@article{,

title = {Surface circulation and upwelling patterns around Sri Lanka},

author = {de Vos, A.,Pattiaratchi, C. B.,Wijeratne, E. M. S.},

url = {https://www.biogeosciences.net/11/5909/2014/},

issn = {1726-4189},

year  = {2014},

date = {2014-01-01},

journal = {Biogeosciences},

volume = {11},

number = {85},

pages = {5909-5930},

publisher = {Copernicus Publications},

abstract = {Sri Lanka occupies a unique location within the equatorial belt in the northern Indian Ocean, with the Arabian Sea on its western side and the Bay of Bengal on its eastern side, and experiences bi-annually reversing monsoon winds. Aggregations of blue whale (Balaenoptera musculus) have been observed along the southern coast of Sri Lanka during the northeast (NE) monsoon, when satellite imagery indicates lower productivity in the surface waters. This study explored elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and numerical simulations using the Regional Ocean Modelling System (ROMS). The model was run for 3 years to examine the seasonal and shorter-term (~10 days) variability. The results reproduced correctly the reversing current system, between the Equator and Sri Lanka, in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the southwest (SW) monsoon transporting 11.5 Sv (mean over 2010–2012) and the westward flowing Northeast Monsoon Current (NMC) transporting 9.6 Sv during the NE monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the southern coast. During the SW monsoon, the island deflects the eastward flowing SMC southward, whilst along the eastern coast, the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the southern coast, resulting from southward flow converging along the southern coast and subsequent divergence associated with the offshore transport of water. Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and hence the upwelling centre was dependent on the relative strengths of wind-driven flow along the eastern and western coasts: during the SW (NE) monsoon, the flow along the western (eastern) coast was stronger, migrating the upwelling centre to the east (west).},

keywords = {currents, Indian Ocean, oceanography, productivity, remote sensing, Sri Lanka},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {The Whale Pump: Marine Mammals Enhance Primary Productivity in a Coastal Basin},

author = {Roman, J,McCarthy, JJ,Roopnarine, P},

issn = {1932-6203},

year  = {2010},

date = {2010-01-01},

journal = {PLoS ONE},

volume = {5},

number = {449},

pages = {47-123},

publisher = {Public Library of Science San Francisco, USA},

abstract = {It is well known that microbes, zooplankton, and fish are important sources of recycled nitrogen in coastal waters, yet

marine mammals have largely been ignored or dismissed in this cycle. Using field measurements and population data, we

find that marine mammals can enhance primary productivity in their feeding areas by concentrating nitrogen near the

surface through the release of flocculent fecal plumes. Whales and seals may be responsible for replenishing 2.36104 metric

tons of N per year in the Gulf of Maine’s euphotic zone, more than the input of all rivers combined. This upward ‘‘whale

pump’’ played a much larger role before commercial harvest, when marine mammal recycling of nitrogen was likely more

than three times atmospheric N input. Even with reduced populations, marine mammals provide an important ecosystem

service by sustaining productivity in regions where they occur in high densities.},

keywords = {feeding, nitrogen, productivity, whales},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Warming of the Eurasian landmass is making the Arabian Sea more productive},

author = {Goes, Joaquim I,Thoppil, Prasad G,do R Gomes, Helga,Fasullo, John T},

issn = {0036-8075},

year  = {2005},

date = {2005-01-01},

journal = {Science},

volume = {308},

number = {379},

pages = {545-547},

abstract = {The recent trend of declining winter and spring snow cover over Eurasia is

causing a land-ocean thermal gradient that is particularly favorable to stronger

southwest (summer) monsoon winds. Since 1997, sea surface winds have been

strengthening over the western Arabian Sea. This escalation in the intensity of

summer monsoon winds, accompanied by enhanced upwelling and an increase

of more than 350% in average summertime phytoplankton biomass along the

coast and over 300% offshore, raises the possibility that the current warming

trend of the Eurasian landmass is making the Arabian Sea more productive.},

keywords = {Arabian Sea, Climate change, monsoon, Oman, productivity, Upwelling},

pubstate = {published},

tppubtype = {article}

}

@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}

}

@article{,

title = {Primary productivity and its regulation in the Arabian Sea during 1995},

author = {Barber,R.T.,Marra,J.,Bidigare,R.C.,Codispoti,L.A.,Halpern,D.,Johnson,Z.,Latasa,M.,Goericke,R.,Smith,S.L.},

year  = {2001},

date = {2001-01-01},

journal = {Deep-Sea Research Part II},

volume = {48},

number = {323},

pages = {1127-1172},

abstract = {The annual cycle of monsoon-driven variability in primary productivity was studied in 1995 during the Arabian Sea Expedition as part of the United States Joint Global Ocean Flux Studies (US JGOFS). This paper describes the seasonal progression of productivity and its regulation on a section which ran from the coast of Oman to about 1000km offshore in the centralArabian Sea at 65§E. During the SW Monsoon (June-mid-September), the coolest water and highest nutrient concentrations were close to the coast, although they extended offshore to about 800 km; during the January NE Monsoon, deep convective mixing provided nutrients to the mixed layer in the region 400 - 1000km o!shore. As expected, the SW Monsoon was the most productive season (123ñ9mmolC m-2d-1) along the southern US JGOFS section from the coast to 1000km offshore, but productivity in the NE Monsoon was surprisingly high (112ñ7mmol C m-2d-1). There was no onshore/offshore gradient in primary productivity from 150 to 1000km o! the Omani coast in 1995, and there was no evidence of light limitation of either primary productivity or photosynthetic performance (PBopt) from deep convective mixing during the NE Monsoon, deep wind mixing during the SW Monsoon or offshore Ekman downwelling during the SW Monsoon. Productivity during the Spring Intermonsoon (86ñ6mmolC m-2d-1) was much higher than in oligotrophic regions such as the tropical Pacific Ocean (29ñ2 mmolC m-2 d-1) or the North Pacific gyre region (32ñ8 mmolC m-2 d-1). The 1995 annual mean productivity (111ñ11mmolC m-2 d-1) along this section from the Omani coast to the central Arabian Sea was about equal to the spring bloom maximum (107ñ23mmolC m-2 d-1) during the 1989 North Atlantic Bloom Experiment (NABE) and the equatorial, 1§N-1§S wave guide maximum (95ñ6mmolC m-2 d-1) in the Pacific Ocean during the 1992 EqPac study. The 1995 SW Monsoon primary productivity was similar to the mean value observed in the same region in 1994 by the Arabesque Expedition (127ñ14mmolC m-2 d-1) and in 1964 by the ANTON BRUUN Expedition (115ñ27 mmol C m-2 d-1). During the 1995 SW Monsoon, strong, narrow and meandering current filaments extended from the region of coastal upwelling to about 700km offshore; these filaments had levels of biomass, primary productivity, chlorophyll-specific productivity and diatom abundance that were elevated relative to other locations during the SW Monsoon. The SW Monsoon was the most productive period, but SW Monsoon primary productivity values were lower than predicted because effcient grazing by mesozooplankton kept diatoms from accumulating the biomass necessary for achieving the high levels of primary productivity characteristic of other coastal upwelling regions. The high rates of chlorophyll-specific productivity (PBopt>10mmolC mg Chl-1 d-1) observed in the 1995 SW Monsoon, together with the observed dust flux and iron concentrations, indicate that the Arabian Sea was more iron replete than the equatorial Pacific Ocean or the Southern Ocean },

keywords = {abundance, Arabian Sea, Atlantic, location, North Atlantic, Oman, Pacific Ocean, performance, productivity, Upwelling},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Heterotrophic bacterioplankton in the Arabian Sea: Basinwide response to year-round high primary productivity},

author = {Ducklow,H.W.,Smith,D.C.,Campbell,L.,Landry,M.R.,Quinby,H.L.,Steward,G.F.,Azam,F.},

year  = {2001},

date = {2001-01-01},

journal = {Deep-Sea Research Part II},

volume = {48},

number = {90},

pages = {1303-1323},

abstract = {Heterotrophic bacterial abundance and productivity were measured during five and four cruises, respectively, in the northwest Arabian Sea as part of the US JGOFS Process Study, which provided a new view of seasonal bacterial dynamics in that part of the basin influenced by monsoonal forcing. In this paper, surface layer data are used to address two questions concerning the influence of the monsoon cycle on bacterial dynamics: (1) Is there a bacterial bloom in the SW Monsoon? and (2) Is bacterial production low during the oligotrophic Spring Intermonsoon? An extensive comparison of epifluorescence microscopy and flow cytometry, unprecedented at this scale, detected essentially the same heterotrophic bacterial populations and distributions, with some between-cruise di!erences. Use of the two methods allowed us to extend our observations in space and time. Bacterial productivity, both in the surface layer and integrated over the euphotic zone, was elevated less than 2-fold during the Southwest Monsoon. Levels of bacterial abundance and production were low during the Northeast Monsoon, then increased in March during the Spring Intermonsoon. There was some stimulation of abundance or production inshore in response to coastal upwelling. In general, the basin was enriched in bacterial biomass >5 ' 108  cells l-1 throughout the year, relative to other tropical regimes, presumably in response to overall high PP and DOC levels. Seasonally uniform DOC levels may be regulated in part by intense bacterial utilization rates, but also reflect seasonal consistency in PP.},

keywords = {abundance, Arabian Sea, Distribution, population, populations, productivity, Upwelling},

pubstate = {published},

tppubtype = {article}

}

@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}

}

@article{,

title = {Nitrogen production in the northern Arabian Sea during the Spring Intermonsoon and Southwest Monsoon seasons},

author = {Sambrotto,R.N.},

year  = {2001},

date = {2001-01-01},

journal = {Deep-Sea Research Part II},

volume = {48},

number = {470},

pages = {1173-1198},

abstract = {Planktonic nitrogen productivity and regeneration were measured with 15NO3, 15NH4 and 15N-urea tracers during the Spring Intermonsoon (SI) and Southwest Monsoon (SWM) seasons in the northern Arabian Sea from the Omani coast southeast to 10§N. On an areal basis, new (nitrate) productivity and the nitrogen f-ratio varied from 0.1 to 13 mmol m-2 d-1 and 0.03 to 0.4, respectively. Including urea in total nitrogen uptake lowered the f-ratio by 29% on average for individual samples, and during the SI was most important in offshore regions. The lowest nitrate productivity rates also were measured in offshore regions during the SI, where low, but detectable, nitrate levels limited uptake. The onset of the SWM was associated with an order of magnitude increase in nitrate uptake seaward of the Findlater Jet as compared to the SI. Apparently, the positive effect of the increased availability of nitrate and the Ekman transport of established phytoplankton populations to the region more than offset the degraded light conditions caused by the deep (>80 m) mixed layers. Despite the increases in offshore nitrate uptake, both a budget of surface particulate material and 234Th POC flux estimates indicated that the mid- SWM reduced the efficiency of material export from surface waters and disrupted the linkage between new production and export that was evident in the SI. In the mid-SWM, new production mainly accumulated in deeply mixed surface waters offshore, and may be responsible for the well documented lag between the onset of the SWM and export. In the coastal upwelling region, new production rates were significantly greater during the SWM only near filaments of coastal water advected offshore. Ammonium regeneration rates and concentrations increased significantly in coastal regions during the SWM, and nitrification likely was a significant sink for some of the ammonium produced there. The transport of some of the remainder of this reduced nitrogen offshore would fuel nitrogen production without having an impact on local respiration. This is one of several factors that may confound the comparison of new and net production in coastal regions during the early SWM.  },

keywords = {Arabian Sea, budget, impact, population, populations, productivity, respiration, Upwelling},

pubstate = {published},

tppubtype = {article}

}

@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}

}

@article{,

title = {Annual biomarker record for export production in the central Arabian Sea},

author = {Prahl,F.G.,Dymond,J.,Sparrow,M.A.},

year  = {2000},

date = {2000-01-01},

journal = {Deep-Sea Research Part II},

volume = {47},

number = {200},

pages = {1581-1604},

abstract = {The record for plankton biomarkers in sediment trap samples from a one-year experiment in the central Arabian Sea (AS4: 15§59'N 61§30'E) shows variations that reflect changing biological conditions in surface waters. Particulate fluxes of C37-39 alkenones, highly branched C25 isoprenoids (HBI), dinosterol, nC28 12-hydroxy fatty acid, 24-ethylcholesterol, and C30-34 series of pentacyclic triterpanols all displayed distinct maxima at the start and stop of the Northeast (NE) and Southwest (SW) Monsoons. Surface mixing conditions changed rapidly at these times, altering light and nutrient availability, thereby triggering these biomarker signals of export production. Temporal offsets noted in individual biomarker concentrations (per g total organic carbon) at the start of the SW Monsoon suggest succession occurs in the phytoplankton community contributing to organic matter export. Comparable offsets were neither apparent at the start of the less dynamic NE Monsoon nor at the end of the NE or SW Monsoons. Broad concentration maxima for HBI also were observed at the beginning and end of the time-series during the relatively quiescent Fall Intermonsoon period when such features were conspicuously absent for other biomarkers. HBI are reputed biomarkers of Rhizoselenia and Haslea spp., two recognized dominants of diatom biomass in the Arabian Sea. These peaks in biomarker concentration could reflect either changes in the relative proportion of specific organisms that contribute to the upper ocean productivity or enhanced preservation of the biomarkers during times of high export production. In either case, the biomarker record in sediment traps reflects important changes in the biological condition of the upper ocean. All biomarkers except HBI were measurable in surface sediments deposited beneath the trap site. Comparison with concentrations in average sediment trap particles showed each was sensitive to significant ( ~ 99%) degradation, displaying depletion factors relative to TOC of ò4. Clearly, consequences of such high levels of early diagenetic recycling must be considered carefully when conclusions about changes in export production from surface waters in past oceans are drawn from stratigraphic analysis of biomarkers in marine sediments.  },

keywords = {Arabian Sea, depletion, marine, plankton, productivity, trap},

pubstate = {published},

tppubtype = {article}

}

@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}

}

@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}

}

@article{,

title = {Nitrogen dynamics during the Arabian Sea Northeast Monsoon},

author = {McCarthy,J.J.,Garside,C.,Nevins,J.L.},

year  = {1999},

date = {1999-01-01},

journal = {Deep-Sea Research Part II},

volume = {46},

number = {151},

pages = {1623-1664},

abstract = {This investigation focused on the weaker and less well understood of the two Arabian Sea monsoonal wind phases, the NE Monsoon, which persists for 3-4 months in the October to February period. Historically, this period has been characterized as a time of very low nutrient availability and low biological production. As part of the US JGOFS Arabian Sea Process Study, 17 stations were sampled on a cruise in January 1995 (late NE Monsoon) and, 15 stations were sampled on a cruise in November 1995 (early NE Monsoon). Only the southern most stations (10§ and 12§N) and one shallow coastal station were as nutrient-depleted as had been expected from the few relevant prior studies in this region. Experiments were conducted to ascertain the relative importance of different nitrogenous nutrients and the sufficiency of local regeneration processes in supplying nitrogenous nutrients utilized in primary production.  Except for the southern oligotrophic stations, the euphotic zone concentrations of NO3- were typically 5-10-fold greater than those of NO2- and NH4+. There was considerable variation (20-40-fold) in nutrient concentration both within and between the two sections on each cruise.  All nitrogenous nutrients were more abundant (2-4-fold) later in the NE Monsoon. Strong vertical gradients in euphotic zone NH4- concentration, with higher concentrations at depth, were common. This was in contrast to the nearly uniform euphotic zone concentrations for both NO3- and NO2-. Half-saturation constants for uptake were higher for NO3- (1.7 æmol kg-1 (s.d.=0.88, n=8)) than for NH4+ (0.47 æmol kg-1 (s.d.=0.33, n=5)). Evidence for the suppressing effect of NH4+ on NO3- uptake was widespread, although not as severe as has been noted for some other regions. Both the degree of sensitivity of NO3- uptake to NH4+ concentration and the half-saturation constant for NO3+ uptake were correlated with ambient NO3- concentration. The combined e!ect of high affnity for low concentrations of NH4+ and the effect of NH4+ concentration on NO3- uptake resulted in similarly low f-ratios, 0.15 (s.d.=0.07, n=15) and 0.13 (s.d.=0.08, n=17), for early and late observations in the NE Monsoon, respectively. Stations with high f-ratios had the lowest euphotic zone NH4+ concentrations, and these stations were either very near shore or far from shore in the most oligotrophic waters. At several stations, particularly early in the NE Monsoon, the utilization rates for NO2- were equal to or greater than 50% the utilization rates for NO3- . When converted with a Redfield C : N value of 6.7, the total N uptake rates measured in this study were commensurate with measurements of C productivity. While nutrient concentrations at some stations approached levels low enough to limit phytoplankton growth, light was shown to be very important in regulating N uptake at all stations in this study. Diel periodicity was observed for uptake of all nitrogenous nutrients at all stations. The amplitude of this periodicity was positively correlated with nutrient concentration. The strongest of these relationships occurred with NO3- . Ammonium concentration strongly influenced the vertical profiles for NO3- uptake as well as for NH4+ uptake. Both NO2- and NH4+ were regenerated within the euphotic zone at rates comparable to rates of uptake of these nutrients, and thus maintenance of mixed layer concentrations did not require diffusive or advective fluxes from other sources.  Observed turnover times for NH4+ were typically less than one day. Rapid turnover and the strong light regulation of NH4+ uptake allowed the development and maintenance of vertical structure in NH4+ concentration within the euphotic zone. In spite of the strong positive effect of light on NO2- uptake and its strong negative effect on NO2- production, the combined effects of much longer turnover times for this nutrient and mixed layer dynamics resulted in nearly uniform NO2- concentrations within the euphotic zone. Responses of the NE Monsoon planktonic community to light and nutrients, in conjunction with mixed layer dynamics, allowed for effcient recycling of N within the mixed layer. As the NE Monsoon evolved and the mixed layer deepened convectively, NO2- and NO3- concentrations increased correspondingly with the entrainment of deeper water. Planktonic N productivity increased 2-fold, but without a significant change the new vs. recycled N proportionality. Consequently, NO3- turnover time increased from about 1 month to greater than 3 months. This reflected the overriding importance of recycling processes in supplying nitrogenous nutrients for primary production throughout the duration of the NE Monsoon. As a result, NO3- supplied to the euphotic zone during the NE Monsoon is, for the most part, conserved for utilization during the subsequent intermonsoon period.  },

keywords = {Arabian Sea, depth, development, diel, growth, productivity},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Demersal fisheries of the Arabian Sea, the Gulf of Oman and the Arabian Gulf},

author = {Siddeek,M.S.M.,Fouda,M.M.,Hermosa,G.V.Jr.},

year  = {1999},

date = {1999-01-01},

journal = {Estuarine, Coastal and Shelf Science},

volume = {49},

number = {474},

pages = {87-97},

abstract = {The demersal fisheries of the Arabian Sea, the Gulf of Oman and the Arabian Gulf are reviewed. The region comprises eight countries: Oman, United Arab Emirates (U.A.E.), Qatar, Saudi Arabia, Bahrain, Kuwait, Iraq and Iran. Over 350 commercial fish species, eight shrimp species, two spiny lobster species, one shovel nose lobster species, one cuttlefish species, one crab species, and one abalone species support the demersal fisheries in the continental shelves of the three regions. Artisanal and industrial vessels with over 120 000 fishermen were involved in demersal fisheries. Fishing boats include fish and shrimp trawlers (wooden and steel hulled), large wooden boats (dhow) with inboard engines, small dhows with outboard engines, and fiberglass boats. Fishing gear consists of trawls, bottom gill nets, traps (wire mesh and plastic types), barrier traps, hand lines, and bare hands and knives (to dislodge abalone). Demersal fish (primarily Lethrinidae, Sparidae, Serranidae, Siganidae, Sciaenidae, Stromateidae, Lutjanidae, Trichiuridae, and Nemipteridae) and shrimp (primarily Penaeus semisulcatus, Metapenaeus affinis, Parapenaeopsis stylifera, and Penaeus merguiensis) were the two commercial demersal resources. Approximately 198 000-214 000 tonnes (t) of demersals were landed annually during 1988-1993, accounting for nearly 40% of the total marine landings (475000-552000 t). This percentage, however varied among countries: 25% in Oman, 32% in U.A.E., 71% in Qatar, 52% in Saudi Arabia, 56% in Bahrain, 55% in Kuwait, close to 100% in Iraq, and 41% in Iran. Fishing effort on certain stocks may have been below the optimum level (e.g. certain Omani demersal fish), near the optimum level (e.g. Omani shrimp), or above the optimum level ( e.g. Arabian Gulf shrimp and demersal fish). Overexploitation led to restriction of fishing effort by limiting fishing licenses, regulating fishing gear (mesh size) and capture size, closing fishing areas, restricting fishing season, and banning certain fisheries. However, fisheries management was hampered by lack of appropriate management regulations, enforcement and data on most stocks. Pollution and degradation of nursery areas were also affecting the productivity of fisheries resources. To achieve sustainable demersal fisheries, maintaining a healthy marine environment, reducing fishing effort, and strictly enforcing closed seasons and closed areas are needed. These measures are being implemented with varying degrees of success by all the countries.},

keywords = {Arabian Gulf, Arabian Sea, enforcement, Fisheries, fishing gear, Gulf of Oman, management, marine, nets, Oman, pollution, productivity, regulations, trap, trawlers},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Seasonal variation of hydrographic and nutrient fields during the US JGOFS Arabian Sea Process Study},

author = {Morrison, John M,Codispoti, LA,Gaurin, S,Jones, B,Manghnani, V,Zheng, Z},

issn = {0967-0645},

year  = {1998},

date = {1998-01-01},

journal = {Deep Sea Research Part II: Topical Studies in Oceanography},

volume = {45},

number = {419},

pages = {2053-2101},

abstract = {Between September 1994 and December 1995, the US JGOFS Arabian Sea Process Experiment collected extensive, high quality hydrographic data (temperature, salinity, dissolved oxygen and nutrients) during all seasons in the northern Arabian Sea. An analysis of this unique data suite suggests the presence of many features that are described in the canonical literature, but these new data provided the following insights.

1.

Although the seasonal evolution of mixed-layer depths was in general agreement with previous descriptions, the deepest mixed-layer depths in our data occurred during the late NE Monsoon instead of the SW Monsoon.



2.

The region exhibits considerable mesoscale variability resulting in extremely variable temperature-salinity (TS) distributions in the upper 1000 db. This mesoscale variability is readily observed in satellite imaging, in the high resolution data taken by a companion ONR funded project, and in underway ADCP data.



3.

The densest water reaching the sea surface during coastal upwelling appeared to have maximum offshore depths of },

keywords = {Arabian Sea, Nutrient cycling, Oman, productivity, Upwelling},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Interannual variability in phytoplankton blooms observed in the northwestern Arabian Sea during the southwest monsoon},

author = {Brock,J.C.,McClain,C.R.},

year  = {1992},

date = {1992-01-01},

journal = {Journal of Geophysical Research},

volume = {97},

number = {52},

pages = {733-750},

abstract = {Interannual changes in the strength and seasonal evolution of the 1979 through 1982 surface level southwest monsoon winds have been related to variations in the summer phytoplankton bloom of the northwestern Arabian Sea by synthesis of satellite ocean color remote sensing with analysis of in situ hydrographic and meteorological data sets. The 1979-1981 southwest monsoon phytoplankton blooms in the northwest Arabian Sea peaked during August-September, extended from the Omani coast to about 65øE, and appeared to lag the development of open-sea upwelling by at least 1 month. In all 3 years the bloom was driven by spatially distinct upward nutrient fluxes to the euphotic zone forced by the physical processes of coastal upwelling and offshore Ekman pumping. Coastal upwelling was evident from May through September, yielded the most extreme concentrations of phytoplankton biomass, and along the Omani coast was limited in its impact on upper ocean biological variability to the continental shelf. Ekman pumping stimulated the development of a broad open-ocean component of the southwest monsoon phytoplankton bloom oceanward of the Omani shelf. Phytoplankton biomass on the Omani continental shelf was increased during both the early and late phases of the 1980 southwest monsoon due to stronger coastal upwelling under the most intense southwesterly winds of the four summers investigated. Diminished coastal upwelling during the early phase of the weak 1982 southwest monsoon resulted in a coastal bloom that reached a mean phytoplankton pigment concentration that was 28% of that seen in 1980. The lack of a strong regional northwestern Arabian Sea bloom in late summer 1982 is attributed to the development of persistent, shallow temperature stratification that rendered Ekman pumping less effective in driving upward nutrient fluxes.},

keywords = {Arabian Sea, plankton, productivity, temperature, Upwelling},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Remarks on the distribution and migration of whales},

author = {Slijper,E.J.,Van Utrecht,W.L.,Naaktgeboren,C.},

year  = {1964},

date = {1964-01-01},

journal = {Bijdragen tot de Dierkunde},

volume = {34},

number = {475},

pages = {4-86},

abstract = {The authors gained the cooperation of the Netherlands Association of Ship Owners and the Royal Netherlands Navy in a project to collect all whale sightings from vessels sailing around the globe between 1954 and 1957. A total of 4500 reports of 11,000 animals were received, with the majority of observations coming from the Atlantic and Indian Oceans. Vessels were given identification guides and all reported observations were scored on the perceived reliability of the identification.  All Rorqual whales were grouped together, and a further distinction was made between humpback, sperm, right whales and "little piked whales" (minke whales).  Sightings were plotted in 10 degree squares according to number of whales observed per 1000 hours steamed in daylight.  Special attention is given to the observations of Captain W.F.J. Morzer Bruins, who the authors describe as a keen naturalist whose observations hold more credibility than those of others.  His observations in the Indian Ocean include a high number of sperm whales off the southern coast of Oman and the Gulf of Aden in January-March and April-June, a scattering of stranded blue and fin whales along the W coast of India, and only 2 stranded and 2 live humpback whales (strandings both in India, and live sightings near Yemen/Oman border? and off S tip of India (near Maldives?).  The larger number of compiled sightings from vessels are presented by species.  Rorqual sightings were plentiful in the Gulf of Aden, Arabian Sea coasts of Oman and Pakistan, and in the Arabian Gulf (but not as plentiful as they were in the area between 30 and 40 degrees S.  The author concludes that the majority of the whales observed in the NIO do not belong to the Southern Hemisphere stock, but suggests that they migrate from the North Pacific through the Indonesian Archipelago and the Strait Malaya (despite very few observations here).  He briefly considers, but discards as unlikely, the hypothesis of a resident NIO stock.The total number of humpback whale sightings in the IO amounted to 500 (compared to 1618 rorqual sightings and 799 "whale" sightings).  The majority of animals were observed in coastal waters, and NIO sightings were generally concentrated in the months of Aug-Nov and Jan-April.  some of the highest recorded densities in the NIO are off of Pakistan  in the months of March, Aug, Oct, and December, but it is not clear how closely related this is to observer effort.  Observations are very few in May, June, July and September, and the authors do not link this to the monsoon -but rather conclude that the whales are not present at that time. Although few calves were observed in the NIO, those that were observed, were all observed in November, January or September (but no indication is given of calf size). The authors conclude that this is evidence that the observed whales do not belong to the S. Hem stock, but are more likely from the N.Pacific, despite the fact that there are "no sightings of humpbacks in the south China Sea or the Indonesian Archipelago that could support this assumption".  Sperm whales were observed with regularity throughout the year in the NIO, but in lower densities than Rorquals.  A low number of sightings in the NIO during summer months again leads the author to conclude that the animals either migrate South or to the N. Pacific.  This species, according to the authors is always associated with areas of high productivity.Minke whales were recorded in low densities in the Gulf of Aden and off the coast of Pakistan, but not in the central or Northern coasts of Oman.},

keywords = {Arabian Gulf, Arabian Sea, Atlantic, density, Distribution, fin whale, Gulf of Aden, Humpback Whale, humpback whales, India, Indian Ocean, Maldives, migration, minke whale, minke whales, North Pacific, Oman, Pakistan, productivity, right whale, right whales, Southern Hemisphere, sperm whale, sperm whales, Strandings, whale, whales},

pubstate = {published},

tppubtype = {article}

}