Mangroves consist of some of the most unique ecosystems on Earth. They are made up of trees and shrubs tolerant to high levels of salinity (halophytes), as they are adapted to a coastal marine life. Complexes within these plants filtrate the salt out of the water, allowing this mangrove forest biomes to exist from slightly brackish water, to places with salt concentrations double to that found in our oceans. These remarkable places fostered evolutionary adaptions that allowed plants to function here, but mycologist researching these biomes realized that without a bizarre group of diverse fungi living amongst these mangroves, the plants living here would have an increasingly tough time making ends meet. Together these functional assemblages of fungi which include saprobes, parasites, mutualists and other endophytes help maintain nearly 130,000 square kilometers of mangrove forests around the world.
Global mangrove distribution.
Manglicolous fungi consist of both marine and terrestrial organisms. Marine fungi live in the submerged clayey soil, roots, and stems, while terrestrial fungi inhabit the stems, branches and upper root surfaces above the water’s surface. There is such a wide array of fungi living in these ecosystems because mangroves provide a bounty of microhabitats, and because this ecosystem type is detritus-based. Fallen leaves, twigs and branches feed a large fungal community that make these nutrient pools accessible to the plants again. In mangrove forests, saprotrophs are vital to the energy flow within these systems.
Compared to the rich diversity of saprobic manglicolous fungi described, only a handful of parasitic fungi has been found that are associated with this ecosystem type. A mere grand total of 26 parasitic manglicolous fungi have been scientifically described. This ecological role seems like it is the weakest driver of functionality amongst the mangroves, but even still, these fungi help create detritus, and also help select traits in plants that resist pathogens. Parasitic manglicolous fungi enhance these communities, making them more ecologically resistant and resilient.
Most mangrove plants form mycorrhizal mutualisms in the form of AMF. These fungi are key in these habitats, because if nutrients are not quickly assimilated to the plants living here, those resources are quickly washed away by intertidal activity. Not much research has been carried out to study the fungal mutualists in these mangroves, since most work focuses on the saprobic manglicolous fungi. Still, scientists Kumar and Ghose in 2008 examined the largest mangrove in the world, apart of the Sundarbans on the Ganges Delta. They found 15 mangrove associated plants with an obligate relationship to mycorrhizae. This same study recorded 44 different species of fungi symbiotically living within mangrove plant tissues.
The largest mangrove forest in the world- the Sundarbans
Mangroves also support a diverse community of fungal endophytes, that live in the tissues of mangrove associated plants, without any negative effects of its host. Many of these species of latent fungi remain dormant in plant tissues, waiting for the plant to die, or the branches they inhabit to break or senesce. These fungi already within the plant have a competitive edge over other saprotrophs, because they essentially colonize the organic matter, prior to it becoming available.
Before I compiled this information you just read, I didn’t know much about mangroves, and I knew nearly nothing about manglicolous fungi. I learned that these are ecologically important treasure troves that need to be protected on Earth. Mangroves support a massive assortment of biological life, both marine and terrestrial. We are just fully understanding their ecological importance as well as their pharmaceutical potential. Manglicolous fungi release a variety of extracellular degradative enzymes to breakdown miscellaneous plant material, in several microhabitats within the same biome. Today, researchers are mining these chemical exudates so that one day, these fungi may provide humanity with novel metabolites to help fight against cancer, viruses, and malicious bacterial infections. The forest floor never ceases to amaze me, even when is totally submerged under brackish water.