Larvacean (Chordata, Tunicata) abundance and inferred secondary production off southeastern Brazil Leonardo K. Miyashita * , Rubens M. Lopes Department of Biological Oceanography, Oceanographic Institute, University of São Paulo, Praça do Oceanográfico 191, Cidade Universitária, São Paulo, SP 05508-120, Brazil article info Article history: Received 22 May 2010 Accepted 15 January 2011 Available online 25 January 2011 Keywords: Appendicularia abundance biomass secondary production Brazil Ubatuba abstract We studied the temporal and vertical variability in larvacean abundance and secondary production on a fixed station off southeast Brazil, from January 2007 to December 2008. Larvacean biomass was derived from lengtheweight regressions, and growth rates were estimated from an empirical model. We iden- tified eleven larvacean species. Oikopleura longicauda occurred throughout the studied period and was the most abundant species, followed by Oikopleura fusiformis. Fritillaria haplostoma, O. fusiformis and O. longicauda were found mainly above the thermocline, whereas Oikopleura dioica and Fritillaria pellucida preferred bottom layers. Higher abundance and biomass were observed in warmer months, when the water column was stratified as a result of the bottom intrusions of the cold and nutrient-rich South Atlantic Central Water. Secondary production mirrored the biomass seasonal pattern. Larvacean biomass equaled to less than 10% of copepod biomass during the same period, but larvacean production comprised on average 77% that of copepods, whereas the production of discarded houses and fecal pellets comprised up to 2800% of larvaceans secondary production. This confirms the potential signifi- cance of larvaceans in the carbon flux in tropical and subtropical coastal regions. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Larvaceans are pelagic tunicates that comprise one of the most abundant mesozooplankton taxa in marine ecosystems (Gorsky and Fenaux, 1998). Larvaceans live within an external mucous structure known as “house”, containing an embedded filtration apparatus that allows them to feed on particles as small as 0.2 mm(Flood et al., 1992), including colloids, bacterioplankton, heterotrophic protists and phytoplankton (Flood et al., 1992; Vargas and González, 2004). A new house is periodically secreted by the epidermal glandular epithelium, whereas the old house, usually clogged with uneaten particles and fecal pellets, is discarded (Alldredge, 1976; Hansen et al., 1996). The house renewal rate ranges from 2 to 40 houses d 1 , varying according to temperature (Sato et al., 2003), salinity (Sato et al., 2001), and food concentration (Lombard et al., 2009a). Discarded houses are major components of macroscopic aggregates influencing carbon vertical flux (Taguchi, 1982; Alldredge, 2005; Robison et al., 2005), and serving as food and substrate to other organisms (Alldredge, 1976; Koski et al., 2007). Because of their feeding mode larvaceans play a key role in the microbial food web (Flood et al., 1992; Vargas and González, 2004), and as they serve as food to large invertebrates and commercial fish (Liang and Vega-Pérez, 1995; Llopiz et al., 2010), larvaceans also impact the classical food chain (Purcell et al., 2005). There is a growing evidence that larvaceans are major contributors to the pelagic secondary production in oligotrophic to mesotrophic coastal and oceanic waters (Hopcroft and Roff, 1998; Sato et al., 2008; Jaspers et al., 2009) as a result of their high carbon assimi- lation efficiency under low to medium food concentration (López- Urrutia et al., 2003a; Lombard et al., 2009b). Coastal ecosystems off southeast Brazil are characterized by oligo- to mesotrophic conditions as a result of scattered, low- volume riverine input together with remote influences of oligo- trophic oceanic water transported by the Brazil Current in the vicinities of the shelf break (Castro et al., 2006). Off Brazil, previous studies on larvaceans have emphasized their occurrence and distribution (e.g., Björnberg and Forneris, 1956; Forneris, 1965; Fenaux, 1967; Matsumura-Tundisi, 1970; Esnal and Castro, 1977), and no data exist on biomass and production. Here, we analyzed the seasonal variability of larvacean abundance and production during two years, on a neritic ecosystem off southeastern Brazil. 2. Material and methods 2.1. Study area The fixed station (23  36 0 S, 44  58 0 W) was located on the inner continental shelf, on the 40-m isobath, and approximately 12 * Corresponding author. E-mail address: leonardo.miyashita@usp.br (L.K. Miyashita). Contents lists available at ScienceDirect Estuarine, Coastal and Shelf Science journal homepage: www.elsevier.com/locate/ecss 0272-7714/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecss.2011.01.007 Estuarine, Coastal and Shelf Science 92 (2011) 367e375