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EN
90Sr activity was determined in Zostera marina collected in the Gulf of Gdańsk in 2008-2013. 90Sr activity in Z. marina from Jama Kuźnicka and Klif Orłowski range from 0.83 Bq kg-1 d.w. to 3.78 Bq kg-1 d.w. and from 0.68 Bq kg-1 d.w. to 4.95 Bq kg-1 d.w., respectively. The plants collected in spring-summer showed significant differences between 90Sr content in blades - 1.55 Bq kg-1d.w. in 2011 and 2.18 Bq kg-1 d.w. in 2013, and in roots - 7.75 Bq kg-1 d.w. and 11.44 Bq kg-1 d.w., respectively. The reduction in 90Sr concentrations in Z. marina roots to 1-2 Bq kg-1 d.w. in summer resulted from the transport of this element to the young parts of the plant. In autumn and winter, the 90Sr content in the blades of Z. marina was increasing and reached the maximum of 3.77 Bq kg-1 d.w. This could be explained by the process opposite to dilution, related to the biomass reduction and strontium concentration in the plant tissues. Changes in 90Sr concentration in Z. marina tissues are affected by isotope concentration in seawater as well as by salinity, which affects the concentration of Ca2+ - for which Sr2+ is a chemical analogue
EN
This study shows the macrozoobenthic biodiversity and the quality status of the Zostera marina meadow in the Gulf of Gdańsk. To our knowledge, this is the first study focused on the assessment of environmental quality based on macrofauna occurring on such a small and specific habitat as a seagrass meadow. The meadow is dominated by Zostera marina, but also Zanichellia palustris and Potamogeton pectinatus are present. Compared to the soft bottom macrofauna in the southern Baltic, the biodiversity of macrozoobenthos is very high, which is reflected in 33 taxa observed during the whole research, while the mean number of taxa was 12. There were also some taxa found only on the bottom overgrown with vegetation, e.g. Idotea balthica or even taxa that are currently rarely observed in the Gulf of Gdańsk, e.g. Gammarus locusta or Gammarus ineaquicauda. Nineteen percent of the stations were classified into the very good quality status and 50% into the good quality status, so the environmental status of this meadow based on the BQI index is assessed as good. Given these results, this is probably one of the best preserved meadows in the southern Baltic.
3
Content available remote Genetic characteristics of three Baltic Zostera marina populations
EN
We performed genetic analyses of three Baltic eelgrass (Zostera marina) populations in Puck Bay (PB), Cudema Bay (CB) and Greifswalder Bodden (GB). The aim of this study was to identify the eelgrass population genetically closest to that from the PB, which could potentially serve as a reservoir for the restoration of the underwater meadows in this bay, seriously degraded in the past. We applied a 12-microsatellite assay to test the genetic distance between the target eelgrass populations. We found that the allelic richness values of the GB, PB and CB populations were 2.25, 3.77 and 3.50 respectively. The genetic diversity found in GB was low and could be explained by the population's history, whereas the diversity of CB was higher than expected in a population located at the edge of the species' range. Analyses of genetic differentiation and structure showed that of the three populations studied, PB and CB were closer to each other than to the GB population. The reasons for this differentiation in eelgrass populations and the implications of the results of their genetic analysis on the planned restoration of the PB populations are discussed.
EN
Methodological aspects of the arrangement of stranded wrack for the degradation rates within the litterbags were tested in a simple field experiment on temperate, fine/medium quartz sediment, sandy beach in Poland at the end of the Hel Peninsula (54°36’N, 18°49’E). Litterbags of the mesh size of 0.5 mm were used to construe and assess the role of the pre-drying of wrack before its placement into the bags. The field station was established on the backshore, 15 m in width seaward from the crest of a dune. Three methods of predrying were done: (1) air drying, (2) oven drying, (3) freeze drying, as well as (4) non-dried fresh material was used as reference. The stranded seagrass wrack (Zostera marina L.), obtained directly from the beach, and then prepared in accordance with the procedures described above, was used as the study material. Four trials were run with five repetitions of litterbags 7 cm long ´ 7 cm wide made from nylon mesh with 0.5 mm aperture widths. After exposition, bags were retrieved 5, 10, 50, 100, 150, 200 and 250 days post-placement. In the laboratory, samples of remaining material were dried by the same method as earlier, respectively, and then weighed, and analysed using a CHNS Analyser. It was shown that, under similar conditions of sediment composition, salinity and wave inundation, the method of predrying had little influence on the long-term process of decay. In the case of non-dried replicates, degradation rapidly proceeded in the initial stages and then stabilised to be linear, whereas, in dried samples it was done so linearly throughout the study period with only little differences. Such differences observed in the early part of the experiment were most likely the result of differences in material structure and the initial chemical composition of the plant material caused by a predrying-incurred disturbance in the chemical structure. Nevertheless, short-term environmentally driven sampling strategies fail to obtain conclusive results about degradation estimates of stranded wrack and should be avoided at least with the use of dried material.
EN
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 žm) 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.
EN
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 Jedrzejczak 2002), focusing 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, adult 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, turbellarians 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, which 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, did not affect the rate of seagrass disintegration. The effect of meiofaunal nematodes, oligochaetes, gastrotrichs 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.
EN
The significance of distance along the beach-dune transect and different moisture conditions as regards the decay of Zostera marina leaf litter was investigated in simple field experiments in three temperate, medium- to fine-quartz-sediment, sandy beaches of the Gulf of Gdansk in Poland. 1800 replicate litterbags of freshly stranded Zostera marina leaves were placed in beach sediments at different strata and levels on each of the beaches. The litterbags were sampled after 5, 10, 50, 100 and 150 days in the field and the remaining material was then dried and weighed. Under similar conditions of sediment composition, salinity and wave inundation, ANOVA tests revealed significant differences in breakdown through time and site. Thus there were some differences in the decay process between the low and high beach. In the former, degradation proceeded rapidly in the initial stages and then stabilised, while in the latter it remained linear throughout the study period. Matter loss in each stratum was also seasonally dependent. This may, however, be more closely linked to successional changes in the chemistry and/or microflora of the beach wrack than to its physical breakdown. Differences between organic matter degradation in the high and low beaches may be explained by differences in the moisture regime and nutrient status, and not by differences in the decay processes themselves. Therefore, two decay centres were found in the beach-dune system: the low beach together with the strandline (wrack consumption 12-21% day-1 in the warm season, and 4-10% day-1 in the cold season) and the dune (active consumption 2-6% day-1 in the warm season only).
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