The Ecology of Rivers, Floodplains and Oxbow Lakes

Rivers and their associated landscapes—floodplains, wetlands, and oxbow lakes—represent some of the most dynamic and biologically rich ecosystems on Earth. They are the arteries of the landscape, transporting water, nutrients, and life through both space and time. However, they are also among the most threatened environments, facing pressures from land-use change, hydrological alteration, pollution, and the accelerating effects of climate change. Understanding the ecology of these systems is therefore fundamental not only to advancing ecological theory but also to designing and implementing effective restoration and management strategies.

This Special Issue of Ecologies, now compiled into a book, comprises a diverse set of studies that collectively deepen our understanding of the structure and functioning of freshwater ecosystems across continents and climatic zones. Although the individual contributions vary in scale, method, and focus—from molecular approaches to landscape-level assessments—they share a unifying goal: to elucidate the processes that sustain freshwater biodiversity and ecosystem services in a rapidly changing world.

Across the nine papers included here, several recurring themes emerge. The first is the importance of biodiversity as a diagnostic lens for assessing ecosystem health. Whether the focus is on diatoms, phytoplankton, macroinvertebrates, or stoneflies, each study demonstrates how biological communities integrate environmental information over time and space, providing insights that exceed what can be inferred from physicochemical measurements alone. In the high mountain lakes of Turkey, for instance, diatom assemblages reveal the structuring influence of environmental gradients even in protected, relatively pristine habitats [1]. Likewise, research on lake phytoplankton in Northern Kazakhstan reminds us that even protected water bodies carry signatures of anthropogenic stress, which can be detected through detailed community analysis [2,3,4]. Similarly, in tropical and temperate rivers, macroinvertebrate assemblages serve as sensitive bioindicators, translating subtle environmental changes into measurable ecological signals [5,6,7,8,9,10].

A second theme concerns the multiple stressors and management challenges affecting freshwater systems. From eutrophication and toxic cyanobacterial blooms to the consequences of altered flow regimes and land-use change, the studies within this Special Issue highlight both the complexity of anthropogenic impacts and the potential for ecological resilience. Experimental work on hydrogen peroxide and amino acid treatments and conceptual perspectives on microbial species interactions in cyanobacteria management [11,12] underscore the need for an integrative, systems-based understanding of ecosystem responses. Restoration efforts that ignore the web of microbial and trophic interactions risk unintended consequences; conversely, those informed by ecological principles can promote more stable and self-sustaining outcomes.

Several contributions also emphasize the significance of habitat structure and connectivity. Rivers and floodplains are defined by their physical heterogeneity—flowing and standing waters, sediments, vegetation, and deadwood all contribute to ecological complexity. The inclusion of deadwood, for example, was shown to enhance habitat diversity and support richer macroinvertebrate assemblages in lowland streams [10,13], reinforcing what river restoration practitioners have long suspected: structural elements are not mere debris but keystones of ecological integrity. Likewise, spatial studies on stoneflies in Maryland [7]. and freshwater invertebrates in urban watersheds [8] illustrate how landscape configuration and land-cover patterns shape community composition and water quality, offering guidance for catchment-scale conservation planning.

Another striking insight from this collection is the value of combining traditional ecological methods with modern molecular and analytical tools. DNA barcoding, as applied to identify critical spawning grounds in the Paranapanema River Basin in Brazil [14], exemplifies how genetic techniques can uncover hidden aspects of species distribution and life-history connectivity that would otherwise remain obscure. These approaches expand our capacity to detect ecological patterns, track biodiversity change, and design conservation interventions grounded in empirical evidence [15,16,17].

Taken together, the studies assembled in this volume convey a powerful message: the ecology of rivers, floodplains, and oxbow lakes cannot be reduced to isolated components. These systems are inherently integrated socio-ecological networks, where physical, chemical, and biological processes interact across scales. Maintaining or restoring their health therefore requires an equally integrated approach—one that bridges disciplines, connects local case studies to global insights, and unites scientists with practitioners and policymakers.

For the readership of Ecologies, which includes both researchers and those engaged in applied ecosystem management, this synthesis offers practical and conceptual guidance. Scientifically, it underscores the need for multi-scale, cross-discipline research that links species-level responses to ecosystem-level functions. Practically, it reaffirms that restoration success depends on process-based understanding, not just on engineering solutions. The inclusion of diverse geographic regions—from South America to Eurasia to North America—demonstrates that while each system has unique characteristics, the underlying ecological principles are universal: biodiversity mirrors environmental heterogeneity; connectivity sustains resilience; and management informed by ecological knowledge yields lasting benefits.

Finally, this Special Issue reminds us of the value of open access science. By making these studies freely available, Ecologies supports the dissemination of ecological understanding beyond academic boundaries, fostering dialogue among scientists, practitioners, and decision-makers. In an era when freshwater ecosystems face unprecedented challenges, such accessibility is not merely desirable—it is essential.

In summary, The Ecology of Rivers, Floodplains and Oxbow Lakes celebrates both the diversity of freshwater ecosystems and the creativity of the research community devoted to their study and protection. The collected papers demonstrate that despite regional and methodological differences, a shared scientific vision is emerging: one that recognizes rivers and their floodplains as living, dynamic systems whose future depends on our collective capacity to understand and restore the processes that sustain them.

I wish to extend my sincere thanks to all the authors who contributed to this Special Issue, and to the anonymous reviewers whose thoughtful comments improved the manuscripts significantly. My gratitude also goes to the editorial team of Ecologies and the staff at MDPI for their support in bringing this project to fruition. Finally, I thank the many practitioners and restoration specialists who keep reminding us that understanding ecology is only the first step—putting it into practice is what truly counts.