Search results for "Food web"
showing 10 items of 181 documents
Biogenic methane contributes to the food web of a large, shallow lake
2013
Summary Biogenic methane as an alternative carbon and energy source for freshwater organisms has been receiving increasing attention, but the phenomenon is still poorly understood for shallow lakes. We measured the carbon and nitrogen stable isotope signatures (δ13C, δ15N) for key groups of pelagic and benthic organisms, including crustacean zooplankton, chironomid larvae, young-of-the-year and adult fish, to assess whether biogenic methane contributes to pelagic and benthic food webs in a large, shallow lake, Lake Vortsjarv, Estonia. In the southern part of the lake, covered by macrophytes, crustacean zooplankton showed strong seasonal variation of δ13C, with the lowest values occurring in…
Responses of decomposer community to root-isolation and addition of slash
2001
Abstract We studied the causal relationships between forest harvesting and the soil decomposer community focusing on suppression of energy inputs from trees to the soil through root–mycorrhizal network and increased energy input to the soil in the form of slash left on site. We hypothesised that both of these factors would affect the decomposer community, since the soil food web has been regarded as a system in which the amount of resources controls the numbers of consumers. To study the importance of these factors without changes in microclimate, like in sunshine and shade, taking place in clear-felled areas, the experiment was performed in a mature spruce ( Picea abies (L.) Karst.) forest…
Functional diversity of decomposer organisms in relation to primary production
1998
Abstract The term `biodiversity' is claimed to lack connections to a serious scientific background. In this work, we approached the concept of biodiversity from a functional point of view by asking: “At what level of the ecological organization (species, trophic species/feeding guilds, trophic levels etc.) should reduction in biodiversity matter to bring about visible changes in ecosystem performance?” We investigate the concepts of `functional diversity' and `ecosystem performance' in relation to feeding habits (such as fungivory, detritivory etc.) of soil fauna and plant growth. After analysing the results of a number of microcosm studies, we came into the following conclusions: (i) troph…
Responses of microbial food web to increased allochthonous DOM in an oligotrophic subarctic lake
2013
Climate-induced changes in catchment area vegetation and runoff alter the quality and quantity of carbon that enters lakes, with implications for food webs in recipient water bodies. The effect of dissolved organic matter (DOM) on the ratio between heterotrophic and autotrophic biomass and productivity was studied in a subarctic, clear water lake in northern Finland. In a mesocosm experiment, natural DOM from a subarctic bog and a boreal lake was added to the lake water, doubling the initial dissolved organic carbon (DOC) concentration. Optical indices sug- gested that the subarctic DOM addition was more bioavailable, which was in line with the greater increase in bacterial biomass and prod…
Population- and ecosystem-level effects of predation on microbial-feeding nematodes.
2017
We studied the role of nematode predation in the functioning of detrital food webs assembled in microcosms. The microcosms contained defaunated humus and litter materials, a diverse microbial community with bacteria, fungi and protozoa, and a birch (Betula pendula) seedling infected with mycorrhizal fungi. Different levels of top-down control upon microbivorous nematodes were set up by assembling food webs either without predators, or in combinations with a specialist and a non-specialist predatory mite (Mesostigmata). The nematode community was composed of either (1) three species of bacterivorous, or (2) three species of fungivorous nematodes or (3) both groups together. After two growing…
A modified niche model for generating food webs with stage-structured consumers : The stabilizing effects of life-history stages on complex food webs
2021
1. Almost all organisms grow in size during their lifetime and switch diets, trophic positions, and interacting partners as they grow. Such ontogenetic development introduces life-history stages and flows of biomass between the stages through growth and reproduction. However, current research on complex food webs rarely considers life-history stages. The few previously proposed methods do not take full advantage of the existing food web structural models that can produce realistic food web topologies. 2. We extended the niche model by Williams & Martinez (2000) to generate food webs that included trophic species with a life-history stage structure. Our method aggregated trophic species …
Nitrate uptake rates in freshwater plankton: the effect of food web structure
2008
9 pages, 3 figure, 1 table
Italian marine reserve effectiveness: does enforcement matter?
2008
Marine protected areas (MPAs) have become popular tools worldwide for ecosystem conservation and fishery management. Fish assemblages can benefit from protection provided by MPAs, especially those that include fully no-take reserves. Fish response to protection can thus be used to evaluate the effectiveness of marine reserves. Most target fish are high-level predators and their overfishing may affect entire communities through trophic cascades. In the Mediterranean rocky sublittoral, marine reserves may allow fish predators of sea urchins to recover and thus whole communities to be restored from coralline barrens to macroalgae. Such direct and indirect reserve effects, however, are likely t…
The fate of organic matter sources in coastal environments: a comparison of three Mediterranean lagoons
2008
Trophic processes in coastal lagoons are strongly influenced by freshwater inputs and water exchanges with the sea. In recent years, stable isotope analysis has become a widespread and reliable method for the examination of trophic structure over time and space, also in complex ecosystems such as coastal lagoons. Stable isotopes of carbon and nitrogen were studied in primary producers and consumers to identify organic matter source pools from terrestrial, benthic and pelagic environments and to characterise the trophic structure in three Mediterranean coastal lagoons (Lake Fusaro, the Lake of Sabaudia and Stagnone di Marsala). The results highlighted the negligible importance of terrestrial…
Experimental Study on the Diet of Mosquitofish (Gambusia holbrooki) under Different Ecological Conditions in a Shallow Lake
2004
We studied the diet of the eastern mosquitofish Gambusia holbrooki with in situ experimental mesocosms located in a shallow lake. Different nutrient concentrations (phosphorus and nitrogen) and fish population densities were tested. Our results confirm that it is a planktivorous species, with also a great ingestion of algae and detritus. Nutrient fertilization caused almost no changes in this species feeding behavior, but larger mosquitofish stocks induced a shift to zooplanktivory and a decline in detritivory. When macrophytes were present, the predation effect focused on zooplankton and plant-associated animals, otherwise predation on bottom macroinvertebrates increased. Females preyed up…