South Andaman Island Research Articles

Spatial distribution of Aedes aegypti and Aedes albopictus in relation to geo-ecological features in South Andaman, Andaman and Nicobar Islands, India.

The study was undertaken in South Andaman district, comprising three tehsils, viz. Port Blair, Ferrargunj and Little Andaman Tehsils, respectively. Intensive pupal infestation surveys were carried out along the National Highway (NH 223), the main passenger and trade route, referred to as Great Andaman Trunk Road. Sampling locations at every 3 km were geo-referenced with global positioning system unit. A total of 17314 water collections were examined from 29 locations across the South Andaman district, among which 1021 (5.9%) were colonized by immature stages of Aedes albopictus, Aedes aegypti and other mosquito species. Ae. aegypti were found in 12 locations, showing higher infestation in the densely built Aberdeen Bazaar. Breeding populations of Ae. albopictus were observed in 27 sampling locations. Both the species were not recorded in two Northern localities. In the areas where both the species are present, they were often found in the same developmental sites, suggesting convergent habitat selection. The most frequently encountered man-made, artificial and natural developmental sites were fixed cement tanks, plastic drums, plastic cans, metal drums, metal pots, discarded tires, coconut shells, leaf axils and tree holes. Ae. aegypti and Ae. albopictus were observed in varying proportions in Port Blair and Ferrargunj Tehsils, while the former species appeared to be absent in Little Andaman. This study elucidates the spatial distribution of Ae. aegypti and Ae. albopictus with preponderance of the latter species, pointing towards arboviral transmission and assumes public health importance in South Andaman district, endemic for dengue.

DIVERSITY AND DISTRIBUTION OF LIVING LARGER BENTHIC FORAMINIFERA FROM CORAL REEF ENVIRONMENTS, SOUTH ANDAMAN ISLAND, INDIA

The waters around the Andaman and Nicobar Islands (ANI) sustain a rich fauna, including larger benthic foraminifera (LBF), which are presently not well-studied. We documented the diversity and distribution of LBF at six reef sites (4–30 m) in South Andaman. We recorded a total of 16 LBF species belonging to 12 genera and 7 families. Amphistegina lessonii, A. radiata, and Calcarina spengleri were found at five of the sites surveyed. The density of living larger benthic foraminifera was 5–17 specimens per cm 2 . The Shannon-Wiener Diversity Index (H) ranged from 0.90–2.06, the Margalef Species Richness Index (D) from 0.39–1.62 and Pielou’s Equitability Index (J) from 0.77–1.12. These relatively high index values reflect the carbonate environment, characterized by a diverse and relatively even distribution of larger benthic foraminiferal assemblages in the South Andaman Islands.

Notes on Scarcely Collected Indian Liverworts III. Plagiochila kurzii (Plagiochilaceae, Marchantiophyta)

Plagiochila kurzii Steph. is known in Indian bryoflora from South Andaman and Katchall Islands in Andaman & Nicobar. The species, last collected from Indian territory towards the close of nineteenth century, is recently rediscovered in the country from South Andaman Island after a gap of over eleven decades.

The non-arboreal diversity of the Andaman Islands, India, based on pollen analysis

ABSTRACTThis paper deals with the pollen morphology of 118 non-arboreal taxa (80 herbs and 38 shrubs) of the South Andaman Islands, India. Pollen morphology was investigated through an acetolysis method and using a trinocular light microscope. Size, shape, symmetry, polarity, apertural pattern and ornamentation are described for every species. Among 118 taxa, only three have heteropolar pollen grains. Prolate shape is dominant and found in 17 taxa while oblate shape is found only in Macrosolen cochinchinensis. Among the 12 apertural patterns, tricolporate is dominant and found in 48 taxa, whereas hexacolpate pollen is present in Ocimum tenuiflorum. Of the nine ornamentation types recorded, psilate and reticulate types are common; Barleria prionitis and Datura metel are distinct with scabrate and striate ornamentation. These observations are of immense value in taxonomical, melissopalynological, aeropalynological and palaeopalynological studies.

Significance of Ophiolite Emplacement in the Development of Ninetyeast Ridge, South Andaman Island, Indian Ocean

Significance of Ophiolite Emplacement in the Development of Ninetyeast Ridge, South Andaman Island, Indian Ocean

Comparison between microzooplankton population in polluted and moderately polluted coastal waters of Port Blair, South Andaman.

We report on the seasonal and spatial variations of microzooplankton between polluted and moderately polluted coastal waters of South Andaman Island, in relation to certain physicochemical and biological parameters. Microzooplankton communities were studied and recorded for 1year (September 2011 to August 2012) during the northeast monsoon, the intermonsoon, and the southwest monsoon periods. We recorded a total of 75 species belonging to 29 genera, of which polluted waters encompassed 71 species (28 genera). In contrast, only 59 species (22 genera) were recorded in the moderately polluted waters. We discovered that taxonomic composition, biomass, and abundance of microzooplankton not only varied spatially but also altered seasonally. It is noteworthy to state that the northeast monsoon played a significant role in controlling the abundance of microzooplankton in South Andaman coastal waters.

Reappearance of the rare Shingle Urchin Colobocentrotus (Podophora) atratus (Camarodonta: Echinometridae) after eight decades from the rocky shore of Kodiyaghat (Port Blair), South Andaman Islands, India

The present work is aimed at facilitating conservation efforts of a rare species of sea urchin (Colobocentrotus atratus) reported nearly eight decades after its initial description by Bell (1887) and later by Clarke (1925) from the coastal waters of south Andaman Islands. Recently, during a three years study (2011-14) on the macrobenthic epifauna along the south Andaman coast, five live specimens of C. atratus were recorded from Kodiyaghat (11031'532''N; 092043'457'' E), south Andaman Islands. Available information shows that this species has reappeared in the south Andaman Islands seventy nine years after the citation by Sastry (1994) collected in the year 1935. The disappearance of this species from the literature in the intermittent years and a sparse population in coastal reaches of south Andaman Islands at present suggest that this species makes a candidate taxa for inclusion in the list of ‘endangered’ or ‘vulnerable’ Indian marine species following IUCN Red List criteria to Wild species.

A New Species and a New Record ofCololejeunea(Lejeuneaceae, Marchantiophyta) from Andaman & Nicobar Islands, India

A new species of Cololejeunea (Spruce) Schiffn., C. andamanensis sp. nov. is described from South Andaman Island. Cololejeunea pseudoschmidtii Tixier, previously known only from China, Malaysia, Philippines and Vietnam, is reported from South Andaman Island and the Great Nicobar Biosphere Reserve in the Nicobar group of the Islands of India.

Magnetic anomalies over the Andaman Islands and their geological significance

The Andaman Islands form part of the outer-arc accretionary sedimentary complex belonging to the Andaman–Sumatra active subduction zone. The islands are characterized by thick cover of Neogene sediments along with exposed ophiolite rocks at few places. A regional magnetic survey was carried out for the first time over the Andaman Islands with a view to understand the correlation of anomaly signatures with surface geology of the islands. The residual total field magnetic anomaly maps have revealed distinct magnetic anomalies having intermediate to high amplitude magnetic signatures and correlate with the areas over/close to the exposed ophiolite rocks along the east coast of north, middle and the south Andaman Islands. The 2D modelling of magnetic anomalies along selected E–W profiles across the islands indicate that the ophiolite bodies extend to a depth of about 5–8 km and spatially correlate with the mapped fault/thrust zones.

Antimicrobial Activity and Phylogenetic Analysis of Streptomyces Parvulus Dosmb-D105 Isolated from the Mangrove Sediments of Andaman Islands.

Actinomycetes, especially species of Streptomyces are prolific producers of pharmacologically significant compounds accounting for about 70% of the naturally derived antibiotics that are presently in clinical use. In this study, we used five solvents to extract the secondary metabolites from marine Streptomyces parvulus DOSMB-D105, which was isolated from the mangrove sediments of the South Andaman Islands. Among them, ethyl acetate crude extract showed maximum activity against 11 pathogenic bacteria and six fungi. Presence of bioactive compounds in the ethyl acetate extract was determined using GC-MS and the compounds detected in the ethyl acetate extract were matched with the National Institute of Standards and Technology (NIST) library. Totally eight compounds were identified and the prevalent compounds were 2 steroids, 2 alkaloids, 2 plasticizers, 1 phenolic and 1 alkane. Present study revealed that S. parvulus DOSMB-D105 is a promising species for the isolation of valuable bioactive compounds to combat pathogenic microbes.

Joint application of satellite remote sensing, ground penetrating radar (GPR) and resistivity techniques for targeting ground water in fractured Ophiolites of South Andaman Island, India

The Ophiolitic complex of the study area oriented in N–S direction, having moderate to steep slopes of the topography and characterized by strong heterogeneity, repetitive deformations and multiple intrusions. Ophiolites of the study area encompass the major groundwater-bearing zones. Generally, these formations have shallower fractured aquifers of a thickness 30–45 m and sometimes due to deep tensile fractures the thickness of aquifer exceeds more than 60 m with a considerable groundwater yield. A joint venture of satellite remote sensing, geoelectrical resistivity and ground penetrating radar (GPR) techniques has been used to assess the groundwater potential of the fractured Ophiolites. The interpreted resistivity inversion model and GPR results were incorporated with borehole lithologs for their subsurface properties and structural variations. The integration of using multiple techniques has increased the accuracy of interpretation, and thus conflated results significantly rendered the existence of weathered and fractured zone having hydrogeological importance. Based on the parameters, viz., geoelectrical properties of layers, reflection configuration, thickness of weathered and fractured aquifer zone, a typical aquifer model for the study area that contains various layers and subtle structural variation has been developed. Further, the derived integrated geophysical data also detail on various lithological characteristics and advances the understanding about aquifer systems of fractured Ophiolites and the distribution of groundwater in fractures.

Habitat Ecology and Ichthyofaunal Diversity of Two Creeks and Their Associated Streams from Port Blair, South Andaman Islands

Habitat ecology and ichthyofaunal diversity were analyzed from two creeks and their associated streams in Port Blair: one was perennial and the other one was seasonal. Various habitat types like riffles, pools, and major and minor bends in both streams were studied. The perennial stream has 12 riffles and 14 pools from head point to the entering point of the creek. The seasonal stream has 15 riffles and 13 pools from the starting point to the sink. The perennial stream was found to have higher ichthyofaunal diversity than the seasonal stream: 1701 individuals constituting 8 orders, 30 families, 42 genera, and 54 species were recorded. Among these, 395 specimens represented by 21 species were found in perennial stream, 291 specimens with 11 species were found in seasonal stream, 863 specimens by 48 species were noted in creek, and 152 specimens constituting 14 species in sink were recorded. The physicochemical parameters of the habitats showed more or less a similar trend. The average dissolved oxygen value of the perennial stream was higher than that of the seasonal stream. Higher temperature values were noted during the postmonsoon season. This study has indicated a wide lacuna in the knowledge of the fresh water habitats and their inhabitants on these islands.

Prevalence and Diversity of Leptospires in Different Ecological Niches of Urban and Rural Areas of South Andaman Island.

Leptospirosis is an emerging disease around the globe. South Andaman Island is an endemic region for leptospirosis. We herein compared the prevalence of leptospires in urban and rural areas of South Andaman Island. The PCR detection and isolation of Leptospira revealed that pathogenic leptospires were prevalent in sewage water and household drainage water in urban areas and in paddy fields, vegetable field water, and stream water in rural areas. These results demonstrate that intermediates are ubiquitously present in the environment and may be responsible for asymptomatic infections, and also provide an insight into disease ecology.

Application of resistivity and GPR techniques for the characterization of the coastal litho-stratigraphy and aquifer vulnerability due to seawater intrusion

The objective of this study is to identify geological properties and structural settings, allowing salt-water intrusion to the aquifers in oceanic originated rock formations of the South Andaman Island. To evaluate the impact of seawater in groundwater aquifer, several geophysical surveys using ground penetrating radar (GPR) and resistivity sounding were performed through the most significant sites, located near coastal areas, tidal channels and agriculture land. High-resolution GPR images were obtained and combined with resistivity sounding, which allows to identify the mixing/transition zone of fresh and saline groundwater and also successfully delineated the structural geometry and litho-stratigraphic details of aquifers. We show that the sedimentary formations are highly susceptible to seawater intrusion than the mantle originated ophiolites. Further, potential impacts from seawater intrusion are higher along the west coast than the east coast because of macro-pore tendency of soils allows seawater filtration.

Stratigraphic evidence for earthquakes and tsunamis on the west coast of South Andaman Island, India during the past 1000 years

Stratigraphic records from west coast of South Andaman Island revealed evidence of three historical earthquakes and associated transoceanic tsunamis during past 1000yrs, in addition to the Mw 9.3 tsunamigenic earthquake of 26 December, 2004. Our finding suggests that along with Sumatran arc segment the Andaman–Arakan segment is also capable of generating mega-subduction zone earthquakes and transoceanic tsunamis. To study the near sub-surface stratigraphic succession we excavated shallow trenches and obtained geoslices from two sites around Collinpur (sites 1 and 2). The exposed succession comprised 11 lithounits (Unit a — youngest and k — oldest) of alternating sequence of coarser units overlain by peaty soils and some of these are indicative of deposition during paleo-tsunami events.Event I that predated AD 800, and is marked by a 35–40cm thick deposit of fine gravel to coarse sands along with broken shell fragments (Unit k). Event II dated around AD 660–800, is represented by 20–25cm thick coarse sand and broken shell fragments (Unit i). Based on stratigraphic evidences of land-level changes, this event is attributed to a near source rupture along Andaman–Arakan segment, accompanied by a transoceanic tsunami. Event III, occurred around AD 1120–1300, is marked by a 50cm thick sand deposit (Unit g). The 2004 tsunami resulted in deposition of 15cm thick medium to coarse sand at the same location. We infer that the 2004 tsunami and Event III resulted in different styles of sedimentation at the same site.Four events at Collinpur along with the record of a subsidence event of AD 1679 from the east coast of Andaman, close-to, Port Blair (Malik et al., 2011), suggest that mega-subduction zone earthquakes and associated tsunamis recur at an interval of 300–500 years at variable locations along the Sumatra–Andaman subduction zone.

Host-feeding pattern of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) in heterogeneous landscapes of South Andaman, Andaman and Nicobar Islands, India.

Mosquito foraging behavior is a determinant of host-vector contact and has an impact on the risk of arboviral epidemics. Therefore, blood-feeding patterns is a useful tool for assessing the role in pathogen transmission by vector mosquitoes. Competent vectors of dengue and chikungunya viz. Aedes aegypti and Aedes albopictus are widely prevalent in the Andaman and Nicobar archipelago. Considering the vector potential, medical importance of both these mosquito species and lack of information on host-feeding patterns, blood meal analysis of both these vector mosquitoes was undertaken. Biogents Sentinel traps were used for sampling blooded mosquitoes, for identifying the source of blood meal by agar gel-precipitin test. We identified vertebrate source of 147 and 104 blood meals in Ae. aegypti and Ae. albopictus from heterogeneous landscapes in South Andaman district. Results revealed that Ae. aegypti (88 %) and Ae. albopictus (49 %) fed on human and a small proportion on mammals and fowls, indicative of predominance of anthropophilism. Ae. aegypti predominantly fed on human blood (94.2 %-densely built urban, 89.8 %-low vegetation coverage, and 78.3 %-medium vegetation coverage). Anthropophilism in Ae. albopictus was maximal in densely built urban (90.5 %) and progressively decreased from low vegetation-vegetation/forested continuum (66.7, 36.4, and 8.7 %), indicating plasticity in feeding across these landscapes. Epidemiological significance of the findings is discussed.

Provenance analysis of the Oligocene turbidites (Andaman Flysch), South Andaman Island: A geochemical approach

The Oligocene-aged sandstone-shale turbidites of the Andaman Flysch are best exposed along the east coast of the South Andaman Island. Previously undocumented sandstone-shale geochemistry, investigated here, provides important geochemical constraints on turbidite provenance. The average 70.75 wt% SiO2, 14.52 wt% Al2O3, 8.2 wt% Fe\(_{2}\textit {O}_{3}^{\mathrm {t}}+\)MgO and average 0.20 Al2O3/SiO2 and 1.08 K2O/Na2O ratios in sandstones, compare with quartzwackes. The shale samples have average 59.63 wt% SiO2, 20.29 wt% Al2O3, 12.63 wt% Fe\(_{2}\textit {O}_{3}^{\mathrm {t}}+\)MgO and average 2.42 K2O/Na2O and 0.34 Al2O3/SiO2 ratios. Geochemical data on CaO–Na2O–K2O diagram fall close to a granite field and on K2O/Na2O–SiO2 diagram within an active continental margin tectonic setting. The range and average values of Rb and Rb/Sr ratios are consistent with acid-intermediate igneous source rocks, while the values and ratios for Cr and Ni are with mafic rocks. Combined geochemical, petrographic and palaeocurrent data indicate a dominantly plutonic-metamorphic provenance with a lesser contribution from sedimentary and volcanic source, which is possibly the Shan–Thai continental block and volcanic arc of the north-eastern and eastern Myanmar. Chemical index of alteration (CIA) values suggests a moderate range of weathering of a moderate relief terrane under warm and humid climate.

Multivariate and geo-spatial approach for seawater quality of Chidiyatappu Bay, south Andaman Islands, India

Chidiyatappu Bay is one of the least disturbed marine environments of Andaman & Nicobar Islands, the union territory of India. Oceanic flushing from southeast and northwest direction is prevalent in this bay. Further, anthropogenic activity is minimal in the adjoining environment. Considering the pristine nature of this bay, seawater samples collected from 12 sampling stations covering three seasons were analyzed. Principal Component Analysis (PCA) revealed 69.9% of total variance and exhibited strong factor loading for nitrite, chlorophyll a and phaeophytin. In addition, analysis of variance (ANOVA-one way), regression analysis, box-whisker plots and Geographical Information System based hot spot analysis further simplified and supported multivariate results. The results obtained are important to establish reference conditions for comparative study with other similar ecosystems in the region.

Seven Angiosperm Species, New Records for Andaman and Nicobar Islands, India

Seven angiosperm species collected from Middle and South Andaman Islands are being reported as additions to the flora of Andaman and Nicobar Islands after Pandey and Diwakar (2008). Brief description, phenology, and distribution pattern are presented along with photographs for the species.

Studies on the Mangrove Macro Faunal Diversity and Assessment among Different Sites in Port Blair Bay, South Andaman Islands

The mangrove intertidal zone is characterised by plenty floral and faunal diversity. The mangroves provide important habitat for a wide range of species like diverse communities of benthic organisms and function as nursery habitats for different types of crab, prawn and fish species and support offshore fish populations and fisheries. To assess the occurrence, spatial distribution and species composition of macro fauna in a mangrove area, core samples were taken along with transect in Portblair bay, South Andaman Islands. Three sites were taken; each study area was divided into three zones viz. Proximal, middle and distal zones, which were analyzed according to the floral composition. The highest value was observed at Barmanallah (2061 no.m-2), followed by Carbyn’s Cove (1710 no.m-2) and the lowest value was noticed at Manjery (882 no.m-2). Terebralia palustris, Cerithidea sp., Periopthalmus sp., Uca sp., Balanus sp. and Polychaetes were dominated in order. Some locations were found to support a high diversity of organisms across habitats, while other locations had high densities of a few species only.