1999). In addition, cysts of toxic species such as Alexandrium PI3K inhibitor spp. and Gymnodinium catenatum may be more toxic than their motile vegetative cells ( Dale, 1978 and Oshima et al., 1992) and may therefore represent a source of paralytic shellfish poisoning (PSP) toxins ( Schwinghamer et al. 1994). Although studies of dinocyst distributions in marine surface sediments are increasing worldwide, there is no published literature on dinoflagellate cyst assemblages
in Saudi coastal areas of the Red Sea. However, incidents of algal blooms and dinoflagellate red tides did occur along Saudi coasts of the Red Sea during the period 2004–2006 (Mohamed & Messad 2007). Although these blooms have since disappeared from this area, there is a possibility of their recurrence in the original bloom area and elsewhere. Therefore, the collection and counting of resting cysts during non-bloom periods offer a potential tool for the prediction of future toxic blooms (Hallegraeff and Bolch, 1992, Anderson, 1997 and Persson et al., 2000). Hence, the
objective of this study was to investigate the occurrence of dinoflagellate cysts in surface sediments collected from previously infected areas with algal blooms on south-western Saudi coasts of the Red Sea. The germination ability of these cysts was also evaluated. The study area was located in the Red Sea off the south-western coast of Saudi Arabia, extending from 19.65° to 19.80°N (Figure 1). The coastal region of this area is subject to drainage from surrounding
rainwater pools and is affected by aquaculture wastewater discharges from a nearby shrimp farm. The surface sediments ABT199 collected from the study area were characterized as fine sand and mud (Table 1). Surface sediments were collected MTMR9 from 6 sites throughout the study area during March 2010. The sites are ca 20 km distant from each other. Three sediment samples were collected from different spots (located about 10 m away from one another) at each site with a flat spade and the subsamples put into plastic jars. Three replicate subsamples were taken from the top 5 cm using a 1.5-cm-diameter syringe with a cut-off top. The three replicates were pooled and placed into containers that were then tightly sealed to prevent germination. All the samples were stored in the dark at 4°C until processing. Aliquots of the samples were oven-dried at 105°C for 6 h to determine sediment dry weight. The sediments were analysed for grain size following Folk & Ward (1957), and their organic carbon content was determined according to el Wakeel & Riley (1957). The sediment samples from each site were homogenized with a glass rod, and subsamples of the sediment were extracted with a spoon and sieved through 100 μm and 25 μm Retsch stainless steel sieves using filtered seawater. The sediments remaining on the 25 μm sieve were collected in a 50 ml glass container.