Nitrification in a seagrass-sponge association

Abstract

In the Mediterranean Sea, the demosponge Chondrilla nucula can occur in close association with the native seagrass Posidonia oceanica. C. nucula harbors a diverse and abundant microbial community, including potential nitrifiers. Thus, the sponge may contribute to the nitrogen (N) demand of the seagrass holobiont. In this study, we investigated potential nitrification rates (PNR) and inorganic N fluxes within this association at a site where C. nucula covered 18 ± 3 % of the seagrass meadow area, during plant growth (spring) and senescence (autumn). Using incubation experiments with 15N-labeled ammonium, we measured PNR and inorganic N of the seagrass-sponge association, and of sponge and seagrass independently, under light and dark conditions. We supplemented these experiments with 16s rRNA gene amplicon sequencing to characterize the microbial community of the sponge. PNR was exclusively measured when the sponge was present (alone or in association with the seagrass). PNR was highest in the dark and when C. nucula was associated with the seagrass, ranging from 21 ± 7 to 267 ± 33 nmol N g DW-1 h-1 in spring and autumn, respectively. Sponge-mediated PNR can support 8% of the N demand of the P. oceanica holobiont during growth and 47 % during senescence. We identified key nitrifying bacterial and archaeal groups as members of the sponge’s microbial community. While C. nucula released inorganic N, potentially sustaining the seagrass, it benefitted from dissolved organic carbon released by P. oceanica. These results suggest that the interaction between C. nucula and P. oceanica is mutually beneficial, ultimately supporting and stabilizing the seagrass ecosystem.

Preprint

Citation

BibTeX citation:

@online{berlinghof2025,
  author = {Berlinghof, J and Montilla, L. M. and Meador, T and
    Gallucci, L and Giovannelli, D and Gruber-Vodicka, H and Maselli, M
    and Margiotta, F and Wild, C and Cardini, U.},
  title = {Nitrification in a Seagrass-Sponge Association},
  date = {2025-01-08},
  url = {https://www.luismmontilla.com/papers/berlinghof2025/},
  doi = {10.1101/2025.01.07.631680},
  langid = {en},
  abstract = {In the Mediterranean Sea, the demosponge *Chondrilla
    nucula* can occur in close association with the native seagrass
    *Posidonia oceanica*. *C. nucula* harbors a diverse and abundant
    microbial community, including potential nitrifiers. Thus, the
    sponge may contribute to the nitrogen (N) demand of the seagrass
    holobiont. In this study, we investigated potential nitrification
    rates (PNR) and inorganic N fluxes within this association at a site
    where *C. nucula* covered 18 ± 3 \% of the seagrass meadow area,
    during plant growth (spring) and senescence (autumn). Using
    incubation experiments with 15N-labeled ammonium, we measured PNR
    and inorganic N of the seagrass-sponge association, and of sponge
    and seagrass independently, under light and dark conditions. We
    supplemented these experiments with 16s rRNA gene amplicon
    sequencing to characterize the microbial community of the sponge.
    PNR was exclusively measured when the sponge was present (alone or
    in association with the seagrass). PNR was highest in the dark and
    when *C. nucula* was associated with the seagrass, ranging from 21 ±
    7 to 267 ± 33 nmol N g DW-1 h-1 in spring and autumn, respectively.
    Sponge-mediated PNR can support 8\% of the N demand of the *P.
    oceanica* holobiont during growth and 47 \% during senescence. We
    identified key nitrifying bacterial and archaeal groups as members
    of the sponge’s microbial community. While *C. nucula* released
    inorganic N, potentially sustaining the seagrass, it benefitted from
    dissolved organic carbon released by *P. oceanica*. These results
    suggest that the interaction between *C. nucula* and *P. oceanica*
    is mutually beneficial, ultimately supporting and stabilizing the
    seagrass ecosystem.}
}

For attribution, please cite this work as:

Berlinghof, J, L. M. Montilla, T Meador, L Gallucci, D Giovannelli, H Gruber-Vodicka, M Maselli, F Margiotta, C Wild, and U. Cardini. 2025. “Nitrification in a Seagrass-Sponge Association.” bioRxiv. January 8, 2025. https://doi.org/10.1101/2025.01.07.631680.