Abstract
Understanding climate change impacts on benthic habitats is crucial to acknowledge their actual ecosystem functioning value. One pertinent way to achieve this is by measuring primary productivity. Accurately quantifying primary productivity in turbulent subtidal, rocky habitats, particularly those with high canopy forming seaweeds, such as kelp, 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 values of net primary production; 2) ex-situ incubations in the laboratory, in which the obtained values do not accurately represent the real production of a community; and 3) in-situ incubations on individual kelp fronds, neglecting community effects on the production. To address this issue, we describe a novel methodology – the Benthic Incubation Chamber (BIC) - designed to assess in-situ primary productivity of different benthic communities (high and low canopy). The method involves incubation chambers where total oxygen flux, temperature, and photo-synthetically active radiation (PAR) are simultaneously recorded. From those measurements, net community production (NCP) and community respiration (CR) for a given biomass and water volume were derived for the sampled area of each chamber. Results from Portuguese continental coast showed differences in NCP rates among different benthic communities and demonstrated the feasibility of this technique to obtain reliable in-situ net primary productivity values in a variety of subtidal habitats. This method contributes to a comprehensive approach to sustain and protect vital marine ecosystems, supporting biodiversity and addressing environmental issues like climate change.