The rocky shores contain a large number of species of economic and ecological importance.
In this environment, the high productivity in the substrate gives an appropriate condition for
the settlement of benthic species and the fixation of sessile organisms. Primary production is
performed by the microphytobenthic component of biofilm epilithic. The objective of this
work was to evaluate the temporal variation of the Neritina zebra gastropod and its
relationships with the primary epilithic biomass on the consolidated substrate of the beaches
of Paraiso, Farol and Grande da Ilha de Mosqueiro-Pará. The samplings occurred in the
months of May and October of 2014 and 2017, corresponding to months of the rainy and dry
period, respectively. The densities of recruits, intermediates and adults were estimated to
measure the influence of different size classes on biofilm availability. For the density samples,
25 x 25 cm square samplers were used and 10 replicates were made on each beach, and for the
samples destined for chlorophyll-a extraction, used as an indirect measure of the primary
production, fragments of rocks of approximately 3 x 3 cm. The biomass primary of the
consolidated substrate of the Mosqueiro-PA intertidal shows higher production of the
epileptic biofilm in the dry period and is related to the lower densities of Neritina zebra. The
recruitment of individuals of Neritina zebra occurs in the rainy season and presents
interannual variation. The relationship between the class of intermediates and the
concentration of chlorophyll a has a negative tendency, ie, the higher densities of this class of
size are associated with the lower rates of chl-a. Thus, understanding the relationships
between different size classes over primary production is crucial to understanding the
mechanisms involved in population control.
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