DOI: 10.5061/dryad.b5mkkwhbw
title: Depth and latitudinal gradients of diversity in seamount benthic communities

description: Aim Latitudinal and bathymetric species diversity gradients in the deep
 sea have been identified, but studies have rarely considered these
 gradients across hard substratum habitats, such as seamount and oceanic
 island margins. This study aimed to identify whether the current
 understanding of latitudinal and bathymetric gradients in α-diversity
 (species richness) apply to seamount ecosystems, as well as ascertaining
 whether identifiable trends were present in seamount β-diversity along a
 bathymetric gradient. Location Exclusive Economic Zones of Saint Helena,
 Ascension Island and Tristan da Cunha, spanning 8°S to 40°S in the South
 Atlantic. Taxon Seamount megabenthic communities. Methods Images from 39
 transects, collected between 250 m and 950 m, were used to characterise
 species richness. We subsequently applied general linear models to test
 possible environmental drivers across latitudinal and bathymetric ranges.
 Regression models were employed to investigate the β-diversity gradient of
 species turnover with depth. Results Transects in temperate latitude had
 significantly higher species richness than those in the tropics. Surface
 primary productivity and substrate hardness both had significant positive
 effects on species richness, and a weak relationship between temperature
 and species richness was observed. No significant relationship between
 species richness and depth was detected, but there was significant species
 turnover with depth. Main conclusions Seamounts and oceanic islands do not
 conform to established depth-diversity relationships within the depth
 range studied. However, seamounts and oceanic islands in the South
 Atlantic do appear to follow a parabolic latitudinal diversity gradient,
 closely associated to higher productivity in temperate regions.
description: Drop camera images from 39 transects, collected between 250 m and
 950 m, were used to characterise species richness from within the
 Exclusive Economic Zones of Ascension Island, Saint Helena and Tristan da
 Cunha, spanning 8°S to 40°S. Environmnetal data derived from
 high-resolution multibeam bathyemtry were used to identify possible
 environmental drivers across latitudinal and bathymetric ranges (see
 transect metadata for variables).
description: # Depth and latitudinal gradients of diversity in seamount benthic
 communities Dataset DOI:
 [10.5061/dryad.b5mkkwhbw](10.5061/dryad.b5mkkwhbw) ## Description of the
 data and file structure This dataset consists of
 a Bridges_etal_diversity_gradients.csv data file. Drop-camera images
 collected from 39 transects, located between depths of 250 m and 950 m,
 were used to characterise species richness within the Exclusive Economic
 Zones of Ascension Island, Saint Helena, and Tristan da Cunha, spanning
 latitudes from 8° S to 40° S. Environmental data derived from
 high-resolution multibeam bathymetry were used to identify potential
 environmental drivers across both latitudinal and bathymetric gradients. |
 Column Name | Description | Units (if applicable) | |
 :----------------------- |
 :--------------------------------------------------------------------------------------------------------------------------- | :----------------------- | | OBJECTID | Unique ID | N/A | | Transect | Transect name | N/A | | dominantsubstrate | Dominant substrate category | N/A | | avghardness | Average hardness of transect  | N/A | | VME | VME category | N/A | | location | UKOT name | N/A | | site | Site name | N/A | | lat | Latitude | Decimal degrees | | long | Longitude | Decimal degrees | | trawlintensity | Intensity of trawl activity | N/A | | fished | Yes/no on prior fishing activity | N/A | | lutz\_poc\_w | Particulate organic carbon flux to depth | mg organic cabron/m2/day | | depth | Average depth of transect based on camera location | Meters | | temp | Average temperature of transect at depth | Degrees celsius | | oxygen | Average oxygen concentration of transect at depth | mg/L | | chla | Average chlorophyll-a measurements of transect at depth | mg/m3 | | salinity | Average salinity of transect at depth | N/A | | TotalSpecies\_controlled | Species richness controlled for the number of images sampled | N/A | | x\_coordGHO | X coordinate in Goodes Homolosine Ocean | Meters | | y\_coordGHO | Y coordinate in Goodes Homolosine Ocean | Meters | | Substrate | Dominant substrate description | N/A | | SURF\_CHL | Average surface chlorophyll a measurement for the transect | mg/m3 | | SURF\_PP | Average surface primary productivity measurement for the transect | grams/m3/day | | SURF\_PP\_gperm3pperyear | Average surface primary productivity measurement for the transect | grams/m3/yr | | SurfPP\_kgperm3perday | Average surface primary productivity measurement for the transect | kilograms/m3/year | | BBPI | Broadscale bathymetric position index of the seafloor | N/A | | Curvature | Curvature of the seafloor | N/A | | FBPI | Finescale bathymetric position index of the seafloor | N/A | | Rugosity | Rugosity of the seafloor | N/A | | Slope | Slope of the seafloor | Degrees | | Depth\_GIS | Average depth of the transect based on the bathymetry layer | Meters | | PredictedTemp | Predicted temperature of the transect based on the model described | Degrees celsius | | Depth\_band200m | Depth band code | N/A | | original\_n\_images | Original numbers of images in the transect | N/A | | new\_n\_images | Controlled number of images in the transect | N/A | | random\_SR1 | 10 iterations of selecting 16 random images were performed to determine variation across the transect - this is iteration 1 | N/A | | random\_SR2 | 10 iterations of selecting 16 random images were performed to determine variation across the transect - this is iteration 2 | N/A | | random\_SR3 | 10 iterations of selecting 16 random images were performed to determine variation across the transect - this is iteration 3 | N/A | | random\_SR4 | 10 iterations of selecting 16 random images were performed to determine variation across the transect - this is iteration 4 | N/A | | random\_SR5 | 10 iterations of selecting 16 random images were performed to determine variation across the transect - this is iteration 5 | N/A | | random\_SR6 | 10 iterations of selecting 16 random images were performed to determine variation across the transect - this is iteration 6 | N/A | | random\_SR7 | 10 iterations of selecting 16 random images were performed to determine variation across the transect - this is iteration 7 | N/A | | random\_SR8 | 10 iterations of selecting 16 random images were performed to determine variation across the transect - this is iteration 8 | N/A | | random\_SR9 | 10 iterations of selecting 16 random images were performed to determine variation across the transect - this is iteration 9 | N/A | | random\_SR10 | 10 iterations of selecting 16 random images were performed to determine variation across the transect - this is iteration 10 | N/A |