Discover Environment (Oct 2024)

Anthropogenic nitrogen accumulation potential of Okinawa mangroves in Japan

  • Ferdouse Zaman Tanu,
  • Ko Hinokidani,
  • Satoshi Takahashi,
  • Yasuhiro Asakura,
  • Azizul Hakim,
  • Yasuhiro Nakanishi

DOI
https://doi.org/10.1007/s44274-024-00145-y
Journal volume & issue
Vol. 2, no. 1
pp. 1 – 19

Abstract

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Abstract The extent of the stable nitrogen (N) isotope ratio (δ 15N) of mangrove leaves reflects the anthropogenic N accumulation potential of mangroves. Therefore, the present study was designed to investigate the N accumulation potential of Okinawa mangroves in Japan using three ecological indicators from four mangrove watersheds. The dissolved inorganic nitrogen (DIN) concentration in mangrove creeks, the leaf δ 15N and the soil δ 15N are considered immediate indicators, short-term indicators, and long-term indicators, respectively. The four mangrove watersheds are classified into two groups, human-affected and forested mangroves, based on the relative land use ratio (%) of the watersheds. The observed values of the ecological indicators were subsequently compared between two groups of watersheds to determine the relative ecosystem conditions. The results showed that both the leaf δ 15N (0 to 9 ‰) and the soil δ 15N (1.5 to 8.0 ‰) values are significantly greater in human-affected mangroves than in forested mangroves. The DIN of creek water samples does not indicate an immediate risk of excess N input from human perturbation in mangroves. However, the significant relationships among the indicators reflect the anthropogenic N accumulation potential of mangroves in Okinawa, Japan. These findings are highly important, especially for policymakers, environmentalists, and related stakeholders, for initiating conservation and management practices for mangroves. Controlled, limited, and/or restricted human perturbation; proper management of municipal wastes; and planned use of agrochemicals upon necessity may help reduce anthropogenic N inputs in mangrove ecosystems in Okinawa.

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