Assessment of Heavy Metal Contamination in Red Seaweeds from the Coastal Areas of Zanzibar by Using EDXRF Technique

The content of Mn, Zn, Ni, Cu, Fe, and Pb in 10 samples of Kappaphycus alvarezii (cottonii) and 10 samples of Eucheuma denticulatum (spinosum) from 15 different sites in the intertidal coastal area of Zanzibar were determined by using EDXRF. The heavy metals assessed in both species decreased in the order of Fe >Mn > Zn >Pb> Cu > Ni. In general, the cottonii samples in Unguja had significantly higher (p ≤ 0.05) concentrations of Fe, Zn, Ni, Cu and Pb than the spinosum samples, but the latter had significantly higher levels of Mn. Similarly, the cottonii samples in Pemba had significantly higher (p ≤ 0.05) concentrations of Ni, Cu and Pb than the spinosum samples, but the latter had significantly higher levels of Fe and Zn. The concentrations of heavy metals in cottonii and spinosum in the present study were noticed lower compared to publish results. The results from this study revealed that, the heavy metals contaminations in cottonii and spinosum along the coastal area in Zanzibar were mainly caused by effluents that directly flow into marine environments. Hence, serious measures should be taken to reduce the flow of waste effluents into the marine ecosystem.

Growth rate of Eucheuma denticulatum cultivated in horizontal net and vertical net

Eucheuma denticulatum is one of the most widely cultivated macroalga commodities. This commodity produces carrageenan iota as raw material for various industries. This study aims to compare the growth rate of E. denticulatum cultivated by the horizontal net (Horinet) and vertical net (Vertinet) methods. This research was conducted in September-December 2019 and located in Lakeba waters, Bau-Bau City, Southeast Sulawesi, Indonesia. The results showed that the specific growth rate of E. denticulatum seaweed cultivated with Horinet and Vertinet was significantly different. The growth of the thallus at an initial weight of 20 g developed to 67 g and 112.5 g as viewed with a horinet and vertnet, respectively. The specific growth rates of these two methods were 5.01 and 6.59%/day using vertinet and horinet, respectively. Based on the results of the t-test showed that the use of the two methods were significantly different by 0.46 and 0.36 (P<0.05) on the specific growth rate of E. denticulatum seaweed. Both of these methods can be used to cultivate seaweed with good results. However, these two methods have differences in the growth results obtained.

The existence of epiphyte on thallus Eucheuma denticulatum (Rhodophyceae) in varying depths cultivated with vertical net method

The existence of macroepiphyte is one of the issues seaweed farmers often face. This research aims to explore the existence of macroepiphyte attached to seaweed Eucheuma denticulatum at varying depths using vertical net method. Research found that the highest and the lowest velocity of macroepiphyte on day -10 in the depth of 50 cm and 200 cm is 248,4 and 121,28 ind/m2/day. On day-20, in the depth of 100 cm and 200 cm is 333,54 and 270,01 ind/m2/day. The most dominating macroepiphyte in the attachment velocity is C. Crasa. Physical and chemical parameter showed around 29o-30oC. Current velocity 0,050-0,067 m/sec. Brightness 92%. Salinity 30-33‰. Nitrate 0,237-0,0416 mg/L. Phosphate 0,0015-0,0036 mg/L. Dissolved oxygen 5,7-6,2 mg/L. The obtained optimum environmental parameter and the type of the macroepiphyte attachment did not show any significant negative effect to the growth of E. denticulatum.

Co-existence of Epiphytes on Eucheuma Denticulatum (Rhodophyceae) in Varying Depths Cultivated with Verti Net Method

The existence of macroepiphytes is one of the issues seaweed farmers often face. This research aimed to explore the co-existence of macroepiphytes with seaweed Eucheuma denticulatum at varying depths using verti net method. Results showed that the highest and the lowest density of macroepiphyte were obtained on day -10 in the depth of 50 cm and 200 cm at 248,4 and 121,28 ind/m2/day, respectively. On day-20, in the depth of 100 cm and 200 cm the densities were 333,54 and 270,01 ind/m2/day, respectively. The most dominant macroepiphyte y is Chatomorpha crasa. Physical and chemical parameters showed a temperature of 29°-30°C, current velocity of 0,050-0,067 m/sec, brightness 92%, salinity 30-33‰, nitrate 0,237-0,0416 mg/L, phosphate 0,0015-0,0036 mg/L and dissolved oxygen 5,7-6,2 mg/L. The obtained optimum environmental parameters and the type of the macroepiphytes did not show any significant negative effect on the growth of E. denticulatum.

Assessment of genetic diversity within eucheumatoid cultivars in east Sabah, Malaysia

Studies have shown that cultivars of the carrageenophytes Kappaphycus and Eucheuma are clones of a limited number of strains originally domesticated from wild populations. For the development and selection of new cultivars, it is important that a comprehensive record of available variants exists. This study was conducted to provide up-to-date analysis and compilation of the current state of cultivars as the last list of cultivars was compiled nearly a decade ago. The present study analyzed the cox2–3 spacer and cox1 (1356 bp) genetic diversity of cultivars collected from 2019 to 2020 from the east coast of Sabah where the seaweed farms are concentrated. These data were compared with cultivars reported from 2010 to 2012 to assess changes, if any, to the gene pool of farmed eucheumatoid in Malaysia. Kappaphycus alvarezii, K. striatus, and K. malesianus are currently cultivated while Eucheuma denticulatum is no longer an important cultivar compared to a decade ago, probably due to its lower price. Analysis of the cox2–3 spacer revealed a new haplotype, LBT10, and, by including published GenBank data, a further four previously unnamed haplotypes were recognized from Sabah. This study confirms that there is a limited gene pool within cultivars in Malaysia and suggests the need for new or genetically diverse cultivars which can adapt to a changing environment, to ensure a more sustainable carrageenan industry.