Food Webs and Niche Space : J. Cohen, Princeton U.P. Monographs in Population Biology, Princeton, N.J., 1978, 189 pp.; cloth $14.00, paper $6.95.

Abstract

Neutrally buoyant sediment traps (NBSTs) were deployed concurrently with particle interceptor traps (PITs) on monthly cruises of the Bermuda Atlantic Time-series Study (BATS) from June 2007 to July 2010. In most months, particulate organic carbon flux measured by the two sediment trap systems agreed within the range of variability for two separate NBSTs. In three periods of this study however, the PITs collected more than three times the amount of particulate organic carbon (POC) than the NBSTs. One of these periods coincided with two instances when the mixed layer was deeper than the trap deployment depth, which may lead to biased collection. One of the anomalous periods occurred during summer months, for which we were unable to find existing evidence of biogeochemical changes that would lead to such increases in POC flux. The third anomalous period occurred when the POC flux measured by the NBSTs was near zero. We hypothesize that the PITs may have a positive bias at low fluxes relative to the NBSTs. Zooplankton swimmers accounted for 49±20% of the total measured carbon flux over the three year period and swimmer removal by screening of samples through a 350 μm mesh was established as an effective method for this site. Process blank corrections based on sample-identical blanks were important for determining mass and carbon flux from both the NBSTs and the PITs. This new record of particle export from NBSTs suggests that the observed carbon imbalance in this region of the ocean (Michaels et al., 1994) is not due to undersampling by the PITs and that export ratios may be even lower than previously thought.