The role of Argopecten purpuratus shells structuring the soft bottom community in shallow waters of southern Peru

BETINA J. LOMOVASKY; PATRICIA A. GAMERO; LEONARDO ROMERO; FAUSTO N. FIRSTATER; GAMARRA SALAZAR, ALEX; FERNANDO J. HIDALGO; JUAN TARAZONA; OSCAR O. IRIBARNE

JOURNAL OF SEA RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 106 p. 14 - 26

1385-1101

Accumulation of Argopecten purpuratus shells often occurs after El Niño events in shallow waters ofIndependencia Bay (14°17´S?76°10´W; Pisco, Peru). Here we experimentally investigate the effects of theirshell accumulation on macrobenthos assemblages in soft bottom, shallow areas of the bay. A field experiment(from May 2006 to May 2007), including four treatments with different coverage levels of empty shells ofA. purpuratus, were randomly arranged in: (1) areas devoid of shells (?Empty? treatment: experimental control),(2) 50% of the plot area covered with shells haphazardly distributed over the bottom (?medium? treatment),(3) 100% of the plot area covered with shells, forming a 10 cmvalve layer (?full? treatment) and (4) ?natural control?.We found a total of 124 taxa throughout the experiment. Polychaetes, crustaceans and mollusks were themost abundant groups in ?natural controls?, dominated by the gastropod Nassarius gayi and the polychaetesPrionospio peruana, Platynereis bicanaliculata and Mediomastus branchiferus. The abundance of individuals(N) and the species richness (S) were higher in the ?medium? treatment, but only in one month under positivesea bottom thermal anomalies. Similarity analysis (Bray?Curtis) showed that ?natural control?, ?empty? and?full? treatments were more similar among them than the ?medium? treatment. Multidimensional analysisshowed no clear species association among treatments and a higher grouping among the samplings of Jun-06,Aug-06 and Nov-06. Our results also showed that the commercial crab Romaleon polyodon and thepolyplacophora Tonicia elegans were positively affected by shell accumulations (?medium? treatment), whilethe limpet Fissurella crassa was negatively affected. Our study shows that directly by changing habitat structureor indirectly by changing sediment characteristics, the addition of scallop shells to the soft bottomcan modify themacrobenthic assemblage; however, the seasonal oceanographic variability (e.g. upwelling, El Niño) could have stronger effects controlling this system than the presence of the shells itself