The following year, I learned more about the harbor when I coincidentally visited the harbor about 30 minutes before low tide. The North Marina was already drained of water, and, in the South Marina, the receding water under the docks was rapidly disappearing. I realized that the twice-daily exposure at low tide and high sediment levels were probably the most significant contributing factors to the distribution of species (see additional images in Footer at bottom of Blog).
High tidal variation is characteristic of the Gulf of Maine, and in the North Harbor, the shallow bay is filled and emptied during each tidal cycle. This variation has a positive effect on marine life (e.g., oyster beds) in that it brings in fresh seawater twice a day. At the highest tides, the harbor is filled and Duck Creek is a shallow bay. At the lowest tide, Duck Creek is drained and the marina is transformed into a mudflat. Tidal variation in the summer averages over 10 feet, and this July, the tidal variation peaked at over 14 feet.
View of the North Wellfleet Harbor at Low Tide
Diadumene Habitat on the Side of the Main Dock in the North Marina