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Occurrence and germination of dinoflagellate cysts in surface sediments from the Red Sea off the coasts of Saudi Arabia

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Mohamed Z. A., Al-Shehri A. M.

Oceanologia

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2011

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tom 53

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nr 1

The distribution and abundance of dinoflagellate cyst assemblages were investigated in surface sediments from south-western Red sea coasts of Saudi Arabia at six sites during March 2010. A total of 19 taxa of dinoflagellate cysts were identified from all sites. The sampling sites showed a similar cyst assemblage, but they differed in total cyst abundance (3 to 4083 cysts g−1 dry weight). Cyst abundance was strongly correlated with sediment characteristics, the highest numbers being recorded in sediments with large contents of organic carbon, silt and clay. Cyst assemblages were dominated by cysts of potentially toxic species, including Cochlodinium polykrikos, Prorocentrum minimum, Dinophysis acuminata, Alexandrium catenella and Scrippsiella trochoidea. Most cysts germinated successfully at different rates at 15 and 25◦C. This study suggests that surface sediments from all Saudi Red Sea coasts should be monitored for the presence of dinoflagellate cysts to give ample warning of the presence and abundance of toxic species in a given area.

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The link between shrimp farm runoff and blooms of toxic Heterosigma akashiwo in Red Sea coastal waters

100%

Mohamed Z. A., Al-Shehri A. M.

Oceanologia

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2012

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tom 54

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nr 2

In May 2010 a copious bloom of the raphidophyte Heterosigma akashiwo was observed for the first time in Red Sea waters off the coasts of Saudi Arabia. This bloom was confined to an area where water and phytoplankton flow freely between the sea and a shrimp farm. The phytoplankton density and physico-chemical characteristics of the sea water were therefore investigated weekly at bloom and non-bloom sites in order to gain insight into the environmental factors prevailing at the bloom site and their link with the shrimp farm runoff. The bloom site showed higher nutrient concentrations than the non-bloom site, indicating the possible role of the shrimp farm in flushing nutrients into this site. The bloom appeared on 27 May, coinciding with a decrease in salinity (<300/00) and an increase in temperature (>19◦C). The results of toxicological assays showed that both bloom samples and batch cultures of H. akashiwo were toxic to Artemia salina and exhibited haemolytic activity with respect to rabbit erythrocytes. Bloom samples showed a higher toxicity (LC50 = 8.9 × 104 cells ml−1) and haemolytic activity (EC50 = 3.64 × 104 cells ml−1) than the batch cultures (LC50 =11.6×104 cells ml−1, EC50 =5.1×104 cells ml−1). In the light of the results of this study, the link between H. akashiwo blooms and shrimp farm runoff should be considered during the monitoring of Red Sea coastal waters for the presence of harmful algal blooms.

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Mass occurrence and toxicity of the cyanobacterium Lyngbya majuscula under phosphorus-limited conditionsin the Red Sea

100%

Al-Shehri A. M., Mohamed Z. A.

International Journal of Ecohydrology and Hydrobiology

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2007

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tom 07

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nr 1

51-57

Ograniczanie wyników

2 Oceanologia

1 International Journal of Ecohydrology and Hydrobiology

3 Al-Shehri A. M.

3 Mohamed Z. A.

1 2012

1 2011

1 2007

Occurrence and germination of dinoflagellate cysts in surface sediments from the Red Sea off the coasts of Saudi Arabia

The link between shrimp farm runoff and blooms of toxic Heterosigma akashiwo in Red Sea coastal waters

Mass occurrence and toxicity of the cyanobacterium Lyngbya majuscula under phosphorus-limited conditionsin the Red Sea