The story of the Puget Sound’s environmental health may come from a microscopic storyteller.
Foraminifera are single-celled organisms found in all marine environments. The morphology of their shell-like chambers varies immensely. According to Univ. of Washington, there are two major groups of foraminifera: one that produces shells built from calcium carbonate, and another that builds its shell by compiling tiny grains of sediment.
By studying 120 shell samples, collected between 1974 and 2009 from the Bellingham Bay and the Sinclair and Dyes inlets (both near Bremerton), postdoctoral researcher Ruth Martin and associate professor Liz Nesbitt determined the diversity and number of foraminifera are on the decline.
“Even though chemical analysis of the water suggest Bellingham Bay and Bremerton waters are healthy, foraminifera are telling us a different story,” said Nesbitt, who is the curator of invertebrate and micropaleontology at the university’s Burke Museum of Natural History and Culture. “However, it is important for us to provide independent, scientific studies for society to then decide how to best address the health of the Puget Sound.”
Though some foraminifera species are particularly sensitive to environmental stressors, others are more tolerant and thrive despite pollution from sewage or industrial waste.
“The embayments, Sinclair and Dyes inlets, have been subjected to contamination by military, industrial, residential and agricultural effluents for over 100 years, resulting in some of the most toxic marine sediments in Puget Sound,” the researchers write. “(We) found that benthic foraminiferal assemblages were notably of low species diversity and strongly dominated by species tolerant of various contaminants and dysoxia. Foraminiferal density and diversity deteriorated between 1974 and 2008, with Sinclair Inlet showing a near collapse of foraminiferal assemblages by 2008.”
The reason behind the decline remains elusive. However, the researchers believe the shells may hold clues. A healthy shell from the foraminifera species Elphidiella hannai appears smooth, its shell completing a full spiral. An unhealthy specimen is bumpy, marred by disintegration.
“The dissolved foraminifera are indirect evidence of acidity in the water,” said Maritn. “In the future, collecting pH and dissolved oxygen levels at the bottom of the water would help confirm acidification in Bellingham Bay and the inlets of Bremerton.”
Currently, Martin and Nesbitt are investigating the health of foraminifera in the neighboring Commencement Bay.