Large salp bloom export from the upper ocean and benthic community response in the abyssal northeast Pacific: Day to week resolution

Abstract

A large bloom of Salpa spp. in the northeastern Pacific during the spring of 2012 resulted in a major deposition of tunics and fecal pellets on the seafloor at , 4000 m depth (Sta. M) over a period of 6 months. Continuous monitoring of this food pulse was recorded using autonomous instruments: sequencing sediment traps, a timelapse camera on the seafloor, and a bottom-transiting vehicle measuring sediment community oxygen consumption (SCOC). These deep-sea measurements were complemented by sampling of salps in the epipelagic zone by California Cooperative Ocean Fisheries Investigations. The particulate organic carbon (POC) flux increased sharply beginning in early March, reaching a peak of 38 mg C m 22 d 21 in mid-April at 3400 m depth. Salp detritus started appearing in images of the seafloor taken in March and covered a daily maximum of 98% of the seafloor from late June to early July. Concurrently, the SCOC rose with increased salp deposition, reaching a high of 31 mg C m 22 d 21 in late June. A dominant megafauna species, Peniagone sp. A, increased 7-fold in density beginning 7 weeks after the peak in salp deposition. Estimated food supply from salp detritus was 97-327% of the SCOC demand integrated over the 6-month period starting in March 2012. Such large episodic pulses of food sustain abyssal communities over extended periods of time.

Major impacts of climate change on deep-sea benthic ecosystems

“…Thus, it is a reasonable expectation that macro-and megafaunal communities will shift in relation to future climatically linked changes in POC flux to the abyssal seafloor ( Figure 4D). Episodic pulses provide food supply to sustain benthic communities over periods of deficit (Smith et al, , 2014; the predicted reduction in POC input over large abyssal areas will likely increase these deficits with a significant impact on faunal communities and their role in ecosystem functioning ( Figure 4D). POC flux to the seafloor, and its degree of seasonality, also strongly influence benthic foraminiferal abundance, diversity and assemblage composition (Altenbach et al, 1999;Sun et al, 2006;Corliss et al, 2009;Gooday et al, 2012).…”

Decadal Change in Sediment Community Oxygen Consumption in the Abyssal Northeast Pacific

“…Large pulses of organic carbon such as salps were underestimated by sediment traps and probably form a significant food input to the benthic community to offset any deficiencies over extended periods of time . Exclusion due to baffle size, clogging and the influence of undersampling by sediment traps, lateral advection of marine and terrestrial organic matter in the benthic boundary layer from the continental margin could each contribute to underestimation of POC flux with sediment traps (e.g., Smith et al 2001Smith et al , 2014.…”

“…Sediment samples were frozen at -20°C. In the laboratory, samples were thawed and split with three-quarters of each sample analyzed for organic carbon following the procedure described by Smith et al (2014). POC flux from the 600-mab sediment trap is presented where available (Fig.…”

“…For much of the record, however, it seemed there was insufficient food supply, even accounting for visible depositions of particulate organic matter on the seafloor (e.g., Smith et al 2008). However, observations in 2011 and 2012 of new peaks in POC flux and subsequent SCOC suggested that large-scale food depositions that occur as rarely as once a decade may aid in balancing demand (e.g., Smith et al 2014). Here, we use newly acquired data extending into 2015 to explore the daily, seasonal and long-term variation in POC flux and SCOC, and discuss the potential for balancing these rates in terms of carbon cycle dynamics.…”

“…Rover I was lost during a mission in the central Pacific in 1999. Rover II development began shortly afterward, and this vehicle has been in operation since 2011 (McGill et al 2009;Sherman and Smith 2009;Smith et al 2013Smith et al , 2014. Synoptic measurements of SCOC between many of these instruments have yielded comparable fluxes with no significant differences (Smith et al 1997Smith and Kaufmann 1999), allowing for long-term changes to be assessed.…”