Persistent DDE in the Mesopotamian wetlands of southern Iraq.

Screening of potential pollutants in surface sediments revealed that almost all persistent organochlorine pesticides were not detected in the newly flooded Mesopotamian wetlands of southern Iraq. This observation suggests that there has been minimal input of organochlorine pesticides recently except for p,p'-DDE which was the only pesticide residue detected (0.29-2.33 microg/kg). It was found in all samples indicating its ability to persist under severe drying of previously exposed surface sediments, high temperature, and intensive solar radiation. p,p'-DDE appears to have a negative relationship with wetland biota, such as zooplankton.

Seasonal influences on the ecology of testate amoebae (Protozoa) in a small Sphagnum peatland in southern Ontario, Canada.

Testate amoebae (Protozoa) were studied in spring, summer, and fall from the same microhabitats in a small Sphagnum-dominated peatland in southern Ontario, Canada. A total of 32 sampling stations were established in two wetland plant communities, 19 in an open Ericaceae low-shrub community and 13 in a closed Picea mariana and Larix laricina swamp community. Sphagnum was collected in each station for analysis of testate amoebae and measurement of soil water content parameters and water table depth in May, August, and October 2001. pH and dissolved oxygen of the groundwater under the Sphagnum were measured also. A total of 52 taxa including the rotifer, Habrotrocha angusticollis, were identified. Soil water content and water table variables emerged as the primary factors separating testate amoebae between the open bog/fen community and swamp community. Testate amoebae in the open bog/fen community showed a clear separation between the May sampling period and the August and October sampling periods. Sampling stations in May had much higher water table and were wetter than those in August and October. Conversely, testate amoebae in the swamp community did not show a clear difference between sampling periods. Soil moisture and water tables appear to be more constant in the swamp communities. Biological factors or other microscale environmental factors may need to be considered to explain seasonal changes in testate amoebae. A greater understanding of relationships between testate amoebae and microenvironmental factors is necessary to track seasonality in testate amoebae distributions.