Fall in the Salt Marsh
By Capt. Weatherly
Every August, the salt marsh announces the coming of Fall. I have a little flash of excitement combined with sadness when I see the first one: a blade of Spartina grass soaring proudly above the rest. It’s my signal that the long, lazy days of summer are slipping away. Our salt marsh undergoes a seasonal cycle, and we often joke that the grass is a better calendar than the trees. It keeps a tight schedule!
As days begin to shorten, the grass grows nearly another foot. The long, billowy blades soon flower and produce seeds. You may be wondering how the grass knows it’s time. August isn’t cooler than July, and it certainly doesn’t scream get ready for fall!
Plants have several ways of “knowing” the seasons. Temperature may be a useful indicator for us (and cooler temps slow the flow of water and nutrients, letting plants know it’s time to slow down growth), but the biggest signal to trigger seasonal change is a shortening photoperiod. As days grow shorter, light-sensing pigments notice the subtle change and tell the plant it’s time to start winter prep. Fewer daylight hours means less time for photosynthesis (the process of turning sunlight into energy) and plants reduce production of the chlorophyll, the pigment that turns leaves green. The breakdown of chlorophyll lets other pigment colors shine through, and leaves begin to turn the vibrant colors of fall!
Throughout Sept and Oct the flowers will be wind-pollenated, seeds will fall, and the marsh will turn a brilliant gold. Fall sunsets make the saltmarsh glow! Spartina grass dies off each winter and come spring, bright green shoots will start inching their way up alongside last year’s growth.
Eventually last year’s grass works loose and floats out into the water. A lot of it breaks apart in the water and sinks to the bottom where it is broken down by the plethora of decomposers living in the pluff mud. High tides float rafts of sticks into the waterways and some drift to the front beach. Waves push it ashore, creating a wrack line (line of shells, sticks, etc. deposited at high tide). Piles of sticks help the beach catch windblown sand and can help with erosion control. The nutrients flowing from the saltmarsh into the open ocean are so plentiful that in terms of biomass (not species diversity although we’re strong there too!) our estuaries rival tropical rainforests to be the most productive ecosystem in the world!
Next time you walk by the marsh in late summer, look closely – you’ll see the grass standing tall, seeds blowing in the wind, and the golden glow that tells us fall is on the way.
Note: The scientific name of smooth cordgrass has long been Spartina alterniflora. It has recently been changed to Sporabolis alternifloris. Change is hard.