Dataset Information

Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem.

ABSTRACT: Subterranean estuaries extend inland into density-stratified coastal carbonate aquifers containing a surprising diversity of endemic animals (mostly crustaceans) within a highly oligotrophic habitat. How complex ecosystems (termed anchialine) thrive in this globally distributed, cryptic environment is poorly understood. Here, we demonstrate that a microbial loop shuttles methane and dissolved organic carbon (DOC) to higher trophic levels of the anchialine food web in the Yucatan Peninsula (Mexico). Methane and DOC production and consumption within the coastal groundwater correspond with a microbial community capable of methanotrophy, heterotrophy, and chemoautotrophy, based on characterization by 16S rRNA gene amplicon sequencing and respiratory quinone composition. Fatty acid and bulk stable carbon isotope values of cave-adapted shrimp suggest that carbon from methanotrophic bacteria comprises 21% of their diet, on average. These findings reveal a heretofore unrecognized subterranean methane sink and contribute to our understanding of the carbon cycle and ecosystem function of karst subterranean estuaries.

SUBMITTER: Brankovits D

PROVIDER: S-EPMC5703975 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

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Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem.

Brankovits D D Pohlman J W JW Niemann H H Leigh M B MB Leewis M C MC Becker K W KW Iliffe T M TM Alvarez F F Lehmann M F MF Phillips B B

Nature communications 20171128 1

Subterranean estuaries extend inland into density-stratified coastal carbonate aquifers containing a surprising diversity of endemic animals (mostly crustaceans) within a highly oligotrophic habitat. How complex ecosystems (termed anchialine) thrive in this globally distributed, cryptic environment is poorly understood. Here, we demonstrate that a microbial loop shuttles methane and dissolved organic carbon (DOC) to higher trophic levels of the anchialine food web in the Yucatan Peninsula (Mexic ...[more]

PMID: 29180666

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Project description:Dissolved organic matter (DOM) is ubiquitous in natural waters and plays a central role in the biogeochemistry in riverine, estuarine and marine environments. This study quantifies and characterizes solid-phase extractable DOM and trace element complexation at different salinities in the Weser and Elbe River, northern Germany, and the North Sea. Dissolved organic carbon (DOC), total dissolved nitrogen (TDN), Co and Cu concentrations were analyzed in original water samples. Solid-phase extracted (SPE) water samples were analyzed for DOC (DOCSPE), dissolved organic nitrogen (DONSPE), sulfur (DOSSPE) and trace metal (51V, 52Cr, 59Co, 60Ni, 63Cu, 75As) concentrations. Additionally, different pre-treatment conditions (acidification vs. non-acidification prior to SPE) were tested. In agreement with previous studies, acidification led to generally higher recoveries for DOM and trace metals. Overall, higher DOM and trace metal concentrations and subsequently higher complexation of trace metals with carbon and sulfur-containing organic complexes were found in riverine compared to marine samples. With increasing salinity, the concentrations of DOM decreased due to estuarine mixing. However, the slightly lower relative decrease of both, DOCSPE and DONSPE (~77%) compared to DOSSPE (~86%) suggests slightly faster removal processes for DOSSPE. A similar distribution of trace metal and carbon and sulfur containing DOM concentrations with salinity indicates complexation of trace metals with organic ligands. This is further supported by an increase in Co and Cu concentration after oxidation of organic complexes by UV treatment. Additionally, the complexation of metals with organic ligands (analyzed by comparing metal/DOCSPE and metal/DOSSPE ratios) decreased in the order Cu > As > Ni > Cr > Co and thus followed the Irving-Williams order. Differences in riverine and marine trace metal containing DOMSPE are summarized by their average molar ratios of (C107N4P0.013S1)1000V0.05Cr0.33Co0.19Ni0.39Cu3.41As0.47 in the riverine endmember and (C163N7P0.055S1)1000V0.05Cr0.47Co0.16Ni0.07Cu4.05As0.58 in the marine endmember.

Project description:Dissolved organic phosphorus (DOP) is an important nutrient for phytoplankton growth in oligotrophic oceans. However, little is known about the impact of DOP on phytoplankton growth in eutrophic waters. In the present study, we conducted field monitoring as well as in situ and laboratory experiments in the Pearl River estuary (PRE). Field observations showed an increase in the nitrogen-to-phosphorus ratio and DOP in recent years in the PRE. The phytoplankton community was dominated by nanophytoplankton Cyclotella in the upper and middle estuary, with high concentrations of DOP and light limitation during the ebb stage of the spring to neap tide in summer. The relative abundance of Cyclotella in natural waters was higher after enrichment with estuarine water with a background of 0.40-0.46 µM DOP, even when dissolved inorganic phosphorus was sufficient (0.55-0.76 µM). In addition, the relative abundance of Cyclotella in natural waters was higher after enrichment with phosphoesters. Laboratory culture results also confirmed that phosphoesters can enhance the growth rate of Cyclotella cryptica. Our study highlights that Cyclotella can become the dominant species in estuaries with increased levels of phosphoesters and low and fluctuating light adaptability and under the joint effect of dynamic processes such as upwelling and tides. Our results provide new insights into the role of Cyclotella in biogeochemical cycles affected by DOP utilization and potential applications in relieving the hypoxia of tropical eutrophic estuaries.IMPORTANCEThis study provides evidence that Cyclotella can become the dominant species in estuaries with increased levels of phosphoesters and low and fluctuating light adaptability and under the joint effect of dynamic processes such as upwelling and tides. Our study provides new insights into the role of Cyclotella in biogeochemical cycles affected by dissolved organic phosphorus utilization, especially affected by anthropogenic inputs and climate change. Potential applications include relieving the hypoxia of tropical eutrophic estuaries.

Dataset Information

Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem.

Publications

Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem.

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