Realm: Marine
Climate: Temperate
Biome: Temperate shelf and seas ecoregions
Central latitude: 34.833333
Central longitude: -123.000000
Duration: 13 years, from 1989 to 2004

350 records

10 distinct species

Across the time series Abyssocucumis abyssorum is the most frequently occurring species

Methods

Forty-eight photographic line transects typically 1.5 km in length were conducted between October 1989 and September 2002. These transects were typically conducted seasonally but this frequency was variable due to logistical constraints. Linetransect photography was conducted using a Benthos 372 35mm film camera and Benthos 382 strobe mounted on a towed benthic camera sled at a height of 82 cm and 22.5? below horizontal (S1). The camera took photographs approximately every five s as the sled moved along the bottom at roughly 2.8 km h-1 creating a continuous image mosaic of the seafloor with overlapping frames. A semi-balloon otter trawl was towed behind the camera sled to non-quantitatively collect specimens from the line transect area. Collected specimens were then identified and used in part as a voucher collection to identify species in the line-transect photographs. The semi-balloon trawl had a 6.1 m opening and 3.8 cm stretch mesh net with a 1.3 cm mesh cod-end liner (S1). The photographs were evaluated using a Canadian grid system (S2) and the computer program DISTANCE (S3) which was based on line-transect theory (S4). The relative location of each individual along each transect was digitized. DISTANCE estimated the visibility of an object at a distance perpendicular to the centerline of the transect and provided a probability density function and effective strip width (ESW) for each species. The sum of non-overlapping distances between frames along the transect axis provided the transect length. Overlap was estimated by measuring the relative positions of a distinct object in sequential frames. The ESW was multiplied by the transect length to provide an estimation of abundance. When the abundance of any given group was below 15 individuals transect-1 an ESW from a species of similar visibility was used to estimate abundance. Detailed descriptions of the line-transect methodsapplied to the analysis of deep-sea camera sled photographs can be found in the supplemental reference materials (S5 S6). The Bray-Curtis dendrogram was created using log transformed (log(x+1)) monthly abundance estimates for each of the ten most dominant taxa with group average clustering. Photographic line transect Unit of abundance = CountPerSqM, Unit of biomass = Weight

Citation(s)

Kuhnz, L. A., Ruhl, H. A., Huffard, C. L. & Smith, K. L. (2014) Rapid changes and long-term cycles in the benthic megafaunal community observed over 24 years in the abyssal northeast Pacific. Progress in Oceanography, 124, 1–11.
Ruhl, H. A. & Smith, K. L. (2004) Shifts in Deep-Sea Community Structure Linked to Climate and Food Supply. Science, 305, 513–515.