DOI: 10.5061/dryad.931zcrjpx
title: Patagonia invertebrate densities

description: The kelp forests of southern Patagonia have a large diversity of habitats,
 with remote islands, archipelagos, peninsulas, gulfs, channels, and
 fjords, which are comprised of a mixture of species with temperate and
 sub-Antarctic distributions, creating a unique ecosystem that is among the
 least impacted on Earth. We investigated the distribution, diversity, and
 abundance of marine macroinvertebrate assemblages from the kelp forests of
 southern Patagonia over a large spatial scale and examined the
 environmental drivers contributing to the observed patterns in assemblage
 composition. We analyzed data from 120 quantitative underwater transects
 (25 x 2 m) conducted within kelp forests in the southern Patagonian fjords
 in the Kawésqar National Reserve (KNR), the remote Cape Horn (CH) and
 Diego Ramírez (DR) archipelagos of southern Chile, and the Mitre Peninsula
 (MP) and Isla de los Estados (IE) in the southern tip of Argentina. We
 observed rich assemblages of macroinvertebrates among these kelp forests,
 with a total of 185 unique taxa from 10 phyla and 23 classes/infraorders
 across the five regions. The number of taxa per transect was highest at
 IE, followed by MP, CH, and KNR, with the lowest number recorded at DR.
 The trophic structure of the macroinvertebrate assemblages was explained
 mostly by wave exposure (28% of the variation), followed by salinity (12%)
 and the KNR region (11%). KNR was most distinct from the other regions
 with a greater abundance of deposit feeders, likely driven by low salinity
 along with high turbidity and nutrients from terrigenous sources and
 glacial melt. Our study provides the first broad-scale description of the
 benthic assemblages associated with kelp forests in this vast and
 little-studied region and helps to establish baselines for an area that is
 currently lightly influenced by local anthropogenic factors and less
 impacted by climate change compared with other kelp forests globally.
description: Characterization of the
 macrobenthos was conducted by scuba divers along two 25-m long transects
 at each sampling location. Transects were run parallel to the shoreline,
 with a target depth of 10 m, depending on location of the lower edge of
 the kelp forest. Since sampling sites targeted kelp forests only, the
 underlying habitats were biased towards hard substrate. For
 sessile and mobile invertebrates, the number of individuals was estimated
 on 1-m of either side of the transect line (50 m<sup>2</sup>).
 For colonial organisms (sponges, some cnidarians, bryozoans, and some
 tunicates) colonies, rather than individuals, were counted. When a species
 was extremely abundant (i.e., &gt; 500) along the transect, abundance
 was estimated considering the number of individuals/colonies
 m<sup>-2</sup> and scaled to the total area of the transect
 (50 m<sup>2</sup>). Only non-cryptic invertebrates ≥1 cm were
 enumerated. A second diver counted the number of kelp
 (<em>Macrocystis pyrifera</em> and
 <em>Lessonia</em> spp.) stipes within 1-m on either side of
 the transect and recorded the bottom type for each transect. Salinity and
 temperature measures were recorded at each site using a YSI model 556
 handheld multiparameter instrument or RBR concerto multi-channel logger.
 Salinity was recorded in parts per thousand (ppt) ± 0.1 and temperature
 was recorded in <sup>o</sup>C ± 0.1.
description: Excel