Barber,R.T.,Marra,J.,Bidigare,R.C.,Codispoti,L.A.,Halpern,D.,Johnson,Z.,Latasa,M.,Goericke,R.,Smith,S.L.
Primary productivity and its regulation in the Arabian Sea during 1995 Journal Article
In: Deep-Sea Research Part II, vol. 48, no. 323, pp. 1127-1172, 2001.
Abstract | BibTeX | Tags: abundance, Arabian Sea, Atlantic, location, North Atlantic, Oman, Pacific Ocean, performance, productivity, Upwelling
@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}
}
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
Johnson,Z.,Landry,M.L.,Bidigare,R.R.,Brown,S.L.,Campbell,L.,Gunderson,J.,Marra,J.,Trees,C.
Energetics and growth kinetics of a deep Prochlorococcus spp. population in the Arabian Sea Journal Article
In: Deep-Sea Research Part II, vol. 46, no. 129, pp. 1719-1743, 1999.
Abstract | BibTeX | Tags: Arabian Sea, chlorophyll, growth, marine, performance, population, populations
@article{,
title = {Energetics and growth kinetics of a deep Prochlorococcus spp. population in the Arabian Sea},
author = {Johnson,Z.,Landry,M.L.,Bidigare,R.R.,Brown,S.L.,Campbell,L.,Gunderson,J.,Marra,J.,Trees,C.},
year = {1999},
date = {1999-01-01},
journal = {Deep-Sea Research Part II},
volume = {46},
number = {129},
pages = {1719-1743},
abstract = {During the US JGOFS process studies in the Arabian Sea (1995), secondary fluorescence maxima (SFM) were observed frequently at the oxic-anoxic interface at the extreme base of the euphotic zone. These secondary peaks were most prominent during the early NE monsoon in the central oligotrophic portion of the Arabian Sea, although they were spatially and temporally variable. Based on high performance liquid chromatography (HPLC) and flow cytometry analyses, SFM were determined to be populated almost exclusively by the marine cyanobacterium Prochlorococcus spp. While SFM were about half the magnitude of primary fluorescence peaks, chlorophyll a biomass was typically an order of magnitude less than at the primary maxima (although total chlorophyll (a + b) differed only by a factor of two). Photosynthesis versus irradiance response curves revealed an efficient population adapted to extremely low light (~0.02-0.05% surface irradiance) largely through increased light absorption capabilities. A theoretical spectral irradiance absorption effciency model based on available spectral irradiance, individual cell properties, and bulk particulate spectral absorption also supports a well-adapted low-light population. Deck-incubated C-14 uptake as well as dilution growth experiments revealed instantaneous growth rates on the order of æ = 0.01 d-1. However, additional in situ observations suggest SFM populations may be more dynamic than the growth rates estimates from shipboard bottle incubations predict. We advance four hypotheses for the regulation of SFM populations including: (1) reduced loss rates, (2) discontinuous environmental conditions, (3) enhanced sub-oxic growth, and (4) physical mechanisms.},
keywords = {Arabian Sea, chlorophyll, growth, marine, performance, population, populations},
pubstate = {published},
tppubtype = {article}
}
During the US JGOFS process studies in the Arabian Sea (1995), secondary fluorescence maxima (SFM) were observed frequently at the oxic-anoxic interface at the extreme base of the euphotic zone. These secondary peaks were most prominent during the early NE monsoon in the central oligotrophic portion of the Arabian Sea, although they were spatially and temporally variable. Based on high performance liquid chromatography (HPLC) and flow cytometry analyses, SFM were determined to be populated almost exclusively by the marine cyanobacterium Prochlorococcus spp. While SFM were about half the magnitude of primary fluorescence peaks, chlorophyll a biomass was typically an order of magnitude less than at the primary maxima (although total chlorophyll (a + b) differed only by a factor of two). Photosynthesis versus irradiance response curves revealed an efficient population adapted to extremely low light (~0.02-0.05% surface irradiance) largely through increased light absorption capabilities. A theoretical spectral irradiance absorption effciency model based on available spectral irradiance, individual cell properties, and bulk particulate spectral absorption also supports a well-adapted low-light population. Deck-incubated C-14 uptake as well as dilution growth experiments revealed instantaneous growth rates on the order of æ = 0.01 d-1. However, additional in situ observations suggest SFM populations may be more dynamic than the growth rates estimates from shipboard bottle incubations predict. We advance four hypotheses for the regulation of SFM populations including: (1) reduced loss rates, (2) discontinuous environmental conditions, (3) enhanced sub-oxic growth, and (4) physical mechanisms.