Habitat heterogeneity over multiple scales supports dense and diverse megafaunal communities on a NE Pacific ridge

Marine environments are highly heterogeneous, varying across scales of a few meters to entire ocean basins. Understanding the relationship between environmental variability and species distribution is essential for area-based management and conservation. However, this requires a precise alignment of seabed mapping, environmental and biological sampling, which is often difficult to achieve in the deep sea. There is thus an urgent need to tackle this challenge to effectively manage high-diversity habitats such as deep-sea coral and sponge (DSCS) aggregations. Relying on multiple subsea platforms, seafloor mapping and imaging techniques, we mapped the distribution of megafaunal communities at Sur Ridge (800-1250 m depth; off Central California) across multiple spatial scales. First, remotely operated vehicle (ROV) video transects were conducted to characterize community distribution along the ridge, in relation to substratum type, environmental conditions and 1-m scale bathymetry. Five dis..., All data were collected at Sur Ridge, a high-relief topographic feature ~35 km west of Point Sur, California.
Data on megafaunal densities and seafloor substratum type were collected from remotely operated vehicle (ROV) video transects conducted throughout Sur Ridge between July 2014 and December 2021 (ROV Doc Ricketts deployed from the R/V Western Flyer). The ROV was equipped with two parallel laser beams (29 cm apart) to estimate the width of the field of view during transects. A total of 58 video transects (each 50 m long) were annotated using MBARI’s video annotation and reference system (VARS; Schlining and Stout 2006). All species were identified to the lowest taxonomic level possible based on morphology and sorted into morphotypes. Megafaunal densities were then estimated based on transect area. Substratum types were estimated from 40 frame grabs per video transect, which were captured at regular intervals using GOM player (version 2.3.80.5345). Frame grabs were analyzed with PAP..., , # Habitat heterogeneity over multiple scales supports dense and diverse megafaunal communities on a NE Pacific ridge

[https://doi.org/10.5061/dryad.z08kprrn4](https://doi.org/10.5061/dryad.z08kprrn4)

## Description of the data and file structure

### Files and variables

#### File: FGirard\_SurRidge\_substratum\_matrix.xlsx

**Description:** Substratum composition matrix containing the estimated proportions of each substratum type per transect.

##### Variables

* The first column contains transect numbers.
* The remaining columns show the estimated proportions per transect for all substratum types.

#### File: FGirard\_SurRidge\_distances\_to\_DSCS\_LASS.xlsx

**Description:** Distances between megafaunal taxa (other than deep-sea corals and sponges) observed on the LASS mosaic and nearest coral and sponge.

##### Variables

* Taxon: Name of observed taxa (megafauna other than coral or sponge).
* Distance to nearest coral: Unit: m.
* Nearest coral taxon: name of nearest coral taxon.
...