Marine Phytophthora species can hamper conservation and restoration of vegetated coastal ecosystems

Phytophthora species are potent pathogens that can devastate terrestrial plants, causing billions of dollars of damage yearly to agricultural crops and harming fragile ecosystems worldwide. Yet, virtually nothing is known about the distribution and pathogenicity of their marine relatives. This is surprising, as marine plants form vital habitats in coastal zones worldwide (i.e. mangrove forests, salt marshes, seagrass beds), and disease may be an important bottleneck for the conservation and restoration of these rapidly declining ecosystems. We are the first to report on widespread infection of Phytophthora and Halophytophthora species on a common seagrass species, Zostera marina (eelgrass), across the northern Atlantic and Mediterranean. In addition, we tested the effects of Halophytophthora sp. Zostera and Phytophthora gemini on Z. marina seed germination in a full-factorial laboratory experiment under various environmental conditions. Results suggest that Phytophthora species are widespread as we found these oomycetes in eelgrass beds in six countries across the North Atlantic and Mediterranean. Infection by Halophytophthora sp. Zostera, P. gemini, or both, strongly affected sexual reproduction by reducing seed germination sixfold. Our findings have important implications for seagrass ecology, because these putative pathogens probably negatively affect ecosystem functioning, as well as current restoration and conservation efforts

Evidence for 'critical slowing down' in seagrass:a stress gradient experiment at the southern limit of its range

The theory of critical slowing down, i.e. the increasing recovery times of complex systems close to tipping points, has been proposed as an early warning signal for collapse. Empirical evidence for the reality of such warning signals is still rare in ecology. We studied this on Zostera noltii intertidal seagrass meadows at their southern range limit, the Banc d'Arguin, Mauritania. We analyse the environmental covariates of recovery rates using structural equation modelling (SEM), based on an experiment in which we assessed whether recovery after disturbances (i.e. seagrass & infauna removal) depends on stress intensity (increasing with elevation) and disturbance patch size (1 m(2) vs. 9 m(2)). The SEM analyses revealed that higher biofilm density and sediment accretion best explained seagrass recovery rates. Experimental disturbances were followed by slow rates of recovery, regrowth occurring mainly in the coolest months of the year. Macrofauna recolonisation lagged behind seagrass recovery. Overall, the recovery rate was six times slower in the high intertidal zone than in the low zone. The large disturbances in the low zone recovered faster than the small ones in the high zone. This provides empirical evidence for critical slowing down with increasing desiccation stress in an intertidal seagrass system

Replication Data for: Conservation implications of Sabellaria spinulosa reef patches in a dynamic sandy-bottom environment

This dataset consists of three folders: Bathymetry_Data (split up into two zip files per campaign year, due to large file sizes) Endobenthos_Data Epifauna_Data Raw video footage is added as separate files per transect, per campaign year. Note that some video files are currently not available due to upload file size limitation; these can be requested by contacting the first author

Replication Data for: Conservation implications of Sabellaria spinulosa reef patches in a dynamic sandy-bottom environment

This dataset consists of three folders: Bathymetry_Data (split up into two zip files per campaign year, due to large file sizes) Endobenthos_Data Epifauna_Data Raw video footage is added as separate files per transect, per campaign year. Note that some video files are currently not available due to upload file size limitation; these can be requested by contacting the first author

Developing seed- and shoot-based restoration approaches for the seagrass, Zostera muelleri

The restoration of seagrass habitats is a relatively young field with several successful restoration attempts highlighting the feasibility of large-scale restoration. Successful restoration of seagrass habitats requires an understanding of the most appropriate techniques to use for the target species and local conditions of restoration sites, however, there are currently limited studies on Zostera muelleri. Here, we conduct field trials to explore the use of seed- and shoot-based restoration approaches for Z. muelleri in Victoria, Australia. We assessed the feasibility of collecting and germinating seeds in the field for restoration purposes and trialed the success of four shoot-based transplanting techniques. We found that seed collections for Z. muelleri were highly successful and scalable, with seed collection rates improving from 489 to 1,939 seeds/hour over 2 years. In addition, in situ seedling germination increased from a maximum of 10.80–25.25% over 2 years. In contrast, shoot-based restoration approaches were more variable, with plants transplanted with their sediment-intact outperforming all bare-rooted approaches. Shoot-based transplanting approaches appear to have more limited application, but may be appropriate for some restoration sites, or used in combination with seeds to achieve the best restoration outcome. Seed-based approaches have the potential to be viable and scalable for Z. muelleri given that large numbers of seeds can be collected and stored for at least 7 months before successfully germinating in the field. However, further studies are required to overcome the seedling survival bottleneck (approximately 4 months from emergence) and further increase in situ germination rates

Developing seed- and shoot-based restoration approaches for the seagrass, Zostera muelleri

The restoration of seagrass habitats is a relatively young field with several successful restoration attempts highlighting the feasibility of large-scale restoration. Successful restoration of seagrass habitats requires an understanding of the most appropriate techniques to use for the target species and local conditions of restoration sites, however, there are currently limited studies on Zostera muelleri. Here, we conduct field trials to explore the use of seed- and shoot-based restoration approaches for Z. muelleri in Victoria, Australia. We assessed the feasibility of collecting and germinating seeds in the field for restoration purposes and trialed the success of four shoot-based transplanting techniques. We found that seed collections for Z. muelleri were highly successful and scalable, with seed collection rates improving from 489 to 1,939 seeds/hour over 2 years. In addition, in situ seedling germination increased from a maximum of 10.80–25.25% over 2 years. In contrast, shoot-based restoration approaches were more variable, with plants transplanted with their sediment-intact outperforming all bare-rooted approaches. Shoot-based transplanting approaches appear to have more limited application, but may be appropriate for some restoration sites, or used in combination with seeds to achieve the best restoration outcome. Seed-based approaches have the potential to be viable and scalable for Z. muelleri given that large numbers of seeds can be collected and stored for at least 7 months before successfully germinating in the field. However, further studies are required to overcome the seedling survival bottleneck (approximately 4 months from emergence) and further increase in situ germination rates