The movement of aquatic mercury through terrestrial food webs

Mercury has contaminated rivers worldwide, with health consequences for aquatic organisms and humans who consume them. Researchers have focused on aquatic birds as sentinels for mercury. However, trophic transfer between adjacent ecosystems could lead to the export of aquatic mercury to terrestrial habitats. Along a mercury-contaminated river in Virginia, United States, terrestrial birds had significantly elevated levels of mercury in their blood, similar to their aquatic-feeding counterparts. Diet analysis revealed that spiders delivered much of the dietary mercury. We conclude that aquatic mercury pollution can move into terrestrial habitats, where it biomagnifies to levels in songbirds that may cause adverse effects. Rivers contaminated with mercury may pose a threat to the many bird species that feed on predatory invertebrates in adjacent riparian habitats.     

Maintenance of fresh boysenberry fruit quality with UV-C light and heat treatments combined with low storage temperature

Summary

Mature boysenberries (Rubus hybrid) were harvested, heat-treated (45°C for 1 or 3 h or 47°C for 1 h) or exposed to UV-C light (2.3, 4.6 or 9.2 kJ m^–2), and stored at 20°C for 2 d. Fruit treated with 9.2 kJ m^–2 or 45°C for 1 h showed less damaged drupelets per fruit and/or remained firmer than untreated fruit after 2 d. Those treatments were selected for further analyses. In another experiment, boysenberries were either UV-C (9.2 kJ m^–2) or heat-treated (45°C for 1 h) and stored either at 20°C for 1 d or at 0°C for 4 d before transfer to 20°C for 1 d. Both UV-C and heat treatments reduced softening and/or fruit damage. Treated fruit had lower respiration rates and anthocyanin leakage than control fruit suggesting greater tissue integrity. Titratable acidity, pH, total sugar content and antioxidant activity in treated fruit showed fewer changes than in control fruit when stored at 20°C for 1 d. Results suggest that heat or UV-C treatment, alone or in combination with refrigerated storage, may be a useful non-chemical mean of maintaining boysenberry fruit quality and extending postharvest life.     

Application of artificial photoperiod in fish: a factor that increases susceptibility to infectious diseases?

This paper describes and evaluates the mortality associated with the potential stressor effect induced by application of artificial photoperiods in rainbow trout (Oncorhynchus mykiss). After application of artificial photoperiods, high mortalities of trout subjected to this management were recorded (36% in LD 14:10 and 25% in LD 24:0) as compared to controls (7%). The recorded signology related to diseased trout included darkening, lethargy and erratic swimming. Among the morphological changes, skin lesions and ulcerative-type necrosis could be observed. Blood tests, histopathology and isolation of pathogens identified as Flavobacterium psychrophilum, associated with Aeromonas, Pseudomonas and Saprolegnia sp., were performed. The application of artificial photoperiods suggests that fish may be more susceptible to opportunistic diseases; thus, it is advisable to emphasize preventive measures in fish subjected to this management.     

Environmental-friendly farming in Switzerland is not hornwort-friendly

Traditionally managed arable fields host a specialised flora adapted to regular disturbance through tillage. Agricultural intensification during the 20th century resulted in a pronounced biodiversity decline in European agroecosystems. Anthoceros agrestis and Phaeoceros carolinianus, both largely confined to cultivated land in Central Europe and the only representatives of hornworts in northern Switzerland, are examples of species that decreased in Central Europe during the last century. A repeated survey of 28 arable fields in the Swiss Plateau from 1989 to 1995 demonstrated that crop type and associated farming routines were critical in determining hornwort occurrences. During the 10 years following the completion of this survey, agri-environment schemes were introduced aiming at a more environmental-friendly agricultural production. We re-investigated the selected sites in 2005–2007 to examine whether these programmes favoured hornworts. We found a significant decrease of untilled autumn stubble-fields, which accounted for a decline of hornworts. High relative summer air humidity positively affected hornwort occurrence. Gametophytic populations of both taxa regenerated from the persistent diaspore bank after years of unfavourable conditions. To ensure the long-term persistence of hornworts in the Swiss Plateau, we recommend three alternative modifications of current Swiss agri-environment schemes to be implemented in cereal fields with known hornwort occurrences: (1) Tailored conservation headlands, (2) Autumn stubble-fields and (3) Field margin strips sown with arable flora but without crop plants. The proposed practices will promote other typically ephemeral arable bryophytes and seed plants and are likely to be advantageous also for other organisms, such as farmland birds.