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Opportunities to understand and protect natural aquatic diversity in both relatively pristine and managed rivers can be enhanced with a comprehensive, system-wide understanding of a river’s hydrogeomorpholgy and its effects on ecological structure and functioning from the river’s headwaters to its terminus in an ocean, lake, or natural endorheic basin. While a moderate number of macrosystem ecology studies have been undertaken recently in headwaters, comparable ecological approaches to studying whole rivers or at least their larger components from upstream to downstream are relatively rare. This is partially correlated with the paucity of applicable river ecosystem models developed over the last half century which could otherwise provide diverse, testable tenets (hypotheses). This manuscript focuses on a 15+ year updated, system-wide analysis of the applicability of the 17 tenets included in our previously published, lotic model - the Riverine Ecosystem Synthesis, or RES. We also propose here four new tenets and analyze the system-wide applicability of the revised RES. Those new tenets hypothesize that: (H-18) “The range and degree of impacts of a Functional Process Zone on biodiversity and ecological processes differ among several factors, including types of FPZs, total river area covered, and dependent variables examined, even in the same river network position”; (H-19) “The degree of ecological differences among types of FPZs vary seasonally with the process being examined while also differing among types of life history characteristics - especially when contrasting responses among seasonal periods of either maximum or minimum growth and reproduction”; (H-20) “The relative importance of in-stream versus watershed drivers of ecological processes in streams can vary within macrosystems and among ecoregions and partially depends on elevation, terrestrial characteristics (natural or human modified), and FPZ type and extent”; and (H-21) “The provision of ecosystem services varies significantly with FPZ type, river size, and location vis-à-vis human populations”. Where appropriate, we also evaluate aspects of several other models published by colleagues that pertain to river ecology.

Abstract River hydrogeomorphology is a major driver shaping biodiversity and community composition. Here, we examine how hydrogeomorphic heterogeneity expressed by Functional Process Zones (FPZs) in river networks is associated with fish assemblage variation. We examined this association in two distinct ecoregions in Mongolia expected to display different gradients of river network hydrogeomorphic heterogeneity. We delineated FPZs by extracting valley‐scale hydrogeomorphic variables at 10 km sample intervals in forest steppe (FS) and in grassland (G) river networks. We sampled fish assemblages and examined variation associated with changes in gradients of hydrogeomorphology as expressed by the FPZs. Thus, we examined assemblage variation as patterns of occurrence‐ and abundance‐based beta diversities for the taxonomic composition of assemblages and as functional beta diversity. Overall, we delineated 5 and 6 FPZs in river networks of the FS and G, respectively. Eight fish species were found in the FS river network and seventeen in the G, four of them common to both ecoregions. Functional richness was correspondingly higher in the G river network. Variation in the taxonomic composition of assemblages was driven by species turnover and was only significant in the G river network. Abundance‐based taxonomic variation was significant in river networks of both ecoregions, while the functional beta diversity results were inconclusive. We show that valley‐scale hydrogeomorphology is a significant driver of variation in fish assemblages at a macrosystem scale. Both changes in the composition of fish assemblages and the carrying capacity of the river network were driven by valley‐scale hydrogeomorphic variables. River network hydrogeomorphology as accounted for in the study has, therefore, the potential to inform macrosystem scale community ecology research and conservation efforts.

River hydrogeomorphology is a major driver shaping biodiversity and community composition. Here, we examine how hydrogeomorphic heterogeneity expressed by Functional Process Zones (FPZs) in river networks is associated with fish assemblage variation. We examined this association in two distinct ecoregions in Mongolia expected to display different gradients of river network hydrogeomorphic heterogeneity. We delineated FPZs by extracting valley‐scale hydrogeomorphic variables at 10 km sample intervals in forest steppe (FS) and in grassland (G) river networks. We sampled fish assemblages and examined variation associated with changes in gradients of hydrogeomorphology as expressed by the FPZs. Thus, we examined assemblage variation as patterns of occurrence‐ and abundance‐based beta diversities for the taxonomic composition of assemblages and as functional beta diversity. Overall, we delineated 5 and 6 FPZs in river networks of the FS and G, respectively. Eight fish species were found in the FS river network and seventeen in the G, four of them common to both ecoregions. Functional richness was correspondingly higher in the G river network. Variation in the taxonomic composition of assemblages was driven by species turnover and was only significant in the G river network. Abundance‐based taxonomic variation was significant in river networks of both ecoregions, while the functional beta diversity results were inconclusive. We show that valley‐scale hydrogeomorphology is a significant driver of variation in fish assemblages at a macrosystem scale. Both changes in the composition of fish assemblages and the carrying capacity of the river network were driven by valley‐scale hydrogeomorphic variables. River network hydrogeomorphology as accounted for in the study has, therefore, the potential to inform macrosystem scale community ecology research and conservation efforts. [ABSTRACT FROM AUTHOR]

Abstract We analyze here the nature of research in freshwater macrosystem biology (especially lotic studies) from both conceptual and current research perspectives. The boundaries of permanent and transitional lotic macrosystems from the smallest to largest spatial extents are described. We contrast ecosystem vs. macrosystem research and macroecology vs. macrosystems ecology and provide some examples of representative aquatic macrosystems ecology projects in the USA. We recommend approaches for incorporating certain large‐scale lotic concepts developed over the last 40 yr as the bases for lotic macrosystem studies. Of these, the three most appropriate in chronological order are the River Continuum Concept, the Riverine Ecosystem Synthesis, and the Stream Biome Gradient Concept. Four other concepts would be suitable for testing macrosystem hypotheses after incorporating small to large conceptual or geographic expansions of the models. We suggest future research directions in lotic macrosystem research in areas of climate change and teleconnections among distant organisms and systems and include general recommendations for conducting macrosystem‐level research.

We analyze here the nature of research in freshwater macrosystem biology (especially lotic studies) from both conceptual and current research perspectives. The boundaries of permanent and transitional lotic macrosystems from the smallest to largest spatial extents are described. We contrast ecosystem vs. macrosystem research and macroecology vs. macrosystems ecology and provide some examples of representative aquatic macrosystems ecology projects in the USA. We recommend approaches for incorporating certain large‐scale lotic concepts developed over the last 40 yr as the bases for lotic macrosystem studies. Of these, the three most appropriate in chronological order are the River Continuum Concept, the Riverine Ecosystem Synthesis, and the Stream Biome Gradient Concept. Four other concepts would be suitable for testing macrosystem hypotheses after incorporating small to large conceptual or geographic expansions of the models. We suggest future research directions in lotic macrosystem research in areas of climate change and teleconnections among distant organisms and systems and include general recommendations for conducting macrosystem‐level research. [ABSTRACT FROM AUTHOR]

Addressing continental scale challenges affecting inland aquatic systems requires data at comparable scales. Critically, local in-situ observations for both lotic and lentic ecosystems are frequently fragmented across federal, state and local agencies, and nonprofit or academic organizations and must be linked to other geospatial data to be useful. To advance macro-scale aquatic ecosystem science, better tools are needed to facilitate dataset integration. Key to integration of aquatic data is the linking of spatial data to the hydrologic network. This integration step is challenging as hydrologic network data are large and cumbersome to manage. Here we develop a new R package, hydrolinks , to ease linking aquatic data to the hydrologic network. We use hydrolinks to evaluate the spatial data quality for all lake and stream sites available through the U.S. Water Quality Portal. We find that 76.5% of lake sites and 13.9% of stream sites do not correspond with mapped waterbodies. [ABSTRACT FROM AUTHOR]