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Comparing photophysiology of seagrasses in the Pacific Northwest: potential implications for species interactions
Citation:
Caudle, K., C. Brown, AND Jim Kaldy. Comparing photophysiology of seagrasses in the Pacific Northwest: potential implications for species interactions. Presented at Kansas Academy of Science, Emporia, KS, April 04 - 05, 2014.
Impact/Purpose:
Differences in photosynthetic temperature response between native eelgrass (Zostera marina) and non-native Japanese eelgrass (Z. japonica) suggest that plant fitness, as measured by the ratio of photosynthesis to respiration, varies with temperature conditions and may confer an advantage to the non-native species under some conditions. Photosynthesis and respiration were measured as part of ongoing experiments to quantify the response of marine macrophyte communities to nutrient loading under variable temperature conditions.
Description:
Physiological tolerances are a primary control on species interactions mediated through production and growth. We examined how the physiology of native eelgrass (Zostera marina L.) and introduced Japanese eelgrass (Z. japonica Aschers. & Graeb) responded to temperature in order to predict field interactions. Individual shoots of Z. marina and Z. japonica were collected from local populations in Yaquina Bay, Newport, OR. Photosynthesis (P) and dark respiration (Rd) were measured using oxygen flux methods at 10, 20, and 30 °C following a 5-10 minute acclimation period. Z. japonica P increased with temperature, while Z. marina P at 30 °C was significantly lower than Z. japonica. At 20 °C both species had similar P rates. Rd rates for both species increased with increased temperature. Although Rd was similar at 10 °C, Z. japonica Rd was significantly lower than Z. marina at both 20 and 30 °C. Differences observed in photosynthesis at these high water temperatures may be due to heat sensitive oxygen evolving proteins. The ratio of P:R may be related to plant fitness, with higher P:R indicating an advantage with respect to carbohydrate availability. At 10°C and 30 °C the differences in P:R between Z. japonica and Z. marina were not statistically significant. However at 20 °C Z. marina had a significantly higher P:R than Z. japonica. Differences in photosynthetic temperature response between Z. japonica and Z. marina suggest a mechanism to explain observed zonation patterns and provide insight on how estuarine plant communities may respond to increased water temperatures.