Benthic diversity and assemblage structure of a north Patagonian rocky shore: a monitoring legacy of the NaGISA project

M. E. RECHIMONT; GALVAN D; SUEIRO M.C; CASAS G; PIRIZ M.L; DIEZ ME; PRIMOST M; ZABALA MARIA SOLEDAD; MARQUEZ F; BROGGER M; JOSE E. F. ALFAYA; BIGATTI GREGORIO

JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2013 vol. 93 p. 2049 - 2058

0025-3154

The rocky shore of Punta Este, Golfo Nuevo (Patagonia, Argentina), was sampled by means of the standardized NaGISA(CoML) protocol, that was aimed to generate biodiversity baseline data in six levels, from high intertidal to 10 m depth.Based on the generated data, we analysed the benthic assemblage structure, species richness, mean abundance and the distributionpattern of invertebrate functional groups, typifying species in each intertidal and subtidal level. The intertidalsampled is exposed to extreme physical conditions higher than any other rocky shore system studied, with air temperaturevariation of 408C during the year, maximum winds of 90 km/h and semidiurnal tides of 5 m amplitude; on the otherhand subtidal presents less thermal variation (DT 108C throughout the year) and more homogeneous physical conditions.We identified 64 taxa represented by six animal phyla: Mollusca, Arthropoda, Annelida (Polychaeta), Echinodermata,Cnidaria and Nemertea; and three algal phyla: Chlorophyta, Rhodophyta and Heterokontophyta (class: Phaeophyceae).Ordination non-metric multidimensional scaling plots showed three different assemblages in terms of species composition(intertidal, subtidal 1 m level and subtidal 5?10 m levels). The intertidal was represented by suspension feeders, mainlyMollusca. The tiny mussels Brachidontes rodriguezii and Brachidontes purpuratus, and the algae Corallina officinalis dominatedthe intertidal and promote positive interaction (amelioration), preventing other species from the extreme physical stress.The subtidal was mainly represented by grazers. Our results showed a tendency of suspension feeders to decrease and grazersand predators to increase from high intertidal to subtidal, probably driven by decreasing physical stress. The gastropod Tegulapatagonica, the sea urchins Arbacia dufresnii and Pseudechinus magellanicus and the invasive algae Undaria pinnatifidawere the most abundant species in 1 m?10 m levels. Based on previous work performed in the region, we hypothesize thatthe differences registered between intertidal and subtidal levels could be explained in part by an increase in physical stressat the intertidal, with low predation pressure that promotes positive interactions, while in the subtidal the increase in consumersand decrease of physical stress could lead to associational defences. Our results could be useful as baseline data todevelop a sustainable network for long-term monitoring of benthic community changes due to anthropogenic activities.