Algal Taxa Research Articles

Phenotypic Comparability from Genotypic Variability among Physically Structured Microbial Consortia.

Microbiomes represent the collective bacteria, archaea, protist, fungi, and virus communities living in or on individual organisms that are typically multicellular eukaryotes. Such consortia have become recognized as having significant impacts on the development, health, and disease status of their hosts. Since understanding the mechanistic connections between an individual's genetic makeup and their complete set of traits (i.e., genome to phenome) requires consideration at different levels of biological organization, this should include interactions with, and the organization of, microbial consortia. To understand microbial consortia organization, we elucidated the genetic constituents among phenotypically similar (and hypothesized functionally-analogous) layers (i.e., top orange, second orange, pink, and green layers) in the unique laminated orange cyanobacterial-bacterial crusts endemic to Hawaii's anchialine ecosystem. High-throughput amplicon sequencing of ribosomal RNA hypervariable regions (i.e., Bacteria-specific V6 and Eukarya-biased V9) revealed microbial richness increasing by crust layer depth, with samples of a given layer more similar to different layers from the same geographic site than to their phenotypically-analogous layer from different sites. Furthermore, samples from sites on the same island were more similar to each other, regardless of which layer they originated from, than to analogous layers from another island. However, cyanobacterial and algal taxa were abundant in all surface and bottom layers, with anaerobic and chemoautotrophic taxa concentrated in the middle two layers, suggesting crust oxygenation from both above and below. Thus, the arrangement of oxygenated vs. anoxygenated niches in these orange crusts is functionally distinct relative to other laminated cyanobacterial-bacterial communities examined to date, with convergent evolution due to similar environmental conditions a likely driver for these phenotypically comparable but genetically distinct microbial consortia.

<p><strong>An updated checklist of algae from the Tatra Mountain lakes (Slovakia)—based on field research from 2010/12</strong></p>

Checklists of any confined locality are very pertinent not only to academic researchers, but also to the policy makers in formulating biodiversity conservation strategies. The Tatra Mountains are the highest mountain peaks of the Carpathian Mountain range, located at the border between Slovakia and Poland, certified by UNESCO as a MAB Biosphere Reserve. More than 100 lakes of various sizes and depths are present in the valleys of this mountainous terrain, which were under severe acidification till late 1980s and recovered during 2000 after control of air pollution. For many years these lakes have witnessed several floristic and ecological studies. But, to facilitate the research, the available baseline information of algal floristics was of 25 years old. Thus, the present inventory was intented to update the existing information. It comprises of 557 cyanobacterial and algal taxa belonging to 228 genera and 95 families of the phyla Cyanobacteria, Stramenopiles, Alveolata, Cryptophyta, Chlorophyta, Charophyta and Euglenophyta. In the checklist, Forty-nine taxa (8.79%) are significantly updated to the existing records from the surveys made during 2010/12 in the present work and some recently published records.

Extraction of high-quality, high-molecular-weight DNA depends heavily on cell homogenization methods in green microalgae.

PremiseNew sequencing technologies have facilitated genomic studies in green microalgae; however, extracting high‐quality DNA is often a bottleneck for long‐read sequencing.Methods and ResultsHere, we present a low‐cost, highly transferrable method for the extraction of high‐molecular‐weight (HMW), high‐purity DNA from microalgae. We first determined the effect of sample preparation on DNA quality using three homogenization methods: manual grinding using a mini‐pestle, automatic grinding using a vortex adapter, and grinding in liquid nitrogen. We demonstrated the versatility of grinding in liquid nitrogen followed by a modified cetyltrimethylammonium bromide (CTAB) extraction across a suite of aquatic‐ and desert‐evolved algal taxa. Finally, we tested the protocol's robustness by doubling the input material to increase yield, producing per sample up to 20 μg of high‐purity DNA longer than 21.2 kbp.ConclusionsAll homogenization methods produced DNA within acceptable parameters for purity, but only liquid nitrogen grinding resulted in HMW DNA. The optimization of cell lysis while minimizing DNA shearing is therefore crucial for the isolation of DNA for long‐read genomic sequencing because template DNA length strongly affects read output and length.

Soil algae and cyanobacteria of Moscow State University educational-scientific station «Satino»

The species composition of soil algae and cyanobacteria in landscapes with different types of land use was studied for the first time on the territory of the Lomonosov Moscow state University educational and scientific station (Kaluga region). 125 species and intraspecific taxa of algae and 35 species of cyanobacteria were found. The specificity of algal-cyanobacterial communities in soils under different types of forest, in clearings of different ages and on arable land was revealed. In a field experiment, the effect of hydrocarbon fuel contamination (gasoline, kerosene, and diesel fuel) on the algal-cyanobacterial communities of sod-podzolic soils was studied. It is shown that with the same primary load of pollutants, their toxicity to algae and cyanobacteria and the rate of recovery of algal-cyanobacterial communities depends on the type of land use of the territory, and with the same type of land use – on the water regime of soils. In the same soil, the specific of the pollutant also affects the recovery of algal-cyanobacterial communities. Data on the composition of algae and cyanobacteria successfully complement information about the biological activity of soils obtained by other methods.

Structural and functional characteristics of algal flora in water bodies of the natural monuments in Orenburg forest steppe Trans Volga region (Russia)

The algal flora of 7 water bodies of Orenburg forest-steppe Trans Volga region protected areas was studied. 193 species and intraspecific taxa of algae belonging to 7 phyla, 12 classes, 30 orders, 57 families and 109 genera were identified. According to the results of a saprobiological analysis studied water bodies and streams are characterized as xeno-, oligo-, and β-mesosaprobic, grades 1-3 of quality, from extremely pure to satisfactory purity. In some water bodies (pond on the Zhmakovsky creek – natural monument «Kuzminka creek with tributaries^ and pond of the natural monument «Aksakov’s park»), disturbances in the stability of ecosystems and various stages of eutrophication were recorded. The data obtained indicate the need for strict compliance with the restrictions already provided for these natural monuments and the use of more effective protection measures to restore ecosystems and improve water quality within the studied objects.

Morphological and Molecular Taxonomic studies of Edaphic Cyanobacteria from Siwa Oasis, Egypt”

Abstract Up to now, edaphic or soil algae of Siwa Oasis have never been demonstrated before. Soil samples of the investigated four regions of Siwa Oasis were cultured on Chu No.10 nutritive medium. Overall, 19 soil algal taxa were detected throughout the areas of study. These were assigned to four systematic algal divisions, of which 10 Cyanophyta taxa followed by 6 Chlorophyta taxa, 2 Xanthophyta taxa and one Euglenophyta taxon. The heterocystous, nitrogen- fixing taxa were demonstrated in considerable numbers (seven/ ten cyanophytes). At time of isolation (12 days-exponential phase), the pure fresh uni-algal cultures of Amorphonostoc paludosum Kossinsk, Aphanizomenon elenkinii Kisselev and Anabaena naviculoides Hollerb (isolated from Siwa Oasis) were selected to study their taxonomical (successive growth stages) and molecular characters. Current molecular study showed that, the used scot polymorphism resolves the problematic taxonomy of Anabaena and Aphanizomenon genera. The recorded morphological and life cycle data (that daily based on microscopic examination to the successive growth stages of the studied three nostocales species) were support the genetic results and indicated that, Anabaena and Aphanizomenon significantly different. Fresh isolated cultured Amorphonostoc and Anabaena genera are traditionally separated based on morphological characteristics and life cycle differences. Therefore, combining of taxonomical, life cycle and molecular evidences for the fresh cultured genera proved to be reliable and successful approaches for the analyses of cyanophytes polymorphisms.

Does biofilm origin matter? Biofilm responses to non‐flow period in permanent and temporary streams

Abstract In some regions, climate change is increasing the variability of rainfall and the frequency of extreme events such as drought. Consequently, non‐flow periods have grown in length and frequency, both in temporary and in formerly permanent streams. Water abstraction for human use may further prolong these dry periods. We analysed the resistance and resilience of biofilms from permanent and temporary streams to non‐flow conditions. This was achieved by exposing cobbles (collected from permanent and temporary streams) with intact biofilm to 31 days of non‐flow, followed by 20 days of stream flow in artificial stream channels. Biofilm resistance and resilience were assessed at a structural (algal biomass, pigment composition, and algae and cyanobacteria composition) and functional level (photosynthetic efficiency and community metabolism). Algal taxa in biofilms from permanent and temporary streams differed throughout the experiment. Biofilms from permanent streams were less resistant to non‐flow than those from temporary streams at structural level. Permanent stream biofilms also presented lower resilience at a structural level, but responded similarly to temporary stream biofilms at a functional level. Our investigation shows how the non‐flow period disturbed permanent stream biofilms, and suggests that temporary stream biofilms will have greater adaptive capacity as hydroperiod becomes shorter due to climate change.

Phytoplankton of the Usa River and Its Tributaries (Kuibyshev Reservoir Basin)

Abstract—Data on the status of summer phytoplankton of the Usa River and its tributaries are given. In total 184 taxa of algae with a rank lower than the genus from eight divisions were recorded in algal flora, with Bacillariophyta (43–57% of the composition) and Chlorophyta (23–47%) predominating in the rivers. The abundance range in algocenoses was 0.02–5.2 million cells/L; of biomass, 0.01–1.8 mg/L; the content of chlorophyll-a, was 0.01–3.1 μg/L. The ecological heterogeneity along the watercourse causes significant dynamics in the taxonomic composition, which is characterized by mosaic distribution in different areas, and changes in the quantitative structure of plankton communities. An increase in the species diversity, abundance, biomass, and chlorophyll-a concentration from the source to the mouth of rivers is noted. The ecotone effect in the zone of mixing and transformation of the waters of the lower reaches of the watercourses and Usinskii Bay of the Kuibyshev Reservoir is expressed in an increase in the diversity and amount of algae, an increase in the coenotic role of Cyanoprokaryota and planktonic green algae of the Chlorococcales order, which are dominant in Usinskii Bay. The influence of hydrological conditions, the content of nutrients, and the anthropogenic impact on the formation of algocenoses is discussed. The taxonomic composition, distribution, structural characteristics of algocenoses in the absence of nutrient limiting depend on hydrological factors, and biotopic heterogeneity of natural and anthropogenic origin have been studied, whereas their relation to the content of nutrients in eutrophic conditions has not been revealed. The Shannon species diversity index varied from 0.5 to 2.7 bits/specimen in the river algocenoses. The minimum values were noted on the upstream sections of the rivers; the complexity of the structure is typical for the algocenoses of the mixing zones of the waters of the upper part of Usinskii Bay and the mouths of the Muranka and Tisherek rivers, as well as for the communities of the sections of rivers with anthropogenic impact.

Biofilm pads—an easy method to manufacture artificial biofilms embedded in an alginate polymer matrix

AbstractPeriphytic biofilms are the major resource for many herbivorous invertebrates in both marine and freshwater benthos. They are of crucial importance for benthic food webs, substrate stability, and biogeochemical processes in littoral zones. While the importance of invertebrate grazing on biofilms has been studied extensively using natural, mixed algal communities grown on artificial substrates, there is so far no method available to create defined periphyton communities for these grazing studies. The reason for this is that many benthic algae interact with co‐occurring species within the extracellular polymeric substances (EPSs) that form the nonorganismic part of the biofilm. Here, we present a novel method that allows the manufacturing of defined monoculture and multispecies biofilms by using an alginate polymer as artificial EPS structure, into which algal cultures can be embedded. Using confocal laser scanning microscopy, we show that alginate effectively embeds various algal taxa in an EPS matrix that is very similar to natural biofilms. In a grazing experiment, we demonstrate that several common freshwater herbivorous invertebrates can graze these alginate biofilms efficiently. As the method is easy to handle, it allows for highly controlled feeding experiments with benthic herbivores to assess, for example, the role of algal biodiversity on the efficiency of top‐down control, the effects of environmental drivers such as nutrients, salinity, or seawater acidification on biofilm community structure, and the impacts of herbivory in benthic communities.

<p><strong>Morphological and molecular investigation of freshwater <em>Hildenbrandia</em> (Hildenbrandiales, Rhodophyta) with a new species reported from Japan</strong></p>

The morphological characterization and phylogenetic analysis based on molecular methods were executed on the freshwater Hildenbrandia specimens collected in this study. The cell size and filament height of the specimen collected from Pipa Lake, Japan were larger than the widely recognized species Hildenbrandia angolensis and Hildenbrandia rivularis, whereas overlapped with Hildenbrandia jigongshanensis. Based on molecular evidences of rbcL phylogenetic analysis and comparison of ITS1 secondary structure, specimen collected from Shiga Prefecture, Japan was proposed as a new species Hildenbrandia japananense. It brings the freshwater Hildenbrandia species in Japan to two. The specimens collected from Niangziguan, Shanxi province, China represent two new records of H. jigongshanensis. It enriches the species diversity of genus Hildenbrandia and increases the distribution diversity of this freshwater red algal taxon.

Dividing the algal soup: is there niche separation between native bivalves (Echyridella menziesii) and non-native Daphnia pulex in New Zealand?

ABSTRACTNew Zealand's native freshwater mussels (kākahi, kāeo) are considered to be in decline, yet the mechanisms driving this are unclear. The widespread establishment of highly efficient filter-feeding, non-native Daphnia in New Zealand lakes may have led to competition for algae with kākahi. We conducted a controlled laboratory experiment to determine whether differences exist in algal resources utilised by kākahi and North American Daphnia pulex. Echyridella menziesii (adults and juveniles) and D. pulex were exposed to mixed algal samples for three hours to determine whether similar algal resources were removed by the grazers. Relative to controls, both adult and juvenile E. menziesii removed a broad range of algal taxa including diatoms, green algae and filamentous species, ranging in size from 33.6 to 348.0 μm. High densities of D. pulex were unable to cause depletion of these same algae species. Our results suggest niche overlap is limited between the two grazers; E. menziesii utilises larger particles than D. pulex.

Genome and cell size variation across algal taxa

Genome and cell size variation across algal taxa

The Potentiality of Marine Macro-Algae as Bio-Fertilizers to Improve the Productivity and Salt Stress Tolerance of Canola (Brassica napus L.) Plants

The present study aimed to evaluate the potentiality of three seaweeds, which belong to different algal taxa (green alga Ulva lactuca Linnaeus, brown alga Cystoseira spp., and red alga Gelidium crinale (Hare ex Turner) Gaillon) as bio-fertilizers to improve the growth and yield of canola (Brassica napus L.) plants under greenhouse conditions. Furthermore, the impact of seaweeds in alleviating the effects of salt stress (75 and 150 mM NaCl) on canola plants was also investigated. The three examined seaweeds (applied as soil amendments) successfully alleviated the harmful effects of salinity on canola plants by significantly reducing the inhibition of chlorophyll a, b, total carbohydrate accumulation, and growth promoting hormones, while increasing antioxidative compounds, such as phenols, flavonoids, anthocyanin, and osmoprotectants, including total carbohydrates and proline. Phytochemical analysis of the three examined seaweeds suggests that their stimulatory effect on growth and productivity under normal and salinity growth conditions may be linked to their constituents of a wide variety of growth promotive hormones, including indole acetic acid, indole butyric acid, gibberellic acid, cytokinins, total carbohydrates, and phenolic compounds. U. lactuca was found to be the best candidate to be used as a bio-fertilizer to improve canola growth, yield, and salt stress tolerance.

Variations in Phototroph Communities on the Ablating Bare-Ice Surface of Glaciers on Brøggerhalvøya, Svalbard

During the summer ablation season, Arctic glacier surfaces host a wealth of microbial life. Here, the phototroph communities on the ablating bare-ice surface of three valley glaciers on Broggerhalvoya, Svalbard were investigated. The communities mainly comprised seven taxa of green algae and cyanobacteria, which have been commonly reported on Arctic glaciers. Although the geographical and glaciological settings of the three studied glaciers are similar, there were differences in total phototroph biomass. The community structure was also distinctive among the glaciers: high dominance of a single taxon of green algae (Ancylonema nordenskioldii) for Midtre Lovenbreen, abundant cyanobacteria for Austre Broggerbreen, and diverse green algae for Pedersenbreen. The major soluble ions in the surface ice showed that there was no significant difference in meltwater nutrient conditions between the glaciers, but there were lower concentrations of mineral-derived ions on Midtre Lovenbreen. Consequently, the glacier-specific mineral loading and surface hydrology are inferred to explain the contrast in bare ice algal communities between the glaciers. We hypothesise that local, glacier-specific conditions affect algal communities and the associated influences on carbon cycling and ice-surface albedo.

Molecular Characterization of Mercury Binding Ligands Released by Freshwater Algae Grown at Three Photoperiods

Interactions between algal derived dissolved organic matter (DOM) and mercury (Hg) are crucial for understanding the fate, transport, and bioavailability of Hg to methylating microorganisms. For the first time, high resolution mass spectrometry (Q-Exactive Orbitrap) was used to examine Hg binding ligands released by Chlorella vulgaris, Chlamydomonas reinhardtii, and Scenedesmus obliquus grown at three light:dark photoperiods (i.e. 12:12, 16:8 and 20:4 h). van Krevelen diagrams showed a significant increase in carbohydrate and protein DOM and a decrease in released lipid-like molecules as light exposure increased. Hg binding DOM were initially in the form of CHO molecular formulas whereas a shift to higher light durations prompted more Hg to be complexed to CHON and CHONS DOM structures. Despite an overall change in bulk DOM composition, molecular similarities existed in Hg binding DOM as light exposure increased. Hg binding ligands were more similar based on the exposed light duration than based algal species, suggesting growth photoperiods influence Hg binding more than algal taxa. Hg binding DOM at 16:8 and 20:4 h growth cycles were more aromatic and homologous in nature when compared to darker growth conditions that resulted in smaller, more aliphatic Hg-DOM complexes rich in sulphur and thiols. Together, these results highlight the importance of photoperiod on the composition of released DOM and its complexation with Hg.

Cyanobacterial and algal abundance and biomass in cave biofilms and relation to environmental and biofilm parameters

Due to life in extreme environments, cyanobacteria and algae from cave biofilms that form at the entrances or deep inside the cave around artificial lights are of increasing interest to many scientists. It is well-known that many phototrophic microorganisms are first to colonize exposed substrata and produce the organic matter on which other biofilm constituents relly. Many studies dealing with phototrophic microorganisms from biofilms focus on the diversity and community composition of cyanobacteria and algae, while quantitative assessments are rarely implemented. Biofilm sampling was conducted in Degurić and Vernjikica Cave located in Western and Eastern Serbia, respectively. Ecological parameters (temperature, relative humidity, light intensity) and distance from the entrance were measured. Additionally, chlorophyll content, as well as biofilm parameters (water content, organic and inorganic matter) were determined. The abundance of phototrophic microorganisms was assessed on microscope slides which contained 1 mg of biofilm that was dehydrated for a short period of time and homogenized prior to slide preparation, and then rehydratated. The biomass of recorded cyanobacterial and algal taxa was calculated by applying geometric approximations and standard mathematical formulas. In Degurić Cave, at the sampling site where the highest biomass was documented, the higher diversity, water content and chlorophyll values were also recorded, while in Vernjikica Cave a high content of organic matter was documented. According to the multivariate analyses performed, the biomass of simple trichal Cyanobacteria, Bacillariophyta, and Xanthophyta was positively correlated with the content of organic matter in biofilm and light intensity, while coccoid and heterocytous Cyanobacteria and Chlorophyta showed a positive correlation with water content in the biofilm, relative humidity and distance from the entrance. The total biomass was positively correlated with the chlorophyll content, organic matter and light intensity, and negatively with the distance from the entrance.

Chrysochromulina: Genomic assessment and taxonomic diagnosis of the type species for an oleaginous algal clade

BackgroundUntil recent studies documented their extensive contribution to primary productivity and carbon sequestration, haptophytes remained underappreciated players in global ecosystem processes. Contemporary analyses, augmented by the use of molecular probes, show the haptophyte taxon Chrysochromulina to be seminal to the ecology of both marine and freshwater ecosystems. Unfortunately, description for the type species for this clade remains enigmatic. ResultsChrysochromulina parva Lackey was re-isolated from Big Walnut Creek (Ohio), the site where the original isolate was obtained. The sequenced haploid genome of this organism is 65.7 Mb in size. Several noteworthy nuclear-encoded genes identified include a novel ftsZ (mediates organelle division) that phylogenetically clusters with the Chloroarachniophytes. Also revealed, is a complement of genes associated with meiosis and DNA repair, indicating the presence of a sexual cycle in this alga. Mitochondrial genes lost to the nucleus include all extrinsic components of the nad complex, completing a punctate pattern of transfer that is observed among algal taxa. Comparison of the newly sequenced Chrysochromulina parva Lacky isolate was made with that of Chrysochromulina tobinii (59.1 Mb) – a fresh water strain isolated from a lake in Colorado. ConclusionGenomic analysis suggests that fresh water Chrysochromulina isolates, though geographically well separated, from a related clade. The name of the type species of Chrysochromulina parva Lacky is anchored with a lectotype and epitype, and the second isolate is described as Chrysochromulina tobinii sp. nov. Chrysochromulina represents a new, extremely tractable model organism for experimental studies. This oleaginous alga has a small genome and because it represents only the second haptophyte taxon to be sequenced and assembled, presents new opportunity to examine the evolution of an algal taxon that plays an intrinsic role in ecosystem function.

Algal Diversity in Baraila Lake Salim Ali Jubba Sahni Bird Sanctuary, Bihar (India)

This communication presents studies of algal diversity sampled from Baraila lake Salim Ali Jubba Sahni Bird Sanctuary, a protected area located in Vaishali district of Bihar. It is the first time that wetlands of Bihar are explored for asscessing of the algal diversity. A total of 36 algal taxa belonging to 27 genera and 9 classes were identified and documented. Out of these, 4 taxa are recorded as new distributional records for India, i.e. Sphaerellocystis ellipsoidea Ettl, Oedogonium pratense Transeau f. minus Mrozi?ska-Webb, Oedogonium undulatum A. Braun ex Hirn var. incisum Hansgirg and Chara muscosa J. Groves & Boll.-Webst.

Macroalgal resource use differences across age and size classes in the dominant temperate herbivorous fish Aplodactylus lophodon (Aplodactylidae)

Herbivorous fishes comprise a substantial proportion of temperate fish communities, although there is little understanding of their trophic resource use and whether this changes throughout post-settlement ontogeny. With increasing loss of macroalgal forests, understanding how temperate fishes use macroalgae will be vital in predicting future effects on temperate fish biodiversity. The Australian rock cale (Aplodactylus lophodon) is one of the most abundant herbivorous fish inhabiting shallow temperate south-eastern Australian reefs. We examined gastrointestinal contents throughout ontogeny and demonstrated that this species maintains a herbivorous diet through all life stages. Differences in algal taxa consumed were apparent through ontogeny, with the juvenile diet dominated by filamentous red and green algae and the adult diet dominated by brown and calcareous red algae. Relative gut length increased through ontogeny, potentially facilitating dietary transition to less digestible algae, but no concurrent increase in jaw power was observed. The results highlight the diversity of trophic resource use in a temperate marine herbivore, but the near-complete dominance of dietary algae throughout ontogeny indicates the reliance on primary producers across all life stages. Given the importance of fucoid resources in the adult diet, any loss of macroalgal forests within south-eastern Australia may affect foraging success and persistence.

Host Differentiation and Compartmentalization of Microbial Communities in the Azooxanthellate Cupcorals Tubastrea coccinea and Rhizopsammia goesi in the Caribbean

We investigated the microbial communities associated with surface layer mucus, tissue and gastrovascular cavity of two azooxanthellate Caribbean cup corals (Tubastrea coccinea and Rhizopsammia goesi) to explore potential differences in microbial community composition within and among these azooxanthellate scleractinian corals. Using next-generation sequencing of the V3-V6 region of the 16S rRNA gene we found that while alpha-diversity was overall very similar, the relative abundance of microbial taxa differed between host species and among locations within a polyp (i.e., compartments). The distinct microbial assemblages between species is only challenged by the relatively high similarity among mucus samples of both species. This suggests a stronger signal of the surrounding environment and weaker host control over the mucus compartment compared with the tissue and gastrovascular cavity. Tubastrea coccinea harboured four indicator OTUs (including a Pseudoalteromonas species, an unidentified Gammaproteobacteria, an unidentified OTU in the family Comamonadaceae and one in the genus Burkholderia). The single indicator for R. goesi was another undetermined OTU in the Comamonadaceae. The microbial communities of the gastrovascular cavity and the mucus overlapped substantially in indicator OTUs. None of these were exclusive of the gastrovascular cavity or mucus, while an OTU of the order Thiohalorhabdales occurred uniquely in the tissue. In contrast to the gastrovascular cavity and mucus, the tissue of both coral species was rich in chloroplasts of different algal taxa (mainly Ulvophyceae and Stramenopiles), and an OTU of the genus Roseivirga (family Flammeovirgaceae). The two coral species shared most indicator OTUs for microbial communities residing in their mucus and tissue, but not in their gastrovascular cavities. However, Endozoicomonadaceae occurred in the tissue of both coral species. The genus Pseudomonas was found in R. goesi but was virtually absent in T. coccinea. This study demonstrates the influence of coral compartments and species identities on the composition of microbial communities associated with azooxanthellate cup corals and emphasizes the important effects of within-polyp microhabitats in structuring the coral microbiome.