Abiotic modulation of Spartina maritima photobiology in different latitudinal populations B. Duarte a, * , T. Couto b , J. Freitas a , J. Valentim c , H. Silva d , J.C. Marques b , J.M. Dias c , I. Caçador a a Centre of Oceanography of the Faculty of Sciences of the University of Lisbon (CO), Campo Grande 1749-016 Lisbon, Portugal b Institute of Marine Research e Marine and Environment Research Centre (IMAR-CMA), c/o Department of Zoology, Faculty of Sciences and Technology, University of Coimbra, 3000 Coimbra, Portugal c Physics Department & Centre for Environmental and Marine Studies (CESAM), University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal d Biology Department & Centre for Environmental and Marine Studies (CESAM), University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal article info Article history: Received 9 October 2012 Accepted 6 February 2013 Available online xxx Keywords: halophyte pigments photosynthetic efficiency climate abstract Spartina maritima has a very wide distribution in the northern hemisphere salt marshes crossing a wide variety of climatic environments. Therefore, it is not strange that some differences arise when observing the photosynthetic mechanisms of different populations inhabiting different latitudes. During this study it could be observed that climate is the most important factor controlling the photosynthetic traits of different populations distributed along a climatic gradient, namely the air temperature, humidity and light environment. Also some sediment physicochemical parameters such as pH and pore water salinity showed important influences driving the photosynthetic mechanisms in S. maritima. Furthermore S. maritima is one of the most abundant halophytes colonizing the Portuguese salt marshes. These facts have greater importance if one considers the large abundance of this halophytic species and how climate change will affect their metabolism and thus the ecosystem services provided by this species to the estuarine system. Ó 2013 Elsevier Ltd. All rights reserved. Salt marsh vegetation has a wide geographic distribution due, not only to its long-distance dispersal, but also to the similarities between salt marsh environments around the globe (Adam, 2002). Although these similarities, the key abiotic factors (for e.g. salinity, radiation, air temperature and humidity) affecting these ecosys- tems have a latitudinal gradient, even at small scales (Pennings et al., 2002). In this context, halophytes with a wide latitudinal distribution are likely to show intra-specific differences between partially and totally isolated populations (Àlvarez et al., 2010). Genetic differentiation among populations within a plant species is well documented, with certain populations being better adapted than others to specific environmental stressors (Keeley, 1979; Silander and Antonovics, 1979; Davies and Singh, 1983; Chung, 1989). This natural genetic variation provides the potential for se- lection of plant populations exhibiting improved stress tolerance. The Spartina genus is one of the more successful halophytes, being present in a wide range of latitudes across the globe. Some works have already described latitudinal population differentiation of Spartina species (Lessmann et al., 1997; Daehler et al., 1999; Otero et al., 2000; Seliskar et al., 2002; Proffitt et al., 2005; Álvarez et al., 2010). The members of the Spartina genus have C4 photo- synthesis using phosphoenolpyruvate carboxylase (PEPC) to concentrate CO 2 at higher amounts than it would be observed in a C3 organism (Hatch, 1992; Álvarez et al., 2010). Although this metabolic advantage PEPC is controlled by light-dependent phos- phorylation (Echevarría et al., 1990; Vidal et al., 1996), making it very dependent on the surrounding climatic environment. Differ- ences are likely to be found since leaves have high sensitivity to environmental pressures, such as climatic variations, contaminants and grazing (Heide, 2005; Stephenson et al. 2006). In addition, the activation of PEPC by its specific kinase is poor in low light (Bailey et al. 2007) and at low temperatures (Lara et al. 2001), both of which abiotic factors change with latitude. Spartina maritima (Curtis) Fernald, has a very wide distribution in the northern hemisphere native to the coasts of western and northern Europe and western Africa, with also a disjunct popula- tion on the Atlantic coasts of Namibia and South Africa (Marchant and Goodman, 1969). Recently, it has been withdrawing from several salt marshes either due to dieback or to hybridization with other Spartina species, originating polyploid species (Ainouche et al., 2003). The study described in this paper aimed to identify the differ- ences in the seasonal photobiological traits (PSII photochemistry * Corresponding author. E-mail address: baduarte@fc.ul.pt (B. Duarte). Contents lists available at SciVerse ScienceDirect Estuarine, Coastal and Shelf Science journal homepage: www.elsevier.com/locate/ecss 0272-7714/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ecss.2013.02.008 Estuarine, Coastal and Shelf Science xxx (2013) 1e11 Please cite this article in press as: Duarte, B., et al., Abiotic modulation of Spartina maritima photobiology in different latitudinal populations, Estuarine, Coastal and Shelf Science (2013), http://dx.doi.org/10.1016/j.ecss.2013.02.008