Premium
Heat stress of two tropical seagrass species during low tides – impact on underwater net photosynthesis, dark respiration and diel in situ internal aeration
Author(s) -
Pedersen Ole,
Colmer Timothy D.,
Borum Jens,
ZavalaPerez Andrea,
Kendrick Gary A.
Publication year - 2016
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13900
Subject(s) - diel vertical migration , seagrass , photosynthesis , q10 , respiration , aeration , shoot , biology , botany , oceanography , chemistry , ecology , habitat , geology
Summary Seagrasses grow submerged in aerated seawater but often in low O 2 sediments. Elevated temperatures and low O 2 are stress factors. Internal aeration was measured in two tropical seagrasses, Thalassia hemprichii and Enhalus acoroides , growing with extreme tides and diel temperature amplitudes. Temperature effects on net photosynthesis ( P N ) and dark respiration ( R D ) of leaves were evaluated. Daytime low tide was characterized by high p O 2 (54 kP a), pH (8.8) and temperature (38°C) in shallow pools. As P N was maximum at 33°C (9.1 and 7.2 μmol O 2 m −2 s −1 in T. hemprichii and E. acoroides , respectively), the high temperatures and reduced CO 2 would have diminished P N , whereas R D increased (Q 10 of 2.0–2.7) above that at 33°C (0.45 and 0.33 μmol O 2 m −2 s −1 , respectively). During night‐time low tides, O 2 declined resulting in shoot base anoxia in both species, but incoming water containing c . 20 kP a O 2 relieved the anoxia. Shoots exposed to 40°C for 4 h showed recovery of P N and R D , whereas 45°C resulted in leaf damage. These seagrasses are ‘living near the edge’, tolerant of current diel O 2 and temperature extremes, but if temperatures rise both species may be threatened in this habitat.