Autochthonous and allochthonous plant contributions to coastal benthic detritus deposits: a dual-stable isotope study in a volcanic lake

WIT Transactions on Ecology and the Environment

et al. 2017

Self Cite

The lakes in the Italian region of Lazio, and in particular Lake Bracciano, have suffered due to reduced rainfall during the most recent years (1264.8 mm in 2014 vs 308.4 mm in 2015 and 883.6 mm in 2016 in Lake Bracciano). Moreover, Lake Bracciano exhibits both a direct water withdrawal (as drinkable water for the city of Rome and several other towns), and an indirect one, by the groundwaters, for agriculture. The 1.5 m water reduction, never observed in the last two decades, bared over 10 m of the littoral zone with the consequent exposition of gravel shores, trashes and reduction of the bottom areas involved in the denitrification process. This condition poses a threat to the ecosystem and to the human profits in term of eutrophication, healthy water loss, ship handling difficulties, touristic boats included, and tourism decline. In a previous investigation, we sampled the epilithic algae in the littoral zone of Lake Bracciano and estimated their nitrogen isotopic signature (δ 15 N). We highlighted the presence of diffuse organic and inorganic nitrogen inputs not intercepted by the wastewater collection system. These inputs, in synergy with water-level reduction, are able to undermine the ecosystem structure and health. In this paper, we show the nitrogen isotopic signatures, and their sources, as euros gained by parking meters for non-residents. We highlight the role of the touristic pressure not intercepted by the wastewater treatment plant in terms of δ 15 N increase during the most critical season (i.e. summer). The results show strong increases of euros gained and consequent δ 15 N signature increases (9‰ < δ 15 N < 17‰) from the end of June to the middle of August. We provide evidence supporting the need to adopt management policies to preserve the ecosystem services and related human health and earnings.

Section: Resultsmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lake Water Quality for Human Use and Tourism in Central Italy (Rome)

Calizza

Fiorentino

WIT Transactions on Ecology and the Environment

et al. 2017

Self Cite

Diet composition of the Italian crested newt (Triturus carnifex) in structurally different artificial ponds based on stomach contents and stable isotope analyses

Carlini

Romano

et al. 2020

Aquatic Conservation

In order to evaluate the effects of ecological disturbances, such as climate change, human‐induced habitat modification, or species introduction, and in order to adopt appropriate management policies for their conservation, knowledge of the trophic ecology of protected or threatened species is crucial. The Italian crested newt, Triturus carnifex (Laurenti, 1768), is listed in annexes II and IV of the European Habitats Directive. For this species, changes in water quality and habitat loss represent major threats, potentially impairing its breeding and feeding activities. Artificial aquatic habitats, such as cattle‐drinking pools, represent valuable refuges and suitable breeding sites for T. carnifex. The aim of this study was to determine the food niche of the Italian crested newt in these habitats, evaluating its prey selection strategy in relation to a range of environmental conditions and differing availability of resources. Stomach contents (indicative of short‐term diet) and δ13C and δ15N signatures of tails (indicative of medium‐term diet) of adult newts from three artificial ponds in central Italy, where traditional silvo‐pastoral activities are still important, were determined. Potential prey were also sampled and processed for stable isotope analysis. Triturus carnifex, similar to other newt species, is an opportunistic predator, feeding on a wide variety of prey that includes terrestrial and aquatic macroinvertebrates. In particular, the opportunistic use of temporally available small zooplankton was identified from stomach contents analysis. Conversely, stable isotope analysis highlighted the consumption of larger, soft‐bodied prey that the stomach‐contents‐based approach underestimated. These included terrestrial oligochaetes, which turned out to be the most important and energy‐rich food source in the medium term. These results emphasize the usefulness of combined approaches for studying the trophic ecology of salamanders and also highlight the importance of the integrated management of aquatic breeding habitats and neighbouring terrestrial habitats, as sources of food, for newt conservation.

Effect of habitat degradation on competition, carrying capacity, and species assemblage stability

Calizza

Costantini

et al. 2017

Ecology and Evolution

Self Cite

Changes in species’ trophic niches due to habitat degradation can affect intra‐ and interspecific competition, with implications for biodiversity persistence. Difficulties of measuring species’ interactions in the field limit our comprehension of competition outcomes along disturbance gradients. Thus, information on how habitat degradation can destabilize food webs is scarce, hindering predictions regarding responses of multispecies systems to environmental changes. Seagrass ecosystems are undergoing degradation. We address effects of Posidonia oceanica coverage reduction on the trophic organization of a macroinvertebrate community in the Tyrrhenian Sea (Italy), hypothesizing increased trophic generalism, niche overlap among species and thus competition and decreased community stability due to degraded conditions. Census data, isotopic analysis, and Bayesian mixing models were used to quantify the trophic niches of three abundant invertebrate species, and intra‐ and interspecific isotopic and resource‐use similarity across locations differing in seagrass coverage. This allowed the computation of (1) competition strength, with respect to each other and remaining less abundant species and (2) habitat carrying capacity. To explore effects of the spatial scale on the interactions, we considered both individual locations and the entire study area (“‘meadow scale”). We observed that community stability and habitat carrying capacity decreased as P. oceanica coverage declined, whereas niche width, similarity of resource use and interspecific competition strength between species increased. Competition was stronger, and stability lower, at the meadow scale than at the location scale. Indirect effects of competition and the spatial compartmentalization of species interactions increased stability. Results emphasized the importance of trophic niche modifications for understanding effects of habitat loss on biodiversity persistence. Calculation of competition coefficients based on isotopic distances is a promising tool for describing competitive interactions in real communities, potentially extendible to any subset of ecological niche axes for which specimens’ positions and pairwise distances can be obtained.