Microbial and Trophic Shifts in the Salt Marsh Palud-Palù, Adriatic Coast

Salt marsh ecosystems are recognized as highly productive, diverse systems which provide key services to society, but are facing an increasing number of multiple human pressures resulting in global losses of these ecosystems. I aimed to assess the effects of human pressures on salt marsh status and functioning, focusing on the perennial Spartina spp. grasses across the Northern Adriatic Sea, using a combination of field observational studies, manipulation of pressures on salt marshes, and wave mesocosm experiments to measure erosion resistance. Major findings include: 1. Macrobenthos diversity and abundance in Spartina spp. patches were influenced by sediment and nutrient variables, and indirectly influenced by Spartina spp. which modified the sdiments via organic enrichment; 2. Spartina spp. below-ground biomass decreased resistance to erosion, with a more pronounced effect in sandy compared to silty sediments; 3. A heat wave that occurred in 2015 synergistically interacted with high nutrient loads to change the vegetation composition in experimentally fertilized plots, with a rapid shift from Spartina spp. grasses to Salicornia spp. succulents, and the heat wave triggered changes in sediment properties that reduced the erosion resistance of salt marsh sediments; 4. After exposure to different inundation levels through a salt marsh transplantation experiment, plant survival (indicated by % live shoot biomass) and % silt were the most significant predictors of erosion resistance. Overall, biomass and sediment properties were the main factors influencing lateral resistance to erosion in our experiments. The research in this thesis fills important knowledge gaps regarding the status of salt marshes and their functioning across lagoons of the Northern Adriatic Sea. These results help to consolidate the evidence of the important role of salt marsh vegetation in coastal protection, and demonstrate the conditions under which erosion resistance in salt marshes is most effective.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 121:99-116 (1995) - doi:10.3354/meps121099 The role of standing dead Spartina alterniflora and benthic microalgae in salt marsh food webs: considerations based on multiple stable isotope analysis Currin CA, Newell SY, Paerl HW The stable isotope compositions (C, N, and S) of live, senescent, and standing dead Spartina alterniflora were compared in order to determine the effects of aerial decomposition on the isotopic signature of aboveground S. alterniflora tissue entering the food chain. Aerial decomposition of aboveground S. alterniflora resulted in a 6 to 18 o/oo increase in delta34S, and a 2 to 3 o/oo decrease in delta15N values; delta13C values were unchanged. We describe mechanisms whereby the activity of fungi and epiphytic microorganisms may contribute to the observed shifts in delta34S and delta15N, respectively. The delta13C value of salt marsh benthic and epiphytic microalgae ranged from -13.0 o/oo in summer to -17.6 o/oo in early spring. Average delta15N values of microalgae and standing dead S. alterniflora were -0.3 and 1.7 o/oo, respectively, reflecting the activity of N2-fixing microorganisms. The delta15N values for omnivorous and herbivorous salt marsh macrofauna ranged between 7.5 and 2.2 o/oo, and for predatory Fundulus spp. delta15N averaged 9.2 o/oo. Given a presumptive +3 o/oo trophic shift in N assimilation, these results suggest that N2-fixing microorganisms associated with microalgal communities were an important source of N to salt marsh consumers. The delta13C, delta15N, and delta34S values of primary producers were compared to the values of the following consumers: Fundulus spp., Uca spp., Ilyanassa obsoleta, and Littoraria irrorata. delta13C vs delta15N and delta13C vs delta34S dual isotope plots demonstrated that microalgae and standing dead S. alterniflora are important food resources in the North Carolina (USA) marshes we sampled. In addition, a compilation of literature values suggests that this is true in salt marshes throughout the East and Gulf coasts of North America. Future isotope studies of marsh food webs should include detrital Spartina spp. material in analyses of trophic structure. Spartina alterniflora . Benthic microalgae . Stable isotopes . Salt marsh . Food web Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 121. Publication date: May 25, 1995 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1995 Inter-Research.

This study investigated the trophic shift of young-of-the-year (YOY) thinlip grey mullet Liza ramada and golden grey mullet Liza aurata during their recruitment in a salt marsh located on the European Atlantic Ocean coast. Stable-isotope signatures (δ(13) C and δ(15) N) of the fishes followed a pattern, having enrichments in (13) C and (15) N with increasing fork length (LF ): δ(13) C in fishes < 30 mm ranged from -19.5 to -15.0‰, whereas in fishes > 30 mm δ(13) C ranged from -15.8 to -12.7‰, closer to the level in salt-marsh food resources. Large differences between the δ(15) N values of mugilids and those of food sources (6·0‰ on average) showed that YOY are secondary consumers, similar to older individuals, when feeding in the salt marsh. YOY mugilids shift from browsing on pelagic prey to grazing on benthic resources from the salt marsh before reaching 30 mm LF. The results highlight the role of European salt marshes as nurseries for juvenile mugilids.

Lagoonal environments are highly biodiverse coastal ecosystems, extremely susceptible to multiple anthropogenic and natural stressors (eutrophication, contaminants, storms and floods, relative sea-level rise among others). Given their ecological importance, effective monitoring and restoration strategies are essential to safeguard their integrity. The quantitative assessment of the Ecological Quality Status (EcoQS) represents a fundamental step in designing action plans through an ecosystem-based approach that incorporates biological indicators, as mandated by the EU Water Framework Directive (2000) and the Marine Strategy Framework Directive (2008/56/EC).This study aims to contextualize the EcoQS of a modern lagoon (Bellocchio Lagoon) belonging to the Po coastal plain (N Adriatic Sea), by comparing current values with pristine reference conditions from the past. To achieve this purpose, we integrated analyses of benthic foraminiferal assemblages from sediment cores and modern samples to reconstruct environmental changes and EcoQS temporal trends mainly applying the Foram-AMBI index, which is based on species sensitivity to organic-matter enrichment.Reference conditions were reconstructed analyzing the foraminiferal assemblages encased within the well-dated sedimentary successions of a near-site humid area, whose Holocene record reflects depositional environments comparable, though on a different scale, to the Bellocchio Lagoon.A reliable comparison of past and present environments was based on the identification of three distinct biofacies within the Bellocchio Lagoon, by means of cluster analyses based on the benthic foraminiferal thanatocoenoses. Each biofacies corresponds to a sub environment (i.e. inner lagoon, outer lagoon, and salt marsh - channels) characterized by a typifying foraminiferal content and a set of environmental parameters (i.e. sand, calcium carbonate and total organic matter content). Using the Modern Analogue Matching technique, cores assemblages were compared to the biofacies, enabling the identification of modern analogues for past depositional settings. The reconstruction of long-term ecosystems&amp;#8217; dynamics and the assessment of the Ecological Quality Ratio, calculated comparing the EcoQS derived from core samples with the EcoQS of modern biocoenoses, allow to evaluate the present-day ecological conditions in the context of the natural and human forcing factors that have affected lagoonal environments over time.

A comparative analysis of inter- and intra-habitat variations of detritus decay rates across ecosystem types was carried out in the Lake Alimini complex (Italy) to assess the relevance of major structural ecosystem features on detritus processing rates. Reed (Phragmites australis) detritus decomposition was studied in a stream, a freshwater lake and a salt marsh on a seasonal basis at a total of 20 sampling stations using the leaf pack technique. Overall, the spatial variability of leaf decomposition rates was more pronounced than the temporal variability, decomposition rates in the stream being 3.6 and 5.2 times faster than in the freshwater lake and salt marsh, respectively. The intra-habitat spatial variability of leaf decay rates in the stream was also higher than in the other systems. Environmental features were relevant factors affecting intra- and inter-habitat variation of reed decay rates, and their relevance to leaf detritus decomposition showed a strong seasonal variation.

Since large stretches of European coasts are already retreating and projected scenarios are worsening, many artificial structures, such as breakwaters and seawalls, are built as tool against coastal erosion. However artificial structures produce widespread changes that alter the coastal zones and affect the biological communities. My doctoral thesis analyses the consequences of different options for coastal protection, namely hard engineering ‘artificial defences’ (i.e. impact of human-made structures) and ‘no-defence’ (i.e. impact of seawater inundation). I investigated two new aspects of the potential impact of coastal defences. The first was the effect of artificial hard substrates on the fish communities structure. In particular I was interested to test if the differences among breakwaters and natural rocky reef would change depending on the nature of the surrounding habitat of the artificial structure (prevalent sandy rather than rocky). The second was the effect on the native natural sandy habitats of the organic detritus derived from hard-bottom species (green algae and mussels) detached from breakwaters. Furthermore, I investigated the ecological implication of the “no-defend” option, which allow the inundation of coastal habitats. The focus of this study was the potential effect of seawater intrusion on the degradation process of marine, salt-marsh and terrestrial detritus, including changes on the breakdown rates and the associated macrofauna. The PhD research was conducted in three areas along European coasts: North Adriatic sea, Sicilian coast and South-West England where different habitats (coastal, estuarine), biological communities (soft-bottom macro-benthos; rocky-coastal fishes; estuarine macro-invertebrates) and processes (organic enrichment; assemblage structure; leaf-litter breakdown) were analyzed. The research was carried out through manipulative and descriptive field-experiments in which specific hypothesis were tested by univariate and multivariate analyses.

Carbon and nitrogen isotope compositions of organic matter in coastal marine sediments (the Gulf of Trieste, N Adriatic Sea): indicators of sources and preservation

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 367:93-107 (2008) - DOI: https://doi.org/10.3354/meps07566 Relative importance of vascular plants and algal production in the food web of a Spartina-invaded salt marsh in the Yangtze River estuary X. Shang1,2,*, G. S. Zhang1, J. Zhang1 1State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 3663 Zhongshan Road North, Shanghai 200062, PR China 2School of Environment and Public Health, Wenzhou Medical College, Wenzhou 325035, PR China *Email: archershang@hotmail.com ABSTRACT: The trophic importance of microphytobenthos (MPB), phytoplankton, C3 vascular plants and invasive Spartina alterniflora in benthic and pelagic food webs was studied in Jiuduansha, a newly formed salt marsh in the Yangtze River estuary, using natural stable carbon and nitrogen isotopic analyses and IsoSource evaluation. MPB was found to be the major food source of meiofauna and important in the diets of macrofaunal consumers. Carbon derived from C3 vascular plants significantly contributed to the nutrition of all planktonic copepods and supported planktivorous nekton, but played a minor role in the benthic food web. Although phytoplankton could be utilized by all the consumers, low production in this highly turbid estuary might restrict its relative importance. High trophic-level consumers could get carbon from 13C-enriched MPB and 13C-depleted C3 plants via zoobenthos and zooplankton, respectively. Neither benthic nor pelagic animals fed exclusively on S. alterniflora except for a gastropod species in the present study, indicating a minor contribution of this invasive C4 plant to the food web of the Jiuduansha salt marsh. In light of the degradation of salt marshes in the Yangtze River estuary, the rapid expansion of this invasive C4 plant may alter the nutrient foundation of resident and migratory consumers and thus significantly impact the ecosystem there. KEY WORDS: Salt marsh · Food web · Microphytobenthos · Spartina alterniflora · Invasion · Trophic shift Full text in pdf format PreviousNextCite this article as: Shang X, Zhang GS, Zhang J (2008) Relative importance of vascular plants and algal production in the food web of a Spartina-invaded salt marsh in the Yangtze River estuary. Mar Ecol Prog Ser 367:93-107. https://doi.org/10.3354/meps07566 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 367. Online publication date: September 11, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Hydromorphic to subaqueous soils transitions in the central Grado lagoon (Northern Adriatic Sea, Italy)

In this work we investigate the development of a salt marsh environment during the Holocene marine transgression in the North Adriatic coast (North Italy) near the pre-Roman and Roman towns of Cittanova and Concordia Sagittaria. Pollen, plant macrofossils, non-pollen palynomorphs (NPPs) and foraminifers are analysed in cores and archaeological excavations to indicate the development of salt marsh plant communities. Other independent proxies (foraminifers, plant macrofossils, molluscs) confirm the ecological interpretation based on pollen records. The relevance of NPPs as indicators of salt marsh environment is evaluated. Linings of foraminifers are the most frequent NPP type, recorded in 85% of the brackish sediments. They may tentatively be referred to the genus Ammonia, a very common benthonic genus in the present lagoons of the North Adriatic Sea. Radiocarbon dates available from previous work allow the salt marsh development to be dated in the sector from the east of the Lagoon of Venice to the Lagoon of Caorle. Near Cittanova, salt marshes developed before 6700 yrs cal. b.p. At Concordia Sagittaria, the first evidence dates from ca. 6700 yrs cal. b.p. and a phase of freshwater conditions is recorded in the sediments of ca. 4500 yrs cal. b.p.

Carbon-rich substrates altered microbial communities with indication of carbon metabolism functional shifting in a degraded salt marsh of the Yellow River Delta, China

Lagoons and estuaries are transitional waters (TW), saline in character but substantially influenced by freshwater (FW) flows and the most productive habitat after upwelling areas. The European eel, Anguilla anguilla, is a typical inhabitant of these habitats and a target of important lagoon fisheries since ancient times. Notwithstanding this, in the Mediterranean region, where the numerous coastal lagoons are the most eligible habitat for this species, eel habitat use and growth, which display a high inter‐individual variability, are poorly studied. To gain knowledge about the migratory behaviour and the relative growth history of this species in TW in the Mediterranean area, the otolith Sr/Ca ratios of 56 individuals were analysed. The study sampling sites were two typical coastal lagoon environments, Caprolace lagoon and Lesina lagoon, located, respectively on the Tyrrhenian and the Adriatic coast of Italy, and the Tiber River (TR) estuary, in Central Italy. Otolith Sr/Ca profiles revealed that in all the sites, the resident contingent is substantial, while the proportion of nomad eels, or habitat inter‐shifter, was different among sites. Mean annual grow rate of resident eels is higher in productive environments (TR and lagoon of Lesina), while in Caprolace lagoon, an oligotrophic lagoon, resident eels grow slower. The observed patterns of habitat use and growth seem linked to local ecological conditions: facultative movements of eels with a nomadic behaviour seem affected by food availability rather than by the salinity gradient. This consideration supports the hypothesis that the facultative catadromous migration of European eel in Mediterranean TW, and the trophic shifts that this species exhibits, depend primarily on the productivity of the environment rather than on its salinity gradient.

Because most plant production is subject to senescence and is eventually consumed by detritivores, the factors that drive detritivore diet choice are pivotal to the flow of energy and materi- als through food webs. Here, we investigated the common salt marsh amphipod Gammarus palustris, which is a habitat specialist that feeds specifically on the dead leaves of its living host plant, salt marsh cordgrass Spartina alterniflora. Restricted use and consumption of dead S. alterniflora was reinforced by superior amphipod performance (survival, size, and sexual development) on dead S. alterniflora relative to other diets, and was driven at least in part by amphipods being physically able to feed on soft, decaying plant tissues but not live, turgid tissues. Stable isotopes from field surveys and laboratory assimilation assays suggest that amphipods also feed on S. alterniflora in the field, and that the important marsh fish Fundulus hetroclitus feeds on amphipods. Thus, consumption of G. palustris by F. heteroclitus may be an important trophic pathway linking cordgrass production to nearshore food webs. Importantly, direct isotopic analyses of amphipods and their known food sources demonstrated substantial deviation of observed fractionation factors from idealized stan- dards. This suggests caution when using idealized trophic shifts to describe food web linkages, and a renewed focus on assimilation assays to determine the realized fractionation of dietary isotopes.

Interactive effects of vegetation and sediment properties on erosion of salt marshes in the Northern Adriatic Sea

The lagoon landscape is characterized by a diversity of tidal morphologies, such as salt marshes, tidal flats and subtidal platforms, playing an essential role for the ecosystem services these areas provide. The existence of these low-lying morphologies depends on the delicate balance between site-specific bio-geo-morphodynamic processes and relative SLR. Tidal morphologies are at risk of survival since they must keep pace with sea level rise and land subsidence. Given the expected climate change scenario, it is important to identify the most threatened areas, where effective measures are urgently needed. This work presents a novel assessment of the vulnerability of tidal morphologies to relative sea-level rise, using as a study case the Venice Lagoon: the largest wetland in Italy and one of the most important coastal ecosystems of the Adriatic Sea, where the natural hydro-morphological setting is strongly influenced by anthropogenic interventions. Vulnerability is assessed for past, ongoing and future relative SLR conditions through an index-based approach that combines sensitivity and hazard maps generated using a series of indicators such as SLR, land subsidence, morphological setting, and stratigraphic characteristics of Holocene deposits. Results indicate that most of the lagoon area will be at moderate to severe vulnerability in the future, representing a significant worsening of conditions compared to the past. Although the expansion of subtidal areas is anticipated, this will be at the expense of intertidal areas, which will experience a significant and alarming decline. This change contributes to the flattening and deepening of the lagoon's topography, which in turn threatens the diversity of the landscape and is likely to lead to a decline in the ecosystem services provided by these tidal morphologies. The vulnerability maps provide a valuable tool to highlight the areas that need more attention, which can assist policymakers in developing restoration, conservation and mitigation plans. This work is part of the research program RESTORE (REconstruct subsurface heterogeneities and quantify sediment needs TO improve the REsilience of Venice saltmarshes), a PRIN 2022 PNRR project funded by the European Union &amp;#8211; NextGenerationEU.