Successional dynamics of the cultivated kelp microbiome

Abstract

Kelp are important primary producers that are colonized by diverse microbes that can have both positive and negative effects on their hosts. The kelp microbiome could support the burgeoning kelp cultivation sector by improving host growth, stress tolerance, and resistance to disease. Fundamental questions about the cultivated kelp microbiome still need to be addressed before microbiome‐based approaches can be developed. A critical knowledge gap is how cultivated kelp microbiomes change as hosts grow, particularly following outplanting to sites that vary in abiotic conditions and microbial source pools. In this study we assessed if microbes that colonize kelp in the nursery stage persist after outplanting. We characterized microbiome succession over time on two species of kelp, Alaria marginata and Saccharina latissima, outplanted to open ocean cultivation sites in multiple geographic locations. We tested for host‐species specificity of the microbiome and the effect of different abiotic conditions and microbial source pools on kelp microbiome stability during the cultivation process. We found the microbiome of kelp in the nursery is distinct from that of outplanted kelp. Few bacteria persisted on kelp following outplanting. Instead, we identified significant microbiome differences correlated with host species and microbial source pools at each cultivation site. Microbiome variation related to sampling month also indicates that seasonality in host and/or abiotic factors may influence temporal succession and microbiome turnover in cultivated kelps. This study provides a baseline understanding of microbiome dynamics during kelp cultivation and highlights research needs for applying microbiome manipulation to kelp cultivation.

Host population crashes disrupt the diversity of associated marine microbiomes

“…Nevertheless, the role of vertical transmission may be diminished due to increased exposure of external microbial communities to the environment (Härer & Rennison, 2023), alongside the associated wave-induced biofilm and blade erosion. Out-planted cultivated macroalgae also exhibit low levels of nursery-microbe persistence, with greater acquisition of environmental microbes, suggesting horizontal transmission is a major factor in shaping macroalgal microbiomes (K. M. Davis et al, 2023). In addition, recent work has shown that the microbial communities associated with macroalgal rafts are significantly disrupted relative to non-rafts, with a declining abundance of core microbes-suggesting that horizontal acquisition of microbes is a preferential strategy for microbial community assembly in Durvillaea (Pearman, 2023).…”

Maturing giant kelp develop depth-specific microbiomes

“…Their prolific arsenal of bioactive compounds may benefit the host by shaping the microbiome and reducing biofouling of the surface (Lage and Bondoso, 2014; Graça et al ., 2016). Furthermore, other studies have shown that Pirellulaceae species are environmentally resilient and remain abundant in microbiomes from different kelp species and across habitats with variable abiotic conditions (Davis et al, 2023 Add Weigel and Pfister 2019).…”

“…Examining shifts in the giant kelp microbiome composition as the host ages is crucial for understanding the host-microbiome relationship and the fate of exuded DOC. Previous studies on multiple macroalgal species have demonstrated significant local effects (Lin et al ., 2018; Weigel and Pfister, 2019; James et al ., 2020; Davis et al ., 2023), and our findings reveal clear depth and age effects. Depth-specific differences in the microbial communities associated with mature blades suggests potential a mechanism for differences DOC remineralization throughout the water column.…”

“…Prior work has found that the microbial communities associated with the giant kelp canopy vary between geographic sites (Weigel and Pfister, 2019; James et al ., 2020) and as a function of their host’s physiological condition (James et al ., 2020), as has been seen in other foundational species of macroalgae (Marzinelli et al ., 2015; Phelps et al ., 2021; Wood et al ., 2022). Studies on different species of kelp and macroalgae demonstrated that both seasonality and hosts anatomy also impact microbiome development(Lemay et al ., 2021; Davis et al ., 2023). In mesocosm experiments simulating ocean warming and/or acidification, canopy forming kelp species ( Macrocystis, Ecklonia ) experienced considerable dysbiosis, showing dramatic changes in microbial community composition correlated with tissue damage or decreases in growth (Minich et al ., 2018).…”

Functional stability despite high taxonomic turnover characterizes the Ulva microbiome across a 2,000 km salinity gradient

“…20.599874 doi: bioRxiv preprint Seaweed-associated bacterial communities are far from static. Although a small core community can sometimes be identified, the bacteria form a highly dynamic community that fluctuates through time and space 13,14 . Abiotic factors, such as temperature, light, and salinity influence the community composition, as does the host itself [15][16][17] .…”