Marine Research in Indonesia (MRI - E-Journal)
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STRUCTURAL ANALYSIS OF MANGROVE COMMUNITIES ON THE CENTRAL QUEENSLAND COASTLINE
No full textThe mangrove communities of the Central Queensland coastline are structurally and floristically intermediate between the relatively simple, temperate mangrove communities to the south, and the more complex and luxuriant communities to the north. Climatically the central Queensland coastline is subtropical with a low (1011 mm) annual rainfall, falling mainly in the summer months; evaporation rates are high, particularly in winter. As a result of a four-metre tidal range and a gentlysloping depositional coastline, the areal extent of mangroves is large and most topographic and physiognomic types are represented. Twelve species of mangroves occur in the study area and although zonation is recognizable, the zones are neither constant nor discrete. In the Port Curtis area, three large plots (500 m2 have been established in which all mangroves have been numbered and tagged since January 1975. The results of the initial investigation of the plots are presented together with some of the changes noted on re-examination after 12 months
A PRELIMINARY STUDY OF THE MANGROVE FOREST ON PULAU RAMBUT, JAKARTA BAY
No full textPulau Rambut (± 56ha) is one of the islands of the Pulau Seribu group. It is a coral island covered by disturbed forest and secondary growth at the center, and mangrove forest at its periphery. A study in a 290 x 10 m transect running south to north across the mangrove forest shows a distinct zonation as follows : the Scyphiphora hydrophyllacea - Lumnitzera racemosa community on coral flat with patchy shallow soils on the interior, the Rhizophora mucronata community on relatively deep soil overlaying coral formation, and the R. mucronata - R. stylosa community on periodically submerged coral flat. Profile diagrams established along the transect show structural changes also. The R. mucronata forest is the most developed community and appears to be the most prevalent. R. stylosa forms the pioneer species on this island
THE EFFECTS OF SOME PESTICIDES ON REEF CORALS
No full textWhile investigating a reef coral kill in Samoa it was speculated that this might have been due to contamination by some chemical. Subsequently, scleractinian reef corals were tested to assess their reactions to 12 commonly used pesticides and toxic substances. The chlorinated-hydrocarbons such as DDT and Endrin produced stress effects in corals subjected to 2ppm for 24 hours in in-vitro studies although the corals continued to deposit skeletal calcium. In-vivo tank experiments suggested that small amounts of these substances in seawater stimulated the corals to deposit skeletal calcium. Other pesticides were much less toxic to the corals
SOME ASPECTS OF THE CULTURE OF EUCHEMA
No full textEucheuma striatum and Eucheuma spinosum, are red algae of commercial value because of their carrageenin content, to an increasing extent are cultivated in the Philippines. The influence of environmental factors on growth rate and photosynthesis of these seaweeds were studied through observations in their natural biotope in seaweed farms, from in-situ experiments, and photosynthesis experiments in an incubator.
While difference in light intensity and temperature play only a minor role, the algae were found out to be sensitive to low salinity and to the amount of dissolved gases and nutrients in the surrounding seawater.
The algae can only be cultured in areas where there is sufficient current but to a cer-tain extent lack of current can be compensated by exposing the plants to wave action. This leads to certain conclusions regarding the most suitable method of commercial Eucheuma culture. Eucheuma can be successfully cultured in small rafts or in floating baskets in areas where there is insufficient current for the use of fixed nets or strings.
There is evidence that-the CO2 -02 metabolism in the surrounding water plays an important role in Eucheuma growth.
Eucheuma harvest can be further increased by introducing more nutrients. Fertilizing with phosphate caused a bigger increase in growth rate than with nitrogen. The method of spraying plants after temporarily removing them from the water, found to be more effective than fertilizing solutions by the use of clay pots.
The presence of a bacterial disease, locally referred to as "ice-ice", was recognized as a clear indication that certain environment conditions were unfavourable for Eucheuma culture. Low salinity, in the first place, but also lack of current favors the attack of "ice-ice".
Finally, it was found that Eucheuma adapts itself to its culture site in such a way that after maintaining seedlings in an area for a sufficient length of time, the cultured plants showed better growth rates and were resistent to unfavorable conditions than plants recently transferred to the area
MEASUREMENT OF PHYSIOGRAPHIC CHANGES ON MANGROVE-FRINGED ESTUARIES AND COASTLINES
No full textStudies of physiographic changes are in progress on mangrove-fringed shorelines in Westernport Bay in Victoria, and Cairns Bay in Queensland, Australia. Historical evidence of advance or retreat of these shorelines has been obtained from comparison of historical maps and air photographs with the present configuration, and supplemented by monitoring shoreline" changes with reference to established datum points during the past decade. In addition, changes in substrate level within the mangrove fringe, on mudflats to seaward, and on salt marshes (where present) to landward have been measured with reference to vertical changes on inserted poles, accretion over emplaced brick-dust layers, and changes in probe depths to underlying horizons (rock, sand, or peat) Results indicate that the advance of Avicennia marina on to mudflats is followed by relatively rapid and generally sustained vertical accretion related to interception of sediment within pneumatophore fields. Other mangroves or salt marsh species then replace Avicennia, and continued accretion leads to the development of a depositional marshland terrace, representing a re-shaping of the inter-tidal profile by the agency of vegetation. Mangroves that produce pneumatophore fields are considered to be more effective in trapping sediments than stilt rooted mangroves such as Rhizophora spp. or buttressed mangroves such as Bruguiera spp
THE MANGROVE FORESTS OF CAIRNS, NORTHERN AUSTRALIA
No full textSurveys of the flora and fauna of the Cairns tidal wetlands were carried out by members of the Australian Littoral Society during the summers of 1974 and 1975. These wetlands cover an area of 6000 hectares in Trinity Inlet and the Barron River delta. The Cairns mangrove and saltmarsh vegetation forms distinct patterns of zonation which appear to be largely controlled by the volume and constancy of freshwater flow. The results of extensive collections revealed a wetlands associated fauna of invertebrates and fish that is considerably more diverse than has previously been reported for northern Queensland. While some species are ubiquitous, many of the invertebrates have been found only in a discrete habitat within particular zones of vegetation. Species diversity of molluscs and crustaceans is greatest in the most constantly inundated zones. A diverse fauna occurs in rotted mangrove logs. Data were obtained on the export of organic material from a small mangrove watershed on one day in December 1975. These revealed a figure for detritus of 11.3 gC/m2/day. This was composed of a 'dissolved' organic carbon fraction of 6.3 gC/m2/day, and 5.0 gC/m2/day of particulate organic carbon. These figures are discussed in relation to available literature on mangrove forests and estuaries. Rapid urban and agricultural development of Cairns is now placing a large portion of these wetlands under serious threat of destruction. The prospects for the future conservation of the Cairns tidal wetlands are discussed
RELATIONSHIP BETWEEN TIDAL FORESTS (MANGROVES) AND COMMERCIAL SHRIMP PRODUCTION IN INDONESIA
No full textAn attempt has been made to relate the surface areas of tidal forest (mangrove) and the commercial shrimp production in those areas and adjacent waters in Indonesia. A significant linear relationship (a = 0.01) was obtained between these two variables as expressed in an equation : Y = 5.473 + 0.1128 X, where Y k the shrimp production in 103 tons and X is the mangrove surface area in 104 Ha. This relationship indicates that the shrimp production increases with the size of the tidal forest area implying that any reduction of the tidal forests, e.g. for industrial and agricultural purposes will cause a decrease in shrimp yield
EFFECTS OF ELEVATED TEMPERATURE ON THE MORTALITY AND METABOLISM OF PACIFIC REEF CORALS
No full textThe upper thermal tolerance limits of subtropical (Hawaiian) and tropical (Enewetak) reef corals were determined both in the field and under laboratory conditions. Enewetak corals routinely withstand temperatures up to 34°C whereas similar exposure time at 32°C kill their Hawaiian congeners. These differing upper thermal limits correspond to increases of + 4 - 5°C above the annual water temperature maxima at each location. Reef coral temperature tolerance is therefore closely adapted to the ambient ocean temperature conditions of a geographic location.Studies of temperature effect on reef coral photosynthesis (P) and respiration (R) also showed different patterns between locations. Same species shower greater autotrophic capability at elevated temperatures in Enewetak than Hawaii. Critical temperatures estimated as coinciding with P:R ratio values minimal to support long term functional autotrophy were 2-5°C higher for Enewetak than Hawaiian specimens, closely corresponding to observed differences in upper thermal tolerance. Results support a hypothesis of temperature adaptation capability for reef corals and suggest that short term physiological tests can predict relative differences in temperature tolerance among coral species
CORAL REEF RECOVERY FOLLOWING ACANTHASTER INFESTATIONS
No full textSince late 1971, data have been obtained on coral recolonization on reefs of the Great Barrier Reef which had been damaged by Acanthaster infestations during the 1960's. There is now tabular Acropora, particularly on the seaweed reef slope in the depts of less than 10 meters. Many such corals now measure 50 cm to 100 cm in diameter. However, recent observations indicate that these corals can be dislodged by strong wave action thus providing an opportunity for both further coral settlement and for the survival and growth of previously "overtopped" colonies
