| Project Duration | 2014-12-31 ~ 2015-12-30 |
|---|---|
| Research Title | Ecological Survey of Macroalgae in Dongsha Atoll |
| Contracted Organization | National Changhua University of Education |
| Principal Investigator | Wang Wei-Long |
| Co-Principal Investigator | Liu Shao-Lun |
| Project Participants | Tsai Chia-Ying, Chen Pin-Chen, Li Zong-Xuan, Chung Dan-Ya, Lin Yan-Bo, Li Zi-Jin, Hong Yu-Hsin, Liang You-Fang, Huang Yu-Chao, Chen Zhi-An |
| Keywords | Dongsha Atoll, macroalgae, new records |
| Abstract | This study conducted nine macroalgal sampling surveys between December 2013 and March 2015 at nine sites around Dongsha Island and within the atoll lagoon, using snorkeling and SCUBA diving methods. A total of 122 species of macroalgae were identified, including 58 red algae species (the most abundant group), 35 green algae species, 25 brown algae species, and 4 cyanobacteria species. Among these, 55 species were newly recorded for the Dongsha waters, comprising 4 cyanobacteria, 30 red algae, 11 brown algae, and 10 green algae species. Analysis of species richness showed that sites around Dongsha Island had a higher average number of macroalgal species (approximately 20–24 species), with site DI07 on the southern side of Dongsha Island recording the highest number (about 24 species). In contrast, the atoll lagoon sites had fewer species on average (approximately 6–15 species), with site K03 in the southern lagoon recording the highest number (about 15 species). Analysis of genera and species numbers revealed slight seasonal variation, with higher species richness in winter and early spring, followed by a gradual decline into spring and summer. The total number of macroalgae peaked in February 2014 (late winter) at 51 genera and 79 species, then gradually decreased, before rising again to 44 genera and 65 species in March 2015 (early spring). Dominant species varied among sites and months. In winter, dominant taxa included the cyanobacterium Lyngbya majuscula; red algae such as Eucheuma denticulatum, Coelothrix irregularis, edible Gracilaria, and Ceramium spp.; brown algae such as Lobophora variegata and Padina australis; and green algae including Caulerpa serrulata, C. racemosa, C. taxifolia, Halimeda opuntia, and Ulva flexuosa. In spring, while Lyngbya majuscula, Eucheuma denticulatum, Caulerpa racemosa, and C. serrulata remained dominant, other dominant species shifted to red algae such as Asparagopsis, Centroceras, and various Gelidium species, as well as the green alga Caulerpa denticulata. Environmental data analysis showed that water temperatures ranged from 19.1 to 31.0 °C, salinity from 28.4 to 36.0 psu, and pH from 8.01 to 9.07. Nutrient concentrations were as follows: nitrate (NO3-N) 0.001–0.026 ppm, nitrite (NO2-N) 0.0017–0.0113 ppm, ammonia (NH3-N) 0.01–0.034 ppm, and phosphate (PO4-P) 0.001–0.085 ppm. Cluster analysis of macroalgal composition and environmental factors across months and sites indicated two main groups: sites around Dongsha Island and sites within the atoll lagoon. This suggests that habitat type is likely a major factor influencing macroalgal community composition. |
2015, Dongsha Atoll, Macroalgae, New records