Aquatic ecology and Biodiversity

Unit 11- Intertidal zone

11.4.1. Biological diversity
Plants are limited to microscopic algae (diatoms) and filamentous algae on the sediment surface, and occasionally seaweeds, such as Fucus spp. attached to stones. Some Cord Grass is found at the first stage of tidal-marsh succession, and eel grass occurs on the lower shore.

Successional sequence
•In sheltered areas, the deposition of sediment on the shore will eventually raise the level so that seeded or ice-transported cord grass may become established.
•The cord grass expands from the point of colonization by vegetative means and accelerates the rate of sediment deposition, developing into the low marsh.
•When the substrate of the marsh rises to the mean-high-water mark through the accumulation of sediment, the cord grass gives way to marsh hay and associated plants, and the high marsh develops.
•With further sediment deposition, the vegetation becomes mainly freshwater: cattail, rushes and reeds, possibly in association with spruce (swamp).
Animals
Animals are predominantly detritus-feeding infauna that can tolerate exposure at low tide. Polychaete worms (Spiophanes wigleyi, Clymenella torquata), amphipods (Corophium volutator) and bivalves (Mya arenaria, Macoma balthica) are particularly common. Scavengers and carnivores present are polychaetes (Neanthes virens), crustaceans (Chiridotea caeca, Crangon septemspinosus) and molluscs (Ilyanassa obsoletus, Lunatia heros). Sessile epifauna species, such as barnacles and slipper limpets, occur attached to small stones lying on the mud surface. Flounders and other fish species come on to the mud flats to feed at high tide. Mud flats are also important feeding areas for migratory shore birds, such as the Semipalmated sandpiper, and land mammals (particularly raccoons).