Search results for " Ecosystem"
showing 10 items of 633 documents
Spatial and temporal variation in denitrification and in the denitrifier community in a boreal lake
2011
We investigated the spatial and temporal variation in denitrification rates (isotopepairing technique, IPT) and in the denitrifier community (examination of gene nirK by denaturinggradient gel electrophoresis [DGGE] of microbial DNA) in the sediments of a boreal, clear-water, eutrophic lake using samples collected from shallow littoral, deep littoral and shallow profundal sediments during early summer, mid-summer, autumn and winter. The measured denitrification rates (44 to 613 μmol N m−2 d−1) are among the lowest ever reported from lacustrine sediments. Denitri fi cation rates varied both spatially and temporally, being highest in the profundal zone during midsummer and in the littoral zon…
Community Structure of Gastropods in Seagrass Meadows at Coastal Area of Nusi and Gersen, Nabire Regency
2020
Gastropods plays an important role in the food chain on seagrass ecosystem and its existence are depend on the physical-chemical factors in the seagrass ecosystem. This study aims to determine the density and diversity of gastropods associated in seagrass habitat in Nusi and Gersen coastal waters. The measurement results of some physical-chemical waters variables, are still quite good for the life of gastropods. Species composition of gastropod in Nusi at higher than at the Gersen, but instead of individual density in Gersen more higher than Nusi. Diversity index of gastropods at Nusi station is higher (3,757) than Gersen (3.053), on the contrary the eveness and dominance index are higher a…
Artificial dam lakes as suitable habitats for exotic invertebrates: Ostracoda ecology and distribution in reservoirs of the Eastern Iberian Peninsula
2014
Reservoirs are the most common deep lakes in Spain, as a consequence of water needs and dry climate. Although these aquatic systems can play an important ecological role in such an area with few large natural lakes, they can also provide new habitats for exotic species, which can colonize ecosystems that native species have not explored yet. Here we present our results for a biannual survey of the ostracod fauna from 24 reservoirs in Xuquer River basin. We check which variables affect ostracod presence, test for differences between winter and summer assemblages, and compare our data with previous available ostracod records from the same river drainage network. Our results reveal that ostrac…
Global distributions of diazotrophs abundance, biomass and nitrogen fixation rates - Gridded data product (NetCDF) - Contribution to the MAREDAT Worl…
2012
The MAREDAT atlas covers 11 types of plankton, ranging in size from bacteria to jellyfish. Together, these plankton groups determine the health and productivity of the global ocean and play a vital role in the global carbon cycle. Working within a uniform and consistent spatial and depth grid (map) of the global ocean, the researchers compiled thousands and tens of thousands of data points to identify regions of plankton abundance and scarcity as well as areas of data abundance and scarcity. At many of the grid points, the MAREDAT team accomplished the difficult conversion from abundance (numbers of organisms) to biomass (carbon mass of organisms). The MAREDAT atlas provides an unprecedente…
Optical types of inland and coastal waters
2017
Inland and coastal waterbodies are critical components of the global biosphere. Timely monitoring is necessary to enhance our understanding of their functions, the drivers impacting on these functions and to deliver more effective management. The ability to observe waterbodies from space has led to Earth observation (EO) becoming established as an important source of information on water quality and ecosystem condition. However, progress toward a globally valid EO approach is still largely hampered by inconsistences over temporally and spatially variable in-water optical conditions. In this study, a comprehensive dataset from more than 250 aquatic systems, representing a wide range of condi…
Shape and size in phytoplankton ecology: do they matter?
2007
This paper summarises the outcomes of the 14th Workshop of the International Association of Phytoplankton Taxonomy and Ecology (IAP). The authors mostly addressed their contributions on the following topics: morphological and morpho-functional descriptors of phytoplankton, size and shape structure of phytoplankton related to different kinds of environmental variables and the role of morphological and physiological plasticity of phytoplankton in maintaining the (apparently) same populations under different environmental conditions. Case studies from different kinds of aquatic environments (deep and shallow lakes, reservoirs with different age, purpose and trophic state, floodplain wetlands m…
Changes in community composition determine recovery trajectories from multiple agricultural stressors in freshwater ecosystems
2020
AbstractPesticides have been identified worldwide as a threat for aquatic biodiversity due to their widespread use in agriculture and their capacity to reach freshwater ecosystems. Very little is known about the consequences of pesticide mixtures targeting different organism groups on community dynamics. Especially, how horizontal changes within one trophic level are propagated vertically across the food web has been rarely investigated. To get insight on the effects of pesticide mixtures on community dynamics, we performed a mesocosm experiment manipulating three common agricultural stressors: chlorpyrifos (an insecticide), diuron (an herbicide) and nutrients. The results of this study sho…
River bioassessment and the preservation of threatened species: Towards acceptable biological quality criteria
2010
Abstract A central objective of environmental management is to maintain biodiversity, including populations of threatened species. Freshwater ecosystems are increasingly assessed by their biotic properties, but whether the resulting classifications of biotic condition are sufficient to protect species with conservation status has received very little consideration. We used data from 225 reference and impacted river sites from Finland to examine whether the occurrence and abundance of threatened macroinvertebrate species (TS) are associated with a commonly used estimate of biological condition (Observed-to-Expected number of predicted taxa of macroinvertebrates or O/E-ratio of taxonomic comp…
Effect of pentachlorophenol on predator-prey interaction of two rotifers
1997
Abstract The effect of pentachlorophenol (PCP) on the predator-prey relationship of two rotifers (Asplanchna girodi and Brachionus calyciflorus) was studied using Asplanchna predatory behavior as an endpoint. The experimental design included three treatments: prey and predator exposure, only prey exposure, and only predator exposure. This enabled us to distinguish toxic effects on the predator from those on the prey and to detect interactions. The main toxic effects observed were on the predator and involved the number of predator-prey encounters. Encounters decreased in a dose-dependent manner, with a no observed effect threshold at 0.11 mg PCP l−1. Decrease in encounter rate reduced the n…
Social and solidarity economy and the need for its entrepreneuring ecosystem: Current challenges in Brazil
2020
Made available in DSpace on 2020-12-12T02:05:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 This articles purpose is to discuss the state of the art of the constitution of the entrepreneurial ecosystem for SSE and its application in Brazil. One of the major challenges for the creation, continuity and strengthening of Solidarity Economy Enterprises (SEE) is the effective establishment of an entrepreneurial ecosystem for Social and Solidarity Economy (SSE). The construction of the solidary entrepreneurial ecosystem is a complex task, full of challenges, especially when this construction is associated to structural weaknesses inherent to its modus operandi. Case studies of sev…