Coralline photosynthetic physiology across a steep light gradient

• Published in: Photosynthesis research Vol. 153; no. 1-2; pp. 43 - 57
• Main Authors: Nguyen, Hang T. T., Pritchard, Daniel W., Desmond, Matthew J., Hepburn, Christopher D.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-08-2022; Springer; Springer Nature B.V
• Subjects: Acclimation; Algae; Arthrocardia; Biochemistry; Biomedical and Life Sciences; Coastal ecosystems; Ecosystem; Kelp - radiation effects; Kelp beds; Life Sciences; Light; Original Article; Photons; Photosynthesis; Photosynthesis - physiology; Photosynthetic pigments; Physiological aspects; Pigments; Plant Genetics and Genomics; Plant Physiology; Plant Sciences; Radiation measurement; Rhodophyta; Water; Pigment; Light dose; Photosynthesis vs. irradiance; Coralline algae; Depth
• ISSN: 0166-8595; 1573-5079
• DOI: 10.1007/s11120-022-00899-7

Coralline algae (CA) are globally distributed and fulfil many important roles within coastal ecosystems. In this study, photosynthetically active radiation (PAR) measured for 616 days at 2 and 10 m in a temperate subtidal kelp forest in southern New Zealand provided context to photosynthesis vs. irradiance relationships for, and pigment concentrations of, an articulated coralline alga,
Arthrocardia
sp. and a crustose coralline species assemblage within the Hapalidiales order. The maximum photosynthetic rate
P
max
of the
Arthrocardia
sp. (20.38 ± 2.38 µmol O
2
. gDW
−1
h
−1
) was significantly higher than the
P
max
of crustose coralline spp. (3.72 ± 0.74 µmol O
2
. gDW
−1
h
−1
) at the same 2 m stratum. Pigment concentration of
Arthrocardia
sp. was significantly higher than that of crustose coralline spp. at the same depth, while pigment concentration of crustose coralline spp. at 2 and 10 m were not significantly affected by depth. The photosynthetic characteristics of these coralline algae represent a shade acclimated organism with low saturation irradiance (all
E
k
 < 100 µmol photons m
−2
 s
−1
). Despite sevenfold difference in average daily dose between 2 and 10 m there was no significant effect of depth on the photosynthetic performance of crustose coralline algae measured. The lack of evidence for acclimation to low light could be because periods of clear water provide enough light to maintain photosynthesis, lower energetic requirements of species found at depth or constraints on the synthesis of photosynthetic pigments at greater depth.