K. C. Sahu

Coastal Vulnerability Assessment for Orissa State, East Coast of India

Abstract Coastal areas of Orissa State in the northeastern part of the Indian peninsula are potentially vulnerable to accelerated erosion hazard. Along the 480-km coastline, most of the coastal areas, including tourist resorts, hotels, fishing villages, and towns, are already threatened by recurring storm flood events and severe coastal erosion. The coastal habitats, namely the largest rookeries in the world for olive Ridley sea turtles (the extensive sandy beaches of Gahirmatha and Rushikulya), Asias largest brackish water lagoon (the “Chilika”), extensive mangrove cover of Bhitarkanika (the wildlife sanctuary), the estuarine systems, and deltaic plains are no exception. .The present study therefore is an attempt to develop a coastal vulnerability index (CVI) for the maritime state of Orissa using eight relative risk variables. Most of these parameters are dynamic in nature and require a large amount of data from different sources. In some cases, the base data is from remote sensing satellites; for others it is either from long-term in situ measurements or from numerical models. Zones of vulnerability to coastal natural hazards of different magnitude (high, medium, and low) are identified and shown on a map. In earlier studies, tidal range was assumed to include both permanent and episodic inundation hazards. However, the mean of the long-term tidal records tends to dampen the effect of episodic inundation hazards such as tsunamis. For this reason, in the present study, tsunami run-up has been considered as an additional physical process parameter to calculate the CVI. Coastal regional elevation has also been considered as an additional important variable. This is the first such study that has been undertaken for a part of the Indian coastline. The map prepared for the Orissa coast under this study can be used by the state and district administration involved in the disaster mitigation and management plan.

Use of sequential leaching, mineralogy, morphology and multivariate statistical technique for quantifying metal pollution in highly polluted aquatic sediments - a case study: Brahmani and Nandira Rivers, India.

The particle size distribution, geochemical composition and sequential leaching of metals (Fe, Mn, Ni, Cu, Co, Cr, Pb, Zn and Cd) are carried out in core sediments (<88 microm) from the Brahmani and Nandira Rivers, India. To confirm the contamination of downstream sediments by fly ash, mineralogical and morphological characterizations were carried out. High environmental risk of Co, Pb and Ni is due to their higher availability in exchangeable fraction. The metals like Zn, Cu and Mn represent an appreciable portion in the carbonate phase. Metals such as Zn, Pb, Cd, Co and Ni are associated with reducible phase may be due to adsorption. The organic bound Cu, Zn, and Pb seem to be second dominant fraction among non-lithogenous in Nandira sediments. Factor analysis data reveals that textural parameters, Fe-Mn oxy/hydroxides, organic precipitation and coal fly ash disposals, are individually responsible for the enrichment of heavy metals. The relationships among the stations are highlighted by cluster analysis to identify the contamination levels.

Application of factor analysis in geochemical speciation of heavy metals in the sediments of a lake system - Chilika (India): a case study.

Abstract The geochemical association of some trace metals (Fe, Mn, Ni, Cu, Cr, and Pb) were sequentially extracted from bulk sediments of the Chilika lagoon, India. The low elemental concentration, except Pb, in the exchangeable phase suggests poor availability to bottom dwellers. However, slightly higher abundance of Pb in the exchangeable phase at station 4 (9.9%) and station 6 (9.5%) is mainly related with waste from major fishing jetties. The carbonate-bound phase reflects heavy metal distribution of detrital origin along with biological decomposition in the lagoon. A relatively higher percentage of Mn in the reducible phase is attributed to the flocculation of its colloids. The concentrations of Cu, Ni, and Pb show their higher affinity to the organic-bound fraction. The absolute metal concentrations in the residual fraction was Fe > Mn > Ni > Cu > Pb > Cr, which reflects the predominance of physical weathering, a high erosion rate, and a high sedimentation rate in the lagoon. According to Risk Assessment Code, Pb, Cr, and Mn at almost all sites remain in the medium-risk category and can pose some environmental problems, mainly to the benthic community. Multivariate statistics (i.e., factor analysis, FA) was applied to the data set of geochemical fractionation of heavy metals in sediments of a coastal wetland. In this study we present the usefulness of the FA technique for evaluation and interpretation of a large, complex metal fractionation dataset and the apportionment of pollution sources and factors, with a view toward better information on chemical processes occurring in brackish environments. The roles of textural characteristics, organic precipitation, oxy-hydroxide formation and the processes of flocculation and adsorption into fine sediments in different geochemical phases were evaluated. The interpretation of the distribution of metals in different phases related to the relative location of sampling and the environmental characteristics of the fluvial as well as the lagoonal environment.

Distribution of trace metals in surface seawater and zooplankton of the Bay of Bengal, off Rushikulya estuary, East Coast of India

Concentrations of trace metals such as iron (Fe), copper (Cu), zinc (Zn), cobalt (Co), nickel (Ni), manganese (Mn), lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), vanadium (V), and selenium (Se) were determined in seawater and zooplankton from the surface waters off Rushikulya estuary, north-western Bay of Bengal. During the study period, the concentration of trace metals in seawater and zooplankton showed significant spatio-temporal variation. Cu and Co levels in seawater mostly remained non-detectable. Other elements were found at higher concentrations and exhibited marked variations. The rank order distribution of trace metals in terms of their average concentration in seawater was observed as Fe>Ni>Mn>Pb>As>Zn>Cr>V>Se>Cd while in zooplankton it was Fe>Mn>Cd>As>Pb>Ni>Cr>Zn>V>Se. The bioaccumulation factor (BAF) of Fe was highest followed by Zn and the lowest value was observed with Ni. Results of correlation analysis discerned positive affinity and good relationship among the majority of the trace metals, both in seawater and zooplankton suggesting their strong affinity and coexistence.

Environmental dynamics of red Noctiluca scintillans bloom in tropical coastal waters

An intense bloom of red Noctiluca scintillans (NS) occurred off the Rushikulya estuarine region along the east coast of India, an important site for mass nesting events of the vulnerable Olive Ridley sea turtle. At its peak, densities of NS were 3.3×10(5) cells-l(-1), with low relative abundance of other phytoplankton. The peak bloom coincided with high abundance of gelatinous planktivores which may have facilitated bloom development by their grazing on other zooplankton, particularly copepods. Ammonium concentrations increased by approximately 4-fold in the later stages of bloom, coincident with stable NS abundance and chlorophyll concentrations in the nano- and microplankton. This increase likely was attributable to release of intracellular ammonium accumulated through NS grazing. Dissolved oxygen concentrations decreased in sub-surface waters to near hypoxia. Micro-phytoplankton increasingly dominated chlorophyll-a biomass as the bloom declined, with diminishing picoplankton abundance likely the result of high predation by the ciliate Mesodinium rubrum. Together, these data illustrate factors that can disrupt ecosystem balance in this critically important Indian coastal region.

Performance of Semianalytical Algorithm and Associated Inherent Optical Properties in Coastal Waters of North Western Bay of Bengal

The present study was carried out with an aim to assess two semianalytical algorithms, Garver–Siegel–Maritorena (GSM) and Generalized IOP (GIOP) and their association with Inherent Optical Properties (IOP) such as phytoplankton absorption coefficient (aph), detritus absorption (adg) and particulate backscattering (bbp). Ten years of Moderate Imaging Spectroradiometer-Aqua (MODISA) data was processed to retrieve Chlorophyll_a (Chl_a) from GSM and GIOP. Subsequently the Rrs from MODISA was inverted to compute aph, adg and bbp. Both the algorithms showed similar trend at an annual scale. However in magnitude, Chl_a from GSM was three times higher than that from GIOP. Further the Chl_a retrieved from GSM was closer to in situ values. The variability of aph and adg was similar at long-term time scale. The peak observed in variability of aph and adg during pre-monsoon was due to the occurrence of bloom whereas the peak during monsoon was due to nutrient discharge from river. The observed peak in bbp during monsoon can be also attributed to the increasing concentration of total particulate matter from river as well as from bottom re-suspension. The poor association of IOP with Chl_a explains the limited accuracy of satellite retrieved Chl_a from these semianalytical algorithms. Hence it is require generating IOP at the regional scale and tuning the semianalytical model for better accuracy.

An Ephemeral Dinoflagellate Bloom during Summer Season in Nearshore Water of Puri, East Coast of India

The present paper reports on the phenomenon of pinkish-red discoloration of the nearshore water of Puri, Odisha on 12th May 2016. Many local newspapers covered this event, as Puri city is a major tourist and pilgrimage place on the east coast of India. Field observations were carried out in order to provide a scientific basis to the event and to elicit possible causes of this discoloration. Taxonomic analysis of the phytoplankton samples revealed the dominance of red colored dinoflagellate species Gonyaulax polygramma, contributing 90% to total phytoplankton population. The localized concentration of G. polygramma was responsible for the pinkish-red discoloration of nearshore water. The exact factor that lay behind the genesis of this bloom could not be delineated due to the short period of its persistence. But two factors - upwelling and anthropogenic nutrient influx - can be viewed as the main cause for this ephemeral bloom. Non-hypoxic conditions in the coastal water following the ephemeral bloom event indicated no significant risk of ecological deterioration to the ambient medium.

Zooplankton Research in Indian Seas: A Review

To promote long-term studies on the distribution and diversity of marine zooplankton in Indian seas, a comprehensive review has been carried out based on the available literature. Zooplankton studies in Indian waters started in the early 1900s, and a plethora of literature has accumulated dealing with various aspects of zooplankton, especially from the Bay of Bengal, Arabian Sea and their associated estuaries and backwaters. From this review, a comprehensive description is offered on the species composition and distribution of zooplankton in the Indian Seas. Emphasis is given to reflect the existing knowledge on the variations in zooplankton species composition in the Bay of Bengal and Arabian Sea. Copepods emerge as the most dominant component in all of these marine waters, as is the case worldwide. Copepods are more diverse in the Bay of Bengal than in Arabian Sea.

Zooplankton Distribution in Coastal Water off Gopalpur, North-Western Bay of Bengal

An interannual study on zooplankton abundance, biomass, and species composition was carried out during different seasons in two local coastal water types off Gopalpur, north-western Bay of Bengal. Although, Type-1 was observed with higher zooplankton abundance in comparison to Type-2, pattern of variation followed similar seasonal trends in both water types during individual years. Well pronounced seasonality was observed in zooplankton distribution. Zooplankton community was composed of 217 holoplankton and 22 meroplankton. The holoplankton community was predominated by copepod in terms of species diversity and abundance followed by hydrozoa, tintinnida, malacostraca, gastropoda, chaetognatha and chordata. The meroplankton were represented by larval forms viz. bivalve veliger, brachyuran zoea larvae, caridean larvae, copepod nauplii, fish egg and gastropod veliger. Dominance of copepod species viz. Acrocalanus longicornis, Paracalanus aculeatus and Paracalanus parvus were observed frequently in both water types. The species richness was higher in Type-1 in comparison to Type-2 during both the years. Salinity regimes and availability of phytoplankton prey influenced the distribution and species composition of zooplankton assemblage.

Winter thermal inversion and Trichodesmium dominance in north-western Bay of Bengal

Clear thermal inversion was observed with cold surface waters (< 24°C) overlying the warm (> 26°C) subsurface water in the coastal waters of the northwestern Bay of Bengal during winter (January 2015). Simultaneously, preponderance of the cyanobacteria Trichodesmium erythraeum was observed dominating the phytoplankton community with > 90% of total population, reaching maximum density of 9.8 × 105 filaments/L. Further, the Trichodesmium predominance was associated with low water temperature (< 24°C).