Meeting Abstract

S10.11  Wednesday, Jan. 6  Lessons learned about ecosystem function and biogenic structure from experimental work on seagrasses and macroalgae BELL, Susan*; MEYERS, Allison; THOMAS, Florence; Univ. of South Florida; Univ. of South Florida; Univ. of Hawaii sbell@cas.usf.edu

Seagrasses and rhizophytic macroalgae provide multiple ecosystem functions including provision of structure for fauna and epiphytes. However modification of the abiotic environment is also notable. Sediment trapping by canopies is well known. The modification of the abiotic environment by these marine plants may have positive or negative effects on other organisms and thus plants may act as ecological engineers. However it is important to establish whether such actions are consistent over larger temporal and spatial scales. We combined studies of underwater landscape change with field experiments to assess the impact of each of these plants on different measures of ecosystem function. Experiments showed that flow regimes within the canopy of these plants differed. Additionally, in field studies conducted using in situ flumes, nutrient uptake was distributed differently among the organisms in the two types of vegetation. Specifically in seagrass beds, epiphytes played a predominant role in removing nutrients from the water column; however, in areas dominated by algal beds, the macroalga was responsible for a large percentage of the whole community uptake. Additional studies revealed that even when seagrass density was held constant, sediment retention varied with hydrodynamic setting. Thus changing landscape composition of these plants within the same locale or the same plants operating within different hydrodynamic conditions can lead to modification of a variety of ecosystem processes. Such variation in time and space presents challenges to assessing the impacts of these potential ecological engineers.