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We examine the potential of trait-based parameters of taxa for linking above-ground and belowground ecological networks (hereafter ‘green’ and ‘brown’ worlds) to understand and predict community dynamics. This synthesis considers carbon, nitrogen and phosphorus-related traits, the abundance of component species and their size-distribution across trophic levels under different forms of management. We have analyzed existing and novel databases on plants, microbes and invertebrates that combine physico-chemical and biological information from (agro)ecosystems spanning the globe. We found (1) evidence that traits from above-ground and below-ground systems may be integrated in the same model and (2) a much greater than expected stoichiometric plasticity of plants and microbes which has implications for the entire food-web mass-abundance scaling. Nitrogen and phosphorus are primary basal resources (hence, drivers) and more retranslocation of P than of N from leaves will lead to higher N:P in the litter and soil organic matter. Thus, under nutrient-rich conditions, higher foliar concentrations of N and P are reflected by lower N:P in the brown litter, suggesting less P retranslocated than N. This apparent stoichiometric dichotomy between green and brown could result in shifts in threshold elemental ratios critical for ecosystem functioning. It has important implications for a general food-web model, given that resource C:N:P ratios are generally assumed to reflect environmental C:N:P ratios. We also provide the first evidence for large-scale allometric changes according to the stoichiometry of agroecosystems. Finally, we discuss insights that can be gained from integrating carbon and nitrogen isotope data into trait-based approaches, and address the origin of changes in Δ13C and Δ15N fractionation values in relation to consumer-resource body-mass ratios

The high numbers of primary producers represent multiple sources of organic matter accumulating onto lake bottoms. The difficulty of distinguishing the relative contribution to the mixture presents considerable challenges to the analysis of these organic deposits. In this study, dual-stable isotope analysis and IsoSource model were used to identify allochthonous and autochthonous components of detritus deposits (Particulate Organic Matter: POM) at two different bottom slope sites of a volcanic lake (lake Bracciano). Experiments were carried out to calibrate IsoSource on constructed plant mixtures and assess changes in isotope ratios during plant decomposition. IsoSource satisfactorily discriminated the constructed mixture sources with a few exceptions. Changes in isotopic enrichment during decomposition were low, and thus did not represent a confounding variable in the isotopic analysis. By contrast, chemical and geological differences of the study sites were associated with differences in plant δ13C and δ15N values (more than 2‰ within single plant species). At both sites, the isotopic signals of POM fell between polygons delineated by source end members with an evident shift of δ13C toward allochthonous sources. POM amount and diversity were greater at the flatter bottom site, where allochthonous contributions were larger than at the other site. In particular, IsoSource ranked species contributions as follows: A. glutinosa > P. australis > A. donax > S. alba > P. nigra > the benthic macroalga Chara sp. at the first site, and A. glutinosa > P. nigra > the aquatic macrophyte C. demersum at the latter. The composition of littoral POM was determined by allochthonous sources in proportion to their relative abundances (as percent land cover) with differences between sites due to bottom slope.

An exclosure experiment was carried out in the reed-dominated littoral zone of a volcanic lake (Lake Vico, central Italy) to test whether the impact of predatory fish on benthic invertebrates cascades on fungal colonisation and breakdown of leaf detritus. The abundance, biomass, and Shannon diversity index of the invertebrate assemblage colonising Phragmites australis leaf packs placed inside: (1) full-exclosure cages, (2) cages allowing access only to small-sized fish predators, and (3) cageless controls, were monitored over a 45-day period together with the mass loss and associated fungal biomass of leaf packs. The species composition of the fungal assemblage was further assessed at the end of the manipulation. In general, invertebrate predators did not show any significant response to fish exclusion, either on a trophic guild or on a single taxon level. In contrast, the exclusion of large predatory fish induced a diverse spectrum of changes in the abundance and population size-structure of dominant detritivore taxa, ultimately increasing the biomass and Shannon diversity index of the whole detritivorous guild. These changes corresponded with significant variations in leaf detritus decay rates as well as in the biomass and assemblage structure of associated fungal colonisers. Our experimental findings provide evidence that in Lake Vico effects of fish predators on invertebrate detritivores influence the fungal conditioning and breakdown of the detrital substrate. We conclude that in lacustrine littoral zones predator-driven constraints may structure lower trophic levels of detritus-based food webs and affect the decomposition of leaf detritus originated from the riparian vegetation.

In this work we propose a review of researches developed in recent years by statisticians and biologists working on lagoons and coastal areas. We briefly illustrate the use of: (1) spatial statistical tools to fill gaps in the data, (2) linear models (LM’s) and GAM’s to investigate the relationships between food web metrics and environmental variables, (3) LM’s, GAM’s, GAMM’s and linear mixed models to investigate the relationships between ecological multimetric indices and environmental parameters and (4) a model based approach for the classification of the ecological status of lagoons. Points (1) and (2) have been developed in collaboration with the Environmental Biology department in Rome, based on data from an aquatic ecosystem in South Sardinia, in order to address two questions: to what extent the effect of disturbance in the terrestrial landscape spreads through the nearest aquatic ecosystem? Which aquatic community metric is more suitable to indicate the propagation distance of terrestrial disturbance? The other two topics come from the collaboration with Environmental Biology department at university of Salento, working on the classification of the ecological status of Mediterranean and Black Sea lagoons. Here the goal is to understand the behaviour and classification ability of multimetric indices (MAMBI, AMBI, BAT, BITS and ISS). In (4) we try to solve the disagreement often encoutered among alternative lagoon classifications, proposing a joint Bayesian hierarchical model for four multimetric indices, based on multivariate normal mixtures. In this model each mixture component is estimated as a function of covariates of interest and corresponds to an ecological status.

We investigated whether predatory fish exert a top-down control on reed leaf packs processing in a lake littoral zone through a trophic cascade. Exclosure experiments were repeated in summer and winter, under high and low natural fish abundance, respectively. Fish exclusion effects on detritus processing and fungal conditioning were consistent with trophic cascade predictions only in summer. In winter, however, results indicated that a trophic cascade was induced by predatory invertebrates. In both seasons, variations in detritivores abundance generally supported a cascade scenario, whereas several taxon-specific departures occurred during the experimental periods. We conclude suggesting that predators may continuously regulate leaf detritus processing in lake littoral zones, through a seasonal shift in the relative contribution of fish and invertebrate predation.

Sediment biotic and abiotic attributes were determined during the PRISMA II oceanographic campaigns in the northern and central Adriatic Sea. The radiotracer orthophosphate 32 P was used under laboratory conditions to analyse the role of micro- and macrofauna in phosphorus dynamics at the water-sediment interface. Effects of infaunal suspensivores on microfungal growth were also investigated. Our findings emphasised: 1) significant differences in sediment 32 P uptake as related to the sampling area, occurrence of the pelagic frontal system, sediment grain size, microbial activity, and anoxia; 2) the crucial role played in 32 P dynamics by different tropho-functional groups r - r i.e ., infaunal filter-feeders and epifaunal detritivore characterising the benthic community of the northern Adriatic basin. The significant changes in ergosterol concentration (adopted as an index of microfungal growth) observed in sediments subjected to infaunal activity, eventually provided a comprehensive insight into macrofauna-microorganism interactions. The potential impact of macrofaunal activity in phosphorus dynamics in the Adriatic benthic system is discussed

Core samples were examined quarterly at two coastal sites (S1 and S2) and at an offshore station (S3) located in the Po River delta area (northwestern Adriatic Sea). Analyses focused on (i) occurrence of coarse detritus of allochthonous origin in the sedimentary matrix and (ii) the relative influence of macrodetritus enrichment and other environmental factors on the vagile macrofauna. Plant debris occurred in site S1 sediments only in summer and autumn; in contrast, fragments of the phanerogams Cymodocea nodosa and Zostera spp. were found in site S2 sediment throughout the sampling period. Sediments from the offshore site S3 were characterized by negligible plant material, even though in summer and autumn samples debris of continental origin was observed. Even though leaf detritus occurrence at site S2 was ∼5-fold higher compared to the other coastal site S1, it did not influence the total organic matter and its distribution among grain-size classes. Conversely, the specific organic content of dimensional fractions provided an effective assessment of detritus enrichment processes occurring at the two coastal sites. A group of brackish-originated crustaceans (i.e. the amphipods Gammarus insensibilis and G. aequicauda and the isopod Idotea baltica ) was the main determinant of among-site multivariate differences in the vagile macrofauna; depositivorous ophiuroids accounted for the residual differences observed during the study period. The analysis of taxa abundance and individual body size indicated that in both site S1 and S3 macrodetritus advection to the benthic system corresponded with passive dispersal of brackish crustaceans, that provided a negligible contribution to the macrobenthic production. In contrast, in site S2 allochthonous inputs from marginal environments could have represented the key factor for the persistence of an authochthonous population of Gammarus insensibilis . The amphipod provided a considerable (19·4%) contribution to the total macrobenthic production of the site, dominated by filter-feeding bivalves and tubicolous deposit feeders. The potential effects of detritivorous crustaceans on soft-bottom macrobenthic assemblages of the northern Adriatic Sea are discussed.

In the Lesina Lagoon (southern Italy), three species of crustacean mesograzers - the isopods Idotea baltica Pallas and Sphaeroma serratum Fabricius, and the amphipod Gammarus insensibilis Stock - dominate the epifaunal assemblage associated with the Rhodophyta Gracilaria verrucosa (Hudson) Papenfuss. We examined in laboratory feeding assays the palatability of the red macroalga to each of the three mesograzer species. Furthermore, we used a cage experiment to investigate the actual impact of the mesograzer assemblage on the growth of Gracilaria under field conditions. Cages with different mesh sizes were used to test the hypothesis that mesograzer effect on the macroalga is size dependent. Laboratory assays indicated for all the mesograzer species a negative effect on Gracilaria; in particular, I. baltica and G. insensibilis actively consumed the macroalga, whereas S. serratum grazing activity was weaker but nonetheless statistically significant. In contrast, Gracilaria was not significantly grazed under field conditions. When mesograzers were totally excluded, algal growth showed a strong negative variation compared to controls where access was not precluded (ca. 43% reduction in wet mass). Simultaneously, the abundance of the encrusting bryozoan Conopeum seurati increased significantly (from 1.5 to 24.7 mg g-1, corresponding to 1.7% and 28.9% cover of algal surface); an analogous increase was detected in the abundance of other sessile macrofauna (i.e. the bivalve Mytilaster marioni). When only juvenile, small-sized epifauna were given access to Gracilaria, algal mass change was reduced by around 36%. The abundance of both encrusting bryozoans and sessile bivalves showed significant positive variations, close to those observed in the total exclusion treatment. Our results suggest that, even though Gracilaria represents a potentially palatable resource for mesograzers in the Lesina Lagoon, the actual impact of epifauna on the macroalga might be beneficial, through an indirect control on the development of fouling epibionts. In addition, such a positive effect may be size specific, since the juvenile, small-sized component of the mesograzer assemblage exerted a significantly weaker control on fouling development, even at unnaturally high densities. We suggest that the occurrence of different functional roles among mesograzer size classes might represent a significant controlling factor for the establishment of mesograzer-epibiont-host plant interactions, and for their effects on macrophytal productivity