Spatial delineation of the depositional footprint of the Motueka River outwelling plume in Tasman Bay, New Zealand

Figures & data

Figure 1  Location of river outwelling plumes and major aquaculture development areas along the New Zealand coastline.

Figure 2  Sampling locations and aquaculture management areas in Tasman Bay. Site designations refer to geographic locations and mean water depth. Stippled polygons represent aquaculture management areas.

Figure 3  River margin sediment sampling locations (squares = main stem of the Motueka River, dots = tributaries) and suspended sediment sampling locations (triangles); u/s refers to upstream.

Figure 4  Monthly suspended sediment load at four sites in the Motueka catchment. See Fig. 2 for site locations.

Table 1  Specific sediment yield and sediment load estimates for four sampling sites in the Motueka catchment.

	Specific sediment yield (t/km^2/year)^a		Sediment load (t/year)		% of WB load
Site	Dec 02–Nov 09	Long-term^b	Dec 02–Nov 09	Long-term^b	Dec 02–Nov 09	Long-term
Motueka at WB	77	136	157,850	278,800	–	–
Wangapeka at WP	105	137	50,295	65,623	32	24
Motupiko at CB	140	110	14,756	11,594	9	4
Motueka at G	306	533	49,878	86,879	32	31
WB, Woodmans Bend; WP, Walter Peak; CB, Christies Bridge; G, Gorge. ^aQuoted as specific sediment yield to account for differences in catchment area. ^bDerived by applying event SY–Q p relationship to long-term discharge record at each site (1990–2009).

Figure 5  Particle size, gravel (>2 mm), sand (2–0.063 mm) and muds/fines (<0.063 mm), of Tasman Bay sediments.

Figure 6  Organic matter content (% ash free dry weight) in Tasman Bay sediments. Crosses refer to sampling sites.

Figure 7  Ni and Cr concentrations in river margin sediments from stations along the main stem Motueka River (grey bars) and tributaries (white bars). ISQG refers to interim sediment quality guidelines. See Fig. 3 for site locations 1–12.

Figure 8  Spatial patterns of: A, nickel; B, chromium; C, copper; D, barium; E, vanadium; F, aluminium; G, lead; H, strontium concentrations (mg/kg) in Tasman Bay sediments. Crosses refer to positions of sampling sites.

Figure 9  Spatial variation in: A, taxa richness; B, Shannon–Weiner diversity values; C, total abundance; and D, abundance of Heteromastus filiformis (grey bars) and Theora lubrica (white bars). Data are averages + standard error (n=5 cores).

Figure 10  Multi-dimensional scaling (MDS) ordination showing: A, similarity of sites based on their infaunal taxa composition (2D stress = 0.18, sites circled were ≥59% similar), and B–D, bubble plots indicating relative values for the most correlated (Spearman ρ-values) explanatory variables.

Figure 11  Depositional footprint of the Motueka River plume in Tasman Bay, based on trace metal and organic matter/Pb composites, and the mechanism of delivery of Ni- and Cr-enriched sediments from the upper catchment. The mineral belt region is not drawn to scale.