Effects of kelp canopy on underwater light climate and viability of brwon algal spores in Kongsfjorden (Spitsbergen)


Contact
philipp.laeseke [ at ] uni-bremen.de

Abstract

Spores represent the most vulnerable life history stage of kelps. While UV-induced inhibition of spore germination has been readily documented, the impact of in situ underwater radiation below kelp canopies has been largely overlooked. We determined spectral composition and intensity of underwater radiation along a density gradient in an Alaria esculenta kelp forest at 3 m depth in Kongsfjorden, Svalbard. Accordingly, we set up a laboratory experiment simulating five different radiation conditions corresponding to irradiances under very dense to no canopy cover on a cloudless summer day. Spore responses (photosynthetic quantum yield, pigment and phlorotannin contents, swimming activity, and germination success) were determined after 4, 8, 16, and 24 h of exposure. In situ spectral radiation composition differed strongly from conditions applied in previous studies, which underestimated photosynthetically active radiation and overestimated UV-radiation effects. Furthermore, spore solutions differed significantly in quantum yield, pigment, and phlorotannin contents upon release. Nevertheless, spores reacted dynamically to different radiation conditions and exposure times. Highest radiation (PAR 61.8 W m−2, 1.9 W m−2 UVA, 0.01 W m−2 UVB) caused photodamage after exposure for ≥ 8 h, while intermediate radiation led to photoinhibition. Lowest radiation (PAR 0.23 W m−2, 0 W m−2 UVA, 0 W m−2 UVB) caused inconsistent reactions. There was a reduction of absolute pigment content in all treatments, but reduction rates of photosynthetic pigments were significantly different between radiation treatments. Soluble phlorotannin content decreased under all conditions but was not significantly affected by experimental conditions. High radiation reduced swimming activity of spores, but experimental conditions had almost no effect on germination success. Consequently, it seems unlikely that in situ radiation conditions negatively affect spores in present and future radiation scenarios.



Item Type
Article
Authors
Divisions
Primary Division
Programs
Primary Topic
Peer revision
ISI/Scopus peer-reviewed
Publication Status
Published
Eprint ID
49925
DOI 10.1007/s00300-019-02537-w

Cite as
Laeseke, P. , Bartsch, I. and Bischof, K. (2019): Effects of kelp canopy on underwater light climate and viability of brwon algal spores in Kongsfjorden (Spitsbergen) , Polar Biology, 42 , pp. 1511-1527 . doi: 10.1007/s00300-019-02537-w


Download
[img]
Preview
PDF
Laeseke_et_al-2019-Polar_Biology.pdf

Download (1MB) | Preview

Share


Citation

Research Platforms

Campaigns


Actions
Edit Item Edit Item