SPATIAL DISTRIBUTION OF PHYTOPLANKTON AT THE HURUN BAY, LAMPUNG

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1 J. Hidrosfir Indonesia Vol.3 No.2 Hal Jakarta, Agustus 2008 ISSN SPATIAL DISTRIBUTION OF PHYTOPLANKTON AT THE HURUN BAY, LAMPUNG Rahmania A. Darmawan Peneliti Bidang Biologi Laut Badan Pengkajian dan Penerapan Teknologi Abstract It is already known that several ecological factors affected phytoplankton distribution in coastal waters, but since the global increase of Harmful Algal Blooms (HABs) phenomenon, people pay more attention on nutrient enrichment. Previous researches showed that HABs phenomenon was happened at the Lampung Bay, especially Trichodesmium erythraeum and Pyrodinium bahamense (Widiarti, 2000). This study was focus on spatial distribution of phytoplankton around the Hurun Bay. Seventeen sampling sites were investigated for phytoplankton assessment and the result showed that a high phytoplankton distribution was found close to coastal area and getting decreased toward offshore. This phenomena was support by total phosphate concentration where their high concentration was found close to coastal area. During the observation, it was found that Leptocyindricus dominate the area beside Chaetoceros, which was also dominance at the station 8. Total nitrogen and dissolved oxygen distribution were almost the same among those stations. Furthermore, it could be concluded as well that Hurun Bay was tend to phosphate limited area. Key words : phytoplankton, HABs, nutrients 1. Introduction Spatial distribution of marine phytoplankton is affected by several ecological factors. One of those important factors is nutrient, which was also explained by Beardall (2001) (1). He said that aquatic primary productivity is frequently limited by the availability of nutrients. Beside nutrients, several factors are also affected the present of phytoplankton in a coastal or estuary ecosystem. Those factors including nutrient loadings entering the estuary via freshwater flow, nutrient ratios and concentrations, light attenuation, tidal mixing, stratification, retention time and exchange with the coastal boundary (2). Beside those ecological factors, human activities around the coast and in the open sea were also have significant impacts to the distribution of phytoplankton in a coastal or marine waters. Since the increase of Harmful Algal Blooms throughout the coastal waters of the world (3), people pay more attention on nutrient enrichment loading to an ecosystem. Beside daily waste from domestic activities, mariculture and others aquaculture activities in coastal and marine area could also supply a lot of organic waste to an estuary or marine ecosystem. Furthermore, this organic waste will increase nutrient loading to the ecosystem. This phenomena is called as eutrophication (nutrient enrichment). Spatial Distribution...J. Hidrosfir Indonesia Vol. 3 (2) :

2 Several negative impacts could be happened because of the eutrophication. One of the negative impact is hypoxia, a phenomena of oxygen decreasing in a water coloumn that could kill any biota who are living in. Joice (2000) (4) explained hypoxia as a low-oxygen condition that can be stressful or fatal to marine life. Beside the fact that algal blooms phenomenon of Trichodesmium erythraeum was happened at the Lampung Bay in 1991 (5) and considering the potential blooming in coastal or estuarine waters, especially because the impacts of mariculture and other human actitivites, it is important to assess the distribution of phytoplankton around the Hurun Bay. Adnan explained that the blooming of T.erythraeum was causing negative impacts to shrimp ponds cultures along the east coast of Lampung. A lot of shrimp were died due to hypoxia and economical losses affecting local fishermen. As a part of a whole Hurun Bay ecological assessment investigation, this paper will only discuss the spatial distribution of phytoplankton from surface layer and their relationship with some ecological informations, such as nutrient, chlorophyll and dissolved oxygen. 2. Methods The whole Hurun Bay was investigated several times for some ecological parameters. This phytoplankton investigation was a part of the whole investigation program.the phytoplankton survey was separate from dissolved oxygen, nutrient and chlorophyll measurement. Samples were collected from seventeen stations (station 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14, 15, 16, and 17(Fig.1). For phytoplankton assessment, water samples were collected with a parallon pipe with 2 liters water volume. Five-hundred milliliter water sample from each station were collected in seventeen bottles after added with Lugol solution. Settling method was used to get a number of phytoplankton cells from every station. Those five-hundred milliliter samples were placed on seventeen 250 ml measuring glass and settled for 5 days. After 5 days, 230 ml liquid from every measuring glass were sucked. The less 20 ml samples from every measuring glass were poured to 17 storage bottles. Those 17 measuring glasses were poured with another 20 ml aquadest and then poured to every storage glass as dilution solution. Another 20 ml aquadest was poured to every storage bottles to clean the measuring glass and get a dilution factor number of 0.5. One milliliter of solution sample from every storage bottles were placed in a Sedwick- Rafter settling chamber and phytoplankton composition were analyzed under a light microscope (Nikon E-400). Phytoplankton numbers were counted with the equation below (6) :...(1) where N = number of cells per sample concentrate n = number of cells foundd in the Sedgwick Rafter A = total area of Sedgwick Rafter (mm 2 ) a = total area of Sedgwick Rafter which are determined during the observation (mm 2 ) V = total volume of concentrate (ml) v = total volume of Sedgwick Rafter (ml) d.f.=dilution factor Surface waters information of chlorophyll a and dissolved oxygen (DO) were analized with a set of probe (Chlorotec, type AAQ1183, Alec Electronics) whether nutrient (Total Dissolved Nitrogen and Total Dissolved Phosphorous) were analyzed in Japan after preserved and stored freezing at 30 0 C with a BRAN LUEBBE Auto Analyzer IV (7). 52 Darmawan R.A. 2008

3 Figure 1. Sampling Stations at the Hurun Bay 3. Result A high abundance of total cell numbers were found mainly around the Balai Budidaya Laut (BBL) area (station 4, 5, 6, 7 and 8) ( (Fig.2), whether total phytoplankton samples showed a domination of Leptocylindricus (Fig.3). At the highest concentration area, the total phytoplankton cells number were between cells/l. Regression linear lines of chlorophyll and phytoplankton showed a same trend, where their concentrations were getting decreased toward offshore (Fig.5). Dissolved oxygen (Fig.6) and Total nitrate concentrations (Fig.4) were almost the same at all stations whether Total Phosphate concentrations were getting decreased toward offshore. Figure 2. Phytoplankton abudance at the Hurun Bay Spatial Distribution...J. Hidrosfir Indonesia Vol. 3 (2) :

4 Figure 3. Phytoplankton composition at the Hurun Bay Total N (ug/l) Total P (ug/l) Figure 4. Nitrate (left) and Phosphate (right) concentration at the Hurun Bay 54 Darmawan R.A. 2008

5 Figure 5. Linear Regression of Chlorophyll and Phytoplankton at the Hurun Bay DO (mg/l) Figure 6.Dissolved oxygen concentration at the Hurun Bay 4. Discussion The data from the phytoplankton survey results showed a high phytoplankton cell concentration closed to estuary and at the area where high load concentration of organic waste or nutrient produced. This condition was also supported with decreasing trend of total phosphate toward offshore. Widiarti (2000) (8) was also found the same condition, where high phosphate concentration was found around the river mouth compare to offshore. Domination of Leptocylindricus during the observation was especially found around the mariculture area (Fig.3). High concentration of Chaetoceros was mainly found at the station 8, although Widiarti (2000) had found that at the Hurun Bay, Skeletonema could preceded the blooming of Pyrodinium before continuing with Chaetoceros. This temporary sampling might cause a lack of time series information or the succession pattern of phytoplankton community around the study area. The constant dissolved oxygen concentration almost at all stations (Fig.6) showed that there is no significance influence of organic matter, whether produced naturally or produced by impact Spatial Distribution...J. Hidrosfir Indonesia Vol. 3 (2) :

6 of human activities (such as mariculture, domestic waste, etc.), to any degradation process which might be affecting oxygen concentration. According to Caraco (1987) the N:P ratio in average of 15 stations (19.95:1) tends to consider as phosphate limited, although Schindler (1977 in Caraco 1987) found that in general, the ratio of available N:P in saltwater system normally tends to be equal or lower than the Redfield ratio (N:P = 16:1). Table 1. Total N, Total P and N:P Ratio at 15 stations in the Hurun Bay 5. Conclusion Although it is not a complete research, some information was gathered from this study. First, it was shown already that high abundance of phytoplankton cells was found closed to coastal area and getting decrease toward offshore. This information was also supported with the trend of phosphate concentration, where a high concentration was found close to coastal area and getting decreased toward offshore. The second, although it is not clear already, there is a tend to consider that Hurun Bay waters is a phosphate limited area but an advance study is needed. Acknowledgment I thank the joint cooperation of CMES- BPPT and BBL Lampung project on the Carrying Capacity Assessment on the Mariculture Area at the Hurun Bay, Lampung, who gave me an opportunity to assess this phytoplankton distribution study. References 1 Beardall,J., E. Young and S. Roberts Approaches for determining phytoplankton nutrient limitation. Aquatic Science 63: Fitzpatrick, J.J., M.B. Meyers. A Review of Methodologies for Use in Determining Nutrient Criteria in Coastal and Estuarine Systems. 3. Gastrich, M.D Harmful Algal Blooms in Coastal Waters of New Jersey. New Jersey Department of Environmental Protection, Division of Science, Research and Technology. 4. Joice, S The Dead Zones: Oxygen-Starved Coastal Waters. Environmental Health Perspectives, Vol.108:3. 5. Praseno, J.P. and Sugestiningsih Redtaid di Perairan Indonesia. Pusat Penelitian dan Pengembangan Oseanologi LIPI. 6. Darmawan, R.A Influence of Eutrophication on the Phytoplankton Assemblage of Jakarta Bay, Indonesia. Master Thesis. University of Bremen. 7. Santoso, A. D A Study on the Hydrography and Water Quality in the Tropical Aquaculture Field, Hurun Bay, Indonesia. Master Thesis. Ehime University. 8. Widiarti, R., R.F.Kaswadji and H.M.Eidman Succession pattern of Red Tide causing organism, Pyrodinium bahamense Plate, in Hurun Bay, South Lampung. JSPS- DGHE International Symposium. 56 Darmawan R.A. 2008