Influence of environmental settings on the prevalence of Trichodesmium spp. in the Bay of Bengal

Abstract

Trichodesmium, an important marine nitrogen-fixing cyanobacteria, is widespread in tropical waters and contributes substantially to the global chemical cycles by new production. The interesting and intriguing feature of Trichodesmium blooms is the suddenness with which the blooms appear and disappear. A well-defined periodicity and annual rhythm of Trichodesmium blooms in the Indian south central coastal environments of the Arabian Sea between February and May is well documented. However, not much is known for the Bay of Bengal. Analysis of the surface water samples collected from the merchant vessels plying between Chennai and Singapore at regular intervals (February 2000 to September 2002 to study the variations in the micro-phytoplankton community indicated that Trichodesmium persists for a large part of the year in the south-eastern part of the Bay of Bengal. Remotely sensed images from 1997 to 2003 also indicated the prevalence of Trichodesmium in the south-eastern part of the Bay during the winter months and in the west (west Bay of Bengal and east Arabian Sea) during summer. This raises the possible role of physical forcing in the dispersal and seeding of Trichodesmium. The prevalence of stratified conditions in the Bay of Bengal almost throughout the year can be one of the causative factors facilitating the preponderance of Trichodesmium. The inter-annual variations observed indicate that the tracking of Trichodesmium will be useful in understanding the biogeochemistry of the region.KEY WORDS: Indian Ocean · Cyanobacteria · Phytoplankton · Arabian Sea · Remote sensing 356: 93-101, 2008 elements such as iron and phosphorous (Karl et al. 1992, Rueter et al. 1992, Mulholland et al. 2002. Resale or republication not permitted without written consent of the publisherMar Ecol Prog SerIn the Indian Ocean Trichodesmium blooms have been recorded since 1942 (Devassy et al. 1978 and references therein). The first report of the blooms in the Arabian Sea was in 1972 (Ramamurthy et al. 1972), and their occurrence with a well-defined periodicity and annual rhythm between February and May has been described as a phenomenon (Devassy et al. 1978). The regular timing of the blooms suggests that physical factors such as stratification, winds and current patterns influence these blooms. In the Bay of Bengal, blooms have been observed since 1942 (Ramamurthy et al. 1972, Devassy et al. 1978 and references therein, Gomes et al. 2000, Jyothibabu et al. 2003. However, elucidation of spatial and temporal distribution was not attempted in any of the earlier investigations. In the present study, which is the first of its kind, surface samples were collected at regular intervals for a period of 3 yr. It was found that Trichodesmium spp. appear regularly during the fall and winter in the Bay of Bengal and make their presence felt during the summer months along the south west coast of India.Remote sensing techniques provide an alternative solution for mapping Trichodesmium on a global scale. Algorithms to detect Trichodes...

Moderate Resolution Imaging Spectroradiometer (MODIS) observations of cyanobacteria blooms in Taihu Lake, China

“…Cyanobacteria and other phytoplankton blooms have been reported in many coastal waters and marginal seas, such as in the Gulf of Finland and the Baltic Sea [ Bianchi et al , 2000; Hansson and Hakansson , 2007], Lake Erie [ Vincent et al , 2004], the Bay of Bengal [ Hegde et al , 2008], and Moreton Bay, Australia [ Roelfsema et al , 2006]. The West Florida Shelf in the eastern Gulf of Mexico is also known to experience periodic occurrence of cyanobacteria ( Trichodesmium spp . )…”

Primary productivity and nitrogen fixation by Trichodesmium spp. in the Arabian Sea

“…It forms dense blooms which are studied with the purpose of understanding both its biomass as well as its distribution (Capone et al, 1997;Carpenter and Price, 1977). Since 1950, these blooms have been reported in the Arabian Sea (Basu et al, 2011;Capone et al, 1998;Desa et al, 2005;Devassy et al, 1978;Lugomela et al, 2002;Parab et al, 2006;Ramamurthy et al, 1972;Sawant and Madhupratap, 1996), the Lakshadweep Sea (Qasim, 1970), the Andaman Sea (Jyothibabu et al, 2003) and the Bay of Bengal (Hegde et al, 2008;Jyothibabu et al, 2003). The phytoplankton biomass at times exceeds 100 μgL −1 during the blooming period this value is higher than any other biomass value recorded in any other individual species (Parab et al, 2006).…”

Three decades of ocean-color remote-sensing Trichodesmium spp. in the World’s oceans: A review

“…In addition, the study successfully validated the algorithm using SeaWiFS match-up scenes containing in situ observations of Trichodesmium. Furthermore, Hedge et al (2008) found the algorithm did not yield false-positive retrievals for pixels that were known not to contain Trichodesmium.…”

“…Although, this study did not focus on algorithm development, it demonstrated how a suitable Trichodesmium remote-sensing algorithm could be applied in a useful way. The work of Hedge et al (2008) successfully determined a month-by-month climatology of the spatial distribution of Trichodesmium which was then linked with information regarding SST, nutrient regime and ocean currents. In addition, the study successfully validated the algorithm using SeaWiFS match-up scenes containing in situ observations of Trichodesmium.…”

“…The algorithm was ultimately incorporated as a quality control flag to indicate if a Level-2 (L2) ocean-color product was potentially contaminated by the presence of Trichodesmium (Hedge et al, 2008). Hedge et al (2008) used the SeaDAS Trichodesmium flag to study the occurrence of Trichodesmium in the Bay of Bengal using SeaWiFS imagery from 1997 to 2003. Although, this study did not focus on algorithm development, it demonstrated how a suitable Trichodesmium remote-sensing algorithm could be applied in a useful way.…”