OCEAN QUEST

DIVING WITH PURPOSE

CORAL GROWTH OBSERVATION IN PULAU TENGGOL, MALAYSIA

Introduction

Following the pilot project on coral propagation initiated by Percetakan Nasional Malaysia Berhad on September 22nd. 2012 a follow up observation is carried out beginning in March 2013. The preliminary observations are aimed to gather data on perturbations and factors contributing to coral growth. This observation is prematurely prepared upon exclusive request by relevant authorities. The observation is initially scheduled to continue for one year ending on September 22nd. 2013. Nonetheless the results of the observation this far have been compiled and set forth for evaluation.

General Observations on Coral Growth at Teluk Air Tawar, Pulau Tenggol

This general observation is made every month during the season from March 2013 and shall be continued until first week of October 2013. Object of observation is to count the number of coral colony affected in one hectare of coral reef beginning at the borders of intertidal and ends at the reef crest (reef front). The observations at coral propagation site include state of health of corals, threats and disease, colony size, physical changes of reef structure and water conditions. Any occurrence pertaining to the corals within the bay is observed and recorded. Location is marked at the northern most point of the site where trenches marking the boating passage is located. This point is at 04⁰48’27.23” N, 103⁰40’39.34” E can be located by following the lateral mooring rope.

Intertidal Area (Zone 1)

Intertidal zone at Teluk Air Tawar covers approximately twice the size of the coral reef area. It is estimated intertidal area is 38,109 m² or 3.8 hectares. Within the 1 hectare of observation area, 27% (2,700 m²) of intertidal area is included in the observation area and it consists of the outer margin of the intertidal zone bordering the reef flats. The intertidal zone plays important role as it is the concentrated areas where ideal conditions for coral propagation are found. (Figure 1)

 

Intertidal zone is the least active areas and most record of observation is made close to the outer margins near the reef flat. Coral propagation in this area concentrates in the outer margins of the intertidal zone bordering the coral reef. Coral propagated in this area has the most rapid growth rates. Coral propagated in this area have the highest chance of survival as there are fewer predators and plenty of sunlight. Shallow depths are added advantage of the intertidal zone. It is much easier to monitor and doesn’t require the use of Scuba for monitoring.

 

Coral Reef Area /Reef Flat (Zone 2)

At Teluk Air Tawar the total estimated reef area with coral cover is 20,512 m² which is converted to 2.05 hectares. The coral cover density area in the bay measures 413 m wide and 49 m deep at the widest point. The coral cover areas do not include the intertidal areas and the back reef areas. Highest density of corals is found in the south part of the bay. Depth range at the coral reef begins at just under 2 meter at the intertidal border and reaches up to 10 meters at the reef front. Observation area is approximately 50% of the total bay area that is estimated to be 10,000 m² or 1 hectare in total. In this 1 hectare of observation area, 47% (4,700 m²) consists of coral reef, 30% (3,000 m²) outer reef front and 27% consists of the back reef or intertidal zone. (Figure 1)The reef flat area is considered the most active areas of the reef where most record observation on coral state of health is recorded. Coral propagation in this area concentrates in voids and dead coral patches surrounded by living corals. Coral broodstock is placed near the margins of the dead coral patches taking advantage of the shelter provided by the living colonies.

 

Outer Reef Front / Reef Crest (Zone 3)

The outer reef front / reef crest is the deepest area of this observation. Bottom composition in this area consists of sand and rubble with depths ranging from 9 to 12 meters. There are some areas of soft coral beds that mainly consist of genus Sarcophyton. The reef crest amounts to 30% (3,000 m²) of the observation area. The margin at the outer edges of the reef flat meeting the reef crest is also propagated withcorals. The difference in depth and surrounding parameters serves as comparative data in our observation.

 

Parameters at Coral Propagation Areas

During the coral propagation program which takes place on 22nd. September, 2012 the corals frags are planted in 3 separate areas and in varying depth. The coral frags are placed sporadically on the edge of the existing coral colonies.

 

1. Zone 1 - Approximately 25 plates are placed in the outer areas of the intertidal zone at depth of 3 meter during mean high water level / high tide (MHWL). This area is protected from the prevailing tidal currents by the reef flats.

 

2. Zone 2 - Second batch of coral frags is placed in areas of dead coral in 6 meters of water during high tide (MHWL). This area is moderately exposed to the tidal currents and long shore currents.

 

3. Zone 3 - Third batch of coral frags are placed at the outer reef crest area in 8 meters of water during high tide (MHWL). This area is exposed to the strongest tidal currents.The coral frags are left to grow until March 2013 when the first monitoring takes place in the beginning of the season. Sporadically placed the corals have to be relocated, their growth recorded and comparison are made between the varying depths and topography. Object of this data is to ascertain the key factors influencing growth rates and use these findings to establish coral nursery in the future. This pilot project establishes just the right mix of depth and conditions which have contrasting effect on coral growth rates.

 

Average Coral Growth Rate Record

Each observation begins with searching for the coral frags that is propagated to the area. On each search we may find two or three plates that we could record the growth in height of the colony. By taking such measurement we can establish a “fair” figure of average growth rate of coral in that area. There are occasion that we found corals that are shorter than the ones we have measured in the previous month and there are also occasions that we found the ones that are taller. Working with these dynamics we can be fair of estimating average growth rates of the corals we have propagated in each area.

 

Growth Rate Records

Table 1 - Periodic Growth Rate Record of Propagated Corals at Teluk Air Tawar, Pulau Tenggol.

In July 2013 the fair overall average growth rate is 10.6 cm in a given period of ten (10) month. (excluding the initial average broodstock height = 3 cm).

 

Total Growth Rate

Total growth rate is the on site height measurement taken in July 2013 in each area.

 

Zone 1 - 22 cm – 3 cm broodstock height = 19 cm total growth. This area has the fastest growth rate in comparison to the other areas.

 

Zone 2 – 8 cm – 3 cm broodstock height = 5 cm total growth.

 

Zone 3 – 5 cm – 3 cm broodstock height = 2 cm total growth.

 

This preliminary observation establishes that coral growth is influenced by location and conditions. Several parameters are established and observed to find the perturbations which enhance or delay coral growth at each designated area.Perturbations leading to coral growth are carefully observed as part of preparatory/preliminary study that will help in our concept of coral propagation.

Factors Contributing to Coral Growth

Corals are polytrophic, meaning they are dependent on both photosynthesis and captured food for energy and growth. Both feeding behavior shall determine how well coral obtain energy to grow. In this concept of coral propagation the heterotrophic feeding behavior of corals and the mineral dynamics of sea water are emphasized and much observation made on food abundance, plankton migrations, mineral precipitation dynamics and geographical factors such as bottom composition and topography.

 

Geographical Comparisons

Coral growth rates are different at different locations of the world and that general data cannot be established based on observation in other location. Example, data obtain on coral growth at the Great Barrier Reef (GBR) cannot apply to corals in Malaysia as the amount of sun’s energy reaching Malaysia (at Equator) is far greater than it is in GBR (at 14⁰ to 22⁰ South of Equator). Coral growth rate should be compared in areas of that are at similar latitudes and in same depth of water. Water clarity may differ from one site to the other in Malaysia and because our sites are at same latitudes the available sunlight is similar i.e. East coast and West coast of Peninsular Malaysia. However the survivability of coral at such latitude as GBR tells us that even on our cloudiest day our coral should be able to receive photosynthates from zooxanthellae and convert them to energy. It will be absurdity to assume that corals propagated in Malaysian waters are affected by insufficient photosynthesis. However as matter of research this subject shall be included for comparative data.

 

Coral Feeding Observations

A number of observations already been carried out to determine if there are differences in feeding activity and possible food abundance in Zone 1, Zone 2 and Zone 3. Observations are also made on the dynamics of water movement which are the carrier of plankton. Night dives are conducted to observe the time when coral polyps begin to open and also to observe for any sign feeding behavior. Particulate Organic Matter (POM) and Dissolved Organic Matter (DOM) that existed in the water are also observed.

Visual observations are made on coral feeding activity in Zone 1, Zone 2 and Zone 3. Coral are able to detect presence of plankton (food) and this perturbation triggers coral polyps into feeding behavior. This can be seen in open polyps with extended tentacles capturing plankton and feeding them through the mouth. This feeding activity occurs at different times at different depth. Frequency at which the tentacles feed the mouth is also observed.

 

Polyps Opening Times

Polyp Feed Count suggests that corals in Zone 1 are indeed feeding rigorously on plankton in which the nutrition may have contributed to the faster growth as compared to Zone 2 and Zone 3 (See Table 3).

The Synergistic Effects of Light and Nutrition on Coral Physiology

The positive effects of nutrition on corals are profound; essential processes such as photosynthesis, calcification and the buildup of the organic matrix are stimulated by feeding. Plankton supplementation is thus useful in building blocks of corals. Coral in Zone 1 also receives the most sunlight thus making energy conversion more efficient than Zone 2 and Zone 3.

 

 

Particulate Organic Matter (POM)

This is particles which populate the water column and it is visible at night. POM includes zooplankton and they are often attracted by light which in turn invites feeding frenzy of marine worms, krills and other micro organisms. It is often difficult to observe polyp feeding behavior at night due to this interference. Therefore polyp feeding counts must be done intermittently in durations of ten seconds per observation. A total of six repetitions are made for each colony.

 

Tidal Currents

Effects of tidal currents on coral feeding activities is also been observed. It is known by captive coral breeders that corals are only efficient in capturing plankton at flow velocity of no stronger than 17.5 cm/sec. Tidal flow are plotted on the location map to determine its directions within the bay area at Teluk Air Tawar. Direction of flow recorded during flooding and during ebbing tides using white water color pigment dispense from a dropper. The direction which the dye travels is recorded. Tidal flow at Zone 1 is not noticeable both during flooding and ebbing tides. The inflow of plankton is deposited into Zone 1 through an opening created by a mooring line. Plankton reaching the intertidal areas did accumulate in that area giving more time and volume for the corals there to feed. Zone 2 is different from Zone 1 because it is open to the prevailing tidal currents. Plankton carried by the tidal stream passes through this area and did not accumulate them in Zone 2 as it does in Zone 1. As a result coral colonies in Zone 2 feeds lesser compared to Zone 1. Zone 3 is exposed to the open water where tidal currents are strongest. As it is also deeper than Zone 1 and Zone 2 it receives less plankton due to plankton migration in the water column and congregated near the surface at night.

KH / ALK Factor

This is the Calcium and Carbonate content in sea water. Calcium, Carbonate and Magnesium are the three major elements in sea water. Coral extract these minerals from sea water and convert them into their Calcium-carbonate skeletons. The dynamics of these minerals is also crucial from rapid development of coral skeleton, meaning, fast growth. Well fed corals combined with good photosynthesis provides coral with energy to build but the main building material must be abundant in order for rapid growth. Presence of coral rubble along the shores is an added advantage to corals in Zone 1. Waves washing ashore grinds the Calcuim-carbonate and dissolve them back into the sea water. These activities occurs right next to the corals at Zone 1.

 

Magnesium Factor

Magnesium is one of the major elements in the sea water. Magnesium is a mineral that did not have any biological function for corals but it is responsible for buffering the Calcium and Carbonate and preventing the two from binding and precipitate. Magnesium in sea water is directly responsible for keeping Calcium and Carbonate plentiful and available for the corals.

 

Summary

This simple observation reveals three components of coral growth:

 

1. Sun's energy used in photosynthesis by zooxanthallae partially provides the energy for coral. This phototrophic process varies with depth of water due to light absorption and reflection properties of water. Coral in shallower depths receives more sun energy compared to those in deeper water.

 

2. Food is a necessity to all animals including corals. Plankton migrates to the surface of the sea at night and it is most abundant in shallow depth. This added more feeding advantage to corals in shallow water as compared to those in deeper water. Feeding on plankton at night provides the extra bulk of energy for coral to build.

 

3. Even with abundance of energy, growth of corals are dependent on the availability of building material in order to build their skeleton. The mineral Calcium and Carbonate is consumed by corals and is used to build their skeleton. Depleted Calcium is replaced by waves grinding and dissolving calcium from coral rubbles and dead shells on the shoreline. Abundance of Calcium and Carbonate near shore gives another advantage for coral growth in the shallow which is closest to the source of the minerals.

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