Blooms of Trichodesmium erythraeum in the South Eastern Arabian Sea during the onset of 2009 summer monsoon

Abstract

This study presents in situ evidence for the blooms of Trichodesmium erythraeum observed in the shelf waters of the South Eastern Arabian Sea (SEAS) during the onset of the southwest monsoon in June 2009. Evidence showed that water surface discoloration was caused by the accumulation of T. erythraeum, and that the water column contained a colony of T. thiebautii. The surface water color in the bloom region varied from pale brown to pinkish red. Pale brown indicated healthy algae at the peak of its photosynthetic activity, while pinkish red indicated the presence of photosynthetically less active filaments. Zooplankton abundance, especially copepodites, in the bloom area substantiated the theory that Trichodesmium filaments are excellent epiphytes to which the copepodites cling. The bloom area was very fertile with copious quantities of dissolved oxygen (6.85 ml L -1 ), PO 4 -P (0.108 µmol L -1 ) and SiO 4 (1.29 µmol L -1 ). Lower NO 3 -N (0.028 µmol L -1) values in the bloom area did not appear to affect Trichodesmium growth from molecular nitrogen fixation. However, lower NO 3 -N values altered the normal phytoplankton composition of this area.

Variability of chlorophyll associated with El Niño–Southern Oscillation and its possible biological feedback in the equatorial Pacific

“…Most of the aforementioned studies were performed since satellite‐based ocean color data became available. Although data from moorings or oceanographic cruises have been of use [ Jang et al , 2010; Padmakumar et al , 2010], these are so spatially and temporally limited that data sets with global coverage are of much greater utility for exploring variability in phytoplankton productivity. The Coastal Zone Color Scanner (CZCS), operated from 1978 to 1986 [ Madrid , 1978]; the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS), from 1997 [ McClain et al , 1998]; and the Moderate Resolution Imaging Spectroradiometer (MODIS) from 2002 [ Esaias et al , 1998] are ocean color instruments that measure water‐leaving radiance.…”

An optical system for detecting and describing major algal blooms in coastal and oceanic waters around India

“…Nevertheless, the present approach was successful in detecting Trichodesmium blooms from MODIS‐Aqua images in coastal waters of the Arabian Sea and southern Bay of Bengal. As evident in Figures and , curvilinear and filamentous features of the Trichodesmium bloom detected along the southwest coast of India are not surprising as they have been recorded in surface and subsurface waters (60 m) and reported by many field studies [e.g., Padmakumar et al ., ; Krishnan et al ., 2007]. Interestingly, on 19 February 2008, T. erythraeum blooms were seen in association with N. scintillans bloom and active filaments of Trichodesmium bloom occurred parallel to the coast from Gujarat (north) to Mangalore (south).…”

“…Samples collected from Trichodesmium filaments were characterized by cell density of 1.14 × 10 6 L −1 , 1.968 × 10 6 L −1 , and 1.51 × 10 6 L −1 at bloom sites off Kollam, Kochi and Kannur. These locations were sufficiently fertile with quantities of dissolved oxygen (6.85 mL L −1 ), PO 4 ‐P (0.108 μmol L −1 ) and SiO 4 (1.29 μmol L −1 ) and SST and salinity of 28.7°C and 35.13 psu, 29.48°C and 35.17 psu and 29.03°C and 35.47 psu, respectively [ Padmakumar et al ., ]. Westerly and northwesterly winds of 5 m s −1 and southward coastal currents provided favorable conditions for the aggregation and accumulation of Trichodesmium blooms along the southwest coast.…”

“…Westerly and northwesterly winds of 5 m s −1 and southward coastal currents provided favorable conditions for the aggregation and accumulation of Trichodesmium blooms along the southwest coast. Although Trichodesmium bloom occurrence coincided with the onset of the southwest monsoon is uncommon, studies based on shipboard hydrographic and biological data in conjugation with satellite data found that narrow and filamentous features of Trichodesmium were closely associated with increasing water temperatures and seasonal stratification along the southwest coast of India [ Gomes et al ., ; Padmakumar et al ., ].…”

“…[] reported many of these data for N. scintillans blooms on 24 January 2006. The cruise program conducted on 4 June 2009 documented the Trichodesmium blooms at a location 09°56.183 N and 75°54.948 E off Kochi (southern part of Arabian Sea) [ Padmakumar et al ., ]. Several data including optical, physical oceanographic, and ancillary data were collected to elucidate the bloom evolution and dynamics.…”