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Interactive biology of two seagrasses, Zostera marina L. and Zostera japonica Aschers. & Graebn.

University of British Columbia

The two seagrasses Zostera marina L. and Zostera japonica Aschers. and Graebn. coexist in an intertidal region of the south-west coast of British Columbia. At the Roberts Bank study area three vegetation zones were identified; a seaward monospecific zone of Z. marina cover, a zone of mixed Z. marina and Z. japonica, and a landward monospecific zone of Z. japonica. The study investigating possible interactions between the two species was undertaken in three parts. First, a descriptive component compared numerous morphological characters, phenological data, and the population dynamics for each species between monospecific and mixed populations using univariate and multivariate statistical techniques. For both species shoots in deeper intertidal waters tended to be longer and with greater biomass than shoots from shallower intertidal areas. The most pronounced difference was the suppression of lateral shoot development of Z. japonica under a Z. marina canopy. Second, transplants of monospecific adult patches indicated that vigorous lateral branching would proceed regardless of location on the intertidal gradient and confirmed that the suppression of Z. japonica growth was due to competition. Third, a manipulation experiment using artificial shoots to mimic shading under a Z. marina canopy did not directly indicate that the attenuation of light under a Z. marina canopy was the mechanism for suppression of Z. japonica population growth. The artificial shoots did not adequately mimic Z. marina shoots as a shading canopy. In addition the "patch" design of the manipulation experiment enhanced lateral branching while reducing shoot length. The results of the manipulation experiment were therefore considered in conjunction with the results of the descriptive study and the transplant experiments.

Text

2010-08-22

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http://hdl.handle.net/2429/27606

Botany

University of British Columbia

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