Food web structure and isotopic niche in a fringe macro-tidal mangrove system, Tropical Eastern Pacific

Tropical mangroves are amongst the most productive and dynamic ecosystems on Earth. In order to understand the trophic dynamics of estuarine mangrove fringes in the Tropical Eastern Pacific, stable isotope data (δ¹³C/δ¹⁵N) of primary producers and consumers (macroinvertebrates) were analyzed using Bayesian mixing models (MixSIAR/SIBER). The mangrove food web exhibited four trophic levels, a wide consumer δ¹³C range (~ 10‰), consumer dependence on different carbon sources (mangroves-detritus, microphytobenthos, macroalgae, planktonic sources), and a wide consumer isotopic niche with little overlap. According to MixSiar analyses, microphytobenthos was an important resource for deposit feeders (60%), filter feeders (65%), filter feeder bivalves (76%), and carnivores (49%). This suggests that microphytobentos provide significant support to the mangrove macroinvertebrate community. Additionally, mangrove-derived carbon played a major role in sustaining herbivores (44%), while macroalgae partially sustained omnivores (33%) and carnivores (45%). Finally, planktonic sources were found to partially support omnivores (33%). Our results reinforce the hypothesis that a diversity of trophic pathways support estuarine mangrove communities, albeit with microphytobenthos being the main carbon source. These findings underline the complexity of the trophic dynamics of estuarine mangrove—food webs in one of the most biodiverse areas of the world.