Beal,L.M.,Chereskin,T.K.,Bryden,H.L.,Ffield,A.
Variability of water properties, heat and salt fluxes in the Arabian Sea, between the onset and wane of the 1995 southwest monsoon Journal Article
In: Deep-Sea Research Part II, vol. 50, no. 42, pp. 2049-2075, 2003.
Abstract | BibTeX | Tags: Arabian Sea, density, depth, Indian Ocean, Oceanic, Red Sea, Upwelling
@article{,
title = {Variability of water properties, heat and salt fluxes in the Arabian Sea, between the onset and wane of the 1995 southwest monsoon},
author = {Beal,L.M.,Chereskin,T.K.,Bryden,H.L.,Ffield,A.},
year = {2003},
date = {2003-01-01},
journal = {Deep-Sea Research Part II},
volume = {50},
number = {42},
pages = {2049-2075},
abstract = {We investigate the variability of the circulation,water masses,heat and salt fluxes in the Arabian Sea over the course of the southwest monsoon. Two zonal sections taken along 8§30'N in 1995 as part of the Indian Ocean WOCE hydrographic program are used. The first was occupied in early June at the onset of the southwest monsoon winds,the second in late September,at the wane of the monsoon. The September section was found to be generally warmer (+0.32§C) and saltier (+0.04) than in June,despite a 50mm drop in mean sea level. Therefore,the common assumption that an increase in sea-surface height follows an increase in heat content (the hydrostatic response) does not hold. Instead,we conclude that the heat content increases due to the advection of Arabian Sea Surface Water and Red Sea Water onto the section from the north,and the drop in sea level is due to a loss of mass,rather than heat,from the water column. There are large uncertainties involved in diagnosing the heat-flux divergence across the Arabian Sea, because the seasonal variability of the water masses and circulation in the basin mean that our data are not representative of a steady state. We treat each section separately and find an oceanic heat export of -0.72PW in June and -0.19PW in September,implying a basin cooling rate of about -0.36PW in June and a slight heating of 0.12PW in September. In June the mass and heat balances are dominated by the Ekman transport and the Somali Current,with very flat density surfaces resulting in a small interior geostrophic transport. By September the Ekman transport has reduced,and it is primarily the interior transport that balances a strong Somali Current. There are two main overturning cells in June and September: A shallow one of approximate magnitude 15 Sv in June and 0 Sv in September, which reaches depths of no more than 500m and is driven by Ekman divergence at the surface; and a deep cell of magnitude 1 Sv representing a weak inflow and subsequent upwelling of Circumpolar Deep water. The deep cell implies a basin-averaged upwelling velocity of 3.2x10-5 cm s-1 through 2200 m.},
keywords = {Arabian Sea, density, depth, Indian Ocean, Oceanic, Red Sea, Upwelling},
pubstate = {published},
tppubtype = {article}
}
We investigate the variability of the circulation,water masses,heat and salt fluxes in the Arabian Sea over the course of the southwest monsoon. Two zonal sections taken along 8§30'N in 1995 as part of the Indian Ocean WOCE hydrographic program are used. The first was occupied in early June at the onset of the southwest monsoon winds,the second in late September,at the wane of the monsoon. The September section was found to be generally warmer (+0.32§C) and saltier (+0.04) than in June,despite a 50mm drop in mean sea level. Therefore,the common assumption that an increase in sea-surface height follows an increase in heat content (the hydrostatic response) does not hold. Instead,we conclude that the heat content increases due to the advection of Arabian Sea Surface Water and Red Sea Water onto the section from the north,and the drop in sea level is due to a loss of mass,rather than heat,from the water column. There are large uncertainties involved in diagnosing the heat-flux divergence across the Arabian Sea, because the seasonal variability of the water masses and circulation in the basin mean that our data are not representative of a steady state. We treat each section separately and find an oceanic heat export of -0.72PW in June and -0.19PW in September,implying a basin cooling rate of about -0.36PW in June and a slight heating of 0.12PW in September. In June the mass and heat balances are dominated by the Ekman transport and the Somali Current,with very flat density surfaces resulting in a small interior geostrophic transport. By September the Ekman transport has reduced,and it is primarily the interior transport that balances a strong Somali Current. There are two main overturning cells in June and September: A shallow one of approximate magnitude 15 Sv in June and 0 Sv in September, which reaches depths of no more than 500m and is driven by Ekman divergence at the surface; and a deep cell of magnitude 1 Sv representing a weak inflow and subsequent upwelling of Circumpolar Deep water. The deep cell implies a basin-averaged upwelling velocity of 3.2x10-5 cm s-1 through 2200 m.
Brandt,P.,Dengler,M.,Rubino,A.,Quadfasel,D.,Schott,F.
Intraseasonal variability in the southwestern Arabian Sea and its relation to the seasonal circulation Journal Article
In: Deep-Sea Research Part II, vol. 50, no. 333, pp. 2129 -2141, 2003.
Abstract | BibTeX | Tags: Arabian Sea, Oceanic, temperature
@article{,
title = {Intraseasonal variability in the southwestern Arabian Sea and its relation to the seasonal circulation},
author = {Brandt,P.,Dengler,M.,Rubino,A.,Quadfasel,D.,Schott,F.},
year = {2003},
date = {2003-01-01},
journal = {Deep-Sea Research Part II},
volume = {50},
number = {333},
pages = {2129 -2141},
abstract = {An analysis of TOPEX/POSEIDON altimeter data and in situ current and temperature data obtained between April 1995 and October 1996 from a moored array shows strong intraseasonal fluctuations in the southwestern Arabian Sea, an oceanic region where the Great Whirl (GW), a predominantly wind-generated, very energetic anticyclone, is present during the Southwest Monsoon. Fluctuation periods between 30 and 50 days, up to 100 days during some years, are observed in the 8-year altimetric dataset, mostly during late summer and fall. These fluctuations are largest in a 1000 km-wide region off the Somali, Omani and Yemeni coasts north of 5§N, suggesting a local generation mechanism. The in situ data at different moorings show strong and coherent fluctuations that are characterized by southwestward phase propagation and northward energy propagation. Their periods range from 30 to 60 days and increase steadily from July 1995 to January 1996. In the first stage, these periods are at and below the cut-off period of freely propagating, first baroclinic mode Rossby waves, but approach this theoretical limit later in the year. Instabilities of the flow in the transition region between the Southern Gyre and the GW are likely sources of these fluctuations.},
keywords = {Arabian Sea, Oceanic, temperature},
pubstate = {published},
tppubtype = {article}
}
An analysis of TOPEX/POSEIDON altimeter data and in situ current and temperature data obtained between April 1995 and October 1996 from a moored array shows strong intraseasonal fluctuations in the southwestern Arabian Sea, an oceanic region where the Great Whirl (GW), a predominantly wind-generated, very energetic anticyclone, is present during the Southwest Monsoon. Fluctuation periods between 30 and 50 days, up to 100 days during some years, are observed in the 8-year altimetric dataset, mostly during late summer and fall. These fluctuations are largest in a 1000 km-wide region off the Somali, Omani and Yemeni coasts north of 5§N, suggesting a local generation mechanism. The in situ data at different moorings show strong and coherent fluctuations that are characterized by southwestward phase propagation and northward energy propagation. Their periods range from 30 to 60 days and increase steadily from July 1995 to January 1996. In the first stage, these periods are at and below the cut-off period of freely propagating, first baroclinic mode Rossby waves, but approach this theoretical limit later in the year. Instabilities of the flow in the transition region between the Southern Gyre and the GW are likely sources of these fluctuations.
Ashjian,C.J.,Smtih,S.L.,Flagg,C.N.,Idrisi,N.
Distribution, annual cycle, and vertical migration of acoustically derived biomass in the Arabian Sea during 1994-1995 Journal Article
In: Deep-Sea Research Part II, vol. 49, no. 299, pp. 2377-2402, 2002.
Abstract | BibTeX | Tags: acoustic, Arabian Sea, diel, Distribution, history, life history, migration, myctophids, Oceanic, Oman, predation, seasonal change, stocks, Upwelling, zooplankton
@article{,
title = {Distribution, annual cycle, and vertical migration of acoustically derived biomass in the Arabian Sea during 1994-1995},
author = {Ashjian,C.J.,Smtih,S.L.,Flagg,C.N.,Idrisi,N.},
year = {2002},
date = {2002-01-01},
journal = {Deep-Sea Research Part II},
volume = {49},
number = {299},
pages = {2377-2402},
abstract = {The distinguishing characteristic that sets the Arabian Sea apart from other oceanic regions is the regular oscillation of monsoonal atmospheric conditions that produces predictable periods of upwelling or convective mixing, with associated biological response, during the Southwest and Northeast monsoons, respectively. This oscillation is also evident in cycles of standing stocks of zooplankton and micronekton. The vertical distribution and spatial pattern of zooplankton and micronekton biomass were estimated using an acoustic Doppler current profiler along a 1000-km transect extending from the continental shelf of Oman to the central Arabian Sea during ten cruises on the R/V Thomas G. Thompson (November 1994-December 1995). The influence of the Southwest Monsoon, and accompanying upwelling and enhanced acoustically derived biomass, was the dominant feature in the spatial-temporal distributions of both zooplankton and micronekton near the Omani coast. The diel vertical migration of predators (myctophids, pelagic crabs), and the seasonal changes in the strength of this signal, was the most significant pattern observed in the vertical distribution of biomass and imparted a strong day-night signal to the integrated upper water-column biomass. Significant differences in the magnitude of integrated upper water-column biomass, both zooplankton (day) and migrator-zooplankton (night), were seen between inshore and offshore of the atmospheric Findlater Jet. A station located in the central Arabian Sea demonstrated seasonal changes in biomass over the year, despite being quite far from the influence of the monsoonal oscillations. Predation pressure was greater offshore of the Findlater Jet than in the region inshore of the Jet or in the central Arabian Sea. The pelagic community of the Arabian Sea may have evolved life history strategies to coincide with the predictable monsoonal cycle},
keywords = {acoustic, Arabian Sea, diel, Distribution, history, life history, migration, myctophids, Oceanic, Oman, predation, seasonal change, stocks, Upwelling, zooplankton},
pubstate = {published},
tppubtype = {article}
}
The distinguishing characteristic that sets the Arabian Sea apart from other oceanic regions is the regular oscillation of monsoonal atmospheric conditions that produces predictable periods of upwelling or convective mixing, with associated biological response, during the Southwest and Northeast monsoons, respectively. This oscillation is also evident in cycles of standing stocks of zooplankton and micronekton. The vertical distribution and spatial pattern of zooplankton and micronekton biomass were estimated using an acoustic Doppler current profiler along a 1000-km transect extending from the continental shelf of Oman to the central Arabian Sea during ten cruises on the R/V Thomas G. Thompson (November 1994-December 1995). The influence of the Southwest Monsoon, and accompanying upwelling and enhanced acoustically derived biomass, was the dominant feature in the spatial-temporal distributions of both zooplankton and micronekton near the Omani coast. The diel vertical migration of predators (myctophids, pelagic crabs), and the seasonal changes in the strength of this signal, was the most significant pattern observed in the vertical distribution of biomass and imparted a strong day-night signal to the integrated upper water-column biomass. Significant differences in the magnitude of integrated upper water-column biomass, both zooplankton (day) and migrator-zooplankton (night), were seen between inshore and offshore of the atmospheric Findlater Jet. A station located in the central Arabian Sea demonstrated seasonal changes in biomass over the year, despite being quite far from the influence of the monsoonal oscillations. Predation pressure was greater offshore of the Findlater Jet than in the region inshore of the Jet or in the central Arabian Sea. The pelagic community of the Arabian Sea may have evolved life history strategies to coincide with the predictable monsoonal cycle
Farrenkopf,A.M.,Luther III,G.W.
Iodine chemistry reflects productivity and denitrification in the Arabian Sea: evidence for flux of dissolved species from sediments of western India into the OMZ Journal Article
In: Deep-Sea Research Part II, vol. 49 , no. 91, pp. 2303-2318, 2002.
Abstract | BibTeX | Tags: Arabian Sea, Atlantic, Hawaii, India, Oceanic, oxygen minimum, productivity
@article{,
title = {Iodine chemistry reflects productivity and denitrification in the Arabian Sea: evidence for flux of dissolved species from sediments of western India into the OMZ},
author = {Farrenkopf,A.M.,Luther III,G.W.},
year = {2002},
date = {2002-01-01},
journal = {Deep-Sea Research Part II},
volume = {49 },
number = {91},
pages = {2303-2318},
abstract = {Dissolved iodine species and total iodine concentrations were measured in the Arabian Sea during the Spring Intermonsoon of 1995. Two separate regimes of iodine chemistry are highlighted in this study: (1) the well-oxygenated surface layer (WOSL) where iodide concentrations were in the range of 158-558 nM, and (2) the oxygen minimum zone (OMZ) where total iodine concentrations [primarily as iodide and in excess to the oceanic iodine/salinity ratio of ~13] varied from ~200 to 950 nM. Iodine data in the WOSL of the Arabian Sea are contrasted with data from the Bermuda Atlantic Time-series Station (BATS), the Hawaii Ocean Time-series Station ALOHA (HOT), VERTEX in the Pacific and the Black Sea. Total iodine concentrations in excess of 400nM were observed in eastern portions of the OMZ. The eastern portion of the basin has a permanent denitrification zone as well as high concentrations of dissolved Mn2+ (d- Mn2+) and iodide. While there is precedent for high values of iodide and total iodine in several other isolated basins, this is the first report of such values in open-ocean waters. Potential sources of excess total iodine to the OMZ include advection along isopycnals, from hydrothermal vents or margin sediments; atmospheric deposition; and remineralization of sinking particulate organic iodine (POI) associated with elevated productivity in surface waters. We estimate that only 3.6% of the excess total iodine can result from remineralization of sinking POI from the WOSL to the OMZ. Advection from margin sediments off of India is the most plausible source of iodine to the OMZ and contributes ~96% of the total excess iodine to the OMZ. I- is maintained as the dominant form of iodine via in situ reduction of iodate by bacteria.},
keywords = {Arabian Sea, Atlantic, Hawaii, India, Oceanic, oxygen minimum, productivity},
pubstate = {published},
tppubtype = {article}
}
Dissolved iodine species and total iodine concentrations were measured in the Arabian Sea during the Spring Intermonsoon of 1995. Two separate regimes of iodine chemistry are highlighted in this study: (1) the well-oxygenated surface layer (WOSL) where iodide concentrations were in the range of 158-558 nM, and (2) the oxygen minimum zone (OMZ) where total iodine concentrations [primarily as iodide and in excess to the oceanic iodine/salinity ratio of ~13] varied from ~200 to 950 nM. Iodine data in the WOSL of the Arabian Sea are contrasted with data from the Bermuda Atlantic Time-series Station (BATS), the Hawaii Ocean Time-series Station ALOHA (HOT), VERTEX in the Pacific and the Black Sea. Total iodine concentrations in excess of 400nM were observed in eastern portions of the OMZ. The eastern portion of the basin has a permanent denitrification zone as well as high concentrations of dissolved Mn2+ (d- Mn2+) and iodide. While there is precedent for high values of iodide and total iodine in several other isolated basins, this is the first report of such values in open-ocean waters. Potential sources of excess total iodine to the OMZ include advection along isopycnals, from hydrothermal vents or margin sediments; atmospheric deposition; and remineralization of sinking particulate organic iodine (POI) associated with elevated productivity in surface waters. We estimate that only 3.6% of the excess total iodine can result from remineralization of sinking POI from the WOSL to the OMZ. Advection from margin sediments off of India is the most plausible source of iodine to the OMZ and contributes ~96% of the total excess iodine to the OMZ. I- is maintained as the dominant form of iodine via in situ reduction of iodate by bacteria.
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.
Burkill,P.H.
Arabesque: An overview Journal Article
In: Deep-Sea Research Part II, vol. 46, no. 340, pp. 529-547, 1999.
Abstract | BibTeX | Tags: Arabian Sea, Gulf of Oman, length, Oceanic, oceanography, Oman, Upwelling
@article{,
title = {Arabesque: An overview},
author = {Burkill,P.H.},
year = {1999},
date = {1999-01-01},
journal = {Deep-Sea Research Part II},
volume = {46},
number = {340},
pages = {529-547},
abstract = {This special issue reports the results of ARABESQUE, a UK-led, international programme of upper-ocean biogeochemistry in the Arabian Sea region, conducted during two contrasting seasons. The seasons studied here were the waning of the southwest monsoon in August/September and the intermonsoon-northeast monsoon transition in November/December 1994. Biogeochemical studies were carried out along three transects in the Gulf of Oman and the Arabian Sea. the main ARABESQUE transect, 1590km in length, lay orthagonal to the southern Oman coast and spanned a range of conditions that encompassed coastal seasonal upwelling through to oceanic aseasonal oligotrophy of the central Arabian Sea. Surface mixed-layer hydrography, PAR, wind speed and direction fields and research results obtained during two seasonal studies are summarised in this paper which also serves and an introductory overview to ARABESQUE.},
keywords = {Arabian Sea, Gulf of Oman, length, Oceanic, oceanography, Oman, Upwelling},
pubstate = {published},
tppubtype = {article}
}
This special issue reports the results of ARABESQUE, a UK-led, international programme of upper-ocean biogeochemistry in the Arabian Sea region, conducted during two contrasting seasons. The seasons studied here were the waning of the southwest monsoon in August/September and the intermonsoon-northeast monsoon transition in November/December 1994. Biogeochemical studies were carried out along three transects in the Gulf of Oman and the Arabian Sea. the main ARABESQUE transect, 1590km in length, lay orthagonal to the southern Oman coast and spanned a range of conditions that encompassed coastal seasonal upwelling through to oceanic aseasonal oligotrophy of the central Arabian Sea. Surface mixed-layer hydrography, PAR, wind speed and direction fields and research results obtained during two seasonal studies are summarised in this paper which also serves and an introductory overview to ARABESQUE.
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.
Dennett,M.R.,Caron,D.A.,Murzov,S.A.,Polikarpov,I.G.,Gavrilova,N.A.,Georgieva,L.V.,Kuzmenko,L.V.
Abundance and biomass of nano- and microplankton during the 1995 Northeast Monsoon and Spring Intermonsoon in the Arabian Sea Journal Article
In: Deep-Sea Research Part II, vol. 46, no. 87, pp. 1691-1717, 1999.
Abstract | BibTeX | Tags: abundance, Arabian Sea, ecosystem, Oceanic, oxygen minimum, plankton
@article{,
title = {Abundance and biomass of nano- and microplankton during the 1995 Northeast Monsoon and Spring Intermonsoon in the Arabian Sea},
author = {Dennett,M.R.,Caron,D.A.,Murzov,S.A.,Polikarpov,I.G.,Gavrilova,N.A.,Georgieva,L.V.,Kuzmenko,L.V.},
year = {1999},
date = {1999-01-01},
journal = {Deep-Sea Research Part II},
volume = {46},
number = {87},
pages = {1691-1717},
abstract = {Phototrophic and heterotrophic nanoplankton (PNAN, HNAN; 2-20 æm protists) and microplankton (PMIC, HMIC; 20-200 æm protists and micrometazoa) are major components of the producer and consumer assemblages in oceanic plankton communities. Abundances and biomasses of these microorganisms were determined from samples collected along two transects during the Northeast Monsoon and Spring Intermonsoon process cruises of the US JGOFS Arabian Sea Program in 1995. Vertical profiles of these assemblages were strongly affected by the presence of a subsurface oxygen minimum layer. Abundances of all four assemblages decreased dramatically below the top of this layer. Depth-integrated (0-160 m) abundances and biomasses of nanoplankton and microplankton were of similar magnitude for most samples. Exceptions to this rule were primarily due to PMIC (mostly diatom) species which dominated phytoplankton assemblages at a few stations during each season. Depth-integrated biomasses for the combined nano- and microplankton averaged over all stations for each cruise were surprisingly similar for the Northeast Monsoon and Spring Intermonsoon seasons in this ecosystem (2.0 and 1.8 g C m-2 [170 and 150 m moles C m-2] for the two seasons, respectively). Nano- and microplankton biomass for these two time periods constituted a significant portion of the total amount of the particulate organic carbon (POC) in the water column. Summed over all stations, these assemblages constituted approximately 25-35% of the POC in the top 160 m of the northern Arabian Sea.},
keywords = {abundance, Arabian Sea, ecosystem, Oceanic, oxygen minimum, plankton},
pubstate = {published},
tppubtype = {article}
}
Phototrophic and heterotrophic nanoplankton (PNAN, HNAN; 2-20 æm protists) and microplankton (PMIC, HMIC; 20-200 æm protists and micrometazoa) are major components of the producer and consumer assemblages in oceanic plankton communities. Abundances and biomasses of these microorganisms were determined from samples collected along two transects during the Northeast Monsoon and Spring Intermonsoon process cruises of the US JGOFS Arabian Sea Program in 1995. Vertical profiles of these assemblages were strongly affected by the presence of a subsurface oxygen minimum layer. Abundances of all four assemblages decreased dramatically below the top of this layer. Depth-integrated (0-160 m) abundances and biomasses of nanoplankton and microplankton were of similar magnitude for most samples. Exceptions to this rule were primarily due to PMIC (mostly diatom) species which dominated phytoplankton assemblages at a few stations during each season. Depth-integrated biomasses for the combined nano- and microplankton averaged over all stations for each cruise were surprisingly similar for the Northeast Monsoon and Spring Intermonsoon seasons in this ecosystem (2.0 and 1.8 g C m-2 [170 and 150 m moles C m-2] for the two seasons, respectively). Nano- and microplankton biomass for these two time periods constituted a significant portion of the total amount of the particulate organic carbon (POC) in the water column. Summed over all stations, these assemblages constituted approximately 25-35% of the POC in the top 160 m of the northern Arabian Sea.
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.
Riemann,L.,Steward,G.F.,Fandino,L.B.,Campbell,L.,Landry,M.R.,Azam,F.
Bacterial community composition during two consecutive NE Monsoon periods in the Arabian Sea studied by denaturing gradient gel electrophoresis (DGGE) of rRNA genes Journal Article
In: Deep-Sea Research Part II, vol. 46, no. 205, pp. 1791-1811, 1999.
Abstract | BibTeX | Tags: Arabian Sea, depth, DNA, dominance, Oceanic, PCR
@article{,
title = {Bacterial community composition during two consecutive NE Monsoon periods in the Arabian Sea studied by denaturing gradient gel electrophoresis (DGGE) of rRNA genes},
author = {Riemann,L.,Steward,G.F.,Fandino,L.B.,Campbell,L.,Landry,M.R.,Azam,F.},
year = {1999},
date = {1999-01-01},
journal = {Deep-Sea Research Part II},
volume = {46},
number = {205},
pages = {1791-1811},
abstract = {Horizontal and vertical variations in bacterial community composition were examined in samples collected during two Joint Global Ocean Flux Study (JGOFS) Arabian Sea cruises in 1995. The cruises, 11 months apart, took place during two consecutive NE Monsoon periods (January and December). Bacteria were harvested by filtration from samples collected in the mixed layer, mid-water, and deep sea at stations across the study area. Total bacterial community genomic DNA was analyzed by PCR amplification of 16S rRNA gene fragments, followed by denaturing gradient gel electrophoresis (DGGE). In total, 20 DGGE bands reflecting unique or varying phylotypes were excised, cloned and sequenced. Amplicons were dominated by bacterial groups commonly found in oceanic waters (e.g., the SAR11 cluster of a-Proteobacteria and cyanobacteria), but surprisingly none of the sequenced amplicons were related to c-Proteobacteria or to members of the Cytophaga-Flavobacter-Bacteroides phylum. Amplicons related to magnetotactic bacteria were found for the first time in pelagic oceanic waters. The DGGE banding patterns revealed a dominance of ÷ 15 distinguishable amplicons in all samples. In the mixed layer the bacterial community was dominated by the same ÷ 15 phylotypes at all stations, but unique phylotypes were found with increasing depth. Except for cyanobacteria, comparison of the bacterial community composition in surface waters from January and December 1995 showed only minor differences, despite significant differences in environmental parameters. These data suggest a horizontal homogeneity and some degree of seasonal predictability of bacterial community composition in the Arabian Sea.},
keywords = {Arabian Sea, depth, DNA, dominance, Oceanic, PCR},
pubstate = {published},
tppubtype = {article}
}
Horizontal and vertical variations in bacterial community composition were examined in samples collected during two Joint Global Ocean Flux Study (JGOFS) Arabian Sea cruises in 1995. The cruises, 11 months apart, took place during two consecutive NE Monsoon periods (January and December). Bacteria were harvested by filtration from samples collected in the mixed layer, mid-water, and deep sea at stations across the study area. Total bacterial community genomic DNA was analyzed by PCR amplification of 16S rRNA gene fragments, followed by denaturing gradient gel electrophoresis (DGGE). In total, 20 DGGE bands reflecting unique or varying phylotypes were excised, cloned and sequenced. Amplicons were dominated by bacterial groups commonly found in oceanic waters (e.g., the SAR11 cluster of a-Proteobacteria and cyanobacteria), but surprisingly none of the sequenced amplicons were related to c-Proteobacteria or to members of the Cytophaga-Flavobacter-Bacteroides phylum. Amplicons related to magnetotactic bacteria were found for the first time in pelagic oceanic waters. The DGGE banding patterns revealed a dominance of ÷ 15 distinguishable amplicons in all samples. In the mixed layer the bacterial community was dominated by the same ÷ 15 phylotypes at all stations, but unique phylotypes were found with increasing depth. Except for cyanobacteria, comparison of the bacterial community composition in surface waters from January and December 1995 showed only minor differences, despite significant differences in environmental parameters. These data suggest a horizontal homogeneity and some degree of seasonal predictability of bacterial community composition in the Arabian Sea.
Tindale,N.W.,Pease,P.P.
Aerosols over the Arabian Sea: Atmospheric transport pathways and concentrations of dust and sea salt Journal Article
In: Deep-Sea Research Part II, vol. 46 , no. 485, pp. 1577-1595, 1999.
Abstract | BibTeX | Tags: Arabian Sea, Gulf of Oman, Oceanic, Oman
@article{,
title = {Aerosols over the Arabian Sea: Atmospheric transport pathways and concentrations of dust and sea salt},
author = {Tindale,N.W.,Pease,P.P.},
year = {1999},
date = {1999-01-01},
journal = {Deep-Sea Research Part II},
volume = {46 },
number = {485},
pages = {1577-1595},
abstract = {This paper provides an overview of dust transport pathways and concentrations over the Arabian Sea during 1995. Results indicate that the transport and input of dust to the region is complex, being affected by both temporally and spatially important processes. Highest values of dust were found off the Omani coast and in the entrance to the Gulf of Oman. Dust levels were generally lower in summer than the other seasons, although still relatively high compared to other oceanic regions. The Findlater jet, rather than acting as a source of dust from Africa, appears to block the direct transport of dust to the open Arabian Sea from desert dust source regions in the Middle East and Iran/Pakistan. Dust transport aloft, above the jet, rather than at the surface, may be more important during summer. In an opposite pattern to dust, sea salt levels were exceedingly high during the summer monsoon, presumably due to the sustained strong surface winds. The high sea salt aerosols during the summer months may be impacting on the strong aerosol reflectance and absorbance signals over the Arabian Sea that are detected by satellite each year},
keywords = {Arabian Sea, Gulf of Oman, Oceanic, Oman},
pubstate = {published},
tppubtype = {article}
}
This paper provides an overview of dust transport pathways and concentrations over the Arabian Sea during 1995. Results indicate that the transport and input of dust to the region is complex, being affected by both temporally and spatially important processes. Highest values of dust were found off the Omani coast and in the entrance to the Gulf of Oman. Dust levels were generally lower in summer than the other seasons, although still relatively high compared to other oceanic regions. The Findlater jet, rather than acting as a source of dust from Africa, appears to block the direct transport of dust to the open Arabian Sea from desert dust source regions in the Middle East and Iran/Pakistan. Dust transport aloft, above the jet, rather than at the surface, may be more important during summer. In an opposite pattern to dust, sea salt levels were exceedingly high during the summer monsoon, presumably due to the sustained strong surface winds. The high sea salt aerosols during the summer months may be impacting on the strong aerosol reflectance and absorbance signals over the Arabian Sea that are detected by satellite each year
De Silva,P.H.D.H..
Cetaceans (whales, dolphins and porpoises) recorded off Sri Lanka, India, from the Arabian Sea and Gulf, Gulf of Aden and from the Red Sea Journal Article
In: Journal of the Bombay Natural History Society, vol. 84 , no. 357, pp. 505-525, 1987.
Abstract | BibTeX | Tags: Antarctic, Arabia, Arabian Gulf, Arabian Sea, behaviour, Blue whale, cetacea, cetacean, cetaceans, Delphinus tropicalis, dolphin, dolphins, fin whale, Gulf of Aden, Gulf of Oman, Humpback Whale, India, Indian Ocean, mammals, marine, migration, Neophocaena phocaenoides, Oceanic, Oman, Pakistan, Porpoise, Red Sea, sanctuaries, skull, Sri Lanka, stranding, Strandings, survey, whale, whales
@article{,
title = {Cetaceans (whales, dolphins and porpoises) recorded off Sri Lanka, India, from the Arabian Sea and Gulf, Gulf of Aden and from the Red Sea },
author = {De Silva,P.H.D.H..},
year = {1987},
date = {1987-01-01},
journal = {Journal of the Bombay Natural History Society},
volume = {84 },
number = {357},
pages = {505-525},
abstract = {Cetacea is a highly specialized oceanic group of mammals with several of its species undertaking long migrations, often exceeding thousand miles during a single journey. During these migrations from cold polar and subpolar seas to warmer tropical and subtropical waters and their return to polar seas in summer both individual and mass strandings have very often occurred in many parts of the world, including Sri Lanka, India and the Arabian Gulf. The Cetacean records dealt with in this paper are of countries which lie at the extreme southern margin of the vast land mass of Asia with no land other than a few islands and vast stretches of the Indian Ocean between them and the Antarctica. Sri Lanka, in view of her geographic position at the southern extremity of this vast land mass (5ø 55' and 9§51'N latitude and 79§41' and 81§ 54' E longitude) has become a passing point in the movement of oceanic species including the larger whales. It has been suggested by Deraniyagala (1945, 1960b) that the movement of larger species towards the tropics from the southern temperate zone is partly associated with the periodic influx of Antarctic water toward the tropics. It is however, now fairly established that several larger species such as the Blue whale, the Fin whale and the Humpback whale show a regular migratory cycle. The majority of strandings recorded in this paper deal with individual strandings. Nevertheless there have been instances of both mass stranding and of apparent suicidal behaviour. This paper deals with 30 Cetacean species from the region. Of these records, records from Sri Lanka total 23 species, from India 24 species, from Pakistan 17 species, from the Gulf of Oman 10 species, from the Arabian Gulf 9 species, from the Gulf of Aden 6 species and from the Red Sea 7 species. Reference is also made to a skull of Delphinus tropicalis van Bree in the Colombo Museum (Skull No. 15 B) which appears to be its first record from Sri Lanka. Mention is also made of a specimen of Neophocaena phocaenoides (G. Cuvier) collected from the Wadge Bank by the Smithsonian Carangid Survey Team in March 1970 and of two incomplete skeletons of Balaenoptera physalus (Linn‚) (probably mother and calf) in the Zoological Museum, King Saud University, Riyadh, Saudi Arabia. All these specimens were identified by me. It is evident from this study that our present knowledge of the Cetacean fauna of the Indian Ocean is far from complete and that much could be accomplished by scientific institutions in the countries in the region by diligently maintaining proper records of sightings and strandings (with photographs) and by undertaking joint study surveys. It is gratifying to note that Sri Lanka, in recent years has been making much headway in this regard. During the last few years the Tulip Expedition led by Dr. Hal Whitehead has been studying the larger whales, especially the larger whales off the east coast and Dr. Stephen Leatherwood Of Hubbs-Sea World Research Institute (Marine Science), San Diego, California has recently published (1985) a summary of available information on the Cetacea of the Indian Ocean Cetacean Sanctuary on behalf of the National Aquatic Resources Agency for Sri Lanka. It is hoped that the present paper will further stimulate interest among the scientific institutions in the region and help to increase our knowledge of a group of remarkable animals at least as far as the species which inhabit and visit our seas.has become a passing point in the movement of oceanic species including the larger whales. It has been suggested by Deraniyagala (1945, 1960b) that the movement of larger species towards the tropics from the southern temperate zone is partly associated with the periodic influx of Antarctic water toward the tropics. It is however, now fairly established that several larger species such as the Blue whale, the Fin whale and the Humpback whale show a regular migratory cycle. The majority of strandings recorded in this paper deal with individual strandings. Nevertheless there have been instances of both mass stranding and of apparent suicidal behaviour. This paper deals with 30 Cetacean species from the region. Of these records, records from Sri Lanka total 23 species, from India 24 species, from Pakistan 17 species, from the Gulf of Oman 10 species, from the Arabian Gulf 9 species, from the Gulf of Aden 6 species and from the Red Sea 7 species. Reference is also made to a skull of Delphinus tropicalis van Bree in the Colombo Museum (Skull No. 15 B) which appears to be its first record from Sri Lanka. Mention is also made of a specimen of Neophocaena phocaenoides (G. Cuvier) collected from the Wadge Bank by the Smithsonian Carangid Survey Team in March 1970 and of two incomplete skeletons of Balaenoptera physalus (Linn‚) (probably mother and calf) in the Zoological Museum, King Saud University, Riyadh, Saudi Arabia. All these specimens were identified by me. It is evident from this study that our present knowledge of the Cetacean fauna of the Indian Ocean is far from complete and that much could be accomplished by scientific institutions in the countries in the region by diligently maintaining proper records of sightings and strandings (with photographs) and by undertaking joint study surveys. It is gratifying to note that Sri Lanka, in recent years has been making much headway in this regard. During the last few years the Tulip Expedition led by Dr. Hal Whitehead has been studying the larger whales, especially the larger whales off the east coast and Dr. Stephen Leatherwood Of Hubbs-Sea World Research Institute (Marine Science), San Diego, California has recently published (1985) a summary of available information on the Cetacea of the Indian Ocean Cetacean Sanctuary on behalf of the National Aquatic Resources Agency for Sri Lanka. It is hoped that the present paper will further stimulate interest among the scientific institutions in the region and help to increase our knowledge of a group of remarkable animals at least as far as the species which inhabit and visit our seas. A key to the identification of the species recorded from the region is given in Appendix. },
keywords = {Antarctic, Arabia, Arabian Gulf, Arabian Sea, behaviour, Blue whale, cetacea, cetacean, cetaceans, Delphinus tropicalis, dolphin, dolphins, fin whale, Gulf of Aden, Gulf of Oman, Humpback Whale, India, Indian Ocean, mammals, marine, migration, Neophocaena phocaenoides, Oceanic, Oman, Pakistan, Porpoise, Red Sea, sanctuaries, skull, Sri Lanka, stranding, Strandings, survey, whale, whales},
pubstate = {published},
tppubtype = {article}
}
Cetacea is a highly specialized oceanic group of mammals with several of its species undertaking long migrations, often exceeding thousand miles during a single journey. During these migrations from cold polar and subpolar seas to warmer tropical and subtropical waters and their return to polar seas in summer both individual and mass strandings have very often occurred in many parts of the world, including Sri Lanka, India and the Arabian Gulf. The Cetacean records dealt with in this paper are of countries which lie at the extreme southern margin of the vast land mass of Asia with no land other than a few islands and vast stretches of the Indian Ocean between them and the Antarctica. Sri Lanka, in view of her geographic position at the southern extremity of this vast land mass (5ø 55' and 9§51'N latitude and 79§41' and 81§ 54' E longitude) has become a passing point in the movement of oceanic species including the larger whales. It has been suggested by Deraniyagala (1945, 1960b) that the movement of larger species towards the tropics from the southern temperate zone is partly associated with the periodic influx of Antarctic water toward the tropics. It is however, now fairly established that several larger species such as the Blue whale, the Fin whale and the Humpback whale show a regular migratory cycle. The majority of strandings recorded in this paper deal with individual strandings. Nevertheless there have been instances of both mass stranding and of apparent suicidal behaviour. This paper deals with 30 Cetacean species from the region. Of these records, records from Sri Lanka total 23 species, from India 24 species, from Pakistan 17 species, from the Gulf of Oman 10 species, from the Arabian Gulf 9 species, from the Gulf of Aden 6 species and from the Red Sea 7 species. Reference is also made to a skull of Delphinus tropicalis van Bree in the Colombo Museum (Skull No. 15 B) which appears to be its first record from Sri Lanka. Mention is also made of a specimen of Neophocaena phocaenoides (G. Cuvier) collected from the Wadge Bank by the Smithsonian Carangid Survey Team in March 1970 and of two incomplete skeletons of Balaenoptera physalus (Linn‚) (probably mother and calf) in the Zoological Museum, King Saud University, Riyadh, Saudi Arabia. All these specimens were identified by me. It is evident from this study that our present knowledge of the Cetacean fauna of the Indian Ocean is far from complete and that much could be accomplished by scientific institutions in the countries in the region by diligently maintaining proper records of sightings and strandings (with photographs) and by undertaking joint study surveys. It is gratifying to note that Sri Lanka, in recent years has been making much headway in this regard. During the last few years the Tulip Expedition led by Dr. Hal Whitehead has been studying the larger whales, especially the larger whales off the east coast and Dr. Stephen Leatherwood Of Hubbs-Sea World Research Institute (Marine Science), San Diego, California has recently published (1985) a summary of available information on the Cetacea of the Indian Ocean Cetacean Sanctuary on behalf of the National Aquatic Resources Agency for Sri Lanka. It is hoped that the present paper will further stimulate interest among the scientific institutions in the region and help to increase our knowledge of a group of remarkable animals at least as far as the species which inhabit and visit our seas.has become a passing point in the movement of oceanic species including the larger whales. It has been suggested by Deraniyagala (1945, 1960b) that the movement of larger species towards the tropics from the southern temperate zone is partly associated with the periodic influx of Antarctic water toward the tropics. It is however, now fairly established that several larger species such as the Blue whale, the Fin whale and the Humpback whale show a regular migratory cycle. The majority of strandings recorded in this paper deal with individual strandings. Nevertheless there have been instances of both mass stranding and of apparent suicidal behaviour. This paper deals with 30 Cetacean species from the region. Of these records, records from Sri Lanka total 23 species, from India 24 species, from Pakistan 17 species, from the Gulf of Oman 10 species, from the Arabian Gulf 9 species, from the Gulf of Aden 6 species and from the Red Sea 7 species. Reference is also made to a skull of Delphinus tropicalis van Bree in the Colombo Museum (Skull No. 15 B) which appears to be its first record from Sri Lanka. Mention is also made of a specimen of Neophocaena phocaenoides (G. Cuvier) collected from the Wadge Bank by the Smithsonian Carangid Survey Team in March 1970 and of two incomplete skeletons of Balaenoptera physalus (Linn‚) (probably mother and calf) in the Zoological Museum, King Saud University, Riyadh, Saudi Arabia. All these specimens were identified by me. It is evident from this study that our present knowledge of the Cetacean fauna of the Indian Ocean is far from complete and that much could be accomplished by scientific institutions in the countries in the region by diligently maintaining proper records of sightings and strandings (with photographs) and by undertaking joint study surveys. It is gratifying to note that Sri Lanka, in recent years has been making much headway in this regard. During the last few years the Tulip Expedition led by Dr. Hal Whitehead has been studying the larger whales, especially the larger whales off the east coast and Dr. Stephen Leatherwood Of Hubbs-Sea World Research Institute (Marine Science), San Diego, California has recently published (1985) a summary of available information on the Cetacea of the Indian Ocean Cetacean Sanctuary on behalf of the National Aquatic Resources Agency for Sri Lanka. It is hoped that the present paper will further stimulate interest among the scientific institutions in the region and help to increase our knowledge of a group of remarkable animals at least as far as the species which inhabit and visit our seas. A key to the identification of the species recorded from the region is given in Appendix.
Silas,E.G.,Matthew,K.J.
Spatial distribution of Euphausiacea (Crustacea) in the southeastern Arabian Sea Journal Article
In: Journal of the Marine Biological Association of India, vol. 28, no. 230, pp. 1-21, 1986.
Abstract | BibTeX | Tags: abundance, Arabian Sea, Distribution, Euphausiid, India, Oceanic, zooplankton
@article{,
title = {Spatial distribution of Euphausiacea (Crustacea) in the southeastern Arabian Sea},
author = {Silas,E.G.,Matthew,K.J.},
year = {1986},
date = {1986-01-01},
journal = {Journal of the Marine Biological Association of India},
volume = {28},
number = {230},
pages = {1-21},
abstract = {Spatial distribution of euphausiids of the southeastern Arabian Sea (west coast of India including the Lakshadweep Sea) was studied. The Arabian Sea and the Bay of Bengal, closed at their northern parts, present special hydrographical features which influence the distribution and abundance of zooplankton in these areas. Here the l0 degree N latitude is thought to be an effective barrier against he penetration of several oceanic species of euphausiids northwards. This is because of the significant changes in the water quality of N of 10 degree N being influenced by the discharge from major river systems of the Indian sub-continent. The species Thysanopoda monacantha, T. tricuspidata and Stylocheiron maximum, which were believed to be restricted to areas south of 10 degrees N are distributed even further northwards.},
keywords = {abundance, Arabian Sea, Distribution, Euphausiid, India, Oceanic, zooplankton},
pubstate = {published},
tppubtype = {article}
}
Spatial distribution of euphausiids of the southeastern Arabian Sea (west coast of India including the Lakshadweep Sea) was studied. The Arabian Sea and the Bay of Bengal, closed at their northern parts, present special hydrographical features which influence the distribution and abundance of zooplankton in these areas. Here the l0 degree N latitude is thought to be an effective barrier against he penetration of several oceanic species of euphausiids northwards. This is because of the significant changes in the water quality of N of 10 degree N being influenced by the discharge from major river systems of the Indian sub-continent. The species Thysanopoda monacantha, T. tricuspidata and Stylocheiron maximum, which were believed to be restricted to areas south of 10 degrees N are distributed even further northwards.