Diatoms on herbarium macrophytes as indicators for water quality

To describe the reference situation for water quality in the eutrophicated broad area De Nieuwkoopse Plassen (Holland), attached diatoms from aquatic macrophytes, collected between 1934 and 1958 have been used. Recent samples for comparison were taken in 1989.The diatoms do not indicate significant changes in salinity. Eutrophication has reduced the number of rare species and increased the abundance of meso- to hyper-eutraphentic species, particularly Fragilaria berolinensis. Reduction of total phosphorus to concentrations below 0.02 mg 1^–1 might be sufficient to restore the diatom assemblages of the 1930s.     

Submerged macrophytes as indicators of the ecological quality of lakes

1. We analysed submerged macrophyte communities from 300 Danish lakes to determine the efficacy of different species, maximum colonisation depth (C_max) of plants as well as coverage and plant volume inhabited (PVI) as indicators of eutrophication. 2. Most species occurred at a wide range of phosphorus and chlorophyll a (Chla) concentrations, but some species of isoetids (Lobelia, Isoëtes) and Potamogeton (Potamogeton gramineus, Potamogeton alpinus and Potamogeton filiformis) were mainly found at low nutrient concentrations and hence may be considered as indicators of nutrient poor conditions. However, species typically found in nutrient‐rich conditions, such as Elodea canadensis and Potamogeton pectinatus, were also found at total phosphorus (TP) <0.02 mg P L^?1 and Chla <5 μg L^?1 and therefore cannot be considered as reliable indicators of eutrophic conditions. 3. Submerged macrophyte coverage, PVI and the C_max were negatively correlated with TP and Chla. However, variability among lakes was high and no clear thresholds were observed. At TP between 0.03 and 0.07 mg P L^?1 plant coverage in shallow lakes ranged from nearly 0 to 100%, whilst at concentrations between 0.10 and 0.20 mg P L^?1 only 29% of the lakes had coverage >10%. C_max was found to be a useful indicator only in deep lakes with unvegetated areas in the deeper part, whereas the use of coverage was restricted to shallow lakes or shallow areas of deep lakes. 4. Overall, submerged macrophytes responded clearly to eutrophication, but the metrics investigated here showed no well‐defined thresholds. We developed a simple index based on species richness, presence of indicator species, coverage and C_max, which might be used to track major changes in macrophyte communities and for lake classification.     

Classifying aquatic macrophytes as indicators of eutrophication in European lakes

Aquatic macrophytes are one of the biological quality elements in the Water Framework Directive (WFD) for which status assessments must be defined. We tested two methods to classify macrophyte species and their response to eutrophication pressure: one based on percentiles of occurrence along a phosphorous gradient and another based on trophic ranking of species using Canonical Correspondence Analyses in the ranking procedure. The methods were tested at Europe-wide, regional and national scale as well as by alkalinity category, using 1,147 lakes from 12 European states. The grouping of species as sensitive, tolerant or indifferent to eutrophication was evaluated for some taxa, such as the sensitive Chara spp. and the large isoetids, by analysing the (non-linear) response curve along a phosphorous gradient. These thresholds revealed in these response curves can be used to set boundaries among different ecological status classes. In total 48 taxa out of 114 taxa were classified identically regardless of dataset or classification method. These taxa can be considered the most consistent and reliable indicators of sensitivity or tolerance to eutrophication at European scale. Although the general response of well known indicator species seems to hold, there are many species that were evaluated differently according to the database selection and classification methods. This hampers a Europe-wide comparison of classified species lists as used for the status assessment within the WFD implementation process.     

Aquatic macrophytes in saline lakes of the Canadian prairies

Vascular macrophyte species richness decreases with increasing salinity. Only three species of submerged plants (Potamogeton pectinatus, Ruppia maritima, R. occidentalis) tolerate hypersaline waters (>50 g l^-1, total of ionic constituents). Eight emergent species occur in more saline habitats but only five (Scirpus maritimus var. paludosus, Distichlisstricta, Puccinellia nuttalliana, Scirpus americanus, Triglochin maritima) occur commonly over a range of saline lakes into the hypersaline category. Usually, species tolerant of high salinities are found over the entire saline spectrum and even extend into subsaline waters (<3 g l^-1) and thrive there. A major increase in the number of species occurs below 5 g l^-1. As the water recedes plants such as Salicornia rubra, Suaeda calceoliformes, Hordeum jubatum and Sonchus arvensis invade.Submerged angiosperm distribution is controlled by total ion concentration and substrate texture plays no apparent role. Although angiosperms normally grow in all kinds of substrates, they occupy coarse substrates in Wakaw lake because suitable fine substrates are densely colonized by charophytes. In this lake light limited growth occurs to a depth of 5% of surface light. Light was not limiting in Redberry Lake but angiosperm growth was limited to the upper 8 m (10% or more of surface light). Thermal stratification and depth (pressure) were probably limiting istead. In meromictic Waldsea Lake the depth of the chemocline (6 m, 5% surface light) delimits angiosperm growth.     

Aquatic plants as environmental indicators of ecological condition in New Zealand lakes

Submerged aquatic plants can act as measurable indicators of ecological conditions occurring within a lake, and they need only be monitored once a year or even less. Historically in New Zealand there has been a reliance on water quality sampling for monitoring the health of lakes and these methods can be complex and costly involving multiple site visits and chemical analysis of water samples. As a result, lake monitoring has been irregular, or not done at all. LakeSPI or ‘Lake Submerged Plant Indicators’ is a new management tool that uses aquatic plants to monitor and assess ecological condition in a wide range of lake types. The method generates three indices: a Native Condition Index (extent and diversity of native plants) and an Invasive Condition Index (extent and impact of alien weeds), which are generated from scores allocated to carefully selected vegetation features; and an integrated LakeSPI Index which is largely derived from components of the other two indices and provides an overall indication of lake ecological condition. The LakeSPI method can be used to assess the status of lakes and monitor trends occurring within them, and it is expected that the use of LakeSPI will facilitate regular monitoring and reporting on a much wider range of lakes than has been possible using traditional water quality methods. By utilizing submerged aquatic plants the method focuses on lake littoral margins where there is greatest public interaction and interest.     

Aquatic insect larvae as indicators of limiting minimal contents of dissolved oxygen

Minimal concentrations of oxygen are limiting factors for limnic biocenoses. It should therefore be possible to use biocenose structure to infer minimal oxygen concentrations that have occured, provided the tolerance of the organisms concerned is known. A simple apparatus used to measure LC₅₀ of oxygen for aquatic insect larvae with tracheal gills is described. Lethal concentrations found in some Ephemeroptera differ between species. Usually, they are strongly temperature dependent. In the species so far studied, confidence intervals are very small and suggest that such insect larvae could be used as bioindicators of minimal oxygen concentrations (even of short term ones), especially in thermically stable waters.     

Aquatic macrophytes and water current velocity in the Danube River

Water currents are among the strongest environmental variables determining the occurrence and/or abundance of aquatic plants and the European Water Framework Directive (WFD) considers river morphology and current conditions important aspects of reference conditions. We used the database of the Joint Danube Survey JDS-2, organised by the International Commission for the Protection of the Danube River (ICPDR, Vienna), to assess the relationship between water flow velocity and the occurrence and abundance of aquatic macrophyte to be species along the navigable reach of the Danube River. Species abundance was assessed in accordance with European Standard EN 14184-2003. Flow velocities were assessed close to the plant stands and estimated in 4 classes, worked out in earlier studies in combination with flow meter measurements, which is appropriate for the conditions in this large river. Statistical analysis revealed that only survey units with either no visible flow or those with fast flow were characterised by indicator species with high significance. Still water conditions or barely visible flow (flow class 1) were indicated by Potamogeton friesii, Nitellopsis obtusa and Trapa natans, and by Potamogeton perfoliatus, Potamogeton nodosus and Stuckenia pectinata. Lemna minor, indicative for flow class 1 as well, was detected in all the other flow classes, too: in all these cases it established its stands closely intermingled with other aquatic species. For survey units with slow (flow class 2) or intermediate flow (flow class 3). No statistically significant indicator species could be determined. The highest flow velocities (flow class 4) were significantly indicated by Fissidens rufulus, Cinclidotus fontinaloides and Cinclidotus riparius. Occurrence of aquatic mosses was also highly related to the Berger–Parker dominance index in NMDS analysis. In the same analysis, but towards the smallest flow velocities, the majority of vascular species and the Simpson diversity index were closely related. The spectrum of life forms was considerably reduced under medium and high flow velocity conditions. With regard to Simpson species diversity, our analysis indicates an agglomeration of diversity in the Middle Danube reach that includes the Iron Gates impoundment. Our results offer a first look at the macrophyte/water flow relationship of a very large river in Europe, the Danube.     

Aquatic macrophytes in the large, sub-tropical Itaipu Reservoir, Brazil

In the last three decades, rapid assessment surveys have become an important approach for measuring aquatic ecosystem biodiversity. These methods can be used to detect anthropogenic impacts and recognize local or global species extinctions. We present a floristic survey of the aquatic macrophytes along the Brazilian margin of the Itaipu Reservoir conducted in 2008 and compare this with a floristic survey conducted ten years earlier. We used ordination analysis to determine whether assemblage composition differed among reservoir arms. Macrophyte species were sampled in each of the 235 sampling stations using a boat, which was positioned inside three places of each macrophyte stand to record species and search for small plants. We also collected submerged plants using a rake with the boat moving at constant velocity for ten minutes. We assigned individual macrophyte species to life form and identified representative species for each life form. A total of 87 macrophyte taxa were identified. The "emergent" life forms contained the highest number of species, followed by "rooted submerged" life forms. The extensive survey of macrophytes undertaken in September 2008 recorded more species than a survey conducted between 1995 and 1998. This could be due to changes in water physico-chemistry, disturbances due to water drawdown and the long period between surveys, which may have allowed natural colonization by other species. Additionally, differences in the classification systems and taxonomic resolution used in the surveys may account for differences in the number of species recorded. Assemblage composition varied among the arms and was affected by underwater radiation (as measured using a Secchi disk) and fetch. Five non-native species were found. Two of these non-native species (Urochloa subquadripara and Hydrilla verticillata) are of special concern because they have a high frequency of occurrence and occupy large marginal areas of the reservoir. Future surveys should be conducted to determine the habitat most frequently colonized by these species. This would allow management strategies to be developed to protect native aquatic biota and prevent interference with the recreational and commercial uses of the Itaipu Reservoir.     

Aquatic invertebrate assemblages as potential indicators of restoration conditions in wetlands of Northeastern China

Wetland restoration has been implemented widely but evaluation of the effectiveness of wetland restoration has been limited. In this study, we aimed to investigate the utility of aquatic invertebrate assemblages as potential indicators of restoration condition in wetlands of the Sanjiang Plain, Northeastern China. Results from non‐metric multidimensional scaling analysis of invertebrate assemblages showed that study wetlands (n = 16) divided into two groups: natural wetlands and wetlands that have been restored for 4 years were classified as a group, and impaired wetlands and wetlands restored for only 1 year were classified into another group. After 4 years of recovery, 47.9% of invertebrate taxa found at the natural wetlands could also be found at the restored wetlands, primarily insects with aerial dispersal capabilities for rapid colonization. Indicator species analysis identified differences in community composition among wetland types, and Amphiagrion sp. and Bezzia sp. were indicators of the restored wetlands. In Northeastern China, aquatic invertebrate assemblages and certain indicator species may provide robust measures of wetland restoration. It is urgent for further exploration to monitor restored wetlands in the long‐time series and fully assess the efficiency of the restoration.     

Aquatic macrophytes mediated remediation of toxic metals from moderately contaminated industrial effluent

The present study assessed Zn, Cr, Cd, and Pb removal efficiency of Colocasia esculenta, Hydrilla verticillata, Phragmitis australis, Typha latifolia, and Spirodella polyrhiza from sewage-mixed industrial effluent. The fresh/dry weight and relative growth rate of each macrophyte decreased with increasing effluent concentration. H. verticillata and C. esculenta exhibited better growth at 50% effluent over control. The maximum Zn, Cd, and Pb accumulation (1008.23, 28.03, and 483.55 mg/kg dry wt., respectively) was recorded in C. esculenta, whereas Cr (114.48 mg/kg dry wt.) in H. verticillata at 100% effluent. Metal accumulation in roots of all plants species was higher (≥50%) initially with increasing effluent concentration and later transferred to shoots. All plants exhibited BCF >1.0 for all heavy metals, highest being for Zn (91.2) and Cd (75.2) in H. verticillata, for Cr (97.9) and Pb (103) in C. esculenta. Except S. polyrhhiza, all other plants exhibited TF <1.0. Maximum removal efficiency of Zn was 82.8% by H. verticillata, whilst that of Cr, Cd, and Pb by C. esculenta at 50% effluent, demonstrating wide applicability of H. verticillata and C. esculenta for treatment of mixed industrial effluent having heavy metals.     

Aquatic macrophytes, macroinvertebrate associations and water levels in a lowland Tasmanian river

Aquatic macrophytes are a common habitat for macroinvertebrates and may occupy depth zones in the littoral region of lowland rivers. Studies have indicated that different species of macrophyte typically support different assemblages, abundances and numbers of species of macroinvertebrates. This has often been attributed to differences in the dissectedness of stems and leaves of the macrophytes, resulting in differences in the surface area and/or the number of microhabitats available to invertebrates. I set out to measure the abundance and taxonomic richness and to describe the macroinvertebrate assemblages associated with three species of aquatic macrophyte in a pool in the Macquarie River, Tasmania and to examine responses of these variables to changes in water levels over summer. The macrophyte species sampled wereMyriophyllum simulans/variifolium, Triglochin procera} and Eleocharis sphacelata, each one differing in the dissectedness of its stems and leaves and its location in the littoral zone. Whereas the greatest abundance of macroinvertebrates was found associated in all months (i.e. at all water levels) with the structurally complex and shallowest macrophyte species, Myriophyllum, the number of taxa associated with this species was in several cases lower than for the structurally simpler and deeper water Triglochin and Eleocharis. While water depth and total plant biomass of samples were often correlated with invertebrate abundance and richness, these relationships were different for each macrophyte species. Of the nine most common invertebrate taxa collected from all samples, the abundances of more than half showed consistent differences among macrophyte species across months, two showed differences among macrophytes, but with an interaction with month and two showed no differences among macrophytes. There were major differences in the invertebrate assemblages associated with each macrophyte species in any one month, however, there was also a large turnover of taxa associated with the species of macrophytes from one month to the next. Changes in water level and concomitant changes in environmental variables are suggested as factors influencing the invertebrate fauna in the littoral zone of the pool of the Macquarie River. It is thus important for river managers to be aware that species of macroinvertebrates are not evenly distributed across species of macrophyte and that water levels and their influence on macrophytes as invertebrate habitat may play an integral part in determining the abundance, richness and assemblage of invertebrates in rivers.     

Aquatic macrophytes are important substrates for Libellulidae (Odonata) larvae and adults

Limnology - Understanding the role of abiotic and biotic factors on biological communities is a challenge for ecologists. Individuals of the order Odonata have a close connection with these...     

Aquatic macrophytes of Lake Bled: changes in species composition,distribution and production

The macrophytes of Lake Bled were studied from 1987 to 1990. Three main factors influenced the decline of the aquatic vegetation in the lake during that period: (1) reduced light in the littoral zone due to an increase in phytoplankton (2) grazing by herbivorous fish and waterfowl, and (3) direct human impact.     

Modern distribution of ostracodes and other limnological indicators in southern Lake Malawi: implications for paleocological studies

This modern distribution study from the southwest arm of Lake Malawi quantitatively relates variables of the lake environment to surficial assemblages of ostracodes and other paleoenvironmental indicators (molluscs, Botryococcus, fish, and charcoal) from 102 sites, across a gradient of littoral to shallow profundal conditions. The goal of this research is to use the resultant relationships to help quantify paleoecological interpretations of the fossil record from sediment cores. Site locations varied by depth (1–60 m) and adjacent shoreline environment. Thirty-three ostracode species are identified from 54 sites including four new, undescribed species of Cypridopsinae (2) and Limnocythere (2). Ostracodes are extremely abundant between 1 and 25 m water depth, but are rare to absent between 30 and 60 m. This disappearance is probably taphonomically controlled, with carbonate dissolution in the death assemblage since abundant live ostracodes have been found in the lake at greater than 30 m depth, where bottom sediments lack calcium carbonate. Constrained correspondence analysis (CCA) of ostracode species abundance suggests depth and dissolved oxygen (DO) content to be the primary environmental variables affecting their distribution. Additional CCA models using all biological indicators suggest limnologic variables correlated with depth (e.g., bottom water temperature and DO) and adjacent shoreline environment were most significant.     

Aquatic bryophytes as ecological indicators of the water quality status in the Tiber River basin (Italy)

A survey of 18 watercourses of the Tiber River basin was carried out to define the ecological niche breadth of some aquatic bryophyte species in relation to environmental factors. Aquatic bryophytes were sampled and water environmental parameters were measured at 99 stations distributed along the catchment (from the headwater regions to the downstream reaches). The datasets of the collected species and environmental data were analyzed by using a multivariate statistical analysis (PCA biplot). Ecological responses of the recorded aquatic bryophytes were obtained using a fuzzy set approach, and were compared with data from literature. The results show that the presence of the aquatic bryophytes in watercourses is affected negatively by the reduction of water velocity, clearness, substratum size and the worsening quality of the water physico-chemical status. In fact, aquatic bryophytes show a general preference for stations characterized by medium-large granulometry, and fast-flowing, clear, oxygenated (mean value 9.2 mg/l), cool waters (mean value 15.0 °C), with low loads of nutrients, particularly ammonia (mean value 0.10 mg/l) and phosphates (mean value 0.09 mg/l). However, ecological responses reveal different patterns in the distribution of aquatic bryophyte species mainly in relation to water physico-chemical parameters (e.g. temperature, conductivity, ammonia, phosphates). E.g. Palustriella commutata var. commutata, Cratoneuron filicinum, Fissidens viridulus and Cinclidotus aquaticus show high preference for clear, turbulent and fast-flowing waters, with temperature below 12 °C, conductivity below 300 μS/cm, and concentrations about 0.01 mg/l for phosphates, not exceeding 0.10 mg/l for ammonium ions and 0.90 mg/l for nitrates. Leptodictyum riparium and Riccia fluitans are for their part more linked to turbid and slow waters affected by eutrophication, showing optimum values for about 0.30 mg/l for ammonia concentration, 0.90 mg/l for nitrates and 0.11 and 0.22 mg/l for phosphates respectively. Conversely, Fontinalis antipyretica is not closely related to specific conditions, showing wide ecological ranges for most of the analyzed environmental factors. This paper has evaluated and discussed the possible use of sampled species as bioindicators for biomonitoring of the water quality.     

Trematode metacercariae of fishes as sentinels for a changing limnological environment

Trematode metacercaria populations infecting cichlids in Lake Kinneret (Sea of Galilee) were used as sentinels for the changing limnological environment. Parasitological data from 0+ cichlid fingerlings (Tilapia zillii, Oreochromis aureus, Sarotherodon galilaeus) were collected from the northwest shore of the lake during 1999 to 2001 and compared with data obtained from 1982 to 1984. The results show that the composition of the metacercarial populations changed significantly between the 2 samplings periods. The total number of metacercarial species found in the Kinneret cichlids was lower in 1999 to 2001 than in 1982 to 1984. Metacercariae transmitted by the snail Bulinus truncatus (Clinostomum tilapiae, Euclinostomum heterostomum, Bolbophorus levantinus and Neascus-type metacercariae--black spot and others) that were commonly found in 1982 to 1984 were absent from the fishes sampled during 1999 to 2001. The other trematode metacercariae (Centrocestus sp. and Haplorchis sp. transmitted by Melanoides tuberculata, Pygidiopsis genata transmitted by Melanopsis costata, as well as Phagicola longa, Strigeidae sp.1, an unidentified metacercaria typically found in the liver, and glochidia) increased in abundance in fishes sampled during 1999 to 2001. The calculated 'true' species richness of the habitat, extrapolated as a function of sampling effort, was significantly lower in the 1999 to 2001 versus 1982 to 1984 samples, while significantly fewer fishes needed to be sampled ('sampling effort') during 1999 to 2001 in order to reach the 'true' species richness. The higher calculated values of species richness and diversity for the 1999 to 2001 samples despite the overall decline in species number is explained by the overall increase in metacercariae prevalence.     

Aquatic macrophytes and phytoplankton of a quarry lake in the upper Vicenza range: preliminary study

Abstract

The work was carried out during 1995 in a quarry-lake and 13 samplings were performed to gather data on the aquatic flora. Sampling locations both along the shores and in the water provided data to define the position and the amount of covering by macrophytes. As regards the microphytes, considered as the sole phytoplankton component, the composition and the seasonal abundance were evaluated.