The role of the seagrass leaf microbiome in assisting nitrogen uptake by the Western Australian seagrass, Posidonia sinuosa

Microorganisms play a key role in facilitating the cycling of several elements in coastal environments, including nitrogen (N). N is a key component for maintaining high seagrass productivity and is often the limiting nutrient in marine environments. Seagrasses harbour an abundant and diverse microbial community (the ‘microbiome’), however their ecological and functional roles related to the seagrass host are still poorly understood, in particular regarding N cycling. Microorganisms capable of mineralising dissolved organic nitrogen (DON) may play a pivotal role in enhancing N availability in coastal environments such as seagrass meadows. Thus, the overall aim of my thesis was to enhance current understanding of abundance and diversity of the microbial community associated with seagrass meadows and their ecological role, with specific focus on N cycling. This was achieved by using molecular techniques together with 15N-enrichment experiments and nanoscale imaging techniques. Firstly, I reviewed the literature on the potential effects that microorganisms associated with both the above- and belowground seagrass tissue may have on plant fitness and the relevance of the seagrass microbiome and I have highlighted literature gaps. For my second chapter, I determined the abundance and community composition of bacteria and archaea associated with seagrass Posidonia sinuosa meadows in Marmion Marine Park, southwestern Australia. Data were collected from different seagrass meadows and meadow ‘microenvironments’, i.e. seagrass leaf surface, sediment and water column. I performed the quantitative polymerase chain reaction (q-PCR) targeting a series of bacterial and archaeal genes: 16S rRNA, ammonia oxidation genes (amoA) and genes involved in mineralisation of DON, via the urease enzyme (ureC). High-throughput sequencing was applied to 16S rRNA and amoA genes, to explore the diversity of these microbial assemblages related to P. sinuosa meadow microenvironments. Results from this chapter show that the P. sinuosa leaf biofilm represents a favourable habitat for microorganisms, as it hosts a significantly higher microbial abundance compared to the sediment and water. Moreover, 16S rRNA and amoA sequencing data indicate a high degree of compartmentalisation of functional microbial communities between the microenvironments of the seagrass meadow (leaf, sediment and water column), pointing towards the existence of a core seagrass leaf microbiome that could have specific interactions with the plant. For my third chapter I determined the role that microorganisms inhabiting P. sinuosa seagrass leaves may play in the recycling of DON, and subsequent transfer of inorganic N (DIN) into plant tissues. To achieve this, I performed an experiment whereby seagrass leaves with and without microorganisms were incubated with DO15N, and I traced the fine-scale uptake and assimilation of microbially processed N into seagrass cells, using nanoscale secondary ion mass spectrometry (NanoSIMS). Results from this chapter show for the first time that seagrass leaf epiphytic microorganisms facilitated the uptake of 15N from DON, which was unavailable to the plant in the absence of epiphytes. This indicates that seagrass leaves have limited to no ability to take up DON, and the seagrass leaf microbiome could therefore play a much more significant role than previously thought in enhancing plant health and productivity. Finally, I determined the net nitrification rates associated with ammoniaoxidising microorganisms (AOM) inhabiting P. sinuosa leaf surfaces, and explored whether AOM facilitated, or competed for, the plant’s N uptake. My findings show that AOM may compete with seagrasses for NH4 + uptake, but that their potential to outcompete seagrass epiphytic algae for DIN uptake indicates that AOM on seagrass leaves may serve as a ‘biocontrol’ over excess epiphytic algal growth. In summary, the present thesis represents a significant advance in our understanding of the seagrass leaf-microbiome relationship and transformations of N within seagrass meadows. Moreover, it opens up new questions for future research not only on seagrass-microbiome interactions but other macrophytes in aquatic systems that may benefit from the presence of specific N-cycling microorganisms

Positive ecological interactions and the success of seagrass restoration

Seagrasses provide multiple ecosystem services including nursery habitat, improved water quality, coastal protection, and carbon sequestration. However, seagrasses are in crisis as global coverage is declining at an accelerating rate. With increased focus on ecological restoration as a conservation strategy, methods that enhance restoration success need to be explored. Decades of work in coastal plant ecosystems, including seagrasses, has shown that positive species relationships and feedbacks are critical for ecosystem stability, expansion, and recovery from disturbance. We reviewed the restoration literature on seagrasses and found few studies have tested for the beneficial effects of including positive species interactions in seagrass restoration designs. Here we review the full suite of positive species interactions that have been documented in seagrass ecosystems, where they occur, and how they might be integrated into seagrass restoration. The few studies in marine plant communities that have explicitly incorporated positive species interactions and feedbacks have found an increase in plant growth with little additional resource investment. As oceans continue to change and stressors become more prevalent, harnessing positive interactions between species through innovative approaches will likely become key to successful seagrass restoration

Positive Ecological Interactions and the Success of Seagrass Restoration

Seagrasses provide multiple ecosystem services including nursery habitat, improved water quality, coastal protection, and carbon sequestration. However, seagrasses are in crisis as global coverage is declining at an accelerating rate. With increased focus on ecological restoration as a conservation strategy, methods that enhance restoration success need to be explored. Decades of work in coastal plant ecosystems, including seagrasses, has shown that positive species relationships and feedbacks are critical for ecosystem stability, expansion, and recovery from disturbance. We reviewed the restoration literature on seagrasses and found few studies have tested for the beneficial effects of including positive species interactions in seagrass restoration designs. Here we review the full suite of positive species interactions that have been documented in seagrass ecosystems, where they occur, and how they might be integrated into seagrass restoration. The few studies in marine plant communities that have explicitly incorporated positive species interactions and feedbacks have found an increase in plant growth with little additional resource investment. As oceans continue to change and stressors become more prevalent, harnessing positive interactions between species through innovative approaches will likely become key to successful seagrass restoration

The seagrass holobiont: Understanding seagrass-bacteria interactions and their role in seagrass ecosystem functioning

This review shows that the presence of seagrass microbial community is critical for the development of seagrasses; from seed germination, through to phytohormone production and enhanced nutrient availability, and defence against pathogens and saprophytes. The tight seagrass-bacterial relationship highlighted in this review supports the existence of a seagrass holobiont and adds to the growing evidence for the importance of marine eukaryotic microorganisms in sustaining vital ecosystems. Incorporating a micro-scale view on seagrass ecosystems substantially expands our understanding of ecosystem functioning and may have significant implications for future seagrass management and mitigation against human disturbance

Microorganisms facilitate uptake of dissolved organic nitrogen by seagrass leaves [dataset]

The database compiles data (used in Tarquinio et al. 2018, ISME Journal, accepted for publication) obtained from nitrogen stable isotope analysis (IRMS) and Nanoscale secondary ion mass spectrometry (NanoSIMS) of seagrass (Posidonia sinuosa) leaves and associated microorganisms. Row data (IRMS) are presented for bulk tissue 15N enrichment of P. sinuosa leaves at different times of incubation (plotted as bar chart in the manuscript), as well as the enrichment detected through the drawing of regions of interest (ROI) from NanoSIMS image analysis and plotted as box plots in the manuscript

Microbiomes of Western Australian marine environments

27 pages, 5 figures, 1 appendixMicrobes are fundamentally important to the maintenance of all habitats, including those in the ocean: they govern biogeochemical cycles, contribute to resistance from disease and nutritional requirements of macroorganisms and provide enormous biological and genetic diversity. The oceanic environment of the west coast of Australia is dominated by the Leeuwin Current, a poleward flowing boundary current that brings warm water down the coastline from the north. Due to the influence of the current, tropical species exist further south than they would otherwise, and stretches of the coastline host unique assortments of tropical and temperate species. Seawater itself, as well as the benthic macroorganisms that inhabit ocean environments, form habitats such as extensive areas of seagrass beds, macroalgal forests, coral reefs, sponge gardens, benthic mats including stromatolites, continental slopes and canyons and abyssal plain enviroments. These environments, and the macroorganisms that inhabit them, are all intrinsically linked with highly abundant and diverse consortiums of microorganisms. To date, there has been little research aimed at understanding these critical organisms within Western Australia. Here we review the current literature from the dominant coastal types (seagrass, coral, temperate macroalgae, vertebrates and stromatolites) in Western Australia. The most well researched are pelagic habitats and those with stromatolites, whereas data on all the other environments are slowly beginning to emerge. We urge future research efforts to be directed toward understanding the diversity, function, resilience and connectivity of coastal microorganisms in Western AustraliaPeer Reviewe

Microbiomes of Western Australian marine environments

Microbes are fundamentally important to the maintenance of all habitats, including those in the ocean: they govern biogeochemical cycles, contribute to resistance from disease and nutritional requirements of macroorganisms and provide enormous biological and genetic diversity. The oceanic environment of the west coast of Australia is dominated by the Leeuwin Current, a poleward flowing boundary current that brings warm water down the coastline from the north. Due to the influence of the current, tropical species exist further south than they would otherwise, and stretches of the coastline host unique assortments of tropical and temperate species. Seawater itself, as well as the benthic macroorganisms that inhabit ocean environments, form habitats such as extensive areas of seagrass beds, macroalgal forests, coral reefs, sponge gardens, benthic mats including stromatolites, continental slopes and canyons and abyssal plain enviroments. These environments, and the macroorganisms that inhabit them, are all intrinsically linked with highly abundant and diverse consortiums of microorganisms. To date, there has been little research aimed at understanding these critical organisms within Western Australia. Here we review the current literature from the dominant coastal types (seagrass, coral, temperate macroalgae, vertebrates and stromatolites) in Western Australia. The most well researched are pelagic habitats and those with stromatolites, whereas data on all the other environments are slowly beginning to emerge. We urge future research efforts to be directed toward understanding the diversity, function, resilience and connectivity of coastal microorganisms in Western Australia

Microbiomes of Western Australian marine environments

Volume: 101Start Page: 17End Page: 4

Organization and Activity of Italian Echocardiographic Laboratories: A Survey of the Italian Society of Echocardiography and Cardiovascular Imaging

Background: The Italian Society of Echocardiography and Cardiovascular Imaging (SIECVI) conducted a national survey to understand better how different echocardiographic modalities are used and accessed in Italy. Methods: We analyzed echocardiography laboratory activities over a month (November 2022). Data were retrieved via an electronic survey based on a structured questionnaire, uploaded on the SIECVI website. Results: Data were obtained from 228 echocardiographic laboratories: 112 centers (49%) in the northern, 43 centers (19%) in the central, and 73 (32%) in the southern regions. During the month of observation, we collected 101,050 transthoracic echocardiography (TTE) examinations performed in all centers. As concern other modalities there were performed 5497 transesophageal echocardiography (TEE) examinations in 161/228 centers (71%); 4057 stress echocardiography (SE) examinations in 179/228 centers (79%); and examinations with ultrasound contrast agents (UCAs) in 151/228 centers (66%). We did not find significant regional variations between the different modalities. The usage of picture archiving and communication system (PACS) was significantly higher in the northern (84%) versus central (49%) and southern (45%) centers (P < 0.001). Lung ultrasound (LUS) was performed in 154 centers (66%), without difference between cardiology and noncardiology centers. The evaluation of left ventricular (LV) ejection fraction was evaluated mainly using the qualitative method in 223 centers (94%), occasionally with the Simpson method in 193 centers (85%), and with selective use of the three-dimensional (3D) method in only 23 centers (10%). 3D TTE was present in 137 centers (70%), and 3D TEE in all centers where TEE was done (71%). The assessment of LV diastolic function was done routinely in 80% of the centers. Right ventricular function was evaluated using tricuspid annular plane systolic excursion in all centers, using tricuspid valve annular systolic velocity by tissue Doppler imaging in 53% of the centers, and using fractional area change in 33% of the centers. When we divided into cardiology (179, 78%) and noncardiology (49, 22%) centers, we found significant differences in the SE (93% vs. 26%, P < 0.001), TEE (85% vs. 18%), UCA (67% vs. 43%, P < 0001), and STE (87% vs. 20%, P < 0.001). The incidence of LUS evaluation was similar between the cardiology and noncardiology centers (69% vs. 61%, P = NS). Conclusions: This nationwide survey demonstrated that digital infrastructures and advanced echocardiography modalities, such as 3D and STE, are widely available in Italy with a notable diffuse uptake of LUS in the core TTE examination, a suboptimal diffusion of PACS recording, and conservative use of UCA, 3D, and strain. There are significant differences between northern and central-southern regions and echocardiographic laboratories that pertain to the cardiac unit. This inhomogeneous distribution of technology represents one of the main issues that must be solved to standardize the practice of echocardiography

Stress Echocardiography in Italian Echocardiographic Laboratories: A Survey of the Italian Society of Echocardiography and Cardiovascular Imaging

Background: The Italian Society of Echography and Cardiovascular Imaging (SIECVI) conducted a national survey to understand the volumes of activity, modalities and stressors used during stress echocardiography (SE) in Italy. Methods: We analyzed echocardiography laboratory activities over a month (November 2022). Data were retrieved through an electronic survey based on a structured questionnaire, uploaded on the SIECVI website. Results: Data were obtained from 228 echocardiographic laboratories, and SE examinations were performed in 179 centers (80.6%): 87 centers (47.5%) were in the northern regions of Italy, 33 centers (18.4%) were in the central regions, and 61 (34.1%) in the southern regions. We annotated a total of 4057 SE. We divided the SE centers into three groups, according to the numbers of SE performed: <10 SE (low-volume activity, 40 centers), between 10 and 39 SE (moderate volume activity, 102 centers) and >= 40 SE (high volume activity, 37 centers). Dipyridamole was used in 139 centers (77.6%); exercise in 120 centers (67.0%); dobutamine in 153 centers (85.4%); pacing in 37 centers (21.1%); and adenosine in 7 centers (4.0%). We found a significant difference between the stressors used and volume of activity of the centers, with a progressive increase in the prevalence of number of stressors from low to high volume activity (P = 0.033). The traditional evaluation of regional wall motion of the left ventricle was performed in all centers, with combined assessment of coronary flow velocity reserve (CFVR) in 90 centers (50.3%): there was a significant difference in the centers with different volume of SE activity: the incidence of analysis of CFVR was significantly higher in high volume centers compared to low - moderate - volume (32.5%, 41.0% and 73.0%, respectively, P < 0.001). The lung ultrasound (LUS) was assessed in 67 centers (37.4%). Furthermore for LUS, we found a significant difference in the centers with different volume of SE activity: significantly higher in high volume centers compared to low - moderate - volume (25.0%, 35.3% and 56.8%, respectively, P < 0.001). Conclusions: This nationwide survey demonstrated that SE was significantly widespread and practiced throughout Italy. In addition to the traditional indication to coronary artery disease based on regional wall motion analysis, other indications are emerging with an increase in the use of LUS and CFVR, especially in high-volume centers