Reciprocal nutritional benefits in a Mediterranean seagrass-sponge association

Abstract

Sponges commonly form associations within seagrass meadows, but their potential impact on seagrass productivity and nutrient cycles remains poorly understood. This study investigates the association between the demosponge Chondrilla nucula and the Mediterranean seagrass Posidonia oceanica in two sampling occasions during the plant growth (spring) and senescence (autumn) seasons at a small inlet near Naples, Italy, where the sponge grows conspicuously within the seagrass bed. We found a non-linear relationship between the benthic cover of the sponge and the seagrass, with higher C. nucula cover linked to intermediate P. oceanica cover, suggesting spatial dependence. Posidonia oceanica showed higher net primary production (NPP) in spring, while C. nucula was net heterotrophic in spring but exhibited near zero metabolic balance in autumn. NPP remained stable when the two organisms were associated, regardless of the season. Chondrilla nucula consistently contributed inorganic nutrients to the association in the form of phosphate, ammonium, and substantial nitrate, recycling nutrients that potentially benefited P. oceanica in its growth season. In return, the seagrass released dissolved organic carbon in spring , which is consistent with supporting sponge heterotrophic nutrition. These findings suggest reciprocal benefits in the interaction between C. nucula and P. oceanica, with nutrient exchange facilitating a facultative mutualism that potentially supports and stabilizes the productivity of the seagrass ecosystem.

Related items
Data and Code
Preprint

Citation

BibTeX citation:

@online{cardini2026,
  author = {Cardini, U. and Montilla, L. M. and Zapata-Hernández, G. and
    Berlinghof, J. and Guarcini, E. and Furia, M. and Margiotta, F. and
    Meador, T. and Wild, C. and Fraschetti, S. and Olivé, I.},
  title = {Reciprocal Nutritional Benefits in a {Mediterranean}
    Seagrass-Sponge Association},
  date = {2026-07-17},
  url = {https://www.luismmontilla.com/papers/cardini2026/},
  doi = {https://doi.org/10.7717/peerj.21392},
  langid = {en},
  abstract = {Sponges commonly form associations within seagrass
    meadows, but their potential impact on seagrass productivity and
    nutrient cycles remains poorly understood. This study investigates
    the association between the demosponge \_Chondrilla nucula\_ and the
    Mediterranean seagrass \_Posidonia oceanica\_ in two sampling
    occasions during the plant growth (spring) and senescence (autumn)
    seasons at a small inlet near Naples, Italy, where the sponge grows
    conspicuously within the seagrass bed. We found a non-linear
    relationship between the benthic cover of the sponge and the
    seagrass, with higher \_C. nucula\_ cover linked to intermediate
    \_P. oceanica\_ cover, suggesting spatial dependence. \_Posidonia
    oceanica\_ showed higher net primary production (NPP) in spring,
    while \_C. nucula\_ was net heterotrophic in spring but exhibited
    near zero metabolic balance in autumn. NPP remained stable when the
    two organisms were associated, regardless of the season.
    \_Chondrilla nucula\_ consistently contributed inorganic nutrients
    to the association in the form of phosphate, ammonium, and
    substantial nitrate, recycling nutrients that potentially benefited
    \_P. oceanica\_ in its growth season. In return, the seagrass
    released dissolved organic carbon in spring , which is consistent
    with supporting sponge heterotrophic nutrition. These findings
    suggest reciprocal benefits in the interaction between \_C. nucula\_
    and \_P. oceanica\_, with nutrient exchange facilitating a
    facultative mutualism that potentially supports and stabilizes the
    productivity of the seagrass ecosystem.}
}

For attribution, please cite this work as:

Cardini, U., L. M. Montilla, G. Zapata-Hernández, et al. 2026. “Reciprocal Nutritional Benefits in a Mediterranean Seagrass-Sponge Association.” PeerJ, July 17. https://doi.org/https://doi.org/10.7717/peerj.21392.