Implications of rising temperatures for gametophyte performance of two kelp species from Arctic waters

Abstract

<jats:title>Abstract</jats:title> <jats:p>The aim of this study was to determine the temperature effects on photosynthesis, growth and reproduction in gametophytes of <jats:italic>Alaria esculenta</jats:italic> (Linnaeus) Greville and <jats:italic>Saccharina latissima</jats:italic> (Linnaeus) C.E. Lane, C. Mayes, Druehl <jats:italic>et</jats:italic> G.W. Saunders from the Artic waters. After 24 days of culture, no gametophytes of either species survived at 20°C. Most growth parameters were greater at 10–15°C than at 5°C. Length and width were similar for both species, but area was greater for <jats:italic>A. esculenta</jats:italic> and cell number was greater for <jats:italic>S. latissima</jats:italic>. Female gametophytes were larger than male gametophytes in width and area, but the opposite was observed in cell number. In <jats:italic>A. esculenta</jats:italic>, but not for <jats:italic>S. latissima</jats:italic>, the percentage of female gametophytes decreased with increasing temperature. <jats:italic>Alaria esculenta</jats:italic> female gametophytes produced more sporophytes at 5°C than at 10°C, with no sporophytes at 15°C. In <jats:italic>S. latissima</jats:italic>, all female gametophytes produced sporophytes at both 5°C and 10°C, with a small percentage of sporophytes at 15°C. <jats:italic>Saccharina latissima</jats:italic> still had a measurable F<jats:sub>v</jats:sub>/F<jats:sub>m</jats:sub> at 20°C, while the F<jats:sub>v</jats:sub>/F<jats:sub>m</jats:sub> of <jats:italic>A. esculenta</jats:italic> was zero at this temperature. Maximum relative electron transport rate (rETR<jats:sub>max</jats:sub>) and non-photochemical quenching (NPQ) were constant in the male and female gametophytes of <jats:italic>A. esculenta</jats:italic> and the male gametophytes of <jats:italic>S. latissima</jats:italic> at temperatures between 5°C and 15°C. Photosynthesis was saturated at a higher irradiance in <jats:italic>A. esculenta</jats:italic> than in <jats:italic>S. latissima</jats:italic>.</jats:p>