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Rosemary Hartman - Marine Invasions

St. Mary's College of Maryland

CDOM Absorbance as a Ballast Water Exchange Verification Tracer

Ballast water is a major vector for invaders in coastal marine environments. So far, the only practical method of mediating ballast water introductions is mandatory open ocean ballast water exchange, however salinity is the only current method of verifying that exchange has taken place, and it is not useful in high salinity ports. I examined absorbance of chromophoric dissolved organic matter (CDOM) as a possible alternate to salinity for ballast water verification. I measured the absorbance of port water samples taken from seven ports around the pacific rim, as well as two transects from 80 miles off shore to port. I found there was a significant difference between average absorbances in each port, with average absorbance being largely driven by salinity, indicating it may be possible to tell which port ballast water was taken from. There was a significant difference between average summer and winter absorbances in most cases; though many factors need to be considered before predicting which season had highest CDOM. The transects show that there is a significant difference in absorbance between port and offshore samples, even in highly saline ports. This means that CDOM absorbance could potentially be used to tell how far off shore ships are exchanging their ballast water.