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Predrying of stranded wrack material as an aspect of the litterbag techniques in the sandy beach studies

Jędrzejczak M. F.

Oceanological and Hydrobiological Studies

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2003

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Vol. 32, No. 1

59-74

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.

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Stranded Zostera marina L. vs wrack fauna community interactions on a Baltic sandy beach (Hel, Poland) : a short-term pilot study. Part I. Driftline effects of fragmented detritivory, leaching and decay rates

Jędrzejczak M. F.

Oceanologia

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2002

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No. 44 (2)

273-286

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.

3

Stranded Zostera marina L. vs wrack fauna community interactions on a Baltic sandy beach (Hel, Poland) : a short-term pilot study. Part II. Driftline effects of succession changes and colonisation of beach fauna

Jędrzejczak M. F.

Oceanologia

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2002

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No. 44 (3)

367-387

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.

4

The degradation of stranded carrion on a Baltic Sea sandy beach

Jędrzejczak M. F.

Oceanological Studies

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1999

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Vol. 28, No. 3-4

109-141

EN

Litterbags of two mesh sizes (0.5 mm and 0.02 mm) were employed to assess the role of faunal and physical components in carrion breakdown on sandy beaches. Field experiments were undertaken on two sandy beaches in Poland. The tissue of Gadus morrhua L. and the white of a hen's egg were used as substrata to be decomposed in the litterbags. The bags, together with control bags, were distributed in three trials in different beach locations (medium water-mark, strandline, backshore, and dune) and at appropriate depths (5, 20 and 50 cm deep). Each trial was run for 20 days and was set up on the beach profile. The litterbags were retrieved after 3, 6,10, 15 and 20 days. The remaining material was then dried and weighed, and analysed using a C11N Analyser. Organic material was rapidly lust from the litterbags. From 4 to 56 % of the original dry mass remained after 20 days in the field in the coarse-mesh bags. However, between llic low and higW-beach stations there were some differences in the decay process. At the former, degradation proceeded rapidly in the initial stages and then stabilised, at the latter it did so linearly throughout the study period. The fact that fauna were excluded from the carrion by the use of finer mesh litterbags had an appreciable effect on the rate of dry matter loss. Microbial decay, abiotic leaching and fragmentation were thought to be major causes of carrion weight loss from the litterbags. The rate of dry mass loss, expressed as loss of organic material, ranged from 1 to 14% per day. At the same time, the C/N ratio increased, which was evidence of the earlier use of nitrogen as an energy source. These results suggest that differences in organic matter degradation in high and low-beach areas can be explained by differences in moisture regime and nutrient status and not by differences in the decay processes themselves.