Influence of nutrient enrichment on colonisation and photosynthetic parameters of hard substrate marine microphytobenthos

Abstract

This study aimed to assess the influence of nutrient enrichment on the development of microalgal biofilm on concrete and PVC cubes. Three mesocosms were utilized to create a nutrient gradient over a period of 28 days. Various parameters including biomass, photosynthetic activity, microtopography, and extracellular polymeric substances (EPS) were measured. Imaging PAM techniques were employed to obtain surface-wide data. Results revealed that nutrient availability had no significant impact on Chl a biomass and the maximum quantum efficiency of PSII ($F_v$/$F_m$). The photosynthetic capacity and efficiency were minimally affected by nutrient availability. Interestingly, the relationship between microphytobenthic (MPB) biomass and photosynthesis and surface rugosity exhibited distinct patterns. Negative reliefs showed a strong correlation with $F_v$/$F_m,$ while no clear pattern emerged for biomass on rough concrete structures. Overall, our findings demonstrate that under conditions of heightened eutrophication, biofilm photosynthesis thrives in the fissures and crevasses of colonized structures regardless of nutrient levels. This investigation provides valuable insights into the interplay between nutrient availability and surface rugosity.

Keywords:

• Microphytobenthos
• marine infrastructures
• photosynthesis
• eutrophication
• pulse amplitude modulated (PAM) fluorimetry
• extracellular polymeric substances (EPS)

Acknowledgments

The results presented in this article were obtained in the collaborative project Interreg Va MARINEFF, selected under the European Cross-border Programme INTERREG FMA, and co-funded by the ERDF. The authors wish to thank the co-financiers and all project partners for their support. The authors also acknowledge the Normandy Region for funding the IMAGING-PAM (CPER Manche 2021). The authors are grateful to Richard Retoux and Xavier Larose of the CRISMAT laboratory (Normandie Univ, ENSICAEN, UNICAEN, CNRS, CRISMAT, 14000 Caen, France) for technical SEM support. The authors thank Antoine Grémare, Alicia Romero Ramirez and Anaïs Richard of the University of Bordeaux for the loan of the 3D camera.

Disclosure statement

The authors have no financial or proprietary interests in any material discussed in this article.

Data availability statement

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

Additional information

Funding

The results presented in this article were obtained in the collaborative project Interreg Va MARINEFF, selected under the European Cross-border Programme INTERREG FMA, and co-funded by the ERDF. The authors wish to thank the co-financiers and all project partners for their support. The authors also acknowledge the Normandy Region for funding the IMAGING-PAM (CPER Manche 2021).