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Marine communities of the newly created Kawésqar National Reserve, Chile: from glaciers to the Pacific Ocean

Citation

Friedlander, Alan (2021), Marine communities of the newly created Kawésqar National Reserve, Chile: from glaciers to the Pacific Ocean, Dryad, Dataset, https://doi.org/10.5061/dryad.f7m0cfxvj

Abstract

The newly created Kawésqar National Park (KNP) and National Reserve (KNR) in southern Chile consists of diverse terrestrial and marine habitats, which includes the southern terminus of the Andes, the Southern Patagonia Ice Fields, sub-Antarctic rainforests, glaciers, fjords, lakes, wetlands, valleys, channels, and islands. The marine environment is influenced by wide ranging hydrological factors such as glacier melt, large terrigenous inputs, high precipitation, strong currents, and open ocean water masses. Owing to the remoteness, rugged terrain, and harsh environmental conditions, little is known about this vast region, particularly the marine realm. To this end, we conducted an integrated ecological assessment using SCUBA and remote cameras down to 600 m to examine this unique and largely unexplored ecosystem. Kelp forests (primarily Macrocystis pyrifera) dominate the nearshore ecosystem and provide habitat for myriad benthic organisms. In the fjords, salinity was low and both turbidity and nutrients from terrigenous sources were high, with benthic communities dominated by active suspension feeders (e.g., Bivalvia, Ascidiacea, and Bryozoans). Areas closer to the Pacific Ocean showed more oceanic conditions with higher salinity and lower turbidity, with benthic communities experiencing more open benthic physical space in which predators (e.g., Malacostraca and Asteroidea) and herbivorous browsers (e.g., Echinoidea and Gastropoda) were more conspicuous components of the community compared to the inner fjords. Hagfish (Myxine sp.) was the most abundant and frequently occurring fish taxa observed on deep-sea cameras (80% of deployments), along with several taxa of sharks (e.g., Squaliformes, Etmopteridae, Somniosidae, Scyliorhinidae), which collectively were also observed on 80% of deep-sea camera deployments. The kelp forests, deep fjords, and other nearshore habitats of the KNR represent a unique ecosystem with minimal human impacts at present. The KNR is part of the ancestral territory of the indigenous Kawésqar people and their traditional knowledge of this region is strongly supported by our scientific findings.

Methods

In-situ surveys: invertebrates and fishes

Two transects of 25-m length, carried out on SCUBA, were conducted parallel to shore, towards the lower edge of the kelp zone. For sessile and mobile invertebrates, the number of individuals was estimated within 1-m of either side of the transect line (50 m2). For colonial organisms (sponges, some cnidarians, bryozoans, and some tunicates) colonies, rather than individuals, were counted. Only non-cryptic invertebrates > 1 cm were enumerated. A second diver counted the number of kelp stipes (M. pyrifera and Lessonia spp.) within 1-m on either side of these transects. M. pyrifera holdfast diameters were measured by a third diver as an indication of plant size and age [2]. This diver also measured test diameter of the sea urchin Loxechinus albus in the general vicinity of the transect.

For fish surveys, a scuba diver counted and sized all fishes within 1-m of either side of the 25-m transect lines (50 m2) at each survey site (N = 2 transects). The transect column extended from the benthos to the surface, or as far as visibility allowed, to include species associated with the kelp canopy and water column. Total fish lengths were estimated to the nearest cm. In addition, photographs were taken in situ to assist with species identification, and document underwater coloration and associated habitat. Fish species biogeographic affinities and trophic group designations were obtained from published literature [26–28].

In addition to these quantitative surveys, we surveyed the deeper fjord slopes down to 40 m where we qualitatively described these communities and recorded the presence of taxa visually and with photography. Prior to each survey, temperature and salinity measurements were taken at a depth of 5 m below the surface using a YSI model 556 handheld multiparameter instrument.

Deep-sea camera surveys

National Geographic’s deep-sea cameras were used to quantify marine life in the deeper areas of the KNR. These systems consist of high definition cameras (Sony Handycam FDR-AX33 4K Ultra-High Definition video with a 20.6 megapixel still image capability) in a 33-cm diameter borosilicate glass sphere that is rated to ~7,000 m depth [29]. Viewing area per frame for the cameras is ca. 17 m2, depending on the steepness of the slope where the camera lands. Cameras were baited with ~ 1 kg of frozen sardines and deployed for ~ three hrs. Lighting at depth was achieved with a high-intensity LED array. Depth gauging was accomplished using an internal logging pressure sensor, or navigation charts in cases of sensor fail. The cameras were weighted with a 12-kg locally procured biodegradable sandbag weight and descended at a rate of ~1 m s-1. At the programmed time, sandbag weights were automatically released, allowing the cameras to return to the surface.

Video footage was annotated for taxa present (identified to the lowest possible taxonomic level), as well as for maximum number of individuals of a given taxon per video frame (MaxN), which provides a metric of relative abundance. Frequency of occurrence (Freq. occ. %) for each taxon observed was calculated as the percentage of incidence across all deployments. The substrata for each camera deployment were classified into standard geological categories consisting of mud, pebble, cobble, and boulder. Seafloor type was defined by the approximate percent cover of the two most prevalent substrata in each habitat patch. The first type was the substratum accounting for ≥ 50% of the patch, and the second most prevalent substratum accounting for an additional ≥ 30% of the patch.