Focusing of phytodetritus deposition beneath a deep‐ocean front, Chatham Rise, New Zealand

Abstract

In October 2001, we observed a deep-ocean phytodetritus deposition event on Chatham Rise beneath the Subtropical Front (STF). The origin of this phytodetritus was probably an extensive phytoplankton bloom that occurred in the STF in the preceding weeks. We assessed the spatial distribution of the deposition event using video images from benthic lander and epibenthic trawl deployments and sediment pigment analyses at six sites on a north-south transect across Chatham Rise. High surficial sediment chlorophyll a concentrations were restricted spatially to the southern flank of Chatham Rise (350-1,200-m depth) with the highest values centered at ,750-m water depth (750 S). This southern 750 S site was also the only site where macroscopic phytodetritus was observed, coincident with elevated benthic biomass and sediment community respiration rates. At 750 S, phytodetritus resuspension was observed on video and corroborated by current meter, sediment trap, and optical 1 Corresponding author (s.nodder@niwa.co.nz). AcknowledgementsWe thank the officers and crew of RV Tangaroa, and numerous scientific personnel at NIOZ and NIWA, especially Henk Franken and Eilke Berghuis for lander support. Figures were drafted by Erika Mackay (NIWA). We appreciate the provision of unpublished organic carbon accumulation rates for Chatham Rise by Elisabeth Sikes (Rutgers University). We thank the SeaWiFS Project (Code 970.2) and the Distributed Active Archive Center (Code 902) at the Goddard Space Flight Center, Greenbelt, Maryland, for the production and distribution of the remotely sensed ocean color data, respectively. Thanks also to the two anonymous reviewers for their constructive comments.

Unimodal relationship between biomass and species richness of deep-sea nematodes: implications for the link between productivity and diversity

“…High-productivity sites usually experience greater temporal variability in organic matter input, which may favour species able to quickly exploit pulses of phytodetritus and thus lead to lower diversity through competitive exclusion (Chown & Gaston 1999). Considerable temporal variability in current flows on the Chatham Rise, for example, may lead to highly episodic phytodetritus deposition events (Nodder et al 2007), a process which may be accentuated by local seabed topography (S. Nodder unpubl. ).…”

“…Usbeck et al 2003) and satellite data (e.g. Lutz et al 2007) are easier to obtain, but current methods do not take into account the potential decoupling between POC flux at the seabed and surface productivity (Bues seler et al 2007), the influence of down-slope transport (Hecker 1990), lateral advection (Nodder et al 2007), riverine input (Hansell et al 2004) or bottom topography (e.g. canyons, Wei et al 2010).…”

“…POC flux to the seafloor depends on a variety of factors not included in these models, such as bottom micro- (Snelgrove et al 1994) and macro-topography (e.g. canyons; De Leo et al 2010), POC input from advective currents (Nodder et al 2007) and the efficiency with which organic matter is remineralized and consumed in the water column (Buesseler et al 2007).Determining the relationship between productivity and local diversity at large spatial scales requires a proxy that can be meaningfully compared between ocean basins. Deep-sea standing stocks (i.e.…”

Comparative biomass of sediment benthos across a depth transect, Chatham Rise, Southwest Pacific Ocean

“…Samples were collected at 9 sites across Chatham Rise in austral spring 2001 (29 September to 14 October; Table 1, Fig. 1; see also Nodder et al 2007). Sampling sites were situated along a latitudinal transect at 178°30' E, at water depths ranging from 350 (crest) to 3100 m north and 2800 m south of the rise (Table 1).…”

Overview and preliminary results of the Surface Ocean Aerosol Production (SOAP) campaign

“…Mixing across the front alleviates nutrient stress, which, combined with a relatively stable water column, promotes primary production (Chiswell et al, 2013). Ocean color climatologies show a monthly mean Chl a of 0.6 mg m −3 , reaching ∼ 1 mg m −3 over the Chatham Rise in spring (Murphy et al., 2001), and the region is characterized by elevated marine particle export, secondary production and fish stocks (Nodder et al, 2007;Bradford-Grieve et al, 1999). In spring the phytoplankton community composition varies with water mass, with diatoms dominating the STF, cryptophytes, prasinophytes and dinoflagellates being more prevalent in subtropical waters, and photosynthetic nanoflagellates dominating subantarctic waters (Chang and Gall, 1998;Delizo et al, 2007).…”