Bacterial community composition and colored dissolved organic matter in a coastal upwelling ecosystem

Abstract

The aim of the present study was to correlate changes in dissolved organic matter (DOM) composition, as characterized through humic-and protein-like fluorescence, with changes in the abundance of major bacterial groups (Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Bacteroidetes) and bacterial activity in an upwelling system during the season of low productivity. Sampling was conducted under 2 contrasting periods characterized by low (February) and high (October) precipitation. In October, the mean humic-like DOM fluorescence in surface waters (3.1 ppb equivalents of quinine sulphate [ppb QS]) was higher than the annual average for this coastal zone (2.2 ppb QS), which was attributed to enhanced continental runoff. Alphaproteobacteria and Bacteroidetes were the most abundant groups, accounting for about 13 and 16% of total bacterial abundance, respectively. Betaproteobacteria were detectable only during the rainy period, accounting for 2 to 9% of total bacterial abundance. The bulk dissolved organic carbon concentration similarly explained the relative abundance of Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria (ca. 50% of total variability). By contrast, a strong correlation was found between the humic-like DOM fluorescence and the relative abundance of the Betaproteobacteria group, explaining 68% of the total variability. Multivariate linear regression analyses revealed that the relative abundance of Betaproteobacteria has the greatest influence on bacterial carbon fluxes, explaining 61 and 65% of bulk bacterial activity and biomass variability, respectively. Despite their relatively low abundance, Betaproteobacteria might play a relevant biogeochemical role in this coastal transition ecosystem during the low productivity period as allochthonous DOM consumers. KEY WORDS: Colored dissolved organic matter · Bacterial community composition · Bacterial production · Northwest Spain Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 55: [131][132][133][134][135][136][137][138][139][140][141][142] 2009 microautoradiography and fluorescence in situ hybridization (FISH) (e.g. Cottrell & Kirchman 2000, AlonsoSáez & Gasol 2007, have been used to unravel the links between bacterial function and diversity in a wide variety of marine pelagic environments. These types of studies have revealed systematic differences in the uptake patterns of specific organic compounds among major phylogenetic groups. Alphaproteobacteria seem to mostly contribute to low molecular weight (LMW) DOM utilization (glucose, amino acids, DMSP), whereas Bacteroidetes appear to be proficient in the use of proteins and other plankton-derived high molecular weight (HMW) compounds. Several studies in lakes and estuaries have also reported changes in bacterial community structure and function associated to shifts in terrestrial organic matter influx. By comparison, little is known about the patterns of utilization of allochthonous carbon sources, such as those d...

Growth rates of different phylogenetic bacterioplankton groups in a coastal upwelling system

“…On the other hand, SAR11 showed a positive correlation with ammonium and negative with DOC concentration, FDOM‐T and bacterial abundance, which confirm the tendency of this group to thrive in oligotrophic waters. Betaproteobacteria correlated positively with the fluorescence of humic‐like dissolved organic matter (FDOM‐M), indicative of refractory substrates, and negatively with salinity; in accordance with Teira and colleagues (2009), who linked the occurrence of this group in marine environments to freshwater influence.…”

Marine Microbial Community Composition During the Upwelling Season in the Southern Benguela

“…The significant split in picoeukaryote community structure from November to February confirms a seasonal shift in the picoeukaryote community as the upwelling season progresses. Likewise, the split in community structure from shelf to offshore in February vs. the lack of one in November (especially for picoeukaryotes) illustrates upwelling-induced spatial variability, as shown in other upwelling systems in the California current and off northwest Africa (Baltar et al, 2007;Alonso-Gutiérrez et al, 2009;Teira et al, 2009;Allen et al, 2012).…”

“…Few studies have focused on the microbial composition of plankton communities of the world's upwelling regions. These include Painting (1989) who also focused on the Southern Benguela, Kerkhof et al (1999) investigated the North Atlantic just off the New Jersey coast, Suzuki et al (2001) investigated an upwelling region in Monterey Bay in the NE Pacific and Teira et al (2009) studied six key bacterial groups in the Northwest Iberian Peninsula coastal upwelling waters. Only a handful of studies have included next generation sequencing techniques, which are capable of describing community diversity and structure in great detail (e.g., Bergen et al, 2015;Aldunate et al, 2018).…”

Consequences of increased terrestrial dissolved organic matter and temperature on bacterioplankton community composition during a Baltic Sea mesocosm experiment

“…Increases in terrigenous organic matter could induce changes in food web dynamics and energy flows in the system (Sandberg et al 2004 ; Wikner and Andersson 2012 ). Although the importance of DOM composition in structuring bacterioplankton communities is relatively well established (where phytoplankton-derived compounds are most studied, e.g., Gomez-Consarnau et al 2012 ; Teeling et al 2012 ; Dinasquet et al 2013 ), few studies have considered the importance of tDOM input (mainly humic substances derived from river runoff) in driving bacterioplankton compositional shifts in marine systems (but see Kisand et al 2002 ; Rochelle-Newall et al 2004 ; Kisand et al 2008 ; Teira et al 2009 ; Grubisic et al 2012 ; Rocker et al 2012 ). However, the impact of humic matter on bacterioplankton composition has been extensively investigated in limnic systems (e.g., Lindström 2000 ; Eiler et al 2003 ; Kritzberg et al 2006 ).…”