Diversity and Ecological Characterization of Sporulating Higher Filamentous Marine Fungi Associated with Spartina maritima (Curtis) Fernald in Two Portuguese Salt Marshes

Succession of Fungal Communities and Their Functional Profiles in a Decaying Foundation Species

Dead plant biomass from foundation plant species is fundamental for the survival of coastal salt marshes because dead biomass aids in the vertical accretion of the ecosystem. Fungi regulate the decomposition of dead biomass, and thus play an essential role for marsh survival. Despite their importance, little is known about the compositional and functional changes of fungal communities in plant matter throughout senescence and litter decomposition. Here, we analyzed how fungal communities and their functionality change in the foundation plant species Spartina patens, which builds vast amounts of dead plant biomass (thatch) on the soil surface. We analyzed the chemical and fungal properties of live biomass, standing dead biomass (dead biomass shortly after senescence), upper thatch (top layer of litter on the soil surface), and lower thatch (bottom layer of litter on the soil surface) during September and November of 2021. We found that the chemical and fungal properties of different S. patens biomass types followed a predictable litter decomposition pattern. Notably, live biomass, standing dead biomass, upper thatch, and lower thatch all hosted unique fungal communities and litter chemistry. Functional groups present in live biomass (pathogens, epiphytes, and mycoparasites) were lost during senescence and later replaced by diverse saprotrophs. The abundance of lignocellulose saprotrophs increased throughout decomposition, with the highest abundance occurring in lower thatch. These results suggest a predictable succession of fungal communities through the senescence and decomposition of the foundation species S. patens. Our study highlights the diversity of fungal communities in a disappearing foundation species.

Fungal Biodiversity in Salt Marsh Ecosystems

This review brings together the research efforts on salt marsh fungi, including their geographical distribution and host association. A total of 486 taxa associated with different hosts in salt marsh ecosystems are listed in this review. The taxa belong to three phyla wherein Ascomycota dominates the taxa from salt marsh ecosystems accounting for 95.27% (463 taxa). The Basidiomycota and Mucoromycota constitute 19 taxa and four taxa, respectively. Dothideomycetes has the highest number of taxa, which comprises 47.12% (229 taxa), followed by Sordariomycetes with 167 taxa (34.36%). Pleosporales is the largest order with 178 taxa recorded. Twenty-seven genera under 11 families of halophytes were reviewed for its fungal associates. Juncus roemerianus has been extensively studied for its associates with 162 documented taxa followed by Phragmites australis (137 taxa) and Spartina alterniflora (79 taxa). The highest number of salt marsh fungi have been recorded from Atlantic Ocean countries wherein the USA had the highest number of species recorded (232 taxa) followed by the UK (101 taxa), the Netherlands (74 taxa), and Argentina (51 taxa). China had the highest number of salt marsh fungi in the Pacific Ocean with 165 taxa reported, while in the Indian Ocean, India reported the highest taxa (16 taxa). Many salt marsh areas remain unexplored, especially those habitats in the Indian and Pacific Oceans areas that are hotspots of biodiversity and novel fungal taxa based on the exploration of various habitats.

Phylogenetic assessment and taxonomic revision of Halobyssothecium and Lentithecium (Lentitheciaceae, Pleosporales)

Our studies on lignicolous aquatic fungi in Thailand, Sweden, and the UK resulted in the collection of three new Halobyssothecium species (H. bambusicola, H. phragmitis, H. versicolor) assigned to Lentitheciaceae (Pleosporales, Dothideomycetes). Multi-loci phylogenetic analyses of the combined large subunit, small subunit, internal transcribed spacers of ribosomal DNA, and the translation elongation factor 1-alpha sequence data enabled a revision of the taxa assigned to Lentithecium and the transfer of L. cangshanense, L. carbonneanum, L. kunmingense, L. unicellulare, and L. voraginesporum to Halobyssothecium. Collection of an asexual morph of L. lineare and phylogenetic analysis confirmed its taxonomic placement in Keissleriella. Detailed descriptions and illustrations of H. bambusicola, H. phragmitis, and H. versicolor are provided.

Diversity of fungi associated with macroalgae from an estuarine environment and description of Cladosporium rubrum sp. nov. and Hypoxylon aveirense sp. nov

Fungal communities associated with macroalgae remain largely unexplored. To characterize algicolous fungal communities using culture dependent methods, macroalgae were collected from different sampling sites in the Ria de Aveiro estuary, Portugal. From a collection of 486 isolates that were obtained, 213 representative isolates were selected through microsatellite-primed PCR (MSP-PCR) fingerprinting analysis. The collection yielded 33 different genera, which were identified using the ITS region of the rDNA. The results revealed that the most abundant taxa in all collections were Acremonium-like species: Alternaria, Cladosporium, Leptobacillium and Penicillium. The fungal community composition varied with macroalgae species. Through multilocus phylogenetic analyses based on ITS, tub2, tef1-α and actA sequences, in addition to detailed morphological data, we propose Cladosporium rubrum sp. nov. (type strain=CMG 28=MUM 19.39) and Hypoxylon aveirense sp. nov. (type strain=CMG 29=MUM 19.40) as novel species.

Revealing the hidden diversity of marine fungi in Portugal with the description of two novel species, Neoascochyta fuci sp. nov. and Paraconiothyrium salinum sp. nov

Fungi are ubiquitous organisms with a wide distribution in almost all ecosystems, including marine environments. Coastal and estuarine ecosystems remain poorly unexplored as fungal habitats, potentially harbouring a hidden diversity with important ecological roles. During an extensive survey of marine fungi in coastal and estuarine Portuguese environments, a collection of 612 isolates was obtained from water, algae, sponges and driftwood. From these, 282 representative isolates were selected through microsatellite-primed PCR (MSP-PCR) fingerprinting analysis, which were identified based on DNA sequence data. The collection yielded 117 taxa from 38 distinct genera, which were identified using DNA sequence analysis. Overall, fungal community composition varied with host/substrate, but the most abundant taxa in the collection were Cladosporium cladosporioides, Penicillium terrigenum, Penicillium brevicompactum and Fusarium equiseti/incarnatum complex. The occurrence of a high fungal diversity harbouring novel species was disclosed. Through a multilocus phylogeny based on ITS, tub2 and tef1-α sequences, in conjunction with morphological and physiological data, we propose Neoascochyta fuci sp. nov. and Paraconiothyrium salinum sp. nov.

From physiology to salt marsh management challenges with sea level rise: the case of native Spartina foliosa, invasive S. densiflora and their hybrid

Sea level rise (SLR) imposes increasing salinity and inundation stresses in salt marshes which simultaneously face invasions by exotic plant species. We aimed to improve and apply knowledge on the ecophysiological responses of halophytes to SLR to conservation management of salt marshes. In a mesocosm experiment, we measured and compared phosphoenolpyruvate carboxylase (PEPC) activity and related functional traits of the California-native Spartina foliosa, invasive S. densiflora and their hybrid S. densiflora × foliosa in response to increasing levels of salinity and inundation. S. foliosa was moderately sensitive to salinity, showing a 57% reduction in PEPC specific activity from freshwater to hypersalinity. This native species compensated for the reduction of PEPC activity with increased salinity through 80% higher enzyme activation by phosphorylation. PEPC functional trait responses of S. foliosa were mostly independent of inundation depth. In view of these results, managers should conserve undeveloped lands for accommodation space above current high tide lines to facilitate colonization of stress-tolerant S. foliosa. Our results on functional responses of PEPC traits recorded high sensitivity to salinity for S. densiflora. This was reflected by 65% lower PEPC specific activity together with increasing accumulation of free proline (+96%) and total proteins (+23%) with elevated salinity. These results suggest prioritized eradication of S. densiflora populations in brackish habitats. Measured PEPC responses support the high stress tolerance of the S. densiflora × foliosa hybrid. PEPC traits for the hybrid were mostly independent of salinity and inundation. The hybrid showed higher PEPC-specific activity than S. foliosa (+70%) and S. densiflora (+15%) in freshwater under intermediate inundation. Results suggest that eradication of the hybrid should be the highest management priority. Our study shows that the responses of key functional physiological traits to environmental stresses serve as biological indicators that can guide ecosystem management practices in a scenario of climate change.

Marine fungi of the Baltic Sea

Vast parts of the Baltic Sea have been mycologically neglected and are still awaiting exploration. Here we summarise earlier records of marine fungi from the Baltic, supplementing them with discoveries from fieldwork in Sweden in 2019. Although marine fungal diversity is clearly attenuated in the brackish water of the Baltic Sea, a substantial number has still been discovered. Here we list 77 species from the Baltic Sea, whereas after a critical assessment a further 18 species have been excluded as records of marine fungi. The species have mainly been identified by their morphological features, supplemented by DNA-based diagnostics. Most of the species have their main distributions in temperate areas of the Atlantic Ocean. Some of the Baltic species discovered here represent far disjunctions to tropical waters while only a very few are until now only recorded for the Baltic Sea. In this paper two species belong in Basidiomycota, while the most ascomyceteous speciose classes are Sordariomycetes (with 42 species) and Dothideomycetes (24). Halosphaeriaceae is the most speciose family in marine habitats, as also in the Baltic Sea, represented here by 29 species. Three species are new to Europe, and in addition 13 to the Baltic Sea and 13 to Sweden.

Vascular Plants Are Globally Significant Contributors to Marine Carbon Fluxes and Sinks

More than two-thirds of global biomass consists of vascular plants. A portion of the detritus they generate is carried into the oceans from land and highly productive blue carbon ecosystems-salt marshes, mangrove forests, and seagrass meadows. This large detrital input receives scant attention in current models of the global carbon cycle, though for blue carbon ecosystems, increasingly well-constrained estimates of biomass, productivity, and carbon fluxes, reviewed in this article, are now available. We show that the fate of this detritus differs markedly from that of strictly marine origin, because the former contains lignocellulose-an energy-rich polymer complex of cellulose, hemicelluloses, and lignin that is resistant to enzymatic breakdown. This complex can be depolymerized for nutritional purposes by specialized marine prokaryotes, fungi, protists, and invertebrates using enzymes such as glycoside hydrolases and lytic polysaccharide monooxygenases to release sugar monomers. The lignin component, however, is less readily depolymerized, and detritus therefore becomes lignin enriched, particularly in anoxic sediments, and forms a major carbon sink in blue carbon ecosystems. Eventual lignin breakdown releases a wide variety of small molecules that may contribute significantly to the oceanic pool of recalcitrant dissolved organic carbon. Marine carbon fluxes and sinks dependent on lignocellulosic detritus are important ecosystem services that are vulnerable to human interventions. These services must be considered when protecting blue carbon ecosystems and planning initiatives aimed at mitigating anthropogenic carbon emissions.

Molecular data reveals a new holomorphic marine fungus, Halobyssothecium estuariae, and the asexual morph of Keissleriella phragmiticola

This study introduces a novel holomorphic marine fungal species, Halobyssothecium estuariae (Lentitheciaceae, Pleosporales), from dead Phragmites communis. The new species has semi-immersed, subglobose or ellipsoidal, papillate, conical ascomata, clavate to subcylindrical, short pedicellate asci and 3-septate, fusoid to ellipsoidal ascospores with rounded ends, pale brown to dark brown central cells and hyaline end cells. The asexual morph has multiseptate, filiform, intercalary, catenate, branched chlamydospores that resemble Xylomyces. The asexual morph of Keissleriella phragmiticola based on combined LSU, SSU, ITS and TEF1 sequence analyses is reported. The role of molecular identification in delineating cryptic species are also discussed.

Potential roles of marine fungi in the decomposition process of standing stems and leaves of Spartina maritima

Fungal communities inhabiting live, senescent, and decaying leaf sheaths, stems, and leaf blades of standing plants of Spartina maritima in two Portuguese salt marshes were assessed by morphological identification of fruiting structures and sequence-based identification based on polymerase chain reaction (PCR)-cloning analysis of the internal transcribed spacer (ITS) rDNA. The molecular method enabled identification of infrequent ascomycetes and basidiomycetes (filamentous and yeasts) and the asexual morph of Byssothecium obiones and Phaeosphaeria halima. The occurrence and ecological role of the most frequent fungi on different S. maritima substrates seem to depend on the phase of plant life cycle, and specifically on the availability and microenvironmental conditions of each plant substrate. Specifically, By. obiones, Natantispora retorquens, and Lulworthia sp. 1 were involved in the decay of lower-middle culms, Buergenerula spartinae of middle culms and leaves, P. halima, Phaeosphaeria spartinicola, and Stagonospora sp. 1 of middle-upper leaves, and Mycosphaerella sp. I of upper leaves of early-decaying S. maritima plants. The presence of these fungi on live vegetative structures suggests that they might begin the colonization process as endophytes, gaining a competitive advantage over the other saprobic fungi on the plants.