Monterey Bay Aquarium Research Institute


PULSE 53: Pelagic-Benthic Coupling and the Carbon Cycle
September 17 - September 23 , 2007

Cruise Description

Purpose

  1. Conduct a study of pelagic-benthic coupling along a transect of existing stations extending from Smooth Ridge/Canyon axis (SR/C, 1300 m depth) and Shepard Meander (SM, 3450 m depth) out to Sta. M (< 4100 m depth) at the terminus of the Canyon on the Monterey Deep-sea Fan (Fig. 1).
  2. This continuing research addresses six main questions:
    • How does the quality and quantity of sinking particulate matter (e.g. organic carbon, phytopigments) entering the benthic boundary layer (BBL) and reaching the sea floor differ spatially and temporally across a transect of stations from the Monterey slope to the abyss?
    • How does the sediment community activity [e.g. sediment community oxygen consumption (SCOC)] and sediment structure (e.g. burrowing) differ spatially and temporally across a transect of stations from the Monterey slope to the abyss?
    • Do temporal changes in sediment community activity (e.g. SCOC) and sediment structure (e.g. burrowing) correlate to the quality and quantity of sinking particulate matter (e.g. organic carbon) reaching the sea floor across a transect of stations from the Monterey slope to the abyss?
    • How do epibenthic megafauna species composition, abundance, size and movements differ spatially and temporally across a transect of stations from the Monterey slope to the abyss?
    • How do temporal changes in epibenthic megafauna species composition, abundance, size and movements relate to the quality and quantity of sinking particulate matter (e.g. organic carbon) reaching the sea floor across a transect of stations from the Monterey slope to the abyss?
    • How do temporal changes in particulate matter flux (e.g. organic carbon), sediment community (SCOC, burrowing), and epibenthic megafauna (species composition, abundance, size, movements) relate to rainfall, river discharge, canyon transport and climate indices (e.g. El Niño Southern Oscillation, Nothern Oscillation Index, Bakun Upwelling Index) across a transect of stations from the Monterey slope to the abyss?

Introduction

Retrieval of the Camera MooringOn this cruise we will study the coupling of pelagic food supply and benthic community responses. This is a continuation of an 18-year long-term time-series research project at a deep-sea site off the coast of California. Station M lies in the eastern North Pacific about 200km off the coast of Point Conception, and is subject to strong seasonal pulses of surface productivity (Smith et al., 1992). The sea floor at 4100 m has very little topographic relief (< 100 m over 1,600 km2) and is composed of silty-clay sediment with seasonal deposits of flocculent phytodetritus. Currents near the seafloor average 3.8 cm s-1, can reach a maximum of 18.2 cm s-1 and flow to the south during periods of highest current speeds and towards the north and west during the periods of low current speeds (Beaulieu and Baldwin, 1998).

Time-lapse photography has revealed abundant evidence of bioturbation and other epifaunal activity at the site in the form of numerous trails, furrows and mounds that can be centimeters to meters across (Smith et al., 1993). Recent research has shown that climate variation can affect levels of photosynthetic activity at the sea surface (Smith et al., 2001). Photosynthetic activity levels then affect the quantity and quality of particulate organic carbon (POC) flux to the seafloor (Smith et al., 1994). Amounts of POC flux can affect the size and abundance of benthic fauna (Ruhl and Smith, 2004).

Our unprecedented long time-series study of pelagic-benthic coupling at Sta. M is continuing in 2007 with this cruise on the R/V Western Flyer. We will process sediment trap samples from Station M in the laboratory to obtain values for organic carbon and nitrogen, as an estimate of the food supply to the benthic community. Time-lapse photographs of the sea floor will be analyzed for megafaunal activity and sedimentation events. The free vehicle grab respirometer (FVGR) has also been deployed on each cruise to measure sediment community oxygen consumption (SCOC) which has showed a consistent seasonal trend. Benthic photo-transects continue to be conducted with the ROV Tiburon to assess megafauna abundance and size.

Methods

We will recover, service and redeploy a long-term sediment trap and camera mooring, deploy and recover a free-vehicle grab respirometer (FVGR), use the ROV Tiburon to conduct benthic photo-transects, and collect push core samples and megafauna specimens. We plan to test the new Benthic Rover respirometer system and steering. Also deployed will be two sediment enrichers. These will descend on a free-vehicle elevator and be deployed using the ROV. The enrichers add specified algal nutrients to the sediment within an enclosed space in order to determine the effects of nutrient enrichment on the microfaunal and bacterial communites in the top layers of the sediment. In conjunction with the enrichers a weighted marker with floating sphere will need to be deployed in order to return to the site for future cruises.

Planned Transit

== Sept 17
0900 Depart Moss Landing
Transit to: Station M - 34º50’N, 123º00’W; 4000 m depth
0500 Deploy FVGR

== Sept 18
0700 Deploy ROVER
0900 Deploy Elevator with spreaders
1000 ROV Tiburon dive for ROVER observation, spreader deployment, biological and sediment sample collection

== Sept 19
0500 Acoustically recall long-term mooring
0700 Recover long-term mooring for cleaning, battery change and film replacement
0900 ROV Tiburon dive for photo transects, megafauna collections

== Sept 20
0700 Deploy long-term mooring
0900 Recover FVGR
1100 ROV Tiburon dive

== Sept 21
0700 ROV Tiburon dive

R/V Western Flyer

== Sept 22
0700 ROV Tiburon dive
1500 Recover ROVER

== Sept 23
0700 ROV Tiburon dive
1700 Begin steam back to Moss Landing

== Sept 24
0900 Arrive Moss Landing

Further Reading

  • Bailey, D., H.A. Ruhl and K.L. Smith, Jr. (2006) Long-term changes in benthopelagic fish abundance in the abyssal northeast Pacific Ocean. Ecology 87: 549-555.
  • Beaulieu, S. and R. Baldwin (1998) Temporal variability in currents and the benthic boundary layer at an abyssal station off central California. Deep-Sea Research II 45: 587-615.
  • Hwang, J., E.R.M. Druffel, S. Griffin, K.L. Smith, Jr., R.J. Baldwin and J.E. Bauer (2004) Temporal variability of delta 14C, 13C and C/N in sinking particulate matter at a deep time-series station in the northeast Pacific Ocean. Global Biogeochem. Cycl. 18: GB4015, doi: 10.1029/2004GB002221.2004.
  • Ruhl, H. A., (2007) Abundance and size distribution dynamics of abyssal epibenthic megafauna in the northeast Pacific. Ecology 88: 1250-1262.
  • Ruhl, H.A., Smith, K.L., Jr. (2004) Shifts in deep-sea community structure linked to climate and food supply. Science 305: 513-515.
  • Ruhl, H. A. (in press) Community change in the variable resource habitat of the abyssal NE Pacific. Ecology.
  • Smith, K.L., Jr., R.J. Baldwin, and P.M. Williams (1992) Reconciling particulate organic carbon flux and sediment community oxygen consumption in the deep North Pacific. Nature 359: 313-316.
  • Smith, K.L., Jr., R.J. Baldwin, D.M. Karl and A. Boetius (2002) Benthic community responses to pulses in pelagic food supply: North Pacific Subtropical Gyre. Deep-Sea Research. I. 49: 971-990.
  • Smith, K.L., Jr., R.S. Kaufmann, R.J. Baldwin, and A.F. Carlucci (2001) Pelagic-benthic coupling in the abyssal eastern North Pacific: An 8-year time-series study of food supply and demand. Limnology and Oceanography 46(3): 543-556.
  • Smith, K.L., Jr., R.S. Kaufmann, and W.W. Wakefield (1993) Mobile megafaunal activity monitored with a time-lapse camera in the abyssal North Pacific. Deep-Sea Research I 40(11/12): 2307-2324.
  • Smith, K.L., R.S. Kaufmann, and R.J. Baldwin (1994) Coupling of near-bottom pelagic and benthic processes at abyssal depths in the Eastern North Pacific-Ocean. Limnology and Oceanography 39(5): 1101-1118.
  • Smith, K.L., Jr., N.D. Holland and H.A. Ruhl (2005) Enteropneust production of spiral fecal trails on the deep-sea floor observed with time-lapse photography. Deep-Sea Research I 52: 1228-1240.
  • Smith, K.L., Jr., R.J. Baldwin, H.A. Ruhl, M. Kahru, B.G. Mitchell and R.S. Kaufmann (2006) Climate effect on food supply to depths greater than 4000 meters in the northeast Pacific. Limnology & Oceanography 51: 166-176.
  • Vardaro, M.F., D. Parmley and K.L. Smith, Jr. (2007) A study of possible “reef effect” caused by a long-term time-lapse camera in the deep North Pacific. Deep-Sea Research I 54: 1231-1240.
  • Smith, K.L., Jr., B.H. Robison, J.J. Helly, R.S. Kaufmann, H.A. Ruhl, T.J. Shaw, B.S. Twining and M. Vernet (2007) Free-drifting icebergs: hot spots of chemical and biological enrichment in the Weddell Sea. Science 317: 478-482.
  • Booth, J. A., H. A. Ruhl, L. Lovell, D. M. Bailey, and K. L. Smith, Jr. (submitted) Population dynamics of NE Pacific abyssal ophiuroids. Marine Biology.

Click on the links above to find out more about this exciting cruise!