Acquatina Lagoon: a model ecosystem to study community patterns

Acquatina is a small lagoon ecosystem (0.45 km2) located on the Adriatic coast only 5 km north of Lecce (Italy). The lagoon has a freshwater input in the northern part and a connection with the sea at the south edge, being characterised by a latitudinal gradient of salinity and an internal patchiness of habitats. Here, we have used the lagoons as a model to study the influence of these sources of variation on the spatial distribution of macrobenthis and fish fauna, using both taxonomic and on taxonomic descriptors. Results showed a non random distribution of both species and functional traits of macroinvertebrate and fish fauna within the lagoon, despite the relatively small surface area. Salinity had an higher inflence than boItom habitat patchiness on both macroinvertebrates and fishes; moreover, spatial co-variance of the two guilds was observed both at the taxonomic and at the size level. As regards fishes, these patterns were common to the dominant species (Atherina Boyeri) and to the rest of the fish guild. Results emphasise that common non random distribution patterns are observed even in small lagoons and for different guilds, including vagile fauna, as fish are. It suggest the occurrence of high intra-specific and inter-specific divergence in lagoon ecosystem allowing resource use optimisation through niche specialisation, available energy partitioning and individual energy budget adaptation

Trace elements and stable isotopes in penguin chicks and eggs: A baseline for monitoring the Ross Sea MPA and trophic transfer studies

Multi-tissue trace elements (TEs), C, N concentrations and stable isotopes (δ13C, δ15N) of chick carcasses and eggs of Adélie and Emperor penguins were studied to i) provide reference data before the recent institution of the Ross Sea Marine Protected Area (Antarctica), and ii) provide conversion factors that allow estimating C, N, δ13C and δ15N in edible tissues from non-edible ones, thus improving the use of stable isotopes in contamination and trophic transfer studies. Higher concentrations of As, Cd, Cr, Cu, Hg, Mn and Pb were found in chick carcasses than in eggs, suggesting increasing contamination in recent decades and high toxicity risks for penguin consumers. Isotopic conversion factors highlighted small differences among body tissues and conspecifics. These values suggest that chick carcasses are reliable indicators of the energy pathways underlying the two penguin species, their trophic position in the food web and their exposure to TEs

Acidic Digestion in a Teleost: Postprandial and Circadian Pattern of Gastric pH, Pepsin Activity, and Pepsinogen and Proton Pump mRNAs Expression

Two different modes for regulation of stomach acid secretion have been described in vertebrates. Some species exhibit a continuous acid secretion maintaining a low gastric pH during fasting. Others, as some teleosts, maintain a neutral gastric pH during fasting while the hydrochloric acid is released only after the ingestion of a meal. Those different patterns seem to be closely related to specific feeding habits. However, our recent observations suggest that this acidification pattern could be modified by changes in daily feeding frequency and time schedule. The aim of this study was to advance in understanding the regulation mechanisms of stomach digestion and pattern of acid secretion in teleost fish. We have examined the postprandial pattern of gastric pH, pepsin activity, and mRNA expression for pepsinogen and proton pump in white seabream juveniles maintained under a light/dark 12/12 hours cycle and receiving only one morning meal. The pepsin activity was analyzed according to the standard protocol buffering at pH 2 and using the actual pH measured in the stomach. The results show how the enzyme precursor is permanently available while the hydrochloric acid, which activates the zymogen fraction, is secreted just after the ingestion of food. Results also reveal that analytical protocol at pH 2 notably overestimates true pepsin activity in fish stomach. The expression of the mRNA encoding pepsinogen and proton pump exhibited almost parallel patterns, with notable increases during the darkness period and sharp decreases just before the morning meal. These results indicate that white seabream uses the resting hours for recovering the mRNA stock that will be quickly used during the feeding process. Our data clearly shows that both daily illumination pattern and feeding time are involved at different level in the regulation of the secretion of digestive juices

Trace metal contamination in a Mediterranean coastal pond (Acquatina, Puglia)

1 - As the interface between land and sea, transitional areas are often negatively impacted by anthropic activities. This impact is the result of many processes, including direct input of pollutants which accumulate in both sediments and aquatic organisms.2 - The aim of this paper is to identify trace metal (As, Cd, total Hg and Pb) contamination in the Acquatina pond (Apulia, Italy), using sediment and fish (A. boyeri, C. labrosus, D. annularis, D. dentex,, D. sargus, D. vulgaris, E. encrasicholus, G. paganellus, L. ramada, M. surmuletus, S. salpa, S. solea) as descriptors. Sampling was carried out in three stations (South, Central and North) and four seasons (summer and autumn 2007, winter and spring 2008). Fish metal concentrations were correlated with ä15N values, which is an indicator of their trophic position.3 - Both sediment and fish trace metal concentrations were compared with regulatory limits. Results showed that trace metal concentrations in sediment were comparable to levels found in moderately contaminated areas. The North station was more contaminated, probably because of freshwater discharges through the Giammatteo channel.4 - Within ichthyofauna, higher metal levels were found in demersal fish. A significant relationship between trace metal and ä15N was found only in total Hg in demersal fish