PhYToPLAnKTon SPecIeS coMPoSITIon In SeAWATeR AnD TISSUe oF GReen MUSSeLS ( PERNA VIRIDIS ) , AT KALI BARU-cILIncInG , noRTh JAKARTA

Species composition and abundances of phytoplankton in the shellfish farming area in Jakarta Bay, Kali Baru-Cilincing, were examined in order to identify harmful algae species. Phytoplankton contained in the shellfish was also observed to detect the presence of toxic species, as well as the phycotoxin contained in visceral of green mussel (Perna viridis) collected from the farming area using brine shrimp lethality test (BSLT). We detected the presence of Alexandrium spp. (PSP causing species), Dinophysis caudata, D. miles and D. rotundata (DSP causing species), and Pseudo-nitzschia spp. (ASP causing species). The last mentioned species was also detected in the stomach content of green mussel. The toxicity of green mussels tested was recorded LC50 ≤ 1,000 ppm and indicated the presence of an active compound in the green mussel viscera. Meanwhile, preliminary PSP test of shellfish did not showed any toxin.


InTRoDUcTIon
Jakarta Bay is known as a productive area for fishery aquaculture, especially green mussel (Perna viridis), which is mainly cultured at farming area of Kali Baru-Cilincing, North Jakarta.However, phenomena related to harmful algal bloom (HAB) species have commonly occurred in Indonesian waters (Praseno, 1995;Praseno et al., 1999).Kali Baru-Cilincing is also known to have high eutrophication levels and occurrences of HAB responsible species.For safe seafood production and prevention of economic loss due to HAB events, it is important to conduct routine monitoring on phytoplankton composition and detection of toxin contamination in green mussel that produced by toxic phytoplankton.This is the case of North Jakarta, because the area is the main green mussel farming sites in Jakarta, and also the main source of livelihood for the surrounding society.The objectives of the study are to detect the presence of toxic phytoplankton in the waters and inside the green mussel viscera, and to detect the presence of phycotoxin contamination in green mussel viscera using brine shrimp lethality test (BSLT) method and Jellet Rapid PSP Test.

MATeRIAL AnD MeThoDS
Nine sampling stations were set up in the green mussel farming area of Kali Baru-Cilincing, North Jakarta (Fig. 1).Samples of phytoplankton and green mussels were collected on 27 May 2012.Plankton samples were taken vertically from 3 meter in depth using a plankton net (mesh 20 mm).For identification and cell number numeration, 1 ml of each sample was put on Sedgewick-Rafter cell counting chamber and observed under a light microscope (Nikon SE, Japan).Species composition of phytoplankton contaminated in shellfishes, were examined from the viscus of a green mussel after being separated from other organs, and the stomach content was homogenized in 100 ml seawater.The solution was filtered through series of sieves (125 mm and 20 mm), and phytoplankton included in the residue on 20 µm mesh were identified under the same microscope mentioned above.
Toxicity in green mussel contents was tentatively checked by brine shrimp lethality test (BSLT).A concentration series of crude extract, which was already extracted from samples, were subjected to 10 individuals of Artemia salina nauplius, and the lethality of nauplii was recorded.Forty individuals of green mussel from three sampling stations were used for the test.Values of median lethal concentration (LC 50 ) were obtained from probit analysis.Extract was recognized to be toxic when LC 50 values were below 1,000 ppm (Harmita and Radji, 2004).
Paralytic Shellfish Poisoning (PSP) toxin contamination in green mussel was discerned by Jellet Rapid PSP Test for PSP (Jellet Biotek Ltd, Nova Scotia, Canada).Homogenized 100 ml of green mussel puree was suspended into buffer solution, then dropped onto the test strip.After 35 min, positive PSP contamination (single line) or negative (double lines) were judged.
The BSLT result by probit analysis showed that the green mussels contained active compounds with toxic properties, and LC 50 with values 116.3, 125.2 and 96.3 ppm, respectively.
The Jellet Rapid Test for PSP toxin in green mussels indicated a negative result or there was no saxitoxin detected inside green mussel viscera.

DIScUSSIon
At Jakarta Bay, the DSP causative species (Dinophysis spp.) and the ASP responsible species (Pseudo-nitszchia spp.) have long been detected (Praseno and Sugestiningsih, 2000).Several species of potentially toxic phytoplankton were also identified in the present study, i.e.Alexandrium spp., Dinophysis spp.and Pseudo-nitzschia spp., of which Pseudo-nitzschia spp.were abundantly found in samples (98,511 cells/ml in average).For Alexandrium spp.and Pseudo-nitzschia spp., we could not identify to species level.Since some species in these genera have been known to be toxin producer, while others not, species identification of Alexandrium spp.using thecal plate observation, and of Pseudo-nitzschia using electron microscopy were required to record the exact HAB related species composition in Jakarta Bay.
Crude extracts of green mussel viscera from Kali Baru-Cilincing was considered to contain toxic compounds, at least for nauplii of A. salina.Possible origin of the active compound in green mussels viscera was toxic phytoplankton found in seawaters around the shellfish farming area.Toxin produced by the phytoplankton was accumulated in green mussel tissues, and poisonous when being consumed (Tait and Dipper, 1998;Anderson et al., 2001).Since toxic phytoplankton found in the area were Alexandrium spp.(PSP causatives), Dinophysis spp.(DSP causatives), and Pseudonitzschia spp.(ASP causatives), the saxitoxin, okadaic acid and domoic acid produced by these HAB species were one of the possible source of active compound in green mussels.However, Jellet PSP Rapid Test showed negative results, indicating absence of saxitoxin in green mussel.Cell concentrations of Alexandrium spp. in water column were also found low (2.94 cells/ml).Phytoplankton cells abundantly contained in shellfish tissue were Pseudo-nitzschia spp., whereas cells of Dinophysis spp.were not detected in green mussel viscera.Based on the results, it was likely that the active compound in green mussel might be domoic acid produced by Pseudo-nitzschia.In any cases, detailed toxin analysis will be required for the safety seafood production in Jakarta Bay.

Table 1 .
Abundance of HAB related phytoplankton (cells/ml) at each station (Station 1-9) in green mussel farming area at Kali Baru -Cilincing, North Jakarta