Browsing All Posts filed under »lakes«

Predatory fish control prey populations – but not when the prey are other fish

September 25, 2017

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Many lake studies have shown that predatory fish feeding on plankton or bottom-living invertebrates have a strong influence on the density, species composition and size structure of prey populations. Typically, there’s an inverse relationship between predator and prey populations, both in terms of  density and in mean body size.  However, there have been few reports […]

Coarse, shallow and wooden… but useful nonetheless

June 19, 2017

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Coarse woody debris (CWD) derived from shoreline trees provides an important, spatially complex habitat and a food source for lake-dwelling organisms. Here are some interesting facts about lake CWD, taken from a recent review paper: In the absence of the physical action of flowing water, CWD breaks down more slowly in lakes than in streams. […]

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 […]

How the terrestrial landscape affects aquatic dispersal

June 19, 2017

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How does the surrounding terrestrial landscape affect the dispersal of pond-dwelling organisms? Although some studies suggest that small aquatic crustaceans can disperse efficiently across a range of intervening environments, other work has pointed to dispersal limitation, especially over large distances.  Czech researchers examined the passive dispersal of microcrustaceans (cladocerans, copepods, and ostracods) by comparing communities […]

Predators concentrate on current-concentrated prey

December 13, 2016

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In marine environments, recirculating eddies, upwellings and downwellings play an important role in concentrating plankton in small areas, a process that attracts predators such as fish, mammals and birds and boosts ecological productivity significantly above background levels. However, much less is known about the ways in which physical processes may concentrate organisms and intensify food-web […]

Low biodiversity in productive lakes

December 13, 2016

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The over-supply of nutrients to lakes (through pollution, for example) stimulates the growth of plant plankton, which blocks light from reaching bottom-dwelling algae and higher plants. Therefore, nutrient excess has the potential to reduce habitat diversity and the associated biodiversity of animal plankton, macroinvertebrates and fish. An international team of biologists looked at the relationship […]

Top predator boosts species richness – but not in alien ecosystems

December 13, 2016

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The spiny water flea Bythotrephes longimanus is a large cladoceran, a specialised carnivore and a top predator. Invasions of North American lakes by Bythotrephes have been linked to dramatic changes in food web structure and reductions in species diversity, which seems to contradict the expectation that top predators increase the evenness and diversity of aquatic […]