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Preliminary results of a field study on some stress-related parameters in Tapes philippinarum naturally infected by the protozoan Perkinsus.
No full textThe aim of the present work was to investigate the possible use of the clam Tapes philippinarum - a filter-feeding bivalve living on soft bottoms - in the monitoring of sediment pollution in the Lagoon of Venice (North-East Italy). To this end, two clam populations, exposed to different environmental conditions (a relative clean site and an industrial polluted area), have been monitored for the prevalence of the protozoan parasite Perkinsus sp. as well as for several biological parameters commonly used as determinants of contaminants exposure. First
results showed a low prevalence, higher in the clean site, but a very diffuse distribution of the parasite throughout the two populations. Nevertheless, greater digestive cells height and longer lysosomal latency time were observed in clams from the clean area. As for the physiological stress-related parameters, even if clearance rates were always higher in these clams, scope for growth values indicated a more complicated biological response
Stress meccanico in esemplari sottotaglia di bivalvi eduli: Chamelea gallina
No full textThe effects of repeated disturbance, such as that caused by mechanical fishing systems tipically used in Northern Adriatic, was simulated in a laboratory experiment on the venus clam Chamelea gallina (Bivalvia: Veneridae). Under-sized clams were subjected to experimental shaking, and changes in physiological and behavioural responses were evaluated by determining adenylate energy charge, survival in air time, reburrowing time, and shell damage level
Biochemical and behavioural effects of hydraulic dredging on the target species Chamelea gallina
No full textThis study is focused on evaluating biological effects on the target species Chamelea gallina as a result of repeated
exploitation of clam beds by hydraulic dredging. A biomarker approach was adopted and two physiological indices were
applied: adenylate energy charge (AEC) (biochemical level) and reburrowing behaviour (organism level). The aim was to
investigate the biological response to various types of fishing, i.e., commercial systems using water at high pressures (HP),
and experimental systems at lower pressures (LP) in the field, and to evaluate the response of clams to mechanical stress
in the laboratory. Field results showed that HP-treated clams exhibited significantly lower levels of AEC compared with
LP treatments. A similar trend was shown by reburrowing behaviour; HP-treated clams reburrowed less. Laboratory results
were less clear: a very low level of AEC was measured in both control and treated clams. These poor conditions in foot
muscle did not indicate worsening at organism level, as no dead or dying clams were recorded throughout the experiment.
However, repeated mechanical stress reduced the percentage of reburrowing clams, which suggested that harvesting may
affect reburrowing behaviour
Effects of hydraulic dredging on target species Chamelea gallina from the northern Adriatic Sea: physiological responses and shell damage
No full textThe impact of experimental dredging was assessed on the venus clam Chamelea gallina from seabeds off the Lagoon of Venice. Commercial-sized clams were collected using high water pressure and mechanical sorting (HP), as in professional fishing, and low water pressure without sorting (LP). To highlight the effects of acute stress due to the different approaches in harvesting clams, various biological responses were evaluated at both organism and cell level. Filtration and respiration rates showed opposite behaviour, the former significantly decreasing, the latter increasing, when mechanical stress was higher. Consequently, lower values of scope for growth in HP clams were observed. The survival in air test exhibited significantly lower median survival time values (LT50) in more severely stressed animals. The haematocrit value and phagocytic index significantly decreased in HP samples, revealing a detrimental effect on mechanisms of immunological defence. Acid phosphatase and β-glucuronidase activity was also affected by increasing mechanical stress, even though an opposite trend was shown in the two investigated enzymes. Lastly, higher damage levels were detected in shells of HP clams
Bioaccumulation and biomarker responses of trace metals and micro-organic pollutants in mussels and fish from the Lagoon of Venice, Italy
No full textThe aims of this study were to evaluate levels and effects of trace metals (Cd, Cr, Cu, Fe, Mn, Pb, Zn), PAHs and PCBs in mussels and fish native to the Lagoon of Venice. To this end, bioaccumulation and various biomarkers of generic stress and exposure (malondialdehyde, MDA and metallothioneins, MT; ethoxyresorufin O-deethylase activity, EROD; fluorescent bile metabolites and somatic indices in fish; lysosomal membrane stability, LMS; lipofuscins, LF; neutral lipids, NL and survival-in-air, SOS in mussels) were measured in organisms seasonally collected from two differently influenced areas.In mussels, metal bioaccumulation levels at the two sites were low and fluctuated similarly, exhibiting decreasing levels in summer, like MDA and MT. Micro-organic pollutants and the probably related biological response of LMS did not show either significant site differences or seasonal trends. LF and NL revealed inconclusive patterns. The results of the survival-in-air test were quite erratic, showing that they were associated with the high variability of both natural and physiological parameters temperature, food, reproduction, and body reserve cycle. In fish, both inorganic and organic micro-pollutant levels were low, and differences were detected between sites only for PCBs. The pattern exhibited by micro-organic contaminants was clearly related to the reproductive cycle at both sites; a relationship with PCBs, EROD and MDA was established at the site where their levels were generally higher. Bile metabolites (3-OH Benzo(a)pyrene, 1-OH Pyrene) were associated with PAH contents
Effects of mechanical stress in under-sized clams, Chamelea gallina and Tapes philippinarum: a laboratory approach
No full textFirst attemps in evaluating the effects of hydraulic dredging on the target species Chamelea gallina: biochemical and behavioural responses
No full textIs derelict fishing gear impacting the biodiversity of the Northern Adriatic Sea? An answer from unique biogenic reefs
No full textCountless submerged rocky formations are scattered in the marine coastal area of the Veneto region (Northern Adriatic Sea, Italy). They are known to be suitable substrates for supporting the development of highly complex fish and zoobenthic communities. However, these areas are threatened by local fishing, due to their peculiar morphology and topography which promote gear entanglement. With the aims of quantifying the impacts of abandoned, lost or otherwise discarded fishing gear (ALDFG) on these rocky habitats and monitoring the biodiversity recovery after ALDFG removal, acoustic and diving surveys were performed to map 15 selected rocky outcrops and one artificial reef (for a total surface area of 21 km2). The recovery capability of benthic and fish communities was evaluated by non-destructive techniques in 5 outcrops periodically sampled throughout 18 months. The data collected (number of individuals, species, taxa, and coverage per each species and taxon) were used to calculate three biodiversity indices (species richness, Margalef and Shannon indices) and to assess community recovery. Mapping activities verified the occurrence of 347 ALDFG distributed unevenly over half of the investigated rocky outcrops. The following cleaning operations led to the removal of 362 items, for a total dry weight of 514 kg. The study on biodiversity recovery showed that the complexity of benthic communities gradually improved. In particular, the various biodiversity indices evaluated at the end of the monitoring period generally showed values comparable, or even higher, than those recorded in the reference sites. An increase in biodiversity and species abundance was also observed for fish community; in particular, cryptic species were able to occupy cracks and fractures of rocks previously obstructed by the derelict fishing gear
Evaluation of biological stress indices in Tapes philippinarum from the lagoon of Venice through monitoring of natural populations and trasplantation experiments
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