A time series of benthic flux measurements from Monterey Bay, CA

In situ incubation chamber measurements of benthic nutrient recycling rates were made on the Monterey Bay shelf at 100 m during various years and seasons. Variability in nutrient (Si, PO42+, NH3, NO3-) and trace metal (Mn, Fe (11), Cu) fluxes correlate with variability in the amount of organic carbon oxidized on the sea floor. Patterns of primary productivity show a mid-year maxima, consistent with the timing of increased rates of benthic C-org and opal recycling. High rates Of C-org rain to the shelf promote nitrate consumption at a rate that equals or exceeds ammonia efflux. Low rates of C-org rain promote greater efflux of DIN; thus these margin sediments provide a negative feedback to local productivity cycles. The efflux of iron (11) from shelf sediments is sufficient to support >100% of new production, yet Fe flux is positively correlated with C-org recycling which lags the maximum in new production. On account of this time lag,. diagenetically recycled Fe is not likely a micro-nutrient trigger of new production, but could serve as a positive feedback. Bio-irrigation rates are seasonally variable by 30% but maximal during the maximum productivity months. (C) 2003 Elsevier Science Ltd. All rights reserved.