Search results for "Pact"
showing 10 items of 2355 documents
Stable carbon and nitrogen ratios in the sand smelt from a Mediterranean coastal area: Feeding habits and effect of season and size
2002
Enriched (δ13C values (annual average - 11·2%) suggest that in the study site (Stagnone di Marsala, Italy) the sand smelt Atherina boyeri exploited benthic prey throughout the year. In particular, Mysidacea and Isopoda seemed to dominate the diet. Stomach content data from the literature was in partial agreement with the present isotopic analysis suggesting that, while Mysidacea and Isopoda are exploited by A. boyeri, Copepoda Harpacticoida and Amphipoda are the dominant food items of the sand smelt diet. Several hypotheses are proposed to explain such partially different results from the two techniques. Both season and size influenced the δ13C and δ15N values of A. boyeri. Although through…
Scuba diver behaviour and its effects on the biota of a Mediterranean marine protected area
2009
The effects of diving activity in different Mediterranean subtidal habitats are scarcely known. This study evaluates diver behaviour (for example time spent in each habitat), use (contacts made with the substrate) and immediate effects of diver contact on benthic species in a marine protected area (MPA) in Sicily. Over a two-year period, intentions of 105 divers were observed within seven subtidal habitats: algae on horizontal substrate, algae on vertical substrate, Posidonia oceanica, encrusted walls, caves, sand and pebbles. Divers selected a habitat in proportion to its availability along the scuba trail. On average, each diver made 2.52 contacts every seven minutes, and no differences w…
Leaf vs. epiphyte nitrogen uptake in a nutrient enriched Mediterranean seagrass (Posidonia oceanica) meadow
2012
Abstract In situ nitrogen uptake by leaves and epiphytes was studied in a Mediterranean seagrass (Posidonia oceanica) meadow impacted from a fish farm and a pristine meadow, using 15NH4 and 15NO3 as tracers. In the impacted meadow both leaves and epiphytes yielded higher N concentrations and showed higher specific N uptake, suggesting a linkage between N uptake and its accumulation. Epiphytes took up N faster than leaves in relation to their corresponding biomass, but when assessed per unit area, N uptake was higher in leaves. Leaf N uptake was negatively correlated with epiphyte N uptake. With increasing epiphyte load on leaves, N leaf uptake decreased while N epiphyte uptake increased, in…
Effect of boat noise on the behaviour of bluefin tuna Thunnus thynnus in the Mediterranean Sea
2007
The effect of boat noise on the behaviour of bluefin tuna Thunnus thynnus was investi- gated in the Egadi Islands, Sicily, during spring 2005 using a fixed tuna trap set near shipping routes. Tuna behaviour was observed when exposed to both natural ambient sound and sound generated by hydrofoil passenger ferries, small boats and large car ferries. Acoustical and behavioural analyses were conducted with and without extraneous sound to define a list of behavioural categories. Each vessel produced different engine sounds with regard to their composition and bandwidth, and all were distinctly different from ambient sound levels. In the absence of boat noise, tuna assumed a con- centrated coordi…
Towards a landscape scale management of pesticides: ERA using changes in modelled occupancy and abundance to assess long-term population impacts of p…
2015
Pesticides are regulated in Europe and this process includes an environmental risk assessment (ERA) for nontarget arthropods (NTA). Traditionally a non-spatial or field trial assessment is used. In this study we exemplify the introduction of a spatial context to the ERA as well as suggest a way in which the results of complex models, necessary for proper inclusion of spatial aspects in the ERA, can be presented and evaluated easily using abundance and occupancy ratios (AOR). We used an agent-based simulation system and an existing model for a wide-spread carabid beetle (Bembidion lampros), to evaluate the impact of a fictitious highly-toxic pesticide on population density and the distributi…
Individual and population-scale carbon and nitrogen isotopic values of Procambarus clarkii in invaded freshwater ecosystems
2022
Este artículo contiene 16 páginas, 1 figura, 1 tablas.
Developing a scuba trail vulnerability index (STVI): a case study from a Mediterranean MPA
2008
Scuba diving is now one of the major form of commercial use of marine protected areas (MPAs) around the world and the control of its potential impacts on the marine environment represents a fundamental key to manage this recreational activity in highly dived areas. A potential tool to tackle such issues has been thought to be the definition of a value of recreational carrying capacity of an area, but this approach has been rarely considered management-effective. Therefore, the first step for effectively managing scuba-diving should be ‘bottom-up’: characterizing the benthic communities potentially affected by diving and evaluating their vulnerability. Aim of this paper is to propose a tool …
Stable isotope evidence for the environmental impact of a land-based fish farm in the western Mediterranean
2004
Isotopic examination (delta(13)C and delta(15)N) of organic matter sources and consumers was used to assess the impact and trace the dispersal of wastewater from a land-based fish farm in western Mediterranean. The results provide evidence of the non-negligible effect of aquaculture facilities on the natural stable isotopic composition of organisms. Aquaculture waste entered the food web, altering the natural isotopic composition of organic matter sources at the base and the upper trophic levels. Nitrogen-rich fish waste mainly affected delta(15)N values, while delta(13)C showed less alteration. Waste seemed to disperse widely enough to affect the isotopic composition at the study site abou…
Effects of fish-farm biodeposition on periphyton assemblages on artificial substrates in the southern Tyrrhenian Sea (Gulf of Castellammare, Sicily)
2007
An algal assemblage growing on artificial substrata of fish-farm cages was investigated. Specifically, algal response to the effects of fish-farm facilities was studied, in order to identify a possible future descriptor of biodeposition impact. Some sites were positioned upstream of the farms (at least 750 m; ‘controls’) and other sites were positioned downstream of the farms (‘impacts’). All sites were situated in the Tyrrhenian Sea. Control and impact sites differed significantly with regard to the dissolved nutrient profile. The fouling community (samples were scraped from buoys) displayed a reduction gradient in diversity which increased with the effect of fish farms. A total of 51 taxa…
Nematode community response to fish-farm impact in the western Mediterranean.
2002
A previous investigation on fish-farm biodeposition effects on benthos, carried out in the Gaeta Gulf (northwestern Mediterranean Sea), revealed a strong impact on meiofaunal assemblages. This study implements these findings by examining in detail the nematode assemblage and its response to organic enrichment from the start of a fish farm activity to the conclusion of the fish rearing cycle. Density, community structure and individual size were utilised for univariate (genus, trophic diversity and abundance patterns) and multivariate analyses (MDS) in order to identify the best descriptors of impact and the response of the nematode assemblages. Nematodes displayed significantly reduced dens…