WAMSI 2 - Dredging Node - Project 5.5.3 - Defining thresholds and indicators of primary producers - Seagrass pressure-response relationships - Experiment 3

Author Identifiers

Kathryn McMahon


Paul S. Lavery


Collection Type


Upload Date


School or Research Centre

School of Science


Western Australian Marine Science Institution


The DSP indicated that an area of uncertainty was whether the type of sediment {organic v inorganic and mean grain size) affected the response of plants to sediment deposition. Organic sediment are known to have a greater impact on corals than inorganic sediment, and it is possible that grain size and organic content could alter the effects of sediment deposition on sediment biogeochemistry, which in turn could affect seagrasses. To test for an effect of sediment type, additional laboratory and field experiment will be conducted in which the sediment composition is manipulated.

Laboratory treatments will be established as in Experiment 2 and subjected to the following treatments: Burial (0.2, 2 cm and 4 cm); sediment Type (fine inorganic, coarse inorganic and organic), and for 3 durations (2, 4 and 8 weeks plus 4 weeks recovery). Grain sizes and durations will be refined following input from Theme 2/3. Four replicate plots of each treatment will be established and the variable indicated in Table I measured at each sampling point. In the laboratory, sediment will be added to treatments as suspended sediment delivered in the water stream feeding the tanks. Feed will be provided at a rate that produces increases in sediment depth comparable to those observed in field situation (as determined in Project 5.1 and from Themes 2 and 3). This will provide loading of sediment to the plant canopy (e.g. material deposited on leaf surfaces) as well as the sediment surface, more representative of a dredging scenario.

An analogous experiment will be conducted in the field to validate the laboratory findings under conditions where sediment re-suspension and other factors may alter the plant responses. In this case, sediment will be added in either one, or a small number of sequential, loading events. Otherwise, the field experiment will follow the same design as that in Experiment 2, and varying the composition of sediment (as above). Variable to be measured are indicated in thumbnail image.

Geographic Bounding:

North bound: -11.00000, West bound: 115.00000, East bound: 126.00000, South bound: -21.00000.

North bound West bound East bound South bound

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This work is licensed under a Creative Commons Attribution 2.5 Australia License.