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ABUNDANCE OF SEAGRASS (ZOSTERA MARINA L.) AND MACROALGAE IN RELATION TO THE SALINITY-TEMPERATURE GRADIENT IN YAQUINA BAY, OREGON, USA
Citation:
Kentula, M E. AND T H. DeWitt. ABUNDANCE OF SEAGRASS (ZOSTERA MARINA L.) AND MACROALGAE IN RELATION TO THE SALINITY-TEMPERATURE GRADIENT IN YAQUINA BAY, OREGON, USA. ESTUARIES. Estuarine Research Federation, Port Republic, MD, 26(4B):1130-1141, (2003).
Description:
The distribution and abundance of the seagrass, Zostera marina, and the associated macroalgae are described for Yaquina Bay, Oregon, U.S.A. Possible relationships between plant abundance and physical-chemical characteristics of the water column were also explored. Study sites were established in each of three zones in the estuary defined by temperature and salinity and were sampled monthly during day-time low tides from June through September 1998 and in July 1999. Zostera and macroalgal cover and Zostera shoot density were measured in 0.25-m-2 quadrats along transects placed to represent the bed in 1998 and randomly in 1999. After cover estimates and shoot counts were made, plant material was harvested and transported to the lab for determination of Zostera and macroalgal biomass. Water column variables were measured from stations near each study site and composited on a depth-averaged, monthly basis for each zone. Both Zostera and green macroalgal distribution and abundance differed between zones, over the summer in 1998, and between years. Seasonal patterns were most obvious for Zostera in Zone I (closest to the ocean) while the pattern in macroalgal abundance suggested a bloom moving up river. The physical-chemical characteristics of the zones differed with the season and could be related to the patterns in plant abundance. In particular, salinity was significantly correlated with Zostera abundance, while abundance of both types of plants were related to the variables describing aspects of light availability. Zostera biomass ranged from 19 - 104 g dry weight m-2; green macroalgae, from 5 - 180 g dry weight m-2. The biomass of the green macroalgae at a site can equal or exceed that of the Z. marina suggesting the potential for "nuisance" algal blooms.