Seasonal changes in phytoplankton composition in an extensive fish culture area in Bolinao, Pangasinan, northern Philippines

The proliferation of fish cages and pens in Bolinao, Pangasinan, northern Philippines seemed to have reached its limit in 2002 when a massive fish kill coinciding with a bloom of Prorocentrum minimum occurred. Since then, various measures have been taken by the local government to decrease the number of fish cages to allow recovery of the waters of Bolinao. Samples collected in April, June and November 2004 representing summer, southwest and northeast monsoons, respectively, from five stations were analyzed for phytoplankton composition. Diatoms generally dominated the phytoplankton and peaked during summer which can be attributed to a very high concentration of Thalassiosira sp. constituting 92% of the phytoplankton in that season. The dinoflagellates constituted a small portion of the phytoplankton composition in all seasons. The flagellates represented a small fraction of the phytoplankton and followed the trend of the dinoflagellates. Cyanobacteria thrived during the wet seasons, almost co-existing with the diatoms. The results seem to suggest that the management of the fish cages or the aquaculture ponds might have resulted to changes in the present (2004) phytoplankton composition compared to previous years (1995-2002)

PSP in the Philippines : three decades of monitoring a disaster

Paralytic Shellfish Poisoning (PSP) caused by Pyrodinium bahamense var. compressum is of significant public health concern in the Philippines. Blooms of Pyrodinium occurred 135 times in 27 different coastal waters of the country between 1983 and 2005 with a total of 2,161 reported PSP cases and 123 fatalities. To address the growing problem on PSP a strategy to mitigate the impact has been implemented. PSP monitoring program has been in placed for more than two decades now. This paper summarizes the current status of occurrence and historical perspective of PSP in the Philippines and collaborative efforts done to improve the monitoring system

Domoic acid in a bivalve Spondylus cruentus in Nha Trang Bay, Khanh Hoa Province, Vietnam

Recently we have found that domoic acid (DA), a toxin responsible for amnesic shellfish poisoning, is always detected in bivalve species belonging to a genus Spondylus randomly collected from various parts of the tropical areas including Vietnam. In Vietnam, 10 species of Spondylus are known to grow. Among these species, S. cruentus is a commercially valuable species. Domoic acid in S. cruentus collected in Nha Trang Bay is analyzed by ELISA and LC/MS/MS. Remarkable individual difference was observed in DA level among 28 specimens of S. cruentus collected from the same area at the same time. The DA level in S. cruentus apparently showed a seasonal variation. However, the variation of DA content seems to be due to a large individual difference among the specimens. When the specimens were reared in plankton-free conditions, DA level in S. cruentus did not decreaseds for 45 days, showing that S. cruentus maintains DA for a long period

Seasonal variation of paralytic and amnesic shellfish toxicities in bivalves and microalgae in Haiphong area, Vietnam

Monitoring survey was conducted to know the distribution and seasonal variation of PSP and ASP toxicities in bivalves and the abundance of toxic microalgae in Haiphong area, Vietnam. Sampling was carried out at the stations in Cat Ba and Do Son every two weeks from February 2002 to March 2004. Low levels of PSP and DA were detected in shellfish samples from both stations, showing seasonal and yearly variation. Toxicity of plankton samples also showed fluctuation, though the clear correlation could not be observed with the shellfish toxicities. HPLC or LC-MSMS analysis provided clear evidence of shellfish contamination with these toxins and indicated the existence of causative microalgae for these toxicities in this area. Several species of Alexandrium such as A. minutum, A. tamiyavanichii, A. ostenfeldii, A. tamarense were found, though the abundance of them was very low. On the other hand, massive bloom of Pseudo-nitzschia occurred in January at both stations. However, these blooms did not always cause the increase of DA level both in plankton and shellfish samples

Seasonal variation of paralytic and amnesic shellfish toxicities in bivalves and microalgae in Haiphong area, Vietnam

Monitoring survey was conducted to know the distribution and seasonal variation of PSP and ASP toxicities in bivalves and the abundance of toxic microalgae in Haiphong area, Vietnam. Sampling was carried out at the stations in Cat Ba and Do Son every two weeks from February 2002 to March 2004. Low levels of PSP and DA were detected in shellfish samples from both stations, showing seasonal and yearly variation. Toxicity of plankton samples also showed fluctuation, though the clear correlation could not be observed with the shellfish toxicities. HPLC or LC-MSMS analysis provided clear evidence of shellfish contamination with these toxins and indicated the existence of causative microalgae for these toxicities in this area. Several species of Alexandrium such as A. minutum, A. tamiyavanichii, A. ostenfeldii, A. tamarense were found, though the abundance of them was very low. On the other hand, massive bloom of Pseudo-nitzschia occurred in January at both stations. However, these blooms did not always cause the increase of DA level both in plankton and shellfish samples

New stage of the study on domoic acid-producing diatoms : A finding of Nitzschia navis-varingica that produces domoic acid derivatives as major toxin components

We reported Nitzschia navis-varingica as a new domoic acid (DA)-producing diatom, and furthermore reported its wide distribution in Asian waters. However the surveys were performed only in limited area of each country. In order to obtain more detailed information, screening of N. navis-varingica was primarily performed in the Philippines. During the survey, we confirmed that all strains of N. navis-varingica isolated from Bulacan, Manila Bay did not produce DA, but did produce isodomoic acids A (IA) and B (IB). The confirmation of IA and IB was done by the analyses of UV-spectra, LC-MS/MS, proton NMR and ^C NMR. Re-observation of the toxin composition including IA and IB simultaneously with DA was performed on the former chromatograms. All the strains positive for DA and/or its derivatives isolated from estuary areas of Bacoor, Tanauan and San Roque, were confirmed to produced DA and IB, indicating that there is a local difference in toxin composition in the Philippines. All of the toxic strains were identified as N. navis-varingica. This is the first report of pennate diatom that produces IA and IB instead of DA as major toxin component. This finding might be a useful step in pursuing the DA production mechanism. Additionally fourty one Pseudo-nitzschia strains isolated from offshore areas of above mentioned estuaries were tested for DA, but all of them did not show any sign of DA production

Screening of diatoms producing domoic acid and its derivatives in the Philippines

Domoic acid is the known causative agent responsible for amnesic shellfish poisoning (ASP). Although there is only one documented ASP case in the world, there is a potential of its occurrence in Southeast Asian countries. However, limited information on domoic acid producing diatoms is available except for Nitzschia navis-varingica, which is known to produce significant levels of domoic acid. In order to obtain fundamental data on domoic acid producing diatoms, screening of Pseudo-nitzschia and Nitzschia species were primarily performed in the Philippines. Two source areas, i.e. Manila Bay and Iba estuary of Luzon Island, were selected for observation of these diatoms. Fifty eight isolates of Pseudo-nitzscia and 18 isolates of Nitzschia-like diatoms were prepared from Manila Bay and Iba estuary, respectively. These isolates were cultured and tested for the production of domoic acid and its derivatives. Pseudo-nitzscia strains did not show any signs of domoic acid production. Five out of 18 Nitzschia isolates were confirmed to produce isodomoic acids A and B. Comparison of sonication and boiling in water bath as extraction methods was investigated and results showed that both methods yielded comparable amounts of domoic acid. Stability of domoic acid extracted by boiling was also investigated and was found out to be stable at room temperature for ten days. Results implied an advantageous and convenient way of sample preparation and preservation for international transport

Distribution of dinoflagellate cysts in the surface sediment of the coastal areas in Chonburi Province, Thailand

Distribution of dinoflagellate cysts were investigated in rainy and dry seasons in the surface sediment of the coastal areas in Ang-sila, Bang-pra, Si-racha and Laem-chabang, Chonburi Province, Thailand. Sampling cruises were conducted in February and September 2005 that were during the dry and rainy seasons, respectively. Thirty types of cysts were found of which 28 cysts belonged to the orders Gonyaulacales, Gymnodiniales and Peridiniales and two were of unknown cyst types. The dominant species were Pheopolykrikos hartmannii and Pyrophacus steinii and the most common species were P. hartmannii, Gonyaulax spinifera (Spiniferites mirabilis), Lingulodinium polyedrum, P. steinii, Protoperidinium pentagonum and P. leonis. Dinoflagellate cysts were widely found in most stations of the study area. The total numbers of dinoflagellate cysts in dry season were higher than those in rainy season. The abundance of dinoflagellate cysts in both seasons was higher at the stations deeper than 10 meter around Ang-sila and Bang-pra areas than at the stations near Laem-chabang areas. These findings suggest that cyst abundance and distribution might be affected by seasonal changes of environment and fishery activity.Proceedings of the Horiba International Conference "New Direction of Ocean Research in the Western Pacific" : Past, Present and Future of UNESCO/IOC/WESTPAC Activity for 50 years and the JSPS Project "Coastal Marine Science"Section I: Research Articles/Harmful microalga

Distribution of dinoflagellate cysts in the surface sediment of the coastal areas in Chonburi Province, Thailand

Distribution of dinoflagellate cysts were investigated in rainy and dry seasons in the surface sediment of the coastal areas in Ang-sila, Bang-pra, Si-racha and Laem-chabang, Chonburi Province, Thailand. Sampling cruises were conducted in February and September 2005 that were during the dry and rainy seasons, respectively. Thirty types of cysts were found of which 28 cysts belonged to the orders Gonyaulacales, Gymnodiniales and Peridiniales and two were of unknown cyst types. The dominant species were Pheopolykrikos hartmannii and Pyrophacus steinii and the most common species were P. hartmannii, Gonyaulax spinifera (Spiniferites mirabilis), Lingulodinium polyedrum, P. steinii, Protoperidinium pentagonum and P. leonis. Dinoflagellate cysts were widely found in most stations of the study area. The total numbers of dinoflagellate cysts in dry season were higher than those in rainy season. The abundance of dinoflagellate cysts in both seasons was higher at the stations deeper than 10 meter around Ang-sila and Bang-pra areas than at the stations near Laem-chabang areas. These findings suggest that cyst abundance and distribution might be affected by seasonal changes of environment and fishery activity.Proceedings of the Horiba International Conference "New Direction of Ocean Research in the Western Pacific" : Past, Present and Future of UNESCO/IOC/WESTPAC Activity for 50 years and the JSPS Project "Coastal Marine Science"Section I: Research Articles/Harmful microalga

Is the archeopyle of Tuberculodinium vancampoae (Rossignol) (Gonyaulacales, Dinophyceae) on the hypocyst?

Volume: 2Start Page: 183End Page: 19