*aquarium net 1 piece
*dip net 1 piece
*enamel tray 1 piece
*forceps 1 pair
*plastic bucket 1 piece
*quadrat 1 piece
*trowel 1 piece
*vials, different sizes 10 pieces
for measuring physical factors
*Alcohol-in-glass-thermometer 1 piece
*compass 1 piece
*cotton thread 1 piece
*environmental comparator with light probe 1 set
*hand-held wind meter 1 set
*meter rule 1 piece
*pH paper some
*ranging poles 2 pieces
*spirit level 1 piece
*whirling hygrometer 1 piece
Methods
To determine the relative humidity
- The reservoir of the hydrometer was fully filled with water and was stoppered.
- The instrument was grasped firmly by one hand.
- It was rotated in the air steadily until both thermometers give a constant reading.
- The relative humidity was determined by finding the difference of temperature of the two bulbs and then read off from a special scale provided
To determine the wind speed.
- The hand-held wind meter was held vertically facing to the wind direction.
- The wind speed was taken where the plastic ball reached maximum height.
pH of sea water.
- The pH of sea water was measured by pH paper by dipping a piece of the paper into sea water and the colour change was observed.
- The colour change was compared with a standard scale to find out the pH value.
Measuring the profile along a transect line
- A long thread of nylon was laid down along the rocky the rocky shore. This is the transect line and the profile was surveyed along this line as well as the sampling of sea animals and plants with the use of quadrats.
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For simplicity, the set-up employed in the surveying is shown below:
- The meter was ensured to be held vertically and as deep into the rock cervices as possible.
- The spirit level was placed horizontally above the horizontal meter rule so that a true horizontal position of the rule can be ensured.
- The height difference over a meter distance between the two rulers was found out and was recorded into a data sheet. The measurement was taken at a meter interval and it went on for about 30 times until the transect line reach water.
Measuring the pattern of zonation along the transect line
- The whole length of the transect was divided into a number of zones and the length of each zone was decided.
- All the zones were assigned with number, e.g. Zone 1, Zone 2, Zone…Zone N for easy identification.
- To the same transect line, the measurement of zonation pattern was taken with a quadrant with a sheet of plastic paper starting from the seashore.
4. The number of marine organisms were found by counting within the quadrate while the data for plants are accessed by means of percentage of coverage of the plant species.
6. The species of the animals and plants found was identified with the help of reference materials.
Results and Calculations
A table showing the abiotic factors of the rocky shore at Shek O during 14:50 to 17:40
A table showing the distribution of sea animals in different zone.
Two kinds of plants are found in the rocky shore habitats, they are Caloplace(Red Algae) and Buellia(Grey Algae).
A table showing the distribution and percentage of coverage of vegetation.
The Rocky shores profiles
Discussion
Principles of the methods used in the procedures.
The whirling hydrowind meter
As the wet bulb is always filled with water, when water evaporates during the whirling action, the temperature on the bulb is lowered and it is lower than the dry-bulbed one. The difference between the reading of both the dry and wet one can be found out and there is a special scale(an accessory of the windmeter) that provide an easy and convenient way to check out the actual relative humidity.
Sampling of animals and plants along the belt transect
When it comes to study the amount and coverage area of plants of a given area, we need the technique of sampling. The meaning behind sampling is that only a small part but have significant representation of the whole with high accuracy is needed to be dealt with as it is virtually impossible to identify and count every organism in a habbit. Provided that the sample is carefully chosen and well assessed beforehand, any conclusion drawn from the findings will be representative enough and can be considered as valid. In our fieldwork, we use the transect with quadrats as our sampling method.
A quadrats is essentially a wooden frame which is foldable so that it can be carried and stored conveniently. It is placed on the rocky shore and any organisms found within the quadrats are identified and their abundance is recorded. The advantage of using a quadrats is that the wooden frame can act as a barrier to prevent the animals from moving away from the area covered by the quadrats.
One the other hand, a transect line is a string that is stretched out along the rocky shore in a straight line. Together with a quadrats, the organisms touching the line and under the area enclosed by the quadrats are counted at a regular intervals(we divided the whole length of the line into different zones). This technique is very useful where there is a transition of plants and animals across an area, especially the rocky shores in our fieldwork. As we can see that there is quite an appreciable height change along the transect, therefore, we should construct a land profile of the rocky shore to indicate the changes in level. This is particularly important as the variation of height in a rocky shore would greatly affect the abundance and distribution of any plants and animals found which constitute the zonation patterns.
In this way, we can relate the zonation observed to the variation of height to make an analysis of the result.
One point I would like to raise is that there are many domestic rubbish occupying a large area of the supertidal zone, especially inside the rock cervices which is often filled with waste plastics bottles, broken furniture, plastic bags and so on. This may more or less lower the accuracy of the profile measured and the availability of sea animals found on the shore.
I suppose it is the rubbish from the sea which is brought to shore by water current and then acuminate there.
An analysis of the result obtained
The rocky shore can be divided into three regions, namely subtidal zone, intertidal zone and the supertidal zone. The first one is always covered with sea water. The second one is a region which is more exposed but subjected to tidal actions while the last one is highest in altitude which have little contact with sea water.
From the result, it was found that both the algae and the sea animals are mainly confined to the subtidal zone and intertidal zone. There is none on the supertidal zone. Red algae occupy a lower shore than the grey one as the red algae absorb light within the blue-green region, which has a longer wavelength and a larger penetrating power.
Filter feeding marine animals like the L.Brevicala are mainly confined to subtidal zone as they rely on sea water to filter plankton for feeding. Others which belong to the class mollusca, like the limpet and crustaceans, like the barnacle possess anchorage structures to attach themselves to the rock surface can survive in the intertidal zone. They either use their radula or filter-feeding structures to feed.
Adaptive features exhibit by the organisms found
As the rocky shore is constantly under the strong tidal action, animals inhibiting on the shore is always subjected to the threat of being washed away, desiccation, fluctuation of salinity and temperature. They should therefore have some means to protect themselves from the threats in order to survive.
Here is a list of sea animals found and some general external features and their adaptations to the rocky shore environment of each of them was discussed below:
Chitons
Chitons are found under rocks or in crevices in tidal pools. They have a shell of eight overlapping plates which are surrounded by a leathery ring. Their eyes are sensitive to light and they shelter beneath the rocks during the day and feed at night.
Chitons cling to rocks by using suction. Their calcareous shell is so hard and strong that are hard to be removed from the rocks. This not only prevents them from being washed away by strong tidal actions but also makes them harder to be a prey of predators.
They are mostly herbivores and eat tiny plants (algae) which they scrape off rocks with their rasping tongue or radula
Limpets
Limpets can be found clinging to rocks in the tide pools. They eat algae, which they scrape off rocks by using their rasp like tongues called radula. Limpets like to be kept moist. When the tide goes out they tuck themselves into their shells and hide away.
They pull themselves tight against the rock so they do not loose moisture in the hot sun or drying wind. It is quite interesting to hear that limpets like to live in the same place. They always come back to the same place after they have finished grazing.
Hermit crabs
Hermit crabs are very common in rock pools. They do not possess a tough protective skin like other crustaceans and they find empty shells to live in. When they grow larger in such an extent that their the shells can’t accommodate any more, they move out to find a bigger one.
It is easy to find them scampering along the bottom of the pool scavenging for food. If you touch the shell they will quickly hide inside until it is safe to come out. It should be noted that Hermit crabs are not true crabs.
Crab
A crab shell is called a carapace and it protects its soft body from predators. Its large claws are used for catching and killing prey.
Crabs have five pairs of jointed legs and they all have the power of regeneration.If a crab looses a leg it can regenerate a new one!
In addition, crabs eyes are carried on stalks. They use gills for gaseous exchange and they take water in to the gill chamber under the carapace through pairs of slits near the base of their legs. Water passes out through openings in the mouth frame.
As crabs grow too large for their skeleton, they moult. The skeleton splits and the crab carefully edges its way out. Its new soft skeleton is underneath.
Sea anemones
These interesting creatures live on the sheltered sides of rocks. They like to be protected from the hot sun and drying winds. Anemones use their tentacles to grasp their preys. The tentacles are covered with stinging cells called nematoblast which can shoot out nematocyst to paralyse their prey.
In addition, the mouth is a fleshy opening in the center of the ring of tentacles. Anemones sting their prey and swallow it whole. They trap shrimp and small fish which come near.
Conclusion
The most noticeable thing about rocky shores is the zonation of organisms. This is common to rocky shores all over the world. The particular species of organism in each zone may vary with different climates and levels of wave and air exposure, but all show special adaptations to living in this area, and the basic structure is recognisable on most rocky shore environments.
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