TEMPORAL VARIATION IN CERATIUM SPP. ABUNDANCE RECORDED IN JAKARTA BAY

Ceratium species in the coastal waters around the world. Eventhough research and monitoring on phytoplankton Ceratium community. Therefore, a research was set up in order to understand the dynamic of Ceratium population and its regulating factors. A serial sampling was conducted in 10 stations during 2009 and 2010. Phytoplankton was sampled in horizontal towing using Kitahara plankton net (80 μm mesh size, 0.5 m Fraction Method on Sedgewick Rafter Counting Chamber (SRCC). The result showed clear temporal variations in Ceratium absolute density, relative density, relative frequency and importance value. When phytoplankton bloomed in August 2009, no Ceratium bloom observed. High density of Ceratium was observed in November 2009 and May 2010, but it contributed relatively small proportion to phytoplankton as a whole (relative density <1%). Due to its low density and relatively limited distribution in Jakarta Bay, Ceratium may demonstrate limited ecological role to the phytoplankton community.


INTRODUCTION
Ceratium problems in many aquatic ecosystems (Praseno and Sugestiningsih, 2000;Orellana-Cepeda et al., 2002;Baek et al., 2008a, b;Baek et al., 2011).Some species of Ceratium such as Ceratium furca and C. fusus were regarded as the most common bloom-forming species in the coastal waters around the world.Persistent and frequent blooms of Ceratium have been reported in many oceans including the North Sea, the North Atlantic Ocean, the Indian Ocean, and the South Eastern Asia.Many of those blooms have severed on the aquatic ecosystem and coastal communities.One common phenomenon due to Ceratium blooms

Ceratium
Such cases have been recorded in Todos Santos Bay, Manzallino and South Africa (Orellana-Cepeda et al., 2002).Similar to most cases of phytoplankton blooms, blooming of Ceratium is triggered by nutrient enrichment including nitrates, nitrites, phosphates and silicates.Warm water and relatively low water turbidity are also important triggering factors (Orellana-Cepeda et al., 2002;Baek et al., 2008a, b;Perez-Martinez & Sanchez-Castillo, 2001).
Jakarta Bay is a shallow water coastal ecosystem, located at the northern side of Jakarta, the capital city of Indonesia.It has been known as eutrophicated and polluted aquatic ecosystem.
Most pollutants and nutrients are discharged by 2012).Eutrophic condition has resulted in frequent cases of phytoplankton bloom and mass fish mortality (Thoha et al., 2007;Sidabutar, 2010).
rently with phytoplankton blooming which cause blooming in May and September 2007 in Jakarta Bay, Skeletonema and Chaetoceros have been Ceratium distributes relatively wide over the bay, but its density was very low (Thoha et al., 2007).
Monitoring on phytoplankton blooms in this area has been continuously carried out but no variation of Ceratium abundance in the system.Consequently, there was no adequate information on the ecological roles of Ceratium in phytoplankton community on this area.Thus, a study has been set up to understand the dynamic of Ceratium spp. in Jakarta Bay and its possible relationship with other phytoplankton genera, from which the results are presented in this paper.

Phytoplankton Observation and Counting Methods
Phytoplankton enumeration was done by taking 0.1 ml fraction from the sample with stample pipette.Such small volume of sample The sample fraction was placed on a Sedgewick Rafter Counting Chamber (SRCC) and observed under Nikon Diaphot inverted-phase contrast and other phytoplankton, referring to Praseno and In this research, our focus was the Ceratium genus.The number of Ceratium and other phytoplankton cells in the samples were counted and then converted into cell.m -3 by equation following Arinardi (1997).The data were further analyzed by generating biological parameter of all phytoplankton genera, such as relative density, 1976).

Relative density was calculated according to
Relative Density =

……………………. (1)
Frequency and relative frequency were often used to quantify the spatial distribution of particular phytoplankton genus proportionated to other genus.These values, according to Kohli et al. (2013), could show genera with either widespread or limited distribution.Both frequency and relative frequency were calculated using equations adopted  (1997).This analysis was conducted by operating Biodiversity Professional ver. 2.

Temporal Variation on Ceratium Biotic Parameters
In general, it was found that Ceratium density, relative frequency, and importance value were higher during September-November 2009, compared with June-August 2009 (Fig. 2).Similar trend was also observed in 2010 (Fig. 2).Total absolute density from 10 sampling stations was The lowest value was observed in October 2009 (104,582 cells.m -3 ) and the highest was observed in May 2010 (1,191,273 cells.m -3 ) (Table 1).The Ceratium total density (Fig. 2A) was different from its relative density (Fig. 2B).In this research, Ceratium relative density was very low (< 1%) compared with other phytoplankton genera in Jakarta Bay (Table 2).Based on those value there was no Cera-tium bloom observed in Jakarta Bay during the research period.Even during phytoplankton bloom in August 2009 (Fig. 3), Ceratium total density was much lower than other non-blooming genera, such as Bacteriastrum, Stephanophyxis, and Thalassiosira (Table 1).During the phytoplankton bloom event in August 2009, Ceratium total density was only 514,909 cells.m -3 .On the other hand, the density of two blooming phytoplankton genera, Nitzchia and Chaetoceros, were over 10 9 cells.m -3 a month before and after blooming (Table 1).
The result showed that Ceratium relative density was higher during September-November 2009 period, compared with that of during June-August 2009 and that of during May-July 2010 (Fig. 2B).The highest Ceratium relative density was observed in November 2009, with value of 0.35%, while the lowest was observed during phytoplankton bloom event in August 2009, with value of 0.01% (Fig. 2B).Although occurred in very low relative density, Ceratium were always present in Jakarta Bay (Table 2).
Protoperidinium (Table 2).The data showed a possible relationship between high Ceratium density and the absent of Nitzschia in Jakarta Bay during May 2010 (Table 1).Based on the pattern in Ceratium total absolute density, it seemed that Ceratium demonstrated repeating cycle, with low density condition occurred between two high density conditions (Fig. 2A).This trend was not observed in the dynamic of its relative density, relative frequency, and importance value (Fig.

2B, 2C, & 2D).
The value of relative frequency, which represented the rate of occurrence of Ceratium in A decline in Ceratium relative frequency was observed during June to August 2009 (Fig. 2C), which was similar to the pattern in its relative density (Fig. 2B).The highest Ceratium relative occurrence frequency was observed in September 2009, and the lowest was observed in August 2009 (Fig. 2C), which coincided with phytoplankton bloom event in Jakarta Bay (Fig. 3).Based on Fig. 4, it was clear that Ceratium was always present in station 1 and 2. The area with the highest Ceratium density was found around those two stations, while the lowest density was found in the water around station 4 and 5. Based on the value of Ceratium relative frequency (Fig. 2C) and distribution pattern, it was found that Ceratium have a wide distribution in Jakarta Bay during September 2009, compared with other months.In September 2009, Ceratium could be found in all sampling stations in Jakarta Bay.The result also suggested that Ceratium tended to be found in higher density around western area of Jakarta Bay.
In general, Ceratium importance value was very low compared with other phytoplankton   genera as a whole (Fig. 2).This value was declining during June to August 2009 period, which was similar with the pattern of its relative density and relative frequency.The highest Ceratium importance value was observed in September 2009, with only 4.49%, while the lowest importance value was observed in August 2009 (1.55%).
Based on Bray-Curtis clustering analysis, it was found that Ceratium distribution pattern in Jakarta Bay during this research periods was very similar with Protoperidinium (over 80% similarity) (Fig. 5), also with some common diatoms of Jakarta Bay such as Rhizosolenia, Nitzschia, Stephanopyxis, Thalassiosira and Chaetoceros.

The Existence of Other Phytoplankton in Jakarta Bay
The dominant phytoplankton genera in Jakarta Bay during this research period were diatoms, with Chaetoceros and Stephanopyxis occurred  when Nitzschia population bloomed with total absolute density over 3×10 9 cells.m -3 (Table 1), and became the dominant phytoplankton genera in the bay (Table 2).During this blooming period, Chaetoceros density also reached over 10 9 cells.m -3 (Table 1).
Alexandrium and Protoperidinium were two genera that have relatively high abundance in (Table 1, 2).Protoperidinium was observed in Jakarta Bay during the entire research period, while Alexandrium was only found during September-November 2009, but total density reaches over 5×10 6 cells.m -3 in October and November 2009 (Table 1).Similar with Ceratium and Protoperidinium, Noctilluca always present in the bay.Noctilluca population was found reaching its peak in September 2009 after phytoplankton bloom event, with total absolute density of 637,818 cells.m -3 (Table 1) and relative density of 0.36% (Table 2).On the contrary, during the peak of Ceratium density in May 2010, Noctilluca population reached its lowest density (Table 2).Meanwhile, Gymnodinium which was always detected through the whole observed months, was absent during the phytoplankton blooming in August 2009.

DISCUSSIONS
Although Ceratium was also known as a common bloom-forming phytoplankton in coastal ecosystems (Baek et al., 2008a, b), there was no Ceratium bloom observed during this research period.Even during phytoplankton bloom in August 2009, with total density over 10 9 cells.m -3 , Ceratium total density remained far below blooming threshold according to Spatharis and Tsirtsis (2010).A peak in Ceratium total absolute density was observed in May 2010, but this peak was not regarded as a Ceratium bloom event.Based on the general cause of phytoplankton bloom in most coastal ecosystem (Glibert et al., 2002;Baek et al., 2008b), a bloom event that occurred during August 2009 in Jakarta Bay was probably related to high nutrient concentration in the water.This nutrient enrichment might come from many rivers that event in August 2009 might be an anomaly since it was occurring during dry season.Lower rainfall in dry season should reduce the nutrient input from the rivers and surface run-offs, and in consequence it should prevent any phytoplankton to bloom.
The lack of Ceratium bloom even during hypothetical eutrophic water condition in August reproductive rate compared to diatoms in the bay (Hikmah, 2010;Smayda and Trainer 2010;Baek et al., 2008b;Baek et al., 2011).It was possible that Ceratium population was unable to compete with the rapid growth of Nitzschia and Chaetoceros during the hypothetical eutrophic condition in August 2009.Termination of phytoplankton blooming in September 2009 might be caused by nutrient such as Ceratium, had an ability to grow and reach high cell density in oligotrophic water condition (Baek et al., 2009b;Alkawri and Ramaiah, 2010).Therefore, Ceratium had a chance to increase its population during hypothetical nutrient depletion event in September 2009.The lowest Ceratium density was observed in October, which also coincided with lowest total phytoplankton density in the bay.This condition might be the result of prolonged nutrient depleting condition in the water.Based on the result of this research, there seemed to be a correlation between Ceratium highest density in May 2010 and the absent of Nitzschia in the bay.But this correlation needed to be studied further.
The Bray-Curtis analysis in this research also indicated that Ceratium temporal variation in its density and distribution seemed to have similar pattern with Protoperidinium and some common diatoms, such as Rhizosolenia, Nitzschia, Stephanopyxis, Thalassiosira and Chaetoceros in Jakarta Bay.This closely similar group (> 70% similarity) indicated that those genera might have similar niche in the community; thus they might also form some biological interactions.This biological interaction probably occurred in the form of competition, especially for nutrients in the water of Jakarta Bay.This hypothetical interaction Although Ceratium was considered common phytoplankton for Jakarta Bay (Thoha, 2010;Sidabutar, 2010), it was present in very low density and with relatively restricted distribution in most sampling periods.Ceratium distributed widely in Jakarta Bay only in September 2009, one month after phytoplankton bloom occurred in the bay.Based on the result, Ceratium population was likely to have clumped distribution type, since its distribution was centered mainly on western area of Jakarta Bay.This type of distribution might occur due to the pattern of currents in the bay, which could cause the Ceratium population to aggregate around western area.Research by Hadikusumah (2007) suggested that surface current of Jakarta Bay varied depending on the season.In general, water current of Jakarta Bay was circulating inside the bay during dry season (June-August) and transitional II season (September-October).The surface water current during those seasons the bay during transitional I season (March-May) (Hadikuksumah, 2007).This physical factor might limit the distribution of Ceratium in the bay.However, it was unknown why its distribution was much wider during September 2009.
Ceratium plays an important role as one of the main substantial part of annual primary production in most marine ecosystem.It was grazed Protoperidinium and some herbivory copepods (Olseng et al., 2002;Baek et al., 2008b;Baek et al., 2011).Despites its important ecological role, Ceratium population in Jakarta Bay seemed to have little value to the ecosystem.Unlike in some temperate coastal ecosystem such as Sagami Bay -Japan, Southern California Bright -USA, and Jinhae Bay -Korea, Ceratium in this tropical ecosystem of Jakarta Bay was suggested to have community of the bay (Orellana-Cepeda et al., 2002;Baek et al., 2008;Baek et al., 2011).Thus it was doubtful whether Ceratium could actually cause severe ecological problem such as red tide as the ecosystem has been heavily affected and frequently enriched by anthropogenic activities, as Ceratium could take over the diatoms in a phytoplankton blooming event and cause problem in the future.

CONCLUSIONS
From this research, it could be concluded that there were three different Ceratium population dyduring June to August 2009, the second occurred during September to November 2009 and the third trend occurred during May to June 2010.The lack of Ceratium bloom during hypothetical eutrophic water condition in August 2009 might be related to its slow reproductive rate and competition with blooming Nitzschia.Although Ceratium was considered as common phytoplankton of Jakarta Bay, the density was very low and the distribution was relatively limited; thus it assumed that Ceratium role in the ecosystem of the bay.

Figure 1 .
Figure 1.Sampling sites around Jakarta Bay, which is located around Pluit, Bidadari calculated to measure the importance of one genus of phytoplankton and Importance value = …….…….. (4) Bray-Curtis clustering analysis (group average link) was then conducted using phytoplankton density data collected from all stations during the study periods, referring to McAleece et al.

Figure 3 .
Figure 3. Phytoplankton absolute density in Jakarta Bay during June to November 2009 and Mei to July 2010.

Figure 4 .
Figure 4. Detail information on Ceratium absolute density in each sampling station in Jakarta Bay.

Figure 5 .
Figure 5. Bray-Curtis clustering analysis from temporal data of all phytoplankton genera in Jakarta Bay.Dashed line indicates 70% similarity.

Table 1 .
Total absolute density (cells.m -3 ) of all phytoplankton genera in Jakarta Bay during this research period.The total absolute density was counted by adding up cell density from 10 sampling stations during each sampling month.

Table 2 .
Relative density (%) of all phytoplankton genera in Jakarta Bay during this research period.