Recovery of macrobenthos in defaunated tropical estuarine sediments Mônica L. Botter-Carvalho a,⇑ , Paulo V.V.C. Carvalho b , Paulo J.P. Santos c a Universidade Federal Rural de Pernambuco, Av. Dom Manoel de Medeiros s/n, Dois Irmãos 52171-900, Recife-PE, Brazil b Petrobras Transporte S/A (TRANSPETRO/DGN/GAS/TGN/NES/SMSOP), Rua Antônio Lumack Monte, 96, 4° andar 51020-905, Recife-PE, Brazil c Universidade Federal de Pernambuco, Av. Prof. Moraes Rêgo s/n, Cidade Universitária 50640-920, Recife-PE, Brazil article info Keywords: Brazil Estuary Field experiments Intertidal Macrozoobenthos Mesoscale abstract In the estuarine environment, hypoxia and/or anoxia have become a major cause of benthic defaunation and are strongly associated with increased eutrophication. Mesoscale field experiments were carried out to examine the recolonization and recovery time of macrobenthos after defaunation. Azoic sediments were achieved by covering four areas with polyethylene sheeting. Temporal changes and depth distribu- tion of macrobenthos within the defaunated sediments were compared with those in undisturbed natural sediments at the same site. Within 3 days, annelids appeared as the first immigrants. After 153 days, the process of recovery had not yet been completed in terms of species richness. Whereas diversity and even- ness showed no significant differences between treatments during the entire experiment, multivariate analyses proved that differences between treatments were still significant 93 days after the start of the experiment. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction A disturbance may be defined as any stochastic event that causes population changes, either due to density-independent mortality and/or to changes in the resource base of the community (Zajac and Whitlatch, 1982). Sediment disturbance is an important force structuring benthic communities (Diaz and Rosenberg, 1995), and is one of the most important ecological processes in maintain- ing the spatio-temporal heterogeneity of soft-bottom communities (Snelgrove et al., 1992). The effects of disturbance, recolonization and succession on the community structure of sediment-dwelling invertebrates have been a major focus in soft-bottom habitat stud- ies (Stocum and Plante, 2006). After disturbances, processes of recolonization followed by succession dynamics can re-establish the structure of the macrofaunal community (Guerra-García and García-Gomez, 2006). In the estuarine ecosystem, the macrobenthos is one of the structuring elements of the food web and plays an important role in the system dynamics (Herman et al., 1999). Surveys of macro- zoobenthic communities are useful tools for assessing short- and long-term changes in marine ecosystems, and thus for discriminat- ing between natural and man-induced disturbances. The estuarine infaunal community is well adapted to natural stress (e.g., tides and salinity). However, anthropogenic distur- bances have been an additional and growing cause of perturbations (Desprez et al., 1992) and frequently cause defaunation (Diaz and Rosenberg, 1995). In the estuarine environment, hypoxia and/or anoxia have become a major cause of benthic defaunation and are strongly associated with increased eutrophication (Gallagher et al., 1983). Recolonization depends on the frequency and inten- sity of hypoxia events (Diaz and Rosenberg, 1995). Experimental studies of recolonization, succession and recovery in soft-sediment habitats have been conducted primarily at micro- scales (e.g., Gamenick et al., 1996; Hall and Frid, 1998; Bolam et al., 2004; Lu and Wu, 2006), and only a small number at mesoscales (e.g., Thrush et al., 1996; Beukema et al., 1999; Dernie et al., 2003; Ritter et al., 2005). Dernie et al. (2003) suggested that the re- sults of microscale experiments be extrapolated only to the small- est disturbance area, but even for a given scale, recovery times for any biological parameter vary strongly among studies, from one day (Hall and Frid, 1998) to three months (Bolam et al., 2004) to re- cover macrofaunal abundance in microscale studies, for example. Besides this limited background, it should be noted that exper- imental studies of zoobenthos recovery are particularly rare for tropical or even subtropical marine ecosystems; the microscale study in a subtropical estuary by Faraco and Lana (2003) is the sin- gle study carried out along the more than 7000 km-long Brazilian coast. The aims of this study are to evaluate the recovery of the mac- rozoobenthos community in a tropical estuarine tidal flat after complete mesoscale defaunation due to hypoxia/anoxia, and to compare the main differences between tropical and temperate estuaries, considering the recovery times of the most commonly evaluated biological parameters. 0025-326X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2011.04.044 ⇑ Corresponding author. Tel.: +55 21 33206321; fax: +55 21 33206301. E-mail address: monica.botter@db.ufrpe.br (M.L. Botter-Carvalho). Marine Pollution Bulletin 62 (2011) 1867–1876 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul