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Temperature trumps light: Teasing apart interactive factors controlling non-indigenous Zostera japonica growth
Citation:
KALDY, III, J. E. AND D. Shafer. Temperature trumps light: Teasing apart interactive factors controlling non-indigenous Zostera japonica growth. Presented at 41st Benthic Ecology Meeting, Norfold, VA, March 21 - 24, 2012.
Impact/Purpose:
In the Pacific Northwest Zostera marina and Z. japonica co-exist by occupying separate elevation niches.
Description:
In the Pacific Northwest Zostera marina and Z. japonica co-exist by occupying separate elevation niches. We conducted two mesocosm experiments to evaluate light and temperature as factors controlling the disjunct distribution of congeners. The first study tests the hypothesis that Z. japonica has higher light requirements than Z. marina by growing the plants in tanks at two different light levels. We evaluated photosynthetic parameters derived using O2 evolution techniques. Z. japonica maximum rates of photosynthesis were 3-6 times higher than Z. marina, while respiration rates were similar. Our data suggest Z. japonica should grow as deep as Z. marina. The second study tested the hypothesis that duration of temperature exposure affects growth. Potted Z. japonica plants were exposed to treatment temperatures for 2, 6, 12, or 24 h each day then returned to “ambient” conditions. Z. japonica growth was a function of exposure duration. Exposure to 8 ºC temperatures inhibited growth. Plants grew when exposed to sub-lethal temperature stress (32 ºC); however they did not grow as fast as under optimum temperatures (20 ºC). Pacific estuaries with extensive tidal flats or limited tidal exchange that promote water warming during transport may be prone to colonization and spread of Z. japonica.