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

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.info:eu-repo/semantics/publishedVersio

Photosynthetic and morphological photoacclimation of the seagrass Cymodocea nodosa to season, depth and leaf position

The photoacclimation capacity of the seagrass Cymodocea nodosa was evaluated considering temporal (i.e. seasonal) and spatial (i.e. depth and within-leaf position) factors of variation. Changes along the leaf were measured in a population growing along a depth gradient (from intertidal to subtidal) in Cadiz Bay (Southern Spain) from 2004 to 2005. Photoacclimation was evaluated by photosynthesis (P–E curves), pigment content and leaf morphology. Plants of Cymodocea nodosa showed large physiological and morphological plasticity (mean %CV = 35.8 ± 3.4) according to the three factors considered. Seasonal patterns appeared for photosynthesis, respiration, pigment content and morphology. Nevertheless, seasonal patterns were not consistent with depth or leaf portions. The resulting data set offered different information depending on the analysis conducted; when only one factor (season, depth or leaf portion) was considered, some tendencies observed in the 3-way full design were masked. Accordingly, considering spatio–temporal variability is crucial when describing photoacclimation and estimating productivity in seagrass meadows

Pieter Hendrik Nienhuis: aquatic ecologist and environmental scientist

Prof. Dr. Pieter Hendrik (Piet) Nienhuis worked for almost 40 years in all aspects of aquatic ecology and environmental science and retired on 31 October 2003. He can be characterised as a distinguished scientist, shaped in an applied estuarine and aquatic research ambience of the former Delta Institute for Hydrobiological Research (DIHO) in Yerseke in the Netherlands. His appointment as a full professor at the Radboud University Nijmegen offered him a challenging step from monodisciplinarity in ecology, via multidisciplinarity in the application of ecological knowledge in river science to interdisciplinarity in environmental science and management. This paper describes his education, teaching activities, research, scientific publications, science management, and significance for various scientific disciplines. He made important contributions to biosystematics of angiosperms and algae, the ecology of seagrasses, nutrient cycling and eutrophication in estuarine ecosystems, and the integrated modelling of the ecological functioning of estuaries. Subsequently, he paid much attention to environmental problems in river basins, ecological rehabilitation and sustainable development. His work influenced the view of ecologists, aquatic scientists and water managers in the Netherlands as well as abroad, in particular regarding the drawbacks of compartmentalization of the estuaries and the importance of connectivity and morphodynamics in river systems. In hindsight, it appears as a logical line that he gradually moved from estuarine ecological research that became increasingly driven by societal and environmental problems to the field of environmental science and management. [KEYWORDS: coastal zone management ; estuarine ecology ; environmental sciences ; interdisciplinary research ; river basin management ; river ecology]