Changes in metabolic rates under fluctuating salinity regimes for two subtidal estuarine habitats |
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| Authors: | Charles N Farris Candace A Oviatt |
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| Institution: | 1. Cape Cod National Seashore, 99 Marconi Site Road, 02667, Wellfleet, Massachusetts
2. Graduate School of Oceanography, University of Rhode Island, South Ferry Road, 02882, Narragansett, Rhode Island
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| Abstract: | The metabolic rate of individual habitats can differ significantly in their contribution to the total system productivity of estuaries. Changing environmental conditions such as those created by tidal exchange can frequently alter these rates. In an effort to quantify these rate responses, metabolic rates were measured for macroalgal and sediment habitats at different salinities. Microcosms representing the two habitats were incubated at three salinity ranges (high: 25 to 31‰; moderate: 12 to 18‰; and low: 0 to 4‰) and production and respiration rates were estimated. The production rates for both habitats were proportional to the salinity of the water in the incubation, with the lowest metabolic rates associated with the lowest salinity. Average macroalgal habitat net production rates were 879 mg O2 m?2 h?1, 609 mg O2 m?2 h?1, and 451 mg O2 m?2 h?1 at high, moderate, and low salinity treatments, respectively, and the dark respiration rates were ?401 mg O2 m?2 h?1, ?341 mg O2 m?2 h?1, and ?333 mg O2 m?2 h?1. Average sediment habitat net production rates were 60 mg O2 m?2 h?1, 13 mg O2 m?2 h?1 and 10 mg O2 m?2 h?1 and the respiration rates were ?114 mg O2 m?2 h?1, ?55 mg O2 m?2 h?1, and ?31 mg O2 m?2 h?1 at high, moderate, and low salinity treatments. The larger contribution of macroalgal habitats to system metabolism may account for observed diurnal changes in water column oxygen levels in some estuaries. Macroalgal production rates explained 83% of the increase in water column oxygen levels during daylight hours and macroalgal respiration rates explained 65% of the decline in oxygen levels during the night. The contribution of macroalgal metabolism to the system can be influenced by even short-term changes in water column salinity. Environmental processes that alter salinity levels on hourly time scales may moderate the effect of macroalgal metabolism on oxygen levels. |
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