Secondary Production of Macrofaunal Crustaceans in DetritalTopographical features capable of accumulating organic debris, such as submarine canyons, are common along many coasts and can support hot spots of secondary production. The floor of the La Jolla submarine canyon (32° 52' N, 117° 15' W) is covered by a persistent mat of surfgrass and kelp detritus from a depth of 15 m to at least 300 m. The detritus is inhabited by a dense assemblage of amphipod and leptostracan crustaceans which at times achieve densities of over 3 million individuals and biomass exceeding 1 kg (dry weight) per square meter. In samples collected between March 1992 and March 1993, leptostracan density averaged 6.9 x 105 m-2 (s. d.: 4.4 x 105) and amphipods 7.8 105 m-2 (s. d. 2.7 x 105). The combined maximum density of these animals was 3,240,000 m-2, an order of magnitude greater than any natural macrofaunal assemblage reported in the literature
Secondary production of the leptostracans, which (average length 4.5 mm), calculated by the cohort summation of losses method, was 3,300 g dry weight m-2 yr-1 (P:B = 7.2). This value is an underestimate because many of the largest size classes could not be assigned to a cohort and were omitted from the calculation. The mean dry biomass of the amphipod assemblage during the study was 168 g m-2and assuming a production:biomass ratio of 4.0, amphipod annual production is estimated as 672 g dry weight m-2 yr-1 (average length of amphipods, 3.5 mm). I found only two reports of secondary production in the literature with values within the same order of magnitude of those found in the present study.
From: Vetter, E. W. 1994. "Hotspots of benthic production." Nature 372: 47.
Vetter, E. W. 1995. "Detritus-Based Patches of High Secondary Production in the Nearshore Benthos." Marine Ecology Progress Series 120: 251-262.