An in situ substratum fertilization technique: Diatom colonization on nutrient-enriched sand substrata.
Abstract: Using
an in situ substratum enrichment method, we assessed the effects of
nutrient release from sand substrata on the community structure of
attached diatoms in a sand-bottomed, northern Michigan stream. Sand
from the stream bottom was washed, sterilized, and then consolidated
into small plastic petri dishes with agar solutions enriched with
various concentrations of NaNO3 and KH2PO4.
Laboratory estimates of
nutrient release rates were performed over a 144-h period with
uncolonized substrata having different agar and nutrient
concentrations. Release rates decreased 10-fold in an exponential
fashion with no significant differences between replicates. Agar
concentrations had no significant effect on release rates, although the
rates were proportional to nutrient concentrations in the substratum.
Racks of substrata were installed parallel to the stream current flow
and retrieved after a 6-wk colonization period. Using multiple
comparisons of treatment means for both nutrients and algal taxa, we
found no differences between control and NO3
enrichments; significant
differences were found, however, between PO4 and
NO3+PO4 (N:P = 25:1)
treatment means relative to each other and the control. Diatom
biovolume was two times as great on PO4
treatments and four times
greater on NO3+PO4
treatments. Effects of PO4
and NO3 enrichment appear
to be taxa specific, with PO4 and NO3+PO4
treatments favoring Navicula
and Nitzschia
spp.
Control and NO3 treatments were dominated by Cocconeis placentula
Ehr. and Achnanthes
minutissima Kutz.
Pringle, C.M., and J. Bowers. 1984. An in situ substratum fertilization technique: Diatom colonization on nutrient-enriched sand substrata. Canadian Journal of Fisheries and Aquatic Sciences 41: 1247-1251.
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