Macrophyte Community Structure Research Articles

Relationship between potentially toxic elements and macrophyte communities in the Sava river

Freshwater ecosystems are at significant risk of contamination by potentially toxic elements (PTEs) due to their high inherent toxicity, their persistence in the environment and their tendency to bioaccumulate in sediments and living organisms. We investigated aquatic macrophyte communities and the concentrations of As, Cu, Cd, Cr, Pb, Zn, Ni and Fe in water and sediment samples to identify a pollution pattern along the Sava River and to investigate the potential impact of these PTEs on the diversity and structure of macrophyte communities. The study, which covered 945 km of the Sava River, showed a downstream increase in sediment concentrations of the analyzed elements. Both species richness and alpha diversity of macrophyte communities also generally increase downstream. Ordinary and partial Mantel tests indicate that macrophyte communities are significantly correlated with sediment chemistry, but only weakly correlated with water chemistry. In the lowland regions (downstream), beta diversity decreases successively, which can be attributed to an increasing similarity of environmental conditions at downstream sites. Species richness is relatively low at sites with low concentrations of Cr, Cd, Fe, and Cu in the sediment. However, species richness increases to a certain extent with increasing element concentrations; as element concentrations increase further, species richness decreases, probably as a result of increased toxicity. Some species that are generally more tolerant to high concentrations of PTEs are: Ceratophyllum demersum, Iris pseudacorus, Najas marina, Butomus umbellatus, Vallisneria spiralis, Potamogeton gramineus and Bolboschoenus maritimus maritimus. Potamogeton perfoliatus and the moss species Cinclidotus fontinaloides and Fontinalis antipyretica have narrow ecological amplitudes in relation to the concentrations of PTEs in the sediment.

Species Diversity and Composition of Macrophytes in Shallabugh Wetland, Ganderbal, Jammu, and Kashmir, India

Macrophyte diversity, richness, and composition of the Shallabugh wetland Reserve, one of the Important Bird and Biodiversity Area in India. The wetland shows the presence of 39 plant species of 27 families and three tree species belonging to three families and a diversity index of H = 3.12 and Evenness e^H/S = 0.5836. The high Importance Value Index (IVI=22.8) was recorded for Typha latifolia, followed by Ceratophyllum demersum (IVI=19.2). The shift in macrophyte community structure is evidenced by the local extinction of Nelumbo nucifera from the Shallabugh wetland area and the near-disappearance of some economically important plants such as Trapa natans (IVI= 0.24). The investigation of various aspects of the wetland ecology of Shallabugh reveals that species composition has witnessed great changes over the years. The conversion of the 141 hectares of wetland into grassland gave way for terrestrial species to flourish. The study serves as the baseline study of the macrophyte community composition and structure of the Shallabugh wetland.

Minor effect of wind exposure and littoral slope on macrophyte characteristics in non-impacted lowland lakes of Poland.

Aquatic vegetation is a reliable indicator of the ecological condition of surface waters. Abundance, composition and spatial structure of aquatic communities are shaped by an array of factors, which include both natural abiotic features of an ecosystem and external influences. We investigated whether the physical features, i.e., wind exposure and slope of the lake basin, have a significant impact on the taxonomic composition and spatial structure of macrophyte communities from non-impacted, highly alkaline, lowland lakes of the European plains (Poland). We further examined whether these features can affect the classification of the ecological status of lakes assessed in accordance with the Water Framework Directive requirements. Morphological, botanical and physicochemical data from 260 transects in 16 non-disturbed lakes of Polish lowlands surveyed in the years 2011-2016 were analysed. For each transect, littoral slope and wind exposure were calculated. Additionally, the total phosphorus concentration was used as a proxy of water trophy. The relationships between environmental variables and macrophyte indices as well as the syntaxonomic composition of aquatic and rush vegetation (dependent variables) were analysed using multidimensional ordination techniques (redundancy analysis, variation partitioning and indicator values), correlation and regression analysis. Among the three analysed environmental factors (littoral slope, wind exposure and water trophy), in almost all cases the latter explained the highest variance in the macrophyte community, while the contribution of the first two was at most moderate, weak or usually statistically insignificant. However, lakes with steeper slopes were more frequently inhabited by stoneworts and had better ecological status than those with a gentle littoral shape. This may be attributed to the links between lake morphometry and rate of eutrophication, with deep lakes supporting more effective dilution of substances. Furthermore, lower light requirements of charophytes than of higher plants and the capacity to growth in unstable sediments facilitate charophyte establishment in deeper and steeper parts of the littoral over higher plants. Our findings suggest that in lowland lakes with relatively small areas, moderate depths and low wind exposure typical of European plains, slopes and weaving do not hamper vegetation development and do not negatively affect the macrophyte assessment of ecological status. In such ecosystems, eutrophication seems to be a more important factor determining aquatic vegetation than physical features.

Responses of submerged macrophytes to different particle size microplastics and tetracycline co-pollutants at the community and population level

Microplastics (MPs) and antibiotics are ubiquitous in aquatic ecosystems, and their accumulation and combined effects are considered emerging threats that may affect biodiversity and ecosystem function. The particle size of microplastics plays an important role in their combined effects with antibiotics. Submerged macrophytes are crucial in maintaining the health and stability of freshwater ecosystems. However, little is known about the combined effects of different particle size of MPs and antibiotics on freshwater plants, particularly their effects on submerged macrophyte communities. Thus, there is an urgent need to study their effects on the macrophyte communities to provide essential information for freshwater ecosystem management. In the present study, a mesocosm experiment was conducted to explore the effects of three particle sizes (5 µm, 50 µm, and 500 µm) of polystyrene-microplastics (PSMPs) (75 mg/L), tetracycline (TC) (50 mg/L), and their co-pollutants on interactions between Hydrilla verticillata and Elodea nuttallii. Our results showed that the effects of MPs are size-dependent on macrophytes at the community level rather than at the population level, and that small and medium sized MPs can promote the growth of the two test macrophytes at the community level. In addition, macrophytes at the community level have a stronger resistance to pollutant stress than those at the population level. Combined exposure to MPs and TC co-pollutants induces species-specific responses and antagonistic toxic effects on the physio-biochemical traits of submerged macrophytes. Our study provides evidence that MPs and co-pollutants not only affect the morphology and physiology at the population level but also the interactions between macrophytes. Thus, there are promising indications on the potential consequences of MPs and co-pollutants on macrophyte community structure, which suggests that future studies should focus on the effects of microplastics and their co-pollutants on aquatic macrophytes at the community level rather than only at the population level. This will improve our understanding of the profound effects of co-pollutants in aquatic environments on the structure and behavior of aquatic communities and ecosystems.

Unveiling novel perspectives on niche differentiation and plasticity in rhizosphere phosphorus forms of submerged macrophytes with different stoichiometric homeostasis

Stoichiometric homeostasis is the ability of organisms to maintain their element composition through various physiological mechanisms, regardless of changes in nutrient availability. Phosphorus (P) is a critical limiting element for eutrophication. Submerged macrophytes with different stoichiometric homeostasis regulated sediment P pollution by nutrient resorption, but whether and how P homeostasis and resorption in submerged macrophytes changed under variable plant community structure was unclear. Increasing evidence suggests that rhizosphere microbes drive niche overlap and differentiation for different P forms to constitute submerged macrophyte community structure. However, a greater understanding of how this occurs is required. This study examined the process underlying the metabolism of different rhizosphere P forms of submerged macrophytes under different cultivation patterns by analyzing physicochemical data, basic plant traits, microbial communities, and transcriptomics. The results indicate that alkaline phosphatase serves as a key factor in revealing the existence of a link between plant traits (path coefficient = 0.335, p < 0.05) and interactions with rhizosphere microbial communities (average path coefficient = 0.362, p < 0.05). Moreover, this study demonstrates that microbial communities further influence the niche plasticity of P by mediating plant root P metabolism genes (path coefficient = 0.354, p < 0.05) and rhizosphere microbial phosphorus storage (average path coefficient = 0.605, p < 0.01). This research not only contributes to a deeper comprehension of stoichiometric homeostasis and nutrient dynamics but also provides valuable insights into potential strategies for managing and restoring submerged macrophyte-dominated ecosystems in the face of changing nutrient conditions.

Macrophyte communities as bioindicator of stormwater pollution in rivers: a quantitative analysis.

Macrophytes are one of the important indicators used in assessing the anthropic impact on aquatic ecosystems. The structure of macrophyte communities of two rivers were compared by species composition, dominant species and projective cover using statistical methods. It is shown that the influence of storm runoff on these rivers is manifested in the form of a change in the dominant species composition. Based on the statistical analysis carried out, it can be argued that, despite the peculiarities of the flora composition of each of the rivers, the influence of storm runoffs largely neutralizes this specificity, determining the situation in local areas immediately below the runoff. In the area of the effluent discharge the dominance of individual species and an increase in the area overgrown with macrophytes was observed. In the area of stormwater discharge on the Psel River, species were usually present: Nuphar lutea, Ceratophyllum demersum, Myriophyllum spicatum and on the Bystrica River-Glyceria maxima, Sagitaria sagittiformis, Stuckenia pectinata and Potamogeton crispus. The use of the NMDS method has been found to provide good insight into the structural rearrangements in macrophyte communities affected by runoff from stormwater systems.

Water depth modulates the species richness–biomass relationship in submerged macrophytes

The effect of biodiversity on ecosystem productivity has been a controversial issue in ecological research. The species richness–productivity relationship is highly variable in natural ecosystems, with a positive relationship being one of the most commonly observed relationships. Previous regional studies from terrestrial ecosystems have demonstrated that environmental gradients can regulate the species richness–productivity relationship. However, how this relationship varies in freshwater ecosystems across spatial environment gradients remains unclear. In this study, we propose that the species richness–productivity relationship can be modulated by the water depth. Here, we surveyed the submerged macrophyte community structure by establishing 24 transects and 642 quadrats in Erhai Lake, Yunnan Plateau, China. Our findings highlight that the species richness–productivity relationship gradually changed from slightly positive to strongly positive as the environment became more light-limited with the increasing water depth, supporting the stress-gradient hypothesis. The results from this study provide new insights into the biodiversity–ecosystem functioning relationships and in managing lake macrophyte communities and productivity.

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.

Long-Term Observations over the Structure of Macrophyte Communities in Floodplain Water Bodies of the Chornobyl Exclusion Zone

The study is based on long-term observations (1998-2021) over the species richness and cenotic activity of macrophytes of floodplain water bodies of the Chornobyl exclusion zone. During this period, the species composition of macrophytes of the studied water bodies remained almost unchanged. The lists of species found in 1998 differ from those registered in 2021 only by three species, including &lt;i&gt;Nymphaea alba, Trapa natans&lt;/i&gt; (registered only since 2007), and &lt;i&gt;Utricularia minor&lt;/i&gt; (found only in 1998, whereas in subsequent years was not observed at all). In the studied water bodies, macrophytes are not diverse in their species composition; their cenotic structure is simple, whereas overgrowing intensity of water surface is high. The presence of rare species of the boreal complex, including primarily &lt;i&gt;Hottonia palustris, Potamogeton acutifolius&lt;/i&gt;, and &lt;i&gt;Callitriche cophocarpa&lt;/i&gt;, makes these water bodies objects of protection and research. In 1998, a common feature of the vegetation cover of all studied floodplain water bodies was a predominance of macrophyte communities, in which the species of river and lake ecosystems, as well as indicator species of increased water logging processes, were registered. At the present time, natural structure of macrophyte communities of floodplain water bodies of the Prypyat River, which was deteriorated as a result of the construction of flood-protection hydraulic structures, is gradually recovered. The peculiarities of the distribution of macrophytes at the present time are indicative of the improvement of water exchange in floodplain water bodies. The chronic ionizing radiation influencing the biota of the studied water bodies for more than 30 years did not result in significant changes in the floristic and cenotic composition of macrophytes. Certain changes are conditioned by changes in hydrological and hydrochemical regime of the floodplain of the Prypyat River.

Waterbodies in the Floodplain of the Drava River Host Species-Rich Macrophyte Communities despite Elodea Invasions

The contribution discusses macrophyte communities in natural and man-made waterbodies located on the active floodplain along the Drava river (Slovenia). We presumed that these different types of wetlands host a great number of macrophyte species, but this diversity may be affected by the presence of alien invasive species Elodea canadensis and E. nuttallii. Presence, relative abundance, and growth forms of plant species along with selected environmental parameters were monitored. Correlation analyses and direct gradient analyses were performed to reveal the possible relations between the structure of macrophyte community and environmental parameters. Number of macrophytes in surveyed water bodies varied from 1 to 23. Besides numerous native species we also recorded Elodea canadensis and E. nuttallii, which were present in 19 out of 32 sample sites, with E. nuttallii prevailing. The less invasive E. canadensis was absent from ponds and oxbow lakes but relatively abundant in side-channels, while E. nuttallii was present in all types but dominant in ponds. The most abundant native species were Myriophyllum spicatum and M. verticillatum, Ceratophyllum demersum and Potamogeton natans. Correlation analyses showed no negative effect of the invasive alien Elodea species to the species richness and diversity of native flora. Positive correlation between the abundance of E. nuttallii and temperature of the water was obtained.

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.

The Effect of Hydro-Morphology and Habitat Alterations on the Functional Diversity and Composition of Macrophyte Communities in the Large River

Macrophyte communities have major role in the functioning of freshwater ecosystems. However, there is gap in knowledge about how natural and anthropogenic hydro-morphological disturbances affect their functional diversity and trait structure, particularly in the temperate large rivers. In this study we investigated the effect of hydro-morphology on functional diversity and trait structure of macrophyte communities in the middle section of the Danube course. We collected macrophyte and environmental data from 947 sampling units in the main river channel and connected side waterbodies. We extracted data on 18 traits with 65 trait states and calculated seven functional diversity metrics and cumulative weighted means of trait states (CWMs). We applied redundancy analysis (RDA) to investigate the response of functional diversity metrics to the environmental variables, and Variation Partitioning to determine whether natural, or anthropogenic subset of hydro-morphological factors is more important predictor of functional diversity. To relate CWMs and environmental variables, we performed RLQ and fourth-corner analysis, followed by false discovery rate procedure. Hydro-morphological variables explained 36.7% of the variability in the functional diversity metrics. Combined effect of two subsets of environmental variables explained largest part of the variability in functional diversity metrics. Six associations between traits and environmental variables were found. We found that functional diversity metrics indicate prevailing ecological processes, from environmental to biotic filtering, along the natural—anthropogenic hydro-morphological gradient. We concluded that functional diversity metrics are potentially useful tools in the identification of the causes of ecological degradation, and could be applied in river bioassessments and management.

Herbivory increases on freshwater plants exposed to artificial light at night

Artificial light at night (ALAN) is recognized as one of the major anthropogenic pollutants jeopardizing biodiversity at a global scale. Few studies have focused on the impacts of nocturnal light on freshwater ecosystems despite their increasing exposure to light pollution worldwide due to human activities along rivers or lakes. By modifying metabolism, the disruption of natural light regime could modify the leaf palatability and affect the plant-herbivore interactions which can partly determine the structure of macrophyte communities. By experimentally mimicking light conditions from sub-urban areas, we measured the effects of low-level light at night on the leaf traits of an aquatic plant, Ceratophyllum demersum, and herbivory by the snail Lymnaea stagnalis, a generalist feeder. We demonstrate that artificial light at night increases the herbivory rate: leaves of C. demersum that had been exposed to ALAN for three months were 1.6 times more consumed by L. stagnalis than control leaves. The increase in C. demersum palatability to the pond snail when plants were exposed to ALAN was not due to a decrease in dry matter content or to a modification of the biomechanical characteristics of the leaves. Because snails have not been exposed to nocturnal light before or during the herbivory experiment, this increase in leaf palatability, is possibly linked to modifications of primary and/or secondary metabolism. Our results suggest that ALAN is a potential key factor affecting ecological processes in aquatic ecosystems such as trophic networks.

Linking macrophyte community structure with food chain length: A case study in the largest freshwater lake in China and ecological restoration implications

Food chain length is a significant ecosystem index and it greatly affects ecosystem processes and their outcomes. In recent decades, determinants or indicators of FCL have been investigated in different ecological contexts, but few studies analyzed the relationships between macrophyte community structure and the food chain length of freshwater ecosystems despite the crucial role of macrophyte community in determining food web structure. This study investigated the influence of macrophyte community structure on food chain length by conducting a field survey in Lake Poyang, the largest freshwater lake in China. Plant volume inhabited (PVI), Shannon-Wiener diversity index and Pielou’s evenness index were used to indicate macrophyte community structure. Our results suggested that intermediate levels of PVI and diversity (PVI 44% and diversity 0.61) with greater evenness could support longer food chain in sub-lakes of Lake Poyang. We proposed that macrophyte community structure indexes could be useful indicators in indicating food chain length in freshwater ecosystem. These novel findings also highlight that within suitable ranges of PVI and diversity, better restoration effect could be achieved by higher macrophyte evenness in lake management. Our findings provide new insights for the restoration and management of macrophytes in freshwater ecosystems.

Macrophytes restoration and its effects on eutrophication control in rehabilitated lakeshore zone of Gonghu Bay, Lake Taihu

以太湖贡湖湾人工湖滨带为对象，研究湖滨水生植物修复过程及其富营养化控制效果.人工湖滨区域内的消浪带、岸上护坡措施为水生植物修复提供了良好的生境条件，形成了包括荇菜（Nymphoides peltatum（Gmel.）Kuntze）、睡莲（Nymphaea tetragona Georgi）、菱（Trapa bispinosa Roxb.）为主的浮叶植物群落，以及以黑藻（Hydrilla verticillata（Linn.f.）Royle）、狐尾藻（Myriophyllum verticillatum L.）、小眼子菜（Potamogeton pusillus L.）、竹叶眼子菜（Potamogeton malaianus）为主的沉水植物群落.通过设置研究区、对照区，持续监测溶解氧、总氮、总磷、氨氮、叶绿素a浓度等水体指标，烧失量、氮含量、磷含量等沉积物指标，水生植物生物量、覆盖度，浮游藻类等指标.不同时期、不同区域间的时空分布显示：随着水生植物的恢复，水体营养状态指数（TLI）、沉积物生物生产力指数（BPI）显著下降，水体透明度显著提升；较高浓度的总氮（>3.0 mg/L）、氨氮（>0.6 mg/L）环境不利于浮叶植物的生长，沉水植物对其则表现出更好的适应性，同时水生植物在成长过程中直接从水体/沉积物中吸收氮；颤藻（Cyanophyta oscillatoria）、直裂藻（Cyanophyta merismopedia）等浮游藻类吸收了水体磷，水生植物利用了沉积物磷，共同缓解了磷在湖滨区域的累计.总结以上，湖滨带的水文水质条件可以影响水生植物群落结构，进而决定氮、磷的控制效果，所以在湖滨带修复中构建合适的生境条件是水生植物发挥氮磷控制效果的重要前提.水生植物在恢复过程中对浮游藻类群落结构的影响是显著的，并且以此影响到湖滨水体中磷的分布.;A rehabilitated lakeshore zone in Gonghu Bay, Lake Taihu, China was chosen to study macrophytes restoration and its effects on eutrophication control. The facilities including wave-weakening belts and bank revetment in rehabilitated lakeshore provided habitat for floating-leaved macrophytes, like Nymphoides peltatum (Gmel.) Kuntze, Nymphaea tetragona Georgi, Trapa bispinosa Roxb., etc. and submerged macrophytes, like Hydrilla verticillate, Myriophyllum verticillatum L., Potamogeton pusillus L., Potamogeton malaianus, etc.. The continuously monitoring on dissolved oxygen, total nitrogen, total phosphorus, ammonia, chlorophyll-a concentrations of water, ignition loss, nitrogen, phosphorus contents of sediment, macrophytes' coverages and biomass, phytoplankton's density were performed between two study areas and reference area. The space-time distribution of different areas and stages indicated that the trophic level index (TLI) of water and the bioproduction index (BPI) of sediment were remarkedly reduced, the water transparency was significantly increased as the macrophytes restored. The relatively high levels of total nitrogen (>3.0 mg/L) and ammonia (>0.6 mg/L) were the condition unfavorable for the floating-leaved macrophytes but not for the submerged macrophytes, in the meanwhile nitrogen of water and sediment were utilized directly during the macrophytes' restoration. Phytoplankton like Cyanophyta oscillatoria, Cyanophyta merismopedia and etc. absorbing phosphorus from water directly and macrophytes utilizing phosphorus in sediment collaboratively alleviated the phosphorus accumulation in lakeshore. Overall, it is concluded that the hydrological condition and water quality have impact on structure of macrophyte communities in the restoration, thus affecting the efficiency of nitrogen and phosphorus control. The macrophytes restoration had significant influences on planktonic communities, of which were directly correlated with phosphorus distribution in lakeshore water.

Preference, performance, and impact of the water‐lily aphid on multiple species of duckweed

The role of herbivores in driving the structure of freshwater macrophyte communities remains poorly understood in comparison with terrestrial ecosystems. For instance, although duckweed (subfamily Lemnoideae) are globally distributed, can be locally highly abundant and ecologically dominant, and are of growing economic importance, their interactions with herbivores remain understudied. To address how herbivores may impact duckweed species composition, we here experimentally quantify the preference and performance of a common duckweed herbivore, the water‐lily aphid (Rhopalosiphum nymphaeae) on four widespread duckweed species. Our two‐way choice experiments reveal that aphids display a preference for Spirodela polyrhiza &gt; Landoltia punctata = Lemna minor &gt; &gt; Wolffia brasiliensis. These results are rarely influenced by natal host species. By evaluating the growth of aphid populations on each duckweed species, we find that preference may be adaptive in certain ecological conditions. Quantifying the population growth rate of duckweed growing in the presence and absence of aphids revealed differential tolerance of herbivory across duckweed species. This study shows that aphids, through preferential feeding and significant differential effects on duckweed growth, can have a significant impact on duckweed population dynamics and potentially community composition.

Environmental heterogeneity drives macrophyte beta diversity patterns in permanent and temporary ponds in an agricultural landscape

Understanding patterns of beta diversity (heterogeneity) and its components (substitution and subset) is important for managing freshwater ecosystems and the research on these topics has increased over the last decade. However, there has been limited empirical research exploring the drivers of these components of beta diversity in ponds from agricultural landscapes, in which hydroperiod length is often a key structural driver. The purpose of our work was to examine the contribution of substitution (species replacement among sites without changes in richness) and subset (species differences among sites when species-poor sites constitute subsets of those with a greater number of taxa) structuring processes on macrophyte beta diversity patterns of sixteen permanent and ten temporary Mediterranean ponds. We also aimed to test the structuring role of local environmental factors and geographic isolation and to determine whether there are differences in the community heterogeneity and the relative importance of the substitution and subset fractions of beta diversity between permanent and temporary ponds. We found that temporary ponds were environmentally and biologically less heterogeneous and supported lower richness than permanent waterbodies. In both pond types, beta diversity almost entirely reflected patterns of species substitution rather than subsets. Local environmental conditions, and not among-pond distance, were the main drivers of macrophyte community structure. Overall, our results suggest that local environmental variables operating through niche processes were the primary mechanisms driving macrophyte beta diversity patterns, thus highlighting the importance of environmental heterogeneity for maintaining pond community diversity in agricultural landscapes. Accordingly, conservation initiatives and ecosystem management strategies should include permanent and temporary pond clusters comprising wide environmental gradients in their efforts to ensure high levels of regional biodiversity.

A small omnivore fish (Acheilognathus macropterus) reduces both growth and biomass of submerged macrophytes: implications for shallow lake restoration

Transplantation of submerged macrophytes has been widely used to improve water quality in restoring shallow lakes in China. However, in some lakes, small omnivorous fish predominated the fish assemblages and fed mainly on submerged macrophytes. Despite significant research examining grazing selectivity in herbivorous fishes, macrophyte feeding preferences of small omnivorous fishes are poorly understood. We conducted a mesocosm experiment to examine the effects of a prolific small omnivorous bitterling fish Acheilognathus macropterus on the relative growth rate (RGR) and biomass of submerged macrophytes (Ceratophyllum demersum, Myriophyllum spicatum, Vallisneria denseserrulata, and Hydrilla verticillata). Our results showed that the presence of A. macropterus significantly increased nutrient concentrations (e.g. total nitrogen and total phosphorus). The RGR of C. demersum in the bitterling-present treatment was significantly lower than the controls, in the presence of other macrophyte species. Further, total biomass of the four species of macrophytes in the fish-present mesocosms was markedly lower than in the fish-absent treatment, suggesting considerable consumption of macrophytes by bitterling. Moreover, the percent biomass of V. denserrulata and H. verticillata were significantly enhanced by the presence of bitterling. Our findings suggest that A. macropterus may increase nutrient concentrations through excretion and reduce the biomass and RGR of certain submerged macrophytes which may shift macrophyte community structure via selective grazing.

Assessing water quality in the Ceyhan River basin (Turkey) with the use of aquatic macrophytes

ABSTRACTAs a major biotic component of many lotic ecosystems, macrophytes consist a major component of running waters are often used as indicators within the European Water Framework Directive (WFD) to establish ecological quality. In this study, we investigated macrophyte community structure (e.g. composition, abundance and diversity) in Ceyhan River Basin located in the Southeastern Anatolian Region in Turkey. Data was collected during 2014–2015 from river sites located throughout the basin to evaluate the relationship between aquatic vegetation and river physico-chemical factors. The ecological status of the river basin was also calculated based on Macrophyte Biological Index for River (IBMR). In total, 33 macrophyta taxa were observed. According to their biological classification (life form), filamentous algae (FA), free floating (FF), floating leaved (FL) and submersed (S) macrophytes reached their maximum abundance value in summer, while emergent (E) macrophytes were at their maximum abundance in both summer and autumn. The ecological status of the Ceyhan River basin ranged from moderate to bad. The values found are reasonably comparable to IBMR scores recorded in rivers of other Mediterranean countries. IBMR index may be suitable to some extent to establish a basis for ecological quality assessment in Turkish River systems.

The role of monitoring, documentary and archival records for coastal shallow lake management

The effective management and restoration of aquatic ecosystems rely on the establishment of “reference conditions,” defined as the conditions expected in the absence of anthropogenic impacts, and require a thorough understanding of the natural variability within a system. However, at least in Europe, most systematic surveys post‐date the onset of human‐induced pressures on aquatic ecosystems, and thus fail to capture earlier degradation to water chemistry and flora and fauna, which were already advanced. Paleolimnological methods can be used to assess a range of anthropogenic stressors, but variability within a system is often smoothed to give long‐term patterns. Here, we compile monitoring, documentary, and archival records from a range of sources to extend our understanding of centennial‐scale lake ecosystem change and recovery from increasing salinity. We use a case study of the Thurne Broads shallow lake coastal wetland system (Broads National Park, UK), which has been subjected to multiple pressures of anthropogenic land drainage and North Sea storm surges (primarily in 1938 and 1953 CE) that have influenced salinity. Although there are still periods with significant data gaps and the interactions with eutrophication remain unclear, we demonstrate that historical data sources can be used in combination to observe seasonal patterns and extend knowledge on past salinity change and macrophyte community structure back to the 1800s. A demonstrable change in the ecosystem is observed after the sea flood of 1938 CE, when salinity levels in parts of the Thurne Broads were close, or equivalent, to seawater. With the added anthropogenic pressures of the late 1900s, the system has failed to fully recover. Future management, whilst balancing the needs of multiple users, should focus on the current large seasonal fluctuations in salinity and the vulnerability of the system to future large salinity increases.