Hung Manh Vu^1,2 , Beatriz Estela Casareto^1,3 , Ken-ichi Hayashizaki⁴ , Laddawan Sangsawang^1,5 , Keita Toyoda³ , Lan Dinh Tran² , Yoshimi Suzuki¹

1 Graduate School of Science and Technology, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka-Shi, Shizuoka-Ken 422-8529, Japan
2 Institute of Marine Environment and Resources, Vietnam Academy of Science and Technology (VAST), 246 Danang Street, Haiphong City 180000, Vietnam
3 Research Institute of Green Science and Technology, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka-Shi, Shizuoka-Ken 422-8529, Japan
4 School of Marine Biosciences, Kitasato University, Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan
5 Marine and Coastal Resources Research and Development Center the eastern Gulf of Thailand, Pak Nam Prasae, Klaeng, Rayong Province 21170, Thailand
Author    Correspondence author
International Journal of Marine Science, 2017, Vol. 7, No. 17   doi: 10.5376/ijms.2017.07.0017
Received: 11 Apr., 2017    Accepted: 10 May, 2017    Published: 23 May, 2017

This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Vu H.M., Casareto B.E., Hayashizaki K.I., Sangsawang L., Toyoda K., Tran L.D., and Suzuki Y., 2017, Role of demersal zooplankton as a food source for higher trophic levels at Fukido Estuary, Ishigaki Island, Okinawa, Japan, International Journal of Marine Science, 7(17): 161-175 (doi: 10.5376/ijms.2017.07.0017)

Demersal zooplankton (DZ) appear in the water column at night, and are highly abundant in mangrove, seagrass, and coral reef habitats; however, few studies have discussed their role in aquatic food webs, considering different consumers and their preferences on different DZ’ size classes. This study elucidates the role of DZ as a food source for higher trophic levels in an estuarine area, particularly with respect to the food preference and size selection of their consumers. The study was conducted in the mangrove forest of Fukido Estuary and an adjacent reef lagoon (with seagrass-dominated and seagrass-coral mixture areas) on Ishigaki Island, Japan. The abundance of demersal zooplankton was 4.0, 5.4, and 11.3×10⁴ ind.m^-2 for seagrass, mangrove, and seagrass-coral mixture habitats, respectively. The lowest DZ biomass was recorded in mangroves and mainly dominated by smaller organisms, because their consumers in this habitat prefer large-sized prey. The δ¹³C and δ¹⁵N signatures showed that, in mangroves, demersal zooplankton constituted a higher proportion of the diet of fishes than in lagoon habitats; however, demersal zooplankton did not have a significant role in the diet of fishes and macroinvertebrates in the lagoon. Consistency among biomass, stomach contents, and the proportions of DZ of all size classes in the diet of mangrove fishes indicated that DZ serve as a major food source. In contrast, fishes in lagoon habitats consumed more crabs, shrimps and mollusks than DZ. In conclusion, our analytical approach allowed us to demonstrate that DZ of different body sizes serve as food sources for different consumers in different habitats of the estuarine ecosystem.

Demersal zooplankton; Biomass; Stable isotope; Mangrove; Seagrass; Seagrass-coral mixture