scholarly journals Spatial Variation in Primary Production in the Eastern Indian Ocean

2021 ◽  
Vol 8 ◽  
Author(s):  
Haijiao Liu ◽  
Yuyao Song ◽  
Xiaodong Zhang ◽  
Guicheng Zhang ◽  
Chao Wu ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Primary Production ◽  
Carbon Fixation ◽  
Monsoon Season ◽  
Biological Data ◽  
Eastern Indian Ocean ◽  
Light Limitation ◽  
Photic Zone ◽  
Production Rates ◽  
Study Region

To examine the spatial pattern and controlling factors of the primary productivity (PP) of phytoplankton in the eastern Indian Ocean (EIO), deck-incubation carbon fixation (a 14C tracer technique) and the related hydrographic properties were measured at 15 locations during the pre-summer monsoon season (February–April 2017). There are knowledge gaps in the field observations of PP in the EIO. The estimated daily carbon production rates integrated over the photic zone ranged from 113 to 817 mgC m–2 d–1, with a mean of 522 mgC m–2 d–1. The mixed-layer integrated primary production (MLD-PP) ranged from 29.0 to 303.7 mgC m–2 d–1 (mean: 177.2 mgC m–2 d–1). The contribution of MLD-PP to the photic zone-integrated PP (PZI-PP) varied between 19 and 51% (mean: 36%). Strong spatial variability in the carbon fixation rates was found in the study region. Specifically, the surface primary production rates were relatively higher in the Bay of Bengal domain affected by riverine flux and lower in the equatorial domain owing to the presence of intermonsoonal Wyrtki jets, which were characterized by a depression of thermocline and nitracline. The PZI-PP exhibited a linear (positive) relationship with nutrient values, but with no significance, indicating a partial control of macronutrients and a light limitation of carbon fixation. As evident from the vertical profiles, the primary production process mainly occurred above the nitracline depth and at high photosynthetic efficiency. Phytoplankton (>5 μm), including dinoflagellates, Trichodesmium, coccolithophores, and dissolved nutrients, are thought to have been correlated with primary production during the study period. The measured on-deck biological data of our study allow for a general understanding of the trends in PP in the survey area of the EIO and can be incorporated into global primary production models.

In-water algorithms for estimation of chlorophyll a and primary production in the Arabian Sea and the eastern Indian Ocean

1997 ◽  
Author(s):  
Toru Hirawake ◽  
Hiroo Satoh ◽  
Tsutomu Morinaga ◽  
Takashi Ishimaru ◽  
Motoaki Kishino
Keyword(s):  
Indian Ocean ◽  
Primary Production ◽  
Chlorophyll A ◽  
Arabian Sea ◽  
Eastern Indian Ocean

scholarly journals SOME BIOLOGICAL ASPECTS OF SCALLOPED HAMMERHEAD SHARKS (Sphyrna lewini Griffith & Smith, 1834) CAUGHT FROM COASTAL FISHERIES IN THE EASTERN INDIAN OCEAN

2015 ◽  
Vol 21 (2) ◽  
pp. 91
Author(s):  
Umi Chodrijah ◽  
Bram Setyadji
Keyword(s):  
Indian Ocean ◽  
Size Composition ◽  
Biological Data ◽  
Biological Information ◽  
Eastern Indian Ocean ◽  
Coastal Fisheries ◽  
Hammerhead Shark ◽  
Total Length ◽  
Scalloped Hammerhead ◽  
The World

Indonesia has the largest chondrichthyan fishery in the world, with a reported of 105,000 and 118,000 tonnes landed in 2002 and 2003 respectively. Scalloped hammerhead shark was either targeted or by-catch from this fishery, mostly for its fins. Despite of the growing concern around the world, the availability of biological data of this species, especially in the Eastern Indian Ocean is still lacking. The objectives of this paper are to present some biological information (size composition and sex ratio) of the scalloped hammerhead, from coastal fisheries in Eastern Indian Ocean. The data used for the analysis comprised of two components, i.e. survey data in 2010 (February, March, June, August, October and December) and data from daily monitoring shark landing in 2013 (January to December). Substantially lower mean size, more immature sharks and more frequent of female caught over years showed that scalloped hammerhead shark in the Eastern Indian Ocean are facing intensive fishing pressure which could lead to overfishing. This could harm the sustainability of scalloped hammerhead shark resource in the long run. The relationship between clasper length and total length was positively correlated where every 5 cmTL increment on clasper length adding 51 cmTL on total length.

scholarly journals The Composition and Primary Metabolic Potential of Microbial Communities Inhabiting the Surface Water in the Equatorial Eastern Indian Ocean

Biology ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 248
Author(s):  
Changling Ding ◽  
Chao Wu ◽  
Congcong Guo ◽  
Jiang Gui ◽  
Yuqiu Wei ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Microbial Communities ◽  
High Throughput Sequencing ◽  
Carbon Fixation ◽  
Calvin Cycle ◽  
Nitrite Reduction ◽  
16S Rrna Genes ◽  
Eastern Indian Ocean ◽  
Rrna Genes ◽  
Metabolic Potential

Currently, there is scant information about the biodiversity and functional diversity of microbes in the eastern Indian Ocean (EIO). Here, we used a combination of high-throughput sequencing of 16S rRNA genes and a metagenomic approach to investigate the microbial population structure and its metabolic function in the equatorial EIO. Our results show that Cyanobacterial Prochlorococcus made up the majority of the population. Interestingly, there were fewer contributions from clades SAR11 (Alphaproteobacteria) and SAR86 (Gammaproteobacteria) to microbial communities than contributions from Prochlorococcus. Based on functional gene analysis, functional genes rbcL, narB, and nasA were relatively abundant among the relevant genes. The abundance of Prochlorococcus implies its typically ecological adaptation in the local ecosystem. The microbial metabolic potential shows that in addition to the main carbon fixation pathway Calvin cycle, the rTCA cycle and the 3-HP/4-HB cycle have potential alternative carbon fixation contributions to local ecosystems. For the nitrogen cycle, the assimilatory nitrate and nitrite reduction pathway is potentially the crucial form of nitrogen utilization; unexpectedly, nitrogen fixation activity was relatively weak. This study extends our knowledge of the roles of microbes in energy and resource cycling in the EIO and provides a foundation for revealing profound biogeochemical processes driven by the microbial community in the ocean.

scholarly journals Indian ocean marine biogeochemical variability and its feedback on simulated South Asia climate

2021 ◽  
Author(s):  
Dmitry V. Sein ◽  
Anton Y. Dvornikov ◽  
Stanislav D. Martyanov ◽  
William Cabos ◽  
Vladimir A. Ryabchenko ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Primary Production ◽  
Light Absorption ◽  
Large Scale ◽  
Monsoon Season ◽  
Light Attenuation ◽  
Convective Precipitation ◽  
Phytoplankton Primary Production ◽  
Cascading Effects ◽  
Subsurface Layers

Abstract. We investigate the effect of variable marine biogeochemical light absorption on Indian Ocean sea surface temperature (SST) and how this affects the South Asian climate. In twin experiments with a regional Earth System Model, we found that the average SST is lower over most of the domain when variable marine biogeochemical light absorption is taken into account, compared to the reference experiment with a constant light attenuation coefficient equal to 0.06 m-1. The most significant deviations (more than 1 °C) in SST are observed in the summer period. A considerable cooling of subsurface layers occurs, and the thermocline shifts upward in the experiment with the activated biogeochemical impact. Also, the phytoplankton primary production becomes higher, especially during periods of winter and summer phytoplankton blooms. The effect of altered SST variability on climate was investigated by coupling the ocean models to a regional atmosphere model. We find the largest effects on the amount of precipitation, particularly during the monsoon season. In the Arabian Sea, the reduction of the transport of humidity across the equator leads to a reduction of the large-scale precipitation in the eastern part of the basin, reinforcing the reduction of the convective precipitation. In the Bay of Bengal, it increases the large-scale precipitation, countering convective precipitation decline. Thus, the key impacts of including the full biogeochemical coupling with corresponding light attenuation, which in turn depends on variable chlorophyll-a concentration, include the enhanced phytoplankton primary production, a shallower thermocline, decreased SST and water temperature in subsurface layers, with cascading effects upon the model ocean physics which further translates into altered atmosphere dynamics.

scholarly journals No nitrogen fixation in the Bay of Bengal?

2019 ◽  
Author(s):  
Carolin R. Löscher ◽  
Wiebke Mohr ◽  
Hermann W. Bange ◽  
Donald E. Canfield
Keyword(s):  
Primary Production ◽  
Water Column ◽  
Bay Of Bengal ◽  
N2 Fixation ◽  
Carbon Fixation ◽  
Monsoon Season ◽  
Stable Stratification ◽  
Water Column Stratification ◽  
Tropical Oceans ◽  
Subsurface Waters

Abstract. The Bay of Bengal (BoB) has long stood as a biogeochemical enigma with subsurface waters containing extremely low, but persistent, concentrations of oxygen in the nanomolar range which – for some, yet unconstrained reason – are prevented from becoming anoxic. One reason for this may be the low productivity of the BoB waters due to nutrient limitation, and the resulting lack of respiration of organic material at intermediate waters. Thus, the parameters determining primary production are key to understanding what prevents the BoB from developing anoxia. Primary productivity in the sunlit surface layers of tropical oceans is mostly limited by the supply of reactive nitrogen through upwelling, riverine flux, atmospheric deposition, and biological dinitrogen (N2) fixation. In the BoB, a stable stratification limits nutrient supply via upwelling in the open waters, and riverine or atmospheric fluxes have been shown to support only less than one quarter of the nitrogen for primary production. This leaves a large uncertainty for most of the BoB's nitrogen input, suggesting a potential role of N2 fixation in those waters. Here, we present a survey of N2 fixation and carbon fixation in the BoB during the winter monsoon season. We detected a community of N2 fixers comparable to other OMZ regions, with only a few cyanobacterial clades and a broad diversity of non-phototrophic N2 fixers present throughout the water column (samples collected between 10 m and 560 m water depth). While similar communities of N2 fixers were shown to actively fix N2 in other OMZs, N2 fixation rates were below the detection limit in our samples covering the water column between the deep chlorophyll maximum and the OMZ. Consistent with this, no N2 fixation signal was visible in δ15N signatures. We suggest that the absence of N2 fixation may be a consequence of a micronutrient limitation or of an O2 sensitivity of the OMZ diazotrophs in the BoB. To explore how the onset of N2 fixation by cyanobacteria compared to non-phototrophic N2 fixers would impact on OMZ O2 concentrations, a simple model exercise was carried out. We observed that both, photic zone-based and OMZ-based N2 fixation are very sensitive to even minimal changes in water column stratification, with stronger mixing increasing organic matter production and export, which would exhaust remaining O2 traces in the BoB.

scholarly journals No nitrogen fixation in the Bay of Bengal?

2020 ◽  
Vol 17 (4) ◽  
pp. 851-864 ◽  
Author(s):  
Carolin R. Löscher ◽  
Wiebke Mohr ◽  
Hermann W. Bange ◽  
Donald E. Canfield
Keyword(s):  
Primary Production ◽  
Water Column ◽  
Bay Of Bengal ◽  
N2 Fixation ◽  
Carbon Fixation ◽  
Monsoon Season ◽  
Stable Stratification ◽  
Water Column Stratification ◽  
Tropical Oceans ◽  
Subsurface Waters

Abstract. The Bay of Bengal (BoB) has long stood as a biogeochemical enigma, with subsurface waters containing extremely low, but persistent, concentrations of oxygen in the nanomolar range which – for some, yet unconstrained, reason – are prevented from becoming anoxic. One reason for this may be the low productivity of the BoB waters due to nutrient limitation and the resulting lack of respiration of organic material at intermediate waters. Thus, the parameters determining primary production are key in understanding what prevents the BoB from developing anoxia. Primary productivity in the sunlit surface layers of tropical oceans is mostly limited by the supply of reactive nitrogen through upwelling, riverine flux, atmospheric deposition, and biological dinitrogen (N2) fixation. In the BoB, a stable stratification limits nutrient supply via upwelling in the open waters, and riverine or atmospheric fluxes have been shown to support only less than one-quarter of the nitrogen for primary production. This leaves a large uncertainty for most of the BoB's nitrogen input, suggesting a potential role of N2 fixation in those waters. Here, we present a survey of N2 fixation and carbon fixation in the BoB during the winter monsoon season. We detected a community of N2 fixers comparable to other oxygen minimum zone (OMZ) regions, with only a few cyanobacterial clades and a broad diversity of non-phototrophic N2 fixers present throughout the water column (samples collected between 10 and 560 m water depth). While similar communities of N2 fixers were shown to actively fix N2 in other OMZs, N2 fixation rates were below the detection limit in our samples covering the water column between the deep chlorophyll maximum and the OMZ. Consistent with this, no N2 fixation signal was visible in δ15N signatures. We suggest that the absence of N2 fixation may be a consequence of a micronutrient limitation or of an O2 sensitivity of the OMZ diazotrophs in the BoB. Exploring how the onset of N2 fixation by cyanobacteria compared to non-phototrophic N2 fixers would impact on OMZ O2 concentrations, a simple model exercise was carried out. We observed that both photic-zone-based and OMZ-based N2 fixation are very sensitive to even minimal changes in water column stratification, with stronger mixing increasing organic matter production and export, which can exhaust remaining O2 traces in the BoB.

No N2 fixation in the Bay of Bengal?

2020 ◽  
Author(s):  
Carolin Löscher ◽  
Wiebke Mohr ◽  
Hermann Bange ◽  
Donald Canfield
Keyword(s):  
Primary Production ◽  
Water Column ◽  
Bay Of Bengal ◽  
Carbon Fixation ◽  
Monsoon Season ◽  
Stable Stratification ◽  
Water Column Stratification ◽  
Tropical Oceans ◽  
Matter Production ◽  
Subsurface Waters

<p>The Bay of Bengal (BoB) has long stood as a biogeochemical enigma with subsurface waters containing extremely low, but persistent, concentrations of oxygen (O<sub>2</sub>) in the nanomolar range which - for some, yet unconstrained reason- are prevented from becoming anoxic. One reason for this may be<br>the low productivity of the BoB waters due to nutrient limitation, and the resulting lack of respiration of organic material at intermediate waters. Thus, the parameters determining primary production are key to understanding what prevents the BoB from developing anoxia. Primary productivity in the sunlit surface layers of tropical oceans is mostly limited by the supply of reactive nitrogen through upwelling, riverine flux, atmospheric deposition, and biological dinitrogen (N<sub>2</sub>) fixation. In the BoB, a stable stratification limits nutrient supply via upwelling in the open waters, and riverine or atmospheric fluxes have been shown to support only less than one quarter of the nitrogen for primary production. This leaves a large uncertainty for most of the BoB’s nitrogen input, suggesting a potential role of N<sub>2</sub> fixation in those waters.<br>Here, we present a survey of N<sub>2</sub> fixation and carbon fixation in the BoB during the winter monsoon season. We detected a community of N<sub>2</sub> fixers comparable to other OMZ regions, with only a few cyanobacterial clades and a broad diversity of non-phototrophic N<sub>2</sub> fixers present throughout the water column (samples collected between 10 m and 560 m water depth). While similar communities of N<sub>2</sub> fixers were shown to actively fix N<sub>2</sub> in other OMZs, N<sub>2</sub> fixation rates were below the detection limit in our samples covering the water column between the deep chlorophyll maximum and the OMZ.<br>Consistent with this, no N<sub>2</sub> fixation signal was visible in δ<sup>15</sup>N signatures. We suggest that the absence of N<sub>2</sub> fixation may be a consequence of a micronutrient limitation or of an O<sub>2</sub> sensitivity of the OMZ diazotrophs in the BoB. To explore how the onset of N<sub>2</sub> fixation by cyanobacteria compared to nonphototrophic N<sub>2</sub> fixers would impact on OMZ O<sub>2</sub> concentrations, a simple model exercise was carried out. We observed that both, photic zone-based and OMZ-based N<sub>2</sub> fixation are very sensitive to even minimal changes in water column stratification, with stronger mixing increasing organic matter production and export, which would exhaust remaining O<sub>2</sub> traces in the BoB.       </p>

Further studies of plankton ecosystems in the eastern Indian Ocean. III. Numerical abundance and biomass

1977 ◽  
Vol 28 (5) ◽  
pp. 557 ◽  
Author(s):  
DJ Tranter ◽  
JD Kerr
Keyword(s):  
Indian Ocean ◽  
Monsoon Season ◽  
Time Of Day ◽  
Eastern Indian Ocean ◽  
Fish Eggs ◽  
The South ◽  
North West ◽  
Numerical Abundance ◽  
Eggs And Larvae ◽  
Fish Eggs And Larvae

The numerical abundance of 13 zooplankton taxa in the eastern Indian Ocean (meridian 110�E.) was examined in relation to some factors likely to control their distribution. Regression analysis showed that season, latitude (and their interaction), and time of day were frequently significant sources of variance. Decapoda, Amphipoda, fish eggs and larvae, Coelenterata and, sometimes, Copepoda and Euphausiacea were more abundant by night than by day. Numbers were generally high in late winter (June-September) and low in early summer, with a secondary peak, in some cases, in early autumn (March). Numbers were generally high at low latitudes (9-15�S.) and low at high latitudes (25-32�S.), one exception being fish eggs and larvae whose centre of abundance lay at 24-25�S. Seasonal periodicity was frequently in phase along the study section, numerical abundance reaching a peak 1-2 months after a general phytoplankton bloom at the onset of the south-east monsoon. There is no ready explanation why the subtropical regime should be in synchrony with that prevailing in the tropics, no subtropical source of nutrient enrichment being known which could match, for example, the Java Dome. An explanation for the observed tropical-subtropical synchrony was therefore sought in terms of interzonal advection. Data from a variety of sources showed that between May and August there was considerable enrichment not only at the Java Dome but also on the north-west Australian shelf. The area between North-West Cape and Port Hedland is the place where (plankton-feeding) humpback whales are known to gather. Sperm whales, on the other hand, congregate 1100-1300 km further to the south- west where the waters are rich in micronekton. The mass transport of upper waters during the south- east monsoon season suggests that these phenomena constitute a trophic sequence. The second zooplankton peak, in March, is the result of a summer algal bloom generated, perhaps, by remineralization of organic matter produced during the previous south-east monsoon season.

Interannual variability of the Eastern Indian Ocean with focus on the Ningaloo Niño and negative Indian Ocean Dipole event in 2010/2011

2020 ◽  
Author(s):  
Svenja Ryan ◽  
Caroline Ummenhofer ◽  
Glen Gawarkiewicz ◽  
Patrick Wagner ◽  
Markus Scheinert ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
General Circulation ◽  
Large Scale ◽  
Southern Oscillation ◽  
Mixed Layer Depth ◽  
Eastern Indian Ocean ◽  
Global Ocean ◽  
Relative Role ◽  
Study Region

<p>The dominant mode of sea surface temperature (SST) variability in the southeast Indian Ocean off the coast of Western Australia is called Ningaloo Niño/Niña. An unprecedented Ningaloo Niño, or marine heatwave, occurred during the austral summer of 2010/2011 with mean SSTs at 3°C above the long-term mean and had drastic impacts on the ecosystem. This event was attributed to a combination of an anomalous strong Leeuwin Current and high local air-sea heat fluxes. A number of local and remote forcing mechanisms have been investigated in recent years, however, little is known about the depth-structure of these ocean extremes and their general connections to large-scale ocean interannual to decadal variability. Using a suite of simulations with a high-resolution global Ocean General Circulation Model from 1958-2016, we investigate eastern Indian Ocean variability with focus on Ningaloo Niño and corresponding cold Ningaloo Niña events. In particular, we are interested in the impacts of large-scale ocean and climate variability, such as the Indonesian Throughflow, El Niño - Southern Oscillation and the Indian Ocean Dipole (IOD), on the study region. Spatial composites reveal large-scale surface and subsurface anomalies that extend from the western Pacific across the Indonesian Archipelago into the tropical eastern Indian Ocean. In particular, strong anomalies in temperature, salinity and mixed layer depth are found to the west of Sumatra and Java, a region that is generally strongly impacted by the IOD. We therefore investigate the connection with Ningaloo Niño/Niña events, at surface and subsurface, with a focus on 2010/2011 where a strong negative IOD event occurred prior to the unprecedented Ningaloo Niño. Furthermore, we find that major heatwaves in 2000 and 2011 are associated with pronounced fresh anomalies. Sensitivity experiments allow us to assess the relative role of buoyancy and wind-forcing as drivers of the observed patterns. Our work can provide valuable contributions for advancing the understanding of Ningaloo Niño/Niña drivers from surface to depth and regional to large scales.</p>

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