Sunspots drive seagrasses

Abstract

Seagrasses are underwater flowering plants that form an important marine habitat worldwide. They respond to watershed and climate influences and are considered a good indicator of environmental health. Investigations into seagrass photosynthesis, response to high irradiance and UV light are providing new insights into controls on plant production. We show that the size and density of the intertidal seagrass directly relates to sunspot activity. The influence of sunspot activity has been largely overlooked in plants and never examined in seagrasses. The correlation between seagrass canopy height and the number of sunspots was highly significant, with height decreasing steadily as sunspots increase and recover only after a substantial decline in sunspot activity. The density of seagrass shoots correlated positively with sunspots until, at high sunspot numbers (>110 per month), plant density dropped and then rebounded. High sunspot activity inhibits the production and alters the meadow structure of tropical intertidal seagrass habitats.

Keywords:

• Halodule wrightii
• sunspot activity
• long-term monitoring
• seagrass

Acknowledgements

We thank those who helped with fieldwork during 14 years of monitoring, Dr Heitor Evangelista for comments which improved an earlier draft and Cathy Short for editing. J.C.C. received financial support from the Programa de Incentivo à Produção Científica, Técnica e Artística, UERJ and Conselho Nacional de Desenvolvimento Científico e Tecnológico and a grant from the Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro no E-25/170669/2004. L.V.M. gratefully acknowledges FAPERJ for providing a Doctoral fellowship (E-26/153.071/2006). F.T.S. received support from SeagrassNet, the New Hampshire Charitable Foundation and Tom Haas.