Humans have controlled the flow of Marshfield’s Green Harbor River for centuries. In the 1800s, at the behest of farmers who wanted more grazing land, a dike was built to limit how much tidal water flowed upstream into the river.
It was the beginning of a slow loss of habitat as the river’s salt and oxygen dropped. But recently, plant and animal species that sharply declined or disappeared are returning. From tiny invertebrates to clams and fish, the marine life is coming back.
Worms that live in the sediment have been observed on the upstream side of the dike in the last two years. Environmental officials have found six species of worm and five species of amphipod, a diminutive crustacean.
The fish are coming back, too. Species found in the river in the last two years include Atlantic silverside, banded and striped killifish, flounder, northern pipefish, sculpin, and tautog. Officials have also recorded soft shell clams, various species of crab and shrimp, snails, sea grapes, and barnacles, as well as plants that thrive in salt marshes.
Found in the Green Harbor River in 2010 and 2011:
Carcinus maenas - green crab
Crangon septemspinosa -
sevenspine bay shrimp
Dolichopodid larva - long-legged fly
Fundulus diaphanus - banded killifish
Fundulus heteroclitus - mummichog
Fundulus majalis - striped killifish
Gasterosteus aculeatus - threespine stickleback
Hemigrapsus sanguineus - Asian shore crab
Molgula - sea grapes
Mya arenaria - softshell clam
Pagarus longicarpus - longclawed hermit crab
Palaemonetes vulgaris - marsh grass shrimp
Palaemonetes pugio - daggerblade grass shrimp
Illyanassa obsoleta - Eastern mudsnail
Littorina littorea - common periwinkle
Menidia menidia - Atlantic silverside
Myoxocephalus - sculpin (species not identified)
Syngnathus fuscus - Northern pipefish
Tautoga onitis - tautog
flounder (species not identified)
6 species of worm
5 species of amphipod
Salicornia - a succulent found in salt marshes
Spartina alterniflora -
salt marsh cordgrass
Sources: Sara Grady, Massachusetts Bays Program; Jason Burtner, Office of Coastal Zone Management.