Characteristics of mangrove ecosystems in Weda Bay: Environment, Vegetation, and Aboveground Carbon Stocks
Suyadi
Lembaga Ilmu Pengetahuan Indonesia
Abstract
Weda Bay is one of mega-biodiversity spots in Indonesia, for example it is one of the largest mangrove habitat in North Maluku. However, data and information of mangrove vegetation and its ecosystem services particularly carbon stocks are lacking. Mangroves were sampled using transects in five sites of mangroves across Weda Bay. The transects extended from seaward to landward to cover all vegetation variation. Environmental data (water and substrate) were collected using Conductivity Temperature and Depth (CTD), Dissolved Oxygen (DO) meter, and sediment core. The objective is to identify characteristics of mangrove vegetation, environment, and it ecosystem services in term of aboveground carbon stocks. The study found 17 species of mangrove and the dominant species was Rhizophora apiculata, followed by Bruguiera gymnorrhiza. The importance index of those species were high (Importance index > 45) in the four sites (Yevi, Imam, Halmahera, and Bori-Bori), but Rhizophora Stylosa was important species in Dadawe site (Importance index: 58). The density of mangrove tree was 987 stem ha-1 and sapling was 1,470 stem ha-1. Substrate of mangrove did not vary significantly with distance from the seaward which mainly dominated by mud and clay (3.9 - 63 µm). Mean water temperature in the mangrove area was 29.3℃, salinity 34.1 psu, mean water suspension was 46 mg l-1, mean dissolved oxygen was 3.2 mg l-1, and water current was 10 m s-1. Aboveground carbon stocks were considerable (mean 154 Mg C ha-1, maximum 425 Mg C ha-1). Change in aboveground carbon stocks over the distance from the seaward edge to landward edge was not significantly different. The study also observed mangrove deforestation, exploitation (fire wood), and plastic pollution in all study sites. These data indicate that the environment (water and substrate) of Weda Bay is suitable for mangroves. However, this ecosystem faced some threats such as mangrove deforestation, wood exploitation, and pollution. It can be estimate that mangrove deforestation generates emissions up to 1,546,599 Mg CO2e ha-1 or equivalent with the loss of carbon market price up to US$ 108 million ha-1. These values exclude belowground carbon stocks and other function and services of mangroves. Better mangrove management e.g. reducing deforestation and pollution are required to protect the functions and ecosystem services of mangroves.
Keywords: mangrove vegetation, mangrove environment, carbon stocks, Weda Bay
Topic: Coastal and Ocean Dynamics