A study on the effect of temperature on the anatomy of vegetative reproductive structure and growth rate of halophila ovalis

Previous studies reported that temperature affect growth and anatomy of reproductive structure in seagrasses however, detailed account is lacking hence the present study aimed at revealing the effect of temperature on growth rate and the anatomy of vegetative reproductive structure of Halophila ovalis. Samples were collected from Kunduchi beach during May to October 2011 and grown in the laboratory under variable temperatures of 22-23, 25-26, 27-28, 30-31 and 33-34ºC, established using thermostatic aquarium heaters and water bath for 30 days. During the experiment new and mature leaves were marked, their lengths were measured after two days intervals, at the end of experiment leaf weight, rhizome weight, and rhizome length were also measured. After the experiment growth rate of leaves and rhizome, new leaf production and average rhizome biomass were determined. Fresh sections from the third node of untreated and treated rhizomes were cut, observed under light microscope, photographs were taken and examined for the effect of temperature on cell anatomy. H. ovalis grown at temperature of 33-34ºC survived only for four days, probably due to temperature, suggesting the intolerance of H. ovalis to higher temperature. Growth rate was low at temperatures of (22-23 ºC) and (30-31 ºC), highest growth rate was attained at 25-26ºC suggesting this to be the optimum temperature for growth of this species. The study on the anatomy of vegetative reproductive structure showed that higher temperature causes the cell wall to collapse and disintegration of the septa diminishing growth capacity. Therefore it can be concluded that predicted temperature increase of 2-4.5 ºC as an impact of climate change would translate into changes in seagrasses distribution, abundance and possibly disappearance of higher temperature intolerant species.