Global diversity and biogeography of the Zostera marina mycobiome

Seagrasses are marine flowering plants that provide critical ecosystem services in coastal environments worldwide. Marine fungi are often overlooked in microbiome and seagrass studies, despite terrestrial fungi having critical functional roles as decomposers, pathogens or endophytes in global ecosystems. Here we characterize the distribution of fungi associated with the seagrass, Zostera marina, using leaves, roots, and rhizosphere sediment from 16 locations across its full biogeographic range. Using high throughput sequencing of the ribosomal internal transcribed spacer (ITS) region and 18S ribosomal RNA gene, we first measured fungal community composition and diversity. We then tested hypotheses of neutral community assembly theory and the degree to which deviations suggested amplicon sequence variants (ASVs) were plant-selected or dispersal-limited. Finally, we identified a core mycobiome and investigated the global distribution of differentially abundant ASVs. We found that the fungal community is significantly different between sites and that the leaf mycobiome follows a weak, but significant pattern of distance decay in the Pacific Ocean. Generally, there was evidence for both deterministic and stochastic factors contributing to community assembly of the mycobiome, with most taxa assembling through stochastic processes. The Z. marina core leaf and root mycobiomes were dominated by unclassified Sordariomycetes spp., unclassified Chytridiomycota lineages (including Lobulomycetaceae spp.), unclassified Capnodiales spp. and Saccharomyces sp. It is clear from the many unclassified fungal ASVs and fungal functional guilds, that knowledge of marine fungi is still rudimentary. Further studies characterizing seagrass-associated fungi are needed to understand the roles of these microorganisms generally and when associated with seagrasses. Importance Fungi have important functional roles when associated with land plants, yet very little is known about the roles of fungi associated with marine plants, like seagrasses. In this study, we report the results of a global effort to characterize the fungi associated with the seagrass, Zostera marina, across its full biogeographic range. Although we defined a putative global core fungal community, it is apparent from the many fungal sequences and predicted functional guilds that had no matches to existing databases, that general knowledge of seagrass-associated fungi and marine fungi generally is lacking. This work serves as an important foundational step towards future work investigating the functional ramifications of fungi in the marine ecosystem.

Fish Response to Multiple Anthropogenic Stressors in Mediterranean Coastal Lagoons: A Comparative Study of the Role of Different Management Strategies

Transitional waters are among the most productive ecosystems of the world and their biotic communities show high diversity and complex mechanisms of self-regulation that provide valuable ecosystem services and societal goods and benefits. In this work a comparison of the fish assemblages of three non-tidal Mediterranean coastal lagoons is carried out in order to evaluate the impacts of alternative management strategies. The anthropogenic pressures acting on the lagoons were quantified by means of categorical indicators, while the characteristics of the fish assemblages were summarized in multi-metric indices (MMIs). Two MMIs were developed using data collected with a beach seine net and with fyke nets, following an empirical approach that selects, from a pool of 73 metrics, the combination that maximizes the MMI/pressure relationship. The two MMIs include four metrics each, most of which are based on feeding mode functional guilds and habitat use functional guilds, and they are sensitive to anthropogenic pressures. The human activities directly or indirectly affecting water quality are the ones that most influence the fish assemblage, while the presence of artisanal fisheries, a typical and relevant resource use in these lagoons, seems to play a beneficial role. Lagoon fisheries management relies on the maintenance of infrastructures that guarantee the hydraulic functioning of the lagoon, thus ensuring exchanges with the adjacent coastal sea, and therefore indirectly contributing to the habitat quality.

Winter bird abundance, species richness and functional guild composition at Delhi’s ponds: does time of day and wetland extent matter?

Urbanisation can limit species persistence and bias composition of functional guilds with serious consequences for ecosystem functioning and conservation planning. Standardised biodiversity surveys are missing at most tropical urban cities where biodiversity levels are high alongside rapidly increasing rates of urbanisation. We explored the utility of time-bound surveys to document winter birds at ponds (wetlands ≤ 5 ha) in Delhi, India at two different times of the day (morning and evening) and in areas with varying extents of wetlands. Systematic surveys at 39 ponds during January–March 2020 yielded an estimated 173 ± 22 bird species (∼37% of Delhi’s birds). The total bird species assemblage at ponds did not vary significantly with time of day, but β-diversity increased marginally with increasing extent of wetlands. Total bird abundance and species richness varied substantially with time of day, with differences apparent across several species rich functional feeding and habitat guilds. Abundance and species richness of some guilds, including species-poor guilds, varied in ponds located in areas with differing extent of wetlands. Reliable and comparable measures of species abundance and species richness (both total and across functional guilds)— metrics commonly used to set research and conservation priorities—in urban habitats can be obtained after appropriately standardising field effort. Such standardised efforts can help underscore the importance of maintaining and improving erstwhile-ignored habitats such as unprotected ponds that are providing refugia to hundreds of bird species in mega-cities like Delhi.