Hj. Grimshaw et al., SHADING OF PERIPHYTON COMMUNITIES BY WETLAND EMERGENT MACROPHYTES - DECOUPLING OF ALGAL PHOTOSYNTHESIS FROM MICROBIAL NUTRIENT RETENTION, Archiv fur Hydrobiologie, 139(1), 1997, pp. 17-27
Relative net primary productivity (NPP) of periphyton communities in t
he Florida Everglades were determined and compared under emergent macr
ophyte canopies typical of enriched and unenriched Everglades habitats
. Photosynthetically active radiation (PAR) reaching the periphyton co
mmunities were reduced only by 35% in sawgrass (Cladium mariscus) habi
tats but by 85% or more in dense stands of cattail (Typha domingensis)
. Photosynthetic rates of periphytic algae and cyanobacteria in sawgra
ss habitats were about 70% of those in open water slough habitats. NPP
of periphytic communities within the cattail habitat was severely red
uced by 80 +/- 8 per cent of rates in the open communities. Greatly re
duced inorganic and organic P concentrations occurred in water of habi
tats with high periphytic photosynthesis, whereas inorganic and organi
c nitrogen concentrations were lower in the nutrient-enriched, more re
ducing cattail habitats. Putative causes for these observations are re
lated to the suppression of periphytic photosynthesis by macrophytic s
hading.