The distribution of chlorophyll a in the tropical eastern Indian Ocean in austral summer

2012 ◽  
Vol 31 (5) ◽  
pp. 146-159 ◽  
Author(s):  
Lisha Hong ◽  
Chunsheng Wang ◽  
Yadong Zhou ◽  
Mianrun Chen ◽  
Hongbin Liu ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Chlorophyll A ◽  
Austral Summer ◽  
Eastern Indian Ocean

scholarly journals VARIABILITY OF SEA SURFACE TEMPERATURE (SST) AND CHLOROPHYLL-A (CHL-A) CONCENTRATIONS IN THE EASTERN INDIAN OCEAN DURING THE PERIOD 2002–2017

2019 ◽  
Vol 16 (1) ◽  
pp. 55
Author(s):  
Michelia Mashita ◽  
Jonson Lumban-Gaol
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Chlorophyll A ◽  
Sea Surface ◽  
Asia Pacific ◽  
Eastern Indian Ocean ◽  
Positive Anomaly ◽  
Chl A ◽  
Annual Variability

We analysed the variability of sea surface temperature (SST) and chlorophyll-a concentration (Chl-a) in the eastern Indian Ocean (EIO). We used monthly mean Chl-a and SST data with a 4-km spatial resolution derived from Level-3 Aqua Moderate-resolution Imaging Spectroradiometer (MODIS) distributed by the Asia-Pacific Data-Research Center (APDRC) for the period 2002–2017. Wavelet analysis shows the annual and interannual variability of SST and Chl-a concentration in the EIO. The annual variability of SST and Chl-a is influenced by monsoon systems. During a southeast monsoon, SST falls while Chl-a increases due to upwelling. The annual variability of SST and Chl-a is also influenced by the Indian Ocean Dipole (IOD). During positive phases of the IOD (2006, 2012 and 2015), there was more intense upwelling in the EIO caused by the negative anomaly of SST and the positive anomaly of Chl-a concentration.

scholarly journals The Horizontal Distribution of Siliceous Planktonic Radiolarian Community in the Eastern Indian Ocean

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3502
Author(s):  
Sonia Munir ◽  
John Rogers ◽  
Xiaodong Zhang ◽  
Changling Ding ◽  
Jun Sun
Keyword(s):  
Indian Ocean ◽  
Chlorophyll A ◽  
Mixed Layer ◽  
Diversity Index ◽  
Horizontal Distribution ◽  
Eastern Indian Ocean ◽  
Entire Area ◽  
Factors Affecting ◽  
Major Factors ◽  
First Time

The plankton radiolarian community was investigated in the spring season during the two-month cruise ‘Shiyan1’ (10 April–13 May 2014) in the Eastern Indian Ocean. This is the first comprehensive plankton tow study to be carried out from 44 sampling stations across the entire area (80.00°–96.10° E, 10.08° N–6.00° S) of the Eastern Indian Ocean. The plankton tow samples were collected from a vertical haul from a depth 200 m to the surface. During the cruise, conductivity–temperature–depth (CTD) measurements were taken of temperature, salinity and chlorophyll a from the surface to 200 m depth. Shannon–Wiener’s diversity index (H’) and the dominance index (Y) were used to analyze community structure. There was a total of 168 plankton species, composed of Acantharia, Phaeodaria, Polycystina, Collodaria and Taxopodida (monospecific—Sticholonche zanclea, Hertwig is the only recognized species). Hence, it included both celestine-based and siliceous organisms, which are also described here for the first time from this region. Total radiolarians ranged from 5 to 5500 ind/m−3, dominated by co-occurrences of Sphaerozoum punctatum and Stichonche zanclea species at the south-equator zone (SEQ)-transect 80° E and equator zone (EQ)-transect Lati-0. The possible environmental variables were tested through RDA analysis; although no result was obtained for the full species dataset, the samples from the equatorial transect related strongly to mixed-layer chlorophyll a concentration and those of a north–south transect to surface silicate concentrations or mixed-layer nitrate were significantly correlated (p < 0.01) to the radiolarian community. Our results indicate that the silicate and chlorophyll-a concentrations are the two major factors affecting the radiolarian distribution along two of the investigated transects (southern equator and equator) in the study area.

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

Variability in reproductive investment of skipjack tuna (Katsuwonus pelamis) in relation to the ocean - climate dynamics in the tropical eastern Indian Ocean

2012 ◽  
Vol 63 (8) ◽  
pp. 695 ◽  
Author(s):  
Yu Kanaji ◽  
Toshiyuki Tanabe ◽  
Hikaru Watanabe ◽  
Tatsuki Oshima ◽  
Makoto Okazaki
Keyword(s):  
Indian Ocean ◽  
Gonadosomatic Index ◽  
Subsurface Layer ◽  
Austral Summer ◽  
Eastern Indian Ocean ◽  
Skipjack Tuna ◽  
Katsuwonus Pelamis ◽  
Allocation Pattern ◽  
Ocean Climate ◽  
The Indian Ocean

The Indian Ocean is characterised by significant climatic and oceanographic variability such as the seasonal monsoon and the decadal and inter-annual oscillation of the Indian Ocean Dipole (IOD). Understanding the effects of ocean–climate variability on marine top predators is important for both fisheries and ecosystem management. To test the hypothesis that variability in surface and subsurface temperature affects the annual reproductive cycles of skipjack tuna (Katsuwonus pelamis) in the tropical eastern Indian Ocean, we examined the seasonal and inter-annual variations of the gonadosomatic index (GSI) and determined hatch date by using otolith microstructure analysis. The GSI tended to be higher in January–February during the north-eastern monsoon when seawater cooling at the subsurface layer is induced by the seasonal inflow of the South Equatorial Countercurrent (SECC). The mode of the hatch-month distribution was also detected in that season. The generalised linear model (GLM) resulted in a dome-shaped quadratic relationship, with a peak GSI between 24°C and 26°C occurring at a depth of 50 m during austral summer. These findings indicate that seasonal monsoons and associated changes in oceanographic conditions strongly affect the energy-allocation pattern of skipjack tunas.

scholarly journals Circulation pattern controls of wet days and dry days in Free State, South Africa

2021 ◽  
Author(s):  
Chibuike Chiedozie Ibebuchi
Keyword(s):  
South Africa ◽  
Indian Ocean ◽  
Atmospheric Circulation ◽  
Southern Africa ◽  
Austral Summer ◽  
Free State ◽  
Austral Spring ◽  
Study Region ◽  
Southwest Indian Ocean ◽  
South Indian

AbstractAtmospheric circulation is a vital process in the transport of heat, moisture, and pollutants around the globe. The variability of rainfall depends to some extent on the atmospheric circulation. This paper investigates synoptic situations in southern Africa that can be associated with wet days and dry days in Free State, South Africa, in addition to the underlying dynamics. Principal component analysis was applied to the T-mode matrix (variable is time series and observation is grid points at which the field was observed) of daily mean sea level pressure field from 1979 to 2018 in classifying the circulation patterns in southern Africa. 18 circulation types (CTs) were classified in the study region. From the linkage of the CTs to the observed rainfall data, from 11 stations in Free State, it was found that dominant austral winter and late austral autumn CTs have a higher probability of being associated with dry days in Free State. Dominant austral summer and late austral spring CTs were found to have a higher probability of being associated with wet days in Free State. Cyclonic/anti-cyclonic activity over the southwest Indian Ocean, explained to a good extent, the inter-seasonal variability of rainfall in Free State. The synoptic state associated with a stronger anti-cyclonic circulation at the western branch of the South Indian Ocean high-pressure, during austral summer, leading to enhanced low-level moisture transport by southeast winds was found to have the highest probability of being associated with above-average rainfall in most regions in Free State. On the other hand, the synoptic state associated with enhanced transport of cold dry air, by the extratropical westerlies, was found to have the highest probability of being associated with (winter) dryness in Free State.

scholarly journals Impact of the Strong Downwelling (Upwelling) on Small Pelagic Fish Production during the 2016 (2019) Negative (Positive) Indian Ocean Dipole Events in the Eastern Indian Ocean off Java

Climate ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 29
Author(s):  
Jonson Lumban-Gaol ◽  
Eko Siswanto ◽  
Kedarnath Mahapatra ◽  
Nyoman Metta Nyanakumara Natih ◽  
I Wayan Nurjaya ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Pelagic Fish ◽  
Eastern Indian Ocean ◽  
Fish Production ◽  
Small Pelagic Fish ◽  
Field Surveys ◽  
Chl A ◽  
Positive Indian Ocean Dipole ◽  
The Impact

Although researchers have investigated the impact of Indian Ocean Dipole (IOD) phases on human lives, only a few have examined such impacts on fisheries. In this study, we analyzed the influence of negative (positive) IOD phases on chlorophyll a (Chl-a) concentrations as an indicator of phytoplankton biomass and small pelagic fish production in the eastern Indian Ocean (EIO) off Java. We also conducted field surveys in the EIO off Palabuhanratu Bay at the peak (October) and the end (December) of the 2019 positive IOD phase. Our findings show that the Chl-a concentration had a strong and robust association with the 2016 (2019) negative (positive) IOD phases. The negative (positive) anomalous Chl-a concentration in the EIO off Java associated with the negative (positive) IOD phase induced strong downwelling (upwelling), leading to the preponderant decrease (increase) in small pelagic fish production in the EIO off Java.

scholarly journals Variability in the Mozambique Channel Trough and Impacts on Southeast African Rainfall

2020 ◽  
Vol 33 (2) ◽  
pp. 749-765 ◽  
Author(s):  
Rondrotiana Barimalala ◽  
Ross C. Blamey ◽  
Fabien Desbiolles ◽  
Chris J. C. Reason
Keyword(s):  
Indian Ocean ◽  
Austral Summer ◽  
Western Indian Ocean ◽  
Strong Relationship ◽  
Ocean Basin ◽  
Moist Convection ◽  
South Indian Ocean ◽  
Mozambique Channel ◽  
Mascarene High ◽  
South Indian

AbstractThe Mozambique Channel trough (MCT) is a cyclonic region prominent in austral summer in the central and southern Mozambique Channel. It first becomes evident in December with a peak in strength in February when the Mozambique Channel is warmest and the Mascarene high (MH) is located farthest southeast in the Indian Ocean basin. The strength and the timing of the mean MCT are linked to that of the cross-equatorial northeasterly monsoon in the tropical western Indian Ocean, which curves as northwesterlies toward northern Madagascar. The interannual variability in the MCT is associated with moist convection over the Mozambique Channel and is modulated by the location of the warm sea surface temperatures in the south Indian Ocean. Variability of the MCT shows a strong relationship with the equatorial westerlies north of Madagascar and the latitudinal extension of the MH. Summers with strong MCT activity are characterized by a prominent cyclonic circulation over the Mozambique Channel, extending to the midlatitudes. These are favorable for the development of tropical–extratropical cloud bands over the southwestern Indian Ocean and trigger an increase in rainfall over the ocean but a decrease over the southern African mainland. Most years with a weak MCT are associated with strong positive south Indian Ocean subtropical dipole events, during which the subcontinent tends to receive more rainfall whereas Madagascar and northern Mozambique are anomalously dry.

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