Epiphytism differences in Gelidiella acerosa cultivated with floating rafts and concrete blocks

Seasonal variations in epiphytic assemblages on Gelidiella acerosa cultivated in 2different methods (Floating raft and Bottom concrete block) were studied for 13 months from November 2009 to November 2010 covering all 4 seasons (northeast monsoon, southwest monsoon, autumn and summer). Twenty-five macro algal species were found in raft culture. Chaetomorpha linum Jania adhaerens, Hypnea valentiae, and Lyngbya majuscula were the dominant epiphytes. Twenty-four epiphytic algae were recorded in bottom concrete block culture. Caulerpa racemosa, Caulerpa peltata, Struvea anastomosans, Zonaria variegata, Padina tetrastromatica, Dictyota sp., J. adhaerens, and L. majuscula were the dominant epiphytic species. Seasonal trend in total epiphytic density was the same in both the culture with maximum density during autumn season (192 +/- 41 epiphytes m(-2) in raft; 498 +/- 10 epiphytes m(-2) in concrete block) and minimum during northeast monsoon season (112 +/- 5 epiphytes m(-2) in raft; 247 +/- 1 epiphytes m(-2) in concrete block). Seasonal variations in dominant epiphyte density followed the trend of total epiphytes with highest in monsoon and autumn seasons. Salinity showed significant positive correlation with epiphyte density (r = 0.63, P = < 0.05), while temperature showed strong negative correlation ( r = -0.63, P < 0.05; r = -0.77, P < 0.01). Light microscopic study and scanning electron microscopic study revealed the extent of penetration of epiphytes into host cortex cell. However, this should be confirmed with a transmission electron microscopic study. The results in this paper will be useful to the farmers in understanding the impact of epiphytes on crop yield and define the strategies to avoid epiphytes on G. acerosa in cultivation.