Massey Documents by Type
Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294
Browse
3 results
Search Results
Item The ability of detainment bunds to mitigate the impact of pastoral agriculture on surface water quality in the Lake Rotorua catchment : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science, Palmerston North, New Zealand(Massey University, 2020) Levine, BrianIdentifying and implementing cost-effective mitigation strategies are necessary to achieve reductions in the anthropogenic phosphorus (P) and nitrogen (N) loads that contribute to eutrophication and toxic algal blooms in Lake Rotorua, in the Bay of Plenty Region on the North Island of New Zealand. Storm generated surface runoff from grazed pastures, that cover ~48% of Lake Rotorua’s catchment, contribute 67% of the total N (TN) and 43% of the total P (TP) loads delivered from the catchment to the lake. Detainment bunds (DBs) are a novel mitigation strategy targeted at decreasing nutrient and sediment losses by impeding and temporarily ponding stormflows for up to 3 days. A DB is an earthen, stormwater retention structure, approximately 1.5-2 m high and 20-80 m long, constructed on pastures across the flow path of targeted low-order ephemeral streams. Two DBs on pastures in the Lake Rotorua catchment, with 20 and 55 ha catchments, were monitored over 12 months. Nearly 20 storm events resulted in ponding at each site. Detailed hydrological analyses were conducted for each storm in order to establish water balances, as well as to analyse contaminate loads delivered to, and discharged from the DBs. Surface runoff flows were measured, and samples were collected, to determine the DB mitigation performance and to identify the processes affecting the outcomes. The DBs prevented an estimated 51-59% of the annual suspended sediment loads, 47-68% of the annual TP loads, and 57-72% of the annual TN loads delivered to the DBs in runoff, from reaching the lake. An estimated 43-63% of the annual surface runoff delivered to the DBs infiltrated the soil, as a result of increased residence times of surface runoff on well-drained pasture soils. Soil infiltration was mainly responsible for decreased contaminant loads delivered to surface waters downstream of the bunds, while sorption and sedimentation also contributed to some load reductions. The inability to impound only portions of the runoff generated during rare, high magnitude storm events limited the performance of DBs. Furthermore, declining soil infiltration rates and increasing soil P concentrations in the ponding areas could affect the longer-term performance of DBs. A cost: benefit analysis of the DB strategy was conducted in order to compare the cost-effectiveness of DBs to other nutrient migration strategies, with results demonstrating that the DB strategy is a highly cost-effective edge of field mitigation option available to pastoral farmers in the Lake Rotorua catchment.Item The effects of hydrological and nutrient disturbance on stream invertebrate communities using a trait-based approach : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Aquatic Ecology at Massey University, Manawatu, New Zealand(Massey University, 2018) Dinh, Yen Thi HaiAnthropogenic altered flow regimes and nutrient enrichment can cause significant impacts on stream biota and may lead to species loss if characteristics of the local fauna are not compatible with the new environmental conditions. I used fourth corner models, Bayesian ordination, and regression analysis to assess those potential effects on trait and species composition of invertebrate communities in UK, New Zealand (NZ) and Vietnamese streams. NZ temperate mountain streams with greater substrate disturbance increased the abundance of plastron- respirers, but not those having two aquatic life stages or who were filter feeders. UK temperate rivers with predictable multiple high flows per year supported individuals having highly synchronized life history strategy; rivers with one prolonged rising climb and strong groundwater influence were better for those having a high reproduction strategy, and rivers with a steep peak flow supported both strategies. Nutrients affect functional feeding and life history traits via promoting algal overgrowth in NZ streams. Both periphyton biomass and nutrients increased the abundance of algae piercers, collectors and those having two aquatic life stages, being long-lived and having hermaphroditic ability; but decreased the abundance of shredders, scrapers, and those having univoltine life cycles. The post-flood recovery of invertebrate communities depended on the recovery of the food base of the food web that was, in turn, determined by the presence of a forest canopy cover and nutrient levels in a stream. Within the forest canopy stream, communities in the low nutrient site recovered by week 9 after a 1-in-50-year flood in Wellington, NZ. Without the forest canopy, the recovery of communities in nutrient impacted streams (by 25 weeks) was probably associated with a quicker regrowth of periphyton while communities in the low nutrient site had not recovered even after 40 weeks. Hydrological disturbances, nutrients, and their combination had strong effects on invertebrate communities in temperate streams. Taxa that survive in a site have trait characteristics that are highly compatible with both the hydrological and nutrient conditions at a site. In contrast to temperate invertebrate communities, Vietnamese tropical highland community structure was influenced more by elevation than disturbance. Further studies are required to clarify how flow disturbance may effect invertebrate communities in tropical streams.Item Effects of disturbance and nutrient regimes on freshwater invertebrate community structure : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University, Manawatū, New Zealand(Massey University, 2018) Taylor, Joanna MarieFreshwater ecosystems globally are under threat from anthropogenically driven impacts including water abstraction for drinking and agriculture, exotic species invasion, eutrophication, channelization and destruction or modification of habitat. In New Zealand, eutrophication from nutrient enrichment is one of the most pervasive and detrimental impacts. High nutrient levels in waterways is detrimental not only to the species that inhabit them, but can also affect drinking and irrigation water for humans and result in loss of recreational and aesthetic values. Excess nitrogen and phosphorus can cause large amounts of periphyton to grow which in turn can impact water quality and the community composition of stream macroinvertebrates. Macroinvertebrate communities are also strongly affected by floods. More or less frequent flooding can cause changes in composition of stream invertebrate communities. Streams are usually affected by multiple stressors but the effect of those stressors are often considered in isolation for management. As macroinvertebrates are often used as indicators of ecosystem health, it is important to assess how different stressors interact and how these impacts those communities. In this study, macroinvertebrate communities in four Taranaki streams were sampled to assess the interactive effects of nutrient enrichment and flood regime. Nutrient enrichment resulted in invertebrate communities changing markedly between upstream and downstream sites. All four streams had a similar composition at the upstream sites whereas downstream sites in most streams were very different. In two of the streams with lower disturbance regimes, nutrients were the most important driver of invertebrate community composition. In the two streams with a higher disturbance regime, the invertebrate communities were more similar between upstream and downstream sites indicating that flooding was overriding the effects of nutrient enrichment as the most important driver of community composition.