Discrete Organic Phosphorus Signatures are Evident in Pollutant Sources within a Lake Erie Tributary

Phosphorus
loads are strongly associated with the severity of harmful
algal blooms in Lake Erie, a Great Lake situated between the United
States and Canada. Inorganic and total phosphorus measurements have
historically been used to estimate nonpoint and point source contributions,
from contributing watersheds with organic phosphorus often neglected.
Here, we used ultrahigh resolution mass spectrometry to characterize
the dissolved organic matter and specifically dissolved organic phosphorus
composition of several nutrient pollutant source materials and aqueous
samples in a Lake Erie tributary. We detected between 23 and 313 organic
phosphorus formulas across our samples, with manure samples having
greater abundance of phosphorus- and nitrogen containing compounds
compared to other samples. Manures also were enriched in lipids and
protein-like compounds. The greatest similarities were observed between
the Sandusky River and wastewater treatment plant effluent (WWTP),
or the Sandusky River and agricultural edge of field samples. These
sample pairs shared 84% of organic compounds and 59–73% of
P-containing organic compounds, respectively. This similarity suggests
that agricultural and/or WWTP sources dominate the supply of organic
phosphorus compounds to the river. We identify formulas shared between
the river and pollutant sources that could serve as possible markers
of source contamination in the tributary.