In large areas of the Southern Ocean, iron limits phytoplankton production. Although biologically mediated iron recycling has been studied for the higher trophic-level whales and the lower trophic-level krill, less is known of the numerically abundant seabirds foraging in Antarctic waters. In this study, we estimate the magnitude of iron recycled by two Antarctic breeding seabirds, the Adélie and emperor penguins, across the a...

New geochemical data, including Sr–Nd–Pb isotopes for whole-rock and groundmass samples, are reported for edifice-forming eruptives at Tongariro volcano, New Zealand, which span its ~ 350 ka to late Holocene history. Tongariro eruptives are medium-K basaltic-andesites to dacites (53.0–66.2 wt% SiO 2 ) that evolved via assimilation-fractional crystallisation (AFC) processes partly or mostly in the uppermost 15 km of the crust....

Motivation Aquatic insects comprise 64% of freshwater animal diversity and are widely used as bioindicators to assess water quality impairment and freshwater ecosystem health, as well as to test ecological hypotheses. Despite their importance, a comprehensive, global database of aquatic insect occurrences for mapping freshwater biodiversity in macroecological studies and applied freshwater research is missing. We aim to fill t...

When herbivore abundance is controlled by predators there may be an indirect positive effect on primary producers due to reduced grazing pressure, but the potential of predation refuges to modify such trophic cascades has rarely been studied. By experimentally manipulating substrate particle size and fish predation regime, we assessed the outcome of invertebrate grazer–biofilm interactions in streams. Locations at the center o...

Global climate change is likely to modify the ecological consequences of currently acting stressors, but potentially important interactions between climate warming and land‐use related stressors remain largely unknown. Agriculture affects streams and rivers worldwide, including via nutrient enrichment and increased fine sediment input. We manipulated nutrients (simulating agricultural run‐off) and deposited fine sediment (simu...

Lack of knowledge about how the various drivers of global climate change will interact with multiple stressors already affecting ecosystems is the basis for great uncertainty in projections of future biological change. Despite concerns about the impacts of changes in land use, eutrophication and climate warming in running waters, the interactive effects of these stressors on stream periphyton are largely unknown. We manipulate...

Ecology Letters (2011) 14: 169–178 Abstract Despite growing awareness of the significance of body‐size and predator–prey body‐mass ratios for the stability of ecological networks, our understanding of their distribution within ecosystems is incomplete. Here, we study the relationships between predator and prey size, body‐mass ratios and predator trophic levels using body‐mass estimates of 1313 predators (invertebrates, ectothe...

We examined nitrogen (N) uptake in seven grassland streams lying in catchments along a gradient (0–84%) of agricultural land use in New Zealand using a stable isotope ( 15 N) addition of NH 4 + to quantify whole‐stream uptake rates and uptake by specific compartments within the streams. Whole‐stream uptake of NH 4 + ranged from 1.2 mmol N m −2 min −1 to 7.9 mmol N m −2 min −1 and showed no evidence of strong saturation of upta...

We studied four streams in southern New Zealand in 2002 to document downstream changes in water quality, habitat, and stream biota in relation to land use. Two streams were in catchments that had increasing intensity of agricultural development downstream from relatively pristine headwaters. A third stream had the most intense land use in the headwaters and a riparian corridor of regenerating native forest along its middle rea...

The nature of benthic biofilm was assessed in four streams in New Zealand, two flowing through native tussock grassland and two through exotic Pinus radiata forest. Components of the biofilm were described using epi‐fluorescent staining (DAPI) and scanning electron microscopy (SEM) of rock and wood substrata. DAPI and SEM analyses showed significantly more bacteria and fungi on rock and wood in tussock as opposed to pine strea...

Agricultural development of native grasslands may change stream physico‐chemistry in ways that provide both subsidies and stresses to the system. The aims of this study were to determine: (1) which physico‐chemical parameters respond most strongly to agricultural development; (2) how biodiversity, community composition, and food‐web structure responded to these changes; and (3) to determine the balance between negative and pos...

Knowledge of the population biology of invading species will often be necessary to develop effective management procedures and policies. But because invaders can have unexpected indirect effects in food webs, invasion ecologists need to integrate processes at the population level and other ecological levels. I describe a series of coordinated studies in New Zealand streams that address the effect of an exotic fish on individua...

Crayfish ( Paranephrops zealandicus White) stomachs from streams in both native bush (mainly tree leaves and dicotyledonous seeds) and exotic pasture settings (mainly grass stems and monocotyledonous seeds) were dominated by allochthonous material. More detritus occurred in stomachs in autumn‐winter than in spring‐summer, but quantities were similar in crayfish from native bush and pasture streams. The stomachs of larger crayf...