Some Ecological Aspects of the Tidal Zone of the North Carolina Coast

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The tidal zone of the North Carolina coast presents a wealth of ecological problems. This zone includes the narrow strip along the ocean f ront, sounds, and rivers, between the high and low tide levels. In this paper, however, the term tidal zone is restricted to the inner belt along the sounds and rivers not affected by the action of the waves of the ocean. The term strand is used for the zone of the beach exposed not only to the rise and fall of the tide but to the direct action of the waves of the sea and the sand blast. Ecologically these two regions are very different. The strand on our coast is practically bare of vegetation and frequented very largely by animals which are scavengers or beach combers. The tidal zone, on the other hand, is often an area of considerable extent and is usually well covered by grasses. At least three species of grasses grow luxuriantly here, a fine short grass growing principally about low tide level, a coarser grass growing principally in the pockets at higher level, and a fine matted grass growing near the high tide level. To these three should be added the common sea oats (Uniola paniculata) which starts just below high tide level and continues up into the higher dunes, and the salt marsh sedges which grow in shallow water and are more or less exposed at low tide. In addition to the areas covered by grasses there are many of considerable extent which are devoid of vegetation. The tidal zone supports a number of terrestrial forms which invade it during low tide, as well as several forms which live permanently here. We need look for no special adaptations in the former group as they are for the most part active creatures which make the most of any situation. In the latter class there are, however, many unsolved questions of interest, not the least important one being the factors which make it possible for these normally terrestrial air breathing animals to maintain themselves in a locality which is strictly aquatic for a longer or shorter period each day. Are we to look for morphological or for physiological adaptations? Are the groups that are present represented by a single species of several species? If a group is represented by several species, are the species of independent origin or are they perhaps descendants of an early ancestral type that has wandered into this region? These and many other questions might be asked. Some of them I believe can be an-