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

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.