Macrophyte Species Composition Research Articles

Ecological Condition of the Sapalayivka River in the Conditions of Lutsk Urbosystem

Purpose. Determination of the main factors of anthropogenic impact of the urban system of the city of Lutsk on the river basin of the river Sapalaivka and assessment of the ecological condition of the river on the basis of MIR "Macrophytic index of rivers". Methods. Comparative-geographical, generalization, systematization, statistical, comparative-analytical, descriptive, cartographic. Results. In the Sapalaivka River, 21 indicator species of macrophytes were found in the surveyed test areas, among which - 8 plants belong to dicotyledons, and 13 plants belong to monocotyledons, using which the MIR values ​​were calculated. Depletion of macrophyte species composition from 15-16 in test plots 1 and 2 to 2 species in test plot 3 indicates deterioration of the ecological condition of the river and the emergence of unfavorable conditions for macrophyte habitats. On the territory of the city, the section of the Sapalaivka riverbed, from the beginning of Potapova Street to the mouth, is mostly canalized, the species composition of macrophytes is depleted here and there is a specific smell of sewage. The part of the river that flows in the city (before Potapova Street), which was renaturalized in 2012-2016, has a richer species composition of macrophytes. Outside the city, the Sarpalaivka river basin is in good condition, as evidenced by the species composition of flora and fauna, as well as the intensive development of higher aquatic vegetation. Conclusion. As a result of the calculated ecological index of macrophytes MIR it is established that the water quality in the river Sapalaivka on the test site № 1, belongs to the II class, category - good and by trophic status is mesotrophic; on the test site № 2, belongs to the III class, category - satisfactory and eutrophic in trophic status; on the test site № 3, belongs to class IV, category - poor and trophic status is polytrophic. It is advisable to carry out further environmental measures, especially in the lower reaches of the river, in order to eliminate sources of water pollution, and to monitor the ecological status of the reservoir in order to restore the species composition of macrophytes and the ability to self-clean.

Biotesting and phytoindication of aquatic environment quality of urbanized territories

Currently, there is a necessity for regular quality control over natural water bodies within the territory of industrial cities. The aquatic environment quality monitoring and the toxicity assessment of the water pollutants, in addition to the hydrochemical analysis data, require integral, biological indicators. In recent times, methods of direct aquatic toxicity assessment, namely biotesting water quality using sensitive hydrobionts and phytoindication with macrophytes, have become increasingly important. In this regard, we have conducted a comparative quality assessment of the water from three different areas of the Saksagan river, influenced by the Ternovska mine in Kryvyi Rih using various test objects. Hydrobiological samples were collected in September 2019 above wastewater outfall (residual rainfall and snowmelt runoff), at wastewater outfall (residual rainfall and snowmelt runoff) and below rwastewater outfall (residual rainfall and snowmelt runoff). In water the basic hydrochemical indicators have been defined: hydrogen index (pH), dissolved gases, biogenic elements, hardness, temperature, electrical conductivity, total mineralization (salinity). The quality of the aquatic environment was assessed by biotesting with daphnid Daphnia magna Straus and phytoindication by modified Mayer`s index. The analysis of the hydrochemical regime has been carried out according to generally accepted methods. Biotesting of water samples was carried out according to CTDC 211.1.4.054-97. In the experiments daphnid Daphnia magna Straus were used as test organisms. For testing the samples toxicity Daphnia youth under the age of 24 hours has been used. The toxicity criterion was the mortality of test organisms in relation to control. The number of dead animals was calculated after 96 hours, then the mortality (or survival) of objects in the samples was calculated. The survey of vegetation has been carried out visually. A rake and a d-shaped net have been used to study the submerged species. The detected algae have been systematized into 3 groups according to the modified Mayer`s index. The average index for the entire monitoring area has reached 15 points, which corresponds to the third quality class (moderately polluted river, β-mesosaprobic zone). It has been revealed that the hydrochemical composition of the water of the Saksagan river is characterized by a sufficiently high mineralization (2.6–3.5 g / l), which is caused by the complex influence of several factors: physiographic conditions, river control (the influence of Makartivske, Krasovske, Saksaganske reservoirs). A naturally simplified structure of the species composition of macrophytes has been noted, which is typical for reservoirs under anthropogenic load. Endangered and listed in the Red book of Ukraine plant species in the study area were absent. The comparison of the results of bioindication methods with hydrochemical analysis has shown that phytoindication by the modified Mayer`s index was more sensitive method with respect to biotesting on daphnid Daphnia magna. However, we consider it impossible to compare these test objects, since each object may have a specific reaction to individual toxicants (Daphnia – to insecticides, macrophytes – to herbicides). Thus, in the future, it is recommended to use a set of methods for rapid assessment of the water quality in urban areas.

Impact of herbivory and competition on lake ecosystem structure: underwater experimental manipulation

Two basic ecological relationships, herbivory and competition, distinctively influence terrestrial ecosystem characteristics, such as plant cover, species richness and species composition. We conducted a cage experiment under natural conditions in an aquatic ecosystem to test the impacts of two treatments combined in a factorial manner: (i) a pulse treatment – removal of dominant competitors among primary producers (macroalgae Chara sp. and Vaucheria sp.), and (ii) a press treatment – preventing herbivore (fish, crayfish) access to caged plots. The plots were sampled once before the treatments were established and four more times within two years. Both treatments had a significantly positive impact on macrophyte cover and species richness and changed the macrophyte species composition. The effect of the macroalgae removal was immediate with the highest species richness occurrence during the first post-treatment monitoring, but the positive effect vanished with time. In contrast, preventing herbivore access had a gradual but long-lasting effect and reached a more steady-state over time. Two of the most common species showed contrasting responses, the palatable Potamogeton pectinatus was most supported by caging, while the distasteful Myriophyllum spicatum preferred open plots. Our findings may be applicable during the revitalisation of aquatic ecosystems that aims to increase macrophyte biodiversity.

Landscape- and Local-Scale Actions Are Essential to Conserve Regional Macrophyte Biodiversity.

Regional-scale pond diversity is supported by high variation in community composition. To effectively and efficiently conserve pond regional diversity, it is essential to recognize the community types in a focal region and the scales of the factors influencing the occurrence of respective community types. Based on a flora survey and GIS analysis of 367 ponds in western Japan, we developed a multinomial regression model that describes the relationship between aquatic macrophyte community type (based on cluster analysis) and five environmental factors that differ in the spatial scale at which they operate (i.e., landscape or local scale) and origin (i.e., natural or anthropogenic). A change in topographic configuration resulted in a transition of the community types with high species richness. Increasing urban and agricultural area around ponds resulted in a decrease in species-rich community occurrence; an increase in urban area increased the probability of a pond having no macrophytes, whereas that of paddy field increased the probability of a pond having only a few macrophytes. Pond surface area and proportion of artificial embankment significantly defined the pond community: greater embankment proportions increased the probability of ponds having few or no macrophytes. Our results suggest that conserving regional pond biodiversity will require actions not only at a local scale but also at a sufficiently large spatial scale to cover the full gradient of topographic configurations that influence the macrophyte species composition in ponds.

Response of Submerged Macrophyte Communities to External and Internal Restoration Measures in North Temperate Shallow Lakes.

Submerged macrophytes play a key role in north temperate shallow lakes by stabilizing clear-water conditions. Eutrophication has resulted in macrophyte loss and shifts to turbid conditions in many lakes. Considerable efforts have been devoted to shallow lake restoration in many countries, but long-term success depends on a stable recovery of submerged macrophytes. However, recovery patterns vary widely and remain to be fully understood. We hypothesize that reduced external nutrient loading leads to an intermediate recovery state with clear spring and turbid summer conditions similar to the pattern described for eutrophication. In contrast, lake internal restoration measures can result in transient clear-water conditions both in spring and summer and reversals to turbid conditions. Furthermore, we hypothesize that these contrasting restoration measures result in different macrophyte species composition, with added implications for seasonal dynamics due to differences in plant traits. To test these hypotheses, we analyzed data on water quality and submerged macrophytes from 49 north temperate shallow lakes that were in a turbid state and subjected to restoration measures. To study the dynamics of macrophytes during nutrient load reduction, we adapted the ecosystem model PCLake. Our survey and model simulations revealed the existence of an intermediate recovery state upon reduced external nutrient loading, characterized by spring clear-water phases and turbid summers, whereas internal lake restoration measures often resulted in clear-water conditions in spring and summer with returns to turbid conditions after some years. External and internal lake restoration measures resulted in different macrophyte communities. The intermediate recovery state following reduced nutrient loading is characterized by a few macrophyte species (mainly pondweeds) that can resist wave action allowing survival in shallow areas, germinate early in spring, have energy-rich vegetative propagules facilitating rapid initial growth and that can complete their life cycle by early summer. Later in the growing season these plants are, according to our simulations, outcompeted by periphyton, leading to late-summer phytoplankton blooms. Internal lake restoration measures often coincide with a rapid but transient colonization by hornworts, waterweeds or charophytes. Stable clear-water conditions and a diverse macrophyte flora only occurred decades after external nutrient load reduction or when measures were combined.

Ecological assessment of the macrophytes and phytoplankton in El-Rayah Al-Behery, River Nile, Egypt

The present study aimed to assess the effect of ecological factors on distribution and species composition of macrophytes and phytoplankton communities at El-Rayah Al-Behery. Changes in the quantitative and qualitative composition of the macrophytes and phytoplankton communities were detected in relation to season and sampling site. A total of eleven macrophytes and 100 phytoplankton species were identified. Among the macrophytes, the emergent species Echinochloa stagnina was the most dominant and widely distributed. Phytoplankton community is fairly diverse, related to 7 classes, which contains 3 main classes: Bacillariophyceae (28 taxa), Chlorophyceae (33 taxa) and Cyanophyceae (23 taxa). According to statistical analysis, occurrence of most macrophytes species were reversely affected by DO, COD, BOD and PO4; and closely correlated with NO2, NO3, Temp. and pH values. However, nitrogen and phosphorus are considered as limiting factors for bacillariohyceae growth (r=0.7). Both temperature and pH have a positive effect on the growth of chlorophyceae (r=0.9 and 0.8, respectively); while dissolved oxygen is an important parameter that affects on the growth of cyanphyceae (r=0.8). In addition, existence of Myriophyllium spicatum was associated with increasing of bacillariohyceae and total phytoplankton density (r=0.7). However, the presence of Polygonum tomentosum was intensely related with chlorophyceae (r=0.9) and Potamogeton nodosus and Polygonum tomentosum were positively correlated with cyanphyceae. In conclusion, the investigated area was characterized by different taxonomic composition of macrophytes and phytoplankton communities, which varied asa result of changing in water physiochemical characteristics as well as the interaction between different species.

Seasonal Variation in Spectral Response of Submerged Aquatic Macrophytes: A Case Study at Lake Starnberg (Germany)

Submerged macrophytes are important structural components of freshwater ecosystems that are widely used as long-term bioindicators for the trophic state of freshwater lakes. Climate change and related rising water temperatures are suspected to affect macrophyte growth and species composition as well as the length of the growing season. Alternative to the traditional ground-based monitoring methods, remote sensing is expected to provide fast and effective tools to map submerged macrophytes at short intervals and over large areas. This study analyses interrelations between spectral signature, plant phenology and the length of growing season as influenced by the variable water temperature. During the growing seasons of 2011 and 2015, remote sensing reflectance spectra of macrophytes and sediment were collected systematically in-situ with hyperspectral underwater spectroradiometer at Lake Starnberg, Germany. The established spectral libraries were used to develop reflectance models. The combination of spectral information and phenologic characteristics allows the development of a phenologic fingerprint for each macrophyte species. By inversion, the reflectance models deliver day and daytime specific spectral signatures of the macrophyte populations. The subsequent classification processing chain allowed distinguishing species-specific macrophyte growth at different phenologic stages. The analysis of spectral signatures within the phenologic development indicates that the invasive species Elodea nuttallii is less affected by water temperature oscillations than the native species Chara spp. and Potamogeton perfoliatus.

Macrophyte species composition and structure along littoral region in relation to limnological variables of a tropical wetland ecosystem

ABSTRACTThe composition and structure of macrophyte communities of the littoral region of Bhindawas wetland (India) was investigated. Two hypotheses were tested: (1) if limnological variables such as water chemistry and soil parameters are important determinants of species composition and abundance and (2) what is the variance in species richness and composition within the wetland. Twenty-eight macrophyte species belonging to 17 different families were identified with relatively low species diversity and richness (H′ = 2.09; Margalef index = 1.12). Eichhornia crassipes, attained the highest relative frequency (22.69%), followed by Salvinia natans, Paspalum paspaloides, Phragmites karka, Cynodon dactylon and Cyperus alopecuroides. The first and second axis of CCA ordination explained 38.4% and 28.5% of the total variance of species–limnological variables relationship, respectively. Water-related variables (dissolved oxygen, pH and nitrate concentration) and soil nutrient factors (soil carbon and phosphorus levels) were significantly correlated to macrophyte distribution. Sampling sites formed two distinct groups based on cluster analysis, indicating varying ecological conditions. Generally, composition and abundance of macrophytes evince highly productive nature of the lake, while dominance of invasive species like E. crassipes and S. natans indicates high influence of increased nutrient levels and anthropogenic activities in the catchment on lake macrophyte composition.

Water parameters and species composition of macrophytes in reclamation lakes in the area of a former sulphur borehole mine (SE Poland)

Macrophytes and selected physical-chemical water properties were studied in 17 post-mining lakes of Jeziórko Sulphur Mine – one of the largest borehole sulphur mines in the world. Artificial lakes were constructed in subsidence depressions during the reclamation process of mining fields. They were characterized by high mineralization – conductivity ranged from 723 to 2295 μS/cm. The reaction was near neutral, or more frequently, slightly alkaline. Concentrations of phosphorus and organic matter were low. In the group of hydrophytes, Ceratophyllum demersum, Myriophyllum spicatum, Najas marina, Utricularia vulgaris, Eleocharis acicularis, Potamogeton pectinatus, Potamogeton natans and Potamogeton pusillus were frequently dominant. In several lakes, large macroscopic algae dominated – charophytes forming large, dense Chara meadows. In marsh communities, Phragmites australis was the most expansive. Reclamation process had a positive effect on diversity, some of the species found in the study area are regionally rare, including one species which is threatened in Poland (Najas minor). No alien species were recorded.

Water Level Rise Induced Limnological Changes Indirectly Influencing the Structure of Aquatic Macrophyte Communities in a Tropical Reservoir

This study aimed to evaluate the degree of contribution of limnological variables to explaining ecological processes involving aquatic macrophytes after an event of water level rise (WLR) of an artificial lake (Cursai Reservoir - CR), located in northeastern Brazil. Initially we tested the hypotheses that limnological characteristics, and species richness and composition of aquatic macrophytes, would change post-WLR. Once these hypotheses were confirmed, we evaluated the degree of influence (direct or indirect) of the variables to structuring the community of aquatic macrophytes in CR. We carried out four pre-WLR sampling expeditions and four post-WLR sampling expeditions to a permanent plot of 5 m x 40 m, wherein we assessed species richness, composition and cover, and measured 12 limnological variables. We used partial correlation analysis to evaluate the degree of contribution of the limnological changes to post-WLR structuring of the aquatic macrophyte community. The results pointed to an indirect correlation between the limnological changes and the structuring of the aquatic macrophyte community derived from the WLR, with interespecific interactions being the determining factors in structuring. The cover and species composition in the post-WLR period confirmed this inference. In this period, we found a reduction in cover of the weeds Eichhornia crassipes, Paspalidium geminatum and Salvinia auriculata, new records of Egeria densa, Ludwigia leptocarpa and Ludwigia helminthorriza, and an increase in cover of Cyperus odoratus and Oxycaryum cubense. We consider that fast WLRs in artificial lakes, such as occurred in CR, can be considered intermediate disturbances. In such cases, the ecological processes involving the aquatic macrophytes could be explained by the intermediate disturbance hypothesis (IDH), which reinforces interespecific interactions (moreover competition) as being the restructuring factor.

The relationship between macrophyte assemblages and environmental variables in drainage and irrigation canals in Slovakia

AbstractOur study provides new knowledge about macrophyte assemblages and environmental variables of Slovak drainage and irrigation canals. The canal system, comprising ca. 15% of all flows in Slovakia, is one of the oldest in Central Europe. This information represents a first step toward exploitation of macrophytes as an obligatory biological quality element for the assessment of ecological potential according to the requirements of the Water Framework Directive. Among 61 canals studied, a total of 85 aquatic plant species (35 hydrophytes, 16 amphiphytes and 34 helophytes) were recorded during the years 2012–2014, including three neophytes and 18 threatened species. Physico-chemical variables explained the highest proportion of species variability, whilst hydromorphological variables and landscape variables were much less significant. Chemical oxygen demand, ammonium nitrogen, electrical conductivity, water pH, flow velocity and water depth were identified as most important drivers of species composition of aquatic macrophytes and explained 21.1% of the variability. The CCA results revealed differences in species composition of canals reflecting the geographical origin and environmental conditions as well, relating to South-Eastern and South-Western Slovakia. In conclusion, macrophytes in drainage and irrigation canals are able to reflect several environmental variables and might provide valuable information for bioindication in assessing the ecological potential.

Morphological and physiological traits of aquatic macrophytes respond to water chemistry in the Amazon Basin: an example of the genus Montrichardia Crueg (Araceae)

Species composition and occurrence of aquatic macrophytes in the Amazon Basin are associated with the hydrology and geomorphology of the catchment area. Nonetheless, the distribution of the Neotropical genus Montrichardia in the Amazon floodplains remains unclear. Three taxa of the genus were described: Montrichardia linifera (Arr.) Schott (ML), associated with nutrient-rich rivers; Montrichardia arborescens (L.) Schott (MA) and M. arborescens var. aculeata (G. Mey.) Engl., growing in nutrient-poor rivers. We hypothesize that different taxa can be discriminated according to variation in density, morphology, physiology, and biomass along environmental gradients of water characteristics and soil fertility. Samples of 55 populations of Montrichardia were taken in rivers with contrasting water types in the Amazon Basin along a gradient of declining soil fertility from Western to Eastern Amazonia spanning about 2,500 km. Local phenotypic variations and discriminant analysis separated ML and MA with MA as subset of MA. Water chemistry influenced the distribution of taxa. The nutritional soil gradient at the basin level clearly explained the distribution of ML, but not that of MA. The distribution pattern of ML was similar to that of tree species in the Amazon Basin, with higher density in West Amazon.

Species composition and morpho-ecological groups of aquatic macrophytes in foothill lakes on the eastern slope of the Southern Urals (Chelyabinsk region, Russia)

The aquatic macrophyte richness in nine lakes situated in the Chelyabinsk region (Russia) was analyzed. These lakes represent the foothill group, located on the eastern slope of the Southern Urals range. A total of 89 species belonging to 49 genera and 35 families were recorded. The species list includes 40 submerged rooted hydrophytes, 23 hygro-helophytes, 13 helophytes, 6 rooted hydrophytes with floating leaves, 4 free submerged hydrophytes and 3 free floating hydrophytes.

Macrophyte species richness and composition are correlated with canopy openness and water depth in tropical floodplain lakes

Aquatic macrophytes colonize a variety of environments, and they play important roles in ecosystem function and in community structure. One key challenge for aquatic ecologists is to investigate the environmental factors that drive the richness and distribution of these plants. In this study, we assessed the importance of selected morphometric variables and of the canopy openness of the riparian vegetation to explain macrophyte species richness and composition. We sampled macrophytes along gradients of depth, littoral slope, distance from the connection with the river, and canopy openness in floodplain lakes connected with the Upper Parana River. We used quadrats to survey a total of 40 sites in 11 lakes. We recorded 31 macrophyte species and found that macrophyte richness was best and positively correlated with canopy openness. This correlation suggests that canopy openness plays an important role as an environmental filter, regulating the amount of light availability for macrophytes. Macrophyte species composition was best correlated with depth, indicating that zonation of macrophyte species also occurs in these shallow lakes. These findings emphasize the importance of morphometric variables and canopy openness for structuring macrophyte assemblages. In addition, our results suggest that canopy openness and depth may be considered in management strategies aiming to recover macrophyte diversity and the processes mediated by aquatic macrophytes in small and shallow floodplain lakes.

Responses of epiphytic aquatic macroinvertebrates to hypoxia

Different species of aquatic macrophytes have strongly contrasting effects on the oxygen dynamics of the waters they inhabit. We conducted laboratory experiments to test the hypothesis that macroinvertebrates inhabiting stands of the floating-leaved water-chestnut (Trapa natans), which causes severe hypoxia, are more resistant to low oxygen concentrations (0.5–1 mg L−1) than those that inhabit submerged aquatic vegetation (Vallisneria americana and Myriophyllum spicatum), which do not cause hypoxia. Chironomids and amphipods associated with T. natans were more resistant to hypoxia than those associated with submerged plants, in support of our hypothesis. Gastropods showed the opposite pattern. Survival was significantly related to exposure time as well in these 3 groups. Ostracods from the 2 habitats were equally resistant to hypoxia, with high survival regardless of exposure time. Almost all zygopterans died when exposed to hypoxia. Different kinds of macroinvertebrates have distinct responses to hypoxia, so different kinds of hypoxic macrophyte beds may support distinct assemblages of macroinvertebrates. Specifically, the spatial and temporal extent of hypoxia will be critical, and shifts in macrophyte species composition caused by species invasions or other reasons may have differential effects on macroinvertebrates by causing different oxygen regimes.

Explanatory variables associated with diversity and composition of aquatic macrophytes in a large subtropical river floodplain

The structure of aquatic macrophyte assemblages can be affected by myriad factors, including physical, chemical and morphometric characteristics. We describe the patterns of plant species diversity and composition and vegetation height in aquatic ecosystems and their potential determinants at a regional scale in the Middle Paraná River floodplain. Sampling was conducted in twenty-three water bodies, including secondary channels, connected lakes and disconnected lakes. We compared the macrophyte species richness, composition and vegetation height in water bodies with different degrees of connectivity with the river and assessed the most important abiotic explanatory variables (morphometric, physical and chemical) associated with these assemblage attributes. Species accumulation curves showed that species richness did not differ between water bodies with different degrees of connectivity, although it tended to be lowest in secondary channels. Species richness was specifically associated with depth, conductivity, percent of solar radiation reaching the bottom and nitrate. Macrophyte assemblage composition was related primarily to the degree of connectivity, as rare species mostly occurred in disconnected lakes. Composition was also related to the degree of wind exposure (fetch), distance to shoreline and depth. Finally, vegetation height (a surrogate for biomass) was associated with the ammonium and sediment organic matter. Thus, a combination of morphometric and abiotic factors explained species richness, while degree of connectivity and morphometry explained assemblage composition. Vegetation height was explained by nutrients. These results suggest that a single set of variables is not sufficient to explain different aspects of macrophyte assemblages.

Assessing the status of marl lakes under the European Union Water Framework Directive – insights from contemporary and palaeolimnological studies of three English lakes

Methods for ecological status assessment of high-alkalinity lakes under the Water Framework Directive (WFD) differ between continental Europe and the UK. In the UK, marl lakes, i.e. carbonate-precipitating lakes, are placed in a separate category in which metrics account for the naturally low phosphorus content and sensitive macrophyte communities found therein. If this separation is appropriate, the UK method, which applies a correction factor for stricter assessment of marl lakes, should assess ecological status more effectively. Using contemporary macrophyte and chlorophyll-a data, this supposition was assessed for three English lakes by calculating ecological status with and without the correction factor. The veracity of the results was assessed using palaeolimnological and historical surveys. Further, the potential of macrophyte maximum colonisation depth (Cmax) as an additional metric was investigated. For two lakes, the status suggested by historical-palaeolimnological data was poorer (Moder- ate) than that suggested by WFD classification, both with and without the correction factor (Good and/or High). This has important implications as restoration is required only for water bodies classed below Good. For the third lake, for which high chlorophyll-a resulted in Poor status in agreement with historical-palaeolimnological data, the discrepancy between the macrophyte metrics with and without the correction factor was considerable (Poor, Moderate, respectively). The results suggest that a separate marl lake category is warranted and may be advisable for other Member States in continental Europe. Importantly, status was higher than recommended for the two lakes close to the Good/Moderate boundary even with the correction factor. This leads us to recommend more studies be undertaken on eutrophication responses of marl lakes. In lakes where macrophyte species composition varies with water depth, eutrophication is apparent through reductions in Cmax especially of Characeae and Potamogetonaceae. Cmax is simple to measure and may much improve the reliability of marl lake assessment.

Factors affecting the distribution patterns of aquatic macrophytes

Abstract Aquatic macrophytes constitute important components of many freshwater ecosystems. The manifold role of aquatic macrophytes in freshwater habitats is closely linked to their distribution, which in turn depends on a myriad of factors. Foremost, among these are light, water temperature, water quality changes and nutrient enrichment, sediment composition and fluctuations in water levels. Light and temperature are of paramount importance in determining the distribution (with depth, season and latitude), thereby influencing productivity and species composition as well. Sediment compositions markedly affect the growth rates of macrophytes which in turn have a profound influence on the distribution of aquatic macrophytes. Water quality changes and nutrient enrichment can cause considerable variations in the species richness, composition, and density of aquatic vegetation. The reduction in water levels could bring drastic changes in the species composition and distribution of macrophytes. Factors associated with competition, herbivory, land use and land cover changes etc. also play an important role in shaping macrophyte distribution and community structure. In this review we examine both biotic and abiotic factors that influence the structural attributes like species composition, distribution, abundance and diversity of aquatic macrophytes.

5. Community of higher aquatic plants

The most recent data (obtained in July, 2011) regarding species composition and community structure of macrophytes from Lake Drūksiai after the shutdown of the INPP are presented. The characteristics of overgrowth and productivity of aquatic plants are given. The current flora composition is compared with the data of previous investigations. According to the data obtained on the development of macrophyte communities, the lake can be referred to as a mesotrophic water body, and after the shutdown of the NPP the macrophyte succession is at the initial stage.

Application of a three-tier framework to assess ecological condition of Gulf of Mexico coastal wetlands

A multi-level coastal wetland assessment strategy was applied to wetlands in the northern Gulf of Mexico (GOM) to evaluate the feasibility of this approach for a broad national scale wetland condition assessment (US Environmental Protection Agency's National Wetlands Condition Assessment). Landscape-scale assessment indicators (tier 1) were developed and applied at the sub-watershed (12-digit hydrologic unit code (HUC)) level within the GOM coastal wetland sample frame with scores calculated using land-use maps and geographic information system. Rapid assessment protocols (tier 2), using a combination of data analysis and field work, evaluated metrics associated with landscape context, hydrology, physical structure, and biological structure. Intensive site monitoring (tier 3) included measures of soil chemistry and composition, water column and pore-water chemistry, and dominant macrophyte community composition and tissue chemistry. Relationships within and among assessment levels were evaluated using multivariate analyses with few significant correlations found. More detailed measures of hydrology, soils, and macrophyte species composition from sites across a known condition gradient, in conjunction with validation of standardized rapid assessment method, may be necessary to fully characterize coastal wetlands across the region.