Physical factors influencing active emergence of meiofauna from boreal intertidal sediment

Werner.Armonies [ at ]


Some intertidal meiobenthic taxa actively emerge from the sediment and enter the water column. Laboratory experiments were conducted to test whether emigration is influenced by physical factors. Light exposure correlates negatively with the numbers of Copepoda, Plathelminthes and veliger-larvae swimming into the water column and the numbers of Ostracoda that are active on the sediment surface, perhaps reflecting a general means of predator avoidance. A temperature lower than seasonally occurring in the field strongly decreased emigrahon. Oxygen deficiency did not affect Ostracoda and veliger-larvae but caused additional plathelminth species to enter the water column. More copepods (copepodites) emerged from the sediment when oxygen content was increased by constant illumination. Interstitial salinity affected the numbers of Copepoda and Plathelminthes leaving the sediment. Highest swimming activity was recorded from interstitial salinities >30 %o. From sediment with ambient salinity, similar numbers of Copepoda entered water columns with 25 to 35%- but significantly fewer individuals entered 20 and 40%0 water. Ostracod activity was only decreased at 40%0. Plathelminth swimming activity was negatively correlated with the salinity of overlying water. These results suggest a strong dependence of emigration rates on physical factors with taxa responding in differential ways. Generally, emigration into the water column may be (1) an integral part of meiobenthic life style, enhancing dispersal and, possibly, allowing for exploitation of food resources in the water column; or (2) a means of escape from dangerous factors in the sediment, either physical or biotic.

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Armonies, W. (1988): Physical factors influencing active emergence of meiofauna from boreal intertidal sediment , Mar Ecol Prog Ser, 49 , pp. 277-286 .

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