© 2018 by Ting Kok+ Team

Mangrove

Survey Methods

Two representative (i.e., replicate) sites in each of the four sections (A, B, C and D) were chosen which allowed spatial comparisons within and between sections (i.e., 2 × 4 = 8 sites in total). These sampling sites were:

Section A - Ting Kok West and Ting Kok

Section B - Island House and Tolo Pond

Section C - Sai Keng and Yung Shue O

Section D - Fung Wong Wat and Lai Chi Chong

To encompass seasonal variation, surveys were be conducted in both the dry (December to March) and the wet (June to September) seasons, as seasonal variation in these fauna is expected to be important. Two temporal replicates (i.e., twice per season) were conducted at each site. The date of each temporal replicate was randomly chosen within the season. We follow the established protocols for sampling mangrove biota (Skov et al., 2002; Cannicci et al., 2009). Apart from studying the organisms inhabiting mangrove plants (i.e., arboreal organisms), we also studied the organisms inhibiting the substratum of the mangrove area (i.e., epifauna) in order to capture as many species inhabiting the mangrove as possible.

A 30 m transect was laid along the shore and three 5 m × 5 m quadrats were deployed on the landward side at 10 m intervals along the transect. To accommodate spatial variation within each site, replicate transects were established at different shore heights (i.e., high and low shore) where possible, depending on the extent and complexity of the mangrove stand (e.g., having mixture of layers of different mangrove species, or having a large mangrove area).

 

 

Arboreal organisms

Three mangrove trees in each 5 m × 5 m quadrat were randomly chosen and all the animals present on the leaves, branches, trunk and roots were identified and counted. An estimate of the density of organisms was made by multiplying the mean number of animals on the sampled trees by the number of trees in the quadrat and then dividing this value by the quadrat area (after Walthew, 1995). Algae present on the trees were only scored as present or absent and were collected and identified later in the laboratory.

Epifauna

In each 5 m × 5 m quadrat, three 0.5 m × 0.5 m quadrats were randomly deployed on the surface of the mud to sample the epifauna.  The abundance of mobile animals was counted, and the coverage of sessile organisms was estimated using a 100-point double strung 0.5 m × 0.5 m quadrat.  

Visual survey of crabs

During the surveys in the wet season, we added visual counts of epifaunal crabs by using binoculars. There were two experienced persons standing outside the 5 m x 5 m quadrat, who observed any epifaunal crabs inside the quadrat for 10 mins.  A 5-min resting period was added before the counting so as to allow the fauna within the quadrat to recover from being disturbed.  To avoid double-counting, one person was responsible for half of the 5 m x 5 m quadrat only. 

Mangrove seedlings

We measured the height of mangrove seedlings, and counted the number of leaves on each of them during the wet season, as a proxy for measuring their growth.  In each 5 m x 5 m quadrat, we tagged three seedlings (< 50 cm of height), measured their height and counted the number of leaves. 

Mangrove trees

All adult plants (height > 0.5 m) were counted within the 5 m x 5 m quadrat. At 0 m, 10 m, 20 m and 30 m along each transect, a centre point was set at a position of 2.5 m away from the quadrat. The centre point was used to divide the adjacent mangrove area intro four portions. In each portion, the tree closest to this centre point was measured for its height, stem basal diameter (calculated from the circumference at the base of each stem), and distance between the tree and the centre point. 

 

Common Species

Acorn barnacle 紋藤壺

Hexanauplia: Balanidae

Black mangrove 桐花樹

Myrsinaceae

Grey mangrove 白骨壤

Acanthaceae

Milky fiddler crab 清白招潮蟹

Decapoda: Ocypodidae

Japanese mudsnail 瘦海蜷

​Gastropoda: Batillariidae

Zoned horned shell 縱帶灘棲螺

​Gastropoda: Batillariidae

Oriental mangrove 木欖

​Rhizophoraceae

莫氏擬蟹守螺

Gastropoda: Potamididae

東京擬蟹守螺

Gastropoda: Potamididae

馬來小藤壺

Hexanauplia: Chthamalidae

加夫蛤

Bivalvia: Veneridae

Kandelia 秋茄

​Rhizophoraceae

Periwinkle 斑肋濱螺

Gastropoda: Littorinidae

Periwinkle 黑口濱螺

Gastropoda: Littorinidae

寬額大額蟹

Decapoda: Grapsidae

Nerita balteata

黑線蜑螺

Gastropoda: Neritidae 

麗彩招潮蟹

Decapoda: Ocypodidae

Common mudskipper 廣東彈塗魚

Perciformes: Gobiidae

Red-clawed crab 雙齒近相手蟹

Decapoda: Sesarmidae

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Black mangrove 欖李

​Magnoliopsida: Combretaceae

長方蟹屬

Malacostraca: Varunidae

Toothed top shell 單齒螺

Gastropoda: Trochidae

印度新脹蟹

Malacostraca: Sesarmidae

Nerita albicilla

Blotched nerite 漁舟蜒螺

Gastropoda: Neritidae

Chameleon nerite snail 矮獅蜒螺

Gastropoda: Neritidae

石磺

Gastropoda: Onchidiidae

石磺

Gastropoda: Onchidiidae

Mudsnail 亞洲小塔螺

Gastropoda: Potamididae

Sand bubbler crab 中型股窗蟹

Malacostraca: Dotillidae

Austral seablite 南方鹼蓮

Family Amaranthaceae

Giant mangrove whelk 沼澤筍光螺

Gastropoda: Batillariidae

Mud creeper 溝紋筍光螺

Gastropoda: Batillariidae

Buddhist crab 角眼切腹蟹

Malacostraca: Dotillidae

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