Evaluation of Submarine Groundwater Discharge as a Source of Nutrients, Carbon , and Metals to the Monterey Bay Extreme Bloom Incubator

Northern Monterey Bay, California is subject to recurrent algal blooms of dinoflagellates and diatoms, which can persist for over a month. The area of Monterey Bay where the algae persist has been termed "the incubator". While physical conditions contribute to the formation and retention of blooms in the incubator, the source of constituents needed to sustain the bloom in the incubator is poorly understood. This study investigated submarine groundwater discharge (SGD) as a source of nutrients, carbon and metals to the incubator. SGD flux was determined using naturally occurring radiogenic tracers, and was found to be 87± 12 cubic meters per day per meter of shoreline. Bay water from the incubator was then used to conduct time series incubation experiments to investigate the role of groundwater and groundwater constituents in sustaining the incubator. Algae in incubator water showed the greatest response to SGD and nitrogen additions, as measured by chlorophyll increase. SGD around the bay is enriched in nitrogen compared to bay waters, suggesting nitrogen in SGD is an important constituent to maintaining the incubator in Monterey Bay.