No abstract

), respectively, from winter to spring. In addition, the bacterial secondary production to primary production (BSP:PP) ratio decreased from 3.7 to 0.2 in Reloncaví Fjord, suggesting a transition from microbial to classical pelagic food webs. The higher solar radiation and extended photoperiod of springtime promoted the growth of diatoms in a nutrient-replete water column. Allochthonous (river discharge) and autochthonous (phytoplankton exudates) organic matter maintained high year-round bacteria biomass and secondary production. In spring, grazing pressure from zooplankton on the microplankton (largely diatoms) resulted in the relative dominance of the classical food web, with increased export production of zooplankton faecal pellets and ungrazed diatoms. Conversely, in winter, zooplankton grazing, mainly on nanoplankton, resulted in a relative dominance of the microbial loop with lower export production than found in spring. Carbon fluxes and fjord-system functioning are highly variable on a seasonal basis, and both the multivorous trophic webs and the carbon export were more uncoupled from local PP than coastal areas.

Resumen.-Es ampliamente reconocida la utilización de estuarios como zonas de crianza para peces e invertebrados, pero el éxito en la explotación de los recursos variará entre las especies residentes del estuario y las oportunistas. Se estudió la distribución y dieta de larvas de Myxodes viridis (Pisces, Clinidae) en 2 localidades del estuario de Bahía Corral (estuarioarriba y estuario-abajo), uno de los estuarios más grandes del sur de Chile, durante la primavera austral de 2009 a 3 profundidades (superficie, picnoclina, profundo) durante la fase llenante y vaciante de 4 ciclos mareales. Las larvas fueron recolectadas principalmente en la estación estuario-abajo durante fase vaciante. La incidencia alimentaria también fue mayor en la fase vaciante; las larvas cambiaron de omnivoría a carnivoría a medida que se desarrollaban, depredando principalmente sobre nauplii y copepoditos calanoideos. Aunque el éxito alimentario fue similar para cada estado de desarrollo en la columna de agua, la dieta de larvas en preflexión y flexión estuvo basada en diferentes ítems presa dentro de los primeros 3-4 m de la columna de agua (superficie y picnoclina) con respecto de aguas más profundas (7-10 m, cerca del fondo). Esto sugiere que la picnoclina pudiera afectar la composición de la dieta de larvas pequeñas de M. viridis, pero no el tamaño, número o volumen de presas ingeridas. Además, ya que el forrajeo está basado predominantemente en diferentes estados de desarrollo de copépodos, las larvas que emergen durante vaciante pueden incrementar la advección fuera del estuario hacia zonas costeras cercanas, indicando que esta especie no es un usuario frecuente del estuario durante su desarrollo larval. Palabras clave: Myxodes viridis, ictioplancton, éxito alimentario, Bahía CorralAbstract.-The utilization of estuaries as nursery zones for fish and invertebrates is widely known, but differences in the success of resource exploitation vary between resident and opportunistic estuarine species. The distribution and diet of larval Myxodes viridis (Pisces, Clinidae) were studied at 2 locations (up-estuary and down-estuary) in the Corral Bay estuary, one of the largest estuaries in southern Chile, during the austral spring 2009 at 3 depths (surface, pycnocline, deep) during the flood and ebb of 4 tidal cycles. Larvae were collected mostly at the down-estuary station during the ebb phase. Feeding incidence was also greater during the ebb phase; larvae changed from omnivory to carnivory as they developed, predating mainly on nauplii and calanoid copepodites. Although the feeding success was similar for each developmental stage along the water column, diet of preflexion and flexion larvae was different in the first 3-4 m depth (surface and pycnocline) in relation to deeper waters (7-10 m depth, near to the bottom). This suggests that the pycnocline may affect the composition of the diet of small, larval M. viridis but not the size, number or volume of ingested prey. Additionally, because foraging is predominantly based on the different life ...