Developing Triple Oxygen Isotopes as a Tool for Quantifying Benthic Primary Production
Rachel H. R. Stanley, Marine Chemistry & Geochemistry
Project summary
Coastal zones have enormous societal importance, given that more than 50% of
Americans live near the coast. Humans have heavily impacted coastal zones in general, and
estuaries in particular. Many estuaries show signs of eutrophication, adversely affecting water
quality and leading to harmful algal blooms. Some estuaries are under remediation but they often
do not respond quickly, if at all, to a drop in nutrient loading. Therefore, a better understanding
of the cycling of nutrients in estuaries is needed. Benthic photosynthetic algae have been found
to be a major player affecting the cycling of nutrients, particularly nitrogen, in estuaries.
Additionally, benthic photosynthetic algae have been estimated to be responsible for 50% of
primary production in estuaries overall, and in any particular estuary may be a factor of 10 more
important than pelagic algae. However, very few methods exist for quantifying the extent of
benthic microalgal photosynthetic activity. Here, we propose to develop a new method for
quantifying benthic microalgal photosynthesis based on triple oxygen isotopes (TOI) –
measurements of 16O, 17O and 18O. TOI respond only to photosynthesis – not to respiration – and
therefore are ideal for studying benthic photosynthesis. The TOI method would solve many of
the problems associated with commonly used current methods, and once developed, could be
widely applied to quantify benthic microalgal photosynthesis in a number of estuaries.