The Impact of Physical Disturbance and Increased Sand Burial on Clonal Growth and Spatial Colonization of Sporobolus virginicus in a Coastal Dune System

Dune plants are subjected to disturbance and environmental stresses, but little is known about the possible combined effects of such factors on growth and spatial colonization. We investigated how clones of Sporobolus virginicus, a widespread dune species, responded to the independent and interactive effects of breakage of rhizomes, breakage position and burial regime. Horizontal rhizomes were severed at three different internode positions relative to the apex to span the range of damage by disturbance naturally observed or left intact, and apical portions exposed to two burial scenarios (ambient vs. increased frequency) for three months in the field. The performance of both parts of severed rhizomes, the apical portion and the remaining basal portion connected to clone containing four consecutive ramets, was compared with that of equivalent parts in intact rhizomes. Apical portions severed proximal to the third internode did not survive and their removal did not enhance branching on their respective basal portions. Severing the sixth or twelfth internode did not affect survival and rhizome extension of apical portions, but suppressed ramet production and reduced total biomass and specific shoot length. Their removal enhanced branching and ramet production on basal portions and changed the original rhizome growth trajectory. However, the gain in number of ramets in basal portions never compensated for the reduction in ramet number in apical portions. Recurrent burial increased biomass allocation to root tissues. Burial also stimulated rhizome extension only in intact rhizomes, indicating that disturbance interacts with, and counteracts, the positive burial effect. These results suggest that disturbance and recurrent burial in combination reduces the regeneration success and spread capacity of S. virginucus. Since global change leads to increasingly severe or frequent storms, the impact of disturbance and burial on clones could be greater in future and possibly prevent colonization of mobile dunes by the species

A Multi Size-Level Assessment of Benthic Marine Communities in a Coastal Environment: Are They Different Sides of the Same Coin?

Organism body size has been demonstrated to be a discriminating element in shaping the response of living beings to environmental factors, thus playing a fundamental role in community structuring. Despite the importance of studies elucidating relations among communities of different size levels in ecosystems, the attempts that have been made in this sense are still very scarce and a reliable approach for these research still has to be defined. We characterized the benthic communities of bacteria, microbial eukaryotes, meiofauna and macrofauna in a coastal environment, encompassing a 10000-fold gradient in body size, testing and discussing a mixed approach of molecular fingerprinting for microbes and morphological observations for meio- and macrofauna. We found no correlation among structures of the different size-level communities: this suggests that community composition at one size-level could have no (or very low) influence on the community composition at other size-levels. Moreover, each community responds in a different way to the environmental parameters and with a degree of sensitivity which seems to increase with organism size. Therefore, our data indicate that the characterization of all the different size levels is clearly a necessity in order to study the dynamics really acting in a system

Spatial variability of macrozoobenthic community and trophic structure of a subtropical lagoon on southeastern Brazil's Atlantic coast

The objective of this study was to investigate the macrobenthic community of two compartments of the Maricá-Guarapina lagoon system, along the coast of Rio de Janeiro, Brazil, in relation to its abiotic sediment factors. An additional discrimination between sites was made, wherever the macrophyte Typha domingensis was found. This vegetation supposedly represents a potentially important food source for consumers. Furthermore, the trophic pathways were analyzed functionally by means of stable isotope analysis to assess the role of organic matter sources for consumers in the study area. In conclusion, the results showed differences between abiotic features in the compartments of the lagoon system, which, although they have affected the different species' distribution, have led to a homogeneous low-diversity system. Macrozoobenthic species tend to change with increasing distance from the sea, with a slightly different distribution in the two compartments. The macrophyte T. domingensis did not exercise any great influence on the biotic distribution and was not the main food source for consumers in the lagoon system, where, instead, sedimentary organic matter and macrophyte detritus also seem to play an important role in the trophic web.O objetivo deste trabalho foi estudar a comunidade macrobentônica em dois compartimentos do sistema lagunar Maricá-Guarapina, situado na costa sudeste do Brazil, relacionando com fatores abióticos do sedimento. Adicionalmente, foi feita uma discriminação entre locais com e sem a presença da macrofita Thypha dominguensis, que supostamente representa uma importante fonte alimentar para os consumidores dos sistemas lagunares. A contribuição das macrofitas e outras fontes primárias de alimento para a rede trófica local foi investigada através do método das análises isotópicas. In conclusão, os resultados obtidos mostraram que os fatores abióticos diferiram pouco entre os compartimentos estudados, embora pareçam influenciar a distribuição do macrobentos local, que se caracteriza por uma baixa diversidade específica. As espécies do macrobentos tendem a mudar com o distanciamento do canal de conexão com o mar, existindo pouca diferença na estrutura da comunidade nos dois compartimentos. Igualmente, a presença da macrófita não influenciou a distribuição do macrobentos e os resultados da análise isotópica indicaram que a referida macrófita não representa fonte alimentar importante para os consumidores locais. Por sua vez, a matéria orgânica sedimentar e detritos de macrófitas parecem exercer um papel importante na rede trófica desse sistema lagunar

First evidence of root morphological and architectural variations in young Posidonia oceanica plants colonizing different substrate typologies

Root morphology and root system architecture of young Posidonia oceanica plants established on two contrasting substrate types, sand and rock, were examined to provide insights into the strategy of adaptation of seagrasses to their environment. After germination, seedlings were planted on sandy patches and on rock within the same area, and survived plants were collected five years later for measurements of the size of the entire root complex and analysis of individual morphological and architectural root traits. Collected plants exhibited up to nine highly intermingled root systems and approx. 2.5 m of total root length. Maximum horizontal extension, total biomass and total length of roots were not significantly affected by substrate. However, on sand roots grew vertically reaching up to 13 cm, while on rock they extended more horizontally and did not penetrate deeper than 5e7 cm leading to the formation of a shallow, densely packed root complex. On rock, the number and the length of second order laterals on an individual root system were reduced and the topological index higher than on sand (0.8 vs. 0.7) reflecting a more simple (herringbone) branching pattern. Again, root diameter was greater than on sand. The results suggest that P. oceanica can adjust root traits early during plant development according to substrate typology to maximize anchorage and substrate exploration efficiency. This plasticity enables the species to establish and persist also on rocky bottoms which generally prevent establishment of the majority of seagrasses

Spatial variability of macrozoobenthic community and trophic structure of a subtropical lagoon on southeastern Brazil's Atlantic coast

The objective of this study was to investigate the macrobenthic community of two compartments of the Maricá-Guarapina lagoon system, along the coast of Rio de Janeiro, Brazil, in relation to its abiotic sediment factors. An additional discrimination between sites was made, wherever the macrophyte Typha domingensis was found. This vegetation supposedly represents a potentially important food source for consumers. Furthermore, the trophic pathways were analyzed functionally by means of stable isotope analysis to assess the role of organic matter sources for consumers in the study area. In conclusion, the results showed differences between abiotic features in the compartments of the lagoon system, which, although they have affected the different species' distribution, have led to a homogeneous low-diversity system. Macrozoobenthic species tend to change with increasing distance from the sea, with a slightly different distribution in the two compartments. The macrophyte T. domingensis did not exercise any great influence on the biotic distribution and was not the main food source for consumers in the lagoon system, where, instead, sedimentary organic matter and macrophyte detritus also seem to play an important role in the trophic web

New Bio-Composites Based on Polyhydroxyalkanoates and Posidonia oceanica Fibres for Applications in a Marine Environment

Bio-composites based on polyhydroxyalkanoates (PHAs) and fibres of Posidonia oceanica (PO) were investigated to assess their processability by extrusion, mechanical properties, and potential biodegradability in a natural marine environment. PHAs were successfully compounded with PO fibres up to 20 wt%while, at 30 wt%of fibres, the addition of 10 wt%of polyethylene glycol (PEG 400) was necessary to improve their processability. Thermal, rheological, mechanical, and morphological characterizations of the developed composites were conducted and the degradation of composite films in a natural marine habitat was evaluated in a mesocosm by weight loss measure during an incubation period of six months. The addition of PO fibres led to an increase in stiffness of the composites with tensile modulus values about 80% higher for composites with 30 wt % fibre (2.3 GPa) compared to unfilled material (1.24 GPa). Furthermore, the impact energy markedly increased with the addition of the PO fibres, from 1.63 (unfilled material) to 3.8 kJ/m2 for the composites with 30 wt % PO. The rate of degradation was markedly influenced by seawater temperature and significantly promoted by the presence of PO fibres leading to the total degradation of the film with 30 wt % PO in less than six months. The obtained results showed that the developed composites can be suitable to manufacture items usable in marine environments, for example, in natural engineering interventions, and represent an interesting valorisation of the PO fibrous wastes accumulated in large amounts on coastal beaches

Biocomposites based on PHBs and natural fibers for commodity applications in different environments: processing, performance in soil, compost and sea water

Composites based on poly(3-hydroxybutyrate) (PHB) and natural fibres such as fibres of Posidonia oceanica (PO), wood saw dust (WSD) and bran were produced by extrusion in presence of appropriate amounts of plasticizer (Acetyl Tri-n- Butyl Citrate, ATBC) and filler (calcium carbonate). Thermal, rheological, mechanical and morphological characterizations of the developed composites were conducted in order to optimize formulations in terms of processability and mechanical performance. The biodegradability of the optimized composites was investigated under controlled composting conditions in accordance with standard methods (ASTM D5338-98, ISO 20200-2004) and in soil for the PHB/WSD composites, because their expected fate is to be treated in composting plants or used for applications in agriculture; in simulated and natural marine sediments in mesocosms and dune habitat for the PHB/PO composites, because their potential applications are in marine environment, such as natural engineering interventions (restoration of seagrass habitats). The optimized PHB/WSD compounds were used for the production of pots for terrestrial plants, PHB/PO compounds for pots and other items usable in the sea and sand dunes, such as transplanting tools and structures for restoration or protection of coastal habitats, and the PHB/bran fibres for the production of food contact containers. The results showed that the industrial processing by extrusion of the composites did not show any difficulty up to 20 wt. % fibres and the presence of the fibres (PO or WSD) facilitated the disintegration of the PHB matrix and, consequently, accelerated its biodegradation both in compost, soil, sea water and dune. The PHB/WSD composites resulted no-phytotoxic by using cress (Lepidium sativum L.) germination test, compostable in accordance with EN 13427:2000, biodegradable in soil at controlled degradation rate. The PHB/PO composites showed a good controlled biodegradation rate in marine sediments and were suitable to manufacture items usable, for example, in natural engineering interventions and represent an interesting valorisation of the PO fibrous wastes accumulated in large amounts on coastal beaches

Identificazione mediante DNA barcoding del mitilide alloctono <i>Xenostrobus securis</i> e nuove segnalazioni in Mediterraneo occidentale = DNA barcoding identification of the exotic mussel <i>Xenostrobus securis</i> and new records in Western Mediterranean

The present study reports species' identification by means of DNA barcoding and new records of the invasive pygmy mussel Xenostrobus securis (Lam. 1819) (Mollusca, Bivalvia), native to South Oceania, in some Western Mediterranean brackish-water biotopes. Monitoring of this species is recommended, given its ecological effects on native biological communities and as fouling agent

Virus contamination and infectivity in beach environment: Focus on sand and stranded material

To assess the exposure of beachgoers to viruses, a study on seawater, sand, and beach-stranded material was carried out, searching for human viruses, fecal indicator organisms, and total fungi. Moreover, for the first time, the genome persistence and infectivity of two model viruses was studied in laboratory-spiked sand and seawater samples during a one-week experiment. Viral genome was detected in 13.6 % of the environmental samples, but it was not infectious (Human Adenovirus – HAdV, and enterovirus). Norovirus and SARS-CoV-2 were not detected. The most contaminated samples were from sand and close to riverine discharges. In lab-scale experiments, the infectivity of HAdV5 decreased by ~1.5-Log10 in a week, the one of Human Coronavirus-229E disappeared in &lt;3 h in sand. The genome of both viruses persisted throughout the experiment. Our results confirm viral contamination of the beach and suggest HAdV as an index pathogen for beach monitoring and quantitative risk assessment

Spatial Relationships between Polychaete Assemblages and Environmental Variables over Broad Geographical Scales

This study examined spatial relationships between rocky shore polychaete assemblages and environmental variables over broad geographical scales, using a database compiled within the Census of Marine Life NaGISA (Natural Geography In Shore Areas) research program. The database consisted of abundance measures of polychaetes classified at the genus and family levels for 74 and 93 sites, respectively, from nine geographic regions. We tested the general hypothesis that the set of environmental variables emerging as potentially important drivers of variation in polychaete assemblages depend on the spatial scale considered. Through Moran's eigenvector maps we indentified three submodels reflecting spatial relationships among sampling sites at intercontinental (>10000 km), continental (1000–5000 km) and regional (20–500 km) scales. Using redundancy analysis we found that most environmental variables contributed to explain a large and significant proportion of variation of the intercontinental submodel both for genera and families (54% and 53%, respectively). A subset of these variables, organic pollution, inorganic pollution, primary productivity and nutrient contamination was also significantly related to spatial variation at the continental scale, explaining 25% and 32% of the variance at the genus and family levels, respectively. These variables should therefore be preferably considered when forecasting large-scale spatial patterns of polychaete assemblages in relation to ongoing or predicted changes in environmental conditions. None of the variables considered in this study were significantly related to the regional submodel