During a toxicity lab performed at UCSB, we took butter lettuce seeds and used UCSB Lagoon water taken from the North shore (farthest away from Pacific Ocean opening) near the faculty lounge, to see if the seeds would grow. When the water was collected, we noted significant levels of algae and detritus in the water (strong offensive smell). Due to the proximity of our collection location to the Pacific Ocean, there may have been significant levels of salt in our test substance. The contaminated lagoon water poisonous in lettuce seeds and inhibited germination and growth of the radical in seeds treated with concentrations 10% and above with the lagoon water. My question is; what are the chemical components of the water that inhibit growth in the butter lettuce seeds?
I have tried to look for chemical or elemental analysis of the UCSB lagoon water but have not found any good data to actually answer your question. I have often felt that the lagoon is both underappreciated and understudied. I agree with you that the high salt levels in the water would definitely have a profound effect on growth of your seeds. Any changes in osmotic balance between the seeds, roots and their environment will effect both germination and growth rates. The offensive smell that you described is most likely sulfur which is generated by bacteria in anoxic, low oxygen, environments. This chemical could be inhibiting germination. In my search I also found that UCSB has been using a larval pesticide in the lagoon in order to attempt to compat the breeding of mosquitoes in the stagnant waters. Maybe this is having an effect on your lettuce? If you or your students are studying chemistry next there are some relatively cheap chemical analysis kits for water quality that would be fun to use to test the lagoon and would tie in nicely biology with chemistry...interdisciplinary is where it is at these days.