Abstract:
Halogenated 1’-methyl-1,2’-bipyrroles (MBPs) are a distinctive class of
marine organic compounds. They are naturally produced, they have a unique
carbon structure, they are highly halogenated, and they bioaccumulate in upper
trophic levels. MBPs share many characteristics with persistent organic
pollutants (POPs), and may prove to be useful natural analogues for these
anthropogenic compounds. Further, their unique structure suggests that their
biosynthetic organism(s) may have new genes to add to current knowledge of
biosynthetic chemistry. The objectives of this dissertation were to further clarify
the environmental distribution of MBPs, to examine whether MBPs biomagnify,
and to investigate possible origins of these compounds through their stable
nitrogen isotopic signatures.
Results from these investigations have shown that over 40 highly
brominated MBP congeners are present in marine mammals, fish, and squid
from the Northwestern Atlantic Ocean. The most abundant MBPs do appear to
biomagnify through the food web to reach the concentrations observed in marine
mammals. This additional evidence affords greater confidence in the use of
MBPs as natural analogues for POPs. However, differences in the environmental
chemistry of MBPs and anthropogenic compounds are also evident, and may be
due to these compounds’ different origins, or to the capacity of degradative
enzymes to act upon them. Finally, compound-specific nitrogen isotope analyses
on MBPs isolated from dolphin blubber show that these compounds are
dramatically enriched in 15N relative to other biosynthetic organic compounds.
This enrichment is likely a signal imparted during biosynthesis, and may assist
in elucidating the organism(s) and mechanism(s) responsible for the biosynthesis
of MBPs.
