MARINE LANDSCAPES AND FAUNAL RECRUITMENT - A FIELD-TEST WITH SEAGRASSES AND COPEPODS

The influence of plant landscapes on recruitment of meiofaunal copepods was investigated in a New Zealand seagrass bed. Artificial plant mimics were placed into sediments at levels equivalent to natural blade densities (100 units per 0.5 x 0.25 m plot) in a variety of experimental treatments and retrieved 3 or 5 d later. To assess the effect of plant arrangement on faunal recruitment, plots were established within a seagrass bed in areas clipped of vegetation with (1) natural vegetation immediately surrounding the experimental plot; (2) natural vegetation clipped up to 0.5 m from plot edges; and (3) vegetation clipped up to 1 m from plot edges. Outside the natural seagrass bed plots were established in unvegetated sediments 0.5 m from the edge of the bed. Additionally, mimics were placed into plots 0.5 m from the edge of the bed which had sediment surfaces covered by plastic sheeting to determine whether recruitment onto plant mimics was from underlying sediments or from outside plots. Density of total copepods was highest on plant mimics with vegetation immediately adjacent to clipped areas inside the natural seagrass bed after 5 d. Densities of total copepods on mimics placed outside the bed were 5x higher than those inside the bed and the covering of sediment significantly reduced recruitment. The dominant copepod species, Bulbamphiascus sp., recruited to mimics irrespective of sediment border and probably invaded mimics from underlying sediments, although this was not true for other common species. While plant arrangement may influence recruitment of some copepod species, altering access to a source pool had a much greater effect on copepod densities on plant mimics.