MARINE ECOLOGY PROGRESS SERIES Vol. 319: 175–189, 2006 Published August 18 Mar Ecol Prog Ser Crustacean larvae distribution in the coastal upwelling zone off Central Chile B. Yannicelli1, 2,*, L. R. Castro1, 2, W. Schneider1, M. Sobarzo1 1Departamento de Oceanografía, Facultad de Ciencias Naturales y Oceanograficas, and 2Laboratorio de Oceanografia Pesquera y Ecología Larval (LOPEL), Universidad de Concepción, Casilla 160C, Concepción, Chile ABSTRACT: We present data on the stage abundance and spatial distribution of 5 taxa of crustacean larvae whose adult populations inhabit different depth ranges in the coastal area of central Chile (35 to 37°S). Our goal was to identify the relationship between the timing and depth range of larval release, with larval depth distribution and behavior, and offshore transport during early upwelling season (November) and upwelling reversal (March). Emerita analoga larvae were mainly released in the intertidal off phase in the season of maximum upwelling intensity. E. analoga was the shallowest larvae in this study, the most widespread in the horizontal plane and no diel vertical migrations were observed. Blepharipoda spinimana, another intertidal species, was always restricted to coastal stations and were mainly released during summer. It is a shallow species and, at our sampling scale, we could not identify vertical behavior. Libidoclaea granaria larvae were released in the continental shelf during the more intense upwelling season (November). Zoea I were widespread horizontally and zoea II appeared closer to the coast. They did not show vertical migration, they were found widespread in the water column and they were the deepest larvae. Larvae that migrated vertically (Neotrypaea unci- nata and Pagurus spp.) were released over a long period during the upwelling season (summer months), from the subtidal environment. Sub-surface waters were characterized by low oxygen and low temperature. Larval distribution depended on the spatial structure of upwelling circulation, larval behaviour and physiological tolerances as well as on the depth and timing of larval release. KEY WORDS: Crustacean larvae · Upwelling area · Vertical distribution · Larval transport · Across shore distribution · Spawning timing Resale or republication not permitted without written consent of the publisher INTRODUCTION 2002). Temporal upwelling dynamics involve intra annual cycles of upwelling intensity that affect off- Advection during the larval phases of benthic organ- shore/onshore advection of plankton and surface isms, which results from the interaction of physical nutrient enrichment. Inter-annually, varying upwelling oceanographic processes and larval behaviour, has intensities correlate with both the expansion and con- been suggested as a key factor determining site spe- traction of the latitudinal range of species (Sorte et al. cific settlement strength. Therefore they influence 2001), and their recruitment strengths (Connolly et al. benthic population and community dynamics (Con- 2001). Spatially, the local topography and coastline nolly & Roughgarden 1998, Wing et al. 1998a). In east- geometry enhance the development of mesoscale circ- ern boundary current (EBC) systems, the temporal and ulation features such as jets, filaments, eddies and spatial dynamics of wind-driven coastal upwelling is upwelling shadows. Upwelling shadows for example, thought to influence larval retention, concentration, might lead to the retention of organisms in coastal sites survival, transport and hence recruitment in both ver- down current from capes and points during upwelling tebrates and invertebrate populations (Lundquist et al. events (Wing et al. 1998b). Upwelling fronts influence 2000, Botsford 2001, Guisande et al. 2001, Flores et al. meroplankton coastal distribution (Bjorkstedt et al. *Email: [email protected] © Inter-Research 2006 · www.int-res.com 176 Mar Ecol Prog Ser 319: 175–189, 2006 1997). Eddies can retain organisms and/or maintain settlement patterns (Sponaugle et al. 2002). While sur- production sufficiently high for larvae to feed (Kasai et face dwelling organisms might be advected offshore al. 2002, Nishimoto & Washburn 2002), and filaments during upwelling events and they might later be trans- might transport larvae offshore (Rodriguez et al. 2001, ported shoreward during relaxation, the opposite is Hernández-León et al. 2002). true for deep dwelling zooplankton (Shanks 2000, The coupling of timing and location of larval release 2002, 2003, Sundby et al. 2001, Garland et al. 2002). with favourable spatio-temporal environmental condi- Those organisms that vertically migrate between tions enhance larval survival and recruitment (Cury & water layers flowing in opposite directions might be Roy 1989, Hinkley et al. 2001, Stenevik et al. 2003). If more concentrated nearshore (Peterson et al. 1979, advection is a relevant determinant for the success of Castro et al. 1993) reducing offshore loss and remain- larvae, then species-specific life history traits such as ing in a food rich media. Crustacean larvae in particu- spawning timing and location can be in tune with lar might show complex vertical swimming behav- advective environmental cycles (e.g. seasonal iours. Semi-diurnal, diurnal or ontogenetic depth upwelling cycle). However, the release, occurs within regulation has been described in a large set of crus- a species specific depth range, and an overall oceano- tacean species, and might arise from endogenous bio- graphic condition (e.g. upwelling circulation) might logical rhythms or environmentally induced behav- affect larvae released from different depths during the iours (Forward & Tankersley 2001, Naylor 2005). same season in opposite ways (e.g. shallow release off- Mechanisms favoring adequate larval advection could shore advection, sub-surface release onshore advec- appear during either the adult or larval phase. A rela- tion). tionship between larval vertical distribution and time In addition to the adult control of spawning timing of spawning has been suggested for larval fish, those and location, larval behaviour plays a role in its own that are spawned during the main upwelling season advection. Behaviour regarding vertical distribution are widespread in the water column (Olivar 1990). control interacts with prevailing hydrodynamics to Those organisms that release eggs (larvae) in surface shape distribution patterns, transport dynamics and waters might show a peak of spawning off phase with the main upwelling season (Castro et al. 2000). In this paper, we analyze the spatial distribution and abundance of the stages of 4 species and 1 genus of 0 15 30 km decapod crustacean larvae in the upwelling area of south central Chile (Fig. 1). Species were chosen I according to contrasting depth ranges of adult habitat. 35.0 We aimed to identify the relationship between larval II depth distribution, offshore distribution and the timing and depth range of larval release. We expected to find III Maule river strategies either in the adult or larval phase that 35.5 IV tended to minimize offshore advection. For example, larger numbers of early stages of non-migrating sur- V face larvae should be found offphase with the main Itata canyon VI upwelling season, or extended spawning periods in 36.0 Itata river species with migrating larvae. The ontogenetic distrib- VII ution (across-shore spreading and clumping) as a con- Itata sequence of vertical distribution, hatching period and VIII terrace depth, should evidence contrasting mechanisms of 36.5 IX shelf retention. For example, surface stages that show Concepcion bay limited depth control should appear more widespread, X less clumpy and farther offshore during upwelling than Bio-bio canyon Bio-bio river XI species that show depth control. In addition, deeper 37.0°S larvae should approach the coast during prevalence of Gulf of Arauco upwelling winds. We present data from 2 surveys conducted in spring and late summer along central Chile. Hydrographic 73.5°W 73.0 72.5 72.0 71.5 data and zooplankton stratified samples allowed the Fig. 1. South Central Chile coastal area with positions of CTD identification of major oceanographic features in the stations during November 2001 cruise. Roman numerals = area, and vertical and horizontal distribution patterns transects of crustacean larval stages. Our data suggested a rela- Yannicelli et al.: Coastal upwelling crustacean larvae distribution 177 tionship between larval across-shore and vertical dis- opment, and we identified 4 larval stages. The majid tribution, and adult spawning timing and depth range. Libidoclaea granaria, with 2 zoeal stages (Faguetti However, offshore distribution was strongly influenced 1969), was selected from below 100 m depth. Its larval by coastal geography. development is shorter than that of E. analoga (about a month at 15°C). Neotrypaea uncinata and pagurids inhabit subtidal bottoms, have 5 and 4 stages respec- MATERIALS AND METHODS tively, and longer larval development than L. granaria. At ambient temperature they developed through their Area studied. The study area (35 to 37°S) is located last zoea stage in between 40 to 50 d (Aste 1982, Lava- at the coastal (shelf) edge of the Humboldt Current dos 1982). system, a major EBC with a surface flow towards the Sampling. During 7 to 13 November 2001 and 7 to equator. Prevailing winds during austral spring and 12 March 2002 we conducted hydrographic and zoo- summer are southwesterly, and hence favor coastal plankton sampling over the continental shelf