widely cultivated in southeast Asian countries for its polysaccharide, kappa-carrageenan. Common post-harvest handling technique involves sun-drying of harvested seaweed on platforms at the farms. Quantity and quality of carrageenan varies depending on the duration and care taken during the post-harvest handling of the raw seaweed. In this study, dynamics of moisture content, water activity index (aw), carrageenan yield, and carrageenan quality were investigated by subjecting the seaweed to three post-harvest methods: (1) freeze-drying (FD), (2) shade-drying (SD), and (3) direct sun-drying (DSD). Seaweed dried under FD and SD produced high yield (56–58 %), superior gel strength (1,454–1,424 g cm^?2), high viscosity (57–58 cPs), and low syneresis (15–17 %). But, carrageenan extracted from DSD seaweed gave 28 % lower yield, 38 % lower gel strength, 27 % lower viscosity, and 8–9 % higher syneresis. In addition, gelling temperature and melting temperature of the DSD carrageenan were lower by 4 and 9 °C, respectively. Molecular size analyses of carrageenan extracted from seaweed dried under FD and SD contained carrageenan of 700 KDa (80 %) and 200 KDa (4–10 %). However, carrageenan extracted from DSD seaweed contained smaller carrageenan molecules, 460 KDa (55 %), 210 KDa (25 %), and <100 KDa (20 %). Further, scanning electron microscope images illustrated the severe effects of DSD on the morphology of seaweed cells. Therefore, SD technique was found to be the best post-harvest processing technique that gave quality carrageenan in a high quantity. Due to its simplicity and low cost, it is a practical approach to be practiced in southeast Asian countries.     

Effect of epiphyte infection on physical and chemical properties of carrageenan produced by Kappaphycus alvarezii Doty (Soliericeae,Gigartinales, Rhodophyta)

Epiphytism of filamentous red algae is a serious problem in Kappaphycus farms in the Philippines, Indonesia, Malaysia, and Tanzania. The causative organism of epiphyte outbreak has been identified as Neosiphonia apiculata (Hollenberg) Masuda and Kogame, but its actual effect on carrageenan quality has not yet been established. Therefore, yield and quality of carrageenan from healthy and infected specimens were examined. Infected specimens showed 20.5?±?2.5 % DW lower carrageenan yield compared with the healthy seaweed (65.5?±?4.2 % DW). Infected specimens also had a higher phenolic and fatty acid content, compared with healthy specimens. The carrageenan from the infected seaweed showed 74.5?±?2.8 % lower viscosity, 52.6?±?3.6 % lower gel strength, 22.9?±?1.5 % higher syneresis, and 5 °C higher melting temperature as compared with carrageenan from healthy specimens. FTIR and ¹³C-NMR analysis of carrageenan from infected seaweed did not show any differences in their functionality or carbon atom chemical shift as compared with healthy and standard k-carrageenan. However, size exclusion chromatography showed the infected carrageenan molecular size to be 80 kDa as compared with 800 kDa for the healthy and standard k-carrageenan. These findings prove that infection of Kappaphycus by the filamentous red algae epiphyte, N. apiculata, reduces carrageenan molecular size and affects the physical properties of the carrageenan.     

Effects of a commercial extract of the brown alga Ascophyllum nodosum on the biomass production of Kappaphycus alvarezii (Doty) Doty ex P. C. Silva and its carrageenan yield and gel quality cultivated in Brazil

Despite of its success, the carrageenan industry has had to cope with difficulties due to epiphyte infestations and diseases known as ice-ice. Some promising results in respect of biomass production, carrageenan yield, and protection epiphytes were obtained using a powdered extract of the brown alga Ascophyllum nodosum in Kappaphycus alvarezii seedling production. This study focused on the effects of the A. nodosum extract on the treatment of K. alvarezii cultivated on commercial floating rafts not only to evaluate improvements demonstrated in vitro but also the effects on the quality of the carrageenan. The seedlings were treated in an A. nodosum extract solution and placed alongside their controls on commercial floating rafts using the tubular net technique. Daily growth rate, carrageenan yield, gel strength, and gel viscosity were obtained over 20 and/or 40 days. After 20 days, daily growth rates showed no significant difference (p?=?0.44), while the carrageenan yield was higher in samples that were treated with the A. nodosum solution (p?<?0.001). After 40 days, both daily growth rate (p?=?000.7) and carrageenan yield (p?=?0.009) were higher in treated samples; however, gel strength was higher in control samples (p?=?0.03) as viscosity was also highest in the samples which had not been treated (p?<?0.001). The use of the A. nodosum extract treatment on the cultivation in situ of K. alvarezii was positive since after 40 days when the daily growth rate and carrageenan yield increased. In spite of the negative effect on the quality of the semi-refined carrageenan, the values were within commercial standards.     

Does biofouling influence <Emphasis Type="Italic">Kappaphycus alvarezii</Emphasis> (Doty) Doty ex Silva farming production in Brazil?

The commercial cultivation of Kappaphycus alvarezii is the main source of raw material for the carrageenan industry. Brazilian commercial farming uses floating rafts that serve as substrata for fouling organisms that may affect production of the carrageenophyte seedlings. The aim of this work was to identify and quantify the biofouling on floating rafts at Sepetiba Bay, Rio de Janeiro State (23° 02′ 25″ S and 43° 53′ 39″ W), and to evaluate seedling damage caused by epibionts and endobionts. Samples were collected from August 2006 to August 2007. In each assessment, organisms contained in random sampling areas of 18 quadrats of 0.10 m² (n = 18) were removed from floating rafts. K. alvarezii seedling samples were collected to verify the presence of epibionts or endobionts (n = 30). Twenty-four taxa belonging to seven groups of animals and three groups of seaweed were found. The percentage occurrence estimated 13 dominant organisms and amphipod tubes: e.g., Chondracanthus tedii, Cladophora vagabunda, Gracilariopsis tenuifrons, Hypnea spinella, Hypnea musciformis, Hincksia mitchelliae, Spyridia spp., Ulva spp., Bowerbankia sp., Bugula neritina, Botryllus sp., Haplosclerida sp., and Perna perna. Richness, equitability, diversity, and total biomass varied significantly during the study period (p < 0.001). There was a tendency for higher biomass values in August 2007. After 6 months, epibionts (i.e., Chlorophyta, Rhodophyta, Chordata, Cnidaria and Ectoprocta) were found on K. alvarezii seedlings. Endobionts were not found in this study. The biofouling biomass was not found to have a significant effect on K. alvarezii daily growth rate, carrageenan yield, or quality (gel strength and viscosity; p > 0.05).     

Effect of the commercial extract of the brown alga Ascophyllum nodosum Mont. on Kappaphycus alvarezii (Doty) Doty ex P.C. Silva in situ submitted to lethal temperatures

Kappaphycus alvarezii is being introduced in several countries and in some of them there is a need to adapt this cultivation to periods with lethal temperatures, such as the 16–18 °C that occurs in the winter in southern Brazil. Moreover, there is the need to maintain the seedlings during this lethal temperature period. Considering the promising results obtained with the commercial powder extract of Ascophyllum nodosum (Acadian marine plant extract powder—AMPEP) treatment in the cultivation of K. alvarezii in vitro and in the sea allowing more resistance to epiphytes and increasing the growth rate and carrageenan yield, it was hypothesized that seedlings previously subjected to an AMPEP treatment could be more resilient to lethal temperatures. The daily growth rate and carrageenan yield and gel quality (gel strength and gel viscosity) of K. alvarezii in vitro previously treated with AMPEP were analyzed under temperature stress. The daily growth rates and the gel strengths of the AMPEP-treated samples were increased. In spite of the lower carrageenan yield and lower gel viscosity, the values were within the ones accepted by the carrageenan industry. Thus, the treatment of the seedlings of the K. alvarezii with AMPEP solution can be used as an alternative to lower temperature effects on crops as a preventive action for the cultivation of the seedlings in tanks and in the sea in periods of low temperatures at sea.     

<Emphasis Type="Italic">Kappaphycus alvarezii</Emphasis> (Rhodophyta,Areschougiaceae) cultivated in subtropical waters in Southern Brazil

Four strains of Kappaphycus alvarezii were cultivated in the subtropical waters of Florianópolis, Santa Catarina State, Brazil (27°29′19′′ S/48°32′28′′ W), from February 2009 to February 2010. Seaweeds were cultivated on floating raft near of mussel farms. Salinity ranged from 29 to 36 psu and temperature from 17.1 to 28.5°C. Higher growth rates (5.12–4.29% day⁻¹) were measured in summer and autumn, showing a positive correlation between growth rate and water temperature. Lower growth rates (0.54–0.32% day⁻¹) occurred in winter, resulted mainly by biomass loss. Significant differences were observed among the strains in spring and the brown tetrasporophytic strain was the only one which failed to recover, being excluded of the experiments. The effect of cultivation periods (36, 42, and 97 days) on carrageenan yield, gel strength, and viscosity were analyzed. Carrageenan yields were higher for plants kept 42 days in the sea (28%), against 25% for 36 and 97 days. There were no significant differences in carrageenan yield among the strains analyzed. Viscosity increased with the increase of cultivation period, while gel strength seemed to vary at random. Tetrasporangia and cystocarps were not observed, and lost fragments did not attach outside the raft. In general, dissolved inorganic nitrogen concentration decreased around the cultivation area as compared to the mussel farm. Results show that cultivation of K. alvarezii is technically feasible in subtropical waters and can be associated with local mussel farms, mitigating the eutrophication and, eventually, increasing the economic return of the farmers.     

Effects of salinity on the growth rate,carrageenan yield,and cellular structure of <Emphasis Type="Italic">Kappaphycus alvarezii</Emphasis> (Rhodophyta,Gigartinales) cultured in vitro

Kappaphycus alvarezii was cultured in vitro under salinities ranging from 15 to 55 psu for 35 days to determine the differential effect on growth rate, carrageenan yield, and cellular structure. Plants kept in 15 psu died after 3 days, while plants cultured in 55 psu presented low growth rates during the entire experimental period (0.28% day⁻¹). Plants cultured in 25, 35, and 45 psu showed growth rates normally associated with this species (between 3% and 4% day⁻¹) and similar cellular morphology. Carrageenan yield was significantly higher in plants cultured in 25 psu in relation to the other treatments. As observed by light microscopy, plants cultured in 15 psu showed cellular turgidity and increased cell wall thickness, both consequences of hyposalinity. Chloroplasts and other membranous organelles underwent rupture and considerable disorganization in ultrastructure. Although branches from the 55 psu samples showed plasmolysis, cells were able to maintain chloroplast integrity, despite their rudimentary features. In high salinities, great concentrations of floridean starch grains were observed in subcortical cells, indicating their probable participation in osmoregulation. Based on these results, we defined the range of 25 to 45 psu as the limits of saline tolerance for K. alvarezii. While new field studies are required to confirm these results, it can be concluded that new sites, such as inactive or abandoned shrimp tanks with salinities up to 25 psu, could be considered for commercial farming.     

Seasonal variations in thalli and carrageenan composition of Gigartina pistillata (Gmelin) Stackhouse (Rhodophyta, Gigartinales) harvested along the Atlantic coast of Morocco

The biology and biochemistry of Gigartina pistillata (Gmelin) Stackhouse collected monthly at Nation Beach (Morocco), was studied during one year. The biological study showed one period of active growth from April to July. The thallus composition was quite stable during the major part of the year. The dry matter was maximum in May and August and minimum in January. The maximum carrageenan content occurred in June and September (about 37%) and the minimum carrageenan content occurred in February (19.0%). The total nitrogen content varied significantly, with a maximum in January (1.98%) and a minimum in August (0.7%). The ash content was significant (23–32%) with a maximum in August and a minimum in May. The carrageenan extracted from natural populations of Gigartina pistillata was a mixture of lambda‐type and kappa‐type carrageenans. The 3,6‐anhydrogalactose varied between 4.5 mol% in June to 25 mol% in February. For industrial applications the extract could be considered as a lambda‐type. The best period for harvest of G. pistillata in Morocco is between July and August when biomass and viscosity are at their maximum. A relationship between the physical characteristics of G. pistillata carrageenans and its seasonal cycle was deduced.     

Cultivation and carrageenan yield and quality ofKappaphycus alvarezii in the waters of Vietnam

The carrageenan-producing red algaKappaphycus alvarezii (Doty) Doty was brought to Vietnam from Japan in 1993. Branch fragments of this species were cultivated in a pond, lagoon, inlet and offshore in Vietnam for the first time. The best daily growth rate (DGR) of plants grown in the lagoon area attained 9–11 % day^–1 in May to June (cold season). The water temperature and salinity in this area ranged from 27.2–32.4 °C and 31.4–33.7 °C, respectively. DGR of plants grown in the inlet ranged from 7 to 9% day^–1 in June. Grazing by fish has been observed to occur in this area. The DGR of plants grown in the pond ranged from 5–6% in January–July, but decreased to less than 4% day^–1 in August (hot season). K. alvarezii in Vietnam showed a carrageenan yield of 18.8–24.6% and gel strength of 1566–1712 g cm^–2. These values are similar ones obtained fromK. alvarezii cultivated in the Philippines and Indonesia.     

Effect of ammonium on growth and carrageenan content in Kappaphycus alvarezii (Gigartinales,Rhodophyta)

Kappaphycus alvarezii, cultured in a region deficient in nitrogen with intermittent application of 10 mM ammonium at three-day intervals for 1 hour, attained a daily growth rate of 4.6%, which was considered to be the optimum growth rate. Under such conditions, the C/N ratio was 29 with a carrageenan content of 58% and gel strength of 45–70 g cm^–2. Gel strength of carrageenan was high when nitrogen content was high and vice versa.     

The effects of selected cultivation conditions on the carrageenan characteristics of <Emphasis Type="Italic">Kappaphycus alvarezii</Emphasis> (Rhodophyta,Solieriaceae) in Ubatuba Bay,São Paulo,Brazil

The yield and the quality of carrageenan depend, among other things, on the cultivar or strain and on the cultivation and processing techniques. This work presents carrageenan yields and some properties of Kappaphycus alvarezii under selected cultivation conditions i.e. cultivation period, depth and planting density. Growth rates (GR) ranged from 5.2–7.2% day⁻¹, with the highest GR at 28 days, at 0–0.5 m depth, and planting density of 12 and 8.4 plants m⁻². Highest productivity was observed in samples after 44 and 59 day cultivation period, which were grown at 0–0.5 m depth, and a planting density of 24 plants m⁻². Carrageenan yields, iota fraction, viscosity, molecular weight and gel strength were measured. A cultivation period of 28 days during the winter had a significant higher carrageenan yield, while samples from 59 days showed a significantly higher iota fraction. Carrageenan also presented an increasing molecular weight under longer cultivation periods. A similar trend was observed for viscosity and gel strength. All samples cultivated in Brazil gave higher values when compared to a K. alvarezii commercial reference sample, with the exception of carrageenan yield values, which were lower in this study. Taking into account all parameters, the culture condition which provided the best carrageenan from a commercial perspective were 45 days of cultivation, growing at the surface, with a planting density of 12 plants m⁻². Considering that this study was performed in the least favorable season (winter), these results indicate that the site is suitable for the implementation of commercial cultivation.     

An initial comparison of tubular netting versus tie–tie methods of cultivation for Kappaphycus alvarezii (Rhodophyta, Solieriaceae) on the south coast of Rio de Janeiro State, Brazil

A new cultivation technique for Kappaphycus alvarezii was used in the Brazilian southeastern coast (23°02′25″ S and 43°53′39″ W), the tubular netting on floating rafts. The tubular net technique (TN) was compared with the current method of tie–tie (TT). After 47 days, the daily growth rate (mean ± SD of TN and TT = 3.4 ± 0.7% day⁻¹), carrageenan yield (mean ± SD of TN and TT = 36 ± 1.3%), gel strength (mean ± SD of TN and TT = 730 ± 114.5 g cm2), and viscosity (mean ± SD of TN and TT = 350 ± 60.4 cP) did not differ between the two techniques (p > 0.05). The amount of time used to plant (TT = 30.2 ± 2.3 min and TN = 13.3 ± 3.4 min) and to harvest the seedlings (TT = 36.2 ± 2.7 min and TN = 17.8 ± 3.7 min) were lower in TN (p < 0.001). It is concluded that TN was more effective than TT, the cultivation management (time rates used to plant and harvest the seedlings) was 53.6% faster, no seedlings were lost, the cost was lower, and an estimated return in 1 year of nearly 20% more than that of the TT technique.     

THE PERFORMANCE OF SPRAY‐IRRIGATED ULVA LACTUCA (ULVOPHYCEAE,CHLOROPHYTA) AS A CROP AND AS A BIOFILTER OF FISHPOND EFFLUENTS1

The seaweed Ulva lactuca L. was spray cultured by mariculture effluents in a mattress‐like layer, held in air on slanted boards by plastic netting. Air‐agitated seaweed suspension tanks were the reference. Growth rate, yield, and ammonia‐N removal rate were 11.8% · d^?1, 171 g fresh weight (fwt) · m^?2 · d^?1, and 5 g N · m^?2 · d^?1, respectively, by the spray‐cultured U. lactuca, and 16.9% · d^?1, 283 g fwt · m^?2 · d^?1, and 7 g N · m^?2 · d^?1, respectively, by the tank U. lactuca. Biomass protein content was similar in both treatments. Dissolved oxygen in the fishpond effluent water was raised by >3 mg · L^?1 and pH by up to half a unit, upon passage through both culture systems. The data suggest that spray‐irrigation culture of U. lactuca in this simple green‐mattress‐like system supplies the seaweed all it needs to grow and biofilter at rates close to those in standard air‐agitated tank culture.     

Seasonal variation in growth and carrageenan yield in cultivated Kappaphycus alvarezii (Doty) Doty on the coastal waters of Ramanathapuram district,Tamil Nadu

Kappaphycus alvarezii, a kappa carrageenan yielding red seaweed, was cultivated in Indian subtropical waters on the Palk Bay side of Bay of Bengal in Ramanathapuram district, Tamil Nadu, at three different sites: Vedalai, Munaikadu, and Thonithurai, for 1 year from April 2011 to March 2012. The maximum crop yields of 416 ± 51 and 550 ± 41 FW raft^?1 were recorded at Vedalai and Munaikadu, respectively, in December 2011, whereas a maximum of 326 ± 49 FW raft^?1 was recorded at Thonithurai in April 2011. Similarly, the maximum daily growth rates (DGRs) of 4.30 ± 0.51 % and 4.92 ± 0.40 % were obtained at Vedalai and Munaikadu, respectively, in December 2011, and 3.76 ± 0.48 % was recorded at Thonithurai in April 2011. Variations in environmental parameters like seawater temperature, salinity, nitrate, and phosphate were found to influence the growth of the seaweed. The maximum carrageenan content as a percentage of dry weight was 29.30 ± 0.61 % (Vedalai), 31.00 ± 0.71 % (Munaikadu), and 29.10 ± 1.12 % (Thonithurai) in March 2012. The data on moisture content (%), clean anhydrous weed/salt ratio, and carrageenan yield obtained in this study fulfilled those of international standards. Further, the results indicated that large-scale cultivation by either NGOs or self-help groups (SHGs) may be taken up along the coastal waters for the benefit of the poverty-stricken coastal people as their livelihood, as the growth rate obtained in this study compared well with that recommended for commercial cultivation elsewhere.     

Cultivation and utilisation of red seaweeds in the Western Indian Ocean (WIO) Region

Seaweed farming in the Western Indian Ocean (WIO) Region is carried out in a number of countries, most of them farming Eucheuma denticulatum, Kappaphycus alvarezii and Kappaphycus striatum. These species are farmed mostly in Tanzania with limited production in Madagascar, Mozambique and Kenya; current production (2012) stands at 15,966 t (dry weight) year^?1 of Eucheuma and Kappaphycus, valued at US$ 4.2 million with 95 % of this tonnage coming from Tanzania. Other countries in the region have limited or no seaweed production owing to problems of epiphytes, ice ice and markets. The problem of epiphytes coupled with ice ice that WIO countries are facing causes die-off of Kappaphycus which is the preferred species in foreign markets for its thicker gel, kappa carrageenan (vs. the weaker iota carrageenan from Eucheuma). New efforts are put to curb these problems including moving seaweed farms to deeper waters and cultivation trials of other carrageenophytes as well as agar-producing species, agarophytes. Research work has been initiated to evaluate Gracilaria and Hypnea farming and processing in Tanzania, the Republic of Mauritius and Mayotte. Gracilaria farming is at experimental stages as a biofilter of fishpond effluents and as potential species for the production of agar with growth rates of 1.5–1.9 % day^?1. Hypnea farming is only being initiated in Mauritius and Mayotte at present. Other innovations including value addition by making various seaweed products and encouraging the consumption of seaweed as food at least in Tanzania and Mauritius are increasing further the importance of the seaweed farming and processing industry in the WIO Region.     

In situ variability of carrageenan content and biomass in the cultivated red macroalga <Emphasis Type="Italic">Kappaphycus alvarezii</Emphasis> with an estimation of its carrageenan stock at the scale of the Malasoro Bay (Indonesia) using satellite image processing

The combination of in situ measurements, hydrodynamical modeling, and satellite imagery processing presents a complete tool to improve seaweed culture management. This study measured the evolution of carrageenan content during 1-year period and estimated the biomass of Kappaphycus alvarezii at a bay scale in Malasoro Bay, Indonesia. It allowed the determination of the carrageenan stock at the scale of the bay. The carrageenan content was assessed from different parts, i.e., basal and apical, of the thallus. The biomass from T ₀ (beginning of the cultivation) to T ₄₅ (harvesting time) was determined at two seasons. Satellite image processing was performed to estimate the biomass at bay scale using parcels resulting from a semi-automatic delineation process. As no long-term in situ environmental data existed in the study area, a 3D hydrodynamical model (Model for Application at Regional Scale 3D) was implemented to obtain high-frequency salinity, water temperature, and currents. The high carrageenan yield was obtained from April to September 2015 (54–63%) when temperature ranged from 25 to 30 °C, salinity range from 33.8 to 34.8 psu, and precipitation below 0.5 mm. The biomass at bay scale was estimated at 2590 t with the highest carrageenan stock at 1.8 t ha^?1 in May 2015. The carrageenan yields and quality obtained in this study fulfilled the specification recommended for industry, and the cultivation of K. alvarezii can be carried out at optimal environmental conditions on April–September. The comprehensive approaches used in this study provide information for carrageenan stock and seaweed culture management as an important economic activity to support Indonesian coastal communities.