The interaction between spatial variation in habitat heterogeneity and dispersal on biodiversity in a zooplankton metacommunity

Assessment of planktonic community diversity and stability in lakes and reservoirs based on eDNA metabarcoding--A case study of Minghu National Wetland Park, China

To evaluate the potential differences in plankton diversity and stability within freshwater lake and reservoir ecosystems, this study employed eDNA metabarcoding to analyze the diversity, assembly mechanisms, stability, and environmental drivers of plankton communities in natural water (Y region) and artificial lake water (M region) at Liupanshui Minghu National Wetland Park, Guizhou Province, China. The study revealed notable regional variations in plankton diversity and assembly mechanisms. Specifically, Shannon, Simpson, and Pielou's evenness indices were higher in the M region, suggesting a more complex species composition compared to the Y region. Analysis of community assembly mechanisms indicated that both regions were influenced by a combination of stochastic and deterministic processes, with stochastic processes serving as the dominant driver. Through LEfSe analysis, Random Forest predictions, and molecular ecological network evaluations, certain OTUs identified as "dual-characteristic" species were consistently highlighted. These species may play a critical role in shaping community composition and contributing to stability. Environmental drivers further clarified these differences. Redundancy analysis (RDA) demonstrated that TDS was the primary factor driving regional differences in key zooplankton species, while EC and DO were significant factors influencing the distribution of key phytoplankton species. Stability assessments, which combined molecular ecological network analysis and the coefficient of variation in species population density, revealed higher stability in the Y region. This indicates that the natural water system (Y region) has a greater resistance to disturbances compared to the artificial system in the M region. The findings provide fundamental support for assessing the health of aquatic ecosystems, as well as for the effective monitoring and biodiversity conservation of lake and reservoir ecosystems.

Novel habitats for biodiversity? A systematic review and meta-analysis of freshwater biodiversity in stormwater management ponds

Stormwater ponds are increasingly becoming a dominant pond type in cities experiencing urban sprawl. These human-made ponds are designed primarily to control flooding issues associated with increased impervious surface in cities and serve to retain sediment and contaminants before flowing to urban downstream waterways. Along with these important functions, constructed ponds including stormwater ponds may be critical in urban freshwater conservation because they often represent some of the few remaining lentic environments (still water; e.g. ponds, wetlands, lakes) in many cities. We currently lack a clear understanding of the role that stormwater ponds play in serving as habitat for freshwater biodiversity. Here, we examined whether stormwater ponds support freshwater biodiversity in cities by reviewing the empirical literature on biotic community responses in urban stormwater ponds across a range of taxonomic groups. We conducted a meta-analysis on empirical papers that quantitatively examined differences in taxonomic richness between stormwater ponds and reference ponds (n = 11 papers, 22 effects). We also examined a broader set of 58 papers to qualitatively synthesize studies on stormwater pond communities and assess various indicators of habitat quality in stormwater ponds. In the studies examined, heterogeneity exists in the habitat quality of stormwater ponds and increased pollutant loads are often reported. However, the results highlight that stormwater ponds tend to contain alpha diversity comparable to reference ponds, and that overall, a range of ecologically important wildlife make use of and inhabit urban stormwater ponds. We find that stormwater ponds can often support communities with broad compositions of taxa, including those that are sensitive or vulnerable to environmental change. We compile recommendations provided within the studies in order to improve our understanding of the management of urban stormwater ponds for biodiversity conservation.

Effects of flow reduction and artificial light at night (ALAN) on litter decomposition and invertebrate communities in streams: A flume experiment

River ecosystems are heavily impacted by multiple stressors, where effects can cascade downstream of point sources. However, a spatial approach to assess the effects of multiple stressors is missing. We assessed the local and downstream effects on litter decomposition, and associated invertebrate communities of two stressors: flow reduction and artificial light at night (ALAN). We used an 18-flow-through mesocosm system consisting of two tributaries, where we applied the stressors, merging in a downstream section. We assessed the changes in decomposition rate and invertebrate community structure in leaf bags. We found no effect of ALAN or its interaction with flow reduction on the litter decomposition or the invertebrate community in the tributaries. Flow reduction alone led to a 14.8 % reduction in decomposition rate in the tributaries. We recorded no effect of flow reduction on the macroinvertebrates community composition in the litter bags. We also observed no effects of the spatial arrangement of the stressors on the litter decomposition and macroinvertebrate community structure downstream. Overall, our results suggest the impact of stressors on litter decomposition and macroinvertebrate communities remained local in our experiment. Our work thus calls for further studies to identify the mechanisms and the conditions under which spatial effects dominate over local processes.

Driving Mechanism of Habitat Quality at Different Grid-Scales in a Metropolitan City

Urban ecosystem dysfunction, habitat fragmentation, and biodiversity loss caused by rapid urbanization have threatened sustainable urban development. Urban habitat quality is one of the important indicators for assessing the urban ecological environment. Therefore, it is of great practical significance to carry out a study on the driving mechanism of urban habitat quality and integrate the results into urban planning. In this study, taking Zhengzhou, China, as an example, the InVEST model was used to analyze the spatial differentiation characteristics of urban habitat quality and Geodetector software was adopted to explore the driving mechanism of habitat quality at different grid-scales. The results show the following: (1) LUCC, altitude, slope, surface roughness, relief amplitude, population, nighttime light, and NDVI are the dominant factors affecting the spatial differentiation of habitat quality. Among them, the impacts of slope, surface roughness, population, nighttime light, and NDVI on habitat quality are highly sensitive to varying grid-scales. At the grid-scale of 1000 to 1250 m, the impacts of the dominant factors on habitat quality is closer to the mean level of multiple scales. (2) The impact of each factor on the spatial distribution of habitat quality is different, and the difference between most factors has always been significant regardless of the variation of grid-scales. The superimposed impact of two factors on the spatial distribution of habitat quality is greater than the impact of the single factor. (3) Combined with the research results and the local conditions of Zhengzhou, we put forward some directions of habitat protection around adjusting urban land use structure, applying nature-based solutions and establishing a systematic thinking model for multi-level urban habitat sustainability.

Detecting patterns of vertebrate biodiversity across the multidimensional urban landscape

Explicit characterisation of the complexity of urban landscapes is critical for understanding patterns of biodiversity and for detecting the underlying social and ecological processes that shape them. Urban environments exhibit variable heterogeneity and connectivity, influenced by different historical contingencies, that affect community assembly across scales. The multidimensional nature of urban disturbance and co-occurrence of multiple stressors can cause synergistic effects leading to nonlinear responses in populations and communities. Yet, current research design of urban ecology and evolutionary studies typically relies on simple representation of the parameter space that can be observed. Sampling approaches apply simple urban gradients such as linear transects in space or comparisons of urban sites across the urban mosaic accounting for a few variables. This rarely considers multiple dimensions and scales of biodiversity, and proves to be inadequate to explain observed patterns. We apply a multidimensional approach that integrates distinctive social, ecological and built characteristics of urban landscapes, representing variations along dimensions of heterogeneity, connectivity and historical contingency. Measuring species richness and beta diversity across 100 US metropolitan areas at the city and 1-km scales, we show that distinctive signatures of urban biodiversity can result from interactions between socioecological heterogeneity and connectivity, mediated by historical contingency.

Abiotic and biotic drivers of temporal dynamics in the spatial heterogeneity of zooplankton communities across lakes in recovery from eutrophication

Seasonal and annual dynamics of the zooplankton community in lakes are affected by changes in abiotic drivers, trophic interactions (e.g., changes in phytoplankton and fish communities and abundances) and habitat characteristics (e.g. macrophyte abundance and composition). However, little is known about the temporal responses of the zooplankton community to abiotic and biotic drivers across lakes at the regional scale. Using a comprehensive 20-year dataset from 20 Danish lakes in recovery from eutrophication, we assessed the seasonal and annual trends in the spatial heterogeneity of zooplankton community across lakes and related it to abiotic and biotic drivers. We found significant seasonality and inter-annual decreases in spatial zooplankton heterogeneity in both shallow and deep lakes, with the decrease in the spatial turnover dominating the temporal dynamics of the beta diversity. For the inter-annual changes, decreased spatial heterogeneity of phytoplankton, macrophytes and fish were important biotic drivers at the regional scale. Using a series of ordinary least squares regressions and model selection with model averaging approaches, we revealed that both local (e.g., total phosphorus, total nitrogen, pH, Secchi depth, alkalinity, Schmidt stability, water temperature) and regional drivers (e.g., air temperature, solar irradiance) were important variables influencing the spatial zooplankton heterogeneity, although the directions depended on the beta diversity measures and water depth. Our results highlight an important role of bottom-up forces through phytoplankton community as well as macrophytes and top-down forces via fishes in driving the temporal changes in zooplankton community composition patterns at the regional scale.