Heidi Luter - Profile on Academia.edu (original) (raw)

Papers by Heidi Luter

Marine Biology Research, 2007

Secondary metabolites from marine invertebrates, such as sponges, have diverse ecological roles a... more Secondary metabolites from marine invertebrates, such as sponges, have diverse ecological roles and may be used in antipredation, anti-fouling and spatial competition. The thin encrusting sponge Iotrochota sp., found on the Great Barrier Reef, Australia, contains several novel indoles that may aid in spatial competition. To examine whether levels of surrounding competition affect the toxicity of Iotrochota sp., 24 sponges from Salamander Reef, Central Great Barrier Reef, subject to either high or low levels of surrounding competition, were sampled. Tissue samples were taken from areas where the sponge was in direct competition with neighbouring sessile invertebrates, as well as from areas where competition was less obvious. Compounds from the tissue samples were extracted and tested in both cytotoxicity and anti-microbial assays. However, neither cytotoxicity nor anti-microbial activity varied significantly between the high and low competition treatments. Cytotoxicity was greatest among large sponges, suggesting that size is an important factor contributing to the toxicity of Iotrochota sp. sponges in this study.

PloS one, 2012

Background: Marine diseases are being increasingly linked to anthropogenic factors including glob... more Background: Marine diseases are being increasingly linked to anthropogenic factors including global and local stressors. On the Great Barrier Reef, up to 66% of the Ianthella basta population was recently found to be afflicted by a syndrome characterized by brown spot lesions and necrotic tissue.

The effects of disease and stress on the microbial community of the sponge Ianthella basta

Levels of nitrogen in coastal areas have been rapidly increasing due to accumulative inputs of se... more Levels of nitrogen in coastal areas have been rapidly increasing due to accumulative inputs of sewage and terrigenous sediments carrying fertilizers. Sponges have an immense filtering capacity and may be directly impacted (positively or negatively) by elevated concentrations of nitrogen. Sponges also host a wide diversity of microbes involved in nitrogen metabolism, yet little is known about the effects of nitrogen loading on these symbiotic partnerships. Manipulative experiments were undertaken to examine the potential effects of excess nitrogen (up to 240 μM) on microbial symbiosis in the abundant sponge species Cymbastela stipitata. Microbial composition and activity were examined using 454-pyrotag sequencing of DNA-and RNA-derived samples. Despite the high levels of nitrogen exposure (up to 124-fold above ambient), sponges appeared visibly unaffected at all treatment concentrations. At the phylum level, the microbial community was consistent between all sponge samples regardless of nitrogen treatment, with Cyanobacteria and Thaumarchaeota being the dominant taxa. Higher microbial diversity was observed at the operational taxonomic units (OTU) level (97% sequence similarity), with only 40% of OTUs shared between samples from all treatments. However, a single cyanobacterial OTU dominated the community of all individuals (average 73.5%) and this OTU did not vary with nitrogen treatment. The conserved microbial community in all sponges irrespective of nitrogen treatment highlights the stability of the sponge-microbe relationship and indicates that the holobiont is resistant to short pulses of nitrogen at levels mimicking sewage effluent.

Sponges biosynthesize a wealth of secondary metabolites, many with novel structures and strong bi... more Sponges biosynthesize a wealth of secondary metabolites, many with novel structures and strong biological activity. Such compounds may serve multiple ecological roles including anti-predation, anti-fouling functionalities and are implicated in border defense or attack during spatial competition. Relative size of benthic organisms may also play an important role in competitive interactions. To determine if a relationship exists between individual size and bioactive metabolite production in the context of spatial competition, we examined three sponge species with different morphologies: the massive Coscinoderma matthewsi, the club-shaped branching Hyrtios erecta, and the fan-shaped Ianthella basta. Extracts from sponges of various sizes and competitive environments were examined using a cell based bioassay as a proxy of bioactivity. For I. basta, sponge size was correlated with bioactivity; the largest individuals generally being the most bioactive. In contrast, there was no correlation between size and bioactivity for either C. matthewsi or H. erecta. Bioactivity of sponges in this study were however highly variable among individuals, regardless of levels of competition. The prevalence of encroaching organisms was not correlated with sponge size for any of the three sponge species, suggesting that potential bioactivity is not influenced by surrounding competition.

Marine Ecology Progress Series, 2009

Spatial variability in abundance and size of sponges are poorly understood compared with other se... more Spatial variability in abundance and size of sponges are poorly understood compared with other sessile organisms such as corals. A hierarchical survey design across 3 spatial scalessites nested in locations nested in island groups -examined variation in sponge size and abundance for the common coral reef sponge Coscinoderma matthewsi (Lendenfed, 1886) (Demospongiae: Dictyoceratida) in Torres Strait, northern Australia. The abundance of C. matthewsi differed significantly across all 3 spatial scales, varying greatly between sites 200 m apart up to island groups 60 km apart. The size frequency distributions of C. matthewsi varied between sites and island groups, and were positively skewed with populations dominated by small sponges. There was no relationship between sponge abundance and size within and between island groups for C. matthewsi in Torres Strait.

Applied and Environmental Microbiology, 2010

A disease-like syndrome is currently affecting a large percentage of the Ianthella basta populati... more A disease-like syndrome is currently affecting a large percentage of the Ianthella basta populations from the Great Barrier Reef and central Torres Strait. Symptoms of the syndrome include discolored, necrotic spots leading to tissue degradation, exposure of the skeletal fibers, and disruption of the choanocyte chambers. To ascertain the role of microbes in the disease process, a comprehensive comparison of bacteria, viruses, fungi, and other eukaryotes was performed in healthy and diseased sponges using multiple techniques. A low diversity of microbes was observed in both healthy and diseased sponge communities, with all sponges dominated by an Alphaproteobacteria, a Gammaproteobacteria, and a group I crenarchaeota. Bacterial cultivation, community analysis by denaturing gradient gel electrophoresis (Bacteria and Eukarya), sequencing of 16S rRNA clone libraries (Bacteria and Archaea), and direct visual assessment by electron microscopy failed to reveal any putative pathogens. In addition, infection assays could not establish the syndrome in healthy sponges even after direct physical contact with affected tissue. These results suggest that microbes are not responsible for the formation of brown spot lesions and necrosis in I. basta.

MicrobiologyOpen, 2014

Microbial source tracking is an area of research in which multiple approaches are used to identif... more Microbial source tracking is an area of research in which multiple approaches are used to identify the sources of elevated bacterial concentrations in recreational lakes and beaches. At our study location in Darwin, northern Australia, water quality in the harbor is generally good, however dry-season beach closures due to elevated Escherichia coli and enterococci counts are a cause for concern. The sources of these high bacteria counts are currently unknown. To address this, we sampled sewage outfalls, other potential inputs, such as urban rivers and drains, and surrounding beaches, and used genetic fingerprints from E. coli and enterococci communities, fecal markers and 454 pyrosequencing to track contamination sources. A sewage effluent outfall (Larrakeyah discharge) was a source of bacteria, including fecal bacteria that impacted nearby beaches. Two other treated effluent discharges did not appear to influence sites other than those directly adjacent. Several beaches contained fecal indicator bacteria that likely originated from urban rivers and creeks within the catchment. Generally, connectivity between the sites was observed within distinct geographical locations and it appeared that most of the bacterial contamination on Darwin beaches was confined to local sources.

Marine Biology Research, 2007

Secondary metabolites from marine invertebrates, such as sponges, have diverse ecological roles a... more Secondary metabolites from marine invertebrates, such as sponges, have diverse ecological roles and may be used in antipredation, anti-fouling and spatial competition. The thin encrusting sponge Iotrochota sp., found on the Great Barrier Reef, Australia, contains several novel indoles that may aid in spatial competition. To examine whether levels of surrounding competition affect the toxicity of Iotrochota sp., 24 sponges from Salamander Reef, Central Great Barrier Reef, subject to either high or low levels of surrounding competition, were sampled. Tissue samples were taken from areas where the sponge was in direct competition with neighbouring sessile invertebrates, as well as from areas where competition was less obvious. Compounds from the tissue samples were extracted and tested in both cytotoxicity and anti-microbial assays. However, neither cytotoxicity nor anti-microbial activity varied significantly between the high and low competition treatments. Cytotoxicity was greatest among large sponges, suggesting that size is an important factor contributing to the toxicity of Iotrochota sp. sponges in this study.

Prevalence of tissue necrosis and brown spot lesions in a common marine sponge

Marine and Freshwater Research, 2010

Page 1. Prevalence of tissue necrosis and brown spot lesions in a common marine sponge Heidi M. L... more Page 1. Prevalence of tissue necrosis and brown spot lesions in a common marine sponge Heidi M. Luter A,B,C,D , Steve Whalan B and Nicole S. Webster B ... We also thank C. Wolff, L. Evans-Illidge, K. Johns and J. Morris for diving and fieldwork. ...

Applied and environmental …, 2010

A disease-like syndrome is currently affecting a large percentage of the Ianthella basta populati... more A disease-like syndrome is currently affecting a large percentage of the Ianthella basta populations from the Great Barrier Reef and central Torres Strait. Symptoms of the syndrome include discolored, necrotic spots leading to tissue degradation, exposure of the skeletal fibers, and disruption of the choanocyte chambers. To ascertain the role of microbes in the disease process, a comprehensive comparison of bacteria, viruses, fungi, and other eukaryotes was performed in healthy and diseased sponges using multiple techniques. A low diversity of microbes was observed in both healthy and diseased sponge communities, with all sponges dominated by an Alphaproteobacteria, a Gammaproteobacteria, and a group I crenarchaeota. Bacterial cultivation, community analysis by denaturing gradient gel electrophoresis (Bacteria and Eukarya), sequencing of 16S rRNA clone libraries (Bacteria and Archaea), and direct visual assessment by electron microscopy failed to reveal any putative pathogens. In addition, infection assays could not establish the syndrome in healthy sponges even after direct physical contact with affected tissue. These results suggest that microbes are not responsible for the formation of brown spot lesions and necrosis in I. basta.

Symbioses in marine sponges involve diverse consortia of microorganisms that contribute to the he... more Symbioses in marine sponges involve diverse consortia of microorganisms that contribute to the health and ecology of their hosts. The microbial communities of 13 taxonomically diverse Great Barrier Reef (GBR) sponge species were assessed by DGGE and 16S rRNA gene sequencing to determine intra and inter species variation in bacterial symbiont composition. Microbial profiling revealed communities that were largely conserved within different individuals of each species with intra species similarity ranging from 65-100%. 16S rRNA gene sequencing revealed that the communities were dominated by Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, Nitrospira, and Cyanobacteria. Sponge-associated microbes were also highly host-specific with no operational taxonomic units (OTUs) common to all species and the most ubiquitous OTU found in only 5 of the 13 sponge species. In total, 91% of the OTUs were restricted to a single sponge species. However, GBR sponge microbes were more closely related to other sponge-derived bacteria than they were to environmental communities with sequences falling within 50 of the 173 previously defined sponge-(or sponge-coral) specific sequence clusters (SC). These SC spanned the Acidobacteria, Actinobacteria, Proteobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Gemmatimonadetes, Nitrospira, and the Planctomycetes-Verrucomicrobia-Chlamydiae superphylum. The number of sequences assigned to these sponge-specific clusters across all species ranged from 0 to 92%. No relationship between host phylogeny and symbiont communities were observed across the different sponge orders, although the highest level of similarity was detected in two closely related Xestospongia species. This study identifies the core microbial inhabitants in a range of GBR sponges thereby providing the basis for future studies on sponge symbiotic function and research aiming to predict how sponge holobionts will respond to environmental perturbation.

Sponges often exhibit tissue regression in response to stressful conditions. This study investiga... more Sponges often exhibit tissue regression in response to stressful conditions. This study investigated whether handling stress invoked tissue regression in Ianthella basta and assessed whether sponges could recover from this regressed tissue state. Six necrotic specimens and 12 healthy explants were collected at Orpheus Is. Australia and transported to aquarium facilities. Sponges were photographed daily and an integrated density (ID) measurement was used to quantify tissue regression. Histological samples were taken from sponge explants to compare cellular organization. Bacterial communities of regressed and recovered tissue were compared using Denaturing Gradient Gel Electrophoresis (DGGE). After 12 h both necrotic and healthy sponges displayed substantial tissue regression. However, within 72 h all sponges recovered to their original condition. The ID of the sponge tissue doubled, confirming tissue recovery in I. basta. Sponges affected by tissue regression had significantly fewer choanocyte chambers and more densely packed granulated cells than recovered sponges. DGGE revealed the same microbial symbionts in both regressed and recovered sponges. Handling stress associated with collection and transportation is sufficient to invoke tissue regression in this species, but sponges can rapidly recover. This study contributes to our understanding of how sponges respond to environmental pressures, influencing population resilience and persistence.

Morphological delineation of sponge species is hindered by the narrow range of fixed diagnostic c... more Morphological delineation of sponge species is hindered by the narrow range of fixed diagnostic characters and our limited knowledge of how much phenotypic plasticity the sponge body plan assumes in response to environmental conditions. Here, we make use of the partial mitochondrial cytochrome c oxidase subunit I (COI) gene and the second internal transcribed spacer (ITS2) region to assess the taxonomic validity of colour morphotypes observed in the elephant ear sponge Ianthella basta (Pallas, 1776) across its distribution range in northern Australia, and explore levels and patterns of genetic diversity among populations of the species collected from both sides of the Torres Strait. Molecular phylogenetic analyses revealed congruent topologies consistent with three evolutionarily significant units (ESUs) that were independent of the morphology of the sponge. ESU I includes previously morphologically and genetically delineated western Pacific specimens of I. basta (Guam), and probably corresponds to the type specimen originally described from Indonesia. ESU I occurs in almost all sampling sites across northern Australia, suggesting considerable levels of connectivity among reefs throughout the Torres Strait. ESUs II and III are each exclusively associated with a geographic region of high sponge species richness separated by Torres Strait, and probably represent the result of historical population fragmentation.

Natural populations of marine invertebrates often exhibit measureable morphologic variation resul... more Natural populations of marine invertebrates often exhibit measureable morphologic variation resulting in taxonomic confusion. This potentially has severe consequences for experimental design and data management. Species of the sponge genus Ianthella embody a number of different morphologies and a diverse range of secondary metabolites. Among them, Ianthella basta (Pallas, 1776), a common sponge in Papua New Guinea and the Great Barrier Reef (GBR), exhibits two dominant colour morphotypes: yellow and purple. Specimens collected from Orpheus Island on the GBR were investigated using phylogenetic (CO1, ITS-2 sequence analysis), chemical (mass spectrometry) and microbial (DGGE and 16S rRNA clone library) techniques in an effort to fully characterise the two colour morphs. Phylogenetic analyses indicated sharp genetic discontinuities within I. basta sensu lato independent of colour variation. The two morphotypes did, however, correspond to distinct DGGE profiles largely due to the presence of additional bands in the purple morpho-group. Further comparison of the microbial communities by 16S rRNA gene sequencing revealed that whilst both colour morphs were dominated by only two bacterial symbionts (residing within the Gamma and Alphaproteobacteria), the purple morph also contained minor representatives of the Cyanobacteria, Chloroflexi and Verrucomicrobia. Untargeted metabolic profiling by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) indicated two distinct clusters corresponding to the different sponge colours. A clear association was found between the araplysillin class of compounds and the purple morphotype of I. basta, indicating the utility of a metabolomic approach to assess differences between colour morphs. These results have important implications for ecological investigations in sponges and other invertebrate taxa whose morphology is fundamentally dynamic, stressing the need for precise taxonomic, chemical and microbial descriptions.

Background: Marine diseases are being increasingly linked to anthropogenic factors including glob... more Background: Marine diseases are being increasingly linked to anthropogenic factors including global and local stressors. On the Great Barrier Reef, up to 66% of the Ianthella basta population was recently found to be afflicted by a syndrome characterized by brown spot lesions and necrotic tissue.

MicrobiologyOpen, 2014

Microbial source tracking is an area of research in which multiple approaches are used to identif... more Microbial source tracking is an area of research in which multiple approaches are used to identify the sources of elevated bacterial concentrations in recreational lakes and beaches. At our study location in Darwin, northern Australia, water quality in the harbor is generally good, however dry-season beach closures due to elevated Escherichia coli and enterococci counts are a cause for concern. The sources of these high bacteria counts are currently unknown. To address this, we sampled sewage outfalls, other potential inputs, such as urban rivers and drains, and surrounding beaches, and used genetic fingerprints from E. coli and enterococci communities, fecal markers and 454 pyrosequencing to track contamination sources. A sewage effluent outfall (Larrakeyah discharge) was a source of bacteria, including fecal bacteria that impacted nearby beaches. Two other treated effluent discharges did not appear to influence sites other than those directly adjacent. Several beaches contained fecal indicator bacteria that likely originated from urban rivers and creeks within the catchment. Generally, connectivity between the sites was observed within distinct geographical locations and it appeared that most of the bacterial contamination on Darwin beaches was confined to local sources.

MicrobiologyOpen, 2014

Microbial source tracking is an area of research in which multiple approaches are used to identif... more Microbial source tracking is an area of research in which multiple approaches are used to identify the sources of elevated bacterial concentrations in recreational lakes and beaches. At our study location in Darwin, northern Australia, water quality in the harbor is generally good, however dry-season beach closures due to elevated Escherichia coli and enterococci counts are a cause for concern. The sources of these high bacteria counts are currently unknown. To address this, we sampled sewage outfalls, other potential inputs, such as urban rivers and drains, and surrounding beaches, and used genetic fingerprints from E. coli and enterococci communities, fecal markers and 454 pyrosequencing to track contamination sources. A sewage effluent outfall (Larrakeyah discharge) was a source of bacteria, including fecal bacteria that impacted nearby beaches. Two other treated effluent discharges did not appear to influence sites other than those directly adjacent. Several beaches contained fecal indicator bacteria that likely originated from urban rivers and creeks within the catchment. Generally, connectivity between the sites was observed within distinct geographical locations and it appeared that most of the bacterial contamination on Darwin beaches was confined to local sources.

Marine Biology Research, 2007

Secondary metabolites from marine invertebrates, such as sponges, have diverse ecological roles a... more Secondary metabolites from marine invertebrates, such as sponges, have diverse ecological roles and may be used in antipredation, anti-fouling and spatial competition. The thin encrusting sponge Iotrochota sp., found on the Great Barrier Reef, Australia, contains several novel indoles that may aid in spatial competition. To examine whether levels of surrounding competition affect the toxicity of Iotrochota sp., 24 sponges from Salamander Reef, Central Great Barrier Reef, subject to either high or low levels of surrounding competition, were sampled. Tissue samples were taken from areas where the sponge was in direct competition with neighbouring sessile invertebrates, as well as from areas where competition was less obvious. Compounds from the tissue samples were extracted and tested in both cytotoxicity and anti-microbial assays. However, neither cytotoxicity nor anti-microbial activity varied significantly between the high and low competition treatments. Cytotoxicity was greatest among large sponges, suggesting that size is an important factor contributing to the toxicity of Iotrochota sp. sponges in this study.

PloS one, 2012

Background: Marine diseases are being increasingly linked to anthropogenic factors including glob... more Background: Marine diseases are being increasingly linked to anthropogenic factors including global and local stressors. On the Great Barrier Reef, up to 66% of the Ianthella basta population was recently found to be afflicted by a syndrome characterized by brown spot lesions and necrotic tissue.

The effects of disease and stress on the microbial community of the sponge Ianthella basta

Levels of nitrogen in coastal areas have been rapidly increasing due to accumulative inputs of se... more Levels of nitrogen in coastal areas have been rapidly increasing due to accumulative inputs of sewage and terrigenous sediments carrying fertilizers. Sponges have an immense filtering capacity and may be directly impacted (positively or negatively) by elevated concentrations of nitrogen. Sponges also host a wide diversity of microbes involved in nitrogen metabolism, yet little is known about the effects of nitrogen loading on these symbiotic partnerships. Manipulative experiments were undertaken to examine the potential effects of excess nitrogen (up to 240 μM) on microbial symbiosis in the abundant sponge species Cymbastela stipitata. Microbial composition and activity were examined using 454-pyrotag sequencing of DNA-and RNA-derived samples. Despite the high levels of nitrogen exposure (up to 124-fold above ambient), sponges appeared visibly unaffected at all treatment concentrations. At the phylum level, the microbial community was consistent between all sponge samples regardless of nitrogen treatment, with Cyanobacteria and Thaumarchaeota being the dominant taxa. Higher microbial diversity was observed at the operational taxonomic units (OTU) level (97% sequence similarity), with only 40% of OTUs shared between samples from all treatments. However, a single cyanobacterial OTU dominated the community of all individuals (average 73.5%) and this OTU did not vary with nitrogen treatment. The conserved microbial community in all sponges irrespective of nitrogen treatment highlights the stability of the sponge-microbe relationship and indicates that the holobiont is resistant to short pulses of nitrogen at levels mimicking sewage effluent.

Sponges biosynthesize a wealth of secondary metabolites, many with novel structures and strong bi... more Sponges biosynthesize a wealth of secondary metabolites, many with novel structures and strong biological activity. Such compounds may serve multiple ecological roles including anti-predation, anti-fouling functionalities and are implicated in border defense or attack during spatial competition. Relative size of benthic organisms may also play an important role in competitive interactions. To determine if a relationship exists between individual size and bioactive metabolite production in the context of spatial competition, we examined three sponge species with different morphologies: the massive Coscinoderma matthewsi, the club-shaped branching Hyrtios erecta, and the fan-shaped Ianthella basta. Extracts from sponges of various sizes and competitive environments were examined using a cell based bioassay as a proxy of bioactivity. For I. basta, sponge size was correlated with bioactivity; the largest individuals generally being the most bioactive. In contrast, there was no correlation between size and bioactivity for either C. matthewsi or H. erecta. Bioactivity of sponges in this study were however highly variable among individuals, regardless of levels of competition. The prevalence of encroaching organisms was not correlated with sponge size for any of the three sponge species, suggesting that potential bioactivity is not influenced by surrounding competition.

Marine Ecology Progress Series, 2009

Spatial variability in abundance and size of sponges are poorly understood compared with other se... more Spatial variability in abundance and size of sponges are poorly understood compared with other sessile organisms such as corals. A hierarchical survey design across 3 spatial scalessites nested in locations nested in island groups -examined variation in sponge size and abundance for the common coral reef sponge Coscinoderma matthewsi (Lendenfed, 1886) (Demospongiae: Dictyoceratida) in Torres Strait, northern Australia. The abundance of C. matthewsi differed significantly across all 3 spatial scales, varying greatly between sites 200 m apart up to island groups 60 km apart. The size frequency distributions of C. matthewsi varied between sites and island groups, and were positively skewed with populations dominated by small sponges. There was no relationship between sponge abundance and size within and between island groups for C. matthewsi in Torres Strait.

Applied and Environmental Microbiology, 2010

A disease-like syndrome is currently affecting a large percentage of the Ianthella basta populati... more A disease-like syndrome is currently affecting a large percentage of the Ianthella basta populations from the Great Barrier Reef and central Torres Strait. Symptoms of the syndrome include discolored, necrotic spots leading to tissue degradation, exposure of the skeletal fibers, and disruption of the choanocyte chambers. To ascertain the role of microbes in the disease process, a comprehensive comparison of bacteria, viruses, fungi, and other eukaryotes was performed in healthy and diseased sponges using multiple techniques. A low diversity of microbes was observed in both healthy and diseased sponge communities, with all sponges dominated by an Alphaproteobacteria, a Gammaproteobacteria, and a group I crenarchaeota. Bacterial cultivation, community analysis by denaturing gradient gel electrophoresis (Bacteria and Eukarya), sequencing of 16S rRNA clone libraries (Bacteria and Archaea), and direct visual assessment by electron microscopy failed to reveal any putative pathogens. In addition, infection assays could not establish the syndrome in healthy sponges even after direct physical contact with affected tissue. These results suggest that microbes are not responsible for the formation of brown spot lesions and necrosis in I. basta.

MicrobiologyOpen, 2014

Microbial source tracking is an area of research in which multiple approaches are used to identif... more Microbial source tracking is an area of research in which multiple approaches are used to identify the sources of elevated bacterial concentrations in recreational lakes and beaches. At our study location in Darwin, northern Australia, water quality in the harbor is generally good, however dry-season beach closures due to elevated Escherichia coli and enterococci counts are a cause for concern. The sources of these high bacteria counts are currently unknown. To address this, we sampled sewage outfalls, other potential inputs, such as urban rivers and drains, and surrounding beaches, and used genetic fingerprints from E. coli and enterococci communities, fecal markers and 454 pyrosequencing to track contamination sources. A sewage effluent outfall (Larrakeyah discharge) was a source of bacteria, including fecal bacteria that impacted nearby beaches. Two other treated effluent discharges did not appear to influence sites other than those directly adjacent. Several beaches contained fecal indicator bacteria that likely originated from urban rivers and creeks within the catchment. Generally, connectivity between the sites was observed within distinct geographical locations and it appeared that most of the bacterial contamination on Darwin beaches was confined to local sources.

Marine Biology Research, 2007

Secondary metabolites from marine invertebrates, such as sponges, have diverse ecological roles a... more Secondary metabolites from marine invertebrates, such as sponges, have diverse ecological roles and may be used in antipredation, anti-fouling and spatial competition. The thin encrusting sponge Iotrochota sp., found on the Great Barrier Reef, Australia, contains several novel indoles that may aid in spatial competition. To examine whether levels of surrounding competition affect the toxicity of Iotrochota sp., 24 sponges from Salamander Reef, Central Great Barrier Reef, subject to either high or low levels of surrounding competition, were sampled. Tissue samples were taken from areas where the sponge was in direct competition with neighbouring sessile invertebrates, as well as from areas where competition was less obvious. Compounds from the tissue samples were extracted and tested in both cytotoxicity and anti-microbial assays. However, neither cytotoxicity nor anti-microbial activity varied significantly between the high and low competition treatments. Cytotoxicity was greatest among large sponges, suggesting that size is an important factor contributing to the toxicity of Iotrochota sp. sponges in this study.

Prevalence of tissue necrosis and brown spot lesions in a common marine sponge

Marine and Freshwater Research, 2010

Page 1. Prevalence of tissue necrosis and brown spot lesions in a common marine sponge Heidi M. L... more Page 1. Prevalence of tissue necrosis and brown spot lesions in a common marine sponge Heidi M. Luter A,B,C,D , Steve Whalan B and Nicole S. Webster B ... We also thank C. Wolff, L. Evans-Illidge, K. Johns and J. Morris for diving and fieldwork. ...

Applied and environmental …, 2010

A disease-like syndrome is currently affecting a large percentage of the Ianthella basta populati... more A disease-like syndrome is currently affecting a large percentage of the Ianthella basta populations from the Great Barrier Reef and central Torres Strait. Symptoms of the syndrome include discolored, necrotic spots leading to tissue degradation, exposure of the skeletal fibers, and disruption of the choanocyte chambers. To ascertain the role of microbes in the disease process, a comprehensive comparison of bacteria, viruses, fungi, and other eukaryotes was performed in healthy and diseased sponges using multiple techniques. A low diversity of microbes was observed in both healthy and diseased sponge communities, with all sponges dominated by an Alphaproteobacteria, a Gammaproteobacteria, and a group I crenarchaeota. Bacterial cultivation, community analysis by denaturing gradient gel electrophoresis (Bacteria and Eukarya), sequencing of 16S rRNA clone libraries (Bacteria and Archaea), and direct visual assessment by electron microscopy failed to reveal any putative pathogens. In addition, infection assays could not establish the syndrome in healthy sponges even after direct physical contact with affected tissue. These results suggest that microbes are not responsible for the formation of brown spot lesions and necrosis in I. basta.

Symbioses in marine sponges involve diverse consortia of microorganisms that contribute to the he... more Symbioses in marine sponges involve diverse consortia of microorganisms that contribute to the health and ecology of their hosts. The microbial communities of 13 taxonomically diverse Great Barrier Reef (GBR) sponge species were assessed by DGGE and 16S rRNA gene sequencing to determine intra and inter species variation in bacterial symbiont composition. Microbial profiling revealed communities that were largely conserved within different individuals of each species with intra species similarity ranging from 65-100%. 16S rRNA gene sequencing revealed that the communities were dominated by Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, Nitrospira, and Cyanobacteria. Sponge-associated microbes were also highly host-specific with no operational taxonomic units (OTUs) common to all species and the most ubiquitous OTU found in only 5 of the 13 sponge species. In total, 91% of the OTUs were restricted to a single sponge species. However, GBR sponge microbes were more closely related to other sponge-derived bacteria than they were to environmental communities with sequences falling within 50 of the 173 previously defined sponge-(or sponge-coral) specific sequence clusters (SC). These SC spanned the Acidobacteria, Actinobacteria, Proteobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Gemmatimonadetes, Nitrospira, and the Planctomycetes-Verrucomicrobia-Chlamydiae superphylum. The number of sequences assigned to these sponge-specific clusters across all species ranged from 0 to 92%. No relationship between host phylogeny and symbiont communities were observed across the different sponge orders, although the highest level of similarity was detected in two closely related Xestospongia species. This study identifies the core microbial inhabitants in a range of GBR sponges thereby providing the basis for future studies on sponge symbiotic function and research aiming to predict how sponge holobionts will respond to environmental perturbation.

Sponges often exhibit tissue regression in response to stressful conditions. This study investiga... more Sponges often exhibit tissue regression in response to stressful conditions. This study investigated whether handling stress invoked tissue regression in Ianthella basta and assessed whether sponges could recover from this regressed tissue state. Six necrotic specimens and 12 healthy explants were collected at Orpheus Is. Australia and transported to aquarium facilities. Sponges were photographed daily and an integrated density (ID) measurement was used to quantify tissue regression. Histological samples were taken from sponge explants to compare cellular organization. Bacterial communities of regressed and recovered tissue were compared using Denaturing Gradient Gel Electrophoresis (DGGE). After 12 h both necrotic and healthy sponges displayed substantial tissue regression. However, within 72 h all sponges recovered to their original condition. The ID of the sponge tissue doubled, confirming tissue recovery in I. basta. Sponges affected by tissue regression had significantly fewer choanocyte chambers and more densely packed granulated cells than recovered sponges. DGGE revealed the same microbial symbionts in both regressed and recovered sponges. Handling stress associated with collection and transportation is sufficient to invoke tissue regression in this species, but sponges can rapidly recover. This study contributes to our understanding of how sponges respond to environmental pressures, influencing population resilience and persistence.

Morphological delineation of sponge species is hindered by the narrow range of fixed diagnostic c... more Morphological delineation of sponge species is hindered by the narrow range of fixed diagnostic characters and our limited knowledge of how much phenotypic plasticity the sponge body plan assumes in response to environmental conditions. Here, we make use of the partial mitochondrial cytochrome c oxidase subunit I (COI) gene and the second internal transcribed spacer (ITS2) region to assess the taxonomic validity of colour morphotypes observed in the elephant ear sponge Ianthella basta (Pallas, 1776) across its distribution range in northern Australia, and explore levels and patterns of genetic diversity among populations of the species collected from both sides of the Torres Strait. Molecular phylogenetic analyses revealed congruent topologies consistent with three evolutionarily significant units (ESUs) that were independent of the morphology of the sponge. ESU I includes previously morphologically and genetically delineated western Pacific specimens of I. basta (Guam), and probably corresponds to the type specimen originally described from Indonesia. ESU I occurs in almost all sampling sites across northern Australia, suggesting considerable levels of connectivity among reefs throughout the Torres Strait. ESUs II and III are each exclusively associated with a geographic region of high sponge species richness separated by Torres Strait, and probably represent the result of historical population fragmentation.

Natural populations of marine invertebrates often exhibit measureable morphologic variation resul... more Natural populations of marine invertebrates often exhibit measureable morphologic variation resulting in taxonomic confusion. This potentially has severe consequences for experimental design and data management. Species of the sponge genus Ianthella embody a number of different morphologies and a diverse range of secondary metabolites. Among them, Ianthella basta (Pallas, 1776), a common sponge in Papua New Guinea and the Great Barrier Reef (GBR), exhibits two dominant colour morphotypes: yellow and purple. Specimens collected from Orpheus Island on the GBR were investigated using phylogenetic (CO1, ITS-2 sequence analysis), chemical (mass spectrometry) and microbial (DGGE and 16S rRNA clone library) techniques in an effort to fully characterise the two colour morphs. Phylogenetic analyses indicated sharp genetic discontinuities within I. basta sensu lato independent of colour variation. The two morphotypes did, however, correspond to distinct DGGE profiles largely due to the presence of additional bands in the purple morpho-group. Further comparison of the microbial communities by 16S rRNA gene sequencing revealed that whilst both colour morphs were dominated by only two bacterial symbionts (residing within the Gamma and Alphaproteobacteria), the purple morph also contained minor representatives of the Cyanobacteria, Chloroflexi and Verrucomicrobia. Untargeted metabolic profiling by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) indicated two distinct clusters corresponding to the different sponge colours. A clear association was found between the araplysillin class of compounds and the purple morphotype of I. basta, indicating the utility of a metabolomic approach to assess differences between colour morphs. These results have important implications for ecological investigations in sponges and other invertebrate taxa whose morphology is fundamentally dynamic, stressing the need for precise taxonomic, chemical and microbial descriptions.

Background: Marine diseases are being increasingly linked to anthropogenic factors including glob... more Background: Marine diseases are being increasingly linked to anthropogenic factors including global and local stressors. On the Great Barrier Reef, up to 66% of the Ianthella basta population was recently found to be afflicted by a syndrome characterized by brown spot lesions and necrotic tissue.

MicrobiologyOpen, 2014

Microbial source tracking is an area of research in which multiple approaches are used to identif... more Microbial source tracking is an area of research in which multiple approaches are used to identify the sources of elevated bacterial concentrations in recreational lakes and beaches. At our study location in Darwin, northern Australia, water quality in the harbor is generally good, however dry-season beach closures due to elevated Escherichia coli and enterococci counts are a cause for concern. The sources of these high bacteria counts are currently unknown. To address this, we sampled sewage outfalls, other potential inputs, such as urban rivers and drains, and surrounding beaches, and used genetic fingerprints from E. coli and enterococci communities, fecal markers and 454 pyrosequencing to track contamination sources. A sewage effluent outfall (Larrakeyah discharge) was a source of bacteria, including fecal bacteria that impacted nearby beaches. Two other treated effluent discharges did not appear to influence sites other than those directly adjacent. Several beaches contained fecal indicator bacteria that likely originated from urban rivers and creeks within the catchment. Generally, connectivity between the sites was observed within distinct geographical locations and it appeared that most of the bacterial contamination on Darwin beaches was confined to local sources.

MicrobiologyOpen, 2014

Microbial source tracking is an area of research in which multiple approaches are used to identif... more Microbial source tracking is an area of research in which multiple approaches are used to identify the sources of elevated bacterial concentrations in recreational lakes and beaches. At our study location in Darwin, northern Australia, water quality in the harbor is generally good, however dry-season beach closures due to elevated Escherichia coli and enterococci counts are a cause for concern. The sources of these high bacteria counts are currently unknown. To address this, we sampled sewage outfalls, other potential inputs, such as urban rivers and drains, and surrounding beaches, and used genetic fingerprints from E. coli and enterococci communities, fecal markers and 454 pyrosequencing to track contamination sources. A sewage effluent outfall (Larrakeyah discharge) was a source of bacteria, including fecal bacteria that impacted nearby beaches. Two other treated effluent discharges did not appear to influence sites other than those directly adjacent. Several beaches contained fecal indicator bacteria that likely originated from urban rivers and creeks within the catchment. Generally, connectivity between the sites was observed within distinct geographical locations and it appeared that most of the bacterial contamination on Darwin beaches was confined to local sources.