Water-column dark C02 fixation and bacterial-mat growth in intermittently anoxic Saanich Inlet, British Columbia

Abstract

Saanich Inlet in British Columbia, Canada, is a frequently cited example of an intermittently anoxic fjord, where annual or less frequent deep water renewal events abruptly alter geochemical stratification in the water column. We examined the potential of chemosynthetic bacteria to exploit productively the variable oxic-anoxic interface in the inlet. An intensive zone of water-column dark CO2 fixation was associated with the oxic-anoxlc interface, where rates of dark CO2 fixation up to 24 mgC m-3 d-' were recorded. This activity closely followed horizontal and seasonal developments in the oxiclanoxic interface. Extensive Beggiatoa-like bactenal mats, exceeding 100 ha in area, were observed by submersible on sediments below 105 m. The distribution of bacterial mats was also affected by deep-water stagnation and renewal. Physiologically-oriented investigations are now required to clarify the energetic basis for water-column dark CO2 fixation and bacterial-mat growth in Saanich Inlet, and thus confirm the significance of chemosynthesis in organic matter production.