Adhesive strength of epiphytic diatoms on the seaweeds of Kovalam coast, Tamil Nadu

摘要

This is the first floristic inventory of epiphytic diatoms found on the intertidal seaweeds viz. Amphiroa anceps, Caulerpa racemosa, Centroceras clavulatum, Chaetomorpha antennina, Chnoospora minima, Enteromorpha compressa, Hypnea valentiae, Sargassumtenerrimum, Ulva lactuca and Valonia utricularis occurring in the Kovalam marine environment of Kanniyakumari District. The epiphytic diatom species were separated by the five step separating treatments of shaking and rubbing. On the basis of the separation order, epiphytic diatoms were grouped into five categories. First group (Separation-A) had diatoms with least adhesive strength. Second group (Separation-B) had large and active motile species. The third group (Separation-C) consisted of the speciesattached firmly to the substrate. Fourth group of diatoms showed largest adhesive strength (Separation-D) and the final group diatoms (Separation-E) were obtained by the process of rubbing the seaweeds in methanol with hand. During the study period, some tycoplanktonic and planktonic diatoms were also commonly observed on the seaweeds. Separation variations of epiphytic diatom population density percentage varied between the different seaweed species. Maximum percentage of epiphytic diatom population density was recorded in V. utricularis^ 6.73%) and the minimum was recorded in A. anceps(2.21 %). The community structure of epiphytic diatoms varied between separations and seaweeds. The total population densities of each epiphytic diatom on various seaweeds were 63 to 3939 Cells g"'. The dominant diatom species viz. Achnanthes coarctata, Cyclotella litoralis, Synedra tabulata, Nitzschia grossestriata, Thallassiothrix longissima, Licmophora abbreviata, Navicula contenta, Fragilaria brevistriatula, Thallassiothrix frauenfeldii and Thallassiothrix frauenfeldii and the subdominant species viz. Cyclotella litoralis, Bacillaria paradoxa, Surirella robusta, Nitzschia longissima, Climacosphenia moniligera, Synedra tabulata, Bacillaria paradoxa, Triceratium reticulatum and Cyclotella litoralismre recorded in the seaweed species A. anceps, C. racemosa, C. clavulatum, C. antennina, C. minima, E. compressa, H. valentiae, S. tenerrimum, U. lactucaand V. utricularis.