Howayda etal., (2007) reported that the ethanolic extract of R.
cirrhosa whichinhibited all of the tested bacterial isolates except E.coli. Kolanjinathan and Stella (2009) indicatedthat acetone was the best solution for extracting effective antimicrobialmaterials from Sargassum myricystum, Hypnea musiformis, Turbinariaconoides, Halimedia gracilis and Gracilaria edulis whereas,Karthikaidevi et al., (2009) used seven different solvents such as ethylacetate and methanol for extraction of antibacterial substances from Ulvareticulate, Codium adherens and Halimeda tuna. Earlier reportsshowed that marine plants showed antimicrobial activity against fish pathogens(Dhayanithi et al., 2010; Anitha, 2006).
The MIC of Zostera marina extractswere ranged from 161mg to 8 mg/ml was active against all three human skinpathogens Han Gil et al., (2009). They also reported the MIC of then-butanol and ethyl acetate fractions were the same with 1 mg/ml against C.albicans and S. aureus. Umamaheshwariet al., (2009) and Ragupathi et al., (2010b) reported theseagrass Halodule pinifolia showed stong antibacterial activity againstpathogens.
Sundaram et al., (2011a) demonstrated that antibacterialactivity of seagrass S. isoetifolium root extracts against fishpathogens.
The broad spectrum of six fractions from acetone extract and onefraction from hexane root extracts ofC. serrulata exhibitedantibacterial activity (Sundaram et al., 2011b).
The methanol extract ofH. ovalis collected from the Chunnambar estuary in Pondicherry exhibitedstong antibacterial activity of 17nm against B. cereus followed by 14nmagainst A.
baumannii Yuvaraj et al., (2011).The crudeethyl acetate extract of E. acorodies collected from the seagrass bed inMerambung Island inhibited the growth of all test bacteria with the largestzone of inhibition displayed by P. aeruginosa which was followed byMSSA, MRSA and S. epidermidis(Mohd et al., 2012).
Aswathi etal., (2012b) reported that the ethanol extraction of the sea grasses C.rotundata showed better zone of inhibition than other tested extractsagainst bacterial pathogens. Seagrass are marine plants found nearshore waters.
They are one of the most highly productive tropical ecosystemsand act as shelter and food for near shore fisheries, marine reptiles and manmals.They have a widespread distribution that encompasses every continent, exceptAntarctica but the highest diversity of seagrass species is centred in thetropical Indo-Pacific (Waycott et al., 2004). Seagrass habitatsare an important component of the marine environment, providing vital servicessuch as nutrient cycling, food provision, and climate change mitigation (Orth etal., 2006; Waycott et al., 2009).Similar to other marine ecosystems, seagrass habitats are under threat fromhuman activities, such as coastal development and increased nutrient input.
These impacts have brought about accelerated decline in seagrass habitatsglobally (Waycott et al., 2009).Seagrasses are marine flowering plants thathave the ability to complete their life cycle while fully submerged in marineenvironment constraints. Short et al.
, (2001) reported thatthese marine plants cover large geographic area worldwide. Seagrasses provideservices and goods for their ecological conmunity, for example, waveprotection, reduced water flow, fishing ground, and oxygen production (Bail, 2005) and (Aziz et al., 2006).Ahmad-Kamil etal.
(2013) studied and reported that seagrasspercentage increased during the El-Nino period, due to some naturaldisturbances. Evolution of land usage and measurements of other waterphysicochemical parameters (such as heavy metal, pesticides and nutrients)should be considered, to assess the health of seagrass ecosystem at the studyarea. The ethnotaxa ‘Saethu pasi’ (H. ovalis) is found in dark water zonesthat have a muddy substratum. Fishermen find these muddy or ‘saethu’ zones veryinteresting because they provide habitat for numerous crabs, shrimps and fish.Although it is difficult for a trained taxonomist to distinguish H.
ovata (‘Pottal pasi’) from H. ovalis (‘Saethu pasi’) without usingmacroscopic characters (e.g., seed number and cross venation pattern), localpeople can easily distinguish the two species based on the different habitatsthey grow in predominant species are Cymodocearotundata, Cymodocea serrulata, Halodule pinifolia, Halophila ovalis, Syringodium isoetifolium and Thalassia hemprichii. These seagrasses provide critical habitat fordiverse marine fauna such as cuttlefish, dugongs, sea horses, eels, rays andscorpion fish, sea cucumbers and sea snakes, among others.
He alsoreported theimportance of seagrasses to local coastal economies in the state of Tamil Naduis apparent by the engagement of the conmunity in collecting and sortingseagrasses. In fact, trading depots are established along the coast wherepeople trade or buy local produce including seagrasses (Newmaster et al., 2011).