A review of intertidal rocky shore Community at Mar del Plata (Argentina).

PABLO E. PENCHASZADEH

KOBE

Congreso; KOBE NAGISA WORLD CONGRESS 2006; 2006

Census of Marine Life

In the rocky shores of Mar del plata (38°W 04´S), intertidal mussels monopolize themacrofauna communities developing beds dominated by the small mytilid Brachidontesrodriguezii. This species covers 45% to 65% of the mid and upper mid intertidal substrate formingstratified beds. Vertical protected substrates of the midlittoral show the highest densities of B.rodriguezii, up to 175,000 indiv. m" representing a dry biomass of 1,670 g. m"; upper horizontalsubstrates at the same level show lower densities (80,000 indiv. m": 592 g. m"). The horizontal bedmatrix accumulates more sand than vertical beds (19.lkg. m? and 5.1kg. m´, respectively).Twenty-six taxa and 14 animal species were recorded within the B. rodriguezii intertidal matrixwhile a total of 9 algae species were found living on the mussel bed. The pulmonate limpetSiphonaria lessoni is the main intertidal herbivore. The invasive barnac1e species, Balanusglandula, was first detected in Mar del Plata in 1974 and today creates an upper midlittoral fringeat densities up to 5,000 indiv.m´. This review of the Mar del Plata rocky shore communitysurnmarizes the existing information as we prepare to sample this area with the NaGISA protocols.The uniqueness of the rocky intertidal of Mar del Plata is the absolute dominance of a singlemussel species Brachidontes rodriguezii in the midlittoral, the presence of a sol e species ofGastropoda, the grazer pulmonate Siphonaria lessoni and the absence, until the mid sixties, of abamac1e belt.