Occurrence, sources and risk assessment of polycyclic aromatic hydrocarbons in the coral reef waters of the Lakshadweep Archipelago, Arabian Sea

The compound effects of anthropogenic disturbances on global and local scales threaten coral reef ecosystems of the Arabian Sea. The impacts of organic pollutants on the coral reefs and associated organisms have received less attention and are consequently less understood. This study examines the background levels, sources, and ecological implications of polycyclic aromatic hydrocarbons (PAHs) in the coral reef ecosystems of Lakshadweep Archipelago. Water and particulate matter were collected from four coral Islands (Kavaratti, Agatti, Bangaram and Perumal Par) of Lakshadweep Archipelago during January and December 2022 and analysed for 15 PAHs priority pollutants. The 15 PAHs congeners generally ranged from 2.77 to 250.47 ng/L in the dissolved form and 0.44 to 6469.86 ng/g in the particulate form. A comparison of available data among the coral reef ecosystems worldwide revealed relatively lower PAHs concentrations in the Lakshadweep coral ecosystems. The isomeric ratios of individual PAH congeners and principal component analysis (PCA) indicate mixed sources of PAHs in the water column derived from pyrogenic, low-temperature combustion and petrogenic. The risk quotient (RQ) values in the dissolved form indicate moderate risk to the aquatic organisms, while they indicate moderate to severe risk in the particulate form.

Factors influencing nearshore hypoxia in the southeastern Arabian Sea: A sensor-based study

Seasonal upwelling and the associated incursion of hypoxic waters into the coastal zone is a widely studied topic over different upwelling zones. However, its persistence or variations over short time scales are poorly addressed. The present study, therefore, brings out a first report on hourly variations in the temperature, salinity and dissolved oxygen recorded by an environmental data buoy equipped with sensors, deployed in the nearshore waters of Alappuzha (southeastern Arabian Sea) from April to August 2022. The characteristic feature of the Alappuzha coast is the development of mud banks during the southwest monsoon, providing a tranquil environment suitable for continuous sensor-based measurements when the sea remains turbulent elsewhere. The results showed that despite an advance in the upwelling intensity, there is a significant variation in the oxygen concentration in the study domain on a diurnal scale. In general, the nearshore region was under hypoxia during the first half of the day (00:00 to 12:00 h), which increased steadily to reach normoxic and supersaturated levels during the rest of the day (12:00 to 24:00 h). Statistical analysis showed that winds significantly correlate to the coastal environment's subsurface oxygen concentration. During the morning hours, the wind was weak, and the water column remained stratified over the subsurface hypoxic water layer. The situation changed in the afternoon (12:00 h onwards), as there was a steady increase in the local wind speed (>5 m/s), which was sustained during the rest of the day. A local wind speed >5 m/s can disturb the stratification and enhance the mixing process from 12:00 to 24:00 h. The total kinetic energy of 11.5 J/m3 is the threshold for this oxygen supersaturation. These findings emphasize the role of wind-induced mixing in alleviating coastal hypoxia, highlighting the need for further biogeochemical and ecological investigations into the impacts of alternating oxic-hypoxic conditions in nearshore waters.

Characterization of phytoplankton functional groups in a tropical shellfish harvesting estuary (Ashtamudi) and adjacent nearshore waters (southwest coast of India)

A pioneering study on phytoplankton marker pigments, by adopting the HPLC-CHEMTAX analytical approach, was carried out in one of the major shellfish harvesting estuaries (Ashtamudi estuary-AE) on the southwest coast of India and also its adjacent nearshore waters (< 20 m depth) to study the dynamics of phytoplankton functional groups (PFGs). The AE, in general, appeared to be warm (> 29 °C) during the non-monsoon seasons, along with the prevalence of higher salinity (> 25) and NH₄-N (> 5 µM) levels. However, during the summer monsoon (SM), the prevailing substantial river influx converted the AE into a low salinity (< 10) dominated system, provided with enhanced levels of NO₃-N (4.6-12.6 µM) and PO₄-P (0.2-1.4 µM), specifically on its upper reaches. The dissolved inorganic nitrogen (DIN) in the AE was mainly comprised of ammonium (NH₄-N), approximately up to ~ 81.8% of the DIN, regardless of seasons, which signifies the eutrophic state of the estuary, the upstream sampling locations, in particular. Concerning the phytoplankton community, a pronounced spatio-temporal variation in chlorophyll a biomass was discernible in the AE, with an exceptional increase (6.4-12.1 mg m^-3) during the SIM period. The prevalence of a conspicuous increase in chlorophyll a (av. > 5 mg m^-3) along with enhanced zeaxanthin (av. > 1.5 mg m^-3) recorded in the AE during the non-monsoon (specifically SIM period) season apparently signified the characteristic governance of cyanobacterial community. During the SM period, the estuary sustained more or less similar concentrations of certain marker pigments, i.e. alloxanthin, zeaxanthin, fucoxanthin and chl b, which representing the co-occurrence of cryptophytes, cyanobacteria, diatoms and chlorophytes, respectively. In contrast, the nearshore waters, wherein enhanced nitrate (NO₃-N) and phosphate (PO₄-P) levels prevailed, irrespective of seasons, sustained dominance of fucoxanthin over other marker pigments, which indicated the numerical supremacy of diatoms. The CHEMTAX analysis, adopted for estimating the chlorophyll a equivalents of various PFGs, corroborated the supremacy of cyanobacterial derived chlorophyll a in the estuary, and it was conspicuous during the non-monsoonal seasonal periods. Even though the estuary has shown remarkable spatio-temporal hydrographic inconsistencies, that variability was not much operative in generating extreme changes in the nutrient components and subsequent phytoplankton community compositions. From the conspicuous increase in N:P and Si:P ratios, resulting mainly from the low levels of P, it can be concluded that the AE has been a P-limited system for phytoplankton growth (especially for large-sized phytoplankton, e.g. diatoms and dinoflagellates), mainly during the non-monsoonal seasonal periods. Perhaps, this P-limitation, along with the prevalence of warm water column and enhanced NH₄-N levels, could be the potential causes of the preponderance of cyanobacterial populations in the AE.

Acceptance of COVID-19 Vaccine among Dental Professionals: A Cross-Sectional Study among Practitioners, Residents, and Students

Introduction:

The COVID-19 pandemic spread rapidly across the world, prompting governments to impose lengthy restrictions on both movement and trade. While lockdowns reduce the prevalence of COVID-19 disease, they may have a negative impact on the economy and job levels. Dental medicine has been one of the most severely impacted industries during this crisis. Dental professionals are exposed to environments with high levels of occupational hazards, additional risks of viral exposure, and transmission.

Methods:

We analyzed 705 anonymous questionnaires filled out by dentists, dental students, and postgraduate students about their willingness to consider a new SARS-CoV-2 vaccine.

Results:

Our findings show a statistically significant relationship between an individual's unemployment rate and their ability to be immunized with a SARS-CoV-2 vaccine.

Conclusion:

As part of the global vaccination program's alertness, these data may be used to forecast patterns in vaccine adoption or denial depending on economic burden during the COVID-19 pandemic by various industries.

Phosphorus cycling from a coastal upwelling zone in the Southeastern Arabian Sea

The present study examined the seasonal cycling of phosphorous (P) along the southwest coast of India (SWCI) based on two cruises during the southwest monsoon (SWM) and northeast monsoon (NEM) of 2018. During SWM, the entire SWCI experienced intense upwelling manifested by the incursion of cold, nutrient-rich, and hypoxic waters. During NEM, the region was transformed into a warm, well-oxygenated and nutrient-deplete environment. Dissolved inorganic phosphorus (DIP) was significantly high in the subsurface during SWM due to its release from sediments. The sediment P was high and showed an increasing trend towards the south, principally dependent on the sediment texture, organic carbon, and Fe concentrations. Bioavailable P, the sum of exchangeable (P_Ex) and reducible (P_Fe) fractions, was almost consistent (5-20%) over seasons, though P_Fe showed a marked reduction during SWM. Authigenic fraction (P_Aut) was the most dominant (46%), followed by detrital (P_Det 41%) and residual (P_Res 8%) fractions. Principal component analysis (PCA) of geochemical parameters for SWM was indicative of the high dissolution of Fe (oxy)hydroxides under hypoxia releasing P and its complexation with organic matter and Fe. PCA results for the NEM were different, as it indicated increased preservation of P-associated organic matter and Fe, alternately favouring the formation of P_Aut in sediments. The study's significance is the observation that the bottom water oxygen concentration can significantly influence sedimentary P cycling in tropical coastal upwelling zones.