Figure 1.
Location maps of the +Fe and HNLC sites with respect to:
a. monthly (October 1998) SeaWiFS chlorophyll (mg m−3) distribution, showing a typical spring bloom to the north of the Crozet Plateau (adapted from Ref. 15), with the meander of the Sub-Antarctic Front indicated by parallel black lines. b. Water depth (km) in the corresponding Crozet region (derived from the General Bathymetric Chart of the Oceans, Centenary Edition).
Table 1.
Details of selected scientific deployments at +Fe and HNLC sites around the Crozet Plateau.
Figure 2.
Carbon fluxes determined over a period of ∼12 months in 2005 at the Crozet Plateau (see also Ref. 12): a. the +Fe site at 3183 m water depth b. the HNLC site at 3195 m water depth.
Both ∼1000 m above the seabed. Bar widths are proportional to cup opening times of the Parflux sediment traps. Bar heights represent the material supplied over the period of cup opening.
Figure 3.
Lipid fluxes at the Crozet abyssal locations, +Fe and HNLC at 3195 and 3183 m water depth in 2005.
Labile lipids: Polyunsaturated fatty acids (PUFA), monounsaturated fatty acids (MUFA) and unsaturated alkanols (U-ALK); Semi-labile lipids: Saturated fatty acids (FA), branched fatty acids (Br-FA) and n-alkanols (ALK); Refractory lipids: Sterols (STER) and other lipids including branched alkanols, triterpenoids, steroidal ketones, phytol derivatives and alkenones (OLIP).
Figure 4.
Seabed seafloor mosaic from WASP photographic images of:
a. & b. the +Fe site, showing substantial cover of phytodetritus patches, which are clearly visible and appear green. c. & d. for comparison the HNLC site, where there is no phytodetritus but faecal casts are visible. In each case the swath width is c. 1.2 m and the total along track distance shown is approximately 2 m. (Total area illustrated c. 20 m2).
Table 2.
Total organic carbon (TOC), mean molar C/N, chlorophyll a and lipid concentrations (mg g−1 TOC) and ratio of chlorophyll a to pheopigments (Chl/P) in surface sediments (0–5 mm) and in sPOM at the Crozet islands abyssal locations, +Fe and HNLC at ∼4200 m.
Table 3.
The abundance and biomass (wet weight) of the dominant megafaunal invertebrates at abyssal sites around the Crozet Plateau.
Figure 5.
Variation in holothurian species composition between +Fe and HNLC sites.
a. Dendrogram representation using group-average clustering. Based on trawl (A–F) catch data standardized to area fished, subject to log(x+1) transformation and assessed with Bray-Curtis similarity coefficient. b. Non-metric multidimensional scaling ordination plot (ordination stress = 0) for the same data.
Figure 6.
Fresh wet weight biomass composition of the megabenthos at Crozet (HNLC, +Fe) and the NE Atlantic Porcupine Abyssal Plain (PAP) sites.
A. Average relative biomass of dominant holothurian families, combined ‘other holothurians’ and ‘other invertebrates’. B. Similarity of individual trawl catches based on the relative biomass of the same taxonomic groups (proportional biomass; Bray-Curtis similarity; group-average clustering).