Recovery Dynamics of the Seagrass Zostera marina Following Mass Mortalities from Two Extreme Climatic Events

A. J. Johnson, E. C. Shields, G. A. Kendrick, R. J. Orth

Research output: Contribution to journalArticle

Abstract

The marine angiosperm, Zostera marina, utilizes both asexual and sexual reproduction to grow, persist, and recover in dynamic environments. Sexual reproduction could be increasingly important for Z. marina population resilience to extreme weather events resulting from climate change. In the Chesapeake Bay, Virginia, a warming event in 2005 and unprecedented rainfall in combination with warming in 2018 led to large-scale Z. marina declines. We compare the survival and demographic characteristics of recovering Z. marina populations following these declines to identify the demographic mechanisms driving population recovery. Mean bottom cover in recovering populations was higher in 2019 than 2006, despite lower adult survival, because seedling abundance was significantly higher. Seedlings contributed significantly more to total shoot abundance than adult clones in 2019. Adult clone survival was lower in 2019 in regions that showed greater variation in temperature and salinity. Shifts in adult clone survival and seedling abundance in recovering populations in the Chesapeake Bay suggest that Z. marina has two complementary demographic mechanisms for recovery: the seed bank produced from the previous year’s flowering and the rapid growth and reproduction of surviving adults. The relevance of reproductive forms or life stages to recovering populations may depend on the severity of the decline in adult survival and the supply of propagules that could facilitate recovery. If climate change increases the frequency of extreme events in the Chesapeake Bay and elsewhere, perennial Z. marina populations may be increasingly dependent on the previous years’ flowering and recruitment from seed.

Original languageEnglish
JournalEstuaries and Coasts
DOIs
Publication statusE-pub ahead of print - 5 Aug 2020

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