Kappaphycus Striatum Research Articles

GCMS and LCMS/MS Based Analysis for the Identification and Characterization of Bioactive Metabolites of Seaweed Kappaphycus striatus as an Anti-hypertensive and Anti-hypercholesterolemic Agent

GCMS and LCMS/MS Based Analysis for the Identification and Characterization of Bioactive Metabolites of Seaweed Kappaphycus striatus as an Anti-hypertensive and Anti-hypercholesterolemic Agent

Ice-ice disease in cultivated eucheumatoid seaweeds: The perspectives of farmers

ABSTRACT Eucheumatoid seaweeds, encompassing the genera Kappaphycus and Eucheuma, are widely cultivated globally, particularly in tropical regions. However, ice-ice disease (IID) poses a significant challenge to their production, causing substantial economic losses. This study aimed to elucidate the factors contributing to IID in eucheumatoid seaweeds, focusing on the perspectives of seaweed farmers in Sibutu, Tawi-Tawi, Philippines. A mixed methods approach was employed, utilizing both one-to-one interviews (n = 96) and focus group discussions. The majority of the interviewed farmers were male, aged between 31 and 60 years, with extensive experience (11‒25 years) in seaweed cultivation. Notably, all participants possessed a familiarity with IID since childhood. Farmers described IID as a pathological condition affecting eucheumatoid seaweeds, characterized by the emergence of white and soft areas on the seaweed thalli. The initial stages of the disease manifest as a pale discolouration of the thalli and the presence of epiphytes or debris. Several environmental factors were identified by the farmers as contributing to IID incidence, including high or low water temperatures, low salinity (particularly after heavy rainfall), stagnant water currents, nutrient deficiencies, inadequate seedling quality, and poor farm management practices. Additionally, deepwater (nearshore) farms were reported to be more susceptible to IID. Farmers noted that easterly winds could exacerbate the disease by facilitating the infestation of epiphytes on the seaweed. Furthermore, the prevalence of IID was observed to be highest during the dry and hot season. Kappaphycus striatus was identified by the farmers as being more susceptible to IID compared with K. alvarezii and Eucheuma denticulatum. The negative impact of IID on farmers’ livelihoods was also highlighted. Some mitigation strategies employed by the farmers included the application of inorganic nutrient enrichments (e.g. ammonium phosphate (16–20-0, N-P-K) and complete (14–14-14, N-P-K) fertilizers), frequent relocation of infected seaweed to different farms, and the cultivation of more IID-resistant species.

Growth Performance of Kappaphycus alvarezii and Kappaphycus striatus cultivated in Ekas Bay, East Lombok Regency, West Nusa Tenggara Province

alvarezii is a superior product of Indonesian fisheries, producing carrageenan which is used as a food, cosmetic, and medicinal ingredient. K. striatus is a carrageenan-producing red alga that began to be cultivated in the Ekas waters of East Lombok in 2023. K. striatus is more resistant to epiphytes and sudden climate change. The purpose of this study was to analyze the growth of Kappaphycus alvarezii and Kappaphycus striatus. The research was conducted in Ekas Bay, Jerowaru District, East Lombok Regency. The research was conducted from November 8, 2023, to January 8, 2024. This research used an experimental method with T-test analysis. Treatments in this research are the cultivation of K. alvarezii and K. striatus. Cultivation was carried out at Ekas Bay. Analysis of seaweed carrageenan was carried out in the Laboratory of Fish Production and Reproduction, Aquaculture Study Program, Faculty of Agriculture, Mataram University. The result of this research is K. striatus has a higher absolute weight of 154 g compared to K. alvarezii seaweed which is 72 g. The specific growth rate K. striatus higher at 2,98 % / day compared to K. alvarezii is 1, 98 % / day. The yield of carrageenan of K. alvarezii is 1,95% and K. striatus 0,88%. Antioxidant of K. alvarezii is 5,46 % and K. striatus is 7,42%. Chlorophyll K. alvarezii is 5,77 mg/l and K. striatus is 3,51 mg/l. The conclusion of this study is the growth of K. striatus is faster than K. alvarezii.

Comparison of two cultivation methods for domesticating wild red algal eucheumatoids for use in the seaweed industry

AbstractEucheumatoid cultivation is an important alternative livelihood for small-scale farmers in coastal areas in east Malaysia. Over the last 50 years, the same clones of the red eucheumatoid Kappaphycus alvarezii and Kappaphycus striatus have been vegetatively propagated for cultivation resulting in low genetic diversity. This has made the cultivars more vulnerable to pests and diseases, which has been further exacerbated by climate change. There is an urgent need, therefore, to develop new cultivars that are resilient to pests and diseases, as well as environmental change. In this study, wild eucheumatoids were collected from four regions in Semporna, East Malaysia: Kerindingan, Sibuhun, Sebangkat and Omadal. These eucheumatoids were then grown at a commercial seaweed farm in Silungun, Semporna using two methods: i) tie-tie and ii) basket net for 60 days and their performance was evaluated based on growth and survival rates. A higher mean specific growth rate (SGR) was recorded by wild-collected Kappaphycus spp. (2.15 ± 1.90% day−1) and Eucheuma denticulatum (2.83 ± 3.27% day−1) when tie-tie was used. However, survival of the wild-collected eucheumatoids was better with the basket net, which led to a reduction in grazing and prevented detachment from culture lines. Of 212 original individuals, 72 survived throughout the study, despite the prevalence of pests and ice-ice disease. Of these, 46.15% Kappaphycus spp. and 50.75% E. denticulatum survived when cultivated using the basket net and 17.20% Kappaphycus spp. and 30.77% E. denticulatum survived when cultivated using tie-tie. The mean SGR and survival rate were significantly correlated with temperature, salinity, pH, current velocity and rainfall (p < 0.05). The surviving wild-collected Kappaphycus spp. and E. denticulatum have the potential to be developed into new cultivars for possible commercial use.

Ice-Ice Disease Prevalence and Intensity in Eucheumatoid Seaweed Farms: Seasonal Variability and Relationship with the Physicochemical and Meteorological Parameters.

Since its initial report in the Philippines in 1981, ice-ice disease (IID) remains a substantial threat to the sustainability of eucheumatoid seaweed production. However, comprehensive investigations into the prevalence, intensity, and potential relationships with physicochemical and meteorological parameters are limited, particularly in open-sea farms. This is the first study to conduct a 12-month monitoring of IID prevalence and intensity in eucheumatoid seaweed farms in Tawi-Tawi, Philippines. The research aimed to elucidate seasonal variations and potential associations with physicochemical and meteorological parameters. The findings revealed significant seasonal variations in IID prevalence, with a higher incidence observed during the dry season compared to the wet season. Additionally, deep-water farms exhibited significantly higher prevalence and ice-ice spot numbers per bundle compared to shallow-water farms. Furthermore, Kappaphycus striatus displayed a significantly greater ice-ice spot length per bundle compared to K. alvarezii. Notably, no interaction effects were observed among season, species, and depth. Interestingly, while no correlations were found between ice-ice disease and most measured physicochemical and meteorological parameters (temperature, salinity, pH, water current velocity, wind speed) or nutrient concentrations (phosphate, nitrate, nitrite), an inverse correlation (p < 0.05) emerged between ammonium levels and IID intensity parameters (number and length of ice-ice spot per bundle). Moreover, a positive correlation was observed between monthly rainfall and IID intensity. These findings offer valuable insights into the dynamics of IID in open-sea eucheumatoid seaweed (Kappaphycus) farming, highlighting the influence of seasonality, depth, and species susceptibility, as well as the relationship between IID severity and ammonium levels and rainfall.

Enhancing carrageenan-based capsule shell formulation from kappaphycus striatum for accelerated disintegration time with multiple disintegrant

Abstract Recently, seaweed-based capsule shells have become more popular because of their reliable quality and animal-free source. But these shells’ prolonged disintegration times are a common problem. This research aims to look for formulations with disintegrant substitution or a combination of several disintegrants to obtain capsule shells that disintegrate quickly. Several studies have explored the incorporation of additional disintegrants such as Polyvinylpyrrolidone (PVP) K-30, Sodium starch glycolate (primogel), Croscarmellose sodium (SSC), and Sodium carboxymethylcellulose (Na-CMC) to address this challenge. The study investigates various combinations of disintegrants in the formulation of capsule shells to achieve rapid disintegration time. The variation in composition of disintegrants was determined using Simplex Lattice Design (SLD) in Design Expert® 13.0.12. Balancing the desirable characteristics of quick disintegration with other factors posed a significant challenge. All types of disintegrants exerted a notable influence on the response variables. To achieve a substantial reduction in disintegration time, the utilization of primogel is strongly recommended. However, it should be noted that primogel contains minerals that do not disintegrate, resulting in an elevated ash content. In contrast, PVP K-30 demonstrates promising performance but falls slightly short of primogel’s efficacy in accelerating disintegration. Additionally, PVP K-30 exhibits a marked advantage in minimizing ash content within the capsule shell. Optimization results indicate that a combination of PVP K-30 and primogel yields a capsule shell with the fastest disintegration time, approximately 23.908 minutes, while maintaining a minimal ash content of 10.487%.

Temporal variation in the incidence of seaweed health problems affecting farmed Kappaphycus striatus in relation to environmental conditions in shallow waters

Temporal variation in the incidence of seaweed health problems affecting farmed Kappaphycus striatus in relation to environmental conditions in shallow waters

Selection of fast-growing seaweed cultivars in Palawan, Philippines

Seaweed farming in Palawan currently involves different local cultivars. At least 12 of these cultivars were successfully grown in an indoor facility employing the branch culture techniques and were sea-out planted in Puerto Princesa Bay since 2015. Six of these cultivars yielded relatively high daily growth rates and were selected for the year-round field-testing experiment to compare the growth rates among cultivars and species, between farming sites, and across seasons from 01 July 2021 until 15 August 2022. Monitoring of cultivars’ daily growth rates (DGRs) was conducted in 100 m2 experimental floating monoline plots in Green Island and Sitio Amogues of the municipalities of Roxas and Taytay, Palawan, respectively. Findings revealed that seaweed DGRs significantly varied among cultivars and species (p = 0.001; p = 0.008). The “spinosum” brown from Puerto Princesa and “sacol” green from Green Island, Roxas had higher DGRs, 4.28% and 4.10%, respectively. Grouping the cultivars per species, the cultivars of Eucheuma denticulatum (L. Burmann) Collins &amp; Hervey had higher DGRs compared to Kappaphycus striatus (F. Schmitz) L. M. Liao and Kappaphycus alvarezii (Doty) L. M. Liao. Spatial and seasonal variabilities in cultivar DGRs were also evident. Four cultivars obtained significantly different DGRs between planting sites. The “tambalang” (p = 0.010) and “magnolia” (p = 0.006) with DGRs of 3.26% and 4.08%, respectively in Green Island Roxas, while the “spinosum” brown from Puerto Princesa (p &lt; 0.001; 4.86% DGR) and San Vicente (p &lt; 0.001; 4.45% DGR) in Amogues, Taytay. Three cultivars in Green Island, Roxas, obtained significantly higher DGRs during the wet season. These were the “tambalang” (p = 0.000; 3.98% DGR), “magnolia” (p = 0.000; 4.57% DGR), and “spinosum”-brown from Puerto Princesa (p = 0.006; 5.23% DGR). In Amogues, Taytay, all six cultivars obtained significantly higher DGRs during the wet season: “tambalang” (p = 0.210; 3.17% DGR); “lakatan” (p = 0.004; 2.69% DGR); “spinosum” brown from Puerto Princesa (p = 0.00; 3.97% DGR); and San Vicente (p = 0.00; 3.39% DGR). A cropping calendar that indicates the fast-growing cultivars to be planted at a particular site and season is provided in this study. This information shall aid local farmers in cultivar selection towards a sustainable seaweed farm management in Palawan.

Niche comparison and range shifts for two Kappaphycus species in the Indo-Pacific Ocean under climate change

Nowadays, eucheumatoids lead the rankings in globally cultivated seaweed production, including the seaweeds Kappaphycus alvarezii and Kappaphycus striatus. Eucheumatoids have declined in biomass over recent years, and climate change is regarded as one of the important factors. Thus, it is urgent to investigate the range dynamics of Kappaphycus under climate change. Considering its high practical relevance for conserving biodiversity, the niche conservatism hypothesis was tested between the two species through ecological niche modeling (ENM), ordination, and hypervolume approach which quantify the extent of niche overlap. In this study, we sifted the best-performing algorithm - Maxent and tuned parameters for fitting the distribution of both Kappaphycus species, compared their geographical distribution patterns, and predicted their range dynamics under climate change. All three methodological approaches indicated significant niche differences in both geographical and environmental space between the two Kappaphycus species. Our models predicted that range shifts mainly induced by rising sea surface temperature are likely to differ between two Kappaphycus species, with K. striatus suffering much range contraction (359,448 km2 in 2100s RCP8.5). By the year 2100, both Kappaphycus species are forecast to lose suitable habitats along most of the coastline of Southeast Asia under the RCP8.5 scenario. K. alvarezii is predicted to expand its distributions (96,429 km2) under the RCP2.6 scenario by the year 2100, suggesting resilience to mild global warming. Our study enhances the understanding of Kappaphycus aquaculture, and is conducive to the sustainable development of tropical seaweed by stressing the importance of conservation and investigation under climate change.

Evaluation of Different Culture Methods on The Growth Performance of Seaweed (Kappaphycus striatum) in Pelakak Village Waters Lingga District

The seaweed culture activities are relatively new and only few people perform them in Lingga District. Specifically, Kappaphycus striatum has recently been cultured for the last three culture periods. This condition causes the seaweed culturists have no appropriate data associated with a proper culture method, following the water characteristics around the culture area. A study regarding the different culture methods on the growth performance of K. striatum in Pelakak Village waters, Lingga District, Riau Islands has never been reported. This study aimed to determine the effect of different culture methods on the growth performance of Kappaphycus striatum seaweed. This study used a completely randomized block design with three treatments and three replications, namely bottom method (P1), off-bottom (P2), and longline method (P3). There were 351 seaweed seeds with 100 g weight per each seed, that are placed in nine culture plots. The culture plot was constructed as a 4 m × 1.5 m square with wooden stakes at both ends and polyethylene ropes installed at a distance of 0.5 m. Each rope stretch was tied at 0.3 m distance for seed planting. Parameters observed in this study were absolute growth rate, specific growth rate, and production rate of the seaweed. The results showed that the absolute growth rate, specific growth rate, and production rate were affected by the culture method (p&lt;0.05). The seaweed group reared in a longline method (P3) obtained the best results, compared to other methods, at 2.34% per day for specific growth rate and 245.7 g/m2 for production rate. Therefore, the longline method can be applied in the Pelakak Village waters, Lingga District.

Application of kajarula technology to the productivity of seaweed Kappaphycus striatus at Tablolong Beach, West Kupang, East Nusa Tenggara

Seaweed Kappaphycus striatus is a potential marine biological resource in Indonesia, but the cultivation uses still the conventional method (long line). The decline in production yields is affected by environmental disturbances, such as pest attacks and release due to strong currents and waves, which are also not environmentally friendly. Therefore, it is necessary to develop new cultivation methods to increase seaweed productivity. This study aims to analyze the productivity of seaweed using Kajarula (Kantong Jaring Rumput Laut, also known as seaweed net bag) technology at Tablolong Beach, West Kupang, East Nusa Tenggara. The research design used for observation data was randomized pretest-posttest Control Group Design. Next, this research is a case study that includes interviews, observations, and following the process of production of seaweed using Kajarula technology. The production performance of seaweed cultivated for 42 days resulted in biomass production of 7.54 ± 0.27 kg/units with an average relative growth of 153.41 ± 10.97 %/day, a growth rate of 239.32 ± 21.95 g/day, and a total harvest of 5.82 – 7.45 kg/units. The water quality conditions in these waters are within the optimal range to support seaweed growth. The productivity of seaweed cultivation using Kajarula technology shows optimal growth and yields.

Characteristics of Rapid Visco Analyzer Carrageenan Extract with Enzymatic Pretreatment of Kappaphycus striatum

Carrageenan is a polysaccharide compound extracted from red seaweed and is widely used by food, cosmetic, and advanced materials industries because of its good properties as an environmentally friendly stabilizer. Carrageenan extraction generally uses alkaline treatment for one full day, where the treatment is to obtain carrageenan quality with good gel characteristics. The use of cellulase enzymes is thought to accelerate the desulfuration process of seaweed, where cellulase enzymes are used to break down cellulose in seaweed cell walls. By using a rapid visco analyzer (RVA), carrageenan was tested to see the pattern and viscosity value. This study aims to determine the effect of enzymatic pretreatment on the profile of carrageenan with a shorter alkalization process compared to the alkalization commonly used by the industry. The results showed that enzymatic treatment before KOH alkalization would produce a carrageenan profile with a viscosity value of 272-360 cP, whereas the NaOH alkalization only reached 19-24 cP. The results of the test using RVA showed that the addition of an enzymatic process could change the physicochemical properties, such as viscosity and gel point of the carrageenan alkalinized with KOH. However, there was no significant difference in the properties when treated by alkalization using NaOH, which can be described from the value of the gelling point of carrageenan treated by cellulose enzyme. Adding enzymes to KOH will accelerate the gelation process, which occurs at an average temperature of 42.78oC. Meanwhile, carrageenan without enzymatic addition has an average gelation value of 37.48oC.

Diseminasi Pemanfaatan Pupuk Bionik Untuk Perbaikan Performa Pertumbuhan Rumput Laut

Farming seaweed is a significant source of income since it helps coastal communities become more resilient. Due to the simple growing, harvesting, and drying methods, low degree of capital investment, and quick production cycle (1.5 months), seaweed cultivation in Tablolong Village, West Kupang District, East Nusa Tenggara Province is dominated by cultivators from coastal villages. The present issue for farmers of seaweed is the unavailability of seeds, both in terms of quantity and quality. Simple actions such as community service projects (PKM) with a focus on fertilizing activities utilizing bionic fertilizers can be taken to encourage the growth of seaweed. The method used to achieve the target of this PKM program is participatory counseling, dissemination of research results, assistance in seaweed cultivation, and monitoring during seaweed cultivation. In November 2021, PKM operations are conducted in Tablolong Village's coastal region. Through the use of bionic seaweed fertilizer, the activity's aim is to earn the partner group's production rates. After participating in PKM activities, the "Blue Sea" partner group was able to produce Kappaphycus striatum by utilizing bionic fertilizers, where the analysis results showed that the daily growth rate was 3.38% day-1, absolute growth was 176 gr and production was 2,755.62 gr m-1.

Growth rate, concentration, and quality of carrageenan in two strains of seaweed Kappaphycus striatus grown in Khanh Hoa waters

In this study, two strains of seaweed Kappaphycus striatus (Payaka brown and Sacol brown) derived from Philippines after nearly 20 years of cultivation, were cultivated in Van Phong Bay and Cam Ranh Bay (Khanh Hoa, Vietnam) to re-evaluate the growth characteristics, concentration, and quality of carrageenan. The results showed that the ecological area affects the growth (fresh weight, growth rate, dry matter accumulation rate), content, and quality of carrageenan (gel strength and viscosity) of the two seaweed strains after 2, 4, 6, 8, 10, 12 weeks of cultivation. The highest biomass of both strains was reached after 8 weeks of cultivation in Van Phong Bay and 10 weeks in Cam Ranh Bay. The fresh weight, the dry weight, and the growth rate (343.33 g, 42.67 g, 1.30%.day-1, respectively) of the Sacol brown strain were similar to that of the Payaka brown strain at the Van Phong Bay. However, the dry matter accumulation rate (12.45%) and the carrageenan content (24.50%/w) of the Sacol brown strain were highest when cultivated in Van Phong Bay. The growth rate, concentration, and quality of carrageenan in two seaweed strains in Van Phong Bay and Cam Ranh Bay were lower than before.

Inorganic nutrient enrichment of seaweed Kappaphycus: Farmers’ practices and effects on growth and ice-ice disease occurrence

Inorganic nutrient enrichment (INE) is an emerging practice among seaweed farmers in Sibutu, Tawi-Tawi, southern Philippines, as a response to the slow seaweed growth and as a control measure for the ice-ice disease. A survey on the practice of INE of Kappaphycus and a field experiment simulating the practice were conducted. From the 100 farmers, 83% practiced INE, 14% did not practice, and 3% stopped the practice. From those who practiced, 87% were using 16−20−0 fertilizer and 13% were using 14−14−14 fertilizer. Seaweeds were dipped into 8.82 g L−1 fertilizer solution for 5–60 s, piled up on a drying platform, covered with canvas overnight, and planted the following day. Seaweeds were hauled up 7–10 days post-cultivation for re-application of INE. Harvesting and/or mass propagating was done at 20 days post-planting. Respondents reported that this method increased seaweed growth and decreased ice-ice disease occurrence. For the field experiment, 8.82 g L−1(HC), 0.01 g L−1(LC), and 0.00 g L−1(UF) of 16−20−0 fertilizer concentrations were tested in Kappaphycus striatus farmed using the modified fixed-off bottom method. At 49 days post-planting, the growth of K. striatus in HC (3.75 % day−1) was significantly higher than in LC (1.82 % day−1) and in UF (1.56 % day−1). Ice-ice disease occurrence of K. striatus was significantly lower in HC (42.37%) than in LC (78.07%) and UF (77.72%). Higher growth and lower ice-ice disease were evident with INE; however, effects in farm environment and on carrageenan quality were also reported. Further, the use of inorganic commercial fertilizer in seaweed farm is discouraged by the Philippine National Standard. Thorough studies that will address these knowledge gaps are needed for science-based policy on regulation and management of use of inorganic fertilizers in Kappaphycus cultivation.

Use of Brown Seaweed Extracts as Bio-fertilizers and their Effects on the Carrageenan Yield, Ice-ice Disease Occurrence, and Growth Rate of the Red Seaweed Kappaphycus striatus

Kappaphycus striatus is one of the most important eucheumatoid species that is widely farmed worldwide. In the southern Philippines, where the initial farm was established, sluggish growth of farmed Kappaphycus species brought about by the poor quality of planting materials and extensive farming resulting in unproductive farms and frequent ice-ice outbreaks have been a hindrance in increasing the seaweed production. As a result, farmers have led to the application of inorganic fertilizers as nutrient enrichment for Kappaphycus. However, inorganic or chemical fertilizers always pose negative impacts on the environment. Hence, in this study, a preliminary investigation on the potential use of extracts of brown seaweeds Sargassum cristaefolium and Turbinaria conoides as bio-fertilizers was tested on K. striatus for their growth rate, carrageenan yield, and ice-ice disease occurrence. Seaweed liquid extracts (SLE): S. cristaefolium (SC), T. conoides (TC), combination of SC and TC (MX), and control (C) were utilized as bio-fertilizers for K. striatus. SLE-enriched K. striatus seedlings were cultivated in a seaweed farm using the fixed-off bottom method for 45 days. Results revealed that the specific growth rates of all SLE treatments were significantly higher than no SLE treatment at day 45. The percentage of ice-ice disease and the yield of carrageenan did not differ among treatments. Enrichment of K. striatus using SLE of two selected brown seaweeds before out-planting could improve growth rates while not affecting the ice-ice disease occurrence and carrageenan yield. Hence, formulated SLE from brown seaweeds S. cristaefolium and T. conoides can be used as potential bio-fertilizers for Kappaphycus cultivation.

Antibacterial potential of different red seaweed (Rhodophyta) extracts against ornamental fish pathogen Salmonella arizonae

This study evaluated the antibacterial effects of different red seaweed (Kappaphycus striatus, Eucheuma denticulatum, Hydropuntia edulis) against Salmonella arizonae that caused disease in goldfish Carassius auratus. In vitro antibacterial susceptibility was determined using a standard disc diffusion assay. Further in vivo experiments were conducted on seaweeds with the highest zone of inhibition. Results showed that K. striatus had the highest zone of inhibition with 30.9 ±0.62 mm followed by H. edulis (29.6 ±1.61 mm), and E. denticulatum (27.6 ±0.51 mm). Promisingly, the antibacterial activity of seaweeds tested was comparable with that of cefixime, trimethoprim, and novobiocin and was significantly higher than the other seven antibiotics tested in this study. Moreover, the in vivo treatment of K. striatus to S. arizonae challenged C. auratus significantly decreased the mortality; the positive control group attained 100% mortality while the treated group had 40% mortality after 10 days of post-infection. This study showed the potential use of K. striatus to control S. arizonae infection in aquarium fishes.

Effects of inorganic nutrient enrichment on the carrageenan yield, growth, and ice-ice disease occurrence of red alga Kappaphycus striatus

One of the problems in Kappaphycus farming is the slow growth in some farms due to nutrient insufficiency caused by overstocking. In the southern Philippines, most seaweed farmers practice inorganic nutrient enrichment of Kappaphycus to boost growth and decrease ice-ice disease occurrence using ammonium phosphate at an average concentration of 8.82 g L-1. In this study, experiments with Kappaphycus striatus enriched with inorganic nutrients were carried out at Pasiagan, Bongao, Tawi-Tawi, southern Philippines, using different inorganic nutrients (T1=8.82 g L-1 of urea, T2=8.82 g L-1 of phosphorus, and T3=control) within 45 days. Seaweeds were enriched in these three inorganic solutions for 30 seconds, placed into a large mat, covered with canvas, and left overnight. After 15 days, findings showed that the specific growth rates of T1 (6.99% day-1) and T3 (6.72% day-1) groups were significantly higher than the T2 (5.84% day-1) group (p&lt;0.05). Inorganic nutrient enrichment did not significantly influence the occurrence of ice-ice disease. Moreover, inorganic nutrient enrichment did not affect the carrageenan yield after 45 days. K. striatus nutrient-enriched with urea could increase growth at day 15, but no effect on the occurrence of ice-ice disease and carrageenan yield. Hence, inorganic nutrient enrichment using urea provides a positive effect to farmed K. striatus by enhancing its growth without affecting its health and carrageenan yield.

Influence of different concentrations of ammonium phosphate on nitrogen assimilation of red seaweed Kappaphycus striatus

Eucheumatoid farming is among the most popular source of livelihood for coastal dwellers, especially in the southern Philippines. Kappaphycus and Eucheuma are the two major cultured eucheumatoid species. However, seaweed farmers have been experiencing low seaweed production for the past years. The slow growth of Kappaphycus spp. in the farm is linked to extensive farming, causing nutrient depletion in the seawater. Hence, seaweed farmers in the province of Tawi-Tawi, southern Philippines, enrich their seaweeds, Kappaphycus striatus, with a wide range of inorganic nutrient solution concentrations with an average of nearly 9 g L⁻¹. To provide standard concentration (g L⁻¹) of inorganic nutrient solution for soaking before farming the seaweed, this study investigated nitrogen assimilation using the Kjeldahl method. Treatments were the concentrations of commonly used inorganic fertilizer [ammonium phosphate, (NH4)3PO4] dissolved in filtered seawater namely; T1 = 0 g L⁻¹ as control, T2 = 3 g L⁻¹, T3 = 6 g L⁻¹, and T4 = 9 g L⁻¹. Results showed that the total nitrogen (%) of T4 (0.68±0.01) and T3 (0.59±0.07) were significantly higher (p<0.05) than T2 (0.48±0.02) and T1 (0.46±0.02). This suggests that using inorganic nutrients as enrichment to K. striatus at a concentration of 6 or 9 g L⁻¹ is effective for obtaining high nitrogen assimilation. Therefore, considering the cost-effective inorganic nutrient enrichment practice, this study recommends using 6 g L⁻¹ of inorganic nutrient concentration to help seaweed farmers boost production by improving the growth performance of K. striatus, especially when planted in nutrient-depleted farms.

Vibrio and Heterotrophic Marine Bacteria Composition and Abundance in Nutrient-enriched Kappaphycus striatus

Inorganic nutrient application in Kappaphycus seaweed farming has been a practice in the southern Philippines for the past years. To investigate the inorganic nutrient’s influence on the number and assemblage of Vibrio and heterotrophic marine bacteria and on the presence of ice-ice disease-inducing bacteria in Kappaphycus striatus, a field experiment was conducted using ammonium phosphate (16-20-0) fertilizer at high concentration (HC, 8.82 g L–1), low concentration (LC, 0.01 g L–1), and control (C, 0.00 g L–1). Vibrio (VCs) and heterotrophic marine bacterial counts (HMBCs) were found similar among treatments. Based on 16S rRNA gene sequencing, isolates from source K. striatus, nutrient-enriched K. striatus (HC, LC, and C), farm seawater, and fertilizer solutions were identified as Vibrio alginolyticus (three strains), V. parahaemolyticus, V. brasiliensis, V. harveyi, Gilvimarinus chinensis, and species related to Bacillus sp. ST7, Psychrobacter sp. ST8, Enterococcus sp. ST5, Oceanobacillus sp. ST9, and Paracoccus sp. ST10. Bacillus sp. ST7 and Oceanobacillus sp. ST9 were unique and only present in HC and LC. The agarolytic activity of G. chinensis, isolated from all samples, suggests that it is an ice-ice disease-causing bacterium. The microbial community dynamics of farmed K. striatus, when enriched with inorganic nutrients, may pave way in addressing the occurrence of ice-ice disease.