Now showing items 1-7 of 7

    • Article

      Agar yield and gel strength of Gracilaria heteroclada collected from Iloilo, Central Philippines 

      MRJ Luhan - Botanica Marina, 1992 - Walter de Gruyter
      Seasonality of yield and gel strength of agar from Gracilaria heteroclada was determined. Gel strength was high (510-794 gm cm-2) during early dry season (October-March) and low (43-101 gm cm-2) during the wet season (May-August). A negative correlation exist (P ≤ 0.05) between agar yield and gel-strength.
    • Article

      Assessment of stocks of a natural Gracilaria population on Panay Island, Philippines 

      TR de Castro, NG Guanzon Jr. & MR Luhan - Botanica Marina, 1991 - Walter de Gruyter
      Two peaks in biomass were recorded from natural beds of Gracilaria sp. at Leganes, Iloilo and Batan, Aklan study sites. The major peak occurred in February 1989 for both areas. The minor peak occurred in September 1988 at Batan and October 1988 at Leganes. Highest biomass at Ivisan, Capiz occurred in May 1988. Lowest biomass was recorded in June at Batan and December 1988 at Leganes. At Ivisan, no biomass was recorded from November 1988 to February 1989. Correlation analysis showed no relationship between biomass and temperature or pH at all study sites. However, salinity was negatively correlated with biomass at Leganes and Batan. Rainfall was inversely correlated with biomass. Based on salinity data gathered from the three study sites, Gracilaria sp. is euryhaline and can tolerate a wide range of salinity. The results show a marked seasonality in the biomass of Gracilaria sp.
    • Article

      Biomass and reproductive states of Gracilaria heteroclada Zhang et Xia collected from Jaro, central Philippines 

      MRJ Luhan - Botanica Marina, 1996 - Walter de Gruyter
      Biomass production and reproductive states were investigated to determine the abundance of Gracilaria heteroclada Zhang et Xia at Jaro, central Philippines from March 1990 to February 1991. Biomass of Gracilaria heteroclada was highest in February (45 g/m2) and lowest in July (1.16 g/m2). Plant fertility was seasonal with the highest percentage of carposporphytic and tetrasporophytic plants occurring in January (48%) and in May (64%) respectively. Seawater temperature was significantly correlated with tetrasporophyte occurrence (r = 0.6586) but not with carposporophyte occurrence. There was no correlation of the occurrence of tetrasporophytes or carposporophytes with salinity or rainfall.
    • Article

      Effect of short-term immersion of Kappaphycus alvarezii (Doty) Doty in high nitrogen on the growth, nitrogen assimilation, carrageenan quality, and occurrence of “ice-ice” disease 

      MRJ Luhan, SS Avañcena & JP Mateo - Journal of Applied Phycology, 2015 - Springer Verlag
      Short-term immersion of Kappaphycus alvarezii (Doty) Doty in a high-nitrogen-containing medium was tested to increase growth, improve the quality of carrageenan, and decrease “ice-ice” disease occurrence. Tank-reared Kappaphycus were used as explants. Growth, nitrogen assimilation, carrageenan quality, and occurrence of ice-ice disease of enriched (E/N) K. alvarezii were determined. E/N and un-enriched (control) K. alvarezii were planted inside net cages in the sea. Nitrogen assimilation was monitored to determine if nitrogen was incorporated in the tissues after 12 h. Total thallus nitrogen of K. alvarezii doubled after immersion in high nitrogen. Growth rate and carrageenan yield of E/N K. alvarezii were significantly higher than those of the control. Gel strengths of E/N and the control were not significantly different. Ice-ice disease occurrence was significantly higher in the control than the enriched seaweeds. Short-term immersion of K. alvarezii in a high-nitrogen medium before outplanting increased growth rate and decreased the occurrence of “ice-ice”.
    • Article

      Gracilaria (Rhodophyta) farming in Panay, Western Visayas, Philippines 

      AQ Hurtado-Ponce, GPB Samonte, MRJ Luhan & NG Guanzon Jr. - Aquaculture, 1992 - Elsevier
      Interviews were conducted among eight Gracilaria growers in Panay, Western Visayas, Philippines from March to July (1990) using a structured questionnaire. The "rice planting" method was employed by farmers growing seaweeds in natural drainage canals and ponds. Initial harvests are made 15–60 days after planting. Higher production [ 7–14 t (dry) ha−1 year−1] are obtained from cultures in canals than in ponds [3–4 t (dry) ha−1 year−1]. The net income derived from culture in ponds is estimated at P698/crop or P6313/year (US$234/year). A higher net income of P4936/crop or P41766/year (US$1547/year) was generated from Gracilaria farming in canals. Returns on investment (ROI) from farming in ponds and canals are 39% and 908%, respectively. Payback period is 2 months in canal farming and 1.8 years in pond farming.
    • Article

      Improved growth performance of Gracilariopsis heteroclada via short-term nitrogen enrichment 

      SS Santander-Avanceña, MRJ Luhan & J Felera-Panizales - Botanica Marina, 2015 - De Gruyter
      This study examined the effect of short-term nitrogen (N) enrichment on Gracilariopsis heteroclada growth and agar quality. Planting materials were soaked in different concentrations of ammonium chloride (NH4Cl) for 6 h. Total thallus N content was highest in Gp. heteroclada enriched in 300 mg l-1 NH4Cl. Growth experiments showed that this enrichment treatment (300 mg l-1 NH4Cl for 6 h) increased the growth of Gp. heteroclada (4.22±0.09% day-1) compared with the control (3.68±0.12% day-1). Pond culture using enriched Gp. heteroclada resulted in high growth rates (6.14±0.50% day-1). No epiphyte growth was observed during either the growth experiment or the pond culture. There were no significant differences between the agar yields of the enriched (3.65±0.36%) or control (3.78±0.18%) Gp. heteroclada. Additionally, no significant differences were detected when the gel strength of the enriched (611±22 g cm-2) and control (587±11 g cm-2) Gp. heteroclada were compared. The results suggest that the short-term N enrichment method could be an alternative culture strategy to increase Gp. heteroclada production and lower farming costs.
    • Article

      Monthly variation of agar quality of some gracilarioids from the Philippines (Rhodophyta, Gracilariaceae) 

      MRJ Luhan, MSR Ferrer, J Tanaka & Y Aruga - The Philippine Scientist, 2004 - San Carlos Publications, University of San Carlos
      Species of the economically important gracilarioid seaweeds from the Philippines were studied to determine the monthly variation in agar quality. Yield, gel strength, melting and gelling temperatures, and sulfate contents were compared. Lowest agar yield was observed in Gracilaria changii in July (4.15%) and highest in Gracilariopsis heteroclada in March (20.84%). Gel strength was lowest in G. heteroclada in November (44 g cm-2) and highest in Gracilaria tenuistipitata in January (874 g cm-2). Melting temperature was lowest in G. heteroclada in November (68.7°C) and highest also in G. heteroclada in January (90.3°C). Gelling temperature was lowest at 34.4°C in G. changii and Gracilaria firma in November and December, respectively; and highest in G. heteroclada in October (45°C). Sulfate content was lowest in G. firma in November (0.16%) and highest in G. heteroclada in February (2.71%).

      The variation in the agar parameters could be due to different composition of agars of different species. Sulfate is significantly lower in Gracilaria firma. Yield is significantly higher in Gracilariopsis heteroclada. There is no significant difference in the gel strength, melting and gelling temperatures among species.