Annika Wagenhoff

Cawthron Institute | CI

The setting of numeric instream objectives (effects-based criteria) and catchment limits for major agricultural stressors, such as nutrients and fine sediment, is a promising policy instrument to prevent or reduce degradation of stream ecosystem health. We explored the suitability of assemblage thresholds, defined as a point at which a small increa...

Setting numeric in-stream objectives (limits, criteria) to inform limits on catchment loads for major landuse stressors is a promising policy instrument to prevent ecosystem degradation. Management objectives can be informed by thresholds identified from stressor - response shapes of ecological indicators based on field survey data. Use of multiple...

1. Degradation of freshwater ecosystems is a major concern worldwide. Agriculture introduces multiple stressors to streams, presenting a challenge for freshwater managers who must understand the relative strengths of individual stressor effects and their combined multiple-stressor effects. 2. Using a replicated regression design, we manipulated lev...

1. The factors underlying population and community dynamics are almost invariably multivariate, and ecosystems worldwide are affected by many anthropogenic stressors. Inorganic dissolved nutri-ents and deposited fine sediment are common stressors in agricultural streams and can be expected to influence benthic algae and cyanobacteria. 2. We determi...

1. Stream managers need to understand relationships between multiple stressors and ecological responses. We examined responses of benthic invertebrates and algae along two land-use-related stressor gradients of concern in running waters. Our correlative study of the consequences of augmented deposited fine sediment and nutrient concentrations was c...

There is growing recognition that multiple forms of uncertainty influence policy reform, but we need case studies illustrating how uncertainties influence reform, and strategies used to manage uncertainties in practice. We present a case study of how science was generated and incorporated into national water policy. We estimated turbidity (suspende...

A method for objectively estimating reference states for suspended fine sediment (turbidity) is presented. To be fit for water policy development and implementation the method had to satisfy four requirements: (1) the method must not be dependent on data from minimally-disturbed reference sites; (2) the method must facilitate characterization of re...

Abstract Undertaking environmental assessments on non‐wadeable rivers is challenging due to their size, depth, and water velocity. The cotton strip assay (CSA) is a functional indicator used in assessing the ecological health of non‐wadeable rivers by measuring cellulose decomposition potential. Enhancing knowledge on the microbial communities resp...

Estuaries are the endpoints of rivers, which shape their physical and biological characteristics, yet few tools are available to link the health of estuaries to their upstream sources. As a first step towards the use of macro-invertebrate indices for setting ecological health thresholds in streams that also protect estuaries, we examined relationsh...

This study investigated the impact of pastoral land use and nutrient and fine sediment inputs on Microcoleus autumnalis and filamentous algae-dominated mats, and benthic chlorophyll-a in streams (lower North Island, New Zealand). Surveying and sampling was undertaken monthly at 61 sites spanning a wide gradient in catchment cover and environmental...

This report is a discussion of the concepts and practice relating to river monitoring, reporting and management

This draft NIWA report provides the first attempt to develop bottom-line thresholds for suspended and deposited sediment based on ecological responses for New Zealand rivers and streams.

This document is the final written output from the Ministry for the Environment funded project on benthic macroinvertebrate indicators of ecosystem health (Contract 21630). The project was designed to address a recognised need to include macroinvertebrates in the National Policy Statement for Freshwater Management (NPS-FM) 2014. Benthic macroinvert...

The Stream Ecology Research Group at Otago University has won the ”River Story Award” at the 2017 New Zealand River Awards. A 3.5 min video made by the Cawthron Foundation tells a story about the multiple-stressor research done since 2007 in the ExStream System, an innovative research facility delevoped by Jay Piggott and Christoph Matthaei. The vi...

Proliferations of the benthic anatoxin-producing cyanobacterium Phormidium are increasing in prevalence in cobble-bed rivers worldwide. This proliferation is of particular concern when rivers are used as sources of drinking water or for recreation. Little is known about the physicochemical variables promoting proliferations, and our existing knowle...

Rehabilitation of vertical hydrological exchange in small pasture streams is expected to improve hyporheic habitat, invertebrate life and ecosystem functioning, and may be achieved by adding large woody debris (LWD). This study investigated whether hyporheic improvement within 10 to 50 cm below streambed surface is evident around existing wood stru...

Thaumetopoea processionea is a serious defoliator of oak and of medical concern whose abundance has consistently increased throughout Europe during the past two decades. This study validates a previously published frost day/temperature sum model for predicting time of egg hatch of this species using five years of recent field data from South-West G...

Anthropogenic nutrient enrichment increases the supply ratio of N and P to aquatic ecosystems and can affect the identity of the limiting nutrient. Here we focus on how stream communities change along gradients of N and P supply and stream catchment landuse intensity. We used a survey approach in 41 southern New Zealand tributaries to investigate h...