Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

This dataset includes epibenthic community abundance collected offshore by trawls and reported as numbers per 100 square meters.

Sampling locations were from the Aleutian Archipelago offshore between longitude 173.9 and -167.6 in June 2016 and July 2017.

Trawls were conducted with a 3.05 m plumb-staff beam trawl with a 7-mm mesh and a 4-mm codend liner (Gunderson & Ellis, 1986). For each trawl, the trawl net was towed for approximately 3 minutes on the seafloor with the vessel traveling at 1.5 knots. A temperature-depth recorder was attached to the trawl net to determine effective trawling distances. The start of each trawl was determined by the time at which the trawl net stopped descending in the depth profile, and the end of each trawl was determined by the time the trawl net began ascending. Trawl distances were determined by referencing the GPS coordinates of the research vessel for the start and end times of each trawl event. Occasionally, the trawl net became damaged by rocks during a trawl event, preventing effective sampling after the collision. For these trawls, the collision point was detectable by a sudden decrease in depth of the trawl net, and the effective trawling swath was assumed to be from the beginning of the trawl up to the collision point.

Organisms were sorted and identified to the lowest taxonomic level feasible. Members of each taxonomic group were counted and their damp-biomass (including shells for mollusks and crabs) was determined. Voucher specimens were prepared in 10% buffered formalin for those taxa that could not be identified in the field.

Some large samples were split in half. This is Indicated as the subsaample_factor. A value of 2 (trawl 24) indicates that half of the trawl contents were taken for biomass and count measurements. The biomass and count values in the area-standardized data sheets are estimated by doubling the values recorded for the subsampled portion.

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- corrected spelling of 4 taxa to agree with World Register of Marine Species names. See Parameter list below for submitted names, in parentheses.

NSF abstract:

In many ecosystems the presence of a single dominant species can modify the physical conditions of the environment and alter patterns of biodiversity, nutrient cycling, and primary production. Losses of these "ecosystem engineers" can have profound impacts to how ecosystems function. Coastal kelps provide excellent examples of organisms whose structure modifies the physical characteristics of their habitats (light, nutrients, water motion) and supports enhanced biodiversity. The kelp forests in the coastal waters of the Aleutian Archipelago have suffered large-scale declines over the past several decades. This project will examine how these losses impact patterns of ecosystem production and biodiversity using a combination of techniques ranging from in situ benthic chambers and shipboard incubations to remote sensing using satellite imagery. The results will provide an understanding of how such events may impact this and other ecosystems. This project will support graduate students and will introduce the public to the Aleutian ecosystems in a series of videos. The investigators will also work with a San Diego high school teacher to integrate project findings into classroom activities, and they expect to involve a teacher in their field program.

The investigators will ask two highly integrated questions: 1) How do the widespread losses of kelp forests impact benthic productivity across the Aleutian Archipelago? 2) How do the widespread losses of kelp forests impact benthic biodiversity and community structure across the archipelago? To address these, the investigators will estimate changes to productivity at ten islands where they have historic data on seaweed community composition and estimates of kelp canopy cover. They will use in situ benthic chambers placed in both kelp forests and urchin barrens to measure plot-scale patterns of net ecosystem productivity (NEP), and shipboard incubations to examine net primary productivity (NPP) for the dominant macroalgae. Data for individual species rates of NPP will be scaled by their biomass and combined with in situ plot-scale benthic chamber experiments of whole communities to estimate NEP at the islands visited. These estimates will be scaled up to calculate NEP across the entire archipelago by first extrapolating results from the study sites to entire islands, and then across the archipelago. They will also estimate broad-scale patterns in production by characterizing water column irradiances across the archipelago and modeling NPP using species-level relationships between irradiance and photosynthesis. Coupling these with estimates of water column irradiance and community respiration will allow modeling of NEP across this region. Benthic biodiversity will be assessed using diver surveys and shipboard benthic trawls. Following these activities, satellite remote sensing of the kelp canopies dating back to the 1980s and the investigators' own historical data on benthic macroalgal abundances at these and other islands will be used to estimate the temporal and spatial patterns of change across the archipelago.

For more information see:

Project blog: http://sdsukelp.weebly.com/blog
Project website: http://www.uaf.edu/cfos/research/projects/collaborative-research--/