Latitudinal patterns in European seagrass carbon reserves: Influence of seasonal fluctuations versus short-term stress and disturbance events

Laura M. Soissons*, Eeke P. Haanstra, Marieke M. van Katwijk, Ragnhild Asmus, Isabelle Auby, Laurent Barille, Fernando G. Brun, Patricia G. Cardoso, Nicolas Desroy, Jerome Fournier, Florian Ganthy, Joxe-Mikel Garmendia, Laurent Godet, Tiago F. Grilo, Petra Kadel, Barbara Ondiviela, Gloria Peralta, Araceli Puente, Maria Recio, Loic RigouinMireia Valle, Peter M. J. Herman, Tjeerd J. Bouma

*Corresponding author for this work

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Abstract

Seagrass meadows form highly productive and valuable ecosystems in the marine environment. Throughout the year, seagrass meadows are exposed to abiotic and biotic variations linked to (i) seasonal fluctuations, (ii) short-term stress events such as, e.g., local nutrient enrichment, and (iii) small-scale disturbances such as, e.g., biomass removal by grazing. We hypothesized that short-term stress events and small-scale disturbances may affect seagrass chance for survival in temperate latitudes. To test this hypothesis we focused on seagrass carbon reserves in the form of starch stored seasonally in rhizomes, as these have been defined as a good indicator for winter survival. Twelve Zostera noltei meadows were monitored along a latitudinal gradient in Western Europe to firstly assess the seasonal change of their rhizomal starch content. Secondly, we tested the effects of nutrient enrichment and/or biomass removal on the corresponding starch content by using a short-term manipulative field experiment at a single latitude in the Netherlands. At the end of the growing season, we observed a weak but significant linear increase of starch content along the latitudinal gradient from south to north. This agrees with the contention that such reserves are essential for regrowth after winter, which is more severe in the north. In addition, we also observed a weak but significant positive relationship between starch content at the beginning of the growing season and past winter temperatures. This implies a lower regrowth potential after severe winters, due to diminished starch content at the beginning of the growing season. Short-term stress and disturbances may intensify these patterns, because our manipulative experiments show that when nutrient enrichment and biomass loss co-occurred at the end of the growing season, Z. noltei starch content declined. In temperate zones, the capacity of seagrasses to accumulate carbon reserves is expected to determine carbon-based regrowth after winter. Therefore, processes affecting those reserves might affect seagrass resilience. With increasing human pressure on coastal systems, short- and small-scale stress events are expected to become more frequent, threatening the resilience of seagrass ecosystems, particularly at higher latitudes, where populations tend to have an annual cycle highly dependent on their storage capacity.
Original languageEnglish
Article number88
Number of pages12
JournalFrontiers in Plant Science
Volume9
DOIs
Publication statusPublished - 1-Feb-2018
Externally publishedYes

Keywords

  • carbon reserves
  • European Atlantic coast
  • latitude
  • resilience
  • Zostera noltei
  • climate setting
  • stress events
  • EELGRASS ZOSTERA-MARINA
  • NOLTII HORNEM
  • POSIDONIA-OCEANICA
  • CARBOHYDRATE RESERVES
  • RESOURCE-ALLOCATION
  • GROWTH DYNAMICS
  • CLIMATE-CHANGE
  • LIGHT
  • PHOTOSYNTHESIS
  • ECOSYSTEMS

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