Antonio Manganaro

The relationship between food availability and growth in Mytilus galloprovincialis in the open sea (southern Mediterranean)

Abstract With the aim of gathering information about the possibility of culturing mussels ( Mytilus galloprovincialis ) in a south Mediterranean oligotrophic area, different lots of mussels were placed in culture at depths of −5 m and −15 m and their growth monitored on a monthly basis. Temperature and salinity were measured in situ and water samples were collected at different depths each month. Total suspended matter (TSM) and its inorganic (ISM) and organic (OSM) fractions were analysed by gravimetry and loss on ignition. Photosynthetic pigments (chlorophyll- a and phaeopigments), particulate organic carbon (POC) and nitrogen (PON), particulate carbohydrate (CHO), protein (PRT) and lipid concentration (LIP) were also measured. The chlorophyll- a concentrations highlighted the high degree of oligotrophy of the study site. Moreover, the inorganic fraction of total seston, which exceeded the organic fraction throughout the study period, highlighted the importance of the allochthonous input of suspended particles. Two main phytoplankton abundance peaks were observed, in spring and autumn. These peaks were mirrored by the biochemical composition of the biopolymeric fraction of particulate organic matter (POM, the sum of PRT, CHO and LIP concentrations). The relatively high values of the POC:PON ratio indicated that the major fraction of particulate organic matter in the study area was of detrital origin. A clear dilution effect on the organic matter, caused by high concentrations of suspended inorganic material, was also revealed by the LPOM/TSM ratio, used as a qualitative food index. The mussels were found to activate physiological compensatory mechanisms in order to maintain a constant absorption rate of organic matter from the total available seston. In this case study, the mussels survived in an environment in which the quantities of available food were frequently time-varied. The mussels placed in culture as juveniles (total length=11.20±4.02 mm) reached a length of approximately 40 mm after 12 months, while the mussels placed in culture as sub-adults (total length=43.16±7.5 mm) reached the commercial size of about 60 mm in the same time interval. The sub-adult mussels spawned in autumn and spring, indicating that they acclimatised well, despite the high degree of oligotrophy of the water.

Evaluation of Functionality and Biological Responses of Mytilus galloprovincialis after Exposure to Quaternium-15 (Methenamine 3-Chloroallylochloride).

Although the irritant effects of quaternium-15 have been established, little is known about the toxicological consequences induced by this xenobiotic on aquatic invertebrates. The present article reports toxicological, histological and physiological effects of quaternium-15 following the exposure of Mytilus galloprovincialis for 18 days at three different concentrations (0.1, 1.0 and 2.0 mg/L). The results demonstrate that at higher concentrations histological damages to M. galloprovincialis gills occur, like melanosis, light exfoliations, increase of mucus production and infiltrative inflammation. In addition digestive gland cells of M. galloprovincialis, were not able to perform the regulation volume decrease (RVD) owing to osmotic stress following the exposure to the preservative. Overall, this first study on quaternium-15 highlights that it can jeopardize both the morphology and vital physiological processes in marine invertebrates, depending on the duration of exposure and the concentration of the preservative, indicating that further studies are necessary to increase our knowledge about the effects of this substance, commonly added to our products of daily use.

Filtration pressure by bivalves affects the trophic conditions in Mediterranean shallow ecosystems

Bivalve filtration may control the amount of seston in coastal waters, reducing local euthrophication and keeping degrading phenomena like hypoxia and anthropogenic pollution under control. Two Sicilian brackish-marine ponds (Ganzirri and Faro) present us with the opportunity to gain data on the effect of bivalve filtration on the amount of particulate organic matter in the field. The cultivation of bivalves has been carried out in both of the ponds since the early 1990s but stopped in Ganzirri in 1995. We tested whether the cessation of bivalve cultivation influenced features of organic matter available to suspension feeders (total suspended matter, its inorganic and organic fractions, chlorophyll a, carbohydrates, proteins and lipids). Since the bivalve cultivation was stopped in Ganzirri in 1995, chlorophyll a sharply and significantly increased compared to Faro, where, in contrast, they remained the same as in previous decades. Recent data shows that organic matter was significantly higher in Ganzirri than Faro and that differences were maintained throughout the study period. Using clearance rate data from the literature, we determined that bivalves can filter the available volume in Ganzirri by about 540 times and in Faro by 650 times per year. Thus bivalve farmed biomass (about 300 tonnes per year of fresh biomass) can exert a high filtration pressure to both (i) control the phytoplankton biomass and trophic dynamics in ponds, and (ii) reduce a possible role of natural-with-sea exchange and polluted waters coming from the hinterlands.

Biogeochemistry and algal communities in the annual sea ice at Terra Nova Bay (Ross Sea, Antarctica)

During the fifteenth Italian Antarctic expedition, in the framework of the Pack Ice Ecosystem Dynamics programme, we investigated structure and functioning of the sympagic communities in the annual pack ice at Terra Nova Bay (74 °41.72′ S, 164 °11.63′ E). From November 1 to November 30 1999, we collected intact sea ice cores and platelet ice samples at an interval of 3 days. Ice samples were analysed for inorganic nutrients concentrations, algal biomass and productivity, pigment spectra, extracellular enzymatic activities and bacterial carbon production, micro-algal and metazoan community structure. Autotrophic biomass in the bottom ice increased more than two orders of magnitude from the beginning to the end of November 1999 (i.e. from c. 1–400 mg chlorophyll a m−3). In the same temporal interval, inorganic nutrients concentrations as well as dissolved organic matter sharply increased. Pigment spectra and microscopic analyses revealed that bottom ice communities were different from those of the platelet ice. The bottom-ice sympagic flora was represented almost exclusively by cryobenthic species, whereas platelet ice was characterised by the presence of both cryopelagic and cryobenthic species. Metazoan community in the bottom sea ice was largely dominated by copepods. In particular, the calanoiod Stephos longipes and the harpacticoid Harpacticus furcifer accounted for more than 90% of the sympagic fauna. In the bottom sea ice concentrations of phaeophorbides and other degraded phytopigments were low indicating that most of the sympagic flora was active. These findings suggest that grazing pressure might be only a minor factor controlling or regulating inorganic nutrient concentrations. Conversely, potential degradation rates of organic carbon mediated by extracellular enzymatic activity were very high and largely exceeded organic matter production by photosynthesis.

Evaluation of Water Variables in No-Take Zone of Ustica Marine Protected Area (Southern Tyrrhenian Sea)

In this research, the seasonal fluctuations of the main water variables in the no-take area (A zone) of the Ustica MPA were investigated. This study aims to monitor the water quality of the Ustica MPA, to analyze all the hydrological parameters useful to the physical-chemical characterization of water and to use TRIX index to characterize the trophic level of the coastal marine area. The final results shown that Ustica is an area of relevant environmental and ecological value and is a good example of a Marine Protected Area, which is not excessively affected by the human presence even during the touristic season. This study represents the first records based on well-organized protocol in order to assess water column characteristics of the studied area. This paper could be used as a reference document for future studies regarding the same or similar areas.

Tyrrhenian Upper Waters in the Ustica Island (Marine Protected Area, Sicily, Italy)

The Marine Protected Area (MPA) of Ustica was monitored for the hydrographic properties in the A zone of the reserve during the period from the autumn of 2001 to the winter of 2003. This study is also a part of a great triennal project (2001–2004) “Sistema Afrodite”, that was carried out in all the MPAs instituted in Italy. The parameters examined were treated statistically to show their seasonal variability. Temperature, nitrate, phosphate, and chlorophyll a showed similar trends between winter 2002 and 2003, while differences between winter 2002 and 2003 were noticed for salinity, dissolved oxygen, and silicate. It is postulated that the Atlantic current and eddies along its margin result in variation of the water characteristics in the MPA zone analyzed in this study.

Artificial pigmentation and flesh quality in red porgy (Pagrus pagrus)

Red porgy (Pagrus pagrus) is a highly valued species of increasing interest for the Mediterranean aquaculture, characterized by a natural red-pink skin coloration, which acquires a gray color under culture conditions. This study was carried out in order to define new diets to modify the pigmentation variability of the red porgy skin. Six thousand red porgy juveniles (29.21 ± 6.39 g) were randomly distributed in three tanks with a volume of 55 m3 each and fed for 8 months with three extruded diets supplemented with graded levels of synthetic carotenoids (GFP0, GFP30, and GFP60). Color, carotenoid content, fatty acid composition of fish skin, chemical and fatty acid composition of fish flesh, and digestive enzymes and histological analysis of the intestine and liver of the fish were determined. The results showed that the supplementation of the synthetic carotenoids affected significantly the skin color indexes with the higher values of redness, yellowness, and chroma recorded in the fish fed with the GFP60 diet, while the other parameters investigated were unaffected except the intestinal protease activities of the GFP60 group, which had lower results. The present study showed encouraging results for developing a new research, but they are not satisfying to the application of this carotenoid supplement feed for this species in production farming.