Forms and distribution of inorganic phosphorus in sediments of two shallow eutrophic lakes in Florida

Physicochemical attributes were measured and aquatic macroinvertebrates were collected from six wetlands near Perth, Western Australia at three weekly intervals over a 13 month period from August 1988 to September 1989. The six wetlands encompassed a range of depths, pH, concuctivities, nutrient concentrations and colours. Temporal changes in the macroinvertebrate communities appeared to be related to seasonal changes in the physical and chemical characteristics of the wetlands. Community composition differed more between the less enriched wetlands then the higly enriched wetlands where communities were generally similar. High species richness was associated with seasonal drying. High macro invertebrate abundance appeared to be associated with the presence of either green algal or cyanobacterial blooms in the enriched wetlands. The highest macroinvertebrate biomass was recorded in wetlands with both cyanobacterial blooms and abundant macrophytes present.     

Ethnopharmacological practices by livestock farmers in Uganda: Survey experiences from Mpigi and Gulu districts

Background

There is continued reliance on conventional veterinary drugs including anthelmintics, to some of which resistance has developed. Loss of indigenous technical knowledge (ITK) from societies affects the opportunities for utilization of ethnopharmacological practices unless properly documented. This study was conducted to identify common traditional practices using medicinal plants against helminthosis and other livestock diseases in Mpigi and Gulu districts of Uganda.

Methods

Seven focus group discussions with ten farmers per group plus 18 key informant interviews were held in each district from August to November 2011. Ranking was used to quantify disease burdens and to identify priority livestock and breeds. Samples of each plant were submitted to Makerere University herbarium for identification and documentation. The local name, relative availability and International Union for Conservation of Nature (IUCN) status were recorded.

Results

Seventy six farmers in Mpigi and 74 in Gulu were interviewed. Theileriosis and helminthosis were the most common disease conditions in cattle and goats, respectively. Forty plant species within 34 genera from 22 botanical families were identified, with 20 of these used against helminthosis. Other plants treated wounds and ecto-parasites, theileriosis, retained placenta and bovine ephemeral fever. Non-plant practices (7) and plants cited were used in combination depending on availability. Males older than 40 years had most ethnopharmacological knowledge. Most plants (75%, n?=?40) were common, but 10 were rare. IUCN status was not evaluated for 95% of these plants. Conventional and traditional drug use in Gulu and Mpigi districts was different (χ²?=?24; p?<?0.001). The scientific, English, Luganda and Acholi names of all plants and their availability within the communities are documented herein.

Conclusion

This is the first detailed livestock-related ethnopharmacological study in Gulu district. Farmers in Uganda are still using a variety of practices to treat livestock ailments. Scientific validation and evaluation of conservation status are urgently needed to ensure future availability and knowledge about these plant resources.     

Influence of redox potential on phosphate-uptake by sediments in two sub-tropical eutrophic lakes

Biogeochemical reactions in shallow eutrophic lakes areaffected bythe changes in redox potential (Eh) as bottom sedimentsundergotemporal resuspension and settling. The stability of varioussediment P fractions and kinetics of P-uptake were evaluatedfortwo sub-tropical lakes (Lake Apopka and Lake Okeechobee,Florida)using sediment suspensions in closed systems maintained atvariousEh levels ranging from –235 to 555 mV. Redox potential hadminimal effect on the stability of NaOH-P (Fe-/Al-bound P plusmoderately resistant organic P) and HCl-P (Ca-/Mg-P) fractionsinLake Apopka sediments. Increases in ortho-P and NH₄Cl-P(loosely-bound P plus labile organic P) concentrations wereobserved in highly reduced (Eh=–225 mV) Apopkasediments.Phosphate solubility diagrams and mineral equilibriacalculationssuggest that P-uptake by Apopka bottom sediments at elevated Pconcentrations (ortho-P110 M) was due toformationof Ca-P compounds and/or co-precipitation of P withCaCO₃. Incontrast, the ortho-P concentrations for Lake Okeechobeebottomsediments increased exponentially with decreasing Eh. Thequantityof NaOH-P fractions for these sediments decreased withdecreasingEh, suggesting the release of Fe- and Mn-bound P intosolution.Phosphate-uptake by Okeechobee bottom sediments (pH 7.5,ambient)followed first order kinetics, yielding a rate constant (k)of 0.51±0.05 h^-1. Unlike that of Apopka, the mudsediments in Lake Okeechobee have strong affinity for P ineitheraerobic or anaerobic conditions. Results suggest that even incalcareous systems, Fe and Al, when present in highconcentrations(as in the case of Lake Okeechobee), are actively involved inregulating P-uptake and geochemistry.     

Influence of draining on soil phosphorus forms and distribution in a constructed wetland

Seasonal water-table fluctuations in wetlands can result in flooded and drained conditions in the surface soil. In constructed wetlands water level drawdown and soil drainage are used in management to consolidate detrital materials, accelerate soil build up, and provide easy access for other management operations. A greenhouse study was conducted using intact peat soil cores to evaluate the changes in bioavailable P and other fractions following draining and reflooding. Measurements of floodwater dissolved reactive P (DRP) indicated that draining and soil exposure could result in large P flux to the overlying water column. Phosphorus flux in soils drained for 6 weeks was 10-fold higher (334 mg P m⁻² day⁻¹) than in soils drained for 3 weeks (33 mg P m⁻² day⁻¹). Soil exposure also resulted in an increase in bioavailable inorganic P (estimated by KCl extraction) at the expense of labile organic P pool. The KCl-P pool, which was initially less than 2% of total P (TP), increased to 3% and 13% of TP after 3 and 6 weeks draining, respectively. Results suggest that various soil P fractions, particularly those in newly accreted materials, were highly unstable and could be released in a more available form when newly accreted soils undergo drying. Water level drawdown and reflooding could result in significant P release, a possible stimulation of algal blooms and other water quality problems. Therefore, soil characteristics and chemistry and their impact on water quality should be a major consideration when one adopts the flood-drain technique in wetland management.