Browsing All Posts filed under »plankton«

Triggers for algal blooms: peak temperatures aren’t always important

July 5, 2018

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There are concerns that human impacts  on freshwater systems – particularly temperature increases linked to climate change and nutrient enrichment caused by run-off and pollution – are encouraging the spread of blue-green algae (cyanobacteria) capable of generating toxic blooms that threaten human and animal health.  One such case is the recent spread of Cylindrospermopsis raciborskii, […]

Helping to resolve the plankton paradox

March 26, 2018

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The richness of plant plankton communities in natural ponds and small lakes is very high – typically up to about 80 species at any one time in most systems. However, ecological theory predicts that the number of coexisting species should be no greater than the number of limiting resources, and normally in the case of […]

Aquatic plants help animal plankton to disperse

March 25, 2018

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Freshwater bodies containing aquatic plants generally support a wide range of animal plankton. If the dormant stages of zooplankton are attached to roots and the submerged parts of plants, the dislodgement and displacement of aquatic vegetation during floods could play a role in plankton dispersal. To assess this possibility, Argentinian researchers collected specimens of free-floating […]

Once more from the top

December 21, 2017

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Top-down trophic cascades are population-level effects transmitted along food chains, from consumers down to primary producers.  In a typical three-level food chain the loss of top predators (for example, as a result of human exploitation) allows herbivore populations to increase, which in turn reduces populations of algae or higher plants.   However, few studies have considered […]

Ironing out harmful algal blooms

September 25, 2017

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An understanding of how iron affects the supply of nutrients in aquatic systems may open the door to better success in managing harmful algal blooms. In highly productive lakes, the release of phosphorus stored in the bottom sediment can encourage bloom development, but nutrient release is retarded in the presence of iron, which precipitates phosphorus […]

How cell size affects algal chemicals

September 25, 2017

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The chemical composition of microalgae – organisms such as green algae, diatoms and dinoflagellates – influences their food web interactions and the way they compete for nutrients, as well as their suitability for human exploitation in the form of biofuels, nutraceuticals and aquaculture feeds.   Because microalgae cover a wide range of cell sizes (less than […]

Plankton migration is system-dependent

June 19, 2017

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Lake zooplankton commonly switch microhabitats on a regular day-night basis by migrating horizontally between stands of vegetation and open waters, or by migrating vertically between deep and surface waters. These movements have been explained in terms of the need to avoid predators (especially fish) and excessive ultraviolet radiation.  However, although zooplankton are known to seek […]