Macrophyte Assemblages Research Articles

A macroecological analysis of ecological uniqueness of freshwater macrophyte assemblages across Europe and North America

Abstract Understanding spatial variation of species composition at different scales is essential for efficient conservation planning. Here, we investigate ecological uniqueness patterns of freshwater macrophyte assemblages at continental extents. We explored the similarities and differences in the patterns of ecological uniqueness between Europe and North America in relation to species richness and environmental variables using macrophyte presence–absence data in 50 × 50 km grid cells. To describe the ecological uniqueness of macrophyte assemblages, we used an index called ‘local contribution to beta diversity’ (LCBD). First, we used linear regression to evaluate the relationship between ecological uniqueness and species richness. Second, the variation of ecological uniqueness was modelled using environmental variables in generalized additive modelling (GAM). Third, boosted regression tree (BRT) analysis was performed with the same environmental variables to compare BRT results with the results from GAM. The results revealed relatively similar patterns of ecological uniqueness in both continents. The relationship between species richness and ecological uniqueness was overall negative but showed differences in the form and degree of the relationship between Europe and North America. The main driver of ecological uniqueness in both continents was mean annual temperature, with further effects associated with annual precipitation, elevation range, alkalinity and the proportion of freshwaters in a grid cell. Synthesis. Our results showed that species richness and ecological uniqueness may be negatively correlated at large spatial extents, and that the form of the relationship is likely to depend on the species richness profile of the area. The significant influence of climate on the ecological uniqueness of macrophyte assemblages suggests that changes in climate and land use may shape unique macrophyte assemblages. Thus, conservation strategies should consider protection measures, especially in the northern areas with unique macrophyte species assemblages, as they are expected to face many changes in the future. Identifying areas with high ecological uniqueness at different scales is important for efficient implementation of biodiversity conservation practices.

Combined stress of an insecticide and heatwaves or elevated temperature induce community and food web effects in a Mediterranean freshwater ecosystem

Ongoing global climate change will shift nature towards Anthropocene's unprecedented conditions by increasing average temperatures and the frequency and severity of extreme events, such as heatwaves. While such climatic changes pose an increased threat for freshwater ecosystems, other stressors like pesticides may interact with warming and lead to unpredictable effects. Studies that examine the underpinned mechanisms of multiple stressor effects are scarce and often lack environmental realism. Here, we conducted a multiple stressors experiment using outdoor freshwater mesocosms with natural assemblages of macroinvertebrates, zooplankton, phytoplankton, macrophytes, and microbes. The effects of the neonicotinoid insecticide imidacloprid (1 µg/L) were investigated in combination with three temperature scenarios representing ambient, elevated temperatures (+4 °C), and heatwaves (+0 to 8 °C), the latter two having similar energy input. We found similar imidacloprid dissipation patterns for all temperature treatments with lowest average dissipation half-lives under both warming scenarios (DT50: 3 days) and highest under ambient temperatures (DT50: 4 days) throughout the experiment. Amongst all communities, only the zooplankton community was significantly affected by the combined treatments. This community demonstrated low chemical sensitivity with lagged and significant negative imidacloprid effects only for cyclopoids. Heatwaves caused early and long-lasting significant effects on the zooplankton community as compared to elevated temperatures, with Polyarthra, Daphnia longispina, Lecanidae, and cyclopoids being the most negatively affected taxa, whereas Ceriodaphnia and nauplii showed positive responses to temperature. Community recovery from imidacloprid stress was slower under heatwaves, suggesting temperature-enhanced toxicity. Finally, microbial and macrofauna litter degradation were significantly enhanced by temperature, whereas the latter was also negatively affected by imidacloprid. A structural equation model depicted cascading food web effects of both stressors with stronger relationships and significant negative stressor effects at higher than at lower trophic levels. Our study highlights the threat of a series of heatwaves compared to elevated temperatures for imidacloprid-stressed freshwaters.

Ecological Dynamics of Macrophytes in Lentic Water Bodies: A Case Study in Valsad, Gujarat, India

We examined the occurrence of macrophyte diversity and its distribution in the selected lakes of Valsad district, Gujarat, India. There were two main objectives, first examine the macrophyte species diversity in the selected lakes using the Shannon-Wiener diversity index, and the second one was to investigate the impact of environmental parameters on the macrophyte diversity. The canonical correspondence analysis (CCA) was utilized to better understand the relationship between macrophyte communities and environmental conditions. The results showed that from the 50 macrophyte species recorded, 30 species were emergent, 06 species were submerged and 14 species were floating and the overall Shannon-Wiener diversity (H’) of water bodies ranged from 1.917 to 2.584. As per the Sorenson percentage similarity result, there was 80.3 % of an average similarity was present in macrophytes composition (p = 0.0039). The 14 (except phosphate and salinity) out of 16 selected physicochemical variables were statistically significant (p < 0.05) and mentioned in the CCA model, which revealed that macrophyte assemblage structure was strongly associated with Physicochemical parameters. Keywords: aquatic macrophytes, biodiversity, CCA, physicochemical variables, Valsad

Environmental drivers alter PUFA content in littoral macroinvertebrate assemblages via changes in richness and abundance

Shallow littoral areas in lakes are productive and highly diverse ecotonal zones, providing habitats for both invertebrate and vertebrate species. We developed a Bayesian modeling framework to elucidate the relationships between environmental drivers (lake typology, habitat, water chemistry, and latitude) and taxon richness, abundance, as well as the content of polyunsaturated fatty acids (PUFAs) in littoral macroinvertebrate communities in 95 boreal lakes. PUFAs, particularly arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), are critical micronutrients to maintain normal physiological functions in consumers. Lake typology was a significant predictor for PUFA content in the invertebrate assemblages, which was connected to taxon richness and/or abundance. Benthic communities in large humus-poor or nutrient-rich lakes displayed higher abundance, taxon richness, and more PUFA-rich taxa, whereas those in medium- and large-sized humic (color 30–90 mg Pt/L) and humus-rich lakes (color >90 mg Pt/L) were characterized by decreased abundance and subsequently low PUFA content. The abundance, taxon richness, and nutritional quality of the communities were also strongly related to latitude. Lakes with lower pH were characterized by lower benthic invertebrate diversity and low frequency of taxa with high somatic EPA and DHA content. The complexity of littoral habitats dominated by various macrophyte assemblages creates an environment that favors higher benthic abundance and increased presence of taxonomic groups with high PUFA content. Nutritional quality of benthic invertebrates for upper trophic levels can be modulated by a complex interplay between external stressors and abiotic factors that typically shape the structure of littoral benthic communities.

Relationships between Environmental Factors and Functional Traits of Macrophyte Assemblages in Running Waters of Greece

The analysis of plant trait composition has raised significant interest among freshwater ecologists as a complementary approach for assessing the effects of environmental change on ecosystem functions. In this study, we investigated patterns of functional traits of the aquatic macrophyte assemblages of 74 lotic ecosystems of Greece, and we identified associations between species traits and environmental variables (hydromorphological and physicochemical parameters) through testing the hypothesis that the environmental features determine the spatial structure of traits. We allocated 12 traits to a total of 39 hydrophyte species, and we conducted RLQ and fourth corner analysis to explore relationships between species, trait composition, and environmental gradients. Based on the results of the RLQ, a hierarchical cluster analysis was conducted to identify groups of plants that share common trait characteristics. Plants were discriminated into five discrete groups based mostly on their life form (e.g., free-floating, rooted submerged etc.) and their ecological preference for nitrogen levels. Hydromorphological parameters had a higher contribution than physicochemical variables in explaining the total variance of the trait data, with water abstraction, channel substrate, and hydrologic alteration being the most important. Our analysis did not reveal significant bivariate relationships between single traits and environmental parameters, although the five groups of macrophyte assemblages appeared to associate with certain environmental gradients. Free-floating and emergent plants were related to higher concentrations of nutrients, whereas rooted submerged plants were related to higher oxygen concentration and increased pH. In addition, free-floating plants were highly associated with metrics of hydromorphological change. Our findings showed clear discrimination of macrophytes based on their functional composition and association of traits with environmental gradients. Thus, further research could explore whether macrophyte functional groups can serve as indicators of environmental change and the overall ecosystem health.

Salinity as a Key Factor in Structuring Macrophyte Assemblages in Transitional Water Bodies: The Case of the Apulian Coastal Lagoons (Southern Italy)

Coastal lagoons are dynamic transitional water ecosystems hosting valuable biological communities, including rich and diverse macrophyte assemblages. Aquatic macrophytes must cope with large fluctuations of environmental conditions on a spatial and seasonal scale. Salinity is one of the most variable parameters, changing from nearly freshwater to hypersalinity, and it is known to have a strong influence on the composition and structure of macrophyte assemblages. This study is focused on the effect of salinity on macrophyte communities of the eight most important coastal lagoons of Apulia (south-eastern Mediterranean Sea). A set of eleven transitional water body types (sensu Water Framework Directive) were allocated in a range of meso- to hyperhaline lagoons. Macrophyte sampling was carried out between 2011 and 2019, and a total of 324 samples (18 sampling stations × 2 seasons × 9 years) was analyzed. Then, macrophyte occurrence in each transitional water body (T-WB) was expressed as frequency values (%) and assemblages were compared to assess any similarity in relation to four salinity classes (mesohaline, polyhaline, euhaline and hyperhaline). Species richness varied according to the salinity class, being much higher in polyhaline and euhaline T-WBs and strongly decreasing at the extremes of the salinity range (mesohaline and hyperhaline T-WBs). Moreover, the statistical analysis showed a high resemblance of macrophyte assemblages of T-WBs within the same salinity class, which shared a great number of species. Four distinct macrophyte communities were distinguished, reflecting the salinity conditions of different T-WB types and confirming the effectiveness of a lagoon typology based on this descriptor.

Human land-uses homogenize stream assemblages and reduce animal biomass production.

Human land-use change is a major threat to natural ecosystems worldwide. Nonetheless, the effects of human land-uses on the structure of plant and animal assemblages and their functional characteristics need to be better understood. Furthermore, the pathways by which human land uses affect ecosystem functions, such as biomass production, still need to be clarified. We compiled a unique dataset of fish, arthropod and macrophyte assemblages from 61 stream ecosystems in two Neotropical biomes: Amazonian rainforest and Uruguayan grasslands. We then tested how the cover of agriculture, pasture, urbanization and afforestation affected the taxonomic richness and functional diversity of those three species assemblages, and the consequences of these effects for animal biomass production. Single trait categories and functional diversity were evaluated, combining recruitment and life-history, resource and habitat-use, and body size. The effects of intensive human land-uses on taxonomic and functional diversities were as strong as other drivers known to affect biodiversity, such as local climate and environmental factors. In both biomes, the taxonomic richness and functional diversity of animal and macrophyte assemblages decreased with increasing cover of agriculture, pasture, and urbanization. Human land-uses were associated with functional homogenization of both animal and macrophyte assemblages. Human land-uses reduced animal biomass through direct and indirect pathways mediated by declines in taxonomic and functional diversities. Our findings indicate that converting natural ecosystems to supply human demands results in species loss and trait homogenization across multiple biotic assemblages, ultimately reducing animal biomass production in streams.

Environmental Drivers of Functional Structure and Diversity of Vascular Macrophyte Assemblages in Altered Waterbodies in Serbia

There is a gap in the knowledge about how environmental factors affect functional diversity and trait structures of macrophyte communities in altered waterbodies. We used macrophyte and environmental data collected from 46 waterbodies; we extracted data on 14 traits with 43 attributes for 59 species and calculated seven functional diversity indices. We used redundancy analysis (RDA) to investigate the response of functional diversity indices to the environmental variables. To relate traits to environment we performed the analysis on three data matrices: site by environmental variables (R), site by species (L), and species by traits (Q)—the RLQ analysis, and the 4th corner analyses. The RDA showed that the environmental variables explained 47.43% of the variability in the functional diversity indices. Elevation, hemeroby (integrative measure of the impact of all human intervention) of the land cover classes on the banks, and water conductivity were correlated with all diversity indices. We found that the traits characteristic of floating and emergent plants represents a strategy to increase efficiency in light interception under high nutrient concentrations in lowland waterbodies, while submerged plants dominate nutrient-poorer waterbodies at higher altitudes. Future investigations should be focused on the role of functional diversity and the structure of macrophyte communities in the indication of tradeoffs and/or facilitation between ecosystem services that altered waterbodies provide, in order to guide their adequate management.

Exploring factors driving macrophytes in rivers—A case study in Middle Atlas Morocco

AbstractMacrophytes represent a functional compartment that plays multiple and fundamental ecological roles in aquatic environments. They are linked with the other compartments of hydrosystems, both abiotic and biotic, which gives them the ability to integrate environmental conditions and reflect the trophic state of watercourses. Nevertheless, macrophytes in Moroccan rivers have been rarely studied. Thus, the main objective of the present work is to study these plants by determining the environmental factors that control their presence and distribution in the watercourses of the upper Oum Er‐rbia basin (Middle Atlas Morocco). From June 2018 to June 2019, 14 sites spread over five rivers were monitored monthly to describe macrophytic communities and investigate their ecological determinism. We used a principal component analysis to establish each river's typology and a detrended correspondence analysis to explore macrophyte assemblages. Canonical correspondence analysis was used to determine the hydrochemical parameters of water that govern the development and distribution of macrophyte species in the upper Oum Er‐rbia basin. The Amengous river stands out from the other surveyed rivers for its exceptional richness of macrophytic species. This richness is often associated with the enrichment of the aquatic environment by nitrogen and phosphate inputs. Furthermore, in some rivers, such as Oum Er‐rbia, nutrient enrichment plays a secondary function in comparison to the hydromorphological descriptors that tend to be more important for macrophyte composition and distribution.

Distribution patterns of macrophytes in shallow lakes of the lower Paraná River floodplain: Associations with environmental conditions

Abstract Macrophytes play key functional and structural roles in floodplain shallow lakes (SL), determining the maintenance of ecosystem functions and sustaining several productive activities. We assessed the relationship between macrophyte community structure (composition, species abundance, and plant diversity) and environmental features (SL dynamics, connectivity, morphometry, flood frequency, and water and sediment physical and chemical variables) in the Lower Paraná River floodplain. Our main hypothesis was that SL macrophyte distribution depends on direct and indirect environmental controls operating at multiple scales. The SL dynamics during the April–November 2017 Paraná River pulse were described according to their coverage changes (vegetation, and turbid or clear open water), which were assessed with supervised classifications on Landsat 8‐OLI scenes. Twenty‐five SL of the Lower Paraná River floodplain were selected to represent all the SL dynamics identified. Ten SL were permanently connected and 15 were disconnected from watercourses. Water and sediment physical and chemical characteristics, macrophyte assemblage composition, and plant species abundance were surveyed at each site in the 2018 summer. Also, SL morphometric parameters and flood frequency were estimated from ancillary geographic data. The direct controlling factors of macrophyte assemblages were water ammonium and water nitrate concentrations, turbidity, and flood frequency. No clear effects of environmental conditions on macrophyte diversity were found. The connectivity of SL with watercourses affected their water and sediment physical and chemical features. Also, SL dynamics during the 2017 pulse were related to flood frequency. As connectivity to watercourses affects SL chemical and physical variables, and SL dynamics were associated with flood frequency, connectivity and SL dynamics indirectly influenced macrophyte assemblage composition. This study improved our understanding of macrophyte distribution patterns in the study area, which was related to several environmental variables operating at different scales. Our results highlight the importance of the variability of hydrological connectivity in promoting environmental heterogeneity in river floodplain systems, which is central to their functioning, and the high biodiversity that characterises these environments.

Quantifying the ecological impacts of alien aquatic macrophytes: A global meta‐analysis of effects on fish, macroinvertebrate and macrophyte assemblages

Abstract Biological invasions constitute a pervasive and growing threat to the biodiversity and functioning of freshwater ecosystems. Macrophytes are key primary producers and ecosystem engineers in freshwaters, meaning that alien macrophyte invasions have the capacity to alter the structure and function of recipient aquatic ecosystems profoundly. Although prevailing wisdom holds that alien macrophyte invasions tend to compromise freshwater ecosystem structure and function, the ecological impacts of alien macrophyte invasion have not been quantitatively reviewed to date. Here we present a global meta‐analysis of 202 cases from 53 research articles, exploring the impacts of alien macrophyte invasion on the abundance and diversity of three ubiquitous and ecologically important focal groups, which together comprise the bulk of non‐microbial freshwater biodiversity: resident macrophytes, macroinvertebrates and fish. Our synthesis includes data from all continents except Antarctica and Asia, covering 25 alien macrophyte species, but reveals considerable taxonomic and geographical biases in knowledge. Meta‐analysis results reveal that invasion by alien macrophytes has an overall negative impact on taxonomic diversity of the three focal groups, but no consistent effect on abundance. At a finer resolution, we detect a strong negative effect of alien macrophyte invasion on resident macrophyte abundance and diversity, and a significant but smaller positive effect of submerged alien macrophyte invasion on macroinvertebrates. Effects on fish appear inconsistent. Our findings emphasise the importance of context‐ and taxon‐specific ecological research in informing appropriate and proportionate management of alien macrophyte invasions, since alien macrophyte impacts are not consistently negative. We also identify significant geographical and taxonomic limitations in existing studies, quantitative data being lacking for many alien taxa.

The effect of crude oil pollution on macrophyte assemblage in Kporghor River, southern Nigeria

A study of the effects of crude oil pollution on macrophyte assemblage was carried out in Kporghor River, Rivers State. Standard procedures were used in data collection. Temperature, total dissolved solutes, dissolved oxygen, pH and electrical conductivity were taken in-situ using Extech multi-parameter equipment while biological oxygen demand was incubated in a BOD bottle and determined using standard methods. Aquatic macrophytes were sampled with 0.5m × 0.5m quadrant and estimates of the percentage cover of each species inside the 0.5 × 0.5 m quadrant was transformed onto a scale based on Braun-Blanquet. The diversity and abundance of the different species were higher in Station (2), followed by station (3) and Station (1) respectively. Bambus vulgaris having a percentage of (29.7%) being the most abundant with percentage abundance, Cyrtospermum senegalense (8.72%), Nymphaea lotus (5.81), Acanthophoenix crinite (4.65%), Pistia stratiotes and Eichornia grassippes (2.91%) respectively. Unidentified species of macrophyte collected from the sampling area accounted for 11.62% species abundance. The result of physico-chemical parameters: temperature (29±0.63oC to 29.15±0.72oC), pH (6.03±0.12 to 6.9±0.15), TDS (36.23±6.82mg/ to 40.05±5.30mg/L), conductivity (4430±792.42μS/cm to 4914.75±569.42μS/cm), DO (5.20±1.20mg/L to 5.50±0.49mg/L) and BOD (3.08±0.94mg/L to 3.40±0.61mg/L). Copper (0.015mg/L) level was below WHO, SON and DPR standards for Cu in water bodies. Cadmium (0.10mg/L), Lead (0.18mg/L) and Nickel (0.28mg/L) concentrations were above WHO permissible limits. The abundance of Bambusa vulgaris (an alien species) suggests its adaptation to the study area. However, mitigation actions are recommended to restore this polluted ecosystem.

Eutrophication drives regime shift via changes in stoichiometric homeostasis-based submerged macrophyte assemblages

Homeostasis for phosphorus (HP) in submerged macrophytes may influence the susceptibility of lakes to regime shifts; however, the mechanisms linking submerged macrophyte HP to regime shifts remain unclear. We conducted an in situ mesocosm experiment to compare the dynamic responses of a high-HP species, Potamogeton maackianus, and a low-HP species, Hydrilla verticillata, to different phosphorus (P) level gradients, as well as their effects on phytoplankton inhibition. The biomass of P. maackianus under mesotrophic P (MP; P concentration 0.05 mg L−1) and eutrophic P (EP; P concentration 0.10 mg L−1) conditions was either non-significantly different from, or lower than that under oligotrophic P conditions (OP; P concentration under detection limit of 0.01 mg L−1). Conversely, H. verticillata biomass under EP was significantly higher than that under MP on day 90, whereas it died under OP. This variable response of submerged macrophyte species to P level gradients increased the relative growth advantage of H. verticillata compared to P. maackianus during eutrophication. The inhibition ratio of phytoplankton (IRP) for P. maackianus was ~15 times higher than that for H. verticillata under EP. Our study demonstrated a trend that submerged macrophyte assemblage IRP increased along with its assemblage HP. Thus, the changes in submerged macrophyte assemblages from high-HP species-dominance to low-HP species-dominance would erode its phytoplankton inhibition capacity, and further promote the regime shift from a clear-water state to a turbid state. Our results advance the regime shift theory from an ecological stoichiometry perspective and highlight the importance of high-HP submerged macrophyte species in the restoration of eutrophic lakes.

High abundance of a single taxon (amphipods) predicts aquatic macrophyte biodiversity in prairie wetlands

Conservation programs often aim to protect the abundance of individual species and biodiversity simultaneously. We quantified relations between amphipod densities and aquatic macrophyte (large plants and algae) diversity to test a hypothesis that biodiversity can support high abundance of a single taxonomic group. Amphipods (Gammarus lacustris and Hyalella azteca) are key forage for waterfowl and are declining in the Prairie Pothole Region of North America. We sampled a large gradient of amphipod densities (0–7050 amphipods/m3) in 49 semi-permanent wetlands, and 50% of the study wetlands had high amphipod densities (> 500 amphipods/m3). Generalized linear models revealed G. lacustris and H. azteca densities increased exponentially with macrophyte diversity indices. Further, H. azteca densities were greatest at moderate levels of submersed vegetation biomass. Community analyses showed both amphipod species were positively associated with diverse macrophyte assemblages and negatively associated with high coverage of cattails (Typha spp.), a taxon that creates monotypic stands, as well as bladderwort (Utricularia spp.), a carnivorous plant. Our results indicate that amphipods could be used as an umbrella species for protecting diverse macrophyte communities in semi-permanent and permanent wetlands of North America’s Prairie Pothole Region.

Coastal degradation impacts on green turtle's (Chelonia mydas) diet in southeastern Brazil: Nutritional richness and health

This study evaluated the influence of environmental degradation on the nutritional value of the main marine macrophytes consumed by green sea turtles (Chelonia mydas) in areas with different degrees of urbanization. Macrophyte assemblages in the highly urbanized area (HUa) showed lower richness compared to the lightly urbanized area (LUa) (Mann-Whitney U test: 10.0 ± 3.6 SD genera and 11.9 ± 4.2 taxa per transect vs. 20.1 ± 7.0 genera and 23.5 ± 9.2 taxa per transect) respectively. Also, diet was poorer with 4.0 ± 1.6 genera per turtle (vs. 8.5 ± 4.0 in HUa) and less diverse with Shannon index of diversity = 0.45 ± 0.29 (vs. 0.64 ± 0.46 in LUa). Body condition was similar in both areas. About half of individuals were classified as having normal body condition, 14–15% as underweight and 23–34% as being emaciated. Fibropapillomatosis prevalence (χ2 = 8.720; n = 222; df = 1; p = 0.003) was higher in the HUa but, in affected animals, severity was marginally non-significant (χ2 = 5.721; n = 82; df = 2; p = 0.057). Significant differences in energy content (kcal) were detected between areas in both summer (S) and winter (W). All ANOVAs on total lipids (F = 22.15 [S] and 30.39 [W]), total water-soluble proteins (F = 327.65 [S] and 64.42 [W]) and total carbohydrates (F = 70.90 [S] and 27.62 [W]) showed high significance (p < 0.001). Carotenoids concentration yielded significant results for Halodule in summer and Hypnea in winter (ANOVAs, F = 39.42 and 13.07, respectively). For both, tests revealed that concentration was higher in LUa than HUa. High levels of phycobiliproteins and proteins in this area probably reflect nitrogen accumulation. Frequency and severity of fibropapillomatosis suggest that urbanization-caused alterations in species diversity and in chemical composition of marine plants affect green turtles' health. Light abstractThe use of coastal areas by humanity is widespread and increasing. The impacts caused to the coastal environment, be it terrestrial, estuarine or marine, are important and affect numerous species. Our study evaluated the influence of environmental degradation on the nutritional value of the main algae eaten by the green turtle, one of the very few marine megaherbivores (those herbivores with body mass above 10 kg). Diet in the highly urbanized area was richer in proteins, lipids and carbohydrates (sugars) and lower in carotenoids (photosynthetic and photoprotectant pigments in algae and plants; precursors of vitamin A involved in oxygen transport in animals—animals do not synthetize such molecules). High levels in phycobiliproteins (photosynthetic pigments present in some algae) and proteins in the highly urbanized area probably result from organic pollution and nitrogen accumulation in coastal waters. Nitrogen compounds dissolved in water are a threat to vertebrates due to its toxicity and negative effects on the immune system. Our results suggest that algae chemical composition and severity of fibropapillomatosis (tumors caused by a herpesvirus in green sea turtles) are directly related through environmental alterations caused by urbanization.

Disentangling the roles of plant functional diversity and plaint traits in regulating plant nitrogen accumulation and denitrification in freshwaters

Abstract There is a growing recognition that functional measures of diversity, based on quantification of functionally important species traits, are useful for explaining variation in ecosystem processes. However, the mechanisms linking functional diversity to different processes remain poorly understood, hindering development of a predictive framework for ecosystem functioning based on species traits. The current understanding of how the functional traits of aquatic plants (macrophytes) affect nitrogen (N) cycling by regulating microbial communities and their activity in freshwater habitats is particularly limited. Denitrifying bacteria are typically associated with the roots of both aquatic and terrestrial plants and denitrification is the main cause of loss of N from ecosystems. Disentangling the interplay between plants and microbial denitrifiers is key to understanding variation in rates of denitrification from local to landscape scales. In a mesocosm experiment, we varied the species richness (monocultures or two‐species mixtures) and composition of macrophytes. We quantified effects of both macrophyte functional diversity, quantified as functional trait dissimilarity, and functional trait composition, quantified as community weighted mean trait values, on N removal in wetlands. We used structural equation modelling to disentangle the direct and indirect influences of traits on N accumulation in plant biomass, denitrification activity and abundance of key bacterial denitrification genes (nirS and nirK). Both functional diversity and functional trait composition regulated N removal, explaining 70%–94% variation in the underlying ecosystem processes. Increased macrophyte functional diversity increased plant N accumulation, and indirectly enhanced denitrification by increasing denitrification gene abundance. Among traits, greater plant relative growth rates, specific leaf area and above‐ground biomass increased plant N accumulation. Denitrification activity increased with increasing below‐ground biomass but decreased with increasing root diameter. These findings improve our understanding of N removal in freshwater wetlands dominated by macrophytes, and have broad ecological implications for wetland management targeting enhanced ecosystem services. Our results highlight the potential for optimizing denitrification and plant N accumulation in wetlands and thereby improving water purification by increasing macrophyte functional diversity and ensuring the presence of key traits in macrophyte assemblages. A free Plain Language Summary can be found within the Supporting Information of this article.

Spatial and temporal variation of the macrophyte assemblage in Santo Tomás, a wetland in the Caribbean Colombian

Abstract: Aim The associated flood events to floodplain of many rivers in the world affect the composition and structure of aquatic biota due the water levels variation can ensure ecological integrity of associated wetlands. This study describes the spatial and temporal variation in the macrophyte assemblage in the Santo Tomás wetland during seasonally flood-pulsed of the Magdalena River (North of Colombia). Methods For eight months, between 2017 and 2018 samplings were carried out in three stations for composition and abundance of aquatic macrophytes. Spatio-temporal pattern of richness was estimated with Chao methodology and vegetation cover was calculated using Kruskal-Wallis and U Mann-Whitney tests. A range abundance curve was used for species dominance between samplings and stations. A non-metric multidimensional scaling (nMDS) was used to analyze the Spatio-temporal distribution, Canonical Correspondence Analysis (ACC) was performed to relate the physicochemical variables to the species composition. Results A total of 24 species of aquatic plants distributed in 23 genera and 15 families were registered in the transects. The most abundant species (% of vegetation cover) were Ipomoea aquatica (19%), followed by Ludwigia helminthorrhiza (14%) and Eichhornia azurea (13%). The most frequent life form was free-floating, followed by the emergent one. The Spatio-temporal changes and the highest values of richness and vegetation cover in the Santo Tomás wetlands occurred during the filling and high waters period. L. helminthorrhiza, E. azurea, Pistia stratiotes, Neptunia oleracea, I. aquatica, Salvinia auriculata, and Hymenachne amplexicaulis were the most dominant species. The quality water of Santo Tomás Wetlands showed spatial and temporal variations during flooding pulse and some physicochemical variables such as organic matter (COD, BOD5), pH, depth, ammonia, and fecal coliforms were related to macrophyte community composition Conclusions Spatial and temporal changes of aquatic plants in Santo Tomás wetlands were related to the flooding pulse of Magdalena River.

Effects of different growth form submerged macrophyte assemblages on biomass accumulation and water purification

种植水生植物，尤其是沉水植物，是目前广泛应用于受损水体的最主要的生态修复方法之一. 研究不同生长型沉水植物组合对水体理化因子的影响及营养物质的去除效率可为受损水生生态系统修复提供重要的科学依据. 本研究以我国水体修复中常用的3种不同生长型沉水植物苦草(Vallisneria natans)、黑藻(Hydrilla verticillata)和穗状狐尾藻(Myriophyllum spicatum)为研究对象，采用1种生长型种植和2种生长型及3种生长型混种模式，研究不同生长型沉水植物组合及其不同生长阶段对实验系统水质指标及氮、磷等营养物质去除率的影响. 结果表明，所有植物组合处理均显著提高了系统中总氮、总磷和氨氮去除率; 在实验前中期总氮、总磷和氨氮去除率最高. 从本实验受试物种组合来看，1种和2种生长型组合比3种生长型组合具有更高的生物量累积量和总氮去除率. Pearson相关性分析显示，实验系统中的pH、DO浓度与植物总生物量呈显著正相关，总氮、总磷、氨氮浓度均与植物总生物量呈显著负相关. 建议在受损浅水水生态系统修复过程中，根据生态修复不同阶段考虑不同生活型、生长型和功能群的水生植物组合; 在生态修复过程中需加强管理，如水生植物收割等，才能达到最好的修复效果.;Aquatic plants are important components of freshwater ecosystems and constitute a dominant actor in many shallow lakes. Planting aquatic plant, especially for submerged macrophytes, is one of the most important ecological restoration methods widely used in damaged shallow freshwater bodies. However, previously studies have mainly focused on the effects of macrophyte richness on biomass and water quality. Little is known about the effect of different assemblages with various growth form submerged macrophyte on biomass accumulation and water purification. In this study, three different growth form submerged plants, Vallisneria natans, Hydrilla verticillata and Myriophyllum spicatum, which are commonly used in water ecological restoration in China, were selected to test the effect of different growth form submerged macrophyte assemblages on water quality and nutrients removal rate. Our results showed that all different growth form assemblages have obvious purification effects on total nitrogen, total phosphorus and ammonia nitrogen, and higher purification effects were observed in the early and middle stage of the experiment. From different combinations, one and two growth form combinations have higher biomass accumulation and higher total nitrogen removal efficiency than three growth form combinations. Pearson correlation analysis showed that the pH, and DO in the experimental system were significantly positively correlated with the total biomass, and the concentrations of total nitrogen, total phosphorus and ammonia nitrogen were significantly negatively correlated with the total biomass. Our results suggest that in order to get the best restoration results, we need to take various factors into consideration during the process of ecological restoration, including different life form and growth form aquatic plant assemblages, harvesting aquatic macrophytes, etc.

Anthropogenic Stressors in Upland Rivers: Aquatic Macrophyte Responses. A Case Study from Bulgaria.

Upland rivers across Europe still exhibit undisturbed conditions and represent a treasure that we cannot afford to lose. We hypothesize that the combination of pristine and modified conditions could demonstrate biological responses along the stressor gradients. Thus, the response of aquatic macrophyte communities to anthropogenic stressors along upland rivers in Bulgaria was studied. Six stressors were selected out of 36 parameters grouped into hydromorphological, chemical variables and combined drivers (catchment land use). The stressors strongly affected species richness on the basis of biological type (bryophytes vs. vascular plants) and ecomorphological type (hydrophytes vs. helophytes). Hydrological alteration expressed by the change of the river’s base flow and altered riparian habitats has led to a suppression of bryophytes and a dominance of riverbank plant communities. Seventy-five percent of mountain sites were lacking bryophytes, and the vegetation at semi-mountainous sites was dominated by vascular plants. It can be concluded that hydropeaking, organic and inorganic pollution, and discontinuous urban structures caused important modifications in the aquatic macrophyte assemblages. Macrophyte abundance and the biological and ecomorphological type of aquatic macrophytes reflect multi-stressor effects in upland rivers.

Variabilidad estructural de la comunidad de macrófitas en un gradiente pluviométrico en la provincia de Chubut

Mallines are Patagonian wetlands characterized by permanent waterlogging on its soils, sustaining small shallow lakes that hosts a vast biodiversity. In these ecosystems, aquatic plants (i.e. macrophytes) develop different life forms adapted to humid conditions, allowing them to regulate the physical and chemical conditions of the mallín. A distinctive characteristic of Patagonia is the exponential west-east decrease in rainfall, which generates three biozones: forest, ecotone and steppe. These biozones have been typified using landform plants, but whether macrophytes assemblages are related to each biozone or not has not been evaluated yet. The aim of this work is to compare the attributes of the macrophyte and wetlands landform plants community in each biozone. During the 2013-2014 austral Summer, 20 shallow lakes were sampled in the west province of Chubut, assessing macrophyte richness and physical and chemical water variables. Macrophytes were classified according to their life forms, origin, and its diversity was calculated. A total of 62 taxa were determined, most of them corresponding to the Cyperaceae, Poaceae and Ranunculaceae families. The steppe exhibited alkaline pH values, and higher conductivity and soluble reactive phosphorus (SRP) than the ecotone and the forest. High SRP values favored the abundance of macrophytes and macroalgae. However, three sites were eutrophic, exhibiting high chlorophyll a and total phosphorus values. Those sites showed higher abundances of macroalgae and emerging macrophytes. The sampled shallow lakes would act as reservoirs of macrophyte diversity at both local and regional scales. Thus, understanding the relationships among macrophytes and environmental variables could be useful for the mallines biodiversity conservation plans.