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Three sandy beaches on Phuket and Kho Khao islands, Thailand, were monitored annually to study the short- and long-term impacts of the 2004 tsunami on their meiofauna assemblages and sediment characteristics. The sediment grain size compositions changed significantly within one year after the tsunami (improved sorting and less negatively skewed distributions), but meiofauna assemblages did not. The fast recolonization of the beaches after the tsunami confirmed that meiofauna is highly resilient to ecosystem disturbances. The tsunami was not observed to have a long-term impact on meiofaunal assemblages.
Free-living Plathelminthes constitute an important component of meiobenthic communities in various marine benthic environments, but research focusing on this group is generally scarce. The current study investigated the free-living interstitial flatworms of the shallow sandy sublittoral zone of the southern Baltic coast. Sediment samples were taken at Hel Peninsula at water depths of 1.5 m and 7 m, and the plathelminths were identified alive to the species level. In total, 22 species were identified. The majority of the species belonged to Kalyptorhynchia and Proseriata, but Acoela recently moved from Plathelminthes into their own phyllum and represented by Mecynostomidae, was the most numerous group. The average total plathelminth densities ranged between 6 and 74 ind. 10 cm–2. The vertical distribution of the plathelminth fauna in the sediments was usually limited to the upper 3–4 cm, except for acoels which penetrated deeper into the sediment layers. The role of both sediment water saturation and oxygen availability appeared to be the main factors limiting flatworm occurrence in the sediments investigated in this study.
This paper evaluates the second part of a three-year field study to investigate the effects of the beach macro- and meiofauna community structure on the decay of stranded wrack on Hel Beach (see Jędrzejczak 2002),f ocusing on successional changes and the colonisation of wrack by beach fauna. The investigation enabled the associated faunal assemblages to be characterised. Zostera marina tissue was colonised by the supralittoral fauna in two distinct phases. The macrofauna, including the talitrid amphipod Talitrus saltator,ad ult Diptera and Coleoptera, colonised the wrack within a day,with maximum numbers being recorded after 3 days. Thereafter,their numbers in the samples declined and the meiofauna, consisting of nematodes, oligochaetes,tur bellarians and dipteran larvae, became increasingly abundant. After 18 days,the wrack surface was dominated by meiofauna. This faunal succession was not directly related to the degradation of the seagrass tissue,whic h proceeded linearly throughout the study period. Exclusion of macrofauna from the wrack by the use of < 1 mm mesh litterbags had no appreciable effect on the rate of dry matter loss. Therefore,the major macrofaunal wrack consumers,including T. saltator and Coleoptera,d id not affect the rate of seagrass disintegration. The effect of meiofaunal nematodes, oligochaetes,gast rotrichs and turbellarians on wrack breakdown could not be accurately determined. However,the development of the meiofaunal community suggested that changes in the fauna community were linked more closely to successional changes in the chemistry and/or microflora of the beach wrack than to its physical breakdown.
The effects of the beach community structure of macro- and meiofauna on the process of beach wrack decay were investigated by means of a simple field colonisation experiment in a temperate, fine quartz sediment, sandy beach at the end of the Hel Peninsula in Poland. 1260 replicate litterbags of three mesh sizes (12 mm, 0.5 mm, 48 μm) containing fresh wrack were used to assess the role of faunal and non-faunal components in the breakdown of stranded Zostera marina. Wrack breakdown was determined during a three-year field study. This paper presents the first part of the results of this field experiment, which refer to the effects of fragmentation detritivory, leaching and decay rates. Material was lost from the bags at a rapid rate, with only 22–32% of the original dry mass remaining after 27 days in the field. This degradation was not directly related to the faunal succession of the eelgrass tissue, which proceeded in two distinct phases throughout the study period. Exclusion of macrofauna from the wrack by the use of finer-mesh litterbags (< 1 mm) had no appreciable effect on the rate of dry matter loss. Microbial decay, and abiotic leaching and fragmentation are probably the major causes of seagrass weight loss from the litterbags.
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