Photosynthesis and growth in macroalgae: linking functional-form and power-scaling approaches

Abstract

Grouping species into functional-form groups and measuring directly their surface area to volume ratio are 2 common approaches to forecast primary production of marine macroalgae. A link between the functional-form model (FFM) and the power-scaling approach (PSA) for a wide variety of marine macroalgae has been attempted for the first time in the present work. To test both approaches, thalli of 44 species of marine benthic macroalgae were collected from intertidal zones adjacent to Cádiz Bay. Metabolic rates, tissue nutrient content, surface area to biomass ratio (SA/B) and specific growth rates were measured for these species. PSA slopes were close to 2/3 power for growth rate, while metabolic rates scaled very close to, or matched, 3/4 power. The FFM descriptive model provided similar results to the PSA when it was transformed to a numerical model through the SA/B ratio. Even though both models appear to be valid, the problems derived from species allocation into morphological groups, and other previous criticisms, make the direct use of SA/B ratios more suitable for representing primary production in macroalgal functional groups in numerical models of coastal ecosystems.KEY WORDS: Functional form · Cádiz Bay · Marine macroalgae · Photosynthesis · Primary production · Surface area to biomass ratio (SA/B) · Scaling · Specific thallus area Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 377: [113][114][115][116][117][118][119][120][121][122] 2009 depending on the study or even the researchers (Phillips et al. 1997); and (4) the use of categorical variables as morphological groups.A further approach is the use of power laws to describe the relationship between 2 biologically continuous variables. The most widely reported power law function in nature is the allometric law (Brown & West 2000, Niklas 1994, 2004:, where Y is an attribute (e.g. metabolic rate), Y 0 is the scaling coefficient, M is the body mass, and b is the scaling exponent. This relationship is applied for a broad range of physiological processes (e.g. photosynthesis, respiration, growth, etc.) over a range of organism sizes and types (Banse 1982, Raven & Kübler 2002, Reich et al. 2006. Thus, scaling relationships would make feasible the forecasting of the potential production of plant populations and the energy budget of an ecosystem when the size spectrum of organisms is known (Nielsen & Sand-Jensen 1990). Accordingly, the proposed metabolic theory of ecology (MTE;Brown et al. 2004) provides predictions of functional processes, as well as the responses of communities and ecosystems from thoroughly understood physiological principles governing the allometric scaling of organism metabolism.However, body size or biomass is often difficult to determine in macroalgae at an individual scale, because either they lack a fixed mature size or many macroalgae are colonial species. In such cases, alternative continuous measurable variables, such as the surface area to volume ratio (SA/V), the surfac...

Species richness of marine macrophytes is correlated to a wave exposure gradient

“…(2005). The functional forms of each species were determined by consensus based on morphological features and physiological traits (Littler & Littler 1980; de los Santos et al . 2009).…”

“…Sargassum and Undaria were representative of the thick‐leathery forms, Halimeda and Corallina were classified as jointed‐calcareous forms, and Lithophyllum and Valonia were considered crustose forms. There is some overlap among functional forms for the species we examined, which is not without debate (Padilla & Allen 2000; de los Santos et al . 2009).…”

“…The species were identified with names following Yoshida et al (2005). The functional forms of each species were determined by consensus based on morphological features and physiological traits (Littler & Littler 1980;de los Santos et al 2009). For example, Ulva-like species and delicate species, such as those from the genera Porphyra and Dictyota were categorized in the delicate sheet-like functional form group and genera from Cladophora and Ceramium were considered filamentous.…”

A unifying explanation for diverse metabolic scaling in animals and plants

“…Perhaps maintenance metabolism is volume‐related in plants, whereas growth‐related photosynthesis is more a function of fluxes of nutrients and solar energy across surfaces or through transport networks (see also ; cf . West et al , 1999 a ; de los Santos, Pérez‐Llloréns & Vergara, 2009; Koyama & Kikuzawa, 2009; but see Jin et al , 2008).…”

“…cf. West et al, 1999a;de los Santos, Pérez-Llloréns & Vergara, 2009;Koyama & Kikuzawa, 2009; but see Jin et al, 2008).…”