The impact of flooding on aquatic ecosystem services

Flooding is a major disturbance that impacts aquatic ecosystems and the ecosystem services that they provide. Predicted increases in global flood risk due to land use change and water cycle intensification will likely only increase the frequency and severity of these impacts. Extreme flooding events can cause loss of life and significant destruction to property and infrastructure, effects that are easily recognized and frequently reported in the media. However, flooding also has many other effects on people through freshwater aquatic ecosystem services, which often go unrecognized because they are less evident and can be difficult to evaluate. Here, we identify the effects that small magnitude frequently occurring floods ( 100-year recurrence interval) have on ten aquatic ecosystem services through a systematic literature review. We focused on ecosystem services considered by the Millennium Ecosystem Assessment including: (1) supporting services (primary production, soil formation), (2) regulating services (water regulation, water quality, disease regulation, climate regulation), (3) provisioning services (drinking water, food supply), and (4) cultural services (aesthetic value, recreation and tourism). The literature search resulted in 117 studies and each of the ten ecosystem services was represented by an average of 12 ± 4 studies. Extreme floods resulted in losses in almost every ecosystem service considered in this study. However, small floods had neutral or positive effects on half of the ecosystem services we considered. For example, small floods led to increases in primary production, water regulation, and recreation and tourism. Decision-making that preserves small floods while reducing the impacts of extreme floods can increase ecosystem service provision and minimize losses

Parasitism and mating of Diaeretiella rapae (Hymenoptera: Aphidiidae) in an uncontrolled environment

Parasitism and mating activities of Diaeretiella rapae were studied in a shadehouse under ambient environmental conditions during September (early spring) and November (late spring). Before collecting the data, the parasitoid and its aphid host colonies were left to develop undisturbed on cabbage seedlings for 3 months in about 25 m2 area. The plants were highly infested with aphids (average 272±25 aphids/plant) and parasitism by D. rapae varied between 25% and 36% during the study period. There was no significant change in parasitism rate during the 10-week study period (P=0.69). Adult parasitoids emerged from aphid mummies at a rate of more than 90% with a higher number of females than males. The mean female/male parasitoid sex ratio was greater in the second 5-week (late spring) than the early 5-week period (early spring) (P<0.05). Mating activities of the parasitoids were observed at all times of the day. It was found that 49% of the mating pairs comprised a male mounted on a female and 45% were male mounted on another male. The male-female mating was more prevalent during midday compared to morning and evening (P<0.05)