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Regional guidelines for ecological assessments of freshwater environments: Aquatic plant cover in wadeable streams - version 2

TR 2014/03
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Report: TR 2014/03

Author: K Collier, M Hamer (Waikato Regional Council) and P Champion (NIWA)

About this report

Aquatic plants (macrophytes) and algae (periphyton) play an important role in stream and river ecology. They provide a food source and habitat for living creatures such as fish and invertebrates and can also influence instream habitats by reducing water velocities and increasing sediment deposition.

Aquatic plants can exacerbate flooding in nutrient rich waters by taking up space in confined channels and blocking culverts during flood events. They also play a major role in the diurnal changes in dissolved oxygen levels within waterways by producing oxygen during the day and using it up at night. In turn aquatic plants and algae are influenced by waterway nutrient levels, temperature, flow stability and light.

This report outlines the methods the Waikato Regional Council recommends for rapidly assessing plant and algal cover in the field. A demonstration is given on how to produce indices relating to both algal cover and aquatic plants. These indices can then be used to explain differences between invertebrate samples, compare differing sites, and present this information to the public or to council in assessments of environmental effects.

The periphyton assessment protocol is based on that developed by NIWA in 2002. The aquatic plant rapid assessment method was developed by the Waikato Regional Council in conjunction with NIWA. These methods were originally outlined in Regional guidelines for ecological assessments of freshwater environments: aquatic plant cover in wadeable streams (Environment Waikato Technical Report 2006/47).  This report replaces and updates those guidelines in order to clarify and revise some of the index equations. It also provides some examples of the relationships between macro-invertebrate indices and the aquatic plant and periphyton indices demonstrated in this report. The plant identification photo guide has also been updated to include more of the plants now found regularly in the Waikato region.

This report is intended to be used as a guide to the methods for the rapid assessment of aquatic plants and algal cover in wadeable streams.

Read or download the report

Reqional guidelines for ecological assessments of freshwater environments: Aquatic plant cover in wadeable streams - version 2 [PDF, 4.1 MB]