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| Titel |
Technical Note: The effects of five different defaunation methods on biogeochemical properties of intertidal sediment |
| VerfasserIn |
T. J. Tolhurst, M. G. Chapman, A. J. Underwood, J. J. Cruz |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 9 ; Nr. 9, no. 9 (2012-09-24), S.3647-3661 |
| Datensatznummer |
250007293
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| Publikation (Nr.) |
 copernicus.org/bg-9-3647-2012.pdf |
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| Zusammenfassung |
Various methods have been used to remove organisms from sediments to
investigate structure and function of faunal assemblages in intertidal
habitats. Nevertheless, little is known about how these treatments affect
properties of the sediments themselves, although changing these properties
may cause changes in the assemblages, independently of other hypotheses
being tested. This study assesses the efficacy of defaunation and effect on
selected biogeochemical properties of five different methods of defaunating
soft muddy sediments in an estuary. The methods were removal and freezing
of sediment, removal and oven-heating, freezing in situ with liquid N2,
spraying with formalin and spraying with hydrogen peroxide. The first four
of these methods have been used in previous studies, whilst the fifth was
considered to be a potentially useful defaunator because it does not leave
toxic residues. The first two methods required sediment to be brought back
to the lab, disrupting the natural structure of the sediment; the last three
were done in situ, with much less disturbance.
Variables measured to assess effects of the treatments on the sediment were
amount of water, grain size, total carbohydrate, suspension index (relative
erosion rate), erosion threshold, chlorophyll a and b, colloidal
carbohydrate, Fo (minimal fluorescence) and
Fv / Fm (photosynthetic yield). There were no
significant effects of any treatment on the first four variables. For the
others, effects of defaunation varied from treatment to treatment and with
time after treatment. Generally, the greatest disturbance was to the
microphytobenthos (MPB, measured by chlorophyll and fluorescence) and related
variables. For most treatments, recovery was rapid, but the effects of
formalin and H2O2 persisted for a few days. Effects on physical
properties of the sediment were mostly minor and insignificant. Removal and
freezing or heating, however, caused major changes to the sediments because
of the disturbances involved. Choosing the appropriate method of defaunation
is very important if interpretations are not to be confounded between the
effects of defaunation per se and any effects of changes to other biota (such
as microphytobenthos) and/or the properties of sediments caused by the method
used to defaunate experimental areas. |
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