Integrating Indian remote sensing multi-spectral satellite and field data to estimate seagrass cover change in the Andaman and Nicobar Islands, India     

Nobi Elavumkudi Paulose  Elangovan Dilipan  Thirunavukarassu Thangaradjou 《Ocean Science Journal》2013,48(2):173-181

Environmental resource managers and policy makers require a reliable tool to quickly assess the spatial extent of any natural resources, including seagrasses, in order to develop management plans. Even small natural or anthropogenic disturbances can cause severe changes in the distributional pattern of seagrass meadows. Satellite imageries provide a suitable means to detect and assess such changes in space and time in remote and inaccessible areas. Present study aims to understand the distribution pattern of seagrasses after the Indian Ocean Tsunami in 2004 with the help of Indian Remote Sensing satellite data and in situ ground surveys with hand held GPS. As no geospatial data bases were available for the pre-tsunami period, the changes in seagrass cover were compared with the ground estimates available in the literature and also using pre-tsunami satellite data sets. The study found severe loss of seagrasses in the northern Andaman particularly in the Interview and North reef islands and in the Nicobar group of islands including Great Nicobar and Trinket islands. The investigation revealed the presence of 2,943.38 ha of seagrass covering the entire Andaman and Nicobar islands, and that 1,619.41 ha of seagrasses had been denuded during this period. The earthquake and subsequent tsunami in 2004 was the major reason for the loss of seagrasses in these islands. The seagrass spatial map generated in the present study can be used for the development of conservation and management plans and also to restore the denuded seagrasses of this region.  相似文献   

Inter-annual and seasonal variations in hydrological parameters and its implications on chlorophyll a distribution along the southwest coast of Bay of Bengal     

Shanthi R.  Poornima D.  Raja K.  Sarangi R. K.  Saravanakumar A.  Thangaradjou T. 《海洋学报(英文版)》2015,34(6):94-100

Seasonal and inter-annual variability of hydrological parameters and its impact on chlorophyll distribution was studied from January 2009 to December 2011 at four coastal stations along the southwest Bay of Bengal. Statistical analysis(principal component analysis(PCA), two-way analysis of variance(ANOVA) and correlation analysis)showed the significant impact of hydrological parameters on chlorophyll distribution in the study area. The ranges of different parameters recorded were 23.8–33.8°C(SST), 4.00–36.00(salinity), 7.0–9.2(p H), 4.41–8.32 mg/L(dissolved oxygen), 0.04–2.45 μmol/L(nitrite), 0.33–16.10 μmol/L(nitrate), 0.02–2.51 μmol/L(ammonia),0.04–3.32 μmol/L(inorganic phosphate), 10.09–85.28 μmol/L(reactive silicate) and 0.04–13.8 μg/L(chlorophyll).PCA analysis carried out for different seasons found variations in the relationship between physico-chemical parameters and chlorophyll in which nitrate and chlorophyll were positively loaded at PC1(principal component1) during spring inter-monsoon and at PC2(principal component 2) during other seasons. Likewise correlation analysis also showed significant positive relationship between chlorophyll and nutrients especially with nitrate(r=0.734). Distribution of hydrobiological parameters between stations and distances was significantly varying as evidenced from the ANOVA results. The study found that the spatial and temporal distribution of chlorophyll was highly dependent on the availability of nutrients especially, nitrate in the southwest Bay of Bengal coastal waters.  相似文献   

Trend in coral-algal phase shift in the Mandapam group of islands,Gulf of Mannar Marine Biosphere Reserve,India     

M. Machendiranathan  L. Senthilnathan  R. Ranith  A. Saravanakumar  T. Thangaradjou  S. B. Choudhry  S. K. Sasamal 《中国海洋大学学报(英文版)》2016,15(6):1080-1086

The present study revealed proliferation of macro-algae modifying coral reef ecosystems in a different manner due to diseases and sedimentations in the Mandapam group of islands in the Gulf of Mannar. Benthic surveys were conducted with major attack of seven coral reefs diseases with high sedimentation rate, nine species of fleshy macro-algae(Turbinaria ornata, Turbinaria conaides, Caulerpa scalpelliformis, Caulerpa racemosa, Kappaphycus alvarezii, Padina gymnosphora, Sargassum wightii, Ulva reticulata and Calurpa lentillifera) proliferation against major corals life forms(Acropora branching, Acropora digitate, Acropora tabulate, coral massive, coral submassive, coral foliose and coral encrusting). The results confirm that diseased corals most favor to macro-algae growth(15.27%) rather than the sedimentation covered corals(8.24 %). In the degradation of coral life forms, massive corals were more highly damaged(7.05%) than any other forms. Within a short period of time(May to September), coral coverage shrank to 17.4% from 21.9%, macro-algae increased 23.51% and the average sedimentation rate attained 77.52 mg cm~(-2) d~(-1) with persisting coral reef diseases of 17.59%. The Pearson correlation showed that the coral cover decreased with increasing macro-algae growth, which was statistically significant(r =-0.774, n = 100, P 0.0005). The proliferation of the various macro-algae C. scalpellifrmis, T. ornata, C. racemosa, T. conaides, U. reticulata, S. wightii, K. alvarezii, P. gymnosphora and C. lentillifera increased with percentages of 6.0, 5.8, 5.7, 4.9, 4.2, 3.7, 2.7 and 1.9, respectively. If this trend continues, the next generation of new recruit corals will undoubtedly lead to a phase shift in Gulf of Mannar corals.  相似文献   

Geochemical and geo-statistical assessment of heavy metal concentration in the sediments of different coastal ecosystems of Andaman Islands,India   总被引：1，自引：0，他引：1  

E.P. Nobi  E. DilipanT. Thangaradjou  K. SivakumarL. Kannan 《Estuarine, Coastal and Shelf Science》2010

Spatial distribution of metal concentrations in the surface sediment samples collected from 16 marine locations covering different coastal ecosystems such as mangroves, seagrasses, dead coral and sandy beaches of the Andaman islands, India was studied. pH, EC, sediment grain size and heavy metal (Al, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) concentrations were determined and contamination factor (CF) and geo-accumulation index (I_geo) were calculated to understand the pollution status of the study area based on the background values. CF of different heavy metals has revealed that different metals have different levels of accumulation viz. Al: 0.01–0.22, Mg: 0.38–1.85, Fe: 0.06–0.74, Mn: 0.04–1.18, Cu: 0.18–2.93, Cr: 0.52–12.6, Zn: 0.3–1.39, Ni: 0.06–0.89, Pb: BDL–0.74, Co: 0.1–0.35 and Cd: 2.3–12.9. In general the metal concentration was less in these ecosystems when compared to similar ecosystems of mainland of India. Concentration of some metals like Cr and Cd was comparatively higher than the background values which is an important issue of concern to the coastal managers of the region. Spatial data on heavy metals, collected now, would help the coastal zone managers to identify the vulnerable sites and take remedial actions.  相似文献   

Sources and threats of chronic tissue loss on coral reefs in the Lakshadweep Islands,Indian Ocean          下载免费PDF全文

Rajamohanan Pillai Ranith  Lakshmanan Senthilnathan  Mayakrishnan Machendiranathan  Thirunavukarasu Thangaradjou  Sasanka Sasamal  Saroj B. Choudhury 《Marine Ecology》2017,38(3)

Tissue degradation and resulting mortality are major threats to coral reefs around the world. Information on interactions of the major environmental factors that mediate tissue loss and mortality in coral reefs is of great importance. It is essential to understand the prevailing reef health conditions and to develop appropriate management actions. In the present study, a series of benthic surveys conducted in the Lakshadweep Islands revealed the interaction of major biological factors in causing tissue loss and mortality. Hierarchical regression analysis revealed interactions of various environmental scenarios. Tissue loss was prevalent in islands with high cover of massive corals (m = 20.91) and low in islands dominated by branching corals (m = 0.61). Hierarchical regression analysis revealed black band disease (β = .59; p < .001) and algal interactions (β = .48; p < .001) to be major factors responsible for coral mortality caused by tissue loss in the region.  相似文献