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Closed Access item Effects of nutrients and light on periphyton biomass and nitrogen uptake in Mediterranean streams with contrasting land uses
|Authors:||Von Schiller, D.|
Riera, Joan L.
|Keywords:||Biofilm, Light, N uptake, Nutrients, Periphyton, Streams|
|Publisher:||John Wiley & Sons|
|Citation:||Freshwater Biology 52(5) : 891-906 (2007)|
|Abstract:||1. Nutrient diffusing substrata (NDS) were used to determine the relative importance of
nutrients and light as potential limiting factors of periphyton biomass and nitrogen (N)
uptake in Mediterranean streams subjected to different human impacts. The nutrients
examined were phosphorus (P) and N, and we also further differentiated between the
response of periphyton communities to N species (i.e. NO3-N and NH4-N). To examine the
effect of light and nutrients on periphyton biomass, chlorophyll a accrual rates on NDS
located at open and closed canopy sites were compared. The effect of nutrient availability
on periphyton uptake was measured by 15N changes on the NDS after NO3-15N short-term
2. Results show that light was the main factor affecting algal biomass in the study streams.
Algal biomass was in general higher at open than at closed canopy sites. Nutrient
availability, as simulated with the NDS experiments, did not enhance algal biomass
accrual in either of the 2 light conditions.
3. In the control treatments (i.e. ambient concentrations), periphyton NO3-N uptake rates
increased and C : N molar ratios decreased consistently with increases in N availability
across streams. NO3-N uptake rates were altered when ambient N concentrations were
increased artificially in the N amended NDS. Periphyton assemblages growing on N
enriched substrata seemed to preferentially take up N diffusing from the substratum
rather than N from the water column. This response differed among streams, and
depended on ambient N availability.
4. Periphyton biomass was not significantly different between substrata exposed to the two
forms of available N sources. Nonetheless, we found differences in the effects of both N
sources on the uptake of N from the water column. NH4-N seemed to be the preferred
source of N for periphyton growing on NDS.
5. Results suggest that the effect of riparian zones on light availability, although seldom
considered by water managers, may be more important than nutrients in controlling
eutrophication effects derived from human activities. Finally, our results confirm that not
only increases in concentration, but also stoichiometric imbalances should be considered
when examining N retention in human altered streams.|
|Description:||16 Páginas ; 5 Figuras ; 3 Tablas|
|Publisher version (URL):||http:dx.doi.org/10.1111/j.1365-2427.2007.01742.x|
|Appears in Collections:||(CEAB) Artículos|
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