Exploitation of intertidal Zostera species by Brent geese (Branta bernicla hrota): Why dig for your dinner?

Exploitation of intertidal Zostera spp by Pale-bellied Brent geese Branta bernicla hrota in Strangford Lough, Co. Down, was studied with respect to feeding method employed, plant parts exploited, the quality of the forage, and assimilation efficiency. Most Brent geese feeding activity involved digging behaviour, which, along with faecal analyses, indicated that birds were exploiting above (shoot) and below ground portions (rhizome) of the food plant. Nutritional information indicated that while rhizome was lower in overall energy, it contained more accessible energy in the form of water soluble carbohydrate and was lower in indigestible fibre than shoot. Feeding experiments indicated that Brent geese feeding on whole plants of Zostera noltii achieved 43% assimilation efficiency. Dig feeding of intertidal Zostera spp by Brent geese is likely to significantly increase the amount and quality of the forage available. Why dig feeding is not employed on all intertidal systems, and its potential effects on the food plants are discussed.

Arsenic rich iron plaque on macrophyte roots--an ecotoxicological risk?

Arsenic is known to accumulate with iron plaque on macrophyte roots. Three to four years after the Aznalcóllar mine spill (Spain), residual arsenic contamination left in seasonal wetland habitats has been identified in this form by scanning electron microscopy. Total digestion has determined arsenic concentrations in thoroughly washed 'root+plaque' material in excess of 1000 mg kg(-1), and further analysis using X-ray absorption spectroscopy suggests arsenic exists as both arsenate and arsenite. Certain herbivorous species feed on rhizomes and bulbs of macrophytes in a wide range of global environments, and the ecotoxicological impact of consuming arsenic rich iron plaque associated with such food items remains to be quantified. Here, greylag geese which feed on Scirpus maritimus rhizome and bulb material in areas affected by the Aznalcóllar spill are shown to have elevated levels of arsenic in their feces, which may originate from arsenic rich iron plaque.

Arsenic levels in the soils and macrophytes of the 'Entremuros' after the Aznalcóllar mine spill

In April 1998, a holding lagoon containing pyrite ore processing waste rich in arsenic, failed and released 5-6 million m(3) of highly polluting sludge and acidic water. Over 2700 ha of the internationally important Doñana National and Natural Parks were contaminated. The area of Natural Park to sustain the greatest impact was known as the Entremuros. This paper presents 0-5 cm soil monitoring data from the Entremuros, from sampling campaigns 6 and 18 months after the disaster; as well as macrophyte root, rhizome and stem data from samples taken 18 months after the spill. Results show a clear, decreasing, north-south arsenic soil pollution trend, both 6 and 18 months after the spill, and suggest a small reduction in total soil arsenic levels occurred over time; although a significant increase in extractable arsenic is also noted. The two macrophytes (Typha dominguensis and Scirpus maritimus) studied herein are not accumulating arsenic in stem parts, however, accumulation of arsenic on iron plaque on the roots of these plants may be occurring. Further work is recommended in order to determine the ecotoxicological significance of this process in relation to the avian food-chains of Doñana, and elsewhere.