Cole Easson - Academia.edu (original) (raw)

Papers by Cole Easson

Research paper thumbnail of Niche structure of marine sponges from temperate hard-bottom habitats within Gray's Reef National Marine Sanctuary

Journal of the Marine Biological Association of the United Kingdom, 2015

Many species of marine sponges on tropical reefs host abundant and diverse symbiont communities c... more Many species of marine sponges on tropical reefs host abundant and diverse symbiont communities capable of varied metabolic pathways. While such communities may confer a nutritional benefit to some hosts (termed High Microbial Abundance (HMA) sponges), other sympatric species host only sparse symbiont communities (termed Low Microbial Abundance (LMA) sponges) and obtain a majority of their C and N from local sources. Sponge communities are widespread across large latitudinal gradients, however, and recent evidence suggests that these symbioses may also extend beyond the tropics. We investigated the role that symbionts play in the ecology of sponges from the temperate, hard-bottom reefs of Gray's Reef National Marine Sanctuary by calculating the niche size (as standard ellipse area (SEA c )) and assessing the relative placement of five HMA and four LMA sponge species within bivariate (d 13 C and d 15 N) isotopic space. Although photosymbiont abundance was low across most of these species, sponges were widespread across isotopic niche space, implying that microbial metabolism confers an ecological benefit to temperate sponges by expanding host metabolic capability. To examine how these associations vary across a latitudinal gradient, we also compared the relative placement of temperate and tropical conspecifics within isotopic space. Surprisingly, shifts in sponge d 13 C and d 15 N values between these regions suggest a reduced reliance on symbiontderived nutrients in temperate sponges compared with their tropical conspecifics. Despite this, symbiotic sponges in temperate systems likely have a competitive advantage, allowing them to grow and compete for space within these habitats.

Research paper thumbnail of Phylogenetic signal in the community structure of host-specific microbiomes of tropical marine sponges

Sponges (Porifera) can host diverse and abundant communities of microbial symbionts that make cru... more Sponges (Porifera) can host diverse and abundant communities of microbial symbionts that make crucial contributions to host metabolism. Although these communities are often host-specific and hypothesized to co-evolve with their hosts, correlations between host phylogeny and microbiome community structure are rarely tested. As part of the Earth Microbiome Project (EMP), we surveyed the microbiomes associated with 20 species of tropical marine sponges collected over a narrow geographic range. We tested whether (1) univariate metrics of microbiome diversity displayed significant phylogenetic signal across the host phylogeny; (2) host identity and host phylogeny were significant factors in multivariate analyses of taxonomic and phylogenetic dissimilarity; and (3) different minimum read thresholds impacted these results. We observed significant differences in univariate metrics of diversity among host species for all read thresholds, with strong phylogenetic signal in the inverse Simpson's index of diversity (D). We observed a surprisingly wide range of variability in community dissimilarity within host species (4-73%); this variability was not related to microbial abundance within a host species. Taxonomic and phylogenetic dissimilarity were significantly impacted by host identity and host phylogeny when these factors were considered individually; when tested together, the effect of host phylogeny was reduced, but remained significant. In our dataset, this outcome is largely due to closely related host sponges harboring distinct microbial taxa. Host identity maintained a strong statistical signal at all minimum read thresholds. Although the identity of specific microbial taxa varied substantially among host sponges, closely related hosts tended to harbor microbial communities with similar patterns of relative abundance. We hypothesize that microbiomes with low D might be structured by regulation of the microbial community by the host or by the presence of competitively dominant symbionts that are themselves under selection for host specificity.

Research paper thumbnail of Metabolic diversity and niche structure in sponges from the Miskito Cays, Honduras

PeerJ, 2014

Hosting symbionts provides many eukaryotes with access to the products of microbial metabolism th... more Hosting symbionts provides many eukaryotes with access to the products of microbial metabolism that are crucial for host performance. On tropical coral reefs, many (High Microbial Abundance [HMA]) but not all (Low Microbial Abundance [LMA]) marine sponges host abundant symbiont communities. Although recent research has revealed substantial variation in these sponge-microbe associations (termed holobionts), little is known about the ecological implications of this diversity. We investigated the expansion of diverse sponge species across isotopic niche space by calculating niche size (as standard ellipse area [SEA c ]) and assessing the relative placement of common sponge species in bivariate (δ (13)C and δ (15)N) plots. Sponges for this study were collected from the relatively isolated reefs within the Miskito Cays of Honduras. These reefs support diverse communities of HMA and LMA species that together span a gradient of photosymbiont abundance, as revealed by chlorophyll a analysis...

Research paper thumbnail of Exploring Individual- to Population-Level Impacts of Disease on Coral Reef Sponges: Using Spatial Analysis to Assess the Fate, Dynamics, and Transmission of Aplysina Red Band Syndrome (ARBS)

PLoS ONE, 2013

Background: Marine diseases are of increasing concern for coral reef ecosystems, but often their ... more Background: Marine diseases are of increasing concern for coral reef ecosystems, but often their causes, dynamics and impacts are unknown. The current study investigated the epidemiology of Aplysina Red Band Syndrome (ARBS), a disease affecting the Caribbean sponge Aplysina cauliformis, at both the individual and population levels. The fates of marked healthy and ARBS-infected sponges were examined over the course of a year. Population-level impacts and transmission mechanisms of ARBS were investigated by monitoring two populations of A. cauliformis over a three year period using digital photography and diver-collected data, and analyzing these data with GIS techniques of spatial analysis. In this study, three commonly used spatial statistics (Ripley's K, Getis-Ord General G, and Moran's Index) were compared to each other and with direct measurements of individual interactions using join-counts, to determine the ideal method for investigating disease dynamics and transmission mechanisms in this system. During the study period, Hurricane Irene directly impacted these populations, providing an opportunity to assess potential storm effects on A. cauliformis and ARBS.

Research paper thumbnail of Disease and nutrient enrichment as potential stressors on the Caribbean sponge Aplysina cauliformis and its bacterial symbionts

Marine Ecology Progress Series, 2012

Sponge diseases have recently emerged as potential forces structuring coral reefs. The increasing... more Sponge diseases have recently emerged as potential forces structuring coral reefs. The increasing prevalence of disease on reefs may be due to changes in the virulence of pathogens and/or to decreases in host resistance as a result of changing environmental conditions. Coral reef ecosystems typically thrive in oligotrophic waters; however, runoff of fertilizers or sewage that contains elevated concentrations of nutrients can lead to eutrophic conditions. Aplysina cauliformis is a dominant member of the Caribbean sponge community, and is susceptible to Aplysina Red Band Syndrome (ARBS), a disease that causes reduced sponge growth and survival. We assessed the independent and interacting effects of nutrient enrichment and disease on A. cauliformis, using a factorial field experiment in which healthy and diseased sponges were exposed to nutrient-enriched or non-enriched treatments. Impacts on ARBS virulence (rate of lesion growth) and host response (both sponge and cyanobacterial symbiont growth and physiology) were assessed. ARBS lesions increased rapidly regardless of nutrient treatment, and disease had a significantly greater detrimental impact on sponges than did nutrient enrichment, as evidenced by a decline in sponge mass and reduced total protein content. The sponge−cyanobacterial symbiont relationship was less impacted by disease, although the sponge-associated bacterial community was significantly affected by sponge condition, with healthy sponges and diseased tissue hosting significantly different bacterial assemblages. In contrast, nutrient enrichment had no effects on sponge or symbiont physiology. Disease is a much greater stressor than eutrophication on the growth and physiology of A. cauliformis and its cyanobacterial symbionts.

Research paper thumbnail of Niche structure of marine sponges from temperate hard-bottom habitats within Gray's Reef National Marine Sanctuary

Journal of the Marine Biological Association of the United Kingdom, 2015

Many species of marine sponges on tropical reefs host abundant and diverse symbiont communities c... more Many species of marine sponges on tropical reefs host abundant and diverse symbiont communities capable of varied metabolic pathways. While such communities may confer a nutritional benefit to some hosts (termed High Microbial Abundance (HMA) sponges), other sympatric species host only sparse symbiont communities (termed Low Microbial Abundance (LMA) sponges) and obtain a majority of their C and N from local sources. Sponge communities are widespread across large latitudinal gradients, however, and recent evidence suggests that these symbioses may also extend beyond the tropics. We investigated the role that symbionts play in the ecology of sponges from the temperate, hard-bottom reefs of Gray's Reef National Marine Sanctuary by calculating the niche size (as standard ellipse area (SEA c )) and assessing the relative placement of five HMA and four LMA sponge species within bivariate (d 13 C and d 15 N) isotopic space. Although photosymbiont abundance was low across most of these species, sponges were widespread across isotopic niche space, implying that microbial metabolism confers an ecological benefit to temperate sponges by expanding host metabolic capability. To examine how these associations vary across a latitudinal gradient, we also compared the relative placement of temperate and tropical conspecifics within isotopic space. Surprisingly, shifts in sponge d 13 C and d 15 N values between these regions suggest a reduced reliance on symbiontderived nutrients in temperate sponges compared with their tropical conspecifics. Despite this, symbiotic sponges in temperate systems likely have a competitive advantage, allowing them to grow and compete for space within these habitats.

Research paper thumbnail of Phylogenetic signal in the community structure of host-specific microbiomes of tropical marine sponges

Sponges (Porifera) can host diverse and abundant communities of microbial symbionts that make cru... more Sponges (Porifera) can host diverse and abundant communities of microbial symbionts that make crucial contributions to host metabolism. Although these communities are often host-specific and hypothesized to co-evolve with their hosts, correlations between host phylogeny and microbiome community structure are rarely tested. As part of the Earth Microbiome Project (EMP), we surveyed the microbiomes associated with 20 species of tropical marine sponges collected over a narrow geographic range. We tested whether (1) univariate metrics of microbiome diversity displayed significant phylogenetic signal across the host phylogeny; (2) host identity and host phylogeny were significant factors in multivariate analyses of taxonomic and phylogenetic dissimilarity; and (3) different minimum read thresholds impacted these results. We observed significant differences in univariate metrics of diversity among host species for all read thresholds, with strong phylogenetic signal in the inverse Simpson's index of diversity (D). We observed a surprisingly wide range of variability in community dissimilarity within host species (4-73%); this variability was not related to microbial abundance within a host species. Taxonomic and phylogenetic dissimilarity were significantly impacted by host identity and host phylogeny when these factors were considered individually; when tested together, the effect of host phylogeny was reduced, but remained significant. In our dataset, this outcome is largely due to closely related host sponges harboring distinct microbial taxa. Host identity maintained a strong statistical signal at all minimum read thresholds. Although the identity of specific microbial taxa varied substantially among host sponges, closely related hosts tended to harbor microbial communities with similar patterns of relative abundance. We hypothesize that microbiomes with low D might be structured by regulation of the microbial community by the host or by the presence of competitively dominant symbionts that are themselves under selection for host specificity.

Research paper thumbnail of Metabolic diversity and niche structure in sponges from the Miskito Cays, Honduras

PeerJ, 2014

Hosting symbionts provides many eukaryotes with access to the products of microbial metabolism th... more Hosting symbionts provides many eukaryotes with access to the products of microbial metabolism that are crucial for host performance. On tropical coral reefs, many (High Microbial Abundance [HMA]) but not all (Low Microbial Abundance [LMA]) marine sponges host abundant symbiont communities. Although recent research has revealed substantial variation in these sponge-microbe associations (termed holobionts), little is known about the ecological implications of this diversity. We investigated the expansion of diverse sponge species across isotopic niche space by calculating niche size (as standard ellipse area [SEA c ]) and assessing the relative placement of common sponge species in bivariate (δ (13)C and δ (15)N) plots. Sponges for this study were collected from the relatively isolated reefs within the Miskito Cays of Honduras. These reefs support diverse communities of HMA and LMA species that together span a gradient of photosymbiont abundance, as revealed by chlorophyll a analysis...

Research paper thumbnail of Exploring Individual- to Population-Level Impacts of Disease on Coral Reef Sponges: Using Spatial Analysis to Assess the Fate, Dynamics, and Transmission of Aplysina Red Band Syndrome (ARBS)

PLoS ONE, 2013

Background: Marine diseases are of increasing concern for coral reef ecosystems, but often their ... more Background: Marine diseases are of increasing concern for coral reef ecosystems, but often their causes, dynamics and impacts are unknown. The current study investigated the epidemiology of Aplysina Red Band Syndrome (ARBS), a disease affecting the Caribbean sponge Aplysina cauliformis, at both the individual and population levels. The fates of marked healthy and ARBS-infected sponges were examined over the course of a year. Population-level impacts and transmission mechanisms of ARBS were investigated by monitoring two populations of A. cauliformis over a three year period using digital photography and diver-collected data, and analyzing these data with GIS techniques of spatial analysis. In this study, three commonly used spatial statistics (Ripley's K, Getis-Ord General G, and Moran's Index) were compared to each other and with direct measurements of individual interactions using join-counts, to determine the ideal method for investigating disease dynamics and transmission mechanisms in this system. During the study period, Hurricane Irene directly impacted these populations, providing an opportunity to assess potential storm effects on A. cauliformis and ARBS.

Research paper thumbnail of Disease and nutrient enrichment as potential stressors on the Caribbean sponge Aplysina cauliformis and its bacterial symbionts

Marine Ecology Progress Series, 2012

Sponge diseases have recently emerged as potential forces structuring coral reefs. The increasing... more Sponge diseases have recently emerged as potential forces structuring coral reefs. The increasing prevalence of disease on reefs may be due to changes in the virulence of pathogens and/or to decreases in host resistance as a result of changing environmental conditions. Coral reef ecosystems typically thrive in oligotrophic waters; however, runoff of fertilizers or sewage that contains elevated concentrations of nutrients can lead to eutrophic conditions. Aplysina cauliformis is a dominant member of the Caribbean sponge community, and is susceptible to Aplysina Red Band Syndrome (ARBS), a disease that causes reduced sponge growth and survival. We assessed the independent and interacting effects of nutrient enrichment and disease on A. cauliformis, using a factorial field experiment in which healthy and diseased sponges were exposed to nutrient-enriched or non-enriched treatments. Impacts on ARBS virulence (rate of lesion growth) and host response (both sponge and cyanobacterial symbiont growth and physiology) were assessed. ARBS lesions increased rapidly regardless of nutrient treatment, and disease had a significantly greater detrimental impact on sponges than did nutrient enrichment, as evidenced by a decline in sponge mass and reduced total protein content. The sponge−cyanobacterial symbiont relationship was less impacted by disease, although the sponge-associated bacterial community was significantly affected by sponge condition, with healthy sponges and diseased tissue hosting significantly different bacterial assemblages. In contrast, nutrient enrichment had no effects on sponge or symbiont physiology. Disease is a much greater stressor than eutrophication on the growth and physiology of A. cauliformis and its cyanobacterial symbionts.