5. Osprey Outlook Floating Dock

As you travel to the end of the boardwalk and look into the main channel – this is Jarvis Creek – you will see that the water in the salt marsh is a green or brownish color. This is due to the presence of large amounts of phytoplankton in the water. Phytoplankton is microscopic algae, and like all plants phytoplankton needs water, sunlight, and nutrients to survive. Therefore, our waterways are clearer in the winter months when there is less sun and phytoplankton present.


The Salt Marsh is rich in nutrients that are provided by decaying Smooth Cord Grass. This tall grass dies every year during the winter and grows again in the Spring. The dead grass eventually breaks up and floats in large mats called spartina wrack. If you look around you should be able to find individual pieces of dead grass floating around as well the larger mats of grass. The wrack decomposes and breaks into smaller particles that provide the nutrients needed by the phytoplankton.


Nutrients in the water usually sink to the bottom, but in the Lowcountry Salt Marsh nutrients are always mixed in the water because of our large tidal range. Hilton Head Island, has the second highest tidal range on the east coast, second to the Bay of Fundi. The average tidal range here is between 7 and 9 feet between high and low tides. The strong tidal range, and the abundance of nutrients are the reason for the large phytoplankton quantities in this Salt Marsh.