Feeding habits of the mochokid Synodontis punctifer Daget, 1964, in the Bandama River,Côte d'Ivoire

The feeding habits of Synodontis punctifer were investigated in the basin of the Bandama River. Fish specimens were collected using gill nets in the rainy season (May–July 2009) and in the dry season (November 2008 to March 2009 and August 2009). In this article, the importance of the different prey types was assessed using the corrected occurrence and weight percentage. These values were used to calculate the index of preponderance for each taxonomic category. One hundred and ten specimens of S. punctifer were examined, nine stomachs were found empty (8.18%). A total of 39 different prey species belonging to seven major groups Insects, Crustacea, Rotifera, Molluscs, Other invertebrates, Other organisms and Macrophytes were identified in the stomach contents. The results showed that Macrophytes were the primary food item and Insects the secondary prey item. Other preys were recorded occasionally. At the rainy season, the main foods of S. punctifer were Macrophytes and during the dry season this species ate Insects and Macrophytes. The food composition varied between localities. In the riverine localities, specimen fed on 38 prey types. Twenty‐seven prey categories were consumed in the lacustrine. In terms of diet overlap, Schoener coefficient values were above the 0.6 limit (α = 0.99), indicating some high overlap.     

Factors influencing macrophyte metrics in Estonian coastal lakes in the light of ecological status assessment

Macrophytes and factors affecting their distribution were studied in 19 coastal lakes of Estonia. The aim of the study was to determine the factors influencing the distribution of macrophytes in coastal lakes and to assess the suitability of valid macrophyte metrics. Our hypothesis was that in coastal lakes most of the macrophyte distribution patterns are caused by lake-specific variables. Morphological, physico-chemical and catchment area characteristics of the lakes varied greatly. Lakes were in different development stages—lakes nearest to the Baltic Sea were younger and more influenced by brackish water and the furthest lakes were older with more freshwater. All that variability was reflected in macrophyte parameters. Factor analysis of environmental indices divided them into three groups—catchment area, morphometric and water chemistry factors. The first factor may be considered as a pressure and the other two as lake-type-specific factors. Lake catchment area parameters had an influence on Bolboschoenus maritimus, Chara tomentosa and Typha latifolia abundance. Morphometric parameters had an influence on the depth distribution of macrophytes and water chemistry factors on the abundance of helophytes. Current indicator species showed more variability associated with lake-specific factors than with changes in status or the influence of pressures.     

Does macrophyte fractal complexity drive invertebrate diversity,biomass and body size distributions?

Habitat structure is one of the fundamental factors determining the distribution of organisms at all spatial scales, and vegetation is of primary importance in shaping the structural environment for invertebrates in many systems. In the majority of biotopes, invertebrates live within vegetation stands of mixed species composition, making estimates of structural complexity difficult to obtain. Here we use fractal indices to describe the structural complexity of mixed stands of aquatic macrophytes, and these are employed to examine the effects of habitat complexity on the composition of free-living invertebrate assemblages that utilise the habitat in three dimensions. Macrophytes and associated invertebrates were sampled from shallow ponds in southwest England, and rapid digital image analysis was used to quantify the fractal complexity of all plant species recorded, allowing the complexity of vegetation stands to be reconstructed based on their species composition. Fractal indices were found to be significantly related to both invertebrate biomass–body size scaling and overall invertebrate biomass; more complex stands of macrophytes contained a greater number of small animals. Habitat complexity was unrelated to invertebrate taxon richness and macrophyte surface area and species richness were not correlated with any of the invertebrate community parameters. The biomass–body size scaling relationship of lentic macroinvertebrates matched those predicted by models incorporating both allometric scaling of resource use and the fractal dimension of a habitat, suggesting that both habitat fractal complexity and allometry may control density–body size scaling in lentic macroinvertebrate communities.     

Effects of resource pulses on nutrient availability,ecosystem productivity,and temporal variability following a stochastic disturbance in eutrophic glacial lakes

Tropical macrophytes sold in the live garden trade are perceived as unlikely to invade temperate regions owing to climate mismatches. Here we study two tropical macrophytes (Pistia stratiotes and Eichhornia crassipes) not previously considered an invasion risk but which were recently discovered in the Great Lakes, and determine mechanisms that may be responsible for their continued presence including human introduction, reproduction through viable seeds and tolerance of winter conditions. Surveys conducted in 2011 and 2012 revealed recurrent presence of one or both species at some sites. Macrophytes in in situ enclosures failed to survive winter conditions, with plant health declining progressively prior to mortality. Water hyacinth seeds were field-collected, identified using Sanger sequencing, and germinated at 28°C with or without scarification. Germination was highest for scarified versus non-scarified seeds. Human introduction was observed at two sites, one involving both species, the other only water hyacinth. These species likely persist through a combination of annual reintroduction (both species) and possibly by production of viable seed (water hyacinth). Macrophytes, particularly water hyacinth, that were not previously viewed as a threat to the Great Lakes owing to environmental incompatibility may need to be reassessed.     

Primary and secondary effects of methabenzthiazuron on plankton communities in aquatic outdoor microcosms

The primary and secondary effects of methabenzthiazuron on plankton were studied in outdoor microcosms (6 m3) for five months. Macrophytes, phytoplankton, zooplankton and the emergence of insects were examined. The herbicide was added to nine of the twelve mesocosms in concentrations ranging from 10 to 3371 μg a.i. l−1 in a single application. The other three ponds were used as untreated controls. Phytoplankton population dynamics fluctuated depending on light intensity, temperature, nutrients, competition and herbicide concentrations. Primary production was temporarily inhibited at test concentrations from 89 to 3371 μg l−1. Cryptophyta (Phytoflagellata) showed also a recovery at the higher concentrations during the study period. Other primary producers did not recover at these concentrations, as expected from the disappearance curve of the active ingredient at these concentrations. This was also indicated by structural indices such as the diversity, eveness and similarity index. The lower concentrations evoked no or only short-term, weak responses. Chemical water parameters were strongly influenced by the absence of macrophytes (Elodea canadensis) at the high application rates, which also caused significant changes in zooplankton communities. No effects were observed on macro-invertebrates and benthic organisms. In conclusion, noticeable effects were detected only at concentrations clearly above the effect threshold known from standard laboratory tests with aquatic primary producers. This revised version was published online in August 2006 with corrections to the Cover Date.     

Tropical macrophytes promote phytoplankton community shifts in lake mesocosms: relevance for lake restoration in warm climates

Hydrobiologia - Macrophytes can be crucial for maintaining clear water conditions in temperate shallow lakes. However, their restorative potential and role in regulating phytoplankton remains...     

Production of the rotifer Brachionus plicatilis for aquaculture in Kuwait

Macrophytes, plankton samples, salinity and depth data were collected from wetlands in October 1981. Species diversity and distributions are recorded and relationships drawn between macrophytes and plankton occurrence. An examination of the data of Geddes et al. (1981) enables comparisons of species composition in a similar range of Western Australian lakes in 1978 at a different stage in the seasonal cycle. Comparison with the biota of salt lakes in Australia's eastern states and elsewhere lead to biogeographical speculations for the macrophytes and for some of the planktonic species.     

Die Möglichkeiten der Gewässerreinigung mit höheren Pflanzen nach den bisherigen Untersuchungsergebnissen und theoretischen Überlegungen

The Possibilities of Water Purification by Macrophytes According to the Hitherto Existing Results and Theoretical Considerations     

Macrophytes in boreal streams: Characterizing and predicting native occurrence and abundance to assess human impact

Macrophytes are a structurally and functionally essential element of stream ecosystems and therefore indispensable in assessment, protection and restoration of streams. Modelling based on continuous environmental gradients offers a potential approach to predict natural variability of communities and thereby improve detection of anthropogenic community change. Using data from minimally disturbed streams, we described natural macrophyte assemblages in pool and riffle habitats separately and in combination, and explored their variation across large scale environmental gradients. Specifically, we developed RIVPACS-type models to predict the presence and abundance of macrophyte taxa at stream sites in the absence of human influence and, used data from impacted streams to explore the responses of three biotic indices to anthropogenic stress. The indices used, taxonomic completeness (O/E-taxa), a measure of compositional dissimilarity (BC-index) and an index taking into account the abundance of species (AB-index), are based on predicted and observed macrophyte communities. We found that size of the catchment area, altitude, latitude and percentage of lakes in the catchment were the large scale environmental variables that best predicted the natural variation of assemblages. The RIVPACS approach substantially improved both the precision and accuracy to predict the natural communities and the sensitivity to human disturbance. O/E-taxa performed best in relation to the null model decreasing the variation by 20% in pools, 29% in riffles and 32% in combined data. In general, models based on the riffle assemblages performed better than models based on pool assemblages, but including both habitats and predicting abundances instead of only presence/absence yielded the greatest accuracy and sensitivity. Our results support the use of multivariate modelling techniques in predicting reference condition to assess status of stream macrophyte communities.     

Hydrophyte-macroinvertebrate interactions in Zwemlust,a lake undergoing biomanipulation

In two years after biomanipulation of Lake Zwemlust (The Netherlands), macrophytes (helophytes, elodeids) and filamentous algae developed luxuriantly in the lake. They influenced the structure of macroinvertebrate communities inhabiting them. Macrophytes and algae, by changing environmental and trophic conditions, also affected the composition of macrozoobenthos. Vascular plants served as an important source of food for zoobenthos and phytofauna, mainly after they were decomposed. Filamentous algae were consumed readily alive by many animals. Invertebrates appeared to be important as a potential nutrient source for hydrophytes.     

Aquatic Macrophyte Approach to Assess the Impact of Disturbances on the Diversity of the Ecosystem and on River Quality

Disturbance has long been recognized as an important determinant of community characteristics in aquatic systems. The aims of our study were to evaluate the impact of different disturbances on the macrophyte diversity and on river quality. To this end, we investigated the floristic composition for different stretches impacted by disturbances and we tested both diversity indices and the trophic index (IBMR) “Biological Index Macrophytes in Rivers” in the Moselle river (NE of France). The river was divided into four sections of different lengths based on uniformity of morphological characteristics, substrate conditions and flowing velocity: the upper, the wild, the resectioned and the downstream Moselle. Floristic composition and water chemical parameters were analysed from 1999 to 2001. The man‐made increase of nutrient concentration favoured the floristic richness in the last sites of the upper Moselle, whereas river dynamics and floods did not allow the development of vegetation in the wild Moselle. Disturbances caused by industrial sewage and eutrophication allowed the spreading of pollu‐tolerant and riparian alien species. The aquatic macrophyte approach is a useful means to detect impact of disturbances on diversity and on river quality. However, it was not effective in assessing disturbances such as flood overflow or chemical pollution. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Horizontal distribution of cladocerans in arctic Greenland lakes – impact of macrophytes and fish

Submerged macrophytes may play an important role as a refuge for zooplankton against predators. However, a recent study suggests that their importance depends on the trophic state of the lake. We studied the impact of fish and macrophytes on the horizontal distribution of pelagic cladocerans in 56 oligotrophic arctic Greenland lakes. In north-east and western Greenland, zooplankton was sampled in the near-shore (littoral) and central (pelagial) part of all lakes and fish were sampled with multiple mesh-sized gill nets. Macrophytes were visually estimated in the littoral. In north-east Greenland, 5 taxa of cladocerans were found, while 14 taxa were recorded in western Greenland. Daphnia pulex occurred only in fishless lakes in both northeast and western Greenland and avoided the near-shore areas in the shallow and deep lakes. Bosmina spp. and Holopedium gibberum were evenly distributed between the littoral and the pelagial in the deep and shallow fishless lakes. However, their near-shore density was lowest in the presence of fish. Macrophyte-related and benthic cladocerans concentrated either in the littoral or were evenly distributed between the littoral and the pelagial, irrespective of depth and fish presence or absence. Macrophytes had no impact on the horizontal distribution of pelagic cladocerans. Thus, it is concluded that horizontal heterogeneity of Bosmina spp. and Holopedium gibberum might be affected by the presence of fish.     

Niche congruency of aquatic macrophytes in central North America with respect to 5 water chemistry parameters

The occurrences of aquatic macrophytes were studied at 430 sites in central North America with respect to total alkalinity, chloride, sulphate, molybdenum reactive phosphorus and dissolved organic matter. Mean niche positions were calculated for the combination of 5 parameters by comparing mean values for each species using agglomerative hierarchical cluster analysis. Overall niche relations were examined by calculating and summing the amount of overlap in the observed ecological tolerance ranges for the 5 parameters for each species pair, and applying cluster and principal component analysis. The results showed that the macrophytes occupied a broad spectrum of niches, ranging from species found at low inorganic concentrations and narrow tolerance ranges, to species occupying broad ranges in the study area. Species with similar overall niches differed with respect to their mean niche positions, and vice versa. Macrophytes with similar niche positions may use a number of strategies to reduce interspecific competition.     

The role of macrophytes,especiallyZostera marina,in the carbon cycle of Lake Grevelingen (IV)

Summary Macrophytes in Lake Grevelingen comprise macroalgae (Ulva, Enteromorpha, Chaetomorpha) and eelgrass (Zostera marina). In terms of production of organic matter far out the largest share comes from eelgrass. Eelgrass showed an enormous increase after the closure of the dam in 1971: in 1968 the phanerogam covered an area of 1200 ha, and in 1978 this area was 4400 ha (Fig. 3).     

Assessing trout farm pollution by biological metrics and indices based on aquatic macrophytes and benthic macroinvertebrates: A case study

In this study we examine the ecological responses of aquatic macrophytes and benthic macroinvertebrates to a trout farm effluent located in the upper Tajuña River (Guadalajara province, Central Spain), comparing the suitability of biological metrics and indices based on these two communities to assess trout farm pollution in the upper reaches of fluvial ecosystems. Sampling surveys were carried out in winter and summer 2006, and in spring 2007. Four sampling sites were selected along the study reach: S-1, placed upstream from the trout farm, was used as a reference station; S-2, S-3 and S-4 were placed about 10, 100 and 1000 m downstream from the trout farm outlet, respectively. The stream bottom was mainly stony with cobbles and pebbles at all sampling sites, except at S-2 where it was covered by a thick layer of organic sediment. Aquatic macrophytes and benthic macroinvertebrates significantly increased in abundance downstream from the trout farm effluent, particularly at S-3 and S-4. However, while the diversity of aquatic macrophytes increased downstream (at S-3 and S-4, but not at S-2), the diversity of benthic macroinvertebrates significantly decreased, particularly at S-2. Regarding aquatic macrophytes, moss coverage values, as well as values of the Index of Macrophytes (IM) and the Macroscopic Aquatic Vegetation Index (MAVI), were higher at S-1 than at S-2. In contrast, values of moss coverage and IM were significantly lower at S-1 than at S-3 and S-4. MAVI values were similar at S-1, S-3 and S-4. Regarding benthic macroinvertebrates, the abundance percentage of oligochaetes and chironomids (expressed as OC%) was significantly higher at downstream polluted sites (particularly at S-2) than at S-1. Conversely, the abundance percentage of ephemeropterans, plecopterans and trichopterans (expressed as EPT%), and scores of the total Biological Monitoring Water Quality (t-BMWQ) index and the average Biological Monitoring Water Quality (a-BMWQ) index were much lower at S-2 than at S-1, with a clear tendency to increase with increasing downstream distance from the trout farm. Correlation analyses showed that changes in physicochemical parameters (inorganic nutrients, dissolved oxygen and turbidity) along the study reach were better correlated with changes in metrics and indices based on benthic macroinvertebrates. Overall it is concluded that metrics and indices based on benthic macroinvertebrates (such as OC% and EPT% metrics and t-BMWQ and a-BMWQ indices) can be more suitable than those based on aquatic macrophytes for the biological monitoring of trout farm pollution in the upper reaches of fluvial ecosystems, since the higher diversity of benthic macroinvertebrates inhabiting the river bottom would permit this community to exhibit a better indicator performance regarding the environmental stress caused by trout farm effluents. However, further studies are needed in order to generalize this conclusion.     

Littoral chironomid communities in an arctic Alaskan lake

The soft-sediment littoral zone of arctic Toolik Lake (68°N) is composed of patches of macrophytes and bare sediments, which support distinct communities of chironomid larvae. Macrophytes were typically dominated by Stictochironomus rosenschoeldi (Zett.) but also had persistent populations of Heterotrissocladius maeaeri Brund., Paratanytarsus spp., Ablabesmyia sp., as well as several other less common taxa. Bare sediments were dominated by H. maeaeri, Parakiefferiella sp., and Zalutschia zalutschicola Lip. S. rosenschoeldi was common in bare sediments hut far less so than in macrophytes. Few taxa were restricted to either habitat. Life cycle lengths, estimated for some species, ranged from 1 to 4 yr. Analysis of indicator species suggested that Toolik is oligotrophic to ultra-oligotrophic, which is consistent with the available primary production estimate for Toolik Lake. Littoral chironomid communities, in addition to profundal communities, may be useful in lake typology.     

Feeding ecology of Oreochromis niloticus (Linnaeus) & Tilapia Zillii (Gervias) in a Nile canal

Fish stomachs, 1149 for Tilapia zillii and 1698 for Oreochromis niloticus, were collected from April 1984 till April 1985 from a Nile canal in the Egyptian delta. Both species showed a significant overlap of diet (Schoener's index) among individuals ranging from 12 to 17.9 cm standard length. Outside this range differences in the importance of food of animal origin occurred. Macrophytes were the main food of O. niloticus and aquatic insects of the food of T. zillii. This initial diet overlap may have contributed to irregularity in the increase of full stomachs with increasing length, and to a decline of the stomach index (SI = stomach weight × 100/fish weight) with increase in length in O. niloticus. The stomach of either species correlated significantly with water temperature, but with daily photoperiod in O. niloticus only.     

Effect of a nitrogen pulse on ecosystem N processing at different temperatures: A mesocosm experiment with 15NO3− addition

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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.

     

Macrophyte refuges, prey behaviour and trophic interactions: consequences for lake water clarity

Macrophytes may enhance grazing on phytoplankton by providing a refuge for zooplankton against fish predation. Loss of macrophytes can trigger sudden degradation of water clarity (regime shift) in lakes. However, the presence of piscivores may drive planktivorous fish to take refuge amongst littoral macrophytes. To address the possibility of regime shifts, I here constructed an empirically based model that combined population dynamics of organisms with game theory for optimal habitat selection, taking into consideration the trophic structure, lake size and eutrophication. The model showed that macrophytes generally acted as a refuge for zooplankton, rather than for fish. The model predicted that regime shifts were more likely in small, shallow lakes and that the presence of macrophytes raised the possibility of regime shifts. The present study demonstrated that the fast dynamics of animal behaviour could lead to regime shifts, in connection with slower variables such as nutrient loading.