Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Project Information
• Funding

To parse the influences of fragmentation components on scallop survival, we generated nine unique landscape grids of 15 × 15 cells. Each cell was the size of an ASU, making the landscape area = 234 m² (18-m × 13-m). These landscapes were part of a larger-scale concurrent experiment, during which we examined seagrass fragmentation effects on estuarine faunal communities (Yarnall et al. In Press). Landscapes were designed to be treatments along orthogonal axes of seagrass percent cover of the landscape footprint (10%, 35%, 60%) and fragmentation per se, indexed by percolation probability (0.1, 0.35, 0.59).

Relative scallop survival was measured using tethered juvenile bay scallops of initial shell height (SH) 3-5 mm, provided by the Castagna Shellfish Research Hatchery at The Virginia Institute of Marine Science, Eastern Shore Laboratory (VIMS ESL) in Wachapreague, VA. The knotted end of 10-cm segment of 12-lbs test monofilament was dotted with cyanoacrylate glue and pressed into a scallop’s ventral shell ridge under a tab of duct tape. Each tether was then anchored to a 30-cm lawn staple and held overnight in aquaria to check attachment integrity. Tethers were then deployed across landscapes the following day.

To examine whether landscape configuration could mediate density-dependent predation rates on scallops, tethers were deployed in low (1x = 4 or 5 m^-2) and high (6x = 24 or 30 m^-2) density treatments (x was chosen based on scallop availability). All scallop tethers were placed ≤1-m from the seagrass-sandflat interface on randomly selected edge (interface-bordering) ASUs, to avoid potential edge effects. Five 24-h survival assay trials were conducted from July to September 2018. Because predation rates after 24 h were high during the first trial, when scallops were smallest, tethers were also checked at 2 h and 6 h during subsequent trials. However, preliminary analysis revealed that across trials, predation rates after 2 h and 6 h were too low to provide resolution among landscape treatments; therefore, only results for cumulative survival after 24 h are presented.

During each survival assay, observers snorkel surveyed tethers and recorded the number of live and dead scallops per treatment. During the first trial, ten tethered dead scallop shells (valves glued shut) were deployed as an additional tether integrity control. However, controls were depredated at similar rates to live scallops, as evinced by crushed shells. For all subsequent trials, control tethers were deployed in cages constructed from cuboid PVC frames covered by mesh VEXAR®. Attachment failure occurred in <3% of all caged-control tethers, therefore no adjustments to scallop recovery rates were necessary. 

Depth note:  Depth ranges were similar across all sites as they were located on a single shoal (Oscar Shoal in Back Sound, NC, USA). Depths typically ranged from <0.5 m (at low tide) to 1.5-2 m (at high tide).

Organism identifiers (common name, scientific name, LSID):
bay scallop, Argopecten irradians, urn:lsid:marinespecies.org:taxname:156817

All data were entered electronically into an Excel spreadsheet.

* Sheet "Data" of submitted file "Scallop_Survival_Assay_2018.xlsx" was imported into the BCO-DMO data system for this dataset.
** In the BCO-DMO data system missing data identifiers are displayed according to the format of data you access. For example, in csv files it will be blank (null) values. In Matlab .mat files it will be NaN values. When viewing data online at BCO-DMO, the missing value will be shown as blank (null) values.

* DateTime with time zone column added "ISO_DateTime_UTC_In." Converted from Date_In and Time_In (from local EST/EDT to UTC) converted to ISO 8601 format.

Amount and quality of habitat is thought to be of fundamental importance to maintaining coastal marine ecosystems. This research will use large-scale field experiments to help understand how and why fish populations respond to fragmentation of seagrass habitats. The question is complex because increased fragmentation in seagrass beds decreases the amount and also the configuration of the habitat (one patch splits into many, patches become further apart, the amount of edge increases, etc). Previous work by the investigators in natural seagrass meadows provided evidence that fragmentation interacts with amount of habitat to influence the community dynamics of fishes in coastal marine landscapes. Specifically, fragmentation had no effect when the habitat was large, but had a negative effect when habitat was smaller. In this study, the investigators will build artificial seagrass habitat to use in a series of manipulative field experiments at an ambitious scale. The results will provide new, more specific information about how coastal fish community dynamics are affected by changes in overall amount and fragmentation of seagrass habitat, in concert with factors such as disturbance, larval dispersal, and wave energy. The project will support two early-career investigators, inform habitat conservation strategies for coastal management, and provide training opportunities for graduate and undergraduate students. The investigators plan to target students from underrepresented groups for the research opportunities.

Building on previous research in seagrass environments, this research will conduct a series of field experiments approach at novel, yet relevant scales, to test how habitat area and fragmentation affect fish diversity and productivity. Specifically, 15 by 15-m seagrass beds will be created using artificial seagrass units (ASUs) that control for within-patch-level (~1-10 m2) factors such as shoot density and length. The investigators will employ ASUs to manipulate total habitat area and the degree of fragmentation within seagrass beds in a temperate estuary in North Carolina. In year one, response of the fishes that colonize these landscapes will be measured as abundance, biomass, community structure, as well as taxonomic and functional diversity. Targeted ASU removals will then follow to determine species-specific responses to habitat disturbance. In year two, the landscape array and sampling regime will be doubled, and half of the landscapes will be seeded with post-larval fish of low dispersal ability to test whether pre- or post-recruitment processes drive landscape-scale patterns. In year three, the role of wave exposure (a natural driver of seagrass fragmentation) in mediating fish community response to landscape configuration will be tested by deploying ASU meadows across low and high energy environments.