Bacterial carbon flow in the Humboldt Current System off Chile

Abstract

During this study, bacterial secondary production (BSP) was measured at 3 coastal upwelling sites (Antofagasta, latitude 23°S; Coquimbo, latitude 30°S; and Concepción, latitude 36°S) within the Humboldt Current System (HCS) off Chile. The data show that bacteria are an important component of pelagic food webs in these areas. The coastal area of Antofagasta had the highest level of bacterial activity (1722 ± 1362 mgCm-2 d-1), the coastal area of Coquimbo the values (77 ± 56 mgC m-2 d-1). The low levels observed in Coquimbo are in agreement with the observation that Coquimbo is an oligotrophic area of persistent upwelling that persistently shows low primay production (PP) values. A BSP value of ca. 5000 mgC m-2 d-1 measured during this study in the coastal area of Antofagasta constitutes the highest BSP value ever reported in the literature. In the 3 upwelling areas sampled a significant proportion of the PP was utilised by bacteria (ca. 63 to 96% in Antofagasta, 16 to 34% in Coquimbo and 10 to 24% in Concepción). A strong correlation between BSP and PP was found during this study (r2 = 0.57, n = 51), reflecting a tight coupling between carbon synthesis and bacterial consumption. The high correlation between PP and BSP, coupled with the lack of correlation between temperature and BSP (r2 = 0.0, n = 420), indicates that in the HCS off Chile substrate availability seems to be more important than temperature in limiting bacterial activity and abundance.