Kinkade,C.S.,Marra,J.,Dickey,T.D.,Weller,R.
An annual cycle of phytoplankton biomass in the Arabian Sea, 1994-1995, as determined by moored optical sensors Journal Article
In: Deep-Sea Research Part II, vol. 48, no. 137, pp. 1285-1301, 2001.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, depth
@article{,
title = {An annual cycle of phytoplankton biomass in the Arabian Sea, 1994-1995, as determined by moored optical sensors},
author = {Kinkade,C.S.,Marra,J.,Dickey,T.D.,Weller,R.},
year = {2001},
date = {2001-01-01},
journal = {Deep-Sea Research Part II},
volume = {48},
number = {137},
pages = {1285-1301},
abstract = {A surface-to-bottom mooring in the central Arabian Sea (15.5§N, 61.5§E) deployed from October 1994 to October 1995, included fluorometers, PAR irradiance sensors, Lu683 sensors, and a spectral radiometer. An annual cycle of phytoplankton biomass was determined by transforming signals from the optical sensors into chlorophyll a (chl a). Half-yearly phytoplankton blooms with water-column stratification were observed near the end of each monsoon, as well as biomass increases in response to mesoscale #ow features. During the Northeast Monsoon, the integrate water-column chl a rose from 15 to 25mg m-2, while during the Southwest Monsoon, chl a increased from 15 to a maximum >40mg m-2. We present an empirical relationship between the ratio of downwelling Ed443/Ed550 (blue to green wavelength ratio) and integral euphotic zone chl a determined by moored fluorometers (r2 = 0.73). There is a more significant relationship between Ed443/Ed550 measured at one depth in the water column (65 m) and the average vertical attenuation cofficient for PAR (KPAR) between 0 and 65m (r2 = 0.845). Because biofouling was a significant problem at times, data return from any one sensor was incomplete. However, optical sensor/data intercomparison helped fill gaps while permitting investigation of the temporal variability in observed phytoplankton biomass. },
keywords = {Arabian Sea, chlorophyll, depth},
pubstate = {published},
tppubtype = {article}
}
A surface-to-bottom mooring in the central Arabian Sea (15.5§N, 61.5§E) deployed from October 1994 to October 1995, included fluorometers, PAR irradiance sensors, Lu683 sensors, and a spectral radiometer. An annual cycle of phytoplankton biomass was determined by transforming signals from the optical sensors into chlorophyll a (chl a). Half-yearly phytoplankton blooms with water-column stratification were observed near the end of each monsoon, as well as biomass increases in response to mesoscale #ow features. During the Northeast Monsoon, the integrate water-column chl a rose from 15 to 25mg m-2, while during the Southwest Monsoon, chl a increased from 15 to a maximum >40mg m-2. We present an empirical relationship between the ratio of downwelling Ed443/Ed550 (blue to green wavelength ratio) and integral euphotic zone chl a determined by moored fluorometers (r2 = 0.73). There is a more significant relationship between Ed443/Ed550 measured at one depth in the water column (65 m) and the average vertical attenuation cofficient for PAR (KPAR) between 0 and 65m (r2 = 0.845). Because biofouling was a significant problem at times, data return from any one sensor was incomplete. However, optical sensor/data intercomparison helped fill gaps while permitting investigation of the temporal variability in observed phytoplankton biomass.
Kumar,S.P.,Ramaiah,N.,Gauns,M.,Sarma,V.V.S.S.,Muraleedharan,P.M.,Raghukumar,S.,Kumar,M.D.,Madhupratap,M.
Physical forcing of biological productivity in the Northern Arabian Sea during the Northeast Monsoon Journal Article
In: Deep-Sea Research Part II, vol. 48 , no. 139, pp. 1115-1126, 2001.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, depth, feeding, lead, location, productivity, spatial scale, surface temperature, temperature
@article{,
title = {Physical forcing of biological productivity in the Northern Arabian Sea during the Northeast Monsoon},
author = {Kumar,S.P.,Ramaiah,N.,Gauns,M.,Sarma,V.V.S.S.,Muraleedharan,P.M.,Raghukumar,S.,Kumar,M.D.,Madhupratap,M.},
year = {2001},
date = {2001-01-01},
journal = {Deep-Sea Research Part II},
volume = {48 },
number = {139},
pages = {1115-1126},
abstract = {Time-series observations at a nominally fixed location in the northern Arabian Sea (21§N, 64§E) during the Northeast Monsoon (winter, February) of l997 showed the prevalence of cold sea-surface temperatures (SST) and deep mixed layers resulting from winter cooling and convection. The covariation of nitrate concentrations in the surface layers and concentrations of chlorophyll a and primary production in the euphotic zone with mixed-layer depth (MLD) and wind suggests that carbon fixation was controlled primarily by physical forcing. Cooler waters during winter 1997 relative to winter 1995 were associated with deeper MLDs, higher nitrate concentrations, elevated primary productivity, and higher chlorophyll a concentrations, leading to the inference that even a 1§C decrease in SST could lead to significantly higher primary productivity. Satellite data on sea surface temperature (advanced very high-resolution radiometer; AVHRR) and TOPEX/POSEl- DON altimeter data suggest that this interannual variation is of basin-wide spatial scale. After the termination of winter cooling and subsequent warming during the Spring Intermonsoon, the Arabian Sea has low primary production. During the latter period, micro-organisms, i.e. heterotrophic bacteria and microzooplankton)-proliferate, a feeding mode through the microbial loop that appears to be inherent to mesozooplankton for sustaining their biomass throughout the year in this region.},
keywords = {Arabian Sea, chlorophyll, depth, feeding, lead, location, productivity, spatial scale, surface temperature, temperature},
pubstate = {published},
tppubtype = {article}
}
Time-series observations at a nominally fixed location in the northern Arabian Sea (21§N, 64§E) during the Northeast Monsoon (winter, February) of l997 showed the prevalence of cold sea-surface temperatures (SST) and deep mixed layers resulting from winter cooling and convection. The covariation of nitrate concentrations in the surface layers and concentrations of chlorophyll a and primary production in the euphotic zone with mixed-layer depth (MLD) and wind suggests that carbon fixation was controlled primarily by physical forcing. Cooler waters during winter 1997 relative to winter 1995 were associated with deeper MLDs, higher nitrate concentrations, elevated primary productivity, and higher chlorophyll a concentrations, leading to the inference that even a 1§C decrease in SST could lead to significantly higher primary productivity. Satellite data on sea surface temperature (advanced very high-resolution radiometer; AVHRR) and TOPEX/POSEl- DON altimeter data suggest that this interannual variation is of basin-wide spatial scale. After the termination of winter cooling and subsequent warming during the Spring Intermonsoon, the Arabian Sea has low primary production. During the latter period, micro-organisms, i.e. heterotrophic bacteria and microzooplankton)-proliferate, a feeding mode through the microbial loop that appears to be inherent to mesozooplankton for sustaining their biomass throughout the year in this region.
Banse,K.,English,D.C.
Geographical differences in seasonality of CZCS-derived phytoplankton pigment in the Arabian Sea for 1978-1986 Journal Article
In: Deep-Sea Research Part II, vol. 47, no. 322, pp. 1623-1677, 2000.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, depth, Gulf of Oman, lead, Oman, plankton, productivity, timing, trap, Upwelling
@article{,
title = {Geographical differences in seasonality of CZCS-derived phytoplankton pigment in the Arabian Sea for 1978-1986},
author = {Banse,K.,English,D.C.},
year = {2000},
date = {2000-01-01},
journal = {Deep-Sea Research Part II},
volume = {47},
number = {322},
pages = {1623-1677},
abstract = {In situ measurements of phytoplankton chlorophyll in the Arabian Sea were taken largely along temporally and spatially unevenly distributed sections, scarce especially prior to the operation of NASA's Coastal Zone Color Scanner (CZCS). Herein, the CZCS pigment observations between late 1978 and mid-1986 north of 10§N, including the outer Gulf of Oman, are depicted for 14 subregions beyond the continental shelves as daily means, often only five days apart. To eliminate bias from electronic overshoot, the data were reprocessed with a more conservative cloud screen than used for NASA's Global Data Set. The pattern, derived from the older in situ observations, of one period with elevated chlorophyll almost everywhere during the Southwest Monsoon (SWM) and one additional late-winter bloom in the north, is confirmed. The differing nitrate silicate ratios in freshly entrained water in the central and northern Arabian Sea seem to lead to different succession and perhaps to differing vertical fluxes, and during winter favor blooms only in the north. The spatial pigment pattern in the outer Gulf of Oman is not an extension of that of the northwestern Arabian Sea. The seasonal physical forcing explains much of the timing of pigment concentration changes, but not the levels maintained over long periods. From the CZCS observations it is unclear whether the period of high phytoplankton productivity expected during the SWM in the open Arabian Sea lasts for about two or four months. During this entire season, chlorophyll values in the upper layers rarely exceed 1-2 mg m-3 outside the zone influenced by the Arabian upwelling. Near 15§N, however, fluxes into sediment traps at 3 km depth indicate an onset of high primary production very soon after the arrival of the SWM and suggest a long period of high production in the open sea. The partial temporal disconnect during the SWM between pigment changes in the upper part of the euphotic zone and of fluxes into the traps is disconcerting. For future modeling of plankton production in the open Arabian Sea, the use of two size classes of phytoplankton is recommended. The utility of satellite-derived pigment concentrations (as opposed to temporal changes of pigment) for testing such models is questioned.},
keywords = {Arabian Sea, chlorophyll, depth, Gulf of Oman, lead, Oman, plankton, productivity, timing, trap, Upwelling},
pubstate = {published},
tppubtype = {article}
}
In situ measurements of phytoplankton chlorophyll in the Arabian Sea were taken largely along temporally and spatially unevenly distributed sections, scarce especially prior to the operation of NASA's Coastal Zone Color Scanner (CZCS). Herein, the CZCS pigment observations between late 1978 and mid-1986 north of 10§N, including the outer Gulf of Oman, are depicted for 14 subregions beyond the continental shelves as daily means, often only five days apart. To eliminate bias from electronic overshoot, the data were reprocessed with a more conservative cloud screen than used for NASA's Global Data Set. The pattern, derived from the older in situ observations, of one period with elevated chlorophyll almost everywhere during the Southwest Monsoon (SWM) and one additional late-winter bloom in the north, is confirmed. The differing nitrate silicate ratios in freshly entrained water in the central and northern Arabian Sea seem to lead to different succession and perhaps to differing vertical fluxes, and during winter favor blooms only in the north. The spatial pigment pattern in the outer Gulf of Oman is not an extension of that of the northwestern Arabian Sea. The seasonal physical forcing explains much of the timing of pigment concentration changes, but not the levels maintained over long periods. From the CZCS observations it is unclear whether the period of high phytoplankton productivity expected during the SWM in the open Arabian Sea lasts for about two or four months. During this entire season, chlorophyll values in the upper layers rarely exceed 1-2 mg m-3 outside the zone influenced by the Arabian upwelling. Near 15§N, however, fluxes into sediment traps at 3 km depth indicate an onset of high primary production very soon after the arrival of the SWM and suggest a long period of high production in the open sea. The partial temporal disconnect during the SWM between pigment changes in the upper part of the euphotic zone and of fluxes into the traps is disconcerting. For future modeling of plankton production in the open Arabian Sea, the use of two size classes of phytoplankton is recommended. The utility of satellite-derived pigment concentrations (as opposed to temporal changes of pigment) for testing such models is questioned.
Hitchcock,G.L.,Key,E.L.,Masters,J.
The fate of upwelled waters in the Great Whirl, August 1995 Journal Article
In: Deep-Sea Research Part II, vol. 47, no. 111, pp. 1605-1621, 2000.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, Distribution, temperature, thermocline, Upwelling
@article{,
title = {The fate of upwelled waters in the Great Whirl, August 1995},
author = {Hitchcock,G.L.,Key,E.L.,Masters,J.},
year = {2000},
date = {2000-01-01},
journal = {Deep-Sea Research Part II},
volume = {47},
number = {111},
pages = {1605-1621},
abstract = {The Great Whirl is a large, anticyclonic gyre that develops of the northern Somali coast during the Southwest Monsoon. In August 1995 the NOAA Ship Malcolm Baldrige surveyed the seaward edge of the upwelling zone associated with this gyre. The fate of recently upwelled water was followed by mapping surface property distributions along a cool surface feature that extended seaward along the northern edge of the Great Whirl. Surface properties (T, S, and chlorophyll a), surface velocity (ADCP), and XBT and CTD casts were interpreted in relation to the trajectories of three instrumented surface drifters deployed in the feature. Cool surface waters correspond in space to the shoaling of the upper thermocline and offshore advection from the coast. Surface chlorophyll a concentrations decreased from 2 to 3 æg l-1 in the Upwelling zone to 0.5-1.5 æg l-1 in the surface feature and contiguous waters. Maximum surface velocities in the Great Whirl were 250 cm s-1 with velocities >100 cm s-1 along the northern perimeter of the gyre. Decorrelation time-scales for u and v velocity components, and chlorophyll a fluorescence, from the drifters were on the order of 4 to 7 days. These times are comparable to those over which the drifters were ejected from the Great Whirl into the Socotra Gyre. Decorrelation times for sea-surface temperature were somewhat longer (10 days). All three platforms passed between the Somali coast and Socotra within a week of their deployment and then traveled east into the northern Arabian Sea.},
keywords = {Arabian Sea, chlorophyll, Distribution, temperature, thermocline, Upwelling},
pubstate = {published},
tppubtype = {article}
}
The Great Whirl is a large, anticyclonic gyre that develops of the northern Somali coast during the Southwest Monsoon. In August 1995 the NOAA Ship Malcolm Baldrige surveyed the seaward edge of the upwelling zone associated with this gyre. The fate of recently upwelled water was followed by mapping surface property distributions along a cool surface feature that extended seaward along the northern edge of the Great Whirl. Surface properties (T, S, and chlorophyll a), surface velocity (ADCP), and XBT and CTD casts were interpreted in relation to the trajectories of three instrumented surface drifters deployed in the feature. Cool surface waters correspond in space to the shoaling of the upper thermocline and offshore advection from the coast. Surface chlorophyll a concentrations decreased from 2 to 3 æg l-1 in the Upwelling zone to 0.5-1.5 æg l-1 in the surface feature and contiguous waters. Maximum surface velocities in the Great Whirl were 250 cm s-1 with velocities >100 cm s-1 along the northern perimeter of the gyre. Decorrelation time-scales for u and v velocity components, and chlorophyll a fluorescence, from the drifters were on the order of 4 to 7 days. These times are comparable to those over which the drifters were ejected from the Great Whirl into the Socotra Gyre. Decorrelation times for sea-surface temperature were somewhat longer (10 days). All three platforms passed between the Somali coast and Socotra within a week of their deployment and then traveled east into the northern Arabian Sea.
Toon,R.K.,Lohrenz,S.E.,Rathbun,C.E.,Wood,A.M.,Arnone,R.A.,Jones,B.H.,Kindle,J.C.,Weidemann,A.D.
Photosynthesis-irradiance parameters and community structure associated with coastal filaments and adjacent waters in the northern Arabian Sea Journal Article
In: Deep-Sea Research Part II, vol. 47, no. 244, pp. 1249-1277, 2000.
Abstract | BibTeX | Tags: Arabian Sea, biology, chlorophyll, Distribution, salinity, Upwelling
@article{,
title = {Photosynthesis-irradiance parameters and community structure associated with coastal filaments and adjacent waters in the northern Arabian Sea},
author = {Toon,R.K.,Lohrenz,S.E.,Rathbun,C.E.,Wood,A.M.,Arnone,R.A.,Jones,B.H.,Kindle,J.C.,Weidemann,A.D.},
year = {2000},
date = {2000-01-01},
journal = {Deep-Sea Research Part II},
volume = {47},
number = {244},
pages = {1249-1277},
abstract = {Comparisons were made among size-fractionated photosynthesis-irradiance (P-E) parameters, chlorophyll a size distributions, and accessory pigment composition of natural phytoplankton assemblages in filaments, coastal upwelling waters, and an oligotrophic region of the northern Arabian Sea during the Fall Intermonsoon in 1995. Differences between P-E parameters, PBmax and àB, were observed between filaments and adjacent waters and were associated with differences in phytoplankton community structure. In a southern filament and coastal upwelled waters, the majority of the estimated biomass (chlorophyll a) was present in the larger (2-20 and 20-200 æm) size fractions; dominant accessory pigments were 19'-butanoyloxyfucoxanthin and peridinin. In higher salinity waters, high percentages of chlorophyll a and lutein/zeaxanthin were observed in the smallest size-fraction (<2 æm). Whole water values of PBmax ranged from 1.77 to 2.31 (g C g chl a-1 h-1) when the majority of the biomass was in the largest fractions. Higher values (more than 4.48 g C g chl a-1 h-1) were determined in whole water samples for communities comprised primarily of small cells. A size dependence was also observed in the value of àB, 0.017 or greater (g C g chl a-1 h-1)/(æmol quanta m-2 s-1) for whole water samples at stations dominated by small cells and 0.013 when derived from stations dominated by large cells. The observed pattern of larger phytoplankton associated with upwelling and filament waters was consistent with previous investigations and was, for the most part, comparable to findings in the California Current system. Our results show that differences in taxonomic composition and photosynthetic characteristics were indeed present between filament waters and other distinct regions; these results suggest that taxonomic variations may be associated with size-related variations in P-E parameters. Our findings provide a unique data set describing filament biology in the northern Arabian Sea during the Fall Intermonsoon thus adding important details in efforts to model biogeochemical processes in this region. },
keywords = {Arabian Sea, biology, chlorophyll, Distribution, salinity, Upwelling},
pubstate = {published},
tppubtype = {article}
}
Comparisons were made among size-fractionated photosynthesis-irradiance (P-E) parameters, chlorophyll a size distributions, and accessory pigment composition of natural phytoplankton assemblages in filaments, coastal upwelling waters, and an oligotrophic region of the northern Arabian Sea during the Fall Intermonsoon in 1995. Differences between P-E parameters, PBmax and àB, were observed between filaments and adjacent waters and were associated with differences in phytoplankton community structure. In a southern filament and coastal upwelled waters, the majority of the estimated biomass (chlorophyll a) was present in the larger (2-20 and 20-200 æm) size fractions; dominant accessory pigments were 19'-butanoyloxyfucoxanthin and peridinin. In higher salinity waters, high percentages of chlorophyll a and lutein/zeaxanthin were observed in the smallest size-fraction (<2 æm). Whole water values of PBmax ranged from 1.77 to 2.31 (g C g chl a-1 h-1) when the majority of the biomass was in the largest fractions. Higher values (more than 4.48 g C g chl a-1 h-1) were determined in whole water samples for communities comprised primarily of small cells. A size dependence was also observed in the value of àB, 0.017 or greater (g C g chl a-1 h-1)/(æmol quanta m-2 s-1) for whole water samples at stations dominated by small cells and 0.013 when derived from stations dominated by large cells. The observed pattern of larger phytoplankton associated with upwelling and filament waters was consistent with previous investigations and was, for the most part, comparable to findings in the California Current system. Our results show that differences in taxonomic composition and photosynthetic characteristics were indeed present between filament waters and other distinct regions; these results suggest that taxonomic variations may be associated with size-related variations in P-E parameters. Our findings provide a unique data set describing filament biology in the northern Arabian Sea during the Fall Intermonsoon thus adding important details in efforts to model biogeochemical processes in this region.
Wiggert,J.D.,Jones,B.H.,Dickey,T.D.,Brink,K.H.,Weller,R.A.,Marra,J.,Codispoti,L.A.
The Northeast Monsoon's impact on mixing, phytoplankton biomass and nutrient cycling in the Arabian Sea Journal Article
In: Deep-Sea Research Part II, vol. 47, no. 254, pp. 1353-1385, 2000.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, depth, growth, impact, lead, productivity, surface temperature, temperature, zooplankton
@article{,
title = {The Northeast Monsoon's impact on mixing, phytoplankton biomass and nutrient cycling in the Arabian Sea},
author = {Wiggert,J.D.,Jones,B.H.,Dickey,T.D.,Brink,K.H.,Weller,R.A.,Marra,J.,Codispoti,L.A.},
year = {2000},
date = {2000-01-01},
journal = {Deep-Sea Research Part II},
volume = {47},
number = {254},
pages = {1353-1385},
abstract = {In the northern Arabian Sea, atmospheric conditions during the Northeast (winter) Monsoon lead to deep convective mixing. Due to the proximity of the permanent pycnocline to the sea surface, this mixing does not penetrate below 125 m. However, a strong nitracline is also present and the deep convection results in significant nitrate flux into the surface waters. This leads to nitrate concentrations over the upper 100 m that exceed 4 æM toward the end of the monsoon. During the 1994/1995 US JGOFS/Arabian Sea expedition, the mean areal gross primary production over two successive Northeast Monsoons was determined to be 1.35 gC/m2/d. Thus, despite the deep penetrative convection, high rates of primary productivity were maintained. An interdisciplinary model was developed to elucidate the biogeochemical processes involved in supporting the elevated productivity. This model consisted of a 1-D mixed-layer model coupled to a set of equations that tracked phytoplankton growth and the concentration of the two major nutrients (nitrate and ammonium). Zooplankton grazing was parameterized by a rate constant determined by shipboard experiments. Model boundary conditions consist of meteorological time-series measured from the surface buoy that was part of the ONR Arabian Sea Experiment's central mooring. Our numerical experiments show that elevated surface evaporation, and the associated salinization of the mixed layer, strongly contributes to the frequency and penetration depth of the observed convective mixing. Cooler surface temperatures, increased nitrate entrainment, reduced water column stratification, and lower near-surface chlorophyll a concentrations all result from this enhanced mixing. The model also captured a dependence on regenerated nitrogen observed in nutrient uptake experiments performed during the Northeast Monsoon. Our numerical experiments also indicate that variability in mean pycnocline depth causes up to a 25% reduction in areal chlorophyll a concentration. We hypothesize that such shifts in pycnocline depth may contribute to the interannual variations in primary production and surface chlorophyll a concentration that have been previously observed in this region.},
keywords = {Arabian Sea, chlorophyll, depth, growth, impact, lead, productivity, surface temperature, temperature, zooplankton},
pubstate = {published},
tppubtype = {article}
}
In the northern Arabian Sea, atmospheric conditions during the Northeast (winter) Monsoon lead to deep convective mixing. Due to the proximity of the permanent pycnocline to the sea surface, this mixing does not penetrate below 125 m. However, a strong nitracline is also present and the deep convection results in significant nitrate flux into the surface waters. This leads to nitrate concentrations over the upper 100 m that exceed 4 æM toward the end of the monsoon. During the 1994/1995 US JGOFS/Arabian Sea expedition, the mean areal gross primary production over two successive Northeast Monsoons was determined to be 1.35 gC/m2/d. Thus, despite the deep penetrative convection, high rates of primary productivity were maintained. An interdisciplinary model was developed to elucidate the biogeochemical processes involved in supporting the elevated productivity. This model consisted of a 1-D mixed-layer model coupled to a set of equations that tracked phytoplankton growth and the concentration of the two major nutrients (nitrate and ammonium). Zooplankton grazing was parameterized by a rate constant determined by shipboard experiments. Model boundary conditions consist of meteorological time-series measured from the surface buoy that was part of the ONR Arabian Sea Experiment's central mooring. Our numerical experiments show that elevated surface evaporation, and the associated salinization of the mixed layer, strongly contributes to the frequency and penetration depth of the observed convective mixing. Cooler surface temperatures, increased nitrate entrainment, reduced water column stratification, and lower near-surface chlorophyll a concentrations all result from this enhanced mixing. The model also captured a dependence on regenerated nitrogen observed in nutrient uptake experiments performed during the Northeast Monsoon. Our numerical experiments also indicate that variability in mean pycnocline depth causes up to a 25% reduction in areal chlorophyll a concentration. We hypothesize that such shifts in pycnocline depth may contribute to the interannual variations in primary production and surface chlorophyll a concentration that have been previously observed in this region.
Brown,S.L.,Landry,M.R.,Barber,R.T.,Campbell,L.,Garrison,D.L.,Gowing,M.M.
Picophytoplankton dynamics and production in the Arabian Sea during the 1995 Southwest Monsoon Journal Article
In: Deep-Sea Research Part II, vol. 46, no. 56, pp. 1745-1768, 1999.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, growth, impact, Oceanic, population, populations, productivity, Upwelling
@article{,
title = {Picophytoplankton dynamics and production in the Arabian Sea during the 1995 Southwest Monsoon},
author = {Brown,S.L.,Landry,M.R.,Barber,R.T.,Campbell,L.,Garrison,D.L.,Gowing,M.M.},
year = {1999},
date = {1999-01-01},
journal = {Deep-Sea Research Part II},
volume = {46},
number = {56},
pages = {1745-1768},
abstract = {Phytoplankton community structure is expected to shift to larger cells (e.g., diatoms) with monsoonal forcing in the Arabian Sea, but recent studies suggest that small primary producers remain active and important, even in areas strongly influenced by coastal upwelling. To better understand the role of smaller phytoplankton in such systems, we investigated growth and grazing rates of picophytoplankton populations and their contributions to phytoplankton community biomass and primary productivity during the 1995 Southwest Monsoon (August-September). Environmental conditions at six study stations varied broadly from openocean oligotrophic to coastal eutrophic, with mixed-layer nitrate and chlorophyll concentrations ranging from 0.01 to 11.5 æM NO3 and 0.16 to 1.5 æg Chl a. Picophytoplankton comprised up to 92% of phytoplankton carbon at the oceanic stations, 35% in the diatom dominated coastal zone, and 26% in a declining Phaeocystis bloom. Concurrent in situ dilution and 14C-uptake experiments gave comparable ranges of community growth rates (0.53-1.05 d-1 and 0.44-1.17 d-1, to the 1% light level), but uncertainties in C:Chl a confounded agreement at individual stations. Microzooplankton grazing utilized 81% of community phytoplankton growth at the oligotrophic stations and 54% at high-nutrient coastal stations. Prochlorococcus (PRO) was present at two oligotrophic stations, where its maximum growth approached 1.4 d-1 (two doublings per day) and depth-integrated growth varied from 0.2 to 0.8 d-1. Synechococcus (SYN) growth ranged from 0.5 to 1.1 d-1 at offshore stations and 0.6 to 0.7 d-1 at coastal sites. Except for the most oligotrophic stations, growth rates of picoeukaryotic algae (PEUK) exceeded PRO and SYN, reaching 1.3 d-1 offshore and decreasing to 0.8 d-1 at the most coastal station. Microzooplankton grazing impact averaged 90, 70, and 86% of growth for PRO, SYN, and PEUK, respectively. Picoplankton as a group accounted for 64% of estimated gross carbon production for all stations, and 50% at highnutrient, upwelling stations. Prokaryotes (PRO and SYN) contributed disproportionately to production relative to biomass at the most oligotrophic station, while PEUK were more important at the coastal stations. Even during intense monsoonal forcing in the Arabian Sea, picoeukaryotic algae appear to account for a large portion of primary production in the coastal upwelling regions, supporting an active community of protistan grazers and a high rate of carbon cycling in these areas. },
keywords = {Arabian Sea, chlorophyll, growth, impact, Oceanic, population, populations, productivity, Upwelling},
pubstate = {published},
tppubtype = {article}
}
Phytoplankton community structure is expected to shift to larger cells (e.g., diatoms) with monsoonal forcing in the Arabian Sea, but recent studies suggest that small primary producers remain active and important, even in areas strongly influenced by coastal upwelling. To better understand the role of smaller phytoplankton in such systems, we investigated growth and grazing rates of picophytoplankton populations and their contributions to phytoplankton community biomass and primary productivity during the 1995 Southwest Monsoon (August-September). Environmental conditions at six study stations varied broadly from openocean oligotrophic to coastal eutrophic, with mixed-layer nitrate and chlorophyll concentrations ranging from 0.01 to 11.5 æM NO3 and 0.16 to 1.5 æg Chl a. Picophytoplankton comprised up to 92% of phytoplankton carbon at the oceanic stations, 35% in the diatom dominated coastal zone, and 26% in a declining Phaeocystis bloom. Concurrent in situ dilution and 14C-uptake experiments gave comparable ranges of community growth rates (0.53-1.05 d-1 and 0.44-1.17 d-1, to the 1% light level), but uncertainties in C:Chl a confounded agreement at individual stations. Microzooplankton grazing utilized 81% of community phytoplankton growth at the oligotrophic stations and 54% at high-nutrient coastal stations. Prochlorococcus (PRO) was present at two oligotrophic stations, where its maximum growth approached 1.4 d-1 (two doublings per day) and depth-integrated growth varied from 0.2 to 0.8 d-1. Synechococcus (SYN) growth ranged from 0.5 to 1.1 d-1 at offshore stations and 0.6 to 0.7 d-1 at coastal sites. Except for the most oligotrophic stations, growth rates of picoeukaryotic algae (PEUK) exceeded PRO and SYN, reaching 1.3 d-1 offshore and decreasing to 0.8 d-1 at the most coastal station. Microzooplankton grazing impact averaged 90, 70, and 86% of growth for PRO, SYN, and PEUK, respectively. Picoplankton as a group accounted for 64% of estimated gross carbon production for all stations, and 50% at highnutrient, upwelling stations. Prokaryotes (PRO and SYN) contributed disproportionately to production relative to biomass at the most oligotrophic station, while PEUK were more important at the coastal stations. Even during intense monsoonal forcing in the Arabian Sea, picoeukaryotic algae appear to account for a large portion of primary production in the coastal upwelling regions, supporting an active community of protistan grazers and a high rate of carbon cycling in these areas.
Caron,D.A.,Dennett,M.R.
Phytoplankton growth and mortality during the 1995 Northeast Monsoon and Spring Intermonsoon in the Arabian Sea Journal Article
In: Deep-Sea Research Part II, vol. 46, no. 63, pp. 1665-1690, 1999.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, growth, mortality, Oceanic, trend, Trends
@article{,
title = {Phytoplankton growth and mortality during the 1995 Northeast Monsoon and Spring Intermonsoon in the Arabian Sea},
author = {Caron,D.A.,Dennett,M.R.},
year = {1999},
date = {1999-01-01},
journal = {Deep-Sea Research Part II},
volume = {46},
number = {63},
pages = {1665-1690},
abstract = {Phytoplankton growth rates and mortality rates were experimentally examined at eight stations in the Arabian Sea along the U.S. JGOFS cruise track during the 1995 Northeast Monsoon (January) and Spring Intermonsoon (March-April). Instantaneous growth rates averaged over an entire cruise were approximately twice as high during the NE Monsoon than during the Spring Intermonsoon period (overall averages of 0.84 ñ 0.29 (s.d.) versus 0.44 ñ 0.19 d-1). Average herbivore grazing (mortality) rates, however, were quite similar for the two seasons (overall averages of 0.35 ñ 0.18 and 0.30 ñ 0.17 d-1 for the NE Monsoon and Spring Intermonsoon, respectively). The absolute amounts of phytoplankton biomass consumed during each season also were similar (29 and 25% of standing stock consumed d-1 for the January and March-April cruises, respectively), as were the geographical trends of this removal. These seasonal trends in growth and removal rates resulted in net phytoplankton growth rates that were considerably higher during the January cruise (0.48 d-1) than during the March-April cruise (0.14 d-1). That is, phytoplankton production was more closely balanced during the Spring Intermonsoon season (87% of daily primary production consumed) relative to the NE Monsoon season (49% of daily primary production consumed). Station-to-station variability was high for rate measurements during either cruise. Nevertheless, there was a clear onshore-offshore trend in the absolute rate of removal of phytoplankton biomass (æg chlorophyll consumed l-1 d-1) during both cruises. Coastal stations had removal rates that were typically 2-4 times higher than removal rates at oceanic stations.},
keywords = {Arabian Sea, chlorophyll, growth, mortality, Oceanic, trend, Trends},
pubstate = {published},
tppubtype = {article}
}
Phytoplankton growth rates and mortality rates were experimentally examined at eight stations in the Arabian Sea along the U.S. JGOFS cruise track during the 1995 Northeast Monsoon (January) and Spring Intermonsoon (March-April). Instantaneous growth rates averaged over an entire cruise were approximately twice as high during the NE Monsoon than during the Spring Intermonsoon period (overall averages of 0.84 ñ 0.29 (s.d.) versus 0.44 ñ 0.19 d-1). Average herbivore grazing (mortality) rates, however, were quite similar for the two seasons (overall averages of 0.35 ñ 0.18 and 0.30 ñ 0.17 d-1 for the NE Monsoon and Spring Intermonsoon, respectively). The absolute amounts of phytoplankton biomass consumed during each season also were similar (29 and 25% of standing stock consumed d-1 for the January and March-April cruises, respectively), as were the geographical trends of this removal. These seasonal trends in growth and removal rates resulted in net phytoplankton growth rates that were considerably higher during the January cruise (0.48 d-1) than during the March-April cruise (0.14 d-1). That is, phytoplankton production was more closely balanced during the Spring Intermonsoon season (87% of daily primary production consumed) relative to the NE Monsoon season (49% of daily primary production consumed). Station-to-station variability was high for rate measurements during either cruise. Nevertheless, there was a clear onshore-offshore trend in the absolute rate of removal of phytoplankton biomass (æg chlorophyll consumed l-1 d-1) during both cruises. Coastal stations had removal rates that were typically 2-4 times higher than removal rates at oceanic stations.
Gardner,W.D.,Gundersen,J.S.,Richardson,M.J.,Walsh,I.D.
The role of seasonal and diel changes in mixed-layer depth on carbon and chlorophyll distributions in the Arabian Sea Journal Article
In: Deep-Sea Research Part II, vol. 46, no. 97, pp. 1833-1858, 1999.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, density, depth, diel, Distribution, nearshore, Oceanic, Upwelling
@article{,
title = {The role of seasonal and diel changes in mixed-layer depth on carbon and chlorophyll distributions in the Arabian Sea},
author = {Gardner,W.D.,Gundersen,J.S.,Richardson,M.J.,Walsh,I.D.},
year = {1999},
date = {1999-01-01},
journal = {Deep-Sea Research Part II},
volume = {46},
number = {97},
pages = {1833-1858},
abstract = {The e!ects of changes in the mixed-layer depth on the distribution of particulate organic carbon (POC) and chlorophyll a were examined in the Arabian Sea during the Northeast Monsoon (January and December), Spring Intermonsoon (February-March), and Southwest Monsoon (July and August) of 1995. POC distributions were derived from profiles of beam attenuation calibrated with POC, and chlorophyll a distributions were derived from calibrated fluorescence profiles. Depth of the seasonal mixed layer (Då of 0.125 kg m-3 from surface density) increased with distance offshore during both monsoons, especially in the southern Arabian Sea where the range was 10-80 m nearshore to 80-120 m offshore. The deepest seasonal mixed layers occurred during the Northeast Monsoon. During the Spring Intermonsoon the seasonal mixed layer was only 10-40 m. Variations in the depth of the diel mixed layer (Då of 0.03 kg m-3 from surface density) were up to 90 m during the Northeast Monsoon, but were seldom over 20 m during the Southwest Monsoon. During the Spring Intermonsoon when mixed layers and diel variations in the mixed layer were small, nutrients became depleted, producing oligotrophic conditions plus a strong deep chlorophyll a maximum (>2 mg chl m-3) below the mixed layer. The chlorophyll a maximum was centered at ~ 50 m, which is significantly beneath the effective depth of satellite color sensing. When mixing is active throughout the diel cycle, particulate organic carbon (POC) and chlorophyll distributions are quite uniform within the mixed layer. Nighttime increases in mixed layer depths can mix POC and chlorophyll a produced during the day downward and can entrain new nutrients to enhance primary production. Although mixing from diel variations may be effective in redistributing components within the mixed layer and may be an important mechanism for removing particles from the mixed layer, regional upwelling of nutrients and diatom blooms appear to dominate over diel mixed layer dynamics in the production and export of carbon in the Arabian Sea.},
keywords = {Arabian Sea, chlorophyll, density, depth, diel, Distribution, nearshore, Oceanic, Upwelling},
pubstate = {published},
tppubtype = {article}
}
The e!ects of changes in the mixed-layer depth on the distribution of particulate organic carbon (POC) and chlorophyll a were examined in the Arabian Sea during the Northeast Monsoon (January and December), Spring Intermonsoon (February-March), and Southwest Monsoon (July and August) of 1995. POC distributions were derived from profiles of beam attenuation calibrated with POC, and chlorophyll a distributions were derived from calibrated fluorescence profiles. Depth of the seasonal mixed layer (Då of 0.125 kg m-3 from surface density) increased with distance offshore during both monsoons, especially in the southern Arabian Sea where the range was 10-80 m nearshore to 80-120 m offshore. The deepest seasonal mixed layers occurred during the Northeast Monsoon. During the Spring Intermonsoon the seasonal mixed layer was only 10-40 m. Variations in the depth of the diel mixed layer (Då of 0.03 kg m-3 from surface density) were up to 90 m during the Northeast Monsoon, but were seldom over 20 m during the Southwest Monsoon. During the Spring Intermonsoon when mixed layers and diel variations in the mixed layer were small, nutrients became depleted, producing oligotrophic conditions plus a strong deep chlorophyll a maximum (>2 mg chl m-3) below the mixed layer. The chlorophyll a maximum was centered at ~ 50 m, which is significantly beneath the effective depth of satellite color sensing. When mixing is active throughout the diel cycle, particulate organic carbon (POC) and chlorophyll distributions are quite uniform within the mixed layer. Nighttime increases in mixed layer depths can mix POC and chlorophyll a produced during the day downward and can entrain new nutrients to enhance primary production. Although mixing from diel variations may be effective in redistributing components within the mixed layer and may be an important mechanism for removing particles from the mixed layer, regional upwelling of nutrients and diatom blooms appear to dominate over diel mixed layer dynamics in the production and export of carbon in the Arabian Sea.
Johnson,Z.,Landry,M.L.,Bidigare,R.R.,Brown,S.L.,Campbell,L.,Gunderson,J.,Marra,J.,Trees,C.
Energetics and growth kinetics of a deep Prochlorococcus spp. population in the Arabian Sea Journal Article
In: Deep-Sea Research Part II, vol. 46, no. 129, pp. 1719-1743, 1999.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, growth, marine, performance, population, populations
@article{,
title = {Energetics and growth kinetics of a deep Prochlorococcus spp. population in the Arabian Sea},
author = {Johnson,Z.,Landry,M.L.,Bidigare,R.R.,Brown,S.L.,Campbell,L.,Gunderson,J.,Marra,J.,Trees,C.},
year = {1999},
date = {1999-01-01},
journal = {Deep-Sea Research Part II},
volume = {46},
number = {129},
pages = {1719-1743},
abstract = {During the US JGOFS process studies in the Arabian Sea (1995), secondary fluorescence maxima (SFM) were observed frequently at the oxic-anoxic interface at the extreme base of the euphotic zone. These secondary peaks were most prominent during the early NE monsoon in the central oligotrophic portion of the Arabian Sea, although they were spatially and temporally variable. Based on high performance liquid chromatography (HPLC) and flow cytometry analyses, SFM were determined to be populated almost exclusively by the marine cyanobacterium Prochlorococcus spp. While SFM were about half the magnitude of primary fluorescence peaks, chlorophyll a biomass was typically an order of magnitude less than at the primary maxima (although total chlorophyll (a + b) differed only by a factor of two). Photosynthesis versus irradiance response curves revealed an efficient population adapted to extremely low light (~0.02-0.05% surface irradiance) largely through increased light absorption capabilities. A theoretical spectral irradiance absorption effciency model based on available spectral irradiance, individual cell properties, and bulk particulate spectral absorption also supports a well-adapted low-light population. Deck-incubated C-14 uptake as well as dilution growth experiments revealed instantaneous growth rates on the order of æ = 0.01 d-1. However, additional in situ observations suggest SFM populations may be more dynamic than the growth rates estimates from shipboard bottle incubations predict. We advance four hypotheses for the regulation of SFM populations including: (1) reduced loss rates, (2) discontinuous environmental conditions, (3) enhanced sub-oxic growth, and (4) physical mechanisms.},
keywords = {Arabian Sea, chlorophyll, growth, marine, performance, population, populations},
pubstate = {published},
tppubtype = {article}
}
During the US JGOFS process studies in the Arabian Sea (1995), secondary fluorescence maxima (SFM) were observed frequently at the oxic-anoxic interface at the extreme base of the euphotic zone. These secondary peaks were most prominent during the early NE monsoon in the central oligotrophic portion of the Arabian Sea, although they were spatially and temporally variable. Based on high performance liquid chromatography (HPLC) and flow cytometry analyses, SFM were determined to be populated almost exclusively by the marine cyanobacterium Prochlorococcus spp. While SFM were about half the magnitude of primary fluorescence peaks, chlorophyll a biomass was typically an order of magnitude less than at the primary maxima (although total chlorophyll (a + b) differed only by a factor of two). Photosynthesis versus irradiance response curves revealed an efficient population adapted to extremely low light (~0.02-0.05% surface irradiance) largely through increased light absorption capabilities. A theoretical spectral irradiance absorption effciency model based on available spectral irradiance, individual cell properties, and bulk particulate spectral absorption also supports a well-adapted low-light population. Deck-incubated C-14 uptake as well as dilution growth experiments revealed instantaneous growth rates on the order of æ = 0.01 d-1. However, additional in situ observations suggest SFM populations may be more dynamic than the growth rates estimates from shipboard bottle incubations predict. We advance four hypotheses for the regulation of SFM populations including: (1) reduced loss rates, (2) discontinuous environmental conditions, (3) enhanced sub-oxic growth, and (4) physical mechanisms.
Brock,J.C.,Sathyendranath,S.,Platt,T.
Biohydro-optical classification of the northwestern Indian Ocean Journal Article
In: Marine Ecology Progress Series, vol. 165, no. 338, pp. 1-15, 1998.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, ecosystem, Gulf of Masirah, Indian Ocean, Oman, plankton, Upwelling
@article{,
title = {Biohydro-optical classification of the northwestern Indian Ocean},
author = {Brock,J.C.,Sathyendranath,S.,Platt,T.},
year = {1998},
date = {1998-01-01},
journal = {Marine Ecology Progress Series},
volume = {165},
number = {338},
pages = {1-15},
abstract = {An approach to a partial solution to the general problem of defining biogeochemical provinces for the accurate estimation of global-ocean primary production and realistic structuring of epipelagic plankton ecosystem models is presented for the northwestern Indian Ocean. This is accomplished through use of a new technique, biohydro-optical classification, that applies a rudimentary submarine light budget incorporating climatologies of incident light, mixed layer thickness, and chlorophyll to recognize fundamental modes of tropical plankton ecosystems. The three types of biohydro-optical classes found in the Arabian Sea, Typical Tropical, Mixed-Layer Bloom, and Transitional, are shown to evolve thorough the spring intermonsoon (March through May) summer southwest monsoon (June thorough August), and fall intermonsoon (Sep through Nov) under climatic forcing and in response to the resulting biological variability. Virtually all of the open Arabian Sea is within the Typical Tropical Class at the close of the spring intermonsoon. This class type is intended to identify the maximum (DCM) maintained by active algal growth, and light-rich oligotrophic shallow zone containing phytoplankton association which depends largely on regenerated nutrients. At the close of the southwest monsoon in August, a mixed layer bloom province covers much of the northern Arabian Sea. This province class corresponds to the ecosystem mode represented by tropical regions undergoing marginal or mid-ocean upwelling and greatly simplifies regional extrapolation of the local primary production algorithm. At the onset of the fall intermonsoon, the mixed layer algal bloom province in the northern and western Arabian Sea is superseded by a transitional province, which persists through the fall intermonsoon. We interpret the upper layer of the fall intermonsoon transitional province in the Arabian Sea as a special case of the shallow regenerative plankton ecosystem of oligotrophic ocean areas, where rates of zooplankton-driven nutrient regeneration and recycled production, key processes in the upper layer of the classic 2-layer euphotic zone or oligotrophic low-latitude oceans, reach extreme values.Note on diagrams/maps in paper:Of all the regions of the nw Arabian Sea, the coastal areas off Oman and Yemen are most often in the Transitional or Mixed layer bloom classes. The Gulf of Masirah maintains a mixed layer bloom class thorughout the year, even when other coastal areas of Oman switch to a Transitional class.},
keywords = {Arabian Sea, chlorophyll, ecosystem, Gulf of Masirah, Indian Ocean, Oman, plankton, Upwelling},
pubstate = {published},
tppubtype = {article}
}
An approach to a partial solution to the general problem of defining biogeochemical provinces for the accurate estimation of global-ocean primary production and realistic structuring of epipelagic plankton ecosystem models is presented for the northwestern Indian Ocean. This is accomplished through use of a new technique, biohydro-optical classification, that applies a rudimentary submarine light budget incorporating climatologies of incident light, mixed layer thickness, and chlorophyll to recognize fundamental modes of tropical plankton ecosystems. The three types of biohydro-optical classes found in the Arabian Sea, Typical Tropical, Mixed-Layer Bloom, and Transitional, are shown to evolve thorough the spring intermonsoon (March through May) summer southwest monsoon (June thorough August), and fall intermonsoon (Sep through Nov) under climatic forcing and in response to the resulting biological variability. Virtually all of the open Arabian Sea is within the Typical Tropical Class at the close of the spring intermonsoon. This class type is intended to identify the maximum (DCM) maintained by active algal growth, and light-rich oligotrophic shallow zone containing phytoplankton association which depends largely on regenerated nutrients. At the close of the southwest monsoon in August, a mixed layer bloom province covers much of the northern Arabian Sea. This province class corresponds to the ecosystem mode represented by tropical regions undergoing marginal or mid-ocean upwelling and greatly simplifies regional extrapolation of the local primary production algorithm. At the onset of the fall intermonsoon, the mixed layer algal bloom province in the northern and western Arabian Sea is superseded by a transitional province, which persists through the fall intermonsoon. We interpret the upper layer of the fall intermonsoon transitional province in the Arabian Sea as a special case of the shallow regenerative plankton ecosystem of oligotrophic ocean areas, where rates of zooplankton-driven nutrient regeneration and recycled production, key processes in the upper layer of the classic 2-layer euphotic zone or oligotrophic low-latitude oceans, reach extreme values.Note on diagrams/maps in paper:Of all the regions of the nw Arabian Sea, the coastal areas off Oman and Yemen are most often in the Transitional or Mixed layer bloom classes. The Gulf of Masirah maintains a mixed layer bloom class thorughout the year, even when other coastal areas of Oman switch to a Transitional class.
Savidge,G.,Lennon,J.,Matthews,A.J.
A shore-based survey of upwelling along the coast of Dhofar region, southern Oman Journal Article
In: Continental Shelf Research, vol. 10, no. 471, pp. 259-275, 1990.
Abstract | BibTeX | Tags: bathymetry, chlorophyll, Oman, salinity, survey, temperature, Upwelling
@article{,
title = {A shore-based survey of upwelling along the coast of Dhofar region, southern Oman},
author = {Savidge,G.,Lennon,J.,Matthews,A.J.},
year = {1990},
date = {1990-01-01},
journal = {Continental Shelf Research},
volume = {10},
number = {471},
pages = {259-275},
abstract = {A shore-based survey of hydrographic variables along the southern Oman coast between 16ø55'N, 53ø55'E and 170Z3'N, 55ø17.5'E was carried out between August and November 1985 during the southwest monsoon season and the succeeding period marked by the onset of the northeast winds. During the monsoon season strong evidence of upwelling based on temperature and nutrient data was apparent for the eastern half of the survey area which was distinguished by severe coastal relief and a steeply shelving bathymetry. The upwelled water appeared to be advected westwards into the shallower waters of Salalah Bay which comprised the western part of the survey area. Maximum stratification as inferred from increased temperatures and decreased nutrient concentrations was recorded at the western end of Salalah Bay. Marked increases in chlorophyll a were apparent within the Bay at the boundary between the stratified and upwelled water but concentrations were low within the main bodies of the two water types. The upwelling process was discontinuous in time but the intensity of the upwelling was not apparently related to variation in wind strength; only minimal variations in the velocity of the prevailing southwest wind were recorded during the major part of the survey period. Regular diurnal changes of variable amplitude were observed for all properties sampled with the exception of salinity.},
keywords = {bathymetry, chlorophyll, Oman, salinity, survey, temperature, Upwelling},
pubstate = {published},
tppubtype = {article}
}
A shore-based survey of hydrographic variables along the southern Oman coast between 16ø55'N, 53ø55'E and 170Z3'N, 55ø17.5'E was carried out between August and November 1985 during the southwest monsoon season and the succeeding period marked by the onset of the northeast winds. During the monsoon season strong evidence of upwelling based on temperature and nutrient data was apparent for the eastern half of the survey area which was distinguished by severe coastal relief and a steeply shelving bathymetry. The upwelled water appeared to be advected westwards into the shallower waters of Salalah Bay which comprised the western part of the survey area. Maximum stratification as inferred from increased temperatures and decreased nutrient concentrations was recorded at the western end of Salalah Bay. Marked increases in chlorophyll a were apparent within the Bay at the boundary between the stratified and upwelled water but concentrations were low within the main bodies of the two water types. The upwelling process was discontinuous in time but the intensity of the upwelling was not apparently related to variation in wind strength; only minimal variations in the velocity of the prevailing southwest wind were recorded during the major part of the survey period. Regular diurnal changes of variable amplitude were observed for all properties sampled with the exception of salinity.
Banse,K.
Seasonality of phytoplankton chlorophyll in the central and northern Arabian Sea Journal Article
In: Deep-Sea Research, vol. 34, no. 35, pp. 713-723, 1987.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, depth
@article{,
title = {Seasonality of phytoplankton chlorophyll in the central and northern Arabian Sea},
author = {Banse,K.},
year = {1987},
date = {1987-01-01},
journal = {Deep-Sea Research},
volume = {34},
number = {35},
pages = {713-723},
abstract = {Marked seasonality of ship-based chlorophyll concentrations in the upper layers of the central and northern parts of the Arabian Sea is established for three hydrographically defined offshore areas. A peak related to the southwest (summer) monsoon occurs, either with or without a northeast (winter) monsoon related peak. Both appear to depend on the establishment of a deep mixed layer and the concomitant nutrient supply, but at any station the relation between pigment content and mixed-layer depth or nitrate concentration is usually obscure.},
keywords = {Arabian Sea, chlorophyll, depth},
pubstate = {published},
tppubtype = {article}
}
Marked seasonality of ship-based chlorophyll concentrations in the upper layers of the central and northern parts of the Arabian Sea is established for three hydrographically defined offshore areas. A peak related to the southwest (summer) monsoon occurs, either with or without a northeast (winter) monsoon related peak. Both appear to depend on the establishment of a deep mixed layer and the concomitant nutrient supply, but at any station the relation between pigment content and mixed-layer depth or nitrate concentration is usually obscure.