Ecoregional differences in macrophyte and macroinvertebrate communities between Westland and Waikato: Are all New Zealand lowland streams the same?

Abstract

We characterised water chemistry, aquatic habitat, macrophytes, and invertebrate assemblages in eight lowland streams-five in Westland, South Island, and three in the Waikato, North Island, New Zealand. Factors influencing invertebrate community structure over large (between ecoregions) and small (within an ecoregion) spatial scales were investigated. The Westland sites had generally lower nutrient concentrations, conductivity, and water clarity, and coarser substrates than the Waikato sites, reflecting differences in geological history, hydrology, and land-use intensity. The macrophyte communities in each region were very different in species composition and structure, but seasonal abundance patterns in both regions were fairly typical of New Zealand streams in general. Alien obligate submerged macrophyte species were absent from the Westland lowland stream sites, and may partly reflect the isolated nature of this region where colonisation by asexual macrophytes would be difficult. Waikato stream invertebrate faunas were *Author for correspondence. M02006; Published 14 November Received 23 January 2002; accepted 19 July 2002dominated by molluscs (mainly Potamopyrgus) and crustaceans (mainly amphipods), whereas Ephemeroptera, Trichoptera, and Coleoptera taxa dominated the Westland stream faunas. The overall structure of invertebrate assemblages appeared to be influenced by a combination of regional differences in substrate type, nutrient concentrations, water clarity, and macrophyte cover. Westland streams with more upstream pastoral development had higher proportions of molluscs than those with predominantly forested or scrub catchments. Our study suggests that large-scale ecoregional differences may override smaller-scale land-use effects on lowland stream invertebrate communities, and that management strategies should be developed on an ecoregional basis for lowland stream ecosystems.

Environmental DNA as a new method for early detection of New Zealand mudsnails (Potamopyrgus antipodarum)

“…Several authors have noted that it does well in moderately eutrophic systems (Dorgelo 1987, Scott et al 1994. In stable habitats with high nutrient loads and abundant macrophytes, mud snails dominated (relative abundance of 90%) invertebrate communities in New Zealand streams (Duggan et al 2002). In Australia, the success of NZ mudsnail introductions seems to be associated with agricultural runoff and nutrient inputs (Scheiber et al 2003).…”

Land‐use impacts and water quality targets in the intensive dairying catchment of the Toenepi Stream, New Zealand

“…Since the earlier Toenepi Stream study, which concluded in 1998, there have been a number of other studies of the stream and catchment because they are located in the established dairy farming Waikato/Hauraki region of New Zealand (DaviesColley & Nagels 2002;Duggan et al 2002;Quinn & Stroud 2002;Wilcock & Croker 2004). The current programme, in which Toenepi is one of the regional dairy catchments, started in 2001 and, apart from short periods in 1997-98 and 2001-02, there has been regular monitoring of water quality and ongoing monitoring of stream discharge since the mid-1990s.…”

“…Water pollutants of concern include various forms of the nutrient elements N and P, as well as suspended solids (SS) and faecal microbes as measured by indicator bacteria (Escherlchla coll) (Davies-Colley et al 2004). In addition, rural stream habitats are commonly degraded by having high temperatures, low dissolved oxygen (DO), wide diurnal changes in pH, and poor visual clarity (Wilcock et al 1999;Duggan et al 2002;Nagels et al 2002).…”

Invertebrate community dynamics in soft‐bottomed streams of northern New Zealand: A spatio‐temporal hierarchy

“…Site codes are the same as those used in Northland (N) by Collier (1995), and Waikato (W) by Collier et al (1998) 8 10 6 2 4 5 7 11 5 5 5 5 9 3 3 2 4 4 11 7 6 % macrophyte cover 20 10 5 1 90 10 <1 <1 <1 0 -39 8 0 73 46 85 60 89 41 -21 43 † % sand/silt 50 100 100 90 90 50 50 70 62 68 85 62 71 53 68 61 87 71 94 85 100 67 100 * Habitat data from Duggan et al (2002).…”

“…However, there is insufficient information on factors affecting invertebrate communities among and within soft-bottomed sites to understand the mechanisms behind these differences. This paper represents an amalgam of several independent studies carried out between 1994 and 1999 focusing on invertebrate communities in lowland streams of northern New Zealand (e.g., Collier 1995;Collier et al 1998Collier et al , 1999Duggan et al 2002). Data for soft-bottomed sites have been extracted from these published studies and other unpublished work, and re-analysed using a common ordination approach to investigate factors influencing macroinvertebrate community structure and composition across a range of spatial and temporal scales.…”