OCCURRENCE OF PSEUDO-NITZSCHIA SPECIES ( BACILLARIOPHYCEAE ) AT KUCHING ESTUARIES FROM YEAR 2007 TO 2010

Pseudo-nitzschia. Bloom Occurrence of Pseudo-nitzschia Cell abundance was determined by microscopic enumeration. Temperature, pH, salinity and macronutrients at the sampling sites were determined at each sampling occasions. Highest cell density of Pseudo-nitzschia spp. was 3 cells L P. brasiliana 4 cells L). Increase in cell abundance was coincided with high salinity and low precipitation rate. Water Pseudo-nitzschia spp. The result obtained Pseudo-nitzschia species in the tropical estuarine waters.


INTRODUCTION
Pseudo-nitzschia is one of the main genera Pseudo-nitzschia been documented worldwide, with some species et al., of Pseudo-nitzschia has been recorded thus far, showed high species richness of Pseudo-nitzschia (Lim et al Teng et al., accepted).Bioac-cumulation of DA through the food web had been caused the death of marine mammals and birds (Scholin et   estuarine waters and its nutritional conditions of Pseudo-nitzschia.Sampling was carried out fortnightly and water physico-chemical parameters were measured in-situ.Field and culture samples of Pseudo-nitzschia transmission electron microscopy.

Study areas and sampling
Fortnightly samplings were carried out in San-Fisheries Department (Santubong and Samariang Branch).Sampling site in Santubong located at the area.Sampling station of Samariang is located upstream of Samariang estuary.The area is prone to domestic waste (solid or liquid) from Surface water samples were collected by samples in duplicates were stored in bottles with for further analyses.Water physical parameters, i.e.: pH, temperature and salinity were measured in-situ using HANNA electronic pH meter (Hanna Instrument, USA) and AGATO hand refractometer (Agato, Japan).

Sample preservation and macronutrient analysis
Filtered water samples for nutrient analysis Nitrate-nitrogen (NO 3 (PO 4 3--P) and silicate (SiO 2 ) in water samples spectrophotometer (HACH Company, Colorado, NO 3 --N concentrations were determined at analyzed using PhosVer3 (Ascorbic Acid) Method Heteropoly blue method was used to determine SiO 2 concentration in the sample.

Cell enumeration
counting chamber under a Leica compound light out in triplicate.Pseudo-nitzschia cells found in the samples were counted using tally counter and manually recorded.Species enumeration and identification through light microscopy was conducted based on common features of Pseudo-nitzschia microscopy.The morphological characteristics tened and elongated, and presence of chloroplasts in each polar according to description by Hasle et al. (1996).

Data analysis
Cell density and physico-chemical readings were input into the statistic program Graphpad t statistical analysis was method of principle component analysis (PCA) and distribution of Pseudo-nitzschia composition.The data were transformed to log (x precipitation rate of Kuching were obtained from the Meteorology Department of Malaysia.Precipitation was measured in millimeters (mm).
Occurrence of Pseudo-nitzschia was less Pseudo-nitzschia 4 cells L -1 L -1 estuary remained low to absent throughout the study period (Fig. 3).

Water physical data in the two estuaries
Salinity in Santubong (Fig. 4a) ranged in Samariang was mainly due to its location, at the -Water temperature of Santubong (Fig. 4c) and tropical water.Similar to salinity, water temperature was slightly lower when samples were collected during the day with high precipitation.There was no much difference in water temperature at the the water temperature and Pseudo-nitzschia cell densities (p tidal cycle in the areas.

Macronutrients
Nitrate-nitrogen concentrations at both -1 mg L -1 in Samariang (Fig. 5b).Both locations mg L -1 relationship with the nitrate-nitrogen concentration (p Phosphate concentration in Samariang was lower than Santubong.Low concentrations -1 -1 at each -1 but phosphate concentrations at was recorded in Santubong and Samariang.In Date of sampling L -1 was recorded before the concentration decrease (Fig. 5c).
In Samariang, sharp increase of phosphate -1 the cell densities in most sampling (p

Silicate concentrations in Santubong and
Santubong and Samariang ranged from below -1 (Fig. 5e) and 1.532 mg L -1 stimulated the growth of Pseudo-nitzschia in the two estuaries whereby high cell densities were always followed by decline in silicate.Silicate was enriched again particularly during end and early of of Pseudo-nitzschia occurrence coincided with decline in silicate concentrations and sometimes occasions when silicate slightly increased for a short period.

Monthly rainfall
in Fig. 6.Data showed precipitation occurred There are two main monsoon seasons, namely, west monsoon (May-September) and two short periods of inter-monsoon seasons.Kuching coastal season whereby precipitation rates are more pronounced in January (Fig. 6).High precipitation month were recorded during early and end of year.Minimum rainfall occurred in the month of June or July in each year.Annual precipitation read at Phosphate (mg L -1 Date of sampling

DISCUSSION
blooms in recent years has been attributed to coastal eutrophication and global climate change, in addition to better awareness and documentation Pseudo-nitzschia and threat to aquatic mammals and birds, but also to others is to determine factor inducing bloom and Pseudo-nitzschia, especially in temperate and subtropical regions.In this paper, one of the few studies on occurrence of Pseudonitzschia in the tropical waters is reported.
In the present study, Pseudo-nitzschia stepped cells in chain for enumeration under light as closely related species is differentiated based on minute structures of frustules and required the aids Pseudonitzschia species can be distinguished based on the sparse features of size and cell shape.In some studies earlier, Pseudo-nitzschia genus and counted as a whole, while some studies grouped different morphotypes based on their size ranges (e.g.  , 1996).High abundance of cosmopolitan P. pungens had been recorded during summer (Hasle et al., et al., 1996).Seasonal shifts of Pseudo-nitzschia in temperate waters suggested in temperature (Fehling et al Pseudonitzschia seriata of sea ice of the Arctic Ocean, as well as in the water column when they were released as the ice melts (Bates et al culture condition, Pseudo-nitzschia can tolerate a (Thessen et al throughout the study probably due to different pH at Santubong and Samariang estuaries were mainly due to intrusion of seawater during intertidal changes.High concentration of Pseudo-nitzschia 3 cells mL -1 ) 4 cells mL -1 ) was not affected by pH.Lundholm et al that marine and smaller Pseudo-nitzschia species could tolerate higher upper limit of pH for growth.In this study, smaller Pseudo-nitzschia cells were larger Pseudo-nitzschia cells in Santubong were the two forms of Pseudo-nitzschia spp.can described by Lundholm et al this study showed that Pseudo-nitzschia cells were lie in other factors such as higher precipitation rate especially the northeast monsoon season, depletion and competition of essential nutrients for growths their bloom in the area.In nutrient-enriched condition, pH was the limiting factor in algal growth (Lundholm et al low tide, hence the lower pH may again support the original idea that they were marine origin and their

Pseudo-nitzschia species can grow P. delicatissima can et al
Cell density of Pseudo-nitzschia spp. at both estuaries was affected by monthly precipitation rates.This close relationship was also supported by the PCA analysis whereby rainfall was Pseudo-nitzschia at Santubong and Samariang.Low cell density of Pseudo-nitzschia spp.during precipitation may probably due to high freshwater dilution rate and decreased light penetration as a consequence of increase in total suspended solid, thus increased turbidity and reduced water transparency.Increased concentration of Pseudo-nitzschia decrease in monthly rainfall, and the abundance was sustained in dry season of May-September.This is coincided with other studies conducted in Thailand and Philippines, where Pseudo-nitzschia cells appeared during December-May, with low the main aspects, which determined different influenced by the light regimes (Gilstad and raining period may responsible for the absence of Pseudo-nitzschia cell densities as a result from -2 -1 was required for optimal reproduction in P. multiseries has been reported to be affected by photoperiod as well (Hiltz et al., Pseudo-nitzschia cells were also reported in low irradiance to aphotic zone (Trainer et  no cell of Pseudo-nitzschia at the concentration was slightly higher than phosphate but much lower compared to silicate.Absent of Pseudo-nitzschia cells at highest concentration of -1 was recorded in Samariang.This may indicate that nitrate-nitrogen may not be the main factor that triggers the growth of Pseudonitzschia spp. in this study.According to Klein et al P. delicatissima and P. fraudulenta abundance is related to high concentration of P. americana, P. australis, and P. pungens did not affected by the amount the requirements for DA production in Pseudonitzschia spp.(Bates et al., 1991).
Pseudo-nitzschia is capable of utilizing both organic and inorganic form of nitrogen sources (Howard et al of nitrogen sources commonly found in the natural P. australis cultures growth -1 ) in either nitrate or ammonium used as the sole nitrogen source (Howard et al., clear (Maguer et al conducted by Hillebrand and Sommer (1996), P. multiseries (Hillebrand and Sommer, 1996).

Despite the absence of correlation between
Pseudo-nitzschia cell densities with nitrogenous concentration in both estuaries, loadings of urea from the adjacent human habitation into the estuarof P. multistriata regulated by the concentration of urea In this study, the smaller size Pseudo-nitzschia was always predominant compared to the bigger counterpart.Two or more Pseudo-nitzschia spp.
In this study, Pseudo-nitzschia tended to be found after a period of high precipitation followed occurrence of Pseudo-nitzschia at the Santubong intense in number of cells in the recent years.Similarly, Pseudo-nitzschia species was reported Pseudo-nitzschia tends to appear in continental 6 cells L -1 ) compare to estuaries (Dortch et al et al Pseudo-nitzschia was only encountered in 53 the two estuaries.Two Pseudo-nitzschia spp.
Pseudo-nitzschia was the most commonly found in the samples.Pseudo-nitzschia cell densities at 4 cells L -1 small-sized Pseudo-nitzschia the estuary.The density in Samariang during the 4 cells L -1 ) was 3 cells L -1 ) record. Pseudo-nitzschia in April to September.Simultaneous emergence of Pseudo-nitzschia was recorded at both estuaries in May each year.A study on Pseudo-nitzschia Bay, Sabah showed that Pseudo-nitzschia cells were present during the whole year and most abundant between October-December and were lowest in March until May, which contradicted to the sampling location whereby the abundance Pseudo-nitzschia were reported to be higher in the shelf compare to the estuaries (Dortch et al Figure 1.

Figure 4 .
Figure 4.In situ physical data of salinity (a, b), temperature (c, d) and pH (e, f) at Santubong and Samariang estuary

Figure 5 .Figure 6 .
Figure 5. Macronutrients (nitrate-nitrogen, phosphate, silicate) reading at Santubong and Samariang estuary from Figure 7.Pseudo-nitzschia from low-nutrient water into the more nutritious bottom layer (Trainer et al et al et al Pseudo-nitzschia species with small cells (Fehling et al CONCLUSION Pseudo-nitzschia cell commonly be found in low precipitation months from April to September.May each year.Apart from the precipitation rate, the cell density has apparently affected by the silicate.The two Pseudo-nitzschia species found in in Malaysian waters particularly at the estuarine waters.
To gain insight in the bloom dynamics of Pseudo-nitzschia species, long term studies In the coast of US, blooms of Pseudo-nitzschia spp.occurred in response to nutrient enriched waters from spring runoff (Heisler et al et al et al et al., to lower Si:N and Si:P in coastal waters due to et al., density of Pseudo-nitzschia at Santubong