Browsing All Posts filed under »predation«

Lake management: are tipping points real?

December 14, 2021

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Freshwater biologists often seek to restore turbid shallow lakes dominated by phytoplankton to clear-water systems with a high abundance of submerged plants.  The usual plan of operation, which is often guided by lake ecosystem modelling, is to reduce external inputs of nutrients (e.g., from agricultural runoff or urban waste streams) to a threshold level at […]

How flowing water affects the schooling of fish

September 28, 2021

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In many species of fish, individuals group together in shoals or schools to benefit from shared information – for example, on food availability or the presence of predators.  There’s also evidence that fish gain hydrodynamic benefits by taking up certain positions relative to other individuals, but not much is known about how flowing water affects […]

Assessing plankton communities: coarse classification works well

March 13, 2021

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Information on the responses of ecological communities to environmental factors plays a significant role in the management of natural resources.  However, assessing the responses of some important groups, such as lake plankton, is often difficult because of a lack of taxonomic expertise.  A possible solution to this problem is to classify organisms by functional physiological, […]

Water abstraction changes local food chains

March 13, 2021

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The alteration of river flows by damming or extracting water is a major threat to freshwater ecosystems that can lead to habitat changes and local species extinctions.  While the impacts of dams and large-scale diversions have been the subject of many studies, the cumulative effects of small water abstractions aren’t so well understood, even though […]

Ecosystem impacts of invasive carp

December 16, 2020

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The common carp (Cyprinus carpio) is one of the world’s most widespread invasive fish species and has a reputation for causing ecological damage.  It’s thought that the excretion of nutrients by dense populations of carp stimulates algal growth, which increases turbidity, and that the feeding and spawning activities of carp further increase turbidity by bringing […]

Are there more species in permanent waters?

December 16, 2020

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How important is the influence of permanent water on the biodiversity of lakes, ponds and wetlands? Because many freshwater habitats dry out on a regular basis, to survive under such conditions organisms need to be able to exist as terrestrial adults or dormant stages, or to migrate to more permanent water bodies.  Despite these challenges, […]

Functional feeding groups: beware of misleading assumptions

September 26, 2020

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Food webs are central to the functioning of aquatic ecosystems, and are commonly reconstructed by assigning each taxon (usually a species, genus or family) to a particular functional feeding group by reference to published information.  In the case of freshwater macroinvertebrates, the main feeding groups are: shredders, which chew on coarse organic particles; collector–filterers, which […]

A clever way to rebalance a lake

September 26, 2020

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Lakes are often subject to high-nutrient  inflows from agricultural runoff, industry and wastewater treatment, and these inputs lead to algal blooms, reduced biodiversity and a shift from clear to turbid water.  Such lakes can be remediated by reducing nutrient loads or by biomanipulation, where fish are selectively removed to lower predation pressure on zooplankton, which […]

Freshwater food webs: don’t forget parasites

September 26, 2020

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Although parasites are the dominant components in aquatic ecosystems, they are rarely considered in food web studies.  This can be a mistake, because parasites with free-living stages are taken as prey by predators, and when parasites swap hosts they carry nutrients from one host to the next.  It’s been found that adding parasites to reconstructed […]

What drives plankton migration?

September 26, 2020

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In lakes and oceanic waters, planktonic animals migrate upwards at night to feed on phytoplankton near the surface, and migrate downwards by day to deeper darker layers to avoid visually-feeding fish predators.  These migrations have significant consequences for nutrient transport and aquatic food webs.  Food availability, light intensity and chemicals released by predatory fish are […]