Depth-related variability in the photobiology of two populations of Halophila johnsonii and Halophila decipiens

The threatened seagrass Halophila johnsonii Eiseman coexists subtidally with H. decipiens Ostenfeld in southeastern Florida, but only H. johnsonii also occurs intertidally. Pulse amplitude modulated fluorometry and fiber-optic spectrometry were used to investigate the photobiology of two populations...

Full description

Saved in:
Bibliographic Details
Published in:Marine biology 2003-06, Vol.142 (6), p.1219-1228
Main Authors: DURAKO, M. J, KUNZELMAN, J. I, KENWORTHY, W. J, HAMMERSTROM, K. K
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
Autoecology
Biological and medical sciences
Fundamental and applied biological sciences. Psychology
Genetic diversity
Habitats
Halophila decipiens
Halophila johnsonii
Marine
Marine biology
Photosynthesis
Plant populations
Plants and fungi
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The threatened seagrass Halophila johnsonii Eiseman coexists subtidally with H. decipiens Ostenfeld in southeastern Florida, but only H. johnsonii also occurs intertidally. Pulse amplitude modulated fluorometry and fiber-optic spectrometry were used to investigate the photobiology of two populations of H. johnsonii and H. decipiens in an attempt to explain these distribution patterns. Maximum photosynthetic quantum yields (Fv/Fm) were measured in situ as a function of depth distribution within, and between, these two species at two sites (Jupiter Sound, 26 degrees 57'N; 80 degrees 04'W, and northern Biscayne Bay, 25 degrees 55'N; 80 degrees 07'W) along the east coast of Florida, USA, during 6-10 March 2001. Reciprocal transplants at the northern site were used to evaluate the plasticity of photosynthetic patterns and pigment absorption spectra and to gain insights into the mechanisms responsible for variations in the observed depth-distribution patterns. Subtidal-population Fv/Fm values were generally higher for H. johnsonii than for H. decipiens, at both sites. At the northern site, intertidal H. johnsonii had significantly lower Fv/Fm (0.494+/-0.138) than both subtidal H. johnsonii (0.696+/-0.045) and subtidal H. decipiens (0.668+/-0.048). In contrast, at the southern site intertidal H. johnsonii had the highest Fv/Fm (0.663+/-0.047) and were the largest plants. Fv/Fm values of subtidal plants of both species decreased when they were transplanted into shallow, intertidal beds. Correspondingly, Fv/Fm increased for intertidal H. johnsonii transplanted into the subtidal, 2 m deep beds. Rapid light curves indicated that H. decipiens had lower maximum relative electron transport rates (RETRmax) than did H. johnsonii. In addition, the onset of photoinhibition occurred at lower irradiances for H. decipiens (537-820 micromol photons m-2 s-1) compared to H. johnsonii (1141-2670 micromol photons m-2 s-1). RETRmax values decreased for intertidal H. johnsonii transplanted into subtidal beds, but they increased for both species when transplanted from subtidal to intertidal beds. Absorption spectra for the acetone-soluble leaf pigments of intertidal H. johnsonii exhibited a dominant peak near 345 nm; this UV peak was 30% lower for subtidal plants. Pigment absorption spectra for H. decipiens lacked the 345 nm peak and absorbances, normalized to leaf pairs, were lower across the spectrum. Our results indicate that photosynthetic tolerance to higher irradiances and prese
ISSN:0025-3162
1432-1793
DOI:10.1007/s00227-003-1038-3