Modelling mangrove productivity and food web trophic interactions using stable isotopes of carbon and nitrogen in Rabigh Lagoon, Saudi Arabia

Mangrove habitats have garnered considerable interest and attention because of their distinctiveness, the ecological services they offer, and their effects on humans and biodiversity. This work used stable carbon and nitrogen isotopes to assess the trophic relationships and mangrove productivity in Rabigh Lagoon, Saudi Arabia. In Rabigh Lagoon, species samples classified as producers and consumers were gathered from mangrove ecosystems. δ 13 C × Nutrients and Salts/Salinity × Nutrients models were used to determine the productivity of mangrove. δ 13 C and δ 15 N stable isotopes of the producers and consumers were determined using Thermo elementary analyser–ConFlo IV–Delta V Advantage mass spectrometer. One-way analysis of variance was used to determine the significant variation in δ 13 C and δ 15 N across organisms in different trophic levels. There is significant variation in the six mangrove stands surveyed in Rabigh lagoon, with the highest productivity recorded at site 5 (S5) (fδ 13 C.fN: 1.78) and site 2 (S2) (fδ 13 C.fP: 2.81) base on isotopic productivity model, while for salinity productivity model, the productivity was highest at site 5 (S5) and site 3 (S3) (fSalinity.fN: 5.09 – 6.48). The differences in δ 13 C and salinity form the basis for dissimilarity in results generated from the two models. The modelled productivity was positively correlated with Avicennia marina, Enteromorpha clathrata , and Halophila species, Phorbas species, Portunus pelagicus , Negombata magnifica , Callyspongia species, Amphimedon chloros and Echinophyllia aspera on a total variation of 98.9 %. This study provides baseline information on the productivity of Rabigh lagoon mangroves and its relationship with the organisms at the different trophic levels.