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Phytoplankton dynamics associated with the monsoon in the Sulu Sea as revealed by pigment signature 总被引：2，自引：0，他引：2
Phytoplankton dynamics during the northeast monsoon was investigated in the Sulu Sea from algal pigment analysis. We visited
the Sulu Sea in February 2000, a mid period of the northeast monsoon, and in November and December 2002, the beginning of
the northeast monsoon. SeaWiFS images showed generally low concentrations of surface chlorophyll a (Chl a) during the southwest monsoon and higher concentrations with several peaks during the northeast monsoon. In the beginning
of the northeast monsoon, subsurface chlorophyll maxima (SCM) occurred, where vertical variation in class-specific composition
as estimated from pigment signatures was prominent. Prochlorococcus, cyanobacteria, prymnesiophytes and crysophytes were important groups above the SCM, and the contribution of cyanobacteria
to Chl a became much lower at and below the SCM. Contributions of chlorophytes and prasinophytes to Chl a generally showed maxima near the SCM. This distribution was accompanied by vertical changes in the concentration of photoprotective
pigments relative to photosynthetic accessory pigments. During the mid northeast monsoon, the upward supply of nutrients was
probably enhanced at some stations due to vertical mixing, and as a consequence diatoms dominated in the upper 100 m water
column of these stations, and other eukaryotic flagellates including prymnesiophytes, chrysophytes and cryptophytes were secondary
major components of the community. The elevation of Chl a concentration and changes in phytoplankton community during the northeast monsoon likely influence the variation in biological
production at higher trophic levels in the Sulu Sea. 相似文献
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N. Ramaiah V. V. S. S. Sarma Mangesh Gauns M. Dileep Kumar M. Madhupratap 《Journal of Earth System Science》2000,109(4):443-451
Bacterial abundance and production, numbers, sizes and concentrations of transparent exopolymer particles (TEP) and total
organic carbon (TOC) were measured during the 1996 summer monsoon to understand the relationship between TEP, the most labile
particulate organic carbon, and bacteria. While high regional variability in the vertical distribution of TOC was discernible,
TEP concentrations were high in surface waters at 18–20°N along 64°E with concentrations well over 25 mg alginic acid equivalents
I−1 due to upwelling induced productivity. Their concentrations decreased with depth and were lower between 200 and 500 m. Bacterial
concentrations were up to 1.99 × 108 I–1 in the surface waters and decreased by an order of magnitude or more at depths below 500 m. A better relationship has been
found between bacterial abundance and concentrations of TEP than between bacteria and TOC, indicating that bacterial metabolism
is fueled by availability of TEP in the Arabian Sea. Assuming a carbon assimilation of 33%, bacterial carbon demand (BCD)
is estimated to be 1.017 to 4.035 g C m–2 d–1 in the surface waters. The observed TEP concentrations appear to be sufficient in meeting the surface and subsurface BCD
in the northern Arabian Sea. 相似文献
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The seasonal dynamics of nutrient ratios and abundance of phytoplankton cells from the central (CB) and western (WB) Bay of Bengal (BOB) were studied during the fall intermonsoon (FIM; September-October 2002) and spring intermonsoon (SpIM; April-May 2003). The nutrient molar ratios of macronutrients such as nitrate to phosphate (N:P), nitrate to silicate (N:Si) and silicate to phosphate (Si:P) in the top 120m were calculated for both FIM and SpIM. During both the seasons, the N:P ratios along the CB and WB were lower than 16, indicating nitrate deficiency. Whereas, along both transects the N:Si ratio was <1 and Si:P >3 in the top 20 and 40m during FIM and SpIM, respectively, indicating Si enrichment. Relatively greater nutrient concentrations along the WB than the CB appear to contribute to higher phytoplankton abundance. The preponderance of diatoms in the Bay could be attributed to rapid utilization of available nutrients in particular during FIM thus resulting in low N:Si ratios in the water column. Among diatoms, pennales were predominantly controlled by nutrients and their ratios. While, apart from nutrients, physical stratification, light and eddies also seem to influence the distribution and abundance of centrales. 相似文献
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Naga Mangala SudheepKandikere Ramaiah Sridhar 《Limnologica》2012,42(2):87-94
The hyporheic zones constitute a major site of storage of organic matter and energy flow in freshwater ecosystems. To complement the studies carried out in North America and Europe, we evaluated the sediment quality and occurrence of aquatic hyphomycetes in coarse particulate organic matter (CPOM; ≥5 mm) and fine particulate matter (FPM; ≤1 mm) in three locations of Kaiga stream and eight locations of Kadra dam of the River Kali in Western Ghats. The pH of sediments of stream and dam was acidic (5.8-6.6) and the average organic carbon of stream sediments was higher than dam sediments (8.6% vs. 3.9%). Among the eight minerals monitored, Fe was highest in all sediments and Ni was below detectable limit in four dam sediments. Spores of aquatic hyphomycetes were directly released from the CPOM fractions of sediments upon bubble chamber incubation, while the FPM fractions produced spores indirectly by colonization of sterile leaf baits followed by bubble chamber incubation. The species richness and diversity in CPOM was higher than FPM in stream as well as dam sediments. The Sorensen's similarity indices between the fungal flora of CPOM in stream (66.7-81.8%) and dam (69.2-88%) locations were generally higher than FPM. The spore output per mg CPOM was between 1215 (dam) and 3384 (stream). The species richness was negatively correlated with Cr (P < 0.01; r = −1.000) of stream sediments, while it was negatively correlated with organic carbon (P < 0.05; r = −0.740) and positively correlated with K (P < 0.05; r = 0.750) of dam sediments. Occurrence and survival of aquatic hyphomycetes in hyporheic habitats of freshwater bodies indicate the importance of such zones as reservoir of fungal inoculum necessary in fundamental functions such as organic matter processing and energy flow. The present study provides baseline data on the sediment quality and fungal composition of stream and dam locations of River Kali of Kaiga region, which will develop as center of industrial activities in future. 相似文献
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Effect of iron enrichment on the dynamics of transparent exopolymer particles in the western subarctic Pacific 总被引：1，自引：0，他引：1
Neelam Ramaiah Shigenobu Takeda Ken Furuya Takeshi Yoshimura Jun Nishioka Tatsuo Aono Yukihiro Nojiri Keiri Imai Isao Kudo Hiroaki Saito Atsushi Tsuda 《Progress in Oceanography》2005,64(2-4):253
Dynamics of transparent exopolymer particles (TEP) was studied during the first in situ iron-enrichment experiment conducted in the western subarctic Pacific in July–August 2001, with the goal of evaluating the contribution of TEP to vertical flux as a result of increased primary production following iron enrichment in open ocean ecosystems. Subsequent to the enhancement of phytoplankton production, we observed increase in TEP concentration in the surface layer and sedimentation of organic matter beneath it. Vertical profiles of TEP, chlorophyll a (Chl a) and particulate organic carbon (POC) were obtained from six depths between 5 and 70 m, from a station each located inside and outside the enriched patch. TEP and total mass flux were estimated from the floating sediment traps deployed at 200 m depth. Chl a and TEP concentrations outside the patch varied from 0.2 to 1.9 μg L−1 and 40–60 μg XG equiv. L−1, respectively. Inside the patch, Chl a increased drastically from day 7 reaching the peak of 19.2 μg L−1 on day 13, which coincided with the TEP peak of 189 μg XG equiv. L−1. TEP flux in the sediment trap increased from 41 to 88 mg XG equiv. m−2 d−1, with 8–14% contribution of TEP to total mass flux. This forms the basic data set on ambient concentrations of TEP in the western subarctic Pacific, and evaluation of the effect of iron enrichment on TEP. 相似文献
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Data on the distribution of dimethylsulphide (DMS) and dimethylsulphoniopropionate (DMSP) in relation to phytoplankton abundance in different oceanic environments is important to understand the biogeochemistry of DMS, which plays an important role in the radiation balance of the earth. During the summer monsoon of 2001 measurements were made for DMS and DMSPt (total DMSP) together with related biological parameters in the Bay of Bengal. Both DMS and DMSPt were restricted to the upper 40 m of the water column. Diatoms accounted for more than 95% of the phytoplankton and were the major contributors to the DMS and DMSPt pool. The mean concentration of DMS in the upper 40 m was observed to be around 1.8+/-1.9 nM in the study area, while DMSPt concentrations varied between 0.7 nM and 40.2 nM with a mean of 10.4+/-8.2 nM. The observed lower DMSPt in the northern Bay in spite of higher mean primary productivity, chlorophyll a and phytoplankton cell counts seemed to result from grazing. Though salinity divides the Bay into different biogeochemical provinces there is no relation between salinity and DMS or DMSPt. On the other hand DMS was linearly related to chlorophyll a:phaeopigments ratio. The results suggest the need for deeper insight into the role of diatoms in the biogeochemical cycling of DMS. 相似文献
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