Annual ecosystem variability in the tropical Indian Ocean: Results of a coupled bio-physical ocean general circulation model

Wiggert, Jerry D.; Murtugudde, Raghu; Christian, James R.

doi:10.1016/j.dsr2.2006.01.027

Cited by 183 publications

(207 citation statements)

References 84 publications

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“…The Equatorial Pacific Upwelling Region sampled here has been shown to have extremely low available iron (≤0.1 nM) and is thought to limit phytoplankton growth (40,41). Part of the Indian Ocean gyre may also be iron limited (42,43), although the BEC model suggests otherwise (22). However, the biogeochemistry is less defined here compared with the Pacific and Atlantic Oceans.…”

Section: Discussionmentioning

confidence: 65%

Characterization ofProchlorococcusclades from iron-depleted oceanic regions

Rusch

Martiny

Dupont

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

163

190

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Prochlorococcus describes a diverse and abundant genus of marine photosynthetic microbes. It is primarily found in oligotrophic waters across the globe and plays a crucial role in energy and nutrient cycling in the ocean ecosystem. The abundance, global distribution, and availability of isolates make Prochlorococcus a model system for understanding marine microbial diversity and biogeochemical cycling. Analysis of 73 metagenomic samples from the Global Ocean Sampling expedition acquired in the Atlantic, Pacific, and Indian Oceans revealed the presence of two uncharacterized Prochlorococcus clades. A phylogenetic analysis using six different genetic markers places the clades close to known lineages adapted to high-light environments. The two uncharacterized clades consistently cooccur and dominate the surface waters of high-temperature, macronutrient-replete, and low-iron regions of the Eastern Equatorial Pacific upwelling and the tropical Indian Ocean. They are genetically distinct from each other and other high-light Prochlorococcus isolates and likely define a previously unrecognized ecotype. Our detailed genomic analysis indicates that these clades comprise organisms that are adapted to iron-depleted environments by reducing their iron quota through the loss of several iron-containing proteins that likely function as electron sinks in the photosynthetic pathway in other Prochlorococcus clades from high-light environments. The presence and inferred physiology of these clades may explain why Prochlorococcus populations from iron-depleted regions do not respond to iron fertilization experiments and further expand our understanding of how phytoplankton adapt to variations in nutrient availability in the ocean.

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Section: Discussionmentioning

confidence: 65%

Characterization ofProchlorococcusclades from iron-depleted oceanic regions

Rusch

Martiny

Dupont

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

163

190

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“…Recent results of modeling (Wiggert et al, 2006) as well as observations (Naqvi et al, unpublished manuscript) suggest that, contrary to the prevalent belief, PP in the western Arabian Sea might sometimes be limited by iron instead of nitrogen during the southwest (SW) monsoon. Aerosol analysis during the SW monsoon also revealed very low (below detection limit) concentrations of the labile-Fe(II) off the central Omani coast, presumably because the air masses during this season come from the pristine southern hemisphere (Sierfert et al, 1999).…”

Section: Processes Of Formation Of Coastal and Open-ocean Suboxic 1 Zmentioning

confidence: 89%

Coastal versus open-ocean denitrification in the Arabian Sea

Naqvi

Naik²,

Pratihary³

et al. 2006

Biogeosciences

159

132

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Abstract. The Arabian Sea contains one of the three major open-ocean denitrification zones in the world. In addition, pelagic denitrification also occurs over the inner and midshelf off the west coast of India. The major differences between the two environments are highlighted using the available data. The perennial open-ocean system occupies two orders of magnitude larger volume than the seasonal coastal system, however, the latter offers more extreme conditions (greater nitrate consumption leading to complete anoxia). Unlike the open-ocean system, the coastal system seems to have undergone a change (i.e., it has intensified) over the past few decades presumably due to enhanced nutrient loading from land. The two systems also differ from each other with regard to the modes of nitrous oxide (N 2 O) production: In the open-ocean suboxic zone, an accumulation of secondary nitrite (NO

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“…A recent modelling study by Wiggert et al (2006) predicts an intensifying region of Fe limitation in the western Arabian Sea through the SWM and into October. In addition to the above-mentioned high NO − 3 :Fe ratio in the upwelled water, modelled Fe limitation also reflects the low aeolian Fe deposition predicted by the GOCART atmospheric transport model (Ginoux et al, 2001).…”

Section: Low Phytoplankton Biomass and Production Off The Southern Ommentioning

confidence: 99%

The Arabian Sea as a high-nutrient, low-chlorophyll region during the late Southwest Monsoon

et al. 2010

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Abstract.Extensive observations were made during the late Southwest Monsoon of 2004 over the Indian and Omani shelves, and along a transect that extended from the southern coast of Oman to the central west coast of India, tracking the southern leg of the US JGOFS expedition (1994)(1995) in the west. The data are used, in conjunction with satellite-derived data, to investigate long-term trends in chlorophyll and sea surface temperature, indicators of upwelling intensity, and to understand factors that control primary production (PP) in the Arabian Sea, focussing on the role of iron. Our results do not support an intensification of upwelling in the western Arabian Sea, reported to have been caused by the decline in the winter/spring Eurasian snow cover since 1997. We also noticed, for the first time, an unexpected development of high-nutrient, low-chlorophyll condition off the southern Omani coast. This feature, coupled with other characteristics of the system, such as a narrow shelf and relatively low iron concentrations in surface waters, suggest a close similarity between the Omani upwelling system and the Peruvian and California upwelling systems, where PP is limited by iron. Iron limitation of PP may complicate simple relationship between upwelling and PP assumed by previous workers, and contribute to the anomalous offshore occurrence of the most severe oxygen (O 2 ) depletion in the region. Over the much wider Indian shelf, which experiences large-scale bottom water O 2 -depletion in summer, adequate iron supply from reCorrespondence to: S. W. A. Naqvi (naqvi@nio.org) ducing bottom-waters and sediments seems to support moderately high PP; however, such production is restricted to the thin, oxygenated surface layer, probably because of the unsuitability of the O 2 -depleted environment for the growth of oxygenic photosynthesizers.

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Annual ecosystem variability in the tropical Indian Ocean: Results of a coupled bio-physical ocean general circulation model

Cited by 183 publications

References 84 publications

Characterization ofProchlorococcusclades from iron-depleted oceanic regions

Characterization ofProchlorococcusclades from iron-depleted oceanic regions

Coastal versus open-ocean denitrification in the Arabian Sea

The Arabian Sea as a high-nutrient, low-chlorophyll region during the late Southwest Monsoon

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