Aquatic Macrophyte Richness Research Articles

Environmental Factors as Predictors of Aquatic Macrophyte Richness and Composition in Wetlands of Southern Brazil

The main goal of this study was to determine how much variation in macrophyte richness and composition is explained by wetland area, altitude, water conductivity, and nitrate and total phosphorus concentrations in wetlands in southern Brazil, and to compare these variations in two wetland subsystems (palustrine and lacustrine). A total of 126 wetlands were sampled distributed in two subsystems: 87 palustrine and 39 lacustrine wetlands. A total of 153 species of aquatic macrophytes was found in wetlands of southern Brazil and the mean number of macrophyte species per site was 8.7 (range 1–23). From the variables tested, the altitude and area were the only predictor of macrophyte richness and explained 23.1% of variation in richness. The two first axes generated by CCA explained only 4.4% of the variation in the aquatic macrophytes distribution. The macrophyte richness was similar across lacustrine and palustrine subsystems. While altitude, area and conductivity explained 33.2% of variation in macrophyte richness in the palustrine subsystem, none of the variables were associated with macrophyte richness in the studied lacustrine wetlands.

Species richness of aquatic macrophytes in ponds related to number of species in neighbouring water bodies

The number of species of aquatic macrophytes and the number of neighbouring water bodies (within 500 m) were counted for three botanically rich ponds and three botanically poor ponds in north-east England. The number of species and the sum of records of aquatic macrophytes in the neighbouring water bodies were also determined. The linear regression model of number of species in the ponds against number of species in neighbouring water bodies closely fitted the data. This model suggested that ponds contain both a baseline number of taxa representing long-distance migrants and/or introductions, and a number of species which have come from neighbouring water bodies.

Aquatic macrophyte richness in Danish lakes in relation to alkalinity, transparency, and lake area

We examined the relationship between environmental factors and the richness of submerged macrophytes species in 73 Danish lakes, which are mainly small, shallow, and have mesotrophic to hypertrophic conditions. We found that mean species richness per lake was only 4.5 in acid lakes of low alkalinity but 12.3 in lakes of high alkalinity due to a greater occurrence of the species-rich group of elodeids. Mean species richness per lake also increased significantly with increasing Secchi depth. No significant relationship between species richness and lake surface area was observed among the entire group of lakes or a subset of eutrophic lakes, as the growth of submerged macrophytes in large lakes may be restricted by wave action in shallow water and light restriction in deep water. In contrast, macrophyte species richness increased with lake surface area in transparent lakes, presumably due to expansion of the area colonised by submerged macrophytes. Thus, the size of the colonised area is a better predictor of species richness than lake surface area. The strong increase in species richness accompanying greater transparency can be accounted for by the combined effect of higher colonised area and higher habitat richness along gradients of deeper macrophyte growth.

Aquatic macrophyte richness in Danish lakes in relation to alkalinity, transparency, and lake area

Aquatic macrophyte richness in Danish lakes in relation to alkalinity, transparency, and lake area

Species Richness of Aquatic Macrophytes in Former Channels Connected to a River: A Comparison between Two Fluvial Hydrosystems Differing in Their Regime and Regulation

This paper compares the plant species richness and distribution of two flowing water systems located in functional alluvial forests subject to different hydrodynamics. The study areas are located in the Alsace Rhine floodplain and the braided and anastomosed sector of the upper Rhine. The substrates, through which substantial flows of groundwater occur, are calcareous Rhine gravels, 200 m deep in places. The first sector selected consists of two lateral side arms which are connected to the Rhine and receive highly mineralized bicarbonated waters (conductivity of 500-1000 ,uS cm-'). The second sector is connected to the river Ill, the main tributary of the Rhine in the Alsace floodplain. This sector receives inputs of more acidic waters and of sediments from the Vosges rnountain, and the waters are less highly mineralized (conductivity of 250-600 itS cm-'). The waters of both sectors are classified as eutrophic to hypertrophic. Comparison of the aquatic macrophytes of the flowing waters near the Rhine and the side arms located in the Ill forest shows that the former has greater species richness (43 versus 25 species), greater biomass, as estimated by percentage cover, and a more complex structure (4-5 versus < 3 strata). Plant community structure and diversity are closely related to habitat variability and in turn to the hydrological conditions and fluvial dynamics. In order to maintain the floristic and phytosociological diversity of these ecosystems, it is necessary first to preserve the fluvial dynamics which create and maintain the variation of habitats.

Environmental and biological responses of former channels to river incision: A diachronic study on the upper rhǒne river

AbstractThe impacts of river incision should be a lowering of the river level, which would increase the rate of water flow from the hillslope aquifer to the river and its former channels. If this aquifer is nutrient‐poor, it should favour the oligotrophication of the former channels. However, if the lowering of the water‐table exceeds the depth of the former channels, then it should lead to the drainage of these channels. These hypotheses were tested on two former channels located in a degrading reach of the Rhǒne River (France); the former channels were influenced by floods, seepage water from the river and hillslope groundwater in 1989. The rate of river incision in this reach has increased since 1980 because of gravel extraction from the river bed (0.5 m between 1989 and 1993). Between 1989 and 1993, the reduction of river infiltration and the increase in the amount of water from the hillslope aquifer in the former channels were demonstrated by the decrease in the phosphate and ammonia content of the water, and its increased alkalinity and conductivity. The responses of aquatic vegetation to river incision depended on the vegetation zone investigated. Two floristic zones that were frequently flooded and species‐poor in 1989 remained species‐poor in 1993. Two floristic zones, which were species‐rich and patchily organized, became dry or very shallow in 1993; as a consequence, aquatic vegetation disappeared, and was replaced by helophytes and terrestrial species. In the last vegetation zone, the increase in the amount of water coming from the hillslope aquifer caused the appearance and development of Chara hispida, an oligotraphent species. Unforeseen impacts of river incision were a decrease in the spatial and temporal heterogeneity of the former channels and lower aquatic macrophyte richness.

Principal determinants of aquatic macrophyte richness in northern European lakes

Determinants of macrophyte species richness were evaluated using data from 641 lakes in Norway, Sweden, Denmark and Finland. The species pool of aquatic macrophytes was carefully delineated prior to establishing the recorded number of species ( S) for any lake. The expected richness E[S∣ X ] for a vector of environmental variables, X, related to lake area, altitude, trophic state and several water quality variables. Neither the size of the regional species pool nor the latitude affected S appreciably. Area ( A) contributed most to explain variation in species richness. E[ S∣ A] could be modelled by a Weibull-type curve. The power function employed by the theory of island biogeography is a limiting case of the Weibull model. Residual analysis identified factors which either increased or decreased species richness. A number of cases of low species richness and low floral diversity related to lake regulation, low pH or hypertrophication. Elevated species richness occurred preferably within quite small, often mesotrophic lakes which had undergone lowering of their surface levels. Lakes exhibiting a highly assorted macrophyte flora often experience intermediate disturbance and stress from moderate alterations of their water levels (1–3 m year −1). Overall, meso-eutrophic lakes supported higher species richness than did either oligotrophic or highly eutrophic lakes.

Biomass and species richness of aquatic macrophytes in four Maine (U.S.A.) lakes of different acidity

Macrophyte communities of 2 pairs of oligotrophic head-water lakes of different acidity were described. The acidic lakes had fewer species of macrophytes than the circumneutral lakes. Biomass in the circumneutral lakes ranged from 14.0 to 157.86 g m −2; values for the acidic lakes were intermediate (33.8 and 74.6 g m −2).

Comparison of Species Composition and Richness of Fish Assemblages in Altered and Unaltered Littoral Habitats

ABSTRACT Species composition and richness of fish assemblages in altered and unaltered littoral habitats in Lake St. Clair, Michigan, differed between areas. A percid-cyprinid-cyprinodontid assemblage dominated in the unaltered area, Muscamoot Bay, which has a natural shoreline (with almost no alteration due to dredging or bulkheading), high water quality, and high species richness of aquatic macrophytes. A centrarchid assemblage dominated in the altered area, Belvidere Bay, which has a bulkheaded shoreline, many dredged areas, reduced water quality due to inputs of nutrients from a nearby river, and relatively low species richness of aquatic macrophytes. Habitat factors, species richness and abundance of aquatic macrophytes, had the most influence on fish community structure in both areas. The percid-cyprinid-cyprinodontid assemblage was significantly correlated with six species of macrophytes whereas the centrarchid assemblage was significantly correlated with only four. These patterns suggested that pr...