MY ABSTRACT

Chinese Science Bulletin, 2006

Traditionally, nitrogen control is generally considered an important component of reducing lake eutrophication and cyanobacteria blooms. However, this viewpoint is refuted recently by researchers in China and North America. In the present paper, the traditional viewpoint of nitrogen control is pointed out to lack a scientific basis: the N/P hypothesis is just a subjective assumption; bottle bioassay experiments fail to simulate the natural process of nitrogen fixation. Our multi-year comparative research in more than 40 Yangtze lakes indicates that phosphorus is the key factor determining phytoplankton growth regardless of nitrogen concentrations and that total phytoplankton biomass is determined by total phosphorus and not by total nitrogen concentrations. These results imply that, in the field, nitrogen control will not decrease phytoplankton biomass. This finding is supported by a long-term whole-lake experiment from North America. These outcomes can be generalized in terms that a reduction in nitrogen loading may not decrease the biomass of total phytoplankton as it can stimulate blooms of nitrogen-fixing cyanobacteria. To mitigate eutrophication, it is not nitrogen but phosphorus that should be reduced, unless nitrogen concentrations are too high to induce direct toxic impacts on human beings or other organisms. Finally, details are provided on how to reduce controls on nitrogen and how to mitigate eutrophication.

The Environmentalist, 2008

Environmental science & technology, 2016

As human populations increase and land-use intensifies, toxic and unsightly nuisance blooms of blue-green algae (Cyanobacteria) are becoming larger and more frequent in freshwater lakes. In the past half century, aquatic scientists have devoted much effort to understanding the causes of such blooms and how they can be prevented or reduced. Here we review the evidence, finding that numerous long-term studies of lake ecosystems in Europe and North America show that controlling algal blooms and other symptoms of eutrophication depends on reducing inputs of a single nutrient: phosphorus. In contrast, small-scale experiments of short duration, where nutrients are added rather than removed, often give spurious and confusing results that bear little relevance to solving the problem of cyanobacteria blooms in lakes.

Environmental Science & Technology, 1995

Hydrobiologia, 1990

No recovery was recorded in the shallow and eutrophic Lake Væng, Denmark, after a sewage diversion in 1981, due to an internal phosphorus loading and a dominance of planktivorous fish. In order to improve lake water quality by means of biomanipulation, a total of 2.5 tons of bream (Abramis brama) and roach (Rutilus rutilus) was removed during 1986 and the spring of 1987. The planktivorous/benthivorous fish biomass was thereby reduced by approximately 50%, from 30 to 15 g WW m−2. After the reduction, the biological structure of the lake changed markedly. The zooplankton community changed from a dominance of rotifers before the fish reduction to larger cladocerans afterwards. Zooplankton mean summer biomass increased from 0.4 mg DW l−1 in 1986 to 2.7 mg DW l−1 in 1987 and to 1.3 mg DW l−1 in 1988. Phytoplankton biomass decreased from a mean summer level of 25 mm3 l−1 in 1986 to 12 in 1987 and to 7 mm3 l−1 in 1988. Qualitatively, the phytoplankton changed from a dominance of cyanobacteria and small diatoms to a dominance of larger diatoms, larger greens and cryptophytes. Secchi depth increased from a mean summer level of 0.6 m in 1986 to 1.0 m in 1987 and 1.3 m in 1988. After the fish removal, the internal phosphorus loading was reduced markedly. This reduction is considered primarily to be caused by the improved redox conditions in the sediment due to reduced sedimentation, and by the increased micro-benthic primary production and phosphorus uptake. Submerged macrophytes, mainlyPotamogeton crispus andElodea canadensis, increased in abundance due to improved light climate at the lake bottom.

Journal of Applied Sciences and Environmental Management, 2004

Water

Maejo International Journal of Energy and Environmental Communication (MIJEEC), 2019