Abstract
We tested experimentally the hypothesis that prevailing locomotion/feeding strategies and body morphology may lead to more active dispersal of free-living marine nematodes, besides passive transport. Neutral Red was applied to the sediment inside cores and the red plume formed during the flood tide was divided into near, middle, and distant zones. At 0.5 m and 1 m from the stained cores, sampling nets were suspended 5 and 10 cm above the sediment-water interface. Dispersion behaviors were defined as a function of a) the numbers of stained recaptured nematodes in comparison to their mean densities in the sediment, b) movement in the sediment or swimming in the water column, and c) body morphology. Tidal currents with average velocities of 9 cm/s resuspended the numerically dominant nematode taxa Sabatieria sp., Terschellingia longicaudata de Man, 1907, Metachromadora sp. and Viscosia sp. The recapture of stained nematodes as far as 2 m from the original stained cores showed that, despite their small body size, they can disperse through relatively large distances, either passively or actively, via the water column during a single tidal event. Recapture patterns in the sediment and in the water column indicate that nematode dispersal is directly influenced by their body morphology and swimming ability, and indirectly by their feeding strategies, which ultimately define their position in the sediment column. Besides stressing the role played by passive transport in the water column, our experiment additionally showed that mobility and feeding strategies also need to be considered as determinant of short-scale nematode dispersal.
Highlights
Dispersal processes determine the present and potential distribution range of a species
The recapture of stained nematodes as far as 2 m from the original stained cores showed that, despite their small body size, they can disperse through relatively large distances, either passively or actively, via the water column during a single tidal event
By using a vital stain and recapturing nematodes in situ in a subtropical unvegetated tidal flat at Paranaguá Bay (S Brazil), this study aims 1) to assess the relative importance of nematode dispersal in the water column and over the sediment during a single tidal event in small spatial scales; and 2) to determine whether small-scale dispersal depends on nematode behavior such as movement and body morphology
Summary
Dispersal processes determine the present and potential distribution range of a species. The organisms most commonly found in the water column dwell in the upper layers of sediment and so are more susceptible to passive suspension (PALMER & GUST 1985, COMMITO & TITA 2002). This is especially true in high-energy areas, in which meiofaunal taxa are resuspended by waves and tidal currents (BOECKNER et al 2009). By using a vital stain and recapturing nematodes in situ in a subtropical unvegetated tidal flat at Paranaguá Bay (S Brazil), this study aims 1) to assess the relative importance of nematode dispersal in the water column and over the sediment during a single tidal event in small spatial scales; and 2) to determine whether small-scale dispersal depends on nematode behavior such as movement (swimmer vs. non-swimmer; active vs. lethargic) and body morphology
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