Species diversity and distribution of seagrasses from the South Andaman, Andaman and Nicobar Islands, India

Abstract

A survey was conducted with the objective to study seagrass distribution, bed size and shoot density in different substrata of the South Andaman Islands. A total of 231 seagrass sites were observed during the study, in which a total of eight species were found. The South Andaman region exhibited the highest species diversity followed by Havelock, Little Andaman and Neil Islands. Eleven continuous seagrass bed were noted during the study which were confined to three different types of substrata: sand only; sand mixed with coral sand and coral rubble; sand mixed with mud.Thalassia hemprichiiandCymodocea rotundatawere found in dense canopies and covered large areas associated with sand and coral rubble.Halophila beccariishowed moderate abundance in muddy substrata andHalodulespp. grew in fine sand. The highest shoot density was recorded at Haddo, followed by Vijaya Nagar and Chidyatapu, contributed mostly byHalodulespp. In general, seagrass diversity and distribution were mainly influenced by the percentage composition of sand. The authors recommend that the seagrass meadow of Haddo should be considered for conservation priority because of multiple anthropogenic pressures, such as sewage input, dumping of solid wastes on the shoreline and anchoring of boats.

Spatial distribution of Echinolitorina peruviana (Lamarck, 1882) for intertidal rocky shore in Antofagasta (23° S, Chile).

“…The marked differences between sites with different kind of human intervention, in studied sites probably is due to the presence of Pyura praeputialis that is a kind of key species that regulate the species composition in rocky shores in northern Chile (Castilla et al, 2004), in this context, in the present study the human altered sites have not P. praeputialis. Also, the low abundances in sites with marked human intervention agree with results for central Chilean rocky shore (Durán and Castilla, 1989) that is similar to the observations for European rocky shore (Stevčić et al, 2018) and Arabian Sea in India (Pandey et al, 2018;Savurirajan et al, 2018) The results about negative binomial distribution agree with similar observations for inland water benthic invertebrates (Gray, 2005;De Los Ríos Escalante and Mansilla, 2017;Ríos and Arancibia, 2018). Also, in recent studies, it has described the use of negative binomial distribution for intertidal environments, specifically in middle intertidal zone, in rocky shores without seaweeds, similar to sites in the present study (Philippe et al, 2016; Checon et al, ).…”

Null and neutral models for explaining spatial variations in intertidal invertebrate species diversity on rocky shores in Antofagasta town (23°S, Chile)

“…Although in the present study weak differences were obtained of higher species richness and individual abundances in non-altered sites in comparison to altered sites, these results agree with results for central and southern Chilean rocky shores (Moreno et al, 1984;Durán & Castilla, 1989;Velásquez et al, 2016) and Peruvian coast (Tejada-Pérez et al, 2018). These results agree with observations of null models, of the results of null-model co-occurrence of species that revealed many species repeated by sites, and of niche overlapping, which revealed the absence of (Stevčić et al, 2018) and the Arabian Sea in India; both zones have high productivity and high species richness (Pandey et al, 2018;Savurirajan et al, 2018).…”

Population structure of a newly recorded (Halodule uninervis) and native seagrass (Halophila ovalis) species from an intertidal creek ecosystem

“…Similarly, there is a 71% chance of the presence of Cymodocea serrulata along with H. ovalis, but it was not evident in our field survey . Interestingly, this ecological association was also observed in the islands of Lakshadweep (Jagtap, 1998) and ANI Sachithanandam et al, 2014;Savurirajan et al, 2018), which differ in sediment dynamics from the mainland coast of India. This unique association between H. ovalis and H. uninervis sustains on H. ovalis, changing the redox potential of sediments and making them more suitable for colonization of other seagrass species (Kaewsrikhaw et al, 2016).…”

“…The density of H. uninervis at Palk Bay (10,500 shoots/m 2 ) is similar to our results, whereas the density of H. uninervis at ANI (12,325 shoots/m 2 ) is 1.4-fold higher than Haripur creek (Table 3). The higher H. uninervis density in the ANI is results from low turbidity and high light penetration with tropical climatic conditions (Savurirajan et al, 2018). In contrast, the Haripur creek has a seasonal influence of monsoon and associated changes along with algal growth on the leaf surface of H. uninervis.…”