The FORAM Index (FI) as an indicator of environmental perturbations in coral ecosystems of Hong Kong, China

Maritime, industrial, urban expansion, and touristic activities have been on the rise in Hong Kong, China. These impact the fringing coral ecosystems with nutrient-rich sewages, industrial effluents and surface run-offs through network of rivers and canals. The FORAM Index (FI), is a single metric index that evaluates the health status of reef environments by combining the abundance ratios of the heterotrophic, opportunistic, and symbiont-bearing taxa in a specialized relationship. Four regions of Hong Kong were investigated— Northeastern Sai Kung, East Sai Kung, Lantau and Southern Hong Kong. A total of 61 genera of habitat specific benthic foraminifera were identified. The stress-tolerant heterotrophs were abundant at all stations. The symbiont-bearing taxa, dominated by Amphistegina which share similar ecosystem functions with the corals, are abundant at few sites in East Sai Kung and Northeastern Sai Kung regions. The opportunistic taxa, strongly represented by Elphidium and Ammonia, were recorded at all sites. East Sai Kung region has two stations with FI > 4, meaning that the environment can support coral vitality, while the rest are intermediate (2 ≤ FI< 4). In Northeastern Sai Kung, only two stations have FI < 2. while the remaining three stations are intermediate. All Lantau stations are below FI = 2, and cannot support coral recovery. Majority of the Southern Hong Kong sample stations are below FI = 2. The FI has shown that all the sites are at different stages of impacts and the majority may not be suitable for coral recovery and growth. Therefore, continuous assessment and monitoring are required to keep the ecosystem functioning.