In-situ estimation of benthic marcoalgal primary production using a novel flow-through benthic incubation chamber system

To estimate primary production of macroalgal habitat, which is known as a key component for energy flow and biochemical cycle in coastal vegetation system, we developed a novel flow-through benthic incubation chamber system (ft-BICs) that enables to measure continuously in-situ areal productivity. The ft-BICs has the shape of truncated square pyramid with volume of 0.029 m³ and area of 0.25 m². To conduct the experiment we purposed, three algal chambers (ACs) were deployed to the locations of benthic habitat with transplanted macroalgae using 0.2025 m² quadrat, and one blank chamber (BC) was deployed with the condition without algal biomass as a control setting. During the experiment, seawaters were continuously flowed into the ft-BICs via the pump box (PB) with the rate of 2 L seawaters min^-1, and DO concentrations were measured with one-minute interval in the ACs, BC and PB. Thus, productivity of benthic macroalgal and microbial communities were estimated from the difference of DO concentrations between ACs and BC; BC and PB, respectively. Our results indicated that DO-based algal productivity was positive values during the times of morning and late afternoon, whereas negative values during the times of early afternoon and night. Daily net algal productivity was estimated to be 170.77 ± 55.01 mg O₂ m^-2 d^-1, and was much higher than the BC (12.68 ± 27.21 mg O₂ m^-2 d^-1). Finally, we support that the ft-BICs is a useful tool for estimation of in-situ benthic algal productivity.