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Abstract River channels, riparian and floodplain forms and dynamics are all influenced strongly by biological processes. However, the influence of macroinvertebrates on entrainment and transport of river sediments remains poorly understood. We use an energy‐based approach to explore the capacity of benthic animals to move surficial, gravel‐bed particles in field and laboratory settings and use the results to assess the relative significance of biological and physical benthic processes. Our results showed that in 11 British gravel‐bed rivers, the maximum energy content (i.e., calorific content) of macroinvertebrate communities generally matched the flow energy associated with median discharges and, at multiple sites, exceeded that of the 10‐year return interval flood. A series of laboratory experiments used to estimate the minimum energy expended by signal crayfish (Pacifastacus leniusculus) when performing geomorphic work established that crayfish move gravel particles at energy levels below that expected of the flow, complicating direct comparisons of the capacity for macroinvertebrates and fluvial flows to influence bed mobility. Our findings suggest that the influence of macroinvertebrate communities in either promoting or suppressing, the mobilisation of the bed may be large compared to equivalent values of fluvial energy. Based on these findings, we conclude that in the gravel‐bed rivers studied, the macroinvertebrate community's potential to perform geomorphic work matches or exceeds the stream power during most of the year. Although our study examined biological and fluvial energy systems separately, it is important to recognise that in nature, these systems are highly interactive. It follows that utilising the energy framework presented in this paper could lead to rapid advances in both fluvial biogeomorphology and river management and restoration. 

Abstract Larval net-spinning caddisflies (Hydropsychidae) function as ecosystem engineers in streams where they construct protective retreats composed of organic and inorganic material affixed with silk filtration nets that alter streambed hydrology. We hypothesized that hydropsychid bio-structures (retreats, nets) are microhabitats for microbes with oxygen-sensitive metabolisms, and therefore increase the metabolic heterogeneity of streambed microbial assemblages. Metagenomic and 16 S rRNA gene amplicon analysis of samples from a montane stream (Cherry Creek, Montana, USA) revealed that microbiomes of caddisfly bio-structures are taxonomically and functionally distinct from those of the immediately adjacent rock biofilm (~2 cm distant) and enriched in microbial taxa with established roles in denitrification, nitrification, and methane production. Genes for denitrification, high oxygen affinity terminal oxidases, hydrogenases, oxidative dissimilatory sulfite reductases, and complete ammonia oxidation are significantly enriched in caddisfly bio-structures. The results suggest a novel ecosystem engineering effect of caddisflies through the creation of low-oxygen, denitrifier-enriched niches in the stream microbiome. Facilitation of metabolic diversity in streambeds may be a largely unrecognized mechanism by which caddisflies alter whole-stream biogeochemistry. 

Abstract Ecosystem engineers can generate hotspots of ecological structure and function by facilitating the aggregation of both resources and consumers. However, nearly all examples of such engineered hotspots come from long‐lived foundation species, such as marine and freshwater mussels, intertidal cordgrasses, and alpine cushion plants, with less attention given to small‐bodied and short‐lived animals. Insects often have rapid life cycles and high population densities and are among the most diverse and ubiquitous animals on earth. Although these taxa have the potential to generate hotspots and heterogeneity comparable to that of foundation species, few studies have examined this possibility. We conducted a mesocosm experiment to examine the degree to which a stream insect ecosystem engineer, the net‐spinning caddisfly (Tricoptera:Hydropsychidae), creates hotspots by facilitating invertebrate community assembly. Our experiment used two treatments: (1) stream benthic habitat with patches of caddisfly engineers present and (2) a control treatment with no caddisflies present. We show that compared to controls, caddisflies increased local resource availability measured as particulate organic matter (POM) by 43%, ecosystem respiration (ER) by 70%, and invertebrate density, biomass, and richness by 96%, 244%, and 72%, respectively. These changes resulted in increased spatial variation of POM by 25%, invertebrate density by 76%, and ER by 29% compared to controls, indicating a strong effect of caddisflies on ecological heterogeneity. We found a positive relationship between invertebrate density and ammonium concentration in the caddisfly treatment, but no such relationship in the control, indicating that either caddisflies themselves or the invertebrate aggregations they create increased nutrient availability. When accounting for the amount of POM, caddisfly treatments increased invertebrate density by 48% and richness by 40% compared to controls, suggesting that caddisflies may also enhance the nutritional quality of resources for the invertebrate assemblage. The caddisfly treatment also increased the rate of ecosystem respiration as a function of increasing POM compared to the control. Our study demonstrates that insect ecosystem engineers can generate heterogeneity by concentrating local resources and consumers, with consequences for carbon and nutrient cycling. 

The collective influence of animals on the processes shaping the Earth’s surface remains largely unknown, with most studies limited to individual species and well-known exemplars. To establish the global geomorphic significance of animals, we systematically reviewed and synthesized evidence across freshwater and terrestrial ecosystems. Over 600 animal taxa had reported geomorphic effects. For the 495 wild animals and 5 livestock identified to species level, we estimated their global abundance, and collective biomass and energy. While our census is global in scope, a lack of research in the tropics and subtropics, and on less visible animals, leaves them underrepresented in analyses. Most reported species are globally widespread, but some are rare, endemic, and/or threatened, leading to risks that key geomorphic processes cease before we fully understand them. We estimate the collective biomass in wild animal geomorphic agents at ≈0.2 Mt Carbon, equating to a biological energy content of ≈7.6 million GJ. If a conservative minimum 1% of this energy contributes to geomorphic work annually, this yields an energy contribution from wild animal geomorphic agents of ≈76,000 GJ—equivalent to the energy of hundreds of thousands of extreme floods. Uncertainties in biomass estimates and energy partitioning mean this value could credibly be an order of magnitude higher, and countless species remain unreported or undiscovered. The livestock estimates exceed the wild animals estimates by three orders of magnitude. The geomorphic energy of animals is far more influential than previously recognized and future losses, dispersal and introductions of zoogeomorphic species may induce substantive landscape changes. 

This data set provides a global inventory of reported animal geomorphic agents and their effects, created by systematically reviewing the published research on animal impacts on landforms and landscapes. Full details on the systematic review process are provided in the accompanying publication Harvey GL, Khan Z, Alberston LK, Coombes M, Johnson MF, Rice SP and Viles HA, Global diversity and energy of animals shaping the Earth's surface, PNAS, which presents analyses of these data (see Related Works). This record contains: a README file, a full bibliography of papers derived from systematic literature review, species inventory of animal geomorphic agents, species occurrence data (where available) downloaded from the Global Biodiversity Information Facility (GBIF), average body size data and number of species for each genus, code used to download and map species occurrence data and code used to produce biomass and energy calculations. All calculations and figures in the accompanying publication (see Related Works) are based on data shared here. Gemma Harvey and Zareena Khan were supported by the Leverhulme Trust via a Leverhulme Research Fellowship (grant number RF-2022-284\4 for the project: Nature's engineers: uncovering signatures of life in landscapes). 

Ecosystem engineers can generate hotspots of ecological structure and function by facilitating the aggregation of both resources and consumers. However, nearly all examples of such engineered hotspots come from long-lived foundation species, such as marine and freshwater mussels, intertidal cordgrasses, and alpine cushion plants, with less attention given to small-bodied, and short-lived taxa. Insects often have rapid life cycles and high population densities and are among the most diverse and ubiquitous animals on earth. Although these taxa have the potential to generate hotspots and heterogeneity comparable to that of foundation species, few studies have examined this possibility. We conducted a mesocosm experiment to examine the degree to which a stream insect ecosystem engineer, the net-spinning caddisfly (Tricoptera:Hydropsychidae), creates hotspots of ecosystem function by facilitating invertebrate community assembly. Our experiment used two treatments: (1) stream benthic habitat with patches of caddisfly engineers present and (2) a control treatment with no caddisflies present. We show that compared to controls, caddisflies increased local resource availability, measured as particulate organic matter (POM) by 43%, ecosystem respiration (ER) by 70%, and invertebrate density, biomass and richness by 96%, 244%, and 72%, respectively. These changes resulted in increased spatial variation of POM by 25%, invertebrate density by 76%, and ER by 29% compared to controls, indicating a strong effect of caddisflies on ecological heterogeneity. We found a positive relationship between invertebrate density and ammonium concentration in the caddisfly treatment, but no such relationship in the control, indicating that either caddisflies themselves or the invertebrate aggregations they create increased nutrient availability. When accounting for the amount of POM, caddisfly treatments increased invertebrate density by 48% and richness by 40% compared to controls, suggesting that caddisflies may also enhance the nutritional quality of resources for the invertebrate assemblage. The caddisfly treatment also increased the rate of ecosystem respiration as a function of increasing POM compared to the control. Our study demonstrates that insect ecosystem engineers can generate heterogeneity by concentrating local resources and consumers, with consequences for carbon and nutrient cycling. 

Hyporheic exchange is now widely acknowledged as a key driver of ecosystem processes in many streams. Yet stream ecologists have been slow to adopt nuanced hydrologic frameworks developed and applied by engineers and hydrologists to describe the relationship between water storage, water age, and water balance in finite hydrosystems such as hyporheic zones. Here, in the context of hyporheic hydrology, we summarize a well-established mathematical framework useful for describing hyporheic hydrology, while also applying the framework heuristically to visualize the relationships between water age, rates of hyporheic exchange, and water volume within hyporheic zones. Building on this heuristic application, we discuss how improved accuracy in the conceptualization of hyporheic exchange can yield a deeper understanding of the role of the hyporheic zone in stream ecosystems. Although the equations presented here have been well-described for decades, our aim is to make the mathematical basis as accessible as possible and to encourage broader understanding among aquatic ecologists of the implications of tailed age distributions commonly observed in water discharged from and stored within hyporheic zones. Our quantitative description of “hyporheic hydraulic geometry,” associated visualizations, and discussion offer a nuanced and realistic understanding of hyporheic hydrology to aid in considering hyporheic exchange in the context of river and stream ecosystem science and management. 

Hyporheic exchange is a key driver of ecosystem processes in streams, yet stream ecologists often fail to leverage detailed conceptual models developed by engineers and hydrologists describing the relationship between water storage, water balance, and water age (time elapsed since a conceptual parcel of water entered the hyporheic zone) in hyporheic zones.  In a companion paper (G.C. Poole et al. Hyporheic Hydraulic Geometry: Conceptualizing relationships among hyporheic exchange, storage, and water age, published in PLoS ONE; doi:10.1371/journal.pone.0262080), we provide visualizations of these relationships in an effort to allow non-hydrologists to grasp four primary concepts along with associated research and management implications: 1) the rate of hyporheic exchange, size of the hyporheic zone, and hyporheic water age are inexorably linked; 2) such linkages can be leveraged to build understanding of hyporheic processes; 3) the age distribution of hyporheic water and hyporheic discharge is heavily skewed toward young water ages -- at any temporal scale of observation (minutes, hours, days, or months) older hyporheic water is rare relative to younger water; 4) the age distribution of water discharged from any hyporheic zone is not the same as the age distribution of water stored within that hyporheic zone. The data set presented here represents the numerical values represented by the figures published in the companion paper.