Effects of small ponds on stream water quality and macroinvertebrate communities

Abstract

Six small constructed ponds (surface area 500-7500 m 2 , catchment area 28-158 ha) in rural and native forest catchments in the Auckland region had poorer water quality than the streams they replaced. Temperature (24°C) and dissolved oxygen (DO) (4 mg/litre) criteria were exceeded for up to 46% and 84% of days, respectively, during a critical 40-day summer period. The poor conditions found in ponds, even within undeveloped native forest catchments, indicated that the physical characteristics of ponds (e.g., lack of shade, organic sediments) affected water quality independently of other factors (e.g., land use, riparian protection). The frequency and severity of the exceedences were related to pond size, retention time, and catchment land use; the most degraded conditions were found in rural ponds with largest surface areas and longest retention times. Ponds affected water quality and macroinvertebrate communities downstream. Exceedences of temperature and DO criteria occurred more frequently and were more severe downstream than upstream of ponds. Ponds in rural catchments increased mean daily stream temperatures 3.1-6.6°C during the critical summer period, and temperature differences were three times higher than those in bush catchments (0.8-2.0°C). Elevated M04122;temperatures were observed for hundreds of metres downstream owing to the slow rate of cooling (1°C/ 100 m), expanding the extent of adverse effects well beyond the "footprint" of the pond. Macroinvertebrate community composition (sample area 1-3 m 2 ) and values of four commonly used metrics appeared to be significantly affected by ponds in rural and native forest catchments. These finding have important management implications that should lead to modifications (e.g., breaching dams) of the estimated 4500 existing ponds in the Auckland region, where possible, and restrictions on proposals for new "o

Riparian Forest Harvesting Effects on Maximum Water Temperatures in Wetland-sourced Headwater Streams from the Nicola River Watershed, British Columbia, Canada

“…The maximum cooling rates we observed (from 1 to 2°C/100 m) are consistent with other studies downstream of small lentic source waters (Rutherford et al 2004;Maxted et al 2005), which have suggested that such high cooling rates apply only over short distances and travel times because downstream water temperatures adjust to the new level of shade and reach a dynamic equilibrium (Rutherford et al 2004). This new T max, 7-day avg (°C) Fig.…”

“…In contrast to lotic-sourced streams, lentic-sourced streams arising from lakes, wetlands, swamps, etc., generally undergo initial cooling in the downstream direction (Brownlee et al 1988;Hendricks and White 1995;Mellina et al 1999Mellina et al , 2002Maxted et al 2005). Studies characterizing the range of potential impacts on headwater stream temperatures from riparian harvesting activities have primarily focused on those with lotic sources (see e.g., Brown and Krygier 1970;Quinn et al 1997;Johnson and Jones 2000;Macdonald et al 2003a, b;Johnson 2004), with the remainder of the literature investigating the effects large reservoirs have on major high-order river ecosystems (Baxter 1977).…”

Microrefuges from drying for invertebrates in a seasonal wetland

“…During summer drying, freshwater animals are increasingly exposed to ultraviolet light, high temperature, large fluctuations in salinity, pH and oxygen, and the rapid disappearance of surface water (Alekseev, DeStasio & Gilbert, 2007). Increased temperature may exceed physiological tolerances and lead to high mortality or local extinction (Maxted et al, 2005). Temperature influences the duration of egg incubation, hatching success, duration of hatching and the induction and termination of resting stages (Oliver, 1971;Alekseev et al, 2007), as well as minimum size at pupation, sex ratios in insects, increased metabolic rate (Terblanche et al, 2005), changes in food availability and food web structure (Rosenzweig et al, 2008).…”

Seasonal variability in the Macroinvertebrate Community Index: Are seasonal correction factors required?

“…Often spatial variability is of interest (e.g., decreasing MCI values at sites progressively further downstream, or below point-source discharges) (Maxted et al 2005;Niyogi et al 2007), but also may be a confounding influence (e.g., variations in MCI between riffles, runs, or pools within a single stream reach, or differences between soft-bottomed or hardbottomed habitats). Similarly, changes in stream health over time may be of interest (e.g., using the MCI to monitor the improvement in stream health resulting from elimination of a point source nutrient discharge), but temporal variability potentially could confound interpretation of long-term monitoring programmes such as State of the Environment (SoE) monitoring if sampling has been undertaken over several weeks or in different seasons.…”