Blooms of harmful cyanobacteria (also known as bluegreen algae) are a growing nuisance in many lakes in Africa, Australia, China, the USA, and in many European waters. Professor Hans Paerl of the University of North Carolina (USA) and professor Jef Huisman of the University of Amsterdam (Netherlands) conclude on the basis of several recent studies that the worldwide proliferation of harmful cyanobacterial blooms is linked to climate change.
Cyanobacteria flourish at high temperatures, especially in nutrient-rich waters with high concentrations of nitrogen and phosphorus. The surface water of lakes is heated during prolonged periods of warm weather. Warm water expands, and floats on the colder water underneath. This results in stratification of lake water, which suppresses vertical mixing. Cyanobacteria profit from these stratified conditions.
They make small gas vesicles inside their cells, providing buoyancy. Buoyant cycanobacteria float upwards when vertical mixing is weak and accumulate in dense surface blooms. These surface blooms shade underlying nonbuoyant phytoplankton (such as green algae and diatoms). Thus, surface blooms of buoyant cyanobacteria effectively suppress other species by monopolizing all available light.
Changes in precipitation patterns and summer droughts
Cyanobacteria also profit from changes in precipitation patterns and summer droughts. Climate models predict more intense precipitation interspersed by longer periods of drought as a result of global warming. Intense precipitation leaches nutrients from soils, flushing them into rivers and lakes. As the discharge subsides during subsequent periods of warm, dry weather, cyanobacteria can capture the extra nutrient load, promoting their bloom development.
Attempts to control the water table by closure of dams and sluices during summer droughts may further aggrevate the problem. This will increase the residence time of cyanobacteria in these stagnant waters, thus providing a longer time window for bloom development. Moreover, cyanobacteria appear to be more salt-tolerant than other freshwater algal species. Rising salinities due to increased evaporation or salt water intrusion from sea level rise may thus give cyanobacteria an additional competitive advantage.
Paerl and Huisman discuss the example of a tropical cyanobacterium responsible for a severe outbreak of hepatitis on Palm Eiland, Australia. This tropical species invaded southern Europe in the 1930s, and has subsequently expanded its range northwards to lakes in the Netherlands and Northern Germany. Likewise, the species also invaded Florida several decades ago, and is now widespread across the US southeast and midwest, where it proliferates in warm and nutrient-rich waters. ‘Water managers will have to anticipate a worldwide expansion of harmful cyanobacteria’, says Huisman. ‘This is another important reason to curb the emission of greenhouse gases’.
Cyanobacteria can produce a variety of different toxins, causing damage to the liver and nervous system of birds and mammals in particular. Ingestion of these toxins can be fatal to cattle, waterfowl, and pets, and is also a serious threat for human health. Bodies of waters are closed for recreation and agricultural use, when their concentrations of cyanobacteria exceed a critical threshold level.
Josje Spinhoven | alfa
Joint research project on wastewater for reuse examines pond system in Namibia
19.12.2016 | Technische Universität Darmstadt
Scientists produce a new roadmap for guiding development & conservation in the Amazon
09.12.2016 | Wildlife Conservation Society
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
18.01.2017 | Life Sciences
18.01.2017 | Health and Medicine
17.01.2017 | Earth Sciences