Abstract
An understanding of the nature of scale-dependence in macroalgal production and to quantify how primary production is incorporated into autotrophic biomass requires an assessment of primary production at multiple scales. In this study we experimentally estimated seasonal variability in individual photosynthesis, community production and growth in biomass of the charophyteChara asperain the Baltic Sea together with the key environmental variables known to regulate the production of macroalgae. The experiments suggested that the production and growth ofC. asperawas defined largely by light and temperature at all studied scales. However, the algal production at the same light levels was systematically lower at the community than an individual level, suggesting the importance of shelf-shading and below-ground processes in natural plant assemblages. Moreover, the observation scale also defined response types between the environment, plant production and growth. This implies that the patterns of variability of the production and growth of macrophytes should always be interpreted in the context of scale and any multiscale model development should involve experimental validation at all important scales.
Highlights
Primary production is important to all ecosystems as it supplies energy to other living organisms, thereby forming the foundation of food webs
In this study we experimentally quantified seasonal variability in individual photosynthesis, community production and growth in biomass of the charophyte C. aspera in the Baltic Sea along with the key environmental variables that are known to determine the production of macroalgae
We found that temperature and light availability were the best overall predictors of the production of C. aspera, followed by macroalgal coverage, flow velocity and water level
Summary
Primary production is important to all ecosystems as it supplies energy to other living organisms, thereby forming the foundation of food webs. Understanding the nature of scale-dependence in macroalgal production can help to elucidate some of the possible controls by which primary production is incorporated into autotrophic biomass Despite this importance, knowledge of such controls is limited as few studies have been undertaken to date that quantify the patterns of macroalgal production at different scales with most being performed under laboratory conditions (e.g., de los Santos et al, 2000; Israel and Hophy, 2002; Binzer and Middelboe, 2005; Pärnoja et al, 2014; Kim et al, 2016). Due to artificially induced conditions, as well as the use of separate phytoelements (thallus pieces, leaves), laboratory incubations often fail to characterize primary production to that which occurs in nature (Binzer and Middelboe, 2005; Binzer et al, 2006)
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