THE GENERAL PURPOSE OF FIELD TRIPS :
1. They can provide students with experiences that cannot be duplicated in the school but are nonetheless an integral part of the general knowledge which are worthwhile for the students.
2. They can enable teachers to expand students' learning beyond the walls of classroom into the vast community outside.
THE AIM OF THIS PARTICULAR FIELD TRIP :
1. To understand and learn the various types of basic field work techniques after the self-experience during the field trip.
2. To investigate and study the ecological environment of the rocky shore habitat.
3. To find out the major organisms present and their adaptations to the environment.
4. To find out the effect of the main physical factors on the distribution of organisms and the interrelationships existing among organisms.
MATERIALS REQUIRED AND BROUGHT(INCLUDING CHEMICALS)
1. Pencils 2. Note papers 3. Cap 4. Sunglasses 5. Hand lens 6. Thermometer 7. 1 m2 quadrat 8. Transect line 9. Plastic bags and vials 10. Compass 11. Drinks or distilled water 12. pH papers 13. A light string 14. Hydrometer instrument for measuring salinity 15. Long ruler 16. Long plastic water pipe 17. Deionized water 18. K2CrO4 solution 19. AgNO3 solution, 0.05M
BRIEF INTRODUCTION OF ROCKY SHORE HABITAT
Rocky Shores are the regions with strong waves all the time which erode the rocks surface and thus leave the rocks exposed. Due to the different period of submergence along the rocky shore as a result of tidal effect, it is usually divided into three main regions : a. Splash zone -- a region rarely covered by the sea, but is usually sprayed with salt spray at high tide. Sometimes, it may be drenched in a heavy gale. Aquatic plants and animals are rare in this zone. b. Intertidal zone -- Also known as the littoral zone. It lies between the mean high water spring tide mark and the mean low water spring tide mark.. All the plants and animals in this zone must subject to exposure and submergence twice each day. It can also be sub-divided into upper, middle and lower intertidal zone. c. Sublittoral zone -- a region covered by the sea all the time. All the animals and plants present here are aquatic.
PROCEDURE OF THE FIELD TRIP :
We set off from school about two o' clock.. After an 1-hour trip, we arrived at our ultimate destination, the Turtle Cove eventually. Then we walk around the rocky shore in order to familiarize ourselves with the environment and find a desirable place where suit our investigation best. After that, our group began to distribute the work among ourselves with two of us drawing the sketch of the shore, several measuring the height of the site by using a transect line, several finding out the distribution of the organisms along the transect line by using an 1 m2 quadrat., and the remaining measuring the change of several physical factors from time to time. After obtaining all the data required, we left and the significant ecological field study finished.
METHOD OF INVESTIGATION OF THE ROCKY SHORE HABITAT
A. Non-biotic factors
1. Temperature -- It was measured by using a standard thermometer which was put in a wood box all the time in order to prevent its breakage for it is extremely delicate.
2. Wave Speed -- It was determined by the number of waves hitting the shore per minute. Although this method was inaccurate, it was the most convenient and easily-conducive method to measure wave speed.
3. Wind Direction -- We held a light string right above our heads and determined the wind direction by observing the direction of its movement.
4. pH -- We found out the pH of the sea water and rock pool water by submerging a pH paper into them and comparing the colour change with the pH colour plate.
5. Salinity -- It is divided into two processes. We first collected some rock pool and sea water at the Turtle Cove rocky shore and they were brought back for later investigation. For the laboratory work, we investigated the rock pool and sea water in the same way. Firstly, we diluted 25 ml of sea water/rock pool water to 250 ml. Then 5 ml of it was pipetted into a conical flask and several drops of K2CrO4 were added. The solution was titrated with 0.05M AgNO3 solution until a permanent red tinge was observed. The salinity of sea water and rock pool water could thus be calculated by the formula provided.
B. Methods employed to find out the distribution and abundance of the species
1. Mapping – A sketch map of the entire rocky shore habitat was made at a position where the whole habitat was visible. The simple but relatively accurate map should include all the surrounding features of the rocky shore, the water front, low tide mark, high tide mark and surrounding flora, et cetera. The shore was surveyed from above. With the aid of compass and mapping equipment, several straight lines were drawn through selected sites so that they run down the shore to the sea. The direction of each line was determined by using a compass and the location and direction of the lines were copied carefully on the sketch map. All these lines were along and perpendicular to the shore line.
2. Laying of the transect line and quadrat Line transect is a method used for making a detailed study along a line which cuts across the area where there is some clear transition of vegetation and fauna. In this current field trip, our group employed the transect line not only to assist in sketching a slope profile but was also used to find the distribution of various species within the community by recording the amount of organisms within an I m2 quadrat which was put along the transect line of 1 m intervals. The transect line was laid on the shore, from the top of the shore to the water front with 13 1 m intervals. In the first place, we had to construct a slope profile along the transect line. Along the line with totally thirteen 1-metre intervals, we determined the drop or rise in height at a particular position with reference to another by comparing the water level inside a plastic U-water pipe which were measured by using a long ruler. In order to find the distribution and zonation of different species along the transect line, a 1 m2 quadrat was placed by the side of the line and the organisms within the quadrat were identified and their amount were recorded. This process was repeated from one interval to the next till the end.
RESULT :
A. Physical Factors :
§ Weather : sunny
§ Highest tide : 2.0m (0836)
§ Lowest tide : 0.5 m (1449) !(This explained why we chose the time between 1400-1800 for our investigation as large part of the rocky shore would be covered by sea during high tide)
Time: 2 : 42 3 : 45 4 : 43
Temperature: air 29oC 26oC 26oC
rock surface 33oC 22oC 25oC
sea water 24oC 24oC 24oC
rock pool 26oC 26oC 25oC
pH : sea water 6.5 7.0 7.0
rock pool 7.0 7.0 7.0
Wind direction : north-east north-east north-east
Relative Humidity (%) : 70% 73% 75%
Wave speed : 5 waves/minute 5 waves/minute 5 waves/minute
Salinity : sea water 3.55% - -
rock pool 3.95% - -
The abiotic factors found during the field study which might pose a certain effect towards the distribution of organisms.
From the result of physical factors, one could see that there was a general decrease in the temperature readings from 14:42 to 16:43 which was apparently affected by the decreasing light intensity in a sunny day. However, the temperature reading on the rock surface at 15:45 was a wrong reading as it was out of the main trend. Other abiotic factors , at the same time, did not vary much. The salinity of rock pool water was more concentrated than the sea water which might be due to the evaporation of water by strong sunlight.
B. Levelling Result :
Location(m) 0 1 2 3 4 5 6 7 8 9 10 11 12 13
Change in height (cm) 0 +89 +78 +76 -16 +60 -9 +28 -30 -31 +31 -8 +12 +15
Absolute height (cm) 295 295 206 128 52 68 8 17 -11 19 50 19 27 15
(+ represents increases in height - represents decreases in height)
C. Horizontal Distribution of Animals and Plants Found along the Transect Line
Organisms 1 2 3 4 5 6 7 8 9 10 11 12 13red algae 20% 15% 10% 5% 5% green algae 8% 4% 1% 1% black lichen 25% 1% 3% 5% 20% 40% 30%green lichen 65% 15% 35% 10% 75% 20% orange lichen 75% 15% 5% 85% 25% 20% 60% 25% 20% pink lichen 18% 10% purple lichen 30%chiton 1 1 3 1 14 1sea urchin 4 periwinkle 15 30 30 3 3common limpet 1 20 30 50 50 barnacle 40 2 7 oyster 3 8 30 250 150 30 50 120 30 100 whelk 8 top shell 1 3 20 30 20 10 15 15 star limpet 5 clam 2 stalked barnacle 12 20 20 sea slater 1 1 small shore crab 1 Nerita Albicilla 1 12 Note : the highlighted blanks represents the organisms were found in rock crevice.
Form the results obtained above, I could divide the transect line intervals into three parts: 1 -- 4 m splash zone and upper shore 5 -- 1 1 m à middle shore 12 -- 13 m à lower shore As what I had mentioned before on page two, splash zone is a region where is merely covered by water. This region was mainly dominated by various types of lichens and periwinkles. Lichens were found everywhere in this zone, especially green and orange lichens whose colour were similar to that of rocks. Periwinkles could also be found attaching the surface of rocks and stones everywhere(They were usually the smaller types). Actually, what enables them to live in the splash zone with inadequate supply of water is that they have strong and hard shells which can protect them and prevent them from desiccation. The dominant types of organisms which could be found in the middle shore were limpet, oyster, top shell and barnacle. Common limpet is a gastropod which has strong , hard shell for protection and preventing parchedness. It also has a suctorial foot for firm attachment to the rock surface so that they would not be amputated from the rocks by waves. And for the barnacles, they also have very strong, hard shell for protection and preventing desiccation. In addition, they have a movable lid for the same purpose. Also, they are cemented very tightly onto the rocks so that they would not be dislodged from the rocks despite of strong wind. Lastly, mostly the higher organisms were found at the lower shore. For example, sea urchin, whelk, clam, et cetera. Chiton has a suctorial foot for attachment to the rocks so that they could not be easily be washed away by the water current. The shore was observed to be composed of granite rock surface and a few large boulders. The rocks surface became very non-smooth because of their exposure to the prevailing wind and incessant wave action all the time.
DISCUSSION :
After thorough investigation of the rocky shore habitat and obtaining the result for the distribution and zonation of different species in this habitat, a special point can be drawn: all the organisms are exposed to certain problems which are caused by physical factors and they have certain features or methods which can resist their affection on them. 1. Wave action At the lower shore region, the incessant wave action strikes strongly on the expose shore. This can easily cause the dislodgement of the organisms from rocks if they do not have proper attaching devices. On the other hand, this may also cause mechanical damage to the delicate tissues of organisms. Additionally, this may also make settlement of aquatic larvae very difficult. All the organisms we found on the rocky shore should thus able to overcome the problem caused by wave action. Most of the organisms found at the middle and lower shore possess specialized structures to hold on the rocks or stones. Here are few examples. Barnacles, limpets and snails all possess large and flattened feet which can hold firmly on the rock surface by suction method. Bivalves and tube worm can do similar things but by cementing method. Crabs have flattened carapace and powerful legs to grasp the rock surface. Green and brown on the other hand have holdfasts. Other animals adapt behaviourally by hiding in crevices or among algae holdfasts.
2. Tidal movement There are two high tides and two low tides each day. So the organisms at the middle and lower shore always experience exposure and submergence. The problem caused by submergence include desiccation, high temperature, salinity fluctuation, problem of gaseous exchange as well as different range of illumination. When the tide recedes, the middle shore organisms become expose to dry air. The danger of desiccation arises because of the heating effect of sunlight, evaporation of water and the frequent wind blowing. Furthermore, loss of water may also bring about an increase in salinity which aggravates the danger of osmotic dehydration. Marine organisms overcome the problem of salinity because they are isotonic to sea water. Other middle shore organisms living in rock pools or intertidal zone of the rocky shore have high osmoregulatory power in order to adjust the extreme salinity fluctuation when tide in or out.
Direct illumination on the exposed shore can produce extremely high temperature. Such a high temperature is surely fatal to the unprotected organisms. So most of the organisms minimize temperature extremes by retreat into some sheltered areas or they have a protective covering themselves. Some of the organisms minimize desiccation by the following methods: 1) Bivalves close their shells 2) Crustaceans burrow 3) Periwinkles excrete uric acid to conserve water inside their body. 4) Sea anemones secrete slimy exudations 5) Barnacles keep their movable plates shut The problem of desiccation is much more serious in the upper shore than in the lower shore for the length of exposure when the tide retreats is longer.
Several types of interrelationships among organisms were were found during investigation: Mutualism : lichens - between fungi and algae Commensalism : barnacles living on the carapace of crabs
One of the possible errors during our investigation was that we counted the number or percentage of organisms inside the quadrat by our instinct only and that is actually extremely inaccurate. Another error was that we might wrongly identify a species and that made the result less accurate. Sometimes, we might miss some of the organisms inside the area of the quadrat for they might hid under some heavy and big rocks which we found hardly to remove away. Some organisms move very fast during counting and this posed difficulty again.
The significance of this field trip and its benefit posed on me is great and utilizable. Not only having a wonderful time with other fellow students, but the most importantly is that I can learn a lot of useful knowledge about rocky shore habitat, about ecology, about biology.
THE SECOND FIELD TRIP
Date : 1st July, 1996 (Monday)
Time : 1:00 p.m. to 5:00 p.m.
Site : Sai King, Sai Kung, Kowloon
Type of habitat : Mangrove
Method :
1. Mapping
Firstly, we stand at a desirable place where the whole mangrove habitat can be observed. Then with the aid of compass and mapping equipment, we draw several straight lines through several selected sites to the point at where we stand. The direction of the lines are all determined by using a compass. Then a simple sketch can be drawn which was used as reference.
2. Transect line and quadrat
We firstly choose a place for investigation where should have most of the organisms we are supposed to find around. Then we drop a transect line from the side where are farthest from the sea till the side near the sea. We draw a slope profile firstly by comparing the water level inside a U-water pipe (mentioned previous). We then noted down the types of plants touched by the transect line for each 1 metre interval so that we can know the distribution and zonation of the plants in a mangrove habitat. On the slope profile, we can indicate different types of plants on it by using different symbols which is the best way to show the distribution and zonation of plants. We can also draw a kite diagram below the slope profile so that the result can be shown much more clearly.
3. Determining physical factors: a. wave speed -- can be determined by finding the time for a floating cork to move a given distance.
b. salinity -- We collect a bottle of sea water nearby and its salinity is determined in laboratory by using the method mentioned previously.
c. temperature -- measured by using a standard type of thermometer. d. ph -- measured by immersing a strip of ph paper in the water inside the mangrove habitat and the sea water respectively.
