Barnacle larval transport in the Mandovi–Zuari estuarine system, central west coast of India

A two-dimensional hydrodynamic and particle tracking model was used to estimate the dispersion and retention of barnacle larvae from their possible spawning sites in a tropical monsoon-influenced estuarine system (central west coast of India). Validation of the hydrodynamic simulations yielded a good match with field measurements. The pattern of larval dispersal in the region varied with the winds and currents. The seasonal changes in abundance could be attributed to physical forcing and weather conditions. The extent of barnacle larval dispersal from spawning sites varied from 10 to 78 km for different sites and seasons. During a 24-h cycle, the larval abundance showed one to two peaks in the estuarine area. The increased larval abundance is favored by the flood currents, pushing the larvae into the estuary. Physical forcing in the region helps in transport of the larvae from their spawning sites hugging to the coast and contributing to the population within the estuary. Field observations and numerical experiments suggest the occurrence of higher larval abundance in the estuary during post-monsoon. The dispersal pattern indicated that the barnacle population present in the estuary is well mixed, and with a seasonally changing pattern

The maxima in northerly wind speeds and wave heights over the Arabian Sea, the Arabian/Persian Gulf and the Red Sea derived from 40 years of ERA5 data

Recent studies point out the importance of northerly winds and waves in the Arabian Sea, especially those due to shamal and makran events in addition to the northeast monsoon system. We have analyzed climatology and trends of northerly maximum wind speed and significant wave height (Hs) in the Arabian Sea and the connected marginal seas, Arabian/Persian Gulf and the Red Sea, during non-monsoon season derived from 40 years of ERA5 wind and wave data, and estimated monthly, annual and decadal extreme climate and their trends. The study brings out an increasing trend in the northerly maximum wind speed (0.8–1.2 cm/s/year) and Hs (0.42–0.88 cm/year) in the southern and central Arabian Sea, which is consistent with the global trend in extreme wind speed and Hs. The northern Arabian Sea including the Sea of Oman exhibits significant decreasing trend in northerly maximum wind speed (− 1.4 cm/s/year) and Hs (− 0.67 cm/year), while the Gulf and the Red Sea exhibit sectorial contrasting trend, indicating the dominance of localized effects in modifying the regional climate. Distinct features identified in the climate and trends of northerly winds and waves are further discussed.The project is funded under the IRCC International Research Co-Fund Collaboration Program of QU and NIO, executed through ORS, QU (IRCC-2019-002)

Co-existence of wind seas and swells along the west coast of India during non-monsoon season

An attempt has been made to understand the co-existence of wind seas and swells along the west coast of India during non-monsoon season. Wave data were collected in different years during non-monsoon season (off Goa during May 2005, off Ratnagiri during January–February 2008 and off Dwarka during December 2007–January 2008), which is fairly a calm weather season along these regions. Diurnal variation in wave parameters is noticeable along the central west coast of India (off Goa and Ratnagiri), which is due to the interaction of multidirectional waves (both wind seas and swells) of varying magnitudes and frequencies. Swells are predominantly mature (91%) and old (88%) during late pre-monsoon and post-monsoon seasons, respectively. Sea Swell Energy Ratio quantifies wind sea, swell and mixed seas prevailing in these regions during non-monsoon season. Intermodal distance (ID) between the energy peaks is moderately separated during non-monsoon season, whereas, during the shamal events, energy peaks are very close to each other (ID ∼ 0). However, pure wind seas (ID ∼ 1) are weakly present and found to co-exist with the swells almost all the time during non-monsoon season. Wind sea growth has been found while the swell propagates opposite to the direction of the wind and wind sea. Wind seas have minimum angular spreads in multimodal state. Under low winds, the interaction between wind sea and swell dominates and thereby the multimodal state reduces to unimodal state. The fetch available for the evolution of the wind sea spectrum has been estimated, and it is found to be less than 150 km. For the fetch limited condition, a non-dimensional empirical relation has been derived relating the significant wind sea height in terms of wind speed and peak wind sea period, and this relation fits for the west coast of India

Role of shamal and easterly winds on the wave characteristics off Qatar, central Arabian Gulf

Waves in the Arabian Gulf (Gulf) are dominated by shamal winds during winter and early summer. Although wave characteristics in the Gulf are broadly studied, features associated with various wind systems are not explicitly covered, especially in the Exclusive Economic Zone (EEZ) of Qatar. In this study, we analyzed the wave parameters measured off Fuwairit, north coast of Qatar during 29 October – 26 November 2019 to identify the features associated with different wind systems. The analyses have been further extended to the Gulf using the reanalysis waves obtained from the COPERNICUS Marine Environment Monitoring Services (CMEMS) to describe the monthly, seasonal and annual characteristics. Results indicate that Nashi winds influence the east and northeast coasts of Qatar with higher waves than those generated by shamal winds. We find exceptional easterly (Nashi) waves during March 2019 contributing to the highest monthly mean Hs, which is a deviation from the known long-term wave climate of the Gulf.This work was jointly carried out under the IRCC International Research Co-Fund Collaboration Program of QU and CSIR-NIO, executed through Office of Research Support (ORS), QU (IRCC-2019-002)

Not Available

Not AvailableA two-dimensional hydrodynamic and particle tracking model was used to estimate the dispersion and retention of barnacle larvae from their possible spawning sites in a tropical monsoon-influenced estuarine system (central west coast of India). Validation of the hydrodynamic simulations yielded a good match with field measurements. The pattern of larval dispersal in the region varied with the winds and currents. The seasonal changes in abundance could be attributed to physical forcing and weather conditions. The extent of barnacle larval dispersal from spawning sites varied from 10 to 78 km for different sites and seasons. During a 24-h cycle, the larval abundance showed one to two peaks in the estuarine area. The increased larval abundance is favored by the flood currents, pushing the larvae into the estuary. Physical forcing in the region helps in transport of the larvae from their spawning sites hugging to the coast and contributing to the population within the estuary. Field observations and numerical experiments suggest the occurrence of higher larval abundance in the estuary during post-monsoon. The dispersal pattern indicated that the barnacle population present in the estuary is well mixed, and with a seasonally changing pattern.Not Availabl

Numerical simulations of barnacle larval dispersion coupled with field observations on larval abundance, settlement and recruitment in a tropical monsoon influenced coastal marine environment

Larval abundance in an area depends on various factors which operate over different spatial and temporal scales. Identifying the factors responsible for variations in larval supply and abundance is important to understand the settlement and recruitment variability of their population in a particular area. In view of this, observations were carried out to monitor the larval abundance, settlement and recruitment of barnacles on a regular basis for a period of two years. The results were then compared with the numerical modelling studies carried out along the west coast of India. Field observations of larval abundance showed temporal variations. The least abundance of larvae was mostly observed during the monsoon season and the peak in abundance was mostly observed during the pre-monsoon season. Numerical simulations also showed a seasonal change in larval dispersion and retention patterns. During pre-monsoon season the larval movement was mostly found towards south and the larvae released from the northern release sites contributed to larval abundance within the estuaries, whereas during the monsoon season the larval movement was mostly found towards north and the larvae released from southern release sites contributed to larval abundance within the estuary. During post-monsoon season, the larval movement was found towards the north in the beginning of the season and is shifted towards the south at the end of the season, but the movement was mostly restricted near to the release sites. Larval supply from the adjacent rocky sites to the estuaries was higher during the pre-monsoon season and the retention of larvae released from different sites within the estuaries was found to be highest during the late post-monsoon and early pre-monsoon season. Maximum larval supply and retention during the pre-monsoon season coincided with maximum larval abundance, settlement and recruitment of barnacles observed in the field studies. These observations showed that the pattern of larval dispersion and retention in the region is predominantly driven by local hydrodynamics operating in the vicinity. Linking larval dispersion and retention with settlement and recruitment of barnacles indicated that the processes are mainly influenced by wind and resultant current patterns. These findings facilitate unravelling the processes operating in the region and to understand the distribution pattern of the intertidal organisms in general in this tropical environment influenced by monsoons

Contributions of Fourier transform infrared spectroscopy in microplastic pollution research: A review

© 2020 Taylor & Francis Group, LLC. Fourier transform infrared (FTIR) spectroscopy has been extensively used in microplastic (MP) pollution research since 2004. The aim of this review is to discuss and highlight the recent advances in FTIR (spectroscopy and chemical imaging) techniques that are used to characterize various polymer types of MPs and to trace their fate and transport in different environmental matrices. More than 400 research papers dealing with FTIR techniques in MP pollution research, which are published between January 2010 and December 2019, have been identified from the Scopus and Web of Science databases. The MPs present in sediment, water (marine and freshwater), biota, air/dust, waste water treatment plants and salt are further classified according to (1) characterization and identification, (2) weathering and aging, (3) ecotoxicology, and (4) analytical methods. The results revealed that the ATR-FTIR technique is mostly used to identify and characterize the MPs found in water and sediment. The µFTIR (FTIR imaging) is extensively used to study the ingestion of MPs in biota (both marine and freshwater). In this article, we have summarized the current knowledge of application of FTIR spectroscopy to MP research and provided insights to future challenges for understanding the risk of MPs

History of a disaster: A baseline assessment of the Wakashio oil spill on the coast of Mauritius, Indian Ocean

Oil spills from tanker ships provide adverse and irreversible impacts of a pollutant over coastal and marine environments. Using Sentinel-1 and 2 satellite images, this baseline paper presents the detection, assessment, and monitoring of the aground and further oil spill from the Wakashio ship of August 06, 2020, on the Mauritius coast. The oil spill started on August 06, after cracks developed on the hull, and continued until the total breakup of the ship on August 15, 2020. Data shows displacements in ship position of about 100 m, and a maximum change of 80° in orientation (from NS to NE). The remote sensing results were validated using met-ocean observations and reanalysis, which showed winds, waves, and tides of high magnitude at the accident site during the incident period. Analysis of the results of this event using REAS and CMEMS data indicate their usefulness to study similar future oil spills events.This work was supported by the Qatar University's International Research Collaboration Co-Funds project (IRCC-2019-002)