@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 = {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}

}

@article{,

title = {The oxygen minimum zone in the Arabian Sea during 1995},

author = {Morrison,J.M.,Codispoti,L.A.,Smith,S.L.,Wishner,K.,Flagg,C.,Gardner,W.D.,Gaurin,S.,Naqvi,S.W.A.,Manghnani,V.,Prosperie,L.,Gundersen,J.S.},

year  = {1999},

date = {1999-01-01},

journal = {Deep-Sea Research Part II},

volume = {46},

number = {174},

pages = {1903-1931},

abstract = {This paper focuses on the characteristics of the oxygen minimum zone (OMZ) as observed in the Arabian Sea over the complete monsoon cycle of 1995. Dissolved oxygen, nitrite, nitrate and density values are used to delineate the OMZ, as well as identify regions where denitrification is observed. The suboxic conditions within the northern Arabian Sea are documented, as well as biological and chemical consequences of this phenomenon. Overall, the conditions found in the suboxic portion of the water column in the Arabian Sea were not greatly different from what has been reported in the literature with respect to oxygen, nitrate and nitrite distributions. Within the main thermocline, portions of the OMZ were found that were suboxic (oxygen less than ~4.5 æM) and contained secondary nitrite maxima with concentrations that sometimes exceeded 6.0 æM, suggesting active nitrate reduction and denitrification. Although there may have been a reduction in the degree of suboxia during the Southwest monsoon, a dramatic seasonality was not observed, as has been suggested by some previous work. In particular, there was not much evidence for the occurrence of secondary nitrite maxima in waters with oxygen concentrations greater than 4.5 æM. Waters in the northern Arabian Sea appear to accumulate larger nitrate deficits due to longer residence times even though the denitrification rate might be lower, as evident in the reduced nitrite concentrations in the northern part of the basin. Organism distributions showed string relationships to the oxygen profiles, especially in locations where the OMZ was pronounced, but the biological responses to the OMZ varied with type of organism. The regional extent of intermediate nepheloid layers in our data corresponds well with the region of the secondary nitrite maximum. This is a region of denitrification, and the presence and activities of bacteria are assumed to cause the increase in particles. ADCP acoustic backscatter measurements show diel vertical migration of plankton or nekton and movement into the OMZ. Daytime acoustic returns from depth were strong, and the dawn sinking and dusk rise of the fauna were obvious. However, at night the biomass remaining in the suboxic zone was so low that no ADCP signal was detectable at these depths. There are at least two groups of organisms, one that stays in the upper mixed layer and another that makes daily excursions. A subsurface zooplankton peak in the lower OMZ (near the lower 4.5 æM oxycline) was also typically present; these animals occurred day and night and did not vertically migrate.},

keywords = {acoustic, Arabian Sea, density, depth, diel, Distribution, location, migrate, migration, occurrence, oxygen minimum, plankton, thermocline, zooplankton},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Biohydro-optical classification of the northwestern Indian Ocean},

author = {Brock,J.C.,Sathyendranath,S.,Platt,T.},

year  = {1998},

date = {1998-01-01},

journal = {Marine Ecology Progress Series},

volume = {165},

number = {338},

pages = {1-15},

abstract = {An approach to a partial solution to the general problem of defining biogeochemical provinces for the accurate estimation of global-ocean primary production and realistic structuring of epipelagic plankton ecosystem models is presented for the northwestern Indian Ocean.  This is accomplished through use of a new technique, biohydro-optical classification, that applies a rudimentary submarine light budget incorporating climatologies of incident light, mixed layer thickness, and chlorophyll to recognize fundamental modes of tropical plankton ecosystems.  The three types of biohydro-optical classes found in the  Arabian Sea, Typical Tropical, Mixed-Layer Bloom, and Transitional, are shown to evolve thorough the spring intermonsoon (March through May) summer southwest monsoon (June thorough August), and fall intermonsoon (Sep through Nov)  under climatic forcing and in response to the resulting biological variability. Virtually all of the open Arabian Sea is within the Typical Tropical Class at the close of the spring intermonsoon.  This class type is intended to identify the maximum (DCM) maintained by active algal growth, and light-rich oligotrophic shallow zone containing phytoplankton association which depends largely on regenerated nutrients. At the close of the southwest monsoon in August, a mixed layer bloom province covers much of the northern Arabian Sea. This province class corresponds to the ecosystem mode represented by tropical regions undergoing marginal or mid-ocean upwelling and greatly simplifies regional extrapolation of the local primary production algorithm.  At the onset of the fall intermonsoon, the mixed layer algal bloom province in the northern and western Arabian Sea is superseded by a transitional province, which persists through the fall intermonsoon.  We interpret the upper layer of the fall intermonsoon transitional province in the Arabian Sea as a special case of the shallow regenerative plankton ecosystem of oligotrophic ocean areas, where rates of zooplankton-driven nutrient regeneration and recycled production, key processes in the upper layer of the classic 2-layer euphotic zone or oligotrophic low-latitude oceans, reach extreme values.Note on diagrams/maps in paper:Of all the regions of the nw Arabian Sea, the coastal areas off Oman and Yemen are most often in the Transitional or Mixed layer bloom classes.  The Gulf of Masirah maintains a mixed layer bloom class thorughout the year, even when other coastal areas of Oman switch to a Transitional class.},

keywords = {Arabian Sea, chlorophyll, ecosystem, Gulf of Masirah, Indian Ocean, Oman, plankton, Upwelling},

pubstate = {published},

tppubtype = {article}

}

@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 = {Some features of the upwelling off Oman},

author = {Elliott,A.J.,Savidge,G.},

year  = {1990},

date = {1990-01-01},

journal = {Journal of Marine Research},

volume = {48},

number = {365},

pages = {319-333},

abstract = {Hydrographic and ADCP data were collected in the coastal waters of Oman during the 1987 summer monsoon.  the minimum surface temperatures, up to 5§C below ambient offshore values, were found close to the coast and in the vicinity of the Kuria Muria Islands.  Strong surface gradients were observed near Ras al Hadd at the entrance to the Gulf of Oman where the geostrophic surface flow exceeded 1.0m/s.  The alongshore flux in the top 300m of a region extending 100km from the coast was estimated to be 10 x 106 m3/s.  Evidence for an offshore filament of cool water was found in both current and temperature data.},

keywords = {Gulf of Oman, oceanography, Oman, plankton, surface temperature, temperature, Upwelling},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Euphausiids of the Indian Ocean and the Red Sea (original title Ehvfauziidy Indijskogo okeana I krasnogo morya)},

author = {Ponomareva,L.A.},

year  = {1975},

date = {1975-01-01},

journal = {Nauka},

volume = {1},

number = {197},

abstract = {The study is mainly based on euphausiid material from 2390 plankton samples collected in the Indian Ocean during Oct-March 1959/60 and 1960/61. Data are presented on the sp composition, biology, vertical and quantitative distribution. The northern Indian Ocean (as far south as 40 degree S) is inhabited by typically tropical euphausiid fauna. The area most rich in euphausiids is the Arabian Sea. The spp most commonly occurring in the 0-200m layer in the Indian Ocean are Euphausia diomedeae, E. distinguenda, Stylocheiron carinatum and Thysanopoda tricuspidata. In the northern Indian Ocean eggs an early larval stages occurred from Jan to June (no observations were made later in the yr), which suggests that euphausiids spawn several times during the yr. The eggs develop very rapidly (within <24h) and so do early larval stages. On reaching the nauplius-2 stage the development slows down and it takes the larva 10-12 days to develop into furcilia-1. The feeding is varied and mixed: none of the spp were observed to feed on phyto- or zooplankton exclusively. Migratory spp show diurnal feeding rhythms. Most of the spp occurring in the upper layers ( down to 500m) are distinct migrants; interzonal spp do not perform significant migrations rarely rising close to the surface and almost never occurring above 50-40m.  The Red Sea is inhabited by immigrants from teh Gulf of Aden and by some endemic spp. The spp abundant in the Arabian Sea are also predominant here with the addition of S. affine. },

keywords = {Arabian Sea, biology, Distribution, Euphausiid, feeding, Indian Ocean, migration, plankton, Red Sea, zooplankton},

pubstate = {published},

tppubtype = {article}

}