Grazing of selected genera of green, red and brown macroalgae

Abstract

Macrobenthic algae and grazers like gastropods, amphipods etc. eventually form a key component of intensified grazing ecosystem in rocky intertidal area. Grazing gastropods suppresses the abundance of canopy forming algal species, thus lead to a reduced algal diversity in the long term. We conducted feeding trials with single and mixed diet during a 28-Days indoor experiment to examine the grazing intensity among green, red and brown algae namely Ulva lactuta, Enteromorpha linza, Gelidium and Padina tetrastromatica following a gut content analysis of experimental gastropods such as Euchelus asper and Nerita oryzarum. Feeding experiments revealed that Euchelus asper consumed 70% Enteromorpha, 10% Ulva and about 10% Gelidium whereas, Nerita oryzarum consumed 45% Ulva and 10% Enteromorpha during single diet experiment. Euchelus asper showed its preference towards all experimental diet where as Nerita preferred Ulva to a greater extends than Enteromorpha and rest other combined diet. Our results showed a higher grazing pressure exerted by Euchelus asper might pose a threat for algal culture and form competition in animals of same trophic level intern affecting their population. Similar experiment may be useful to control mass canopy forming algal growth and habitat studies for grazing animals will also be attributed.