Freshwater blooms of phytoplankton affect public health and ecosystem services globally1,2. Harmful effects of such blooms occur when the intensity of a bloom is too high, or when toxin-producing phytoplankton species are present. Freshwater blooms result in economic losses of more than US$4 billion annually in the United States alone, primarily from harm to aquatic food production, recreation and tourism, and drinking-water supplies3. Studies that document bloom conditions in lakes have either focused only on individual or regional subsets of lakes4–6, or have been limited by a lack of long-term observations7–9. Here we use three decades of high-resolution Landsat 5 satellite imagery to investigate long-term trends in intense summertime near-surface phytoplankton blooms for 71 large lakes globally. We find that peak summertime bloom intensity has increased in most (68 per cent) of the lakes studied, revealing a global exacerbation of bloom conditions. Lakes that have experienced a significant (P < 0.1) decrease in bloom intensity are rare (8 per cent). The reason behind the increase in phytoplankton bloom intensity remains unclear, however, as temporal trends do not track consistently with temperature, precipitation, fertilizer-use trends or other previously hypothesized drivers. We do find, however, that lakes with a decrease in bloom intensity warmed less compared to other lakes, suggesting that lake warming may already be counteracting management efforts to ameliorate eutrophication10,11. Our findings support calls for water quality management efforts to better account for the interactions between climate change and local hydrological conditions12,13. Analyses show that the peak intensity of summertime phytoplankton blooms has increased in 71 large lakes globally over the past three decades, revealing a worldwide exacerbation of bloom conditions.

Widespread global increase in intense lake phytoplankton blooms since the 1980s

Use of water quality indices to verify the impact of Córdoba City (Argentina) on Suquía River.

The usefulness of water quality indices, as the indicators of water pollution, for assessment of spatial-temporal changes and classification of river water qualities was verified. Four water quality indices were investigated: WQI (considering 18 water quality parameters), WQI(min) and WQI(m) (considering five water quality parameters: temperature, pH, DO, EC and TSS) and WQI(DO) (considering a single parameter, DO). The water quality indices WQI(min), WQI(m) and WQI(DO) could be of particular interest for the developing countries because of the minimum analytical cost involved. As a case study, water quality indices were used to evaluate spatial and temporal changes of the water quality in the Bagmati river basin (Nepal) for the study period 1999-2003. The results allowed us to determine the serious negative effects of the city urban activity on the river water quality. In the studied section of the river, the water quality index (WQI) was 71 units (classified as good) at the entry station and 47.6 units (classified as bad) at the outlet station. For the studied period, a significant decrease in water quality (mean WQI decrease = 11.6%, p = 0.042) was observed in the rural areas. A comparative analysis revealed that the urban water quality was significantly bad as compared with rural. The analysis enabled to classify the water quality stations into three groups: good water quality, medium water quality and bad water quality. WQI(min) resulted in overestimation of the water quality but with similar trend as with WQI and is useful for the periodic routine monitoring program. The correlation of WQI with WQI(min) and DO resulted two new indices WQI(m) and WQI(DO), respectively. The classification of waters based on WQI(m) and WQI(DO) coincided in 90 and 93% of the samples, respectively.

Application of water quality indices and dissolved oxygen as indicators for river water classification and urban impact assessment.

Constructed wetlands for pollution control: Processes, performance, design and operation

A review of currently available in-stream water-quality models and their applicability for simulating dissolved oxygen in lowland rivers.

River water quality modelling: I. state of the art

River Water Quality Modelling: III. Future of the Art

(2002). Trend and noise: long-term changes of phytoplankton in the Keszthely Basin of Lake Balaton, Hungary. SIL Proceedings, 1922-2010: Vol. 28, No. 1, pp. 194-203.

/pdf/trend-and-noise-long-term-changes-of-phytoplankton-in-the-b4rdgxjhw6.pdf

Trend and noise: long-term changes of phytoplankton in the Keszthely Basin of Lake Balaton, Hungary

From simple to complex – Comparing four modelling tools for quantifying hydrologic ecosystem services

As one of the major measures for controlling the man-made eutrophication of Lake Balaton, the Hidveg reservoir of 20 km2 surface area was built near the mouth of River Zala, draining half the watershed of the lake, and representing the largest nutrient source for the lake. The reservoir, as the first element of the expected total system of 70 km2 surface area (Kis-Balaton Control System), started to operate in June 1985, aiming at removing nutrients primarily through sedimentation, adsorption and uptake by macrophytes.

Operation of the Kis-Balaton reservoir: evaluation of nutrient removal rates

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