Many marine and estuarine benthic animals are attached to the sea floor throughout their adult life or have limited mobility. The tiny, free-living larval stages of these animals are the main means by which they disperse to other places. This dispersal, settlement to the bottom, and metamorphosis of these larvae into new adult organisms characterize the process of recruitment. Recruitment links populations at different sites and provides the new individuals that allow populations to recover when decimated. The links between production of larvae by adults and actual recruitment to the sea bottom are often obscured by
- disjunct, patchy distributions of source populations,
- a diverse range of species with larvae that live for minutes to months over which dispersal occurs, and
- local and regional current systems that carry recruiting larvae varying distances.
We still know little about the extent of mortality of planktonic larvae during the time they are dispersing or how many microscopic new recruits die on the bottom before they are large enough to be observed.
The images on this page show larval, new recruit, and adult life-stages of the colonial bryozoan Bugula turrita . Un-released larvae and a swimming larva can be seen in the bottom-left image. Click on an image to see the enlarged version.