Biology subjects

Parfrey, L.

Publications and source records attributed to Parfrey, L..

5 recordsLinked to original sources

bioRxiv2025

Dispersal transiently modifies the temperature dependence of ecosystem productivity after an extreme thermal fluctuation

Effects of warming on ecosystem productivity are typically summarized over broad time scales, yet they emerge from communities that can reorganize in a matter of days. Temperature accelerates ecosystem productivity through predictable effects on metabolic rates, but dispersal across thermally heterogeneous metacommunities may modify this effect by redistributing communities and their underlying thermal phenotypes. Using multi-trophic freshwater mesocosm communities in which warming and dispersal were manipulated, we tested the hypothesis that increasing dispersal modifies the thermal sensitivity of gross primary productivity (GPP) through the redistribution of phytoplankton biomass, size spectra, and thermal phenotype composition along spatial thermal gradients. High dispersal temporarily weakened the thermal sensitivity of GPP after an unplanned heatwave. This effect was caused by reduced mass-specific GPP in the warmest mesocosms accompanied by regional homogenization of phytoplankton communities and the spread of poorly adapted thermal phenotypes under the highest dispersal treatments. Except immediately post-heatwave, the thermal sensitivity of GPP was robust to dispersal, despite evidence of metacommunity dynamics. These findings suggest that the temperature dependence of ecosystem metabolism can be briefly modified by dispersal after a perturbation, but remains robust under steady-state conditions.

ecology↗

bioRxiv2025

An experimental test of the influence of microbial manipulation on sugar kelp (Saccharina latissima) supports the the core influences host function hypothesis

Kelp are valued for a wide range of commercial products and for their role in kelp forest ecosystems, making kelp cultivation a rapidly expanding economic sector. Microbes associated with kelp and other macroalgae play a critical role in processes such as nutrient exchange, chemical signaling, and defense against pathogens. Thus, manipulating the microbiome to enhance macroalgal growth and resilience is a promising yet underexplored approach for sustainable kelp cultivation. The core microbiome hypothesis suggests that the bacteria that are consistently found on a host (the core microbes) are likely to have a disproportionate impact on host biology, making them an attractive target for microbiome manipulation. In this study, we surveyed wild Saccharina latissima and their surrounding environment to identify core bacterial taxa, compared them to cultivated kelp, and experimentally tested how cultured bacterial isolates affect kelp development. We found that core bacteria are nearly absent in cultivated juvenile sporophytes in nurseries but eventually colonized them after outplanting to ocean farm sites. Bacterial inoculants had both positive and negative effects on kelp development. Notably, the strength of association of a bacterial genus with kelp in the wild positively correlated with its impact on gametophyte settlement and sporophyte development in kelp co-culture experiments, aligning with predictions from the core microbiome influences host function hypothesis. These findings affirm the feasibility of using microbial manipulations to improve current kelp aquaculture practices and provide a framework for developing these techniques. IMPORTANCEMicroorganisms consistently associated with hosts are widely thought to be more likely to impact host biology and health. However, this intuitive concept has not been experimentally evaluated. This study formalizes this concept as the Core microbiome Influences Host Function hypothesis and experimentally tests this hypothesis in sugar kelp (Saccharina). The distribution of bacteria on wild kelp and core microbes were first identified by compiling a broad dataset of the kelp microbiome sampled across space and time. Bacterial cultures were isolated from the surface of sugar kelp and individually grown in laboratory co-culture with sugar kelp spores to assess the ability of bacterial isolates to influence kelp growth and development. In support of the core influences host function hypothesis, isolates belonging to bacterial genera that are more strongly associated with wild sugar kelp are more likely to influence development in laboratory experiments.

ecology↗

bioRxiv2025

Novel pink-spot disease in North American kelpnurseries

Macroalgal cultivation is a growing industry in North America, but is well established in Asia and Africa, where macroalgal disease cause crop losses, placing a significant economic burden on farmers. As kelp cultivation intensifies in North America, kelp disease prevalence is expected to increase in tandem. With input from the kelp-growing community through an online survey, we describe the prevalence of a novel kelp disease, pink-spot disease, which has been observed in Canada and the United States on Saccharina latissima, Alaria marginata, Nereocystis luetkeana, and Macrocystis tenuifolia. Eight of the fourteen (57%) surveyed kelp growers report bright pink spots (pink-spot disease) on their kelp spools in the land-based nursery stage. Along with the grower survey, we conducted 16S rRNA amplicon sequencing in 2021 and 2022 to investigate the causative agent of pink-spot disease and associated bacterial community changes on infected Saccharina latissima (sugar kelp) spools. Our data in both years show that a member of the genus Algicola is enriched on visibly diseased spool regions compared to asymptomatic spool regions and may be the causative agent of pink-spot disease. As macroalgal cultivation continues to intensify, monitoring diseases is important to mitigate potential negative impacts.

ecology↗

bioRxiv2023

Low salinity significantly alters the bacterial community of the marine foundation species Saccharina latissima (sugar kelp)

As climate change progresses, the intensity and variability of freshwater outflow into the ocean are predicted to increase. The resulting increase in low-salinity events will be a source of stress for Saccharina latissima and potentially Saccharina-associated bacteria. Bacteria influence host health and can facilitate or hinder host survival and acclimation to stressful abiotic conditions. Therefore, understanding how bacterial communities change under abiotic stress is critical to understand how abiotic stress will affect kelp physiology. We investigated the effect of low-salinity stress on Saccharina-associated bacteria and the host by surveying the bacterial community associated with Saccharina and the surrounding environment across naturally occurring salinity gradients during the spring freshet across two years at four field sites with contrasting salinity profiles around Vancouver, Canada (519 samples), coupled with salinity manipulation experiments repeated eight times (269 samples). Overall, Saccharina harbours a stable core bacterial community, which decreases in relative abundance under abiotic stress. In the field, both salinity and temperature shape the bacterial community, with temperature having higher explanatory power most of the time. In the lab, we confirm that the patterns observed in the field can be replicated by manipulating salinity alone. Decreased relative abundance of core bacteria and increased community dissimilarity in low salinity, in both the lab and field, suggest that host filtering is significantly impaired in low salinity. In the context of a stable host-associated core bacterial community during non-stressful conditions, the change in the community composition observed during conditions of abiotic stress indicates a host stress response.

ecology↗

bioRxiv2019

Exposure to parasitic protists and helminths changes the intestinal community structure of bacterial microbiota but not of eukaryotes in a cohort of mother-child binomial from a semi-rural setting in Mexico

Around 3.5 billion people are colonized by intestinal parasites worldwide. Intestinal parasitic eukaryotes interact not only with the host, but also with the intestinal microbiota. In this work, we studied the relationship between the presence of multiple enteric parasites and the community structure of the bacterial and eukaryote intestinal microbiota in an asymptomatic cohort of mother-child binomials from a semi-rural community in Mexico. The intestinal parasites identified were Blastocystis hominis, Entamoeba histolytica/dispar, Endolimax nana, Chilomastix mesnili, Iodamoeba butshlii, Entamoeba coli, Hymenolepis nana and Ascaris lumbricoides. We sequenced bacterial 16S rDNA and eukaryotic 18S rDNA in fecal samples of 46 mothers and their respective children, with ages ranging from two to twenty months. Although we did not find significant alpha-diversity changes, we found a significant effect of parasite exposure on bacterial beta-diversity, which explained between 5.2% and 15.0% of the variation of the bacterial community structure. Additionally, exposure to parasites was associated with significant changes in relative abundances of bacterial taxa, characterized by increases in the Clostridia and decreased Actinobacteria and Bacteroidia abundances. There were no significant changes of intestinal microeukaryote abundances associated with parasite exposure. However, we found several significant positive correlations between intestinal bacteria and eukaryotes, including co-occurrence of the fungi Candida tropicalis with Bacteroides and Actinomyces, and Saccharomycetales with Bifidobacterium and Prevotella copri. These bacterial community structure changes associated with parasite exposure imply effects on microbial metabolic routes, host nutrient uptake abilities and intestinal immunity regulation in host-parasite interactions.\n\nIMPORTANCEThe impact of intestinal eukaryotes on the prokaryotic microbiome composition of asymptomatic carriers has not been extensively explored, especially in children and in hosts with multiple parasites. In this work, we studied the relationship between protist and helminth parasite colonization and intestinal microbiota structure in an asymptomatic population of mother-child binomials from the semi-rural community of Morelos in Mexico. We found that the presence of parasitic eukaryotes correlated with changes in the bacterial community structure in the intestinal microbiota in an age-dependent way. This was characterized by an increase of the relative abundance of the class Clostridia and the decrease of Actinobacteria and Bacteroidia. While there were no significant associations between the presence of parasites and microeukaryote community structure, we observed strong positive correlations between bacterial and eukaryote taxa, identifying novel relationships between prokaryotes and fungi, and reflecting the diet of the human population studied.

microbiology↗