Investigating marine shallow waters dynamics to explore the role of turbidity on ecological responses

The ecological tangible effect of the complex interaction between sediments and water column in shallow waters is represented by turbidity which is a common feature of most aquatic ecosystems: it varies both temporally and spatially; it can cover a huge area and persist for a long period or it can be very localized and temporary. Among many factors able to generate turbidity, wind generated wave action and water mass movements due to tides seem important in causing resuspension of sediments. Although there is much research spent in last decades on this topic and many models to explain the complexity of the wind-water-sediment interaction, some interactive aspects are too site specific and then still poor understood. On the other hand, this interaction involves many physical, chemical and trophic aspects like water flow velocity, turbulence, boundary layer thickness, environmental stresses and, in turn, resuspension, transport, and deposition of particulate matter, mechanical limits to size, larval dispersion, food availability. To get further knowledge on these aspects, we carried out in March 2007 a 5-day-experiment in a Mediterranean shallow area (The Stagnone di Marsala, Western Sicily) by collecting data on wind and water velocities, their directions and the contextual response of the water column in term of turbidity, chlorophyll-a and suspended solids (by ignition). To analyse the interaction, we proceeded step by step. Firstly, we studied data from the two current meters (an acoustic doppler velocimeter 40 ± 2 cm deep, and an electromagnetic current meter 20 ± 2 cm deep). From this data, the water column had the following features: i) during the big semidiurnal tidal transitional phase, the flow field followed a behaviour leading us to hypothesize a logarithmic layer defined by the law of the wall and to obtain friction velocity values with linear regression in good agreement with calculated ones with covariance and TKE method, while ii) during the small tidal transition and at high and low tides, a not-well defined gradient was present (i.e., the mean deviation of the direction of the two water velocities was more than 30° and the flow magnitude at 40 cm was less than that measured at 20 cm implying high values of turbulence intensity). The second step analysed data from multiprobe, ADV, meteorological station and considered turbidity (NTU) as proxy of food availability for consumers. NTU followed a one-day-period and the lower the turbidity, the higher the turbulence (both at 20 and 40 cm)

Microbiome network in the pelagic and benthic offshore systems of the northern Adriatic Sea (Mediterranean Sea)

Because of their recognized global importance, there is now the urgent need to map diversity and distribution patterns of marine microbial communities. Even if available studies provided some advances in the understanding the biogeographical patterns of marine microbiomes at the global scale, their degree of plasticity at the local scale it is still underexplored, and functional implications still need to be dissected. In this scenario here we provide a synoptical study on the microbiomes of the water column and surface sediments from 19 sites in a 130 km2 area located 13.5 km afar from the coast in the North-Western Adriatic Sea (Italy), providing the finest-scale mapping of marine microbiomes in the Mediterranean Sea. Pelagic and benthic microbiomes in the study area showed sector specific-patterns and distinct assemblage structures, corresponding to specific variations in the microbiome network structure. While maintaining a balanced structure in terms of potential ecosystem services (e.g., hydrocarbon degradation and nutrient cycling), sector-specific patterns of over-abundant modules-and taxa-were defined, with the South sector (the closest to the coast) characterized by microbial groups of terrestrial origins, both in the pelagic and the benthic realms. By the granular assessment of the marine microbiome changes at the local scale, we have been able to describe, to our knowledge at the first time, the integration of terrestrial microorganisms in the marine microbiome networks, as a possible natural process characterizing eutrophic coastal area. This raises the question about the biological threshold for terrestrial microorganisms to be admitted in the marine microbiome networks, without altering the ecological balance

Impact of mangrove forests degradation on biodiversity and ecosystem functioning

Abstract Mangroves are amongst the most productive marine ecosystems on Earth, providing a unique habitat opportunity for many species and key goods and services for human beings. Mangrove habitats are regressing at an alarming rate, due to direct anthropogenic impacts and global change. Here, in order to assess the effects of mangrove habitat degradation on benthic biodiversity and ecosystem functioning, we investigated meiofaunal biodiversity (as proxy of benthic biodiversity), benthic biomass and prokaryotic heterotrophic production (as proxies of ecosystem functioning) and trophic state in a disturbed and an undisturbed mangrove forests. We report here that disturbed mangrove area showed a loss of 20% of benthic biodiversity, with the local extinction of four Phyla (Cladocera, Kynorincha, Priapulida, Tanaidacea), a loss of 80% of microbial-mediated decomposition rates, of the benthic biomass and of the trophic resources. The results of this study strengthen the need to preserve mangrove forests and to restore those degraded to guarantee the provision of goods and services needed to support the biodiversity and functioning of wide portions of tropical ecosystems

In Vitro Evaluation of Antioxidant Potential of the Invasive Seagrass Halophila stipulacea

none10Marine organisms with fast growth rates and great biological adaptive capacity might have biotechnological interests, since ecological competitiveness might rely on enhanced physiological or biochemical processes’ capability promoting protection, defense, or repair intracellular damages. The invasive seagrass Halophila stipulacea, a non-indigenous species widespread in the Mediterranean Sea, belongs to this category. This is the premise to investigate the biotechnological interest of this species. In this study, we investigated the antioxidant activity in vitro, both in scavenging reactive oxygen species and in repairing damages from oxidative stress on the fibroblast human cell line WI-38. Together with the biochemical analysis, the antioxidant activity was characterized by the study of the expression of oxidative stress gene in WI-38 cells in presence or absence of the H. stipulacea extract. Concomitantly, the pigment pool of the extracts, as well as their macromolecular composition was characterized. This study was done separately on mature and young leaves. Results indicated that mature leaves exerted a great activity in scavenging reactive oxygen species and repairing damages from oxidative stress in the WI-38 cell line. This activity was paralleled to an enhanced carotenoids content in the mature leaf extracts and a higher carbohydrate contribution to organic matter. Our results suggest a potential of the old leaves of H. stipulacea as oxidative stress damage protecting or repair agents in fibroblast cell lines. This study paves the way to transmute the invasive H. stipulacea environmental threat in goods for human health.openClementina Sansone; Christian Galasso; Marco Lo Martire; Tomás Vega Fernández; Luigi Musco; Antonio Dell’Anno; Antonino Bruno; Douglas M. Noonan; Adriana Albini; Christophe BrunetSansone, Clementina; Galasso, Christian; Lo Martire, Marco; Vega Fernández, Tomás; Musco, Luigi; Dell’Anno, Antonio; Bruno, Antonino; Noonan, Douglas M.; Albini, Adriana; Brunet, Christoph

Combining passive and active restoration to rehabilitate a historically polluted marine site

IntroductionPassive and active restoration approaches have been often considered as different alternatives to achieve the ecological restoration of a degraded site. This false dichotomy has been overcome in terrestrial ecosystems, for which a range of restoration approaches have often been applied within the same restoration project, creating a continuum of interventions. In the marine environment, the combined approach based on passive and active restoration is less studied.MethodsHere, we tested the possibility of actively restoring a macroalgal population in a historically polluted industrial site, subjected to decadal passive restoration (i.e., unassisted, or spontaneous recovery following cessation of industrial activity), in the Mediterranean Sea. Recently, it has been demonstrated that in the site under scrutiny, there is no longer any sign of the historical contamination or impact on benthic fauna therefore the environmental conditions are indistinguishable from surrounding non-impacted areas. We used artificial breakwater barriers already present in the site to restore a population of the brown algae Gongolaria barbata. The intervention was conducted by applying an in situ recruitment approach and a complementary action using cages to exclude the herbivores. The G. barbata recruits were transplanted on the artificial reefs and after they reached the maximum growth inside the cages, one cage was opened and another one was completely removed to also test the grazing pressure. The associated benthic assemblages were also analysed in terms of meio- and macrofaunal abundance, the richness of taxa, and taxonomic composition.Results and discussionOur results indicate that, at least over a relatively short period (i.e., 6 months), the use of the cages represents a useful tool to let the macroalgae grow enough to counterbalance the herbivory pressure. The associated fauna below the macroalgae was characterized by a different taxonomic composition when compared to controls (i.e., artificial reefs without the macroalgae), particularly when considered the rare taxa. In conclusion, the combination of passive and active restoration can be considered a useful approach to restore marine sites degraded by historical industrial activities

The paradox of an unpolluted coastal site facing a chronically contaminated industrial area

Present and past industrial activities in coastal areas have left us a legacy of contamination and habitat degradation with potential implications for human health. Here, we investigated a coastal marine area enclosed in a Site of National Interest (SNI) of the central-western Adriatic (Mediterranean Sea), where priority actions of environmental remediation are required by governmental laws due the high environmental and human risk, and that is off-limits to any human activity since 2002. In particular, our investigation was focused on an area located in front of a chemical industry dismissed more than 3 decades ago. We report that the concentrations of heavy-metal and organic contaminants in the investigated sediments were generally lower than those expected to induce detrimental biological effects. Meiofaunal abundance, biomass and community structure changed among stations, but regardless of the distance from the abandoned industrial plant. Taxa richness within the SNI did not change significantly compared to the controls and the lack of some taxa in the SNI transects was not due to the contamination of the SNI area. The results of this study suggest a natural recovery of the marine area over 2 decades of restrictions on human activities, including fishing and shipping bans. If the hypothesis of the natural recovery of this SNI will be further confirmed by other studies, the plans forthe identification and monitoring of the most polluted areas in Italy should necessarily be redefined also in the light of the Water Framework, the Marine Strategy Framework and the Environmental Quality Standard Directives

Rhodobacteraceae dominate the core microbiome of the sea star Odontaster validus (Koehler, 1906) in two opposite geographical sectors of the Antarctic Ocean

Microbiota plays essential roles in the health, physiology, and in adaptation of marine multi-cellular organisms to their environment. In Antarctica, marine organisms have a wide range of unique physiological functions and adaptive strategies, useful for coping with extremely cold conditions. However, the role of microbiota associated with Antarctic organisms in such adaptive strategies is underexplored. In the present study, we investigated the diversity and putative functions of the microbiome of the sea star Odontaster validus, one of the main keystone species of the Antarctic benthic ecosystems. We compared the whole-body bacterial microbiome of sea stars from different sites of the Antarctic Peninsula and Ross Sea, two areas located in two opposite geographical sectors of the Antarctic continent. The taxonomic composition of O. validus microbiomes changed both between and within the two Antarctic sectors, suggesting that environmental and biological factors acting both at large and local scales may influence microbiome diversity. Despite this, one bacterial family (Rhodobacteraceae) was shared among all sea star individuals from the two geographical sectors, representing up to 95% of the microbial core, and suggesting a key functional role of this taxon in holobiont metabolism and well-being. In addition, the genus Roseobacter belonging to this family was also present in the surrounding sediment, implying a potential horizontal acquisition of dominant bacterial core taxa via host-selection processes from the environment

Macroalgal forest restoration: the effect of the foundation species

IntroductionActive restoration is the strategy needed to trigger or accelerate the recovery of degraded marine habitats, which provide the goods and services essential for preserving biodiversity and human wellbeing. Ecosystem engineers are generally the target species in the ecological restoration of marine ecosystems, and large-sized brown macroalgae (e.g., the Cystoseira complex) are a priority due to their crucial ecological importance and vulnerability in many regions of the Mediterranean Sea. MethodsHere, we present the results of a successful intervention of ecological restoration of Gongolaria barbata. Results and DiscussionOne year after the restoration intervention, we observed the recovery of the canopy in terms of ca. 15m2 with a significant increase in faunal abundance and biodiversity compared with reference areas. However, despite the high restored macroalgal growth rates, the assemblage structure was still significantly different from that of reference pristine areas. Despite the fast faunal colonization of a new 3D habitat linked to the successful re-introduction of the ecosystem engineers (i.e., macroalgae), the complete restoration of the properties of a habitat can be a much longer process. We conclude that, after 1 year, active restoration of macroalgal forests still results in a partial recovery of ecosystem functions (i.e., rehabilitation) rather than a full ecosystem restoration, thus stressing the need for long-term monitoring of restoration interventions

Fattori di controllo della disponibilità alimentare per il benthos eterotrofo in ambienti costieri di interfaccia

Gli ecosistemi di interfaccia, sono rappresentati da tutti quegli habitat al confine tra terre emerse continentali e ambienti acquatici. Essi sono la fase dinamica di incontro tra ambienti largamente differenti (mare, terra, atmosfera) definita come “interfaccia”, nella quale è possibile riconoscere la transizione da un sistema all’altro per la presenza di marcati gradienti fisico-chimici, biologici ed ecologici. Nella fattispecie, questi ecosistemi sono rappresentati dagli ambienti costieri di basso fondale e da ambienti intertidali di substrato duro. Essi sono i principali fornitori di beni e servizi ecosistemici per le popolazioni costiere. In questa tesi si è studiato il ruolo della variabilità sistemica in ambienti intertidali di bassofondo su alcuni aspetti salienti del funzionamento ecosistemico, della biodiversità e in ultimis sulla relazione tra biodiversità e funzionamento ecosistemico. L’obiettivo è stato quello di studiare l’effetto della variabilità fisica e chimica come fattore di controllo nei due habitat modello (laguna e pozze intertidali) lungo le coste della Sicilia nord-occidentale, sulle caratteristiche del cibo disponibile - proveniente da produzione primaria e secondaria. I risultati di questo studio mettono in evidenza il ruolo determinante della variabilità spaziale e temporale, la quale controlla ampiamente le dinamiche chimico fisiche e trofiche in questi ambienti estremi. Ad esempio nello Stagnone di Marsala l’energia meccanica di attrito innescata dalla sinergia vento/marea gioca un ruolo importante sulla disponibilità di cibo, favorendo gli scambi tra il comparto sedimentario e la colonna d’acqua. La presenza di vegetazione smorza l’entità degli scambi che divengono massimi quando le fanerogame marine sono rade o assenti. I risultati degli esperimenti su gli ambienti di pozza, hanno dimostrato l’importanza di questi habitat sotto molti aspetti. Le pozze di scogliera del Mediterraneo, le cui dinamiche fisiche e chimiche sono azionate dalle escursioni mareali funzionano come veri e propri bio-reattori. In particolare, è stato dimostrato che, ogni sei ore, per effetto dell’isolamento in emersione, le pozze di scogliera triplicano il contenuto di materiale organico, il quale viene disperso nell’adiacente intertidale, al momento del collegamento con il mare nella successiva alta marea. Dato l’elevatissimo numero di pozze presenti lungo le coste rocciose, l’export di materia organica labile prodotta quotidianamente è quantitativamente rilevante. Questo sink di energia contribuisce indubbiamente a favorire il mantenimento degli elevati livelli di biodiversità tipici di questi ambienti del Mediterraneo. I risultati di questo studio forniscono nuove informazioni utili alla comprensione del funzionamento degli ecosistemi di interfaccia marino-costieri, che sono stati fino ad ora, la fonte più importante di approvvigionamento per le popolazioni rivierasche di tutto il pianeta