The impact of ornithogenic inputs on phosphorous transport from altered wetland soils to waterways in East Mediterranean ecosystem

Abstract

Large flocks of Eurasian crane (Grus grus, >35,000) have begun wintering in an altered wetland agro-ecosystem located in Northern Israel, a phenomenon that attracts more than 400,000 eco-tourists a year. A 100-ha plot has been used to feed the cranes in order to protect nearby fields. The objective of this study was to evaluate the influence of this bird's feeding practice on the P status of the altered wetland soils and waterways. We installed a series of wells at two depths (40 and 90cm) between two major waterways in the feeding area and monitored the hydraulic heads and collected groundwater samples for elemental analyses. We collected six soil cores and four sediment samples from the waterways and conducted sequential P extraction. We found significant increase in groundwater soluble reactive P (SRP) (>0.5mgl−1) compared with much lower concentrations (~0.06mgl−1) collected in the period prior to the feeding. We found significant decrease in Fe(II), Ca, and SO4 concentrations in the shallow groundwater (33, 208, and 213mgl−1, respectively) compared with the period prior to the feeding (47, 460, and 370mgl−1 respectively). An increase in the more labile P fraction was observed in soils and sediments compared with the period before the feeding. The P input by bird excrement to the feeding area was estimated around 700kg P per season, while P removal by plant harvesting was estimated around 640kgPyr−1. This finding supports the current eco-tourism practices in the middle of intensive farming area, suggesting little impact on waterways.