Abundance Of Aquatic Macrophytes Research Articles

Diversity, Abundance, and Seasonal Variation of Aquatic Macrophytes in Southeastern Bangladesh

The study was conducted to assess the diversity and abundance of aquatic macrophytes in the southeastern region of Bangladesh, encompassing the Noakhali, Cumilla, and Chandpur districts. The study was carried out over the period of July 2022 to June 2023. This research utilized a mixed-methods approach, incorporating observation of the study area, qualitative interviews, and quantitative surveys. Five types of aquatic macrophytes, 47 species from 18 orders and 25 families were identified. These are free-floating, rooted-floating, emergent, submerged, and marginal. Among the three locations, Noakhali was recorded as the highest with 44 species, followed by Cumilla with 43, and Chandpur with 35. In Noakhali, seasonal variation analysis showed that 39% of species were found in the rainy season, 14% in summer, 14% in winter, and 20% year-round. In Cumilla, 35% of aquatic macrophytes were available in the rainy season, and 14%, 12%, and 5% in winter, spring, and autumn, respectively. In Chandpur, 37% of aquatic macrophytes were prevalent in the rainy season, 26% were found year-round, 9% in winter, 14% in summer, and 6% each in spring and autumn. In Noakhali, 44% of macrophytes were frequent, 33% moderate, and 23% rare. In Cumilla, 49% were frequent, 44% moderate, and 14% rare. Chandpur reported 49% frequent, 31% moderate, and 20% rare species. The order Alismatales emerged as the dominant order comparatively across all locations. This research will provide insights into the biodiversity of aquatic macrophytes in this area, thus supporting effective management strategies.

Aquatic Floral Abundance on Ichthyofaunal Community in a Forested Stream of Pamba River in the Western Ghats

Aquatic macrophytes are essential to the fish community because they offer food, protection from predators and shelter. The present study deals with the influence of the distribution and abundance of aquatic macrophytes on stream fishes. Twenty-one species of aquatic plants and 13 associated fish species were identified during the study period of January-December 2019. In the study stream, the abundance of aquatic flora positively impacted the fish community. Certain aquatic macrophytes were highly preferred by individual fish species in the area. The Podostemonads formed a major plant group along the stream. Emergent plants, especially Lagenandra toxicaria played an important role in maintaining the composition of the fish community. Hypselobarbus kurali is a known genus of food fish, and they exhibited affinity to the area covered with Lagenandra toxicaria. Hydrilla verticillata, the submerzed plant showed extensive growth during monsoon and supported a large number of Haludaria fasciata.

Assessment of aquatic ecological health: A comparative study between cistern-made and ‘Natural’ earthen-made waterbody

Ecological health of two waterbodies i.e., cistern-made and ‘natural’ earthen-made waterbody was compared in the present study based on temporal variations of physicochemical and biological parameters. Number of physicochemical parameters [transparency, temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), total suspended solids (TSS), dissolved oxygen (DO), total hardness (TH), total alkalinity (TA), biochemical oxygen demands (BOD), nitrate, phosphate and chlorophyll a (Chl a)], and biological parameters, e.g., zooplankton community and aquatic macrophytes were studied seasonally. Zooplankton communitiy comprised six arthropods and two rotifers. SIMPER analysis depicted that Moina sp., Daphnia sp., and Cyclops sp. were dominant species in cistern pond while Cyclops sp., Daphnia sp., Keratella sp. and Brachionus sp. were dominant in earthen natural pond. Abundance of species was highest in summer followed by post-rainy and winter in both the ponds while maximum abundance of zooplankton was recorded in summer. Species richness peaked in winter in natural pond, while in cistern pond species richness and diversity raised in summer. Multivariate analyses depicted significant temporal variation in zooplankton species in both the conditions. RELATE analysis revealed that temporal variation in species distribution and zooplankton community was significantly correlated with environmental parameters. Moreover, biological-environmental best matching (BIO-ENV) analyses indicated that water temperature, pH, TH and BOD (for cistern pond) and water temperature, EC and TSS (for earthen natural pond) were the main driving forces for temporal variations in species distribution and zooplankton community. Additionally, correlation analysis depicted that Moina sp., Daphnia sp., Diaptomus sp., Cyclops sp., Cypris sp., Bosmina sp., and species abundance was positively (significant) correlated with transparency, water temperature, and Chl a in natural pond. On the other hand, correlation analysis depicted that zooplankton species, species abundance, evenness and diversity were positively correlated with water temperature, DO, BOD and Chl a in cistern pond. Moreover, abundance of aquatic macrophytes were limited in three basic groups, namely free floating [(Lemna sp. (Major), Lemna sp. (Minor), Azolla sp., Pistia sp. and Eichhornia sp.], rooted submerged [Hydrilla sp., Ceratophyllum sp.] and rooted emerged [Nymphaes sp. and Ipomoea sp.]. Further, trophic state index (TSI) value revealed that both the ponds are hyper-eutrophic (‘natural’ waterbody > cistern waterbody) with a strong temporal variations. Therefore, these data could be used as water quality community-based bio-assessment tool as well as basis of water quality management plans to monitor the pollution level or conservation of aquatic ecology.

Plant Macrofossils Reveal Aquatic Macrophyte Successions of a Typical Shallow Lake (Huanggai Lake, China) in the Past Century.

Aquatic macrophytes are one of the important biotic components of shallow lake ecosystems. Understanding the long-term evolution of the macrophyte community is crucial for lake management. Huanggai Lake, a typical shallow lake in the middle reach of the Yangtze River, was selected as the research site for this study. Based on 210Pb/137Cs dating, aquatic plant macrofossils were used to reconstruct the succession of aquatic macrophytes in the past century. Our results show that the lake maintained a consistent natural state before 1940, with a relatively low abundance of aquatic plants dominated by species such as Najas minor. From 1940 to 1974, human activities gradually intensified in the lake leading to the emergence of eutrophic species such as Potamogeton maackianus, along with the increasing abundance of other emergent and floating aquatic macrophytes. Since 1974, more pollution-resistant, emergent species such as Potamogeton maackianus and Potamogeton crispus have become dominant. The abundance of aquatic macrophytes reached its maximum in the early 1990s. Combined with macrofossil succession and other multiple sedimentary proxy analyses, driving mechanisms for aquatic macrophytes are discussed. Both the nearby Liangzi Lake and Huanggai Lake share many common features of aquatic plant evolution. This study is the first of its kind to use plant macrofossils (with identifiable images) as a proxy for aquatic macrophyte succession in a shallow Yangtze lake. In absence of long-term monitoring records, this study highlights the increased application of plant macrofossils for reconstructing the vegetation dynamics and restoration of degraded lakes exposed to severe anthropogenic impacts over the past century.

Spatio‐temporal, ontogenetic and sex‐related patterns in resource use of Amazonian manatees across floodplains and estuaries as inferred by δ13C and δ15N isotopic values

Abstract Threats to aquatic mammals may occur in isolation or in combination, leading to cumulative effects on populations and their ecosystems. Thus, conservation actions must consider the complexity of factors involved in patterns of habitat use, including feeding ecology, such as ontogenetic, spatial and temporal dietary shifts. The Amazonian manatee (Trichechus inunguis) occurs in a variety of environments, such as várzeas and igapós (flooded areas) and estuaries. Different environments can lead to variation in the diet of manatees according to the availability and abundance of plant species. Stable isotope analysis (δ13C and δ15N) of manatee teeth was performed to assess spatio‐temporal, ontogenetic and sex‐related patterns in resource use. Mixing models were applied to identify the most consumed plant groups. In várzeas, there were significant interactions between sex and ontogenetic class and ontogenetic class and time series for δ13C values. For manatees sampled from 1994 to 2004, males and adults showed the highest δ15N values, and aquatic C3, followed by C4 plants, were the groups that most contributed to the species’ diet. Comparisons among the environments showed the highest δ13C values for manatees from várzeas and the lowest values for manatees from igapós. Várzeas had the highest abundance of C4 plants (high δ13C values), whereas they are scarce in igapós, leading manatees to consume mainly C3 species. The isotopic values of manatees mirrored those of the most available food sources in each environment, supporting the generalist and opportunist behaviour described for the species. Therefore, threats to the diversity, distribution and abundance of aquatic macrophytes, such as contamination, cattle raising and changes in the hydrological cycle (as a consequence of dams and climate change), will affect the diet of the manatee and should be taken into account when designing conservation strategies for the species.

Aquatic Macrophyte Vegetation Promotes Taxonomic and Functional Diversity of Odonata Assemblages in Intermittent Karst Rivers in the Mediterranean

Assemblages of adult Odonata were studied in four intermittent karst rivers encompassing macrophyte-rich (MRH) and macrophyte-poor habitats (MPH) in southern Europe, where temporary lotic habitats are the predominant freshwater type but are still understudied. With a total of 25 recorded species, the studied habitats support species-rich Odonata assemblages, as already shown for intermittent rivers in the Mediterranean. Aquatic macrophyte abundance, conductivity, and water velocity are the most significant determinants of Odonata assemblages in the studied IRES. MRH promote higher Odonata abundance and the taxonomic and functional diversity of their assemblages compared to the MPH. Odonata assemblages in MRH are characterized by higher values of body size and a higher share of species preferring lentic and temporary hydrological conditions. Moreover, their assemblages are characterized by various patterns of nymphal development and drought resilience strategies. In contrast, MPH are preferred by lotic species, with nymphal development all year round and with no specific drought-resisting strategies. Our results contribute to the knowledge of diversity and ecological requirements of dragonflies and damselflies in IRES habitats, which could provide scientific background for future conservation activities and bioassessment protocols of such habitats and their biota.

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.

Comprehensive analyses of agrochemicals affecting aquatic ecosystems: A case study of Odonata communities and macrophytes in Saga Plain, northern Kyushu, Japan

The negative influence of agrochemicals (pesticides: insecticide, fungicide, and herbicide) on biodiversity is a major ecological concern. In recent decades, many insect species are reported to have rapidly declined worldwide, and pesticides, including neonicotinoids and fipronil, are suspected to be partially responsible. In Japan, application of systemic insecticides to nursery boxes in rice paddies is considered to have caused rapid declines in Sympetrum (Odonata: Libellulidae) and other dragonfly and damselfly populations since the 1990s. In addition to the direct lethal effects of pesticides, agrochemicals indirectly affect Odonata populations through reductions in macrophytes, which provide a habitat, and prey organisms. Due to technical restrictions, most previous studies first selected target chemicals and then analyzed their influence on focal organisms at various levels, from the laboratory to the field. However, in natural and agricultural environments, various chemicals co-occur and can act synergistically. Under such circumstances, targeted analyses might lead to spurious correlations between a target chemical and the abundance of organisms. To address such problems, in this study we adopted a novel technique, “Comprehensive Target Analysis with an Automated Identification and Quantification System (CTA-AIQS)” to detect wide range of agrochemicals in water environment. The relationships between a wide range of pesticides and lentic Odonata communities were surveyed in agricultural and non-agricultural areas in Saga Plain, Kyushu, Japan. We detected significant negative relationships between several insecticides, i.e., acephate, clothianidin, dinotefuran, flubendiamide, pymetrozine, and thiametoxam (marginal for benthic odonates) and the abundance of lentic Epiprocta and benthic Odonates. In contrast, the herbicides we detected were not significantly related to the abundance of aquatic macrophytes, suggesting a lower impact of herbicides on aquatic vegetation at the field level. These results highlight the need for further assessments of the influence of non-neonicotinoid insecticides on aquatic organisms.

The importance of aquatic macrophytes in a eutrophic tropical shallow lake

Inlay Lake is the second largest natural lake in Myanmar. Located in Shan State, in the eastern part of the country, it is a known biodiversity hotspot. The lake is negatively affected by an increasing local human population and rapid growth in both agriculture and tourism. In recent decades, several studies have listed faunistic and floristic groups in Inlay Lake, but there is still a general lack of knowledge about the aquatic macrophyte and phytoplankton community composition and abundance, and their interactions. To fill this knowledge gap, field surveys of biological and physical and chemical parameters were carried out in the period 2014–2017. They show that Inlay Lake is a shallow, clear water and calcareous lake, with nutrient concentrations indicating mesotrophic-eutrophic conditions. However, close to the shore, nutrient concentrations are generally higher, reflecting pollution from inflowing rivers, shoreline villages and floating gardens. Both the richness and abundance of aquatic macrophytes in Inlay Lake were high, with several species forming extensive stands in most of the lake over the whole survey period. Total phytoplankton and cyanobacterial biomass were low, but cyanobacteria included toxin-producing strains of Microcystis, suggesting that cyanobacterial and total phytoplankton biomass need to be kept low to avoid potentially harmful cyanobacterial blooms. Submerged macrophyte abundance and phytoplankton biomass were inversely correlated in the heavily vegetated northern lake area. Our survey suggests a great importance of the submerged macrophytes to the general water quality and the clear water state in Inlay Lake. Maintaining high macrophyte abundances should therefore be a goal in management strategies, both for Inlay Lake and other lakes in Myanmar. It is highly desirable to include macrophytes and phytoplankton in the lake monitoring in Myanmar.

Bulk and compound-specific \u03b413C and n-alkane indices in a palustrine intermontane record for assessing environmental changes over the past 320\xa0ka: the Padul Basin (Southwestern Mediterranean realm)

Here we provide valuable information about the palaeoenvironmental evolution of Southwestern Mediterranean region during the last ca. 320 ka through a biomarker-based study of the longest continuous continental Quaternary record in the Iberian Peninsula. The n-alkane content and δ13C values of these lipids were measured in 300 samples taken from the uppermost 55 m of the Padul Basin (PB) record. The δ13C signal of long-chain n-alkanes was a reliable proxy for C4/C3 terrestrial vegetation composition in the basin, as emergent macrophytes made a minor contribution to these homologues. In contrast, the δ13C values of C23 and C25 alkanes reflected mainly phases of increasing water level of the lacustrine/palustrine water body since aquatic macrophytes contain a large proportion of these compounds. Low δ13C values were attributed to a marked contribution of plants using the C3 photosynthetic pathway. Intervals with the lowest δ13C values were attributed to an important input of angiosperms, although they could also be explained by changing environmental conditions or environmental stress, as large shifts in δ13C occurred in long-chain homologues typically abundant in terrestrial plants. Shifts in δ13C of medium-chain homologues reflected limited CO2 availability induced by water temperature, salinity, pH, enhanced productivity, low atmospheric pCO2, or stagnant barriers, rather than the abundance of aquatic macrophytes. Our results also suggest enhanced isotopic fractionation during lipid synthesis by aquatic macrophytes within MIS 7 and the Holocene, leading to increased δ13C values of bulk OM and of long-chain n-alkanes. Hence, the δ13C logs were ideal for studying the contribution of aquatic macrophytes to the lipid and isotopic composition of sediments and for the reconstruction of palaeoenvironmental conditions. These results confirmed that C4 plants had a low presence in the PB. Comparison with biomarker analysis and pollen data of the PB and other records of the Southwestern Mediterranean revealed that δ13C values of bulk OM and of long-chain n-alkanes reflected global climatic oscillations during MIS 7 and the episodes Heinrich Events 3, 2, 1 and Younger Dryas.

Macrophytes as indicators of the ecological status of a tropical rehabilitated wetland ecosystem: Application of multivariate statistics and Ecological State Macrophyte Index (ESMI)

The present study used the Ecological State Macrophyte Index (ESMI) and the multivariate statistical methods to assess the ecological status and the variation of macrophytes in a tropical wetland system. Six sites were selected from rehabilitated and non-rehabilitated areas of an urban tropical wetland and the water quality parameters (water pH, temperature, conductivity, total dissolved solids (TDS), dissolved oxygen (DO), visibility, biological oxygen demand 5 days after incubation (BOD 5 ), chemical oxygen demand (COD), nitrate, chlorophyll-a and total phosphorus concentrations), sediment quality parameters (pH, organic matter content, percentage sand, silt and clay content) and abundance of aquatic macrophytes were measured. Shannon Weiner diversity index, percentage vegetation under anthropo-pressure, macrophyte settlement rate and ESMI were calculated. Significant variations in the water and sediment quality parameters were observed and ten species of aquatic macrophytes were recorded. Salvinia melosta and Cypreus iria were recorded only from the non-rehabilitated sites. Although there was no significant difference in the percentage anthropo-pressure among study sites, the rehabilitated sites were displayed low anthropo-pressure. The sites in the non-rehabilitated area showed a significantly lower macrophyte settlement rate. ESMI and macrophyte abundance showed significant correlations with water quality parameters. Based on the results, it can be recommended that applications based on ESMI and multivariate statistics can be used to assess the ecological status of tropical wetlands.

Negative correlations between native macrophyte diversity and water hyacinth abundance are stronger in its introduced than in its native range

AbstractAimWe tested the hypothesis that the diversity and abundance of aquatic macrophytes are negatively related with Eichhornia crassipes abundance in its introduced range, but not in its native range.LocationUpper Paraná River Floodplain, Brazil and Southeast China.MethodsWe sampled aquatic macrophytes patches in Brazil (native range) and China (introduced range) along a biomass gradient of E. crassipes. For each patch, we obtained values of species richness and aquatic macrophytes percentage cover, as response variables in regression models. We also used species accumulation curves to quantify the total plot diversity in dominated and non‐dominated plots for both countries. Finally, we compared the influence of E. crassipes dominance on community composition and beta diversity with Permanova and Permdisp, respectively.ResultsThe regression analyses revealed a negative correlation between macrophyte richness and cover and E. crassipes biomass only in the introduced range. The cumulative number of species decreased at a higher extent in plots dominated by E. crassipes in China, compared with Brazil. Also, species composition changed and beta diversity decreased in the dominated plots in China, but not in Brazil.Main ConclusionsThe reduction of all diversity attributes related to E. crassipes probably results from its engineer species role, which decreases littoral region habitat heterogeneity and affects rare species in the introduced range. Differences between countries may be associated with impacts of water hyacinth on native macrophytes as this plant grows very fast and is highly competitive. Although less probable, biotic resistance at the establishment phase of water hyacinth in sites with higher number of native species is also a possibility. Regardless of the main mechanism explaining our patterns, it is suggested that invasion by water hyacinth is a cause for concern for its higher impacts in the introduced ranges than the native ranges.

Relationship between epipelon, epiphyton and phytoplankton in two limnological phases in a shallow tropical reservoir with high Nymphaea coverage

Macrophytes and phytoplankton are recognized as having roles in determining alternative stable states in shallow lakes and reservoirs, while the role of periphyton has been poorly investigated. Temporal and spatial variation of phytoplankton, epipelon and epiphyton was examined in a shallow reservoir with high abundance of aquatic macrophytes. The relationships between algae communities and abiotic factors, macrophyte coverage and zooplankton density were also analyzed. Monthly sampling was performed in three zones of the depth gradient of the reservoir. Two phases of algal dominance were found: a phytoplankton phase and epipelon phase. The phase of phytoplankton dominance was characterized by high macrophyte coverage. Rotifera was the dominant zooplankton group in all the zones. Flagellate algae were dominant in phytoplankton, epipelon and epiphyton. Macrophyte coverage was found to be a predictor for algal biomass. Changes in biomass and species composition were associated with macrophyte cover variation, mainly the Nymphaea. In addition to the abiotic factors, the macrophyte coverage was a determining factor for changes to the algal community, contributing to the alternation between dominance phases of phytoplankton and epipelon. The macrophyte–phytoplankton–periphyton relationship needs to be further known in shallow reservoirs, especially the role of epipelon as an alternate stable state.

Effects of a herbicide on paddy predatory insects depend on their microhabitat use and an insecticide application.

Indirect effects of agrochemicals on organisms via biotic interactions are less studied than direct chemical toxicity despite their potential relevance in agricultural landscapes. In particular, the role of species traits in characterizing indirect effects of pesticides has been largely overlooked. Moreover, it is still unclear whether such indirect effects on organisms are prevalent even when the organisms are exposed to direct toxicity. We conducted a mesocosm experiment to examine indirect effects of a herbicide (pentoxazone) on aquatic predatory insects of rice paddies. Because the herbicide selectively controls photosynthetic organisms, we assumed that the effects of the herbicide on predatory insects would be indirect. We hypothesized that phytophilous predators such as some Odonata larvae, which cling to aquatic macrophytes, would be more subject to negative indirect effects of the herbicide through a decrease in abundance of aquatic macrophytes than benthic, nektonic, and neustonic predators. Also, we crossed-applied an insecticide (fipronil) with herbicide application to examine whether the indirect effects of the herbicide on the assembling predators act additively with direct adverse effects of the insecticide. The herbicide application did not decrease the abundance of phytoplankton constitutively, and there were no clear negative impacts of the herbicide on zooplankton and prey insects (detritivores and herbivores). However, the abundance of aquatic macrophytes was significantly decreased by the herbicide application. Although indirect effects of the herbicide were not so strong on most predators, their magnitude and sign differed markedly among predator species. In particular, the abundance of phytophilous predators was more likely to decrease than that of benthic, nektonic, and neustonic predators when the herbicide was applied. However, these indirect effects of the herbicide could not be detected when the insecticide was also applied, seemingly due to fipronil's high lethal toxicity. Our study highlights the importance of species traits such as microhabitat use, which characterize biotic interactions, for predicting indirect effects of agrochemicals. Given that indirect effects of the chemicals vary in response to species traits and direct toxicity of other chemicals, efforts to explain this variation are needed to predict the realistic risks of indirect effects of agrochemicals in nature.

Diatom-inferred aquatic impacts of the mid-Holocene eruption of Mount Mazama, Oregon, USA

AbstractHigh-resolution diatom stratigraphies from mid-Holocene sediments taken from fringe and central locations in Moss Lake, a small lake in the foothills of the Cascade Range, Washington, have been analyzed to investigate the impacts (and duration) of tephra deposition on the aquatic ecosystem. Up to 50 mm of tephra was deposited from the climactic eruption of Mount Mazama 7958–7795 cal yr BP, with coincident changes in the aquatic ecosystem. The diatom response from both cores indicates a change in habitat type following blanket tephra deposition, with a decline in tychoplanktonic Fragilaria brevistriata and Staurosira venter and epiphytic diatom taxa indicating a reduction in aquatic macrophyte abundance. Additionally, the central core shows an increase in tychoplanktonic Aulacoseira taxa, interpreted as a response to increased silica availability following tephra deposition. Partial redundancy analysis, however, provides only limited evidence of direct effects from the tephra deposition, and only from the central core, but significant effects from underlying environmental changes associated with climatic and lake development processes. The analyses highlight the importance of duplicate analyses (fringe and central cores) and vigorous statistical analyses for the robust evaluation of aquatic ecosystem change.

Distribution and abundance of aquatic macrophytes in a forested stream: Case study in Kottawa Forest Reserve

Forest ecosystems have been studied for terrestrial components and other faunal assemblages while information on aquatic plants on this regard is scarce. Thus, present preliminary study was designed to study the abundance, distribution and factors influencing on aquatic plant distribution in forested stream selecting “Gong Gawwa Ela” locate in the Kottawa forest reserve. Six sites were selected along a stretch of the stream (~1 km). Those sites were visited once in every month for a period of three months. For each site, plant distribution was observed in a transect across the stream perpendicular to the river bank. Water quality, water flow velocity and sediment composition at each site were also monitored. Eleven aquatic plant species were found along the stream while the most common species were Lagenandra thwaitesii, Aponogeton rigidifolius and Adiantum sp. A significant difference in plant diversity among study sites was noticed where the highest plant diversity was found in the most downstream site. Irrespective to the species; distribution of above three species exhibited a significant positive correlation to the sediment composition. Further, diversity of aquatic plant was significantly correlated to the abundance of L. thawaitsii. There was no significant difference in dissolved oxygen, pH, temperature and biological oxygen demand among study sites. Present study revealed that sediment composition and the abundance of L. thawaitsii are two factors that decide the architecture of the aquatic plant communities along this stream.

Identifying and quantifying environmental thresholds for ecological shifts in a large semi-regulated river

ABSTRACTEcological shifts, between a clear macrophyte-dominated state and a turbid state dominated by phytoplankton and high inorganic suspended solids, have been well described in shallow lake ecosystems. While few documented examples exist in rivers, models predict regime shifts, especially in regulated rivers with high water retention time. Here I quantified ecological shifts in a large, semi-regulated floodplain river during a transition from a turbid- to a clear-water state using water quality, aquatic vegetation and fisheries data from a rigorous, standardized long-term data set. My findings indicate that significant changes occurred in total suspended solids concentration, aquatic macrophyte abundance, native and non-native fish biomass, fish functional feeding guild patterns, fish habitat guild assemblages and fish spawning guild assemblage patterns over a nearly 20-year period in Navigation Pool 8 of the Upper Mississippi River. Transitions in physical and biological indicators were examined to identify mechanisms underlying the ecological shifts. Environmental variables driving fish assemblage changes were identified (total suspended solids and aquatic vegetation) and management-relevant thresholds are presented. Awareness of management thresholds is critical for resource managers to implement measures to prevent the river from moving to a degraded state characterized by high non-native fish abundance and low predatory fish species abundance.

Fishes from Baía da Medalha, southern Pantanal, Brazil: A 20 years review

Abstract Located in the Pantanal of Miranda-Abobral, the Baía da Medalha is the largest pond close to the Base de Estudos do Pantanal of the Universidade Federal de Mato Grosso do Sul. The Baía da Medalha has been a study site for several didactic and scientific projects for years. Nevertheless, its fish fauna has never been inventoried. Based on data collected from the beginning of the 1990s up to 2011, we provide a list of fish species from the Baía da Medalha. A total of 97 species were recorded, corresponding to about 40% of the species stated for the Pantanal. Characiformes and Siluriformes were the most species-rich orders, being Characidae and Cichlidae the families with the highest number of species. Regional seasonal flood dynamics and the abundance of aquatic macrophytes may be associated with this high diversity. The representative richness found in this lagoon highlights the importance of such taxonomic surveys to preserve the diversity of aquatic habitats within the Pantanal ecosystem.

Proposal for estimating volume based relative abundance of aquatic macrophytes

In aquatic macrophyte ecology, species abundance is usually estimated by cover values expressed on the ordinal scale. Recently, there has been increasing demand for three-dimensional estimates of plant abundance. To extend ordinal cover data into three dimensions, a new formula is proposed which considers the vertical developmental types of plants. In this, a constant k is used with three different values reflecting three groups of macrophytes, namely the “free floating leaved”; “rooted, floating leaved” and “submersed leaved” species. By using the new formula, inappropriate conversion and evaluation of ordinal abundance data occurring frequently in the literature may also be avoided.

Aquatic macrophyte community varies in urban reservoirs with different degrees of eutrophication

AIM: Investigate spatial and temporal variation in the aquatic macrophyte community in four urban reservoirs located in Curitiba metropolitan region, Brazil. We tested the hypothesis that aquatic macrophyte community differ among reservoirs with different degrees of eutrophication. METHODS: The reservoirs selected ranged from oligotrophic/mesotrophic to eutrophic. Sampling occurred in October 2011, January 2012 and June 2012. Twelve aquatic macrophytes stands were sampled at each reservoir. Species were identified and the relative abundance of aquatic macrophytes was estimated. Differences among reservoirs and over sampling periods were analyzed: i) through two‑way ANOVAs considering the stand extent (m) and the stand biodiversity - species richness, evenness, Shannon-Wiener index and beta diversity (species variation along the aquatic macrophyte stand); and ii) through PERMANOVA considering species composition. Indicator species that were characteristic for each reservoir were also identified. RESULTS: The aquatic macrophyte stand extent varied among reservoirs and over sampling periods. Species richness showed only temporal variation. On the other hand, evenness and Shannon-Wiener index varied only among reservoirs. The beta diversity of macrophyte stands did not vary among reservoirs or over time, meaning that species variability among aquatic macrophyte stands was independent of the stand extent and reservoir eutrophication. Community composition depended on the reservoir and sampling period. CONCLUSIONS: Our results support our initial expectation that reservoirs of different degrees of eutrophication have different aquatic macrophyte communities. As a consequence, each reservoir had particular indicator species. Therefore, monitoring and management efforts must be offered for each reservoir individually.