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Research Training Group 2530
RTG2530Biota-mediated effects on Carbon cycling in Estuaries

Photo: UHH/RTG2530

Research theme C

Biota-mediated C fluxes across marsh-water boundaries

C fluxes among estuarine marshes, intertidal flats and subtidal channels can largely influence productivity, organic matter (OM) degradation and food web structure. C fluxes across marsh-water boundaries include C subsidies driven by abiotic factors, and C fluxes mediated by trophic interactions among organisms and consumer motility. Biota and their interactions may control the quality of C compounds and the quantity of the respective C fluxes across marsh-water boundaries.

As marsh plant community structure is controlled by herbivory, plant-herbivore interactions may also determine the quantity and quality of litter which is directly flushed in estuarine waters. Plant-microbe interactions in the rhizosphere affect the amount of dissolved organic and inorganic C and particulate organic C contained in pore water and exported to estuarine waters. In addition, microphytobenthos communities and their interactions with microbes and herbivores affect the export of C to subtidal channels. Motility of aquatic consumers (e.g. foraging movements and ontogenetic migration of fish in intertidal creeks) can lead to C fluxes from marshes and intertidal flats to estuarine channels impacting aquatic productivity and food web structure.

Considering the supply of subsidies from estuarine channels and intertidal flats to marshes, dep-osition of aggregates and debris of biota occurs during regular tidal flooding of marshes. These aquatic subsidies may shape productivity and food web structure in marsh ecosystems. Microbial degradation of OM in phycospheres may additionally determine the quantity and quality of aquatic subsidies to marshes and their effect on marsh consumer populations and biological communities. Consumer motility may also affect water-marsh C fluxes as e.g. birds can feed in estuarine waters and on intertidal flats and deposit nutrient-rich fecal matter in marshes.

While the relevance of C fluxes across marsh-water boundaries in driving estuarine trophodynamics is increasingly recognized, little is known on (i) the role of rhizosphere, and phycosphere processes and of consumer effects in regulating these fluxes, and on (ii) the impact of C fluxes on consumer populations and communities.

Doctoral projects within RT C will address the following research questions:

  • How do rhizosphere and phycosphere processes control C turnover across marsh-water boundaries?
  • How is C turnover across marsh-water boundaries mediated by trophic interactions?
  • How are C fluxes across marsh-water boundaries affecting terrestrial and aquatic consumer populations and communities?