Giuseppe Castaldelli

Impact of Tapes philippinarum farming on nutrient dynamics and benthic respiration in the Sacca di Goro

AbstractThe introduction of the short-necked clam Tapes philippinarum into the Sacca di Goro has over a short period made this coastal environment one of the top European clam production sites. In recent years, this activity has been seriously impacted due to the appearance in the lagoon of large macroalgal beds and the occurrence of dystrophic events causing anoxia and massive deaths of molluscs in the cultivated areas. Tapes cultivation sites now cover more than one third of the lagoon surface at densities sometimes attaining 2000–2500 adult individuals m−2; such densities and the harvesting methods, based on sediment dredging, probably have a strong impact on the benthic system. Whilst a number of studies have reported water–sediment interface induced modifications due to oyster or mussel farming there have been few attempts to quantify how clam farming affects biogeochemical cycles of oxygen and nutrients, in particular in the Sacca di Goro. Two areas, a farmed and a control one, were compared for benthic fluxes and results were correlated with clam biomass. Oxygen, carbon dioxide, ammonium, reactive silica and phosphorus fluxes were stimulated several fold by the presence of Tapes due to the clams, respiration and excretion activities, but also to the reducing conditions in the surface sediments. On average, the whole lagoon dark sediment O2 demand and CO2 production were stimulated by a factor of, respectively, 1.8 and 3.3, whilst nutrient release was 6.5 times higher for NH4+ and 4.6 times higher for PO43-. Our results indicate that clam farmers should carefully consider sustainable densities of Tapes in order to prevent the risk of sediment and water anoxia. Rapid nutrient recycling (up to 4000 μmol NH4+ m−2 h−1 and 150 μmol PO43- m−2 h−1) stimulated by the high biodegradability of clam faeces and pseudofaeces could in turn favour macroalgal growth.

Intestinal immune response of Silurus glanis and Barbus barbus naturally infected with Pomphorhynchus laevis (Acanthocephala).

Immunopathological and ultrastructural studies were conducted on the intestine of barbel Barbus barbus and sheatfish Silurus glanis that were naturally infected with the acanthocephalan Pomphorhynchus laevis. Enteric helminths often cause inflammation of the digestive tract, inducing the recruitment of different types of immune cells at the site of infection. The results of our study clearly demonstrated that mast cells (MC) were the dominant immune cells which occur at the site of inflammation in both hosts. MC were associated with fibroblasts and were found in close proximity to, and inside, the capillaries of the intestine, thus, migration of mast cells via the bloodstream was suggested. Significant degranulation of MC was present. Immunohistochemical staining revealed met‐enkephalin and serotonin (5‐HT) in intestinal MC of both uninfected and infected barbel and the absence of the antimicrobial peptides piscidin 3 and piscidin 4 in both species. Data are discussed with respect to host immune response to an intestinal helminth and compared with other host‐parasite systems.

Proliferative cell nuclear antigen (PCNA) expression in the intestine of Salmo trutta trutta naturally infected with an acanthocephalan

BackgroundChanges in the production of proliferating cell nuclear antigen (PCNA), a 36 kd protein involved in protein synthesis, within intestinal epithelia can provide an early indication of deviations to normal functioning. Inhibition or stimulation of cell proliferation and PCNA can be determined through immunohistochemical staining of intestinal tissue. Changes in the expression of PCNA act as an early warning system of changes to the gut and this application has not been applied to the fields of aquatic parasitology and fish health. The current study set out to determine whether a population of wild brown trout, Salmo trutta trutta (L.) harbouring an infection of the acanthocephalan Dentitruncus truttae Sinzar, 1955 collected from Lake Piediluco in Central Italy also effected changes in the expression of PCNA.MethodsA total of 29 brown trout were investigated, 19 of which (i.e. 65.5%) were found to harbour acanthocephalans (5–320 worms fish-1). Histological sections of both uninfected and infected intestinal material were immunostained for PCNA.ResultsThe expression of PCNA was observed in the epithelial cells in the intestinal crypts and within the mast cells and fibroblasts in the submucosa layer which is consistent with its role in cell proliferation and DNA synthesis. The number of PCNA-positive cells in both the intestinal epithelium and the submucosa layer in regions close to the point of parasite attachment were significantly higher than the number observed in uninfected individuals and in infected individuals in zones at least 0.7 cm from the point of parasite attachment (ANOVA, p < 0.05).ConclusionsAn infection of the acanthocephalan D. truttae within the intestinal tract of S. t. trutta effected a significant increase in the number of PCNA positive cells (mast cells and fibroblasts) at the site of parasite attachment when compared to the number of positive cells found in uninfected conspecifics and in tissue zones away from the point of parasite attachment.

Decomposition dynamics of the bloom forming macroalga Ulva rigida C. Agardh determined using a 14C-carbon radio-tracer technique.

Abstract The short-term decomposition dynamics of Ulva rigida C. Agardh by a natural bacterial consortium were studied in the laboratory using a 14 C radio-tracer technique. Following an initial rapid loss of approximately 15% of the particulate organic carbon (POC) by leaching of dissolved organic carbon (DOC), there was an exponential loss of POC and an accompanying increase in the labelling of the inorganic carbon (IC) pool. However, losses of labelled POC were significantly greater than the summed accumulation of radiolabel in the IC and DOC pools over the course of the experiments. We propose that this discrepancy may be due to the production of volatile organic compounds (VOC) during decomposition, which were stripped from the medium during the extraction of IC, by acidification and sparging with helium, but were not retained by the KOH traps for IC. The compatible solute dimethylsulphonioproprionate (DMSP) which is accumulated to high concentrations by Ulva spp. and is metabolised by bacteria to volatile dimethylsulphide (DMS) and potentially methane, could be one of the major sources of VOCs during our incubations. Modelled decomposition rates based on the loss of label from the particulate fraction were high, with calculated half times of 8.1 and 7.6 days. However, these rates greatly overestimate true mineralisation rates, since only approximately 50% of the label lost from the POC pool was recovered as IC. Overall these data indicate that previously determined decomposition rates based on loss of dry weight of macroagal biomasses would also greatly overestimate carbon mineralisation rates and hence the oxygen demand for this mineralisation. This aspect may be particularly important for environmental management or modelling of bloom impacted environments, since the most severe impacts of macroalgal blooms are mediated by the hypoxic or anoxic conditions induced when the blooms collapse and hence are strictly related to the oxygen demand for mineralisation of the macroalgal biomasses.

Linking dissolved organic carbon, acetate and denitrification in agricultural soils

This study focuses on the factors affecting nitrate removal via microbial denitrification in agricultural soils, and particularly on the quantity and quality of dissolved organic carbon. To assess the relationship among dissolved organic carbon, nitrate and low molecular weight organic acids (acetate and formate), grids of ceramic suction cups were established in the four most representative soil types of the lower Po River floodplain, cropped with maize. Results highlighted a direct relation between acetate and dissolved organic carbon in all sites. The best fit was obtained in soils were the main source of organic carbon was the maize residues. By comparing dissolved organic carbon and acetate versus nitrate concentration revealed that acetate can be used as a better proxy for denitrification in the field with respect to dissolved organic carbon.

Assessment of the Intrinsic Vulnerability of Agricultural Land to Water and Nitrogen Losses via Deterministic Approach and Regression Analysis

A set of indices was developed in order to classify the vulnerability of agricultural land to water and nitrogen losses (LOS), setting a basis for the integrated water resources management in agricultural systems. To calibrate the indices using multiple regression analysis, the simulation results of Groundwater Loading Effects of Agricultural Management Systems (GLEAMS) model for combinations of different soil properties, topography, and climatic conditions of a reference field crop were used as “observed values.” GLEAMS quantified (1) the annual losses of the percolated water beneath the root zone, (2) the annual losses of the surface runoff, (3) the annual losses of the nitrogen leaching beneath the root zone, and (4) the annual losses of nitrogen through the surface runoff, which were used to calibrate the following indices LOSW-P, LOSW-R, LOSN-PN, and LOSN-RN, respectively. All the simulations to gain the LOS indices were carried out for the same reference field crop, the same nitrogen fertilization, and the same irrigation practice, in order to obtain the intrinsic vulnerability of agricultural land to water and nitrogen losses. The LOS indices were also combined to derive nitrogen concentrations in the percolated and in the runoff water. Finally, the connection of LOS indices with the groundwater was performed using an additional equation, which determines the minimum transit time of the percolated water to reach the groundwater table.

Infiltration and activation of acidophilic granulocytes in skin lesions of gilthead seabream, Sparus aurata, naturally infected with lymphocystis disease virus.

Light, ultrastructural and immunocytochemical investigations were carried out on the skin of gilthead seabream, Sparus aurata L., naturally infected with lymphocystis iridovirus, to assess pathology and host cellular responses. Of 220,000 young seabream examined, 32,400 (14.7%) had clinical signs of lymphocystis and within 6 months of disease appearance, 45% of clinically affected fish had died. A subsample of 20 S. aurata (80.0 ± 12.5mm total length, mean ± S.D.), including 10 with lymphocystis on the skin and 10 clinically normal, were examined via immunohistochemistry. Affected skin displayed macroscopic, wart-like clusters of hypertrophic fibroblasts which arose from the dermis and were covered by the epithelium. Clusters were encountered on the head, trunk and fins, but there was no evidence of visceral lymphocystis. The lymphocysts were surrounded by numerous granular cells that were positive for the antimicrobial peptide (AMP) piscidin 3 and underwent intense degranulation. To identify the type of granular cells involved in this viral disease, a double immunohistochemical staining with the monoclonal antibody G7 (mAb G7), which is specific for seabream acidophilic granulocytes (AGs), and with anti-histamine (as a marker for mast cells, MCs) was applied to the skin sections of the 10 clinically normal fish and 10 fish with lymphocystis. In infected skin, the number of G7-positive cells (i.e., AGs) (18.5 ± 10.5, mean number of cells per 20,000 μm(2) ± S.D.) was significantly higher compared to their density in uninfected skin (1.4 ± 2.2) (t test, p<0.01). Notably, the AGs that infiltrated the skin lesions of infected animals were found to be degranulated and to produce the pro-inflammatory cytokine interleukin-1β. No histamine-positive granular cells (i.e., MCs) were encountered in the lymphocystis lesions. The present study shows the response of skin to lymphocystis disease virus (LCDV) and provides evidence that AGs, but not MCs, are recruited and activated in response to this skin infection.

Impact of commercial clam harvesting on water column and sediment physicochemical characteristics and macrobenthic community structure in a lagoon (Sacca di Goro) of the Po River Delta

The Sacca di Goro is a hypertrophic lagoon of the Po river Delta, which is heavily exploited for rearing ofthe Manila clam, Tapes philippinarum. Harvesting of the clams could add to the general disturbance regime in the lagoon through damage to the benthic community, the release of porewater nutrients which could fuel macroalgal growth and of reduced compounds from the sediment leading to depletion of water column oxygen. We tested these hypotheses during an in situ harvesting experiment. No significant differences were found in population or biomass densities, or community indices between samples collected before and after harvesting. Similarly, no differences were recorded in trophic (food source) availability. Whilst, there was a slight reduction in water column oxygen, pH and Eh values in the plume of suspended sediment, these changes were small. Similarly, increases in water column concentrations of ammonium and reactive phosphorus during harvesting were not significant. Calculations based on profiles of sediment ammonium content, before and after harvesting, demonstrated a release of ammonium equivalent to 13 mmol m−2. In terms of the oxygen and nitrogen budgets of the lagoon the effects of harvesting seem to be of little importance and of the same order of magnitude of sediment-water fluxes driven by clam activity, both terms being subjected to high energy hydrodynarnism.

The impact of an oil spill on organs of bream Abramis brama in the Po River

An oil spill into the River Lambro occurred on 23 February 2010 and reached the Po River the following day. Breams captured here on 1 March 2010, along with a sample from a control site, were examined by light and electron microscopy. The main affected organs were skin and gill with slight or no damage to liver, kidney, and intestine. The gills exhibited lamellar aneurisms, fusion of secondary lamellae, edema with epithelial lifting, mucous cell hypertrophy, and mucus hypersecretion. Significantly higher mucous cell density was observed in the skin of exposed fish. Histochemical staining revealed that acid glycoconjugates were prevalent in epidermal mucous cells in the exposed Abramis brama, whereas neutral and mixed glycoconjugates were dominant in the control fish. Rodlet cells were significantly more abundant in the kidney of exposed fish and showed ultrastructural differences compared to controls. These histopathologic effects were indicators of chemical stress due to exposure to oil. The present study is one of the first which explores the acute effects of this incident and makes part of a few reports focused on freshwater oil spill.

Green electrochemical approach for delignification of wheat straw in second-generation bioethanol production

Ethanol is considered as one of the most promising next-generation automotive fuels, as it is carbon-neutral and can be produced from renewable resources, like lignocellulosic materials. However, owing to biomass characteristics, some technological barriers, such as delignification pretreatment, need to be addressed for an efficient conversion of wood to bioethanol. This paper describes a mild and harmless delignification of wheat straw, carried out at room temperature and requiring only 10 min, using an environmentally-friendly HOCl-containing electrochemically activated water solution, synthesized from diluted brines. Holocellulose (i.e. the sum of cellulose and hemicellulose) rich materials can be obtained with approximately 64% reduction of the initial lignin content. Both the absence of lignin degradation products, which could act as inhibitors during fermentation, and a promising, non-optimized ethanol yield (68% w/w on theoretical value) confirm the potential of this alternative approach towards resolving the challenges to develop a sustainable and low-cost process.