Multiple scales of biological variability in New Zealand streams : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Manawatū, New Zealand

Stream fish communities in Taranaki, New Zealand, were studied for the patterns and drivers of their spatial ecology. The study was focused on three main themes: a) complementarity between geography and landuse in driving regional distribution patterns of stream fish, b) the impact of agriculture on community composition, structure and variability of fish and invertebrates, and c) concordance among environmental distance and community dissimilarities of stream fish and invertebrates. Stream sampling and data collection for fish was conducted at regional scale using 96 sites distributed in the protected forest (44 sites) of Egmont National Park in Taranaki, and in surrounding farmlands (52 sites). Local scale sampling for fish and invertebrates was carried out at 15 stream sites in pasture (8 sites) and in adjacent forest (7 sites). Environmental data of geography, landuse and local habitat description were also gathered concurrently to biological sampling. The regional scale survey reported fifteen fish species, dominated by longfin eels (Anguilla dieffenbachia), redfin bullies (Gobiomorphus huttoni) and koaro (Galaxias brevipinnis), while 12 fish species and 69 different invertebrate taxa were recorded from the 15 sites at local scale. Regional scale spatial patterns of fish were mainly driven by landuse pattern. Catchment landuse (characterised by percentage cover of farming/native forest) effectively partitioned the stream fish community structure in Taranaki. Within each level of catchment landuse (farming), abundance and richness of fish species were negatively correlated with the altitude. Moreover, the upstream slope in high elevations and intensive farming downstream limited the distribution of stream fish across the region. Fish community composition differed significantly but weakly between forest and pasture in the immediate proximity. The dissimilarity of fish communities between forest and pasture increased from regional to local scale, and a similar result was found with stream invertebrate dissimilarity at the local scale. Stream communities (fish and invertebrates) were equally variable among streams between the two land use classes both at regional and local scales. Although the land use difference did not affect within-stream variability of fish, invertebrate communities were less variable within a pasture stream. Trends in in-stream variability of invertebrates were influenced mainly by altitude, stream morphology, pH, and riparian native cover. In concordance analysis, Mantel and Procrustes tests were used to compare community matrices of fish and invertebrates and the environmental distance between stream sites. The spatial patterns of fish and invertebrates were significantly concordant with each other among the 15 streams at the local scale. Nevertheless, community concordance decreased with lower spatial scales, and the two communities were not concordant at local sites within a given stream. Agriculture had a negative impact on the concordance between fish and invertebrates among streams, and none of the communities correlated with the overall environmental distance between agricultural streams. Community concordance between fish and invertebrates was consistently higher than the community-environment links, and lower trophic level (invertebrates) linked to their environment more closely than the upper trophic level (fish). The overall results suggest a bottom-up control of the communities through the stream food web. Finally, to inform the regional management and conservation decision, stream sites were partitioned according to the most important bioenvironmental constraints. The ecological similarity was measured by geography, land use pattern and the abundances of influential native fish species within the region, and the streams were clustered into seven distinct zones, using the method of affinity propagation. Interestingly, the dichotomy in proximal land use was not generally represented between zones, and the species diversity gradients were not significantly different across the zonal stream clusters. The average elevation of a given zone did not influence the community variability, while upstream pasture significantly homogenised fish communities between streams within a zone. Nonetheless the zones were based on river-system connectivity and geographical proximity. This study showed separate effects of confounding geography (altitude) and landuse on stream fish community structure, which has not explicitly been explored by previous studies. Studies with a simultaneous focus on multiple biological (e.g. fish and invertebrates) and environmental (e.g. geography, landuse, stream morphology) scales in varying spatial scales are not common in freshwater ecology. Therefore, this study has a great contribution to the understanding of the spatial ecology of stream communities linked with the control of geography, landuse, environment and likely biological interactions between fish and invertebrates

The ecology of chalk-stream invertebrates studied in a recirculating stream

To study and qualify the factors influencing interactions between various trophic levels in natural hard-water streams, a recirculating artificial stream channel was constructed. This structure has enabled patterns of population change of stream fauna to be observed under partially controlled physical and chemical conditions. Initial colonization of the substratum by invertebrates and subsequent succession was studied along with depth distribution and growth and production studies of invertebrates

Food webs in forest and pasture streams in the Waikato region, New Zealand: A study based on analyses of stable isotopes of carbon and nitrogen, and fish gut contents.

Stable isotopes of carbon (C) and nitrogen (N) were studied in 11 stream communities in the Waikato region of New Zealand. From comparisons of mean d13C and d15N values, food webs in the shaded, forest streams were clearly based on allochthonous material (conditioned leaf litter and terrestrial invertebrates). Autotrophs in forest streams were not a significant C source for the food webs. However, the C source of food webs in the unshaded pasture streams appeared to be a mixture of allochthonous and autochthonous material. Conditioned leaf litter appeared to contribute to the pasture stream food webs, and the d13C and d15N of some samples of epilithic diatoms indicated their consumption by invertebrates in pasture streams. Fish ate a wide range of aquatic invertebrates; longfinned eels (Anguilla dieffenbachiai) and banded kokopu (Galaxias fasciatus) also had a large proportion of terrestrial invertebrates in their diet. Filamentous green algae were found only at pasture sites, where they were sometimes abundant. The wide range of d13C values of filamentous green algae (-18.8 to -29.7[[perthousand]]) complicated understanding of their role in the stream food webs. The d13C values of Cladophora were related to water velocity, with more 13C-enriched values in pools than in runs (-23.2[[perthousand]] in pools, mean velocity 0.12 m s-1; -28.1[[perthousand]] in runs, mean velocity 0.24 m s-1). Crayfish and the gastropod mollusc Potamopyrgus appeared to be the only invertebrates to eat filamentous green algae

Spatial variability in the hyporheic zone refugium of temporary streams

A key ecological role hypothesized for the hyporheic zone is as a refugium that promotes survival of benthic invertebrates during adverse conditions in the surface stream. Many studies have investigated use of the hyporheic refugium during hydrological extremes (spates and streambed drying), and recent research has linked an increase in the abundance of benthic invertebrates within hyporheic sediments to increasing biotic interactions during flow recession in a temporary stream. This study examined spatial variability in the refugial capacity of the hyporheic zone in two groundwater-dominated streams which flow permanence varied over small areas. Two non- insect taxa, Gammarus pulex and Polycelis spp. Were common to both streams and were investigated in detail. Hydrological conditions in both streams comprised a four- month period of flow recession and low flows, accompanied by reductions in water depth and wetted width. Consequent declines in submerged benthic habitat availability were associated with increases in population densities of mobile benthic taxa, in particular G. pulex

Ecological and physical characteristics of the Te Awa O Katapaki Stream, Flagstaff, Waikato

1. The fish, macroinvertebrates, aquatic vegetation, and water quality indicate that the Te Awa O Katapaki Stream is an unpolluted, pastureland stream that is typical of the Waikato region. 2. The stream has very high nutrient concentrations that probably result from the dairy farming upstream. 3. The fish fauna is dominated by the native shortfinned eels. The presence of the migratory common smelt indicates that swimming fish species also have free access to the stream from the Waikato River. 4. Fish of high conservation value, such as giant or banded kokopu (Galaxias argenteus or G. fasciatus) were absent, which is predictable given the warm, unshaded nature of the stream. 5. Fish and invertebrates would soon recolonise the restored stream following any work in the streambed

The effects of intense fire on headwater streams of the Colville National Forest, WA

Thesis (M.S.) University of Alaska Fairbanks, 2006Forest fires play an important role in shaping ecosystems, and there has been growing concern on the effects of high intensity fires on forest and aquatic ecosystems. Headwater streams are highly connected to riparian and surrounding terrestrial systems, and to downstream aquatic systems, partly through prey and organic matter transfers via aquatic invertebrate drift and emergence. Because of their small size, headwater streams may experience the greatest initial impact from forest fire, but may also return to pre-fire conditions quicker than larger streams. In this study, headwater streams from replicated burned and control watersheds were sampled in the two years following an intense forest fire in northeastern Washington. Benthic, drift and emergence samples of aquatic invertebrates were taken and analyzed for differences in density, biomass and community composition between watershed types. There was significantly higher density of invertebrates in burned sites, but no difference in biomass except in invertebrate emergence which was greater at burned sites. There was lower diversity in the burned watersheds, and the invertebrate community was dominated by chironomids. These changes in invertebrate density and community composition could influence the food resources available to aquatic and riparian consumers

Preliminary estimates of mass-loss rates, changes in stable isotope composition, and invertebrate colonisation of evergreen and deciduous leaves in a Waikato, New Zealand, stream.

Rates of mass loss are important in the choice of tree species used in riparian rehabilitation because leaves that break down fast should contribute to stream food-webs more rapidly than leaves that break down more slowly. To examine comparative mass-loss rates of some native evergreen and introduced deciduous trees in a New Zealand stream, fallen leaves were incubated in bags with 2 x 3 mm mesh openings. The native trees were mahoe (Melicytus ramiflorus), kahikatea (Dacrycarpus dacrydioides), silver beech (Nothofagus menziesii), rewarewa (Knightia excelsa), tawa (Beilschmiedia tawa), and the introduced trees were silver birch (Betula pendula) and alder (Alnus glutinosa). The leaf bags were left in the Mangaotama Stream for 28 days from mid April to mid May 1995 when mean water temperature was 14.5deg.C, giving a total of 406 degree days. Rates of mass loss followed the sequence: mahoe > silver birch > alder > kahikatea > silver beech > rewarewa > tawa. Mean mass-loss rate for mahoe, assuming a negative exponential model, was 0.0507 k day-1 (0.00350 k (degree day)-1), and for tawa was 0.0036 k day-1 (0.00025 k (degree day)-1). C:N ratio decreased on average from 45:1 to 35:1, and d15N increased between 0.7 and 3.0[[perthousand]] (1.8 +/- 0.41[[perthousand]], mean +/-1 standard error), excluding kahikatea. Changes in d13C were smaller and not consistent in direction. Biomass of invertebrates was greatest in bags that had lost 25-45% of their initial leaf biomass

Ecological integrity of boreal streams

Running waters provide a number of services for humans, such as drinking water and food resources and many freshwater animals are confined and specialised to this environment. However, this natural resource has become increasingly impacted by humans resulting in a substantial loss of biodiversity and services. To assess ecological integrity of streams a number of bioassessment schemes have been developed and most of these are based on community structure and composition. Although many of the biological metrics developed have been used successfully in bioassessment, it has been suggested that ecosystem functions, such as leaf-litter decomposition, should be incorporated in modern bioassessment schemes. In this thesis I compare a number of structural metrics with functional metrics along a nutrient gradient in nine boreal streams in south-central Sweden to assess the potential of ecosystem function as a biomonitoring tool. Leaf-litter breakdown (Alnus glutinosa (L.) Gaertner) was studied during four seasons and stable isotope (δ13C and δ15N) and stoichiometric ratios (C:N) of phytobenthos, CPOM, FPOM, invertebrates and fish were also analysed. My results indicate that leaf-litter breakdown is a relatively insensitive tool to assess ecosystem impairment compared to invertebrate metrics. However, δ15N in organic matter has been suggested as a potential tool to assess ecological integrity of streams and my results support this conjecture. A strong response in δ15N in organic matter with nutrient enrichment was revealed, suggesting that δ15N could serve as a simple tool to assess nutrient enrichment effects in boreal streams. I also found that leaf-litter associated fungi and invertebrates were positively correlated with leaf-litter breakdown rates and a nutrient gradient. Moreover, I found that certain dominating species, e.g. waterlouse (Asellus aquaticus (L.)), can have a strong influence on ecosystem processes. In this thesis I show that leaf-litter breakdown is not a simple low-cost biomonitoring tool as several field trips were necessary to assure adequate litter-bag recovery. Also natural factors, such as fluctuating water levels and heavy snow fall, resulted in substantial loss of litter bags thereby confounding data interpretation

Benthic and interstitial habitats of a lentic spring as invertebrate refuges during supra-seasonal drought

Instream refuges are places where invertebrates persist during disturbances due to reduced adverse impacts. During droughts, low flows may be accompanied by elevated temperatures, and potential refuges including subsurface sediments and spring-fed headwaters are therefore characterized by hydrological and thermal stability. This study examined invertebrate use of benthic and interstitial habitats (analogous to the hyporheic zone) in a groundwater-dominated, perennial limnocrene spring during a supra-seasonal drought. Although exceptionally high air temperatures occurred as flow declined, environmental conditions in the spring were relatively stable, and refuge-seeking vertical migrations into interstitial habitats did not coincide with peak temperatures. However, maximum benthic abundance of two amphipods (Gammarus pulex and Crangonyx pseudogracilis) occurred shortly after the period of elevated temperatures. It is suggested that this temporary increase in the abundance of these mobile taxa reflected upstream migrations triggered by a combination of refuge-seeking behaviour and thermally-stimulated activity. In addition, the spring provided a passive refuge for many lotic invertebrate taxa. A conceptual model is presented, which illustrates the potential contribution of multiple refuges to invertebrate persistence in drought-impacted ecosystems

Ecological study of chalk and limestone stream. Annual report October 1975 to September 1976

Few detailed studies have been made on the ecology of the chalk streams. A complex community of plants and animals is present and much more information is required to achieve an understanding of the requirements and interactions of all the species. It is important that the rivers affected by this scheme should be studied and kept under continued observation so that any effects produced by the scheme can be detected. The report gives a brief synopsis of work carried out during the third year of a four year ecological study sponsored jointly by the Thames Water Authority and the Central Water Planning Unit. It assumes . It assumes some familiarity with the investigations carried out on the River Lambourn during the preceding three years which was sponsored jointly by the Thames Conservancy and Water Resources Board (immediate predecessors of the present sponsoring organisations). (PDF contains 35 pages