Browsing by Author "van Tussenbroek, Brigitta I."
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- Diversity of the holopelagic Sargassum microbiome from the Great Atlantic Sargassum Belt to coastal stranding locationsPublication . Theirlynck, Tom; Mendonça, Inara Regina W.; Engelen, Aschwin; Bolhuis, Henk; Collado-Vides, Ligia; van Tussenbroek, Brigitta I.; García-Sánchez, Marta; Zettler, Erik; Muyzer, Gerard; Amaral-Zettler, LindaThe holopelagic brown macroalgae Sargassum natans and Sargassum fluitans form essential habitats for attached and mobile fauna which contributes to a unique biodiversity in the Atlantic Ocean. However, holopelagic Sargassum natans (genotype I & VIII) and Sargassum fluitans (genotype III) have begun forming large accumu-lations with subsequent strandings on the western coast of Africa, the Caribbean and northern Brazil, threatening local biodiversity of coastal ecosystems and triggering economic losses. Moreover, stranded masses of hol-opelagic Sargassum may introduce or facilitate growth of bacteria that are not normally abundant in coastal regions where Sargassum is washing ashore. Hitherto, it is not clear how the holopelagic Sargassum microbiome varies across its growing biogeographic range and what factors drive the microbial composition. We determined the microbiome associated with holopelagic Sargassum from the Great Atlantic Sargassum Belt to coastal stranding sites in Mexico and Florida. We characterized the Sargassum microbiome via amplicon sequencing of the 16S V4 region hypervariable region of the rRNA gene. The microbial community of holopelagic Sargassum was mainly composed of photo(hetero)trophs, organic matter degraders and potentially pathogenic bacteria from the Pseudomonadaceae, Rhodobacteraceae and Vibrionaceae. Sargassum genotypes S. natans I, S. natans VIII and S. fluitans III contained similar microbial families, but relative abundances and diversity varied. LEfSE analyses further indicated biomarker genera that were indicative of Sargassum S. natans I/VIII and S. fluitans III. The holopelagic Sargassum microbiome showed biogeographic patterning with high relative abundances of Vibrio spp., but additional work is required to determine whether that represents health risks in coastal environments. Our study informs coastal management policy, where the adverse sanitary effects of stranded Sargassum might impact the health of coastal ecosystems.
- Effects of nutrient enrichment on seagrass population dynamics: evidence and synthesis from the biomass-density relationshipsPublication . Cabaco, Susana; Apostolaki, Eugenia T.; Garcia-Marin, Patricia; Gruber, Renee; Hernandez, Ignacio; Martinez-Crego, Begona; Mascaro, Oriol; Perez, Marta; Prathep, Anchana; Robinson, Cliff; Romero, Javier; Schmidt, Allison L.; Short, Fred T.; van Tussenbroek, Brigitta I.; Santos, RuiThe available data from experimental and descriptive studies on seagrass biomass and density responses to nutrient enrichment were analysed to assess the intraspecific mechanisms operating within seagrass populations and whether biomass-density relationships can provide relevant metrics for monitoring seagrasses. The response of shoot biomass and density to nutrient enrichment was dependent on the type of study; the short-term positive response of biomass and density in experimental studies reveals context-specific nutrient limitation of seagrasses. The long-term negative response of descriptive studies probably results from ecosystem-scale events related to nutrient enrichment such as increased turbidity, algal blooms, epiphyte loads and anoxia. Most seagrass species analysed lie in the nonthinning part of the theoretical biomass-density curves. A simultaneous increase in biomass and decrease in density, evidence of self-thinning, were only observed in 4 of 28 studies. The analysis of both the static and the dynamic biomass-density relationships revealed that the slopes increase under nutrient enrichment. Surprisingly, the species-specific slopes (log B-log D) were higher than one, revealing that the B/D ratio, that is, the average shoot biomass, increases with density in all seagrass species analysed. Nutrient enrichment further enhanced this effect as biomass-density slopes increased to even higher values. The main drivers behind the increasing biomass-density slopes under nutrient enrichment were the increase in shoot biomass at densities above a species-specific threshold and/or its decrease below that threshold. Synthesis. Contrasting short- and long-term responses of both biomass and density of seagrasses to nutrient enrichment suggest that the former, positive ones result from nutrient limitation, whereas the later, negative ones are mediated by whole ecosystem responses. In general, shoot biomass of seagrasses increases with density, and nutrient enrichment enhances this effect. Experimental testing of facilitation processes related to clonal integration in seagrasses needs to be done to reveal whether they determine the low incidence of self-thinning and the intriguing biomass-density relationships of seagrass species. The increasing slopes and decreasing intercepts of the species-specific dynamic biomass-density relationships of seagrasses and the decreasing coefficients of variation of both biomass and density constitute relevant, easy-to-collect metrics that may be used in environmental monitoring.
- Toward a coordinated global observing system for seagrasses and marine macroalgaePublication . Duffy, J. Emmett; Benedetti-Cecchi, Lisandro; Trinanes, Joaquin; Muller-Karger, Frank E.; Ambo-Rappe, Rohani; Boström, Christoffer; Buschmann, Alejandro H.; Byrnes, Jarrett; Coles, Robert G.; Creed, Joel; Cullen-Unsworth, Leanne C.; Diaz-Pulido, Guillermo; Duarte, Carlos M.; Edgar, Graham J.; Fortes, Miguel; Goni, Gustavo; Hu, Chuanmin; Huang, Xiaoping; Hurd, Catriona L.; Johnson, Craig; Konar, Brenda; Krause-Jensen, Dorte; Krumhansl, Kira; Macreadie, Peter; Marsh, Helene; McKenzie, Len J.; Mieszkowska, Nova; Miloslavich, Patricia; Montes, Enrique; Nakaoka, Masahiro; Norderhaug, Kjell Magnus; Norlund, Lina M.; Orth, Robert J.; Prathep, Anchana; Putman, Nathan F.; Samper-Villarreal, Jimena; Serrao, Ester; Short, Frederick; Pinto, Isabel Sousa; Steinberg, Peter; Stuart-Smith, Rick; Unsworth, Richard K. F.; van Keulen, Mike; van Tussenbroek, Brigitta I.; Wang, Mengqiu; Waycott, Michelle; Weatherdon, Lauren V.; Wernberg, Thomas; Yaakub, Siti MaryamIn coastal waters around the world, the dominant primary producers are benthic macrophytes, including seagrasses and macroalgae, that provide habitat structure and food for diverse and abundant biological communities and drive ecosystem processes. Seagrass meadows and macroalgal forests play key roles for coastal societies, contributing to fishery yields, storm protection, biogeochemical cycling and storage, and important cultural values. These socio-economically valuable services are threatened worldwide by human activities, with substantial areas of seagrass and macroalgal forests lost over the last half-century. Tracking the status and trends in marine macrophyte cover and quality is an emerging priority for ocean and coastal management, but doing so has been challenged by limited coordination across the numerous efforts to monitor macrophytes, which vary widely in goals, methodologies, scales, capacity, governance approaches, and data availability. Here, we present a consensus assessment and recommendations on the current state of and opportunities for advancing global marine macrophyte observations, integrating contributions from a community of researchers with broad geographic and disciplinary expertise. With the increasing scale of human impacts, the time is ripe to harmonize marine macrophyte observations by building on existing networks and identifying a core set of common metrics and approaches in sampling design, field measurements, governance, capacity building, and data management. We recommend a tiered observation system, with improvement of remote sensing and remote underwater imaging to expand capacity to capture broad-scale extent at intervals of several years, coordinated with strati fied in situ sampling annually to characterize the key variables of cover and taxonomic or functional group composition, and to provide ground-truth. A robust networked system of macrophyte observations will be facilitated by establishing best practices, including standard protocols, documentation, and sharing of resources at all stages of work flow, and secure archiving of open-access data. Because such a network is necessarily distributed, sustaining it depends on close engagement of local stakeholders and focusing on building and long-term maintenance of local capacity, particularly in the developing world. Realizing these recommendations will producemore effective, efficient, and responsive observing, a more accurate global picture of change in vegetated coastal systems, and stronger international capacity for sustaining observations.