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

RECHIMONT, M.E; GALVÁN, D; SUEIRO, M.C.; CASAS, G; PIRIZ, M.L.; DIEZ, M.E.; PRIMOST, M; ZABALA, M.S; MARQUEZ, F; BROGGER, M; ALFAYA, J.E.F.; BIGATTI, G

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 ofthe standardized NaGISA (CoML) protocol, that was aimed to generate biodiversity baselinedata in 6 levels, from high intertidal to 10m depth. Based on the generated data, we analyzed thebenthic assemblage structure, species richness, mean abundance and the distribution pattern ofinvertebrate functional groups, typifying species in each intertidal and subtidal level. Theintertidal sampled is exposed to extreme physical conditions higher than any other rocky shoresystem studied, with air temperature variation of 40°C during the year, maximum winds of 90km/h and semidiurnal tides of 5m amplitude; on the other hand subtidal presents less thermalvariation (ΔT 10°C along the year) and more homogeneous physical conditions. We identified64 taxa represented by six animal phyla: Mollusca, Arthropoda, Annelida (Polychaeta),Echinodermata, Cnidaria and Nemertea; and three algal phyla: Chlorophyta, Rhodophyta andHeterokontophyta (class: Phaeophyceae). Ordination nMDS plots showed three differentassemblages in terms of species composition (intertidal, subtidal 1m level and subtidal 5-10mlevels). The intertidal was represented by suspension feeders, mainly Mollusca. The tinymussels Brachidontes rodriguezii and Brachidontes purpuratus, and the algae Corallinaofficinalis dominated the intertidal and acts as a buffer that prevents other species for theextreme physical stress. The subtidal was mainly represented by grazers. Our results showed atendency of suspension feeders decreasing and increasing of grazers and predators from highintertidal to subtidal, probably driven by decreasing in physical stress. The gastropod Tegulapatagonica, the sea urchins Arbacia dufresnii and Pseudechinus magellanicus and the invasivealgae Undaria pinnatifida were the most abundant species in 1m-10m levels. Based on previousworks performed in the region, we hypothesize that the differences registered between intertidaland subtidal levels could be explained in part by an increase in physical stress at the intertidalwith low predation pressure that promotes positive interactions, while in the subtidal theincreasing in consumers and decreasing of physical stress could lead to associational defenses.Our results could be useful as baseline data to develop a sustainable network for long-termmonitoring benthic community changes due to anthropogenic activities.