Benthic Incubation Chamber (BIC) for in-situ assessment of primary productivity in different canopy-forming communities

Abstract

Accurately quantifying primary productivity in highly dynamic subtidal rocky habitats, particularly those with high canopy-forming macroalgae, is inherently challenging, leading to a scarcity of information. Kelp primary productivity has primarily been assessed through (1) quantification of carbon standing stock and biomass, which provides limited information on rates of primary productivity; (2) ex-situ incubations in the laboratory, in which the obtained values may not represent the actual productivity of a community; and (3) in-situ incubations in detached plants or including only the fronds. To address this issue, we describe a versatile methodology—the Benthic Incubation Chamber (BIC); and tested it along the morphologically diverse Portuguese continental coast. BIC is designed to assess in-situ primary productivity in a variety of benthic communities (high and low canopy), fulfilling the existing need to measure productivity in highly dynamic, shallow subtidal habitats. The method involves incubation chambers where total oxygen flux, temperature, and photosynthetically active radiation (PAR) are simultaneously recorded. From those measurements, Net Community Productivity (NCP) and community respiration (CR) for a given biomass and water volume were derived for each chamber. Incubations performed in the Portuguese continental coast demonstrated the feasibility of this technique to obtain reliable in-situ net primary productivity values in a range of subtidal habitats. This method contributes to a comprehensive approach to sustaining and protecting vital marine ecosystems, supporting biodiversity and addressing environmental issues.