- Overview of the study: “The objective of this study was to assess the relative importance of mangrove and seagrass food sources in fish diets, taking into consideration several types of mangrove habitats in the western Atlantic region”(82).
- The results from this study show that seagrass beds play a larger role in sources of food for a majority of fish rather than mangrove habitat based on carbon content of primary producers and animal prey: “In all study sites, mangrove prey items were more 13C depleted than those from seagrass beds (t-tests, Pb0.001, Figs. 2a, 3a, 4a). In each study site, primary producers showed distinct carbon signatures, with lower values observed for mangrove litter (−28.9‰ to −27.1‰) and higher values for green seagrass leaves (−14.6‰ to −7.0‰) (t-tests, Pb0.001, Figs. 2a, 3a, 4a). In Belize, an increasing δ 13C gradient was observed between primary producers from fringing mangroves bordering the overwash islet (Be-MO: −28.9‰ to −16.5‰), seagrass beds adjacent to mangroves (Be-SG: −16.0‰ to −13.0‰, t‐tests, Pb0.001) and seagrass beds far from mangroves (Be-SGF: −8.9‰ to −7.0‰, t‐tests, Pb0.001) (Fig. 4a)…Even with some similar carbon signatures between mangrove and seagrass motile prey items (i.e., Majidae crabs from IRL-SG and Mysidacea from Be-MO), invertebrates from mangroves had in general more depleted δ 13C values compared to those from seagrass beds (t-tests, Pb0.001, Figs. 2a, 3a, 4a)”(86,87).
- This study emphasizes the importance of mangrove habitat for juvenile fish habitat rather than feeding grounds” “This study showed that most transient fishes (22 out of 31 species) from subtropical (IRL-MB, Keys-MF) and tropical mangroves (Be-MO) actively foraged in nearby seagrass beds, thus reinforcing the limited role of mangroves as fish foraging habitats for these species…It has been shown that structural complexity of mangrove prop roots attract juvenile reef fishes, which use this habitat more as shelters and nursery grounds than as foraging areas (Laegdsgaard and Johnson, 2001; Nagelkerken et al., 2010).”(91).
- In conclusion: “this study emphasizes the importance of considering different mangrove habitat types when investigating fish foraging grounds. SIA facilitated tracing of mangrove and seagrass food-source contributions in fish diets and revealed that 8 out of 10 resident and only 4 out of 31 transient species from basin, ponds, fringing and overwash mangrove sites derived a substantial proportion of their diets from mangroves. In Florida and Belize, these species were large roving fishes, zoobenthic or water column feeders that depend indirectly on organic matter from mangroves through the benthic–pelagic food web or secondary consumers. The remaining fish species, including juvenile reef fishes, occur in mangroves but appear to forage in adjacent seagrass habitats”(91).
- This article may be important to show the importance of both seagrass beds and mangrove habitat to fish species because of the connected role of the two ecosystems. If seagrass habitat is being destroyed, there may not be enough food in mangrove habitat to support a healthy ecosystem. Likewise, destruction of mangrove habitat may lead to the depletion of a species due to a lack of habitat for juveniles.