Patrones ecológicos en la comunidad de bacterias bentónicas del Sulfureto de Humboldt.
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Date
2013
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Universidad de Concepción
Abstract
Los microorganismos son componentes claves de los ecosistemas oceánicos, por lo que conocer su diversidad y distribución es crucial para comprender y anticipar sus respuestas a cambios ambientales. El Sistema de Corrientes de Humboldt (SCH) determina las características oceanográficas de gran parte del mar costero de Chile. Frente a la zona central de Chile, el SCH presenta una marcada variabilidad estacional, identificándose dos regímenes climático-oceanográficos contrastantes — primavera-verano y otoño-invierno — donde la principal variable que afecta al bentos sublitoral es la presencia o ausencia, respectivamente, de la denominada “Zona de Mínimo Oxígeno” disuelto (ZMO). Los sedimentos bajo la ZMO son ricos en compuestos sulfurados y constituyen el “Sulfureto de Humboldt”, hábitat de extensas y masivas comunidades de bacterias filamentosas multicelulares gigantes y de poco estudiadas poblaciones de bacterias clásicas, de eucariontes unicelulares y de pequeños metazoos. En el presente trabajo se presentan los patrones de riqueza específica y diversidad de las comunidades de bacterias bentónicas en la Bahía de Concepción y la plataforma continental adyacente y sus cambios en el tiempo y espacio. Para esto, se utilizó muestras de ADN de muestras bentónicas, obtenidas en cuatro estaciones de muestreo visitadas en diciembre 2007, abril 2008, septiembre 2008 y enero de 2009 y datos ambientales pertinentes. Usando métodos moleculares cultivo independientes (pirosecuenciación paralela masiva de la región V6 del gen 16S del ARN ribosomal) y la información molecular obtenida de cada bacteria, se crearon unidades taxonómicas operacionales (OTUs), basadas en criterios de similitud entre las secuencias V6. Esta técnica permite estudiar las comunidades de microorganismos presentes en muestras ambientales sin recurrir a la taxonomía clásica. En seguida, utilizando la información relativa a las OTUs y la correspondiente a las variables ambientales (temperatura, salinidad, oxígeno disuelto y surgencia producida por el viento), se investigaron los patrones espacio-temporales y las variables oceanográficas que mejor explican tales patrones. Comparadas con estudios similares en otras localidades, utilizando el mismo método, las bacterias del Sulfureto de Humboldt presentaron valores más altos de riqueza de especies y diversidad. Las estimaciones de riqueza de OTUs sugieren la existencia de 46.658 OTUs diferentes de los que sólo logramos recuperar el 33%. Usando el método del escalamiento multidimensional, se generaron grupos de OTUs asociados al periodo (estación del año) y a los sitios (estaciones) de muestreo. Al evaluar la significancia de los grupos observados, se encontró diferencias significativas asociadas a los periodos (estaciones del año) de muestreo, pero no así con las localidades (estaciones) de muestreo. El análisis para dilucidar la relación entre los patrones observados en las comunidades y las variables oceanográficas, indicó que la salinidad, la profundidad de la oxiclina <1 mL/L de oxígeno disuelto y la profundidad de las muestras bentónicas explican un 42,4% de la varianza observada. Los resultados de este trabajo dejan en evidencia una zona que presenta una comunidad bacteriana rica en especies y de alta diversidad cuya composición y estructura obedecen a un acoplamiento con la estacionalidad de los procesos oceanográficos regionales.
Because microorganisms are key components of ocean ecosystems, to know their diversity and distribution is essential to understand and anticipate responses of marine ecosystems to environmental changes. The Humboldt Current System (HCS) determines the oceanographic characteristics of most of the coastal sea of Chile. Off central Chile the HCS presents a marked seasonal variability with two contrasting climaticoceanographic regimes — spring-summer and fall-winter — where the variable that affects the sublittoral bentos is the presence or absence, respectively, of the so-called “Oxygen Minimum Zone”. The sediments under the OMZ are rich in sulfur compounds and constitute the “Humboldt Sulfuretum”, the habitat of extensive and massive communities of giant filamentous multicellular bacteria and of yet unsufficiently studied populations of classical bacteria, unicellular eukaryotes and small metazoans. In this work I present the patterns of species richness and diversity of the community of benthic bacteria of the Bay of Concepción and adjacent shelf and their temporal and spatial changes. For this I used data from four benthic sampling stations visited during December 2007, April 2008, September 2008 and January 2009. Using cultureindependent molecular methods (massive parallel pyrosequencing of the V6 region in the 16S rRNA gene) and the molecular information obtained for each bacterium, I created Operational Taxonomic Units (OTUs) based on the similarity of the V6 sequences. This technique allows community studies without reference to taxonomic identifications. I then used the OTUs-related information as well as that of the environmental variables (temperature, salinity, dissolved oxygen and wind-driven upwelling) to find the spatial and temporal patterns and identify the oceanographic variables that best explained those patterns. Compared with similar studies elsewhere, using the same method, the benthic bacteria of the Humboldt Sulfuretum showed higher species richness and diversity. Estimates of OTUs richness suggest the existence of 46.658 OTUs, of which I only recovered 33%. Using the multidimensional scaling method, groups of OTUs associated with the period (season) and sampling sites (stations) were generated. An evaluation of the significance of the observed groups significant differences associated with the period of sampling (seasons) but not with sampling locality (sampling station), were found. The analysis to elucidate the relationship between the observed community patterns and the oceanographic variables showed that salinity, depth of the oxycline <1 mL/L dissolved oxygen, and sampling depth, explained 42,4 % of the observed data variance. The results of this study contribute with evidence for a species-rich and high diversity bacteria community whose composition and structure results from the coupling with the seasonality of regional oceanographic processes.
Because microorganisms are key components of ocean ecosystems, to know their diversity and distribution is essential to understand and anticipate responses of marine ecosystems to environmental changes. The Humboldt Current System (HCS) determines the oceanographic characteristics of most of the coastal sea of Chile. Off central Chile the HCS presents a marked seasonal variability with two contrasting climaticoceanographic regimes — spring-summer and fall-winter — where the variable that affects the sublittoral bentos is the presence or absence, respectively, of the so-called “Oxygen Minimum Zone”. The sediments under the OMZ are rich in sulfur compounds and constitute the “Humboldt Sulfuretum”, the habitat of extensive and massive communities of giant filamentous multicellular bacteria and of yet unsufficiently studied populations of classical bacteria, unicellular eukaryotes and small metazoans. In this work I present the patterns of species richness and diversity of the community of benthic bacteria of the Bay of Concepción and adjacent shelf and their temporal and spatial changes. For this I used data from four benthic sampling stations visited during December 2007, April 2008, September 2008 and January 2009. Using cultureindependent molecular methods (massive parallel pyrosequencing of the V6 region in the 16S rRNA gene) and the molecular information obtained for each bacterium, I created Operational Taxonomic Units (OTUs) based on the similarity of the V6 sequences. This technique allows community studies without reference to taxonomic identifications. I then used the OTUs-related information as well as that of the environmental variables (temperature, salinity, dissolved oxygen and wind-driven upwelling) to find the spatial and temporal patterns and identify the oceanographic variables that best explained those patterns. Compared with similar studies elsewhere, using the same method, the benthic bacteria of the Humboldt Sulfuretum showed higher species richness and diversity. Estimates of OTUs richness suggest the existence of 46.658 OTUs, of which I only recovered 33%. Using the multidimensional scaling method, groups of OTUs associated with the period (season) and sampling sites (stations) were generated. An evaluation of the significance of the observed groups significant differences associated with the period of sampling (seasons) but not with sampling locality (sampling station), were found. The analysis to elucidate the relationship between the observed community patterns and the oceanographic variables showed that salinity, depth of the oxycline <1 mL/L dissolved oxygen, and sampling depth, explained 42,4 % of the observed data variance. The results of this study contribute with evidence for a species-rich and high diversity bacteria community whose composition and structure results from the coupling with the seasonality of regional oceanographic processes.
Description
Tesis presentada para optar al título de Biólogo/a Marino/a.
Keywords
Diversidad bacteriana, Corrientes marítimas, Bahías Chile Octava región