1,721,075 research outputs found
Joint analysis of macrofaunal and meiofaunal assemblages improves the assessment of lagoonal environmental heterogeneity
No full textMatching datasets of macrofaunal and meiofaunal assemblages were jointly analyzed for the first time in a
coastal lagoon (Cabras Lagoon, Sardinia) in relation to the lagoonal environmental heterogeneity. Within the
common faunal list, indicator species/taxa for different environmental conditions were found evenly for both
assemblages, with the two faunal components responding distinctly to the putative environmental gradients
according to their autecology. The relationship between the number of individuals and species/taxa richness of
both assemblages showed an exponential increase at increasing salinity and DO concentrations in water as expected
basing on the confinement theory. Along the trophic gradient, the two metrics of both macrofaunal and
meiofaunal assemblages showed a similar belt-shaped curve in agreement with theoretical predictions and
quantitative field studies, with a peak at intermediate OM values followed by a sharp decrease at OM above 12%
at the most confined site. While not a causality measure, our results indicate that these simple benthic-OM relationships
applied to both faunal components represent a valuable screening-level indicator for evaluating the
likelihood of reduced sediment quality and associated bioeffects in eutrophic lagoons. The present study demonstrates
that macrofaunal and meiofaunal assemblages in coastal lagoons, as commonly shown in marine waters,
are coherent and distinct entities and that their joint use represents a more comprehensive and robust tool to
assess the environmental heterogeneity and quality of these highly variable systems
Meiofaunal Dynamics and Heterogeneity along Salinity and Trophic Gradients in a Mediterranean Transitional System
No full textThe spatiotemporal variation in meiofaunal assemblages were investigated for the first
time in the Cabras Lagoon, the largest transitional system in the Sardinian Island (W-Mediterranean
Sea). Two main environmental (salinity and trophic) gradients highlighted a significant separation
of the three study sites across the lagoon, which were consistent through time. The environmental
variability and habitat heterogeneity of the Cabras Lagoon influenced the meiofauna. In particular,
salinity and dissolved oxygen, primarily, shaped the meiofaunal assemblage structure at the seaward
site which was significantly dierent from both the riverine and the organically enriched sites. On the
other hand, the trophic components (e.g., organic matter, Chlorophyll-a, and phaeopigments) and the
dierent degrees of confinement and saprobity among sites were the secondary factors contributing
mostly to the separation between the latter two sites. The lack of significant dierences in the
temporal comparison of the meiofaunal assemblage structure along with the very low contribution
of temperature to the meiofaunal ordination indicated that this assemblage was more aected by
spatial rather than by temporal variation. This pattern was also supported by significant dierences
between the three sites in several univariate measures, including total number of individuals,
number of taxa, Pielou’s evenness, and the ratio between nematodes and copepods. Thus, the present
study corroborates the hypothesis that meiofaunal organisms are good indicators of the spatial
heterogeneity in transitional waters (TWs) and could have a greater species richness than that
expected. Indeed, the Cabras Lagoon overall showed one of the highest meiofaunal richness values
found from both Mediterranean and European TWs
Paradigm shifts in community ecology: Open versus closed units, challenges and limits of connectivity studies
Full text linkDue to the presence of the complex life cycles involving a benthic adult and a pelagic larval phase, the study of benthic community dynamics cannot ignore investigations of the processes occurring in the water column. Current investigations focus mainly on larval dispersal from an evolutionary and a biogeographic perspective, taking into account also population connectivity, conservation planning and coastal management. In the present paper we underline the need to improve knowledge of the main traits of marine invertebrate life cycles, highlighting the limits and challenges of current approaches. Firstly, we summarized the changing approaches within community studies, following the paradigm shifts found in recent marine ecological research, from supply-side ecology to connectivity, and involving the concepts of open and closed populations. Secondly, we analysed the main larval traits influencing dispersal, paying particular attention to pelagic larval duration in light of the few available data for connectivity studies. The difficulty in estimating many of the main traits of larval ecology make numerical simulation fundamental for a better understanding of the relationship between propagule dispersal and seawater dynamics, both being highly variable. We conclude that some essential biological information is still lacking for the proper integration of the modeling approaches. Thus it is necessary to further investigate the life-cycle traits and physiological and ecological characteristics of each species, an approach known as autecology or natural history. All too frequently modern ecologists ignore such reductionist approaches, although they are essential for a full understanding of processes, such as connectivity and metapopulation dynamics
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Abundance, Distribution, and Habitat Preference of Syngnathid Species in Sabaudia Lake (Tyrrhenian Sea)
Full text linkSyngnathids are considered flagship species of estuarine and coastal environments. However, most of the Mediterranean species are still classified as data-deficient (DD) at a global level according to the IUCN Red List of Threatened Species. In central Italy, several areas host potentially suitable habitats for syngnathids but have not been previously reported in the literature; the estimation of population parameters and habitat partitioning at these sites may help to assess their conservation status. In this study, we investigated the abundance, distribution, and habitat preferences of sympatric populations of Hippocampus hippocampus, H. guttulatus, Syngnathus abaster, and Nerophis ophidion in Sabaudia Lake (Tyrrhenian Sea, Italy). While confirming the primary importance of a healthy coastal habitat, we retrieved hints about species ecology and habitat use. The species distribution in the study area highlights the role of habitat complexity in supporting local populations of these sensitive species
Note sulle capacità di biorisanamento da metalli pesanti in due filtratori mediterranei
No full textThe aim of the study is to compare the heavy metals bioremediation capacity of two Mediterranean filter-feeders: the sponge Ircinia sp. and the ascidian Styela plicata (Lesueur, 1823). The analytical measurements have been performed by applying the technique of anodic stripping voltammetry (ASV) and by using the innovative miniaturized bismuth-based sensor. The results confirm that both organisms show a remarkable heavy metals bioaccumulation capacity. Furthermore, it turned out that the sponge Ircinia sp. has greater bioremediation potential than S. plicata
A Vermetid Bioconstruction at the Adriatic Coast of Apulia (Italy)
No full textThis study presents the first comprehensive data on a vermetid formation along the Apulian coast of the Adriatic Sea, representing one of the northernmost records in the Mediterranean. Surveys along the Brindisi coastline employed visual inspection to map the bioconstruction's distribution and extension. Detailed data on the bioconstruction inner and the outer edge length, thickness, width, slope and topographic complexity were collected at three selected sites. Moreover, photographic replicates were used to assess shell aperture density and diameters of Dendropoma sp. Associated fauna was studied using two quantitative sampling squares in each transect. The results showed that the vermetid bioconstruction consisted of a thin, encrusted monolayer (thickness < 1.5 cm) that extended for 3.273 linear kilometers, covering 17.23% of the investigated area; it had an average width of 0.5 m, with a mean density of Dendropoma sp. at 2.52 ind/cm(2). The associated fauna was composed of 47 taxa dominated by crustaceans, mollusks and annelids. Species richness was correlated with the bioconstruction's thickness and complexity. These findings underline the ecological importance of vermetid bioconstructions as biodiversity hotspots. The lack of massive mortality events along the Apulian coast, in contrast to other Mediterranean vermetid bioconstructions, underscores the necessity for targeted conservation measures
Uso combinato dei tratti funzionali e tassonomici per la valutazione della qualità ecologica negli ambienti di transizione del Mediterraneo
No full textLe lagune costiere sono ambienti di transizione caratterizzati da grandi fluttuazioni ambientali che possono fortemente incidere sulle associazioni bentoniche. La nematofauna è una componente fondamentale di questi ambienti dove può raggiungere anche notevoli livelli di densità. Nonostante ciò, sono pochissimi gli studi in aree di transizione del Mediterraneo. È per questo che è stato condotto uno studio sulla nematofauna della laguna di Cabras, il più grande sistema lagunare della Sardegna. Ad essere analizzati non sono stati solo gli aspetti tassonomici della comunità (composizione, struttura, diversità alpha), ma anche i più comuni tratti funzionali (strategie di vita e gruppi trofici). Questo al fine di valutare quali aspetti della comunità siano maggiormente condizionati dalle condizioni ambientali lungo il gradiente spaziale della laguna nei due periodi analizzati (estate 2010 e inverno 2011). La struttura tassonomica si è conferma lo strumento più sensibile per documentare le modificazioni della comunità apparendo significativamente condizionata sia spazialmente che temporalmente. Il grado di confinamento e dell'arricchimento organico erano i fattori primari che incidevano sulla composizione tassonomica, biodiversità e i tratti funzionali della nematofauna. Unica eccezione era l'indice di maturità (MI), un indice basato sulle strategie di vita dei nematodi che ha mostrato valori complessivamente uniformi in tutta la laguna. La mancanza di variazioni di questo indice è piuttosto interessante in quanto corroborerebbe l'idea che i nematodi di questi corpi d’acqua siano profondamente adattati ad un ambiente dinamico e caratterizzato da naturali ed a volte estreme fluttuazioni ambientali rendendo incapace l’indice di documentare, se utilizzato da solo, cambiamenti ambientali. Quando è stata analizzata la qualità ecologica dei sedimenti di Cabras, i descrittori della nematofauna (H’, MI e percetuale di taxa a strategia r o k) hanno evidenziato una qualità da cattiva (nei siti più interni) a scadente (nel sito prossimo al mare). Il confronto di questi risultati con quelli ottenuti da studi precedenti sugli indici biotici della macrofauna (es. BENTIX, M-AMBI e M-bAMBI MAGNI et al. 2023) nella stessa area di studio, ha mostrato andamenti del tutto simili, evidenziando un complessivo buon livello di bioindicazione dei nematodi
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