Barry J. F. Biggs

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We sampled benthic algae monthly for 15 months in 12 New Zealand gravel-bed streams to investigate amongstream differences in algal taxonomic richness and how this might relate to among-stream differences in flood disturbance and nutrient resource regimes. The mean number of benthic algal taxa per month ranged from 9.4 to 21.3 among streams. There were(More)
Photosynthesis-irradiance (P-I) characteristics of periphyton (microphytobenthos) have been considered primarily for entire assemblages. How P-I responses vary with mat thickness and with community composition has not been considered in detail. We used a combined approach of modeling, microscale determinations of photosynthetic rate and light attenuation,(More)
Macrophytes play a key role in many unshaded lotic ecosystems, but little is known of the factors controlling their presence, abundance, and composition. Macrophyte abundance, diversity, and composition were studied in 15 New Zealand streams to test the hypotheses that the presence and development of macrophytes in lotic systems is primarily controlled by(More)
Of the mechanisms that remove benthic algae during flood disturbances, relatively little is known about the effects of sediment scour. We investigated suspended sediment scour using naturally colonized benthic algal communities exposed to realistic velocities and suspended sediment concentrations in a laboratory flowtank. Increased velocity alone removed(More)
In spite of their potential use as indicators of both present and past environmental conditions, little is known about the diatom communities in the many small water bodies at high altitudes in New Zealand. We sampled benthic diatoms at 20 sites in a typical subalpine mire pool/tarn complex near Arthur’s Pass in South Island, New Zealand in the austral(More)
In 2004, an invasive mat-forming freshwater diatom, Didymosphenia geminata (didymo), was found in New Zealand causing concern with regard to potential consequences for local freshwater ecosystems. A four-stage research program was initiated to identify methods to control D. geminata. This article reports the results of Stage 2, in which four potential(More)
Streams are important sites of nutrient transport and transformation in the landscape but little is known about the way in which individual taxa or individual habitats (riffles and pools) influence nutrient dynamics within stream reaches. We used 5-week additions of a stable isotope (15NH4Cl) tracer to investigate nitrogen dynamics in pools and riffles of(More)
Studies documenting phenotypic variation among populations show that ecological performance in one activity is sometimes traded off against another. Identifying environment-specific costs and benefits associated with performance trade-offs is fundamental to knowing how conflicting selection pressures shape phenotype-environment matching in populations. We(More)
A 1-h pulse-dose of a chelated Cu formulation (Gemex™; New Zealand) was applied to a river to test efficacy against the invasive mat-forming diatom Didymosphenia geminata (didymo) and to provide information on nontarget species effects that could not be adequately predicted from laboratory and experimental mesocosm studies. Intensive sampling allowed(More)