This is why we are in business! Marine plants are becoming recognized as valuable allies in the fight to keep our marine environment clean and healthy. Marine plants can absorb as much as 5 times the CO2 as terrestrial plants and absorb large quantities of phosphate and nitrogen from fertilizers entering the Salish Sea. Marine plant aquaculture- seaweed farms- have also been shown to influence the carbonate (aragonite) concentrations and provide a refuge for pteropods, dungeness crab larvae and other shell forming plankton adversely affected by ocean acidification. They also provide cover for herring, other forage fish and the base of the food web whose health is critical to the survival of our salmon and ultimately the Orcas.
While we applaud the creation of rain gardens to help mitigate the influx of toxins into the Salish Sea it seems that there is not much effort going on below high water. When placed downstream of storm water outfalls, marine plants have the ability to absorb large amounts of organic nutrients and can also act as phytoaccumulators of heavy metals, PAHs (Poly Aromatic Hydrocarbons), PCBs (Poly Chlorinated Biphenols), and other toxins and pollutants from the water (1).
Marine plants that have absorbed fertilizers from agricultural or residential run off and then returned for use as fertilizer effectively create a loop and a check point . Plants with contaminants that are not degraded may be better suited for use as a biofuel, or in a worst case scenario, as toxic waste. The goal is to keep them out of the Salish Sea. We know that many of these pollutants are bound to bacteria and incorporated into plankton. Macroalgae have also been found to harbor millions of bacteria on their exposed surfaces. Why some plants are more efficient than others at absorbing and /or degrading the pollutants is not well understood. Much more research is needed to take the rain garden approach of restoration into the sea.