An assessment of the importance of emergent and floating-leaved macrophytes to trophic status in the Loosdrecht lakes (The Netherlands)

The potential importance of the six major emergent and floating-leaved macrophyte species in recycling of sediment phosphorus in the Loosdrecht lakes was studied. Representative plant samples were collected at the time of maximum biomass, and analysed for biomass and carbon, nitrogen and phosphorus contents. Species cover was determined by aerial photography.Total cover in the seven lakes studied ranged between 2 and 26 percent. For the four main species, biomass per unit area increased with lake trophic status. Consistent differences in C, N and P contents per unit biomass were not observed. Although cover values were small, significant amounts of C, N and P were contained in the macrophytes when compared with maximum sestonic content.Potential P loads from macrophyte decay were calculated. In Lake Loosdrecht, the P load represented 15 percent of current external P inputs. The potential importance of macrophyte decay to P recycling in the other lakes is greater.Decay of macrophyte species at the end of the growing season appears to affect autumnal nutrient and chlorophyll a levels in the water column of some lakes. The re-establishment of submerged species following lake restoration may increase the importance of this pathway in the lakes.     

The impact of an industrially contaminated lake on heavy metal levels in its effluent stream

Levels of cadmium and zinc in various components of Williamson Ditch (an industrially contaminated stream flowing into Palestine Lake), Trimble Creek (a stream draining Palestine Lake) and the Tippecance River (a river receiving Trimble Creek) were determined. Water, sediment, plant, fish and clam samples were analyzed for cadmium and zinc content by atomic absorption spectrophotometry. Unweighted mean metal concentrations in Trimble Creek were the following: water, 51 µg Zn/1 and 4.2 µg Cd/1; sediment, 592 µg Zn/g and 48.8,µg Cd/g; plants, 375 µm Zn/g and 7.91 µg Cd/g; fish, 145 µg Zn/g and 6.02 µg Cd/g. These concentrations were generally lower than those found in Williamson Ditch and higher than those found in the Tippecanoe River or background levels previously reported for other aquatic ecosystems.     

Distribution and movement of toxaphene in anaerobic saline marsh soils

The biological oxygen demand (BOD) of filtered water from Lake Wingra, Wisconsin is significantly higher in the littoral zone than in the pelagial zone. Laboratory experiments indicate that BOD is not influenced by water temperature at the time of sampling or by enrichment with nitrate or ammonia. Rather, enrichment with macrophyte leachate sharply increases BOD, and enrichment with phosphate produces a small but significant increase in BOD. We conclude that high BOD in littoral waters of the lake is an indication of production of labile organic matter in the water by dense beds of the macrophyte Myriophyllum spicatum.     

Farm pond restoration using Chara vulgaris vegetation

Four aged Madison County, New York farm ponds were selected to see if various treatments could be used to restore the water quality. One pond was untreated and used as a control; another pond was partially drained and exposed to the drying and oxidizing effects of the air over the fall and winter; the other two ponds were drained and the accumulated sediment removed by bulldozing. In these latter two ponds, Chara vulgaris vegetation was inoculated following the restoration process. C. vulgaris growth rapidly became the dominant producer where this inoculation was accomplished in the fall of 1976, and it is expected that the other pond will also become a C. vulgaris pond in 1978 — after its oogonia have undergone the requisite winter dormancy period.Early C. vulgaris growth was found to be associated with clear water conditions and lessened phytoplankton growth; short, bushy, light-inhibited growth by the algae stabilized the bottom against wind-caused turbidity because of its rhizoidal growth within the substrate. Pioneer C. vulgaris growth was also found to be highly productive, significantly lowering the pond's CO₂ readings.Investigators of aquatic systems are cautioned to be cognizant of the effect of epiphytic growth on successional events in such environments. Such epiphytes are surely important, if not prime, causes of the demise of various aquatic macrophytes.The partial draining and exposing of a pond over the fall and winter did not yield significantly improved water conditions.     

Production of submerged aquatic plant communities of Doodhadhari lake Raipur, (M.P. India)

The biomass of submerged aquatic plant communities was studied periodically during two annual growth periods. Najas minor contributed 78% to the total standing biomass. Ceratophyllum demersum, Hydrilla, Nelumbo nucifera, Trapa bispinosa and Potamogeton crispus contributed towards the rest of the biomass. The production was 0.64 g./m.²/day for the growing seasons of one year.     

Investigations of the aufwuchs of freshwater sponges. I. A quantitative comparison between the surfaces of Spongilla Lacustris and three aquatic macrophytes

The aufwuchs of the epithelium of the freshwater sponge Spongilla lacustris was examined and compared qualitatively and quantitatively with that on three plant substrates common to its habitat: Nymphea odorata, Nuphar advena and Utricularia spp. Estimations of the percentage surface area with attached forms and the number of attached green algal filaments yielded significantly lower values for the sponge. Two theories explaining the mechanism effecting this reduced amount of aufwuchs are discussed.     

Modeling nutrients,oxygen and critical phosphorus loading in a shallow reservoir in China with a coupled water quality – Macrophytes model

Many macrophyte-dominated clear lakes switch to a phytoplankton-dominated turbid state when the lake becomes eutrophic. An existing Yuqiao Reservoir Water Quality Model (YRWQM) and the macrophyte submodel were coupled to simulate the effect of submerged macrophytes on nutrients and dissolve oxygen cycles in a shallow reservoir in China. The level of phosphorus loading in a transition from a clear to turbid state was addressed using the integrated model. The model runs from seedling establishment until dying out, from March 1 to July 18 in 2009. The simulations were performed for a contingent range of P loadings, starting from three different initial conditions. The results indicated that the integrated model improves accuracy of predictions compared to YRWQM. The concentrations of nutrients declined slightly during the macrophyte growth period in the reservoir and dissolved oxygen increased slightly. Although nutrient concentrations increased by submerged macrophyte release during the extinction period, the effect on the nutrients was less than that of transfer with nutrient-rich water. More released nutrients may enhance increases in substantial abundance. The critical phosphorus loading level during a switch from the clear to turbid state was estimated by these scenarios. The threshold for the switch is ∼6.1 mgP m⁻² d⁻¹ with an initial total phosphorus concentration of 160 μg l⁻¹. Moreover, the results demonstrated that the switch was also dependent on the initial total phosphorus concentration. These results suggest that the reservoir in a clear water state is at risk of a switch as nutrient levels are close to the critical levels.     

The development and persistence of alternative ecosystem states in a large,shallow lake

1. Palaeolimnological data were used to investigate drivers of the community of primary producers in Lake Mattamuskeet, North Carolina, U.S.A. This is a large, shallow lake with two basins currently dominated by phytoplankton and macrophytes. The two basins were divided in 1940 by the building of a roadway across the lake, which also corresponded with the divergence in their ecosystem state. 2. Photosynthetic pigments, organic matter and nutrients (P, N, C, S) were analysed in sediment cores from each basin to reconstruct the primary producer community over the past c. 100 years. We sought to answer two questions. First, what changes to the ecosystem resulting from the building of the roadway caused the development of different primary producer communities in the two basins? Second, why have the alternative ecosystem states persisted despite a variety of human perturbations since 1940? 3. K‐means cluster analysis and principal component analysis were applied to identify three sediment types based on photosynthetic pigment data: sediments indicating low productivity (low pigment concentrations), sediments associated with macrophytes (chlorophyll a and b) and with phytoplankton (alloxanthin and aphanizophyll). In addition, other palaeolimnological proxies measured, such as loss on ignition, total phosphorus, total organic carbon/total nitrogen and other nutrients, were different in post‐1940 sediments within the two basins. 4. These differences suggest characteristics, such as nutrient cycling, water depth and other physical changes resulting from roadway construction, combined to establish and maintain the differing communities of primary producers in the two basins. Furthermore, Fe/S dynamics and waterfowl herbivory probably contributed to the development of the two ecosystem states.     

Rendiconti Delle Sedute E Brevi Comunicazioni

Abstract

The development of effective strategies to rehabilitate compromised environments is one of the major challenges facing the postindustrial society, since most of the habitats are becoming progressively polluted due to indiscriminate discharge of contaminants generated by anthropogenic activities. Several aquatic photosynthetic organisms can be used to treat wastewaters in primary and tertiary treatments, including cyanobacteria, algae and higher plants. In this review, we summarize the results obtained in the remediation of polluted waters by photosynthetic organisms and discuss the future perspective of phytoremediation.     

Free-Radical Scavenging Activity of Submerged Mycelium Extracts from Higher Basidiomycetes Mushrooms

Twenty-four Basidiomycetes strains were evaluated to determine their free-radical scavenging capacity in submerged cultivation. The scavenging capacity of the extracts varied from 1 to 85% depending on the mushroom species, solvent used, and concentration. A calculation of EC₅₀ of extracts from several wood-rotting Basidiomycetes showed high scavenging abilities at low effective concentration.