This study was carried out to investigate the Cochlodinium polykrikoides fluctuations in the north of Oman Sea during pre- and post-monsoon season in 2008. The study area was divided into 10 transects （TI-T10） from ...This study was carried out to investigate the Cochlodinium polykrikoides fluctuations in the north of Oman Sea during pre- and post-monsoon season in 2008. The study area was divided into 10 transects （TI-T10） from the Strait of Hormuz （T1） to Gwadar （TI0） which cover the whole of the Iranian waters in the Oman Sea. The results showed that at first, Cochlodinium polykrikoides appeared in the northeast part （T10） in the pre-monsoon season, then it spread to other parts of the study area. Cochlodinium polykrikoides was observed in greater abundance in the Strait of Hormuz in the post-monsoon season. The results demonstrated that T10 （transect 10） had the highest abundance in the pre-monsoon season. The Kruskal-Wallis test showed a significant difference among transects （P 〈 0.05）. The present study showed that the abundance of Cochlodinium polykrikoides increased from coastal to offshore waters in the pre-monsoon season; however, in the post-monsoon season, there was a higher abundance in coastal waters compared to the offshore zone. It could be seen that the abundance of Cochlodinium polykrikoides started in offshore waters, then increased in coastal waters. During the pre-monsoon season, water discoloration was not observed, however, the water changed to brown from T 1 to T4 （northwest） and blooms of Cochlodinium polykrikoides was recorded in the post-monsoon season.展开更多
Numerical simulations of four weak cyclonic storms [two cases of pre-monsoon cyclones: Laila (2010), Aila (2009) and two cases of post-monsoon cyclones: Jal (2010), SCS (2003)] are carried out using WRF-ARW mesoscale ...Numerical simulations of four weak cyclonic storms [two cases of pre-monsoon cyclones: Laila (2010), Aila (2009) and two cases of post-monsoon cyclones: Jal (2010), SCS (2003)] are carried out using WRF-ARW mesoscale model. Betts-Miller-Janjic (BMJ) as cumulus parameterization (CP) scheme, Yonsei University(YSU) planetary boundary layer (PBL) scheme and WRF single moment 6 class (WSM6) microphysics (MP) scheme is kept same for all the cyclone cases. Three two-way interactive nested domains [60 km,20 kmand6.6 km] are used with initial and boundary conditions from NCEP Final Analysis data. The model integration is performed to evaluate the track, landfall time and position as well as intensity in terms of Central Sea Level Pressure (CSLP) and Maximum Surface Wind speed (MSW) of the storm. The track and landfall (time and position) of almost all cyclones are well predicted by the model (except for SCS cyclone case) which may be because of the accurate presentation of the steering flow by CP scheme. Irrespective of season, the intensity is overestimated in all the cases of cyclone, mainly because of the lower tropospheric and mid-tropospheric parameters are overestimated. YSU PBL scheme used here is responsible for the deep convection in and above PBL. Concentration of frozen hydrometeors at the mid-tropospheric levels and thus the latent heat released during auto conversion of hydrometeors is also responsible for overestimation of intensity.展开更多
Introduction:Seasonal and tidal variations in nutrient concentration and water quality were investigated in the western Sundarbans of Bangladesh during the post-monsoon,winter and monsoon seasons during 2010–2011.Met...Introduction:Seasonal and tidal variations in nutrient concentration and water quality were investigated in the western Sundarbans of Bangladesh during the post-monsoon,winter and monsoon seasons during 2010–2011.Methods:Water collected from the surface,middle and bottom layers at six locations of the Kholpetua-Arpangashia river system during high and low tides was analyzed for temperature,salinity,pH,dissolved oxygen(DO),total dissolved solids(TDS),electrical conductivity(EC)and dissolved nutrients(NO3–N,PO4–P,SO4 and NH3–N).Results:The study revealed that nutrient concentrations were influenced by seasonal changes.Mean nutrient levels during post-monsoon,winter and monsoon seasons,respectively,were in the following ranges:nitrate(0.06–0.40,0.06–0.46 and 0.08–0.46 mg/L);phosphate(0.09–0.18,0.05–0.42 and 0.10–0.16 mg/L);sulphate(58.71–86.14,68.68–119.01 and 78.15–136.47 mg/L)and ammonia(0.02–0.08,0.02–0.04 and 0.26–0.38 mg/L).Increased levels of PO4–P,SO4 and NH3–N and lower DO and salinity were recorded during the monsoon period.Most of the experimental sites showed higher NO3–N content during monsoon,whereas few elevated concentrations were observed during post-monsoon and winter periods.High and low tidal waters contained mean nutrient levels in the following ranges:nitrate(0.05–0.46 and 0.04–0.40 mg/L);phosphate(0.05–0.42 and 0.07–0.18 mg/L);sulphate(63.63–125.36 and 58.71–136.47 mg/L)and ammonia(0.02–0.38 and 0.02–0.37 mg/L)without following any distinct fluctuation patterns.The western part of the Sundarbans receives less freshwater input during the monsoon season than other areas of the ecosystem,which reduces the variability of nutrient levels and water quality components.Conclusions:This study provides considerable advances in understanding the seasonality of nutrient distribution with possible tidal influence.The data generated from this study will guide continuing efforts to support a sound management for coastal mangrove ecosystems.展开更多
文摘This study was carried out to investigate the Cochlodinium polykrikoides fluctuations in the north of Oman Sea during pre- and post-monsoon season in 2008. The study area was divided into 10 transects （TI-T10） from the Strait of Hormuz （T1） to Gwadar （TI0） which cover the whole of the Iranian waters in the Oman Sea. The results showed that at first, Cochlodinium polykrikoides appeared in the northeast part （T10） in the pre-monsoon season, then it spread to other parts of the study area. Cochlodinium polykrikoides was observed in greater abundance in the Strait of Hormuz in the post-monsoon season. The results demonstrated that T10 （transect 10） had the highest abundance in the pre-monsoon season. The Kruskal-Wallis test showed a significant difference among transects （P 〈 0.05）. The present study showed that the abundance of Cochlodinium polykrikoides increased from coastal to offshore waters in the pre-monsoon season; however, in the post-monsoon season, there was a higher abundance in coastal waters compared to the offshore zone. It could be seen that the abundance of Cochlodinium polykrikoides started in offshore waters, then increased in coastal waters. During the pre-monsoon season, water discoloration was not observed, however, the water changed to brown from T 1 to T4 （northwest） and blooms of Cochlodinium polykrikoides was recorded in the post-monsoon season.
文摘Numerical simulations of four weak cyclonic storms [two cases of pre-monsoon cyclones: Laila (2010), Aila (2009) and two cases of post-monsoon cyclones: Jal (2010), SCS (2003)] are carried out using WRF-ARW mesoscale model. Betts-Miller-Janjic (BMJ) as cumulus parameterization (CP) scheme, Yonsei University(YSU) planetary boundary layer (PBL) scheme and WRF single moment 6 class (WSM6) microphysics (MP) scheme is kept same for all the cyclone cases. Three two-way interactive nested domains [60 km,20 kmand6.6 km] are used with initial and boundary conditions from NCEP Final Analysis data. The model integration is performed to evaluate the track, landfall time and position as well as intensity in terms of Central Sea Level Pressure (CSLP) and Maximum Surface Wind speed (MSW) of the storm. The track and landfall (time and position) of almost all cyclones are well predicted by the model (except for SCS cyclone case) which may be because of the accurate presentation of the steering flow by CP scheme. Irrespective of season, the intensity is overestimated in all the cases of cyclone, mainly because of the lower tropospheric and mid-tropospheric parameters are overestimated. YSU PBL scheme used here is responsible for the deep convection in and above PBL. Concentration of frozen hydrometeors at the mid-tropospheric levels and thus the latent heat released during auto conversion of hydrometeors is also responsible for overestimation of intensity.
基金Ministry of Education,Government of the Peoples’Republic of Bangladesh provided the necessary financial support under the Grants for Advanced Research in Science to carry out the present study.The authors would like to acknowledge the support of the laboratory staff of the Fisheries and Marine Resource Technology Discipline and Environmental Science Discipline of Khulna University during sample analysis in the laboratory.Thanks are due to the graduate and undergraduate students for their generous cooperation during field observation,in-situ measurement and laboratory analysis.Support of the authorities of the Forest Department of Bangladesh are appreciated.The authors would like to thank two anonymous reviewers for their valuable comments and suggestions that helped improve the manuscript.
文摘Introduction:Seasonal and tidal variations in nutrient concentration and water quality were investigated in the western Sundarbans of Bangladesh during the post-monsoon,winter and monsoon seasons during 2010–2011.Methods:Water collected from the surface,middle and bottom layers at six locations of the Kholpetua-Arpangashia river system during high and low tides was analyzed for temperature,salinity,pH,dissolved oxygen(DO),total dissolved solids(TDS),electrical conductivity(EC)and dissolved nutrients(NO3–N,PO4–P,SO4 and NH3–N).Results:The study revealed that nutrient concentrations were influenced by seasonal changes.Mean nutrient levels during post-monsoon,winter and monsoon seasons,respectively,were in the following ranges:nitrate(0.06–0.40,0.06–0.46 and 0.08–0.46 mg/L);phosphate(0.09–0.18,0.05–0.42 and 0.10–0.16 mg/L);sulphate(58.71–86.14,68.68–119.01 and 78.15–136.47 mg/L)and ammonia(0.02–0.08,0.02–0.04 and 0.26–0.38 mg/L).Increased levels of PO4–P,SO4 and NH3–N and lower DO and salinity were recorded during the monsoon period.Most of the experimental sites showed higher NO3–N content during monsoon,whereas few elevated concentrations were observed during post-monsoon and winter periods.High and low tidal waters contained mean nutrient levels in the following ranges:nitrate(0.05–0.46 and 0.04–0.40 mg/L);phosphate(0.05–0.42 and 0.07–0.18 mg/L);sulphate(63.63–125.36 and 58.71–136.47 mg/L)and ammonia(0.02–0.38 and 0.02–0.37 mg/L)without following any distinct fluctuation patterns.The western part of the Sundarbans receives less freshwater input during the monsoon season than other areas of the ecosystem,which reduces the variability of nutrient levels and water quality components.Conclusions:This study provides considerable advances in understanding the seasonality of nutrient distribution with possible tidal influence.The data generated from this study will guide continuing efforts to support a sound management for coastal mangrove ecosystems.
