Oil pollution in Chilika lagoon: An anthropogenic threat to biodiversity

Chilika lagoon is situated on the east coast of India and is spread over three districts of Odisha, namely Puri, Khordha and Ganjam. The water spread area varies between 1165 and 906sq.km during monsoon and summer respectively. It is a hot spot for biodiversity, and the largest wintering ground for migratory avian guests on the Indian sub-continent

Cyclone Phailin enhanced the productivity following its passage: evidence from satellite data

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Empirical algorithm to estimate the average cosine of underwater light field at 490 nm

The average cosine of the underwater light field μ(λ), where λ is the wavelength, is an apparent optical property (AOP) that describes the angular distribution of radiance at a given point in water. Here, we present a simple algorithm to determine the average cosine at 490 nm, μ(490), which was developed using the measured optical parameters from the eastern Arabian Sea and coastal waters off Goa. The algorithm is validated using measured optical parameters. This algorithm, based on a single optical parameter, performed better compared with other empirical algorithms in determining the average cosine of underwater light field. The absorption coefficient at 490 nm, derived as an application of μ(490), compared well with the synthetic optical data and optical data measured from other regions

The interplay between submesoscale instabilities and turbulence in the surface layer of the Bay of Bengal

The Air-Sea Interactions Regional Initiative (ASIRI) aims to understand vertical fluxes of momentum and heat across the surface layer in the Bay of Bengal. As the mesoscale and submesoscale eddies redistribute freshwater input over saline water of the bay, they influence the vertical distribution of salinity and thus impact air-sea fluxes. This study reports on numerical simulations performed to investigate processes that can lead to the observed vertical structure of stratification near the ocean surface. Processes are explored at multiple lateral scales, ranging from a few meters to tens of kilometers, to elucidate how the interplay among large-scale motion, submesoscale instabilities, and small-scale turbulent motion affects the surface layer

Comparing the spatio-temporal variability of remotely sensed oceanographic parameters between the Arabian Sea and Bay of Bengal throughout a decade

The spatio-temporal variability of sea-surface temperature (SST), photosynthetically active radiation (PAR), chlorophyll-a (Chl-a), particulate organic carbon (POC) and particulate inorganic carbon (PIC) was evaluated in the Arabian Sea (ABS) and Bay of Bengal (BoB), from July 2002 to November 2014 by means of remotely sensed monthly composite Aqua MODIS level-3 data having a spatial resolution of 4.63 km. Throughout the time period under consideration, the surface waters of ABS (27.76 ± 1.12°C) were slightly cooler than BoB (28.93 ± 0.76°C); this was observed during all the seasons. On the contrary, the availability of PAR was higher in ABS (45.76 ± 3.41 mol m-2 d-1) compared to BoB (41.75 ± 3.75 mol m-2 d-1), and its spatial dynamics in the two basins was mainly regulated by cloud cover and turbidity of the water column. The magnitude and variability of Chl-a concentration were substantially higher in ABS (0.487 ± 0.984 mg m-3), compared to BoB (0.187 ± 0.243 mg m-3), and spatially higher values were observed near the coastal waters. Both POC and PIC exhibited higher magnitudes in ABS compared to BoB; however, the difference was substantially high in case of POC. None of the parameters showed any significant temporal trend during the 12-year span, except PIC, which exhibited a significant decreasing trend in ABS

Response of surface chlorophyll to aerosol dust input in the Central Arabian Sea

The decadal trends in satellite-derived surface chlorophyll in conjunction with Aerosol Optical Depth (AOD) are explored in a unique area in the central Arabian Sea, known to mimic High Nutrient and Low Chlorophyll (HNLC) like conditions during late summer monsoon. The analysis indicates two recurring seasonal blooms, possibly associated with distinct biogeochemical processes in the studied region. Furthermore, the mineral dust deposition in July every year coincides with one such increase in surface chlorophyll followed by a lag period until winter monsoon. This rapid increase in the phytoplankton biomass just after the aeolian input is possibly due to an enhancement in soluble iron within the mixed layer, as suggested by AOD dust data. Most likely, this rapid increase in biomass may induce further depletion of soluble iron leading to HNLC-like conditions during the late Summer Monsoon, as reported earlier. This hypothesis is consistent with the satellite observation, which shows a decrease in surface chlorophyll during subsequent months until the convective mixing between December – January (winter monsoon). The study reveals that the presence of the HNLC region in the central Arabian Sea during the summer monsoon is not perennial like the Southern Ocean. Instead, it is a transient phenomenon primarily controlled by aerosol deposition and rapid uptake of soluble iron, which facilitate the diatom blooms as suggested by the recent output from the NASA Ocean Biogeochemical Model (NOBM)

New light for time series: international collaboration in ship-based ecosystem monitoring.

Ship-based biogeochemical and ecological time series are one of the most valuable tools to characterize and quantify ocean ecosystems. These programs continuously provided major breakthroughs in understanding ecosystem variability, allow quantification of the ocean carbon cycle, and help understand the processes that link biodiversity, food webs, and changes in services that benefit human societies. A quantum jump in regional and global ocean ecosystem science can be gained by aggregating observations from individual time series that are distributed across different oceans and which are managed by different countries. The collective value of these data is greater than that provided by each time series individually. However, maintaining time series requires a commitment by the science community and sponsor agencies.. Based on the success of existing initiatives, e.g. ICES and SCOR working groups, IOC-UNESCO launched the International Group for Marine Ecological Time Series (IGMETS, http://igmets.net) to promote collaborations across different individual projects, and jointly look at holistic changes within different ocean regions. The effort explores the reasons and connections for changes in phytoplankton and zooplankton at a global level and identifies locations where particularly large changes may be ocurring. This compilation will facilitate better coordination, communication, and data intercomparability among time series.IEO (RADIALES) IOC-UNESC

Heterogeneous microbial oceanographic environments: Application of GIS technology in deciphering of microenvironment scenarios off the central west coast of India

In the vast oceanic microbial environment of 2468.83km 2, GIS modeling techniques involving sixty query steps, enabled the deciphering of Microenvironments as low as 1.19km 2 to 38.6 km 2 for the summer of 2004 and in case of summer 2005 where 84 query steps were involved to decipher Microenvironments of 10.55km 2 to 25.94km 2. Thirtythree sampling stations were established between Betul to Ankola off the central west coast of India accounting for a spatial coverage of 2468.83km 2. GIS query-modeling investigation was carried out using spatial layers of depth, optical parameters (k-Irradiance attenuation Coefficient, c-Beam attenuation coefficient), sediment size parameters (Sediment Mean Size and Sediment Sorting) and Benthic Foraminifera Suborders (Rotaliina, Textulariina, Miliolina, Lagenina). Foraminifera have been used as a surrogate parameter. However, any microbial parameter could proxy for foraminifers providing for the numerical deciphering of microenvironments. This is suggestive of the assimilation of GIS technology for a better appreciation of microbial oceanography

BoBBLE: ocean-atmosphere interaction and its impact on the South Asian monsoon

The Bay of Bengal (BoB) plays a fundamental role in controlling the weather systems that make up the South Asian summer monsoon system. In particular,the southern BoB has cooler sea surface temperature (SST) that influence ocean-atmosphere interaction and impact on the monsoon. Compared to the southeast, the southwestern BoB is cooler, more saline, receives much less rain, and is influenced by the Summer Monsoon Current(SMC). To examine the impact of these features on the monsoon, the BoB Boundary Layer Experiment (BoBBLE) was jointly undertaken by India and the UK during June–July 2016. Physical and bio-geochemical observations were made using a CTD, five ocean gliders, a uCTD, a VMP, two ADCPs, Argo floats, drifting buoys, meteorological sensors and upper air radiosonde balloons. The observations were made along a zonal section at 8◦N between 85.3◦E and 89◦E with a 10-day time series at 89◦E, 8◦N. This paper presents the new observed features of the southern BoB from the BoBBLE field program, supported by satellite data. Key results from the BoBBLE field campaign show the Sri Lanka Dome and the SMC in different stages of their seasonal evolution and two freshening events during which salinity decreased in the upper layer leading to the formation of thick barrier layers. BoBBLE observations were taken during a suppressed phase of the intraseasonal oscillation; they captured in detail the warming of the ocean mixed layer and preconditioning of the atmosphere to convection

<span style="font-size:15.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: "Times New Roman";mso-ansi-language:EN-US;mso-fareast-language:EN-US; mso-bidi-language:HI;mso-bidi-font-weight:bold" lang="EN-US">Spatio-Temporal Distribution of Physico-Chemical Parameters and Chlorophyll-<i style="mso-bidi-font-style:normal">a</i> in Chilika Lagoon, East Coast of India</span>

614-627<span style="font-size:9.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" "times="" roman";mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:hi"="" lang="EN-US">Present study contains the current status of Chilika Lagoon water quality during pre-monsoon, monsoon and post-monsoon seasons of the year 2012. Spatial and seasonal distributions of water quality parameters viz. WT, pH, Salinity, DO, TSM, Chl-a and inorganic nutrients (NO , NO , NH, PO, SiO) were examined in this study. Twenty locations were selected covering all the ecological sectors of the lagoon. Study reveals significant spatio-temporal variation in water quality parameters. The pH of the lagoon was found to be slightly alkaline. DO concentration was controlled by photosynthetic activities of autotrophs. Results of one-way ANOVA indicated spatio-temporal variation in the nutrients especially NH  and SiO (p  was found below the pollution limit for aquatic lives. Among the nutrients SiO, was the most influencing factor regulating phytoplankton production of the lagoon throughout the year.  However, NH was found as the second influencing factor for distribution of Chl-a