Growth and Photoacclimation Strategies of Three Zostera Species Along a Vertical Gradient: Implications for Seagrass Zonation Patterns

Sang Rul Park,Kyeonglim Moon,Kun-Seop Lee,Seung Hyeon Kim

doi:10.3389/fmars.2021.594779

Sang Rul Park, Kyeonglim Moon + Show 2 more

Open Access

https://doi.org/10.3389/fmars.2021.594779

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Abstract

Seagrasses typically display vertical zonation patterns in tropical and temperate areas. In East Asia, three Zostera species (Z. japonica, Z. marina, and Z. caespitosa) are distributed at different water depths, leading to zonation patterns from intertidal to subtidal zones. The present study aimed to determine whether these patterns could be explained by differences in their physiological responses, morphological traits, and meadows architecture caused by depth variations. Intertidal Zostera japonica had the lowest shoot height and blade width and the highest shoot density, while subtidal Z. caespitosa exhibited the largest specific leaf area. Total carotenoid content and the total chlorophyll/total carotenoid ratio were significantly higher in Z. japonica than in Z. marina or Z. caespitosa. The average carbon stable isotope (δ13C) values were significantly less negative in Z. caespitosa than in Z. marina and Z. japonica. The average maximum relative electron transport rate was higher for Z. marina than for Z. japonica and Z. caespitosa, while the maximum quantum yield values were higher for Z caespitosa than for Z. japonica and Z. marina. The non-photochemical quenching (NPQ) of Z. japonica extinguished within 5-min following the rapid light curve, indicating that most of its NPQ was energy-dependent quenching (qE). The rapid light curve (RLC) parameters and leaf relaxation after RLC showed that Z. japonica is a high-light adapted species and Z. caespitosa is a low-light adapted one. Additionally, Z. caespitosa showed the lowest dark respiration values and Z. japonica, the highest, suggesting that Z. caespitosa can survive with low photosynthetic activity. These results suggested that interspecific variations in the morphological and physiological characteristics, photosynthetic pigments, and meadows architecture of three Zostera species were associated with vertical zonation patterns and likely explain their patterns.

Highlights

Seagrasses are a specialized group of flowering plants adapted to marine environments and play crucial functional and structural roles in estuarine and coastal ecosystems (Kuo and McComb, 1989; Orth et al, 2006)
Zostera caespitosa meadows were never exposed to air, while Z. japonica and Z. marina were exposed to air for approximately bout 2.5 and 0.5 h per day, respectively (Figure 2B)
Sheath length, and leaf width of Z. marina and Z. caespitosa increased during spring and decreased during fall, while those of Z. japonica were lowest during February–April, when the duration of air exposure was longest

Summary

Introduction

Seagrasses are a specialized group of flowering plants adapted to marine environments and play crucial functional and structural roles in estuarine and coastal ecosystems (Kuo and McComb, 1989; Orth et al, 2006). They provide food and shelter that support the productivity and biomasses of commercially important fish species (Hemminga and Duarte, 2000; Beck et al, 2001; Short et al, 2007). Climate change greatly accelerates environmental changes and, causes considerable changes in seagrass distributions (Duarte et al, 2018). Understanding how seagrass species respond to environmental changes is critical for developing effective strategies to protect seagrass beds

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