2019/06/14
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Sheltered Sandy Shore

Habitat

Coastal Organisms 
 
Marine Organisms
 

Habitat

Sandy shores can be divided into an exposed or a sheltered type, depending on the strength of wave action the shore receives.  The sandy shore in Ting Kok is a sheltered type, which means it receives weaker wave action, and has a substratum composed of sand with smaller particle size as compared to an exposed sandy shore.
 

 
With fine sand particles and stable condition, the substratum can retain more moisture in the sheltered shore which results in containing higher species diversity and a large quantity of organisms than those of the exposed shore.  
 
Nevertheless, the distribution of species is determined by ecological gradients of shore. Ecological gradients include vertical gradient, horizontal gradient and depth gradient.

 

i) Vertical gradient is caused by tidal cycles.  Sand in the lower intertidal zone only dries out on the surface during low tides, whilst sand in the upper intertidal zone dries out to a greater depth for a longer period.  Being uncovered by tides, the upper intertidal zone normally exposes to air and experiences more extreme temperature change than the lower intertidal zone.  Therefore, organisms inhabiting in the upper intertidal zone are expected to be more capable of coping with water stress.
 
ii) Horizontal gradient is created by local topography and oceanography.
 
iii) Depth gradient is determined by oxygen availability and particle sizes of the sandy shore.  Generally speaking, oxygen availability decreases as you go deeper to the ground.  Sand gets darken in colour is due to the action of anaerobic bacteria.

In addition, boulders and rubbles patchily scatter on the sandy flats in Ting Kok, forming scattered gravel shores along the sandy shore. 
 

At first glance, this type of shore may look dull.  Nevertheless, if you observe carefully, you will discover a dynamic habitat.  No matter on the hard surfaces of boulders and rubbles or the crevices and spaces under them, boulders and rubbles can provide homes and refuge for different kinds of organism to escape from hot sun, dehydration and hide from predators, for instance, the shore birds. 

Brachidontes variabilis

 

Common Rock Oyster
Saccostrea cucullata

     

Barnacle
Amphibalanus amphitrite

 

Isognomon ephippium

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Coastal Organisms

Organisms on sandy shores can be categorised into three groups by their ways of habitation: 

i) Surface dwellers, which are collectively referred to as “epifauna”.  Most of the epifauna are mobile crustaceans such as crabs.  They are usually scavengers, feeding on dead animals or detritus on top of the sand.  Some of the epifauna possess a comprehensive camouflage to mask themselves from predators and preys.

 

 Metopograpsus frontalis

 

Topshell
Monodonta labio

 

Soldier Crab
Mictyris sp.

         

 Fiddler Crab
Paraleptuca splendida

 

Fiddler Crab
Gelasimus borealis

 

Ghost Crab
Ocypode ceratophthalmus 
         

Buddhist Crab
Tmethypocoelis ceratophora

 

Swimming Crab
Thalamita crenata

 

Sesarmine Crab
Parasesarma bidens

         

Sesarmine Crab
Parasesarma pictum

 

Turban Shell
 Lunella coronata  

 

Hermit Crab
Clibanarius longitarsus

  
 

ii) Burrowers, which are collectively known as infauna, including both shallow and deep burrowers.  Most infauna are bivalves and worms.

 

Anomalodiscus squamosus

 

Coecella sp.

 

Ruditapes sp.

         

Anadara cornea

 

Gafrarium sp.

 

Marcia sp.

         

Siphonosoma cumanense

 

Innkeeper Worm
Ochetostoma erythrogrammon

   
iii) Temporary burrowers, which may be surface dwellers or burrowers, depending on the phases of tidal cycle.

 

Terebralia sulcata

 

Batillaria sp.

 

Pirenella sp.

         

Dog Whelk
Reishia clavigera

 

Reticunassa festivus

 

Clithon sp.


No matter living on the sand surface or within the sand, animals have to face different challenges.    
 
Living on the sand surface allows animals to search for food or mates easily.  However, since the shore is exposed to air and intense solar radiation at low tide, organisms are at the risk of water loss and heat stress.  They are also easier to be washed away by waves.  
 
Oppositely, organisms living within the sand are safe from wave action, predation and desiccation during low tides.  However, they have to face challenges in finding food, mates and enough oxygen for survival. 

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Marine Organisms

Pistol Shrimp
Alpheus brevicristatus

 

Green Urchin
Salmacis sphaeroides

 

Starfish
Luidia maculata

         

Jellyfish
 Mastigias papua

 

Starfish 
Archaster typicus

 

Sea Cucumber
 Holothuria leucospilota

         

Flesh-Crested Blenny
 
Omobranchus fasciolatoceps

 

Spotted Seahorse
 Hippocampus kuda

 

Sea Squirt
 Styela plicata

         

Pipefish
Hippichthys
sp.

 

Striped Sweetlips
 Diagramma pictum

 

Hong Kong Pufferfish
Takifugu alboplumbeus

         

Striped Poison-fang Blenny Mimic
Petroscirtes breviceps

 

Sleepy Goby
Psammogobius biocellatus

 

Freckled Goatfish
Upeneus tragula  

         

Slender Sliver-biddy
Gerres oblongus

 

Butterfly Ray
Gymnura sp.

 

Fan-bellied Leatherjacket
Monacanthus chinensis

         

Broadbanded Cardinalfish
Ostorhinchus fasciatus

 

Longhorn Cowfish
Lactoria cornuta

 

Orange-black Dragonet
Dactylopus kuiteri