Assessment of Ecological Health of Sunnambar and Ariankuppam Estuaries(Southeast Coast of India)

Man has a long history of exploiting the costal and estuarine areas which have very highecological values for food, transport, commerce and for settlement. Nevertheless, suchecosystems are subjected to a wide range of anthropogenic pressures which are responsiblefor considerable environmental impairment. Over the past decades water quality has beendefined primarily in chemical terms. Recently, agencies managing water quality have beenincreasingly emphasising the use of biological parameters as monitoring tools for betterassessment of the effects of environmental stressors on biological systems. In keeping withthis emerging trend, the ecological health of two estuaries namely Sunnambar andAriankuppam situated in the Union Territory of Puducherry on the southeast coast of Indiawas assessed using benthic organisms. Samples were collected for a period of one year.Every month sediment samples were collected using Petersen grab. Five stations were fixedup along the course of the estuaries and each time samples were collected in duplicate.Information on physico-chemical parameter such as temperature, salinity, pH and organicmatter was also collected. The levels of all the heavy metals analysed (Co, Cu, Ni, Pb, Fe, Zn,Mn and Hg) were higher in Ariankuppam estuary than in Sunnambar estuary. The number ofspecies of polychaetes identified from Sunnambar and Ariankuppam estuaries was 45 and 11respectively. The diversity indices were very low in the Ariankuppam estuary(H‟log20.8741±0.24, d-1.07±0.45, J-0.528±0.03, Lambda'-0.78±0.06 and sPhi+347±77.74)and high in Sunnambar estuary (H‟log2-4.1253±0.12, d-4.982±0.57, J-0.874±0.01, Lambda'-0.03±0.004 and sPhi+-1704±273.34). The assignment of the polychaete species identifiedinto one of the five ecological groups (EGI: species sensitive to disturbance; EGII: speciesindifferent to disturbance; EGIII: species tolerant to disturbance; EGIV: second orderopportunistic species; EGV: first order opportunistic species) as proposed by the marinebiotic index AMBI was done based upon the list available in the AMBI program(http://www.azti.es). The M-AMBI was calculated by factor analysis (FA) of AMBI, speciesrichness (as number of taxa) and Shannon‟s diversity index values, using AMBI software(http://ambi.azti.es). This method compares monitoring results with reference conditions bysalinity stretch, in order to derive an M-AMBI value, which expresses the relationshipbetween observed values and reference condition values. At „high‟ status the referencecondition may be regarded as an optimum where the M-AMBI approaches 1. At „bad‟ status,the M-AMBI approaches 0. High BI in Ariankuppam estuary and high M-AMBI value inSunnambar estuary clearly revealed the disturbed condition of Ariankuppam estuary andhealthy nature of Sunnambar estuary. These values (BI and M-AMBI) should becontinuously monitored as there is rapid industrialisation and urbanisation around Puducherrytown.Keywords: Estuarine health, Suunambar, Ariankuppam, Macrobenthos, Diversit