Effects of salinity on photosynthesis and respiration of the seagrass Zostera japonica: A comparison of two established populations in North America

Abstract

a b s t r a c tPhotosynthetic responses were quantified for two Zostera japonica Aschers. and Graebn. populations from the northern and southern limits of distribution exposed to a range of salinities along the Pacific Coast of North America. Plants were collected from Padilla Bay, Washington (northern) and Coos Bay, Oregon, USA (southern) and cultured together in experimental tanks at 3 salinities (5, 20 and 35) under saturating irradiance for 3 weeks. Subsequently, photosynthesis-irradiance (P vs. E curves) relationships for leaf segments from the two populations were assessed using an oxygen electrode system. We found no evidence for diel rhythms in either light saturated photosynthesis (P max ) or dark respiration (R d ). For the Padilla Bay population, P max ranged from 192 to 390 mol O 2 g DW −1 h −1 ; for the Coos Bay population P max ranged from 226 to 774 mol O 2 g DW −1 h −1 . Photosynthetic maxima of the Coos Bay plants occurred at a salinity of 20, whereas salinity had no effect on the photosynthetic maxima of the Padilla Bay plants. There were significant differences in leaf tissue R d among salinity treatments but the two populations responded similarly to salinity. North American populations of Z. japonica are best adapted to intermediate salinities, displaying minimum R d rates, lower compensation irradiance, higher saturation irradiance, and greater P max rates at a salinity of 20. Additionally, the southern population may be better adapted to southward expansion along the Pacific Coast and changes associated with global climate change.Published by Elsevier B.V.

Moderate Increase in TCO2 Enhances Photosynthesis of Seagrass Zostera japonica, but Not Zostera marina: Implications for Acidification Mitigation

“…This is the first time that a response in the photosynthetic rate of Z. japonica to TCO 2 has been documented, to our knowledge. Previous research has shown that Z. japonica photosynthesis is more sensitive to light and salinity (Shafer et al, 2011;Shafer and Kaldy, 2014) than is Z. marina photosynthesis (Hellblom and Björk, 1999;Shafer and Kaldy, 2014). Given that the two species appear to express different physiological response to environmental factors, it is likely that the utilization of TCO 2 would also be inherently different.…”

“…There have not been any published studies to our knowledge examining Z. japonica response to TCO 2 . Only a handful of studies have examined Z. japonica photosynthesis and physiology for populations established in the PNW (see Shafer et al, 2011;Shafer and Kaldy, 2014;Kaldy et al, 2015). Shafer and Kaldy (2014) found that Z. japonica local to the central Oregon coast has a substantially greater photosynthetic rate than Z. marina under the same chemical conditions.…”

“…While this study provides insight into the relative photosynthetic differences between the two species, a comprehensive understanding of variable TCO 2 and irradiance response is needed in order to determine how this difference drives OA mitigation potential. In addition, it is important to examine if the local adaptations that exist throughout a species' distribution (Backman, 1991 and references therein;Shafer et al, 2011) result in photosynthetic differences that are dissimilar between central Oregon and Salish Sea populations.…”

Coexistence between Zostera marina and Zostera japonica in seagrass beds of the Seto Inland Sea, Japan

“…The upper part of seagrass is affected by water turbulence, and the lower part is affected by photosynthesis inhibition (Dennison and Alberte 1985;Duarte 1991;Mach et al 2010;Kendrick et al 2002). The habitats of Z. marina and Z. japonica are affected by salinity and depth (Greve and Krausen-Jensen 2005;Morita et al 2010;Abe et al 2009;Shafer et al 2011). For example, in the summer, Z. marina growth becomes difficult when the daily mean water temperature is 28°C or more.…”

Comparison of non-native dwarf eelgrass (Zostera japonica) and native eelgrass (Zostera marina) distributions in a northeast Pacific estuary: 1997–2014

“…Harrison (1982) studied seasonal and annual variations of Z. japonica in lower British Columbia, Canada, and other studies of this species in PNW estuaries subsequently have been reported (below). In recent years a number of investigations of the occurrence and ecology of Z. japonica in Yaquina Estuary have been published , Larned 2003, Kaldy 2006, Almasi and Eldridge 2008, Young et al 2008, Shafer et al 2011, Kaldy and Shafer 2013.…”