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D. P. Praseno
The living organisms of the sea can be divided into three major groups: benthic, necton, and planktonic organisms. Benthic organisms usually live on the bottom of the sea, or attached to various substrates. They may crawl on the bottom of the sea, or live buried in holes. Necton are free swimming organisms, like most of the fishes, while plankton are suspended or floating organisms, and are not able to withstand water currents.
This chapter will discuss only the third group, the planktonic organisms, and what is known so far about them in Indonesia, with special reference to the waters between Jakarta and Cirebon.
Plankton Primary Productivity
The most common method for studying primary productivity is the method introduced by Steeman-Nielsen (1952) using C14, Using this method, or modifications of it, measurements have been made on several cruises in Indonesian waters by Indonesian and foreign scientists (Birowo et al. 1975).
As was expected, high productivity values were obtained from shallow waters, especially those influenced by river water discharge. Malacca Strait nearly always shows high values (more than 1 mg C/m³/hour). Usuaily primary productivity in the surface layers has a value ranging from 0.1 - 1 mg C/m³/hour.
Doty et al. (1963) measured primary productivity of the waters around the Seribu Islands, and obtained values ranging from 0.23 - 0.52 mg C/m³ /hour but Nontji (personal communication) also obtained high values from waters around the coral reefs of the Pari Islands, where values ranging from 1.86 to 8.96 mg C/m³/hour were recorded. Similar values have been measured around several coral islands in the Pacific (Sargent and Austin 1949; Odum and Odum 1955; Kohn and Helfrich 1957). High values may also be found in estuarine waters or areas of marine upwelIing (Soegiarto and Nontji 1966).
Another method of measuring primary productivity is by determining the chlorophyll content of phytoplankters. This method is commonly used by LON-LIPI. Nontji (1974a) compiled all chlorophyll data of the Indonesian waters and calculated an average value of 0.19 mg/m³. A higher average (0.24 mg/m³) was obtained in the east monsoon, while during the west monsoon the average value was 0.16 mg/m³.
Depths of maximum chlorophyll concentration are variable. In the South China Sea (Hung and Tsai 1972) the depth was between 50 and 125 m, while in the Banda Sea it was 25 m (Nontji 1974a, 1975), and in the Halmahera Sea 50 m (Nontji 1974b).
Periodical observations in Jakarta Bay revealed that the bay water is very productive. Observations were made during 1975 - 78. Sampling was carried out during both the rainy and dry seasons (January and August), and during the two transition periods (May and November). The average chlorophyll concentration ranged from 0.90 to 5.41 mg/m³ with a maximum value of 17.96 mg/m³. The highest concentrations were found in samples taken in front of river mouths.
Tests were also made to detect and measure chlorophyll in sea water by remote sensing techniques. A chlorophyll detector was designed and constructed by the Deutsche Forschungs und Versuchtanstalt fur Luft und Raumfahrt (DFVLR) in co-operation with the Indonesian National Institute of Aeronautics and Space (LAPAN). The radiometer was tested in Jakarta Bay, and gave higher values than those recorded by surface sampling (Praseno et al. 1978a).
Phytoplankton
Diatoms and dinoflagellates are the main phytoplankters in the sea. The diatoms have wide distribution, while dinoflagellates are mostly concentrated in estuarine waters. Some dinoflagellates, e.g., Noctiluca, are holozoic types. These organisms do not possess photosynthetic capacity, and depend on consuming organic material from their surroundings. However, they are still grouped as phytoplankters in order not to separate them from the rest of the dinoflagellates and other planktonic algae that are holophytic types.
Another member of the phytoplankters is Trichodesmium (Cyanophyceae). This appears only occasionally, but is then found in great numbers floating on the surface like sawdust. Delsman (1939) has observed the blooming of these organisms forming very long patches on the surface of the Java Sea. Trichodesmium spp. avoid less brackish water and are nearly always found some distance out from the coast.
Delsman (1939) also found that in the Java Sea phytoplankton are concentrated in coastal waters and diminish towards the open sea. In coastal waters the diatoms are mostly represented by the genera Rhizosolenia, Chaetoceros, and Coscinodiscus, while dinoflagellates are mainly represented by the genera Noctiluca and Ceratium (Allen and Cupp 1935).
During the last decade a number of observations have been carried out, mostly by staff members of LON-LIPI. Nontji and Arinardi (1975) studied phytoplankton distribution in relation to some ecological factors, and found that the rivers of Java and Kalimantan have important influences on phytoplankton. Nontji (1973) described distribution patterns of prominent phytoplankton genera in relation to ecological factors, and Hutomo (1977) studied seasonal variations in phytoplankton in the waters of the southern part of Pulau-Pulau Seribu, where three peaks occurred, during the months of October, January-February, and May
Periodical observations in Jakarta Bay and its vicinity showed that besides the genera mentioned by Delsman (1939), other genera may also be important, like Skeletonema, Bacteriastrum, and Thalassionema/ Thalassiothrix of the diatoms, and Dinophysis of the dinoflagellates. Phytoplankters are mostly concentrated in the estuarine waters of Muara Angke-Muara Karang and Marunda.
Phytoplankton growth is influenced by the presence of nutrients, derived either from river-water discharge or from marine upwelling processes. If sufficient nutrients are available, blooming of phytoplankton may occur, either of a single species, or of many species at the same time. Blooming of a single species was observed in Jakarta Bay by Praseno and Adnan (1978a, b, c). The plankton Noctiluca was often found blooming in waters influenced by river discharge, appearing in great numbers after heavy rainfall. Another phytoplankton that usually blooms independently is the diatom Skeletonema sp. While other diatoms do not grow because of the drop in salinity, Skeletonema can tolerate low salinity. This may be important for the mixed culture of the diatom without applying specie! techniques to produce a monoculture. Skeletonema 5p. is one of the diatoms used as food by many larvae.
Zooplankton
Zooplankton studies in the Java Sea were first made by Delsman (1921) when he made an inventory of fish eggs and larvae. His important work continued for 17 years (Delsman 1921,1922,1924, 1925,1926a, 1926b, 1926c, 1929a, 1929b, 1930, 1931a, 1931b, 1931c, 1932, 1933, and 1938). Other zooplankters were investigated in relation to ecological factors like salinity and phosphate (Delsman 1939).
After that, little was done until 1964. In 1964 the Baruna Expedition I was carried out, with some stations located in the Java Sea. Results showed that zooplankters are mostly concentrated near the coasts of Java and Kalimantan. Plankton volumes reached an average of 0.04 ml/m³, and individual counts had an average of 226 plankters/m³. Copepods were predominant, and usually consisted of the genera Acrocalanus, Candacia, Corycaeus, Eucalanus, Oithona, and Pleuromamma (Arinardi 1970).
Prawoto and Tjee (1966) made quantitative investigations of plankton of the waters around Java. They found that plankton volumes in the Java Sea are higher than those in the Indian Ocean. Thaliacea (mostly Salpidae) were found in abundance in the western part of the Java Sea.
Zooplankton of the waters around Pulau-Pulau Seribu were investigated in more detail after 1969. The influence of seasons upon plankton concentrations was studied by Praseno and Arinardi (1974), who found that the volume of zooplankton during the rainy season was less than that during the dry season. The average zooplankton volume during the rainy season was 0.10 ml/m³, while during the dry season it was 0.20 ml/m³. The low value in the rainy season was due to the small amount of Thaliacea, which then had a frequency of occurrence of 23 per cent and a relative abundance of 0.17 per cent, while during the dry season the values were 63 per cent and 4.29 per cent, respectively.
Further analysis showed that the average number of plankters during the rainy season was 695 organisms/m³ and during the dry season 689 organisms/m³. During the rainy season the distribution was more or less homogeneous, while during the dry season the plankters were concentrated near the coast (Arinardi et al. 1977).
The influence of rain can be detected in the sea. After heavy rainfall certain zooplankers appear in great numbers, like the Calanoid copepods, Decapod larvae, and Oikopleura in the waters around Pulau Panggang, PulauPulau Seribu (Arinardi 1978a). Other plankters may appear at the approach of the dry season, e.g., Ostracoda, or during the dry season, e.g., Thaliacea. Arinardi (1978b) also studied the relationship between phytoplankton and zooplankton of the area, and found that a reverse relationship occurred during the dry season.
Due to the fact that Jakarta Bay is located near a centre of marine research, it is natural that its waters have received much attention. Periodical surveys were carried out in the area to monitor changes of water condition. Thus Sutomo (1978) found that the distribution of zooplankters in the bay is influenced by water masses, rainfall, and the presence of Noctiluca sp. A maximum number of zooplankters was obtained in the month of November 1975, the transition period from the dry to the rainy season, when 1,689 organisms/m³ were counted. A minimum number of organisms was obtained in May 1976, the transition period from the rainy to the dry season, when the average was 1,309 organisms/m³. Copepoda, Luciferidae, and Larvacea were found mainly during the rainy season, while Ostracoda were found mainly during the dry season.
Sutomo etal. (1977) made monthly observations of zooplankton in the waters in front of Angke River. Low zooplankton concentrations in this water were caused by blooming of Noctiluca and Thaliacea, or by the turbidity of sea water, which in turn was caused by heavy rainfall. High plankton concentration was observed in April (4,451 organisms/m³), and low concentration in October (366 organisms/m³).
Plankton observations were also carried out in connection with fouling organisms, e.g., barnacles. In the waters seaward of the Karang River, in Jakarta Bay, barnacle larvae were found throughout the year, with a peak in September. Minimum numbers of Cirripid larvae were found in March (Hutomo etal. 1977; Romimohtarto and Arinardi 1977), their greatest concentration being some distance out from the coast.
Micro-organisms
Micro-organisms are sometimes included in the plankton community. These organisms cannot be captured by nets because of their size. Plankton that pass through the finest net are called nannoplankton, their size ranging from 5 to 60 microns, and they are usually collected by centrifuging water samples. Organisms smaller than 5 microns are called ultraplankton, and include bacteria and smaller flagellate forms.
Nannoplankters have only been studied in regard to their chlorophyll content, together with the rest of the phytoplankters. Samples are obtained by dipping the surface water, or by using a van Dorn sampler to obtain water samples from certain depths.
Ultraplankton may play an important role in the marine environment. In 1951 for the first time food poisoning due to the bacteria Pasteurella parahaemolyticus was reported by Fujino et al. (1951). Takikawa (1958, 1960) named the bacteria Pseudomonas enteritis,and it was later called Vibrio parahaemolyticus by Sakazaki et al. (1963), who divided it into three biotypes, according to morphological, cultural, and biochemical properties. The three biotypes are now referred to as Vibrio parahaemolyticus (Biotype I), V. alginolyticus (Biotype II), and V. anguillarum (Biotype III).
In Japan V. parahaemolyticus is known to cause food poisoning, which can develop into an epidemic in the summer (Aiiso et al. 1963; Miyamoto et al. 1962). V. parahaemolyticus is a typical bacteria belonging to the marine environment (Horde et al. 1963; Asakawa 1966), and in the United States it has been isolated from sea water and mud as well as from several crustaceans, molluscs, and fishes (Baross and Liston 1968, 1970; Ward 1968).
In Indonesia the extent of food poisoning due to V. Parahaemolyticus is not fully known. Observations in Jakarta Bay were carried out by LON (Thayib and Suhadi 1974), when V. parahaemolyticus was isolated from mud, molluscs, and fishes. Results showed that 15 per cent of the mud samples, 13.4 per cent of the molluscs, and 9.7 per cent of the fish samples were contaminated by the three biotypes. For V. parahaemolyticus the percentages were 5 per cent of the mud samples, 2.7 per cent of the molluscs, and 1 per cent of the fish samples.
Investigations were also made to detect the presence of coliform bacteria (Thayib and Listiawati 1977, 1978). High concentrations were obtained from water samples of the estuarine area and waters surrounding the islands. The MPN of Coliform bacteria varied from 930 per 100 ml to 1,100,000 per 100 ml of sea water in Jakarta Bay.
Further investigations of the bacteria in Jakarta Bay were carried out by Thayib et al. (1977). Other micro-organisms were also detected in clams (Anadara spp.) and in oysters (Crassostrea spp.). Salmonella was found to contaminate 52.3 per cent of the 300 clam samples, and 46 per cent of the 250 oyster samples. The bacteria Shigella contaminated 6.3 per cent of the clams, and 1.2 per cent of the oysters. Escherichia cold was found in 8.3 per cent of the clams, and 16.0 per cent of the oysters, while the bacteria Staphylococcus was detected in 1 per cent of the clams, and 37.1 per cent of the oysters. Further investigations showed that V. parahaemolyticus has contaminated 3 per cent of the clams, and 5.5 per cent of the oysters.
These results showed that the clams and oysters of Jakarta Bay are contaminated to such a degree as to endanger the consumers.
Besides pathogenic micro-organisms Thayib [1878) made an inventory of hydrocarbonoclastic micro-organisms in Jakarta Bay. Halophylic, halotolerant, and terrestrial bacteria were recorded. Of all the microorganisms Pseudomonas was found to predominate. Other bacteria were Arthorbacter, Nocardia, Micrococcus, and Corynebacterium.
Investigations of plankton, chlorophylls, and micro-organisms have been concentrated mainly in Jakarta Bay. As a result it can be concluded that the waters of Jakarta Bay are very much influenced by the rivers which enter the area. Inputs of nutrients have made the bay water very productive, but it is also affected by many pathogenic bacteria, which contaminate marine products. If these marine products are not treated correctly, they may endanger their consumers. The bay water is also polluted by oil, especially in the Tanjung Priok and the Sunda Kelapa areas, and this can be detected indirectly from the MPN of hydrocarbonoclastic micro-organisms.
The Jakarta Bay area has to be monitored periodically in order to trace possible changes. Only in this way can unfavourable developments be detected, and steps taken to prevent further damage of the environment. Little information is available on other coastal and estuarine waters between Jakarta and Cirebon. More attention should be paid to these areas since they are very important for fisheries.
References
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Discussion
Burgers: How do the micro-organisms contaminate fish and molluscs in the area?
Praseno: They are probably not harmful to the consumers because sea foods are mostly cooked. There are blooms of other organisms but they do not cause substantial fish mortality.
Sutamihardja: Would you comment on the high values of cadmium and mercury in Jakarta Bay and on the causes of high micro-organism populations?
Praseno: Heavy-metal concentrations are due to industrial activity. Almost all the industrial waste water from the region enters the rivers and thus passes into Jakarta Bay, carrying high concentrations of heavy metals. Microorganisms also enter Jakarta Bay in river discharge, and the MPN of coliform bacteria is very high indeed.