Soft shore

Survey Methods

Eight soft shore sites in the Tolo area were studied, including:

Section A - Ting Kok West and Ting Kok

Section B - Tolo Pond and Wu Kai Sha

Section C - Sai Keng and Starfish Bay

Section D - Fung Wong Wat and Lai Chi Chong

At each site, three 50 m transects was positioned at three tidal heights (low = 1.15 m +C.D., mid = 1.45 m +C.D. and high = 1.75 m +C.D.). During the wet season, an extra transect (extra low = 0.7 m +C.D.) was added to increase our sampling efforts at each site. Two temporal replicates were conducted on each chosen site. The sequence of sampling on each site was randomized to minimize selection bias.

Sediment analysis

At each shore height, two samples of surface (of 8.5 cm diameter and 5 cm depth) and bottom (of 8.5 cm diameter and 15 cm depth) sediments were collected randomly along the transect for substrate analysis (Leung et al., 2006). Particle size of each sediment sample was determined using the wet-sieving method using seven particle size classes (<0.063, 0.063, 0.125, 0.25, 0.5, 1.0 and 2.0 mm). For determining the total organic matter (TOM) content, ~10 g of each dried sediment samples were weighed and put into crucibles, respectively, and burned in a furnace. The sediment samples were ignited for 200 oC for 60 minutes followed by 500 oC for 480 minutes (i.e., 8 hours). After that, TOM content was calculated by percentage of weight loss.

Epifauna and infauna

Using the transects laid at three different, fixed tidal heights mentioned above, fifteen 0.1 square metre quadrats were placed every three meters at each height to study the abundance of sessile and slow-moving macrobenthos (≥ 0.5 mm). The sediment in the quadrat was excavated to a depth of around 20 cm along with the epifauna. Epifauna and infauna was not examined separately due to time constraints. All excavated sediments were sieved through a 0.5 mm sieve and the sieved animal samples will be preserved in 80% ethanol. The samples were then identified and quantified in laboratory. The sampling effort was adequate to cover a representative estimation of the species abundance.

Rapid assessment

Rapid assessment was also conducted at each site to determine the abundance of fast moving epifaunal macrobenthos. A quick search for fast moving animals was conducted at each shore height before laying down the transect. Animals were identified on site and their relative abundance of occurrence was recorded. Animals that could be identified be eye were collected and identified in the laboratory.