The Hudson River’s ecosystem is very different from the Great Lakes. Lake water settles into layers, with cool water near the bottom and warm, clear water above. But water in the Hudson is affected by tides from the Atlantic Ocean. They mix the water from top to bottom. Tides also stir up silt from the riverbed, making the water turbid or cloudy. Little sunlight can pass through the murky water. Less sunlight means fewer plants and phytoplankton.