The vast and complex coast of the Magellan Region of extreme southern Chile possesses a diversity of habitats including fjords, deep channels, and extensive kelp forests, with a unique mix of temperate and sub-Antarctic species. The giant kelp Macrocystis pyrifera plays a key role in structuring the ecological communities of the entire region, with the large brown seaweed Lessonia spp. There were clear differences in marine communities among these sub-regions, with the lowest diversity in the fjords. Dropcam surveys of mesophotic depths 53— m identified 30 taxa from 25 families, 15 classes, and 7 phyla. While much of these deeper habitats consisted of soft sediment and cobble, in rocky habitats, echinoderms, mollusks, bryozoans, and sponges were common.
|Country:||Sao Tome and Principe|
|Published (Last):||1 May 2005|
|PDF File Size:||17.38 Mb|
|ePub File Size:||16.75 Mb|
|Price:||Free* [*Free Regsitration Required]|
The vast and complex coast of the Magellan Region of extreme southern Chile possesses a diversity of habitats including fjords, deep channels, and extensive kelp forests, with a unique mix of temperate and sub-Antarctic species.
The giant kelp Macrocystis pyrifera plays a key role in structuring the ecological communities of the entire region, with the large brown seaweed Lessonia spp.
There were clear differences in marine communities among these sub-regions, with the lowest diversity in the fjords. Dropcam surveys of mesophotic depths 53— m identified 30 taxa from 25 families, 15 classes, and 7 phyla. While much of these deeper habitats consisted of soft sediment and cobble, in rocky habitats, echinoderms, mollusks, bryozoans, and sponges were common. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All data are available within the paper, its Supporting Information files, and at Dryad: doi: The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. They produce the largest biogenic structures in the ocean, are important in marine carbon cycles, and constitute one of the most diverse and productive ecosystems on the planet [ 5 — 8 ].
Kelp forests are important recruitment and nursery habitat for numerous species and provide a key link between nearshore and deep-water habitats [ 2 , 4 , 9 ]. The biomass and persistence of these kelp forests are controlled by many biotic and abiotic factors including disturbance from large wave events, seasonal and interannual nutrient inputs, top-down consumer interactions, and anthropogenic degradation of habitat [ 10 — 15 ]. The relative impacts of these forces are often difficult to tease apart since there have been major reductions in kelp forest community biodiversity over the past few centuries, leading to a lack of understanding of what the natural community was like in the past [ 16 — 19 ].
The vast and complex Magellan Region of extreme southern Chile consists of a diversity of habitats including fjords, deep channels, inland seas, glaciers, and extensive kelp forests that are the product of glacial and post-glacial processes [ 20 ], which have created remarkably high levels of terrestrial endemism and the largest temperate forests in the Southern Hemisphere [ 21 — 23 ].
The region still contains largely unfragmented ecosystems, low anthropogenic impacts, and very low population density [ 23 ]. This region is the confluence of water masses from three great oceans Pacific, Atlantic, and Southern oceans , with a mix of species of temperate and sub-Antarctic distributions that creates a unique area of marine endemism with high biodiversity value [ 26 — 27 ].
The region contains critical habitats for marine mammals of global conservation concern e. Today only 2, people live in the Magellan region, most of them in Puerto Williams, which is located on Navarino Island in the Beagle Channel and is the southernmost town in the world [ 36 ]. The Patagonian toothfish Dissostichus eleginoides and southern hake Merluccius australis fisheries were once important to the economy of the region, but severe overfishing in recent years has greatly reduced the catch of these species [ 37 — 38 ].
The southern king crab Lithodes santolla and false king crab Paralomis granulosa fisheries are currently the most important economic activities in the region, but large declines have recently been noted for these species as well [ 36 ]. The marine ecosystems of the Magellan Region are diverse with unique biogeography, yet have been poorly studied to date [ 39 ]. The region possesses the southernmost kelp forests in the world and therefore has extremely high biodiversity value.
The importance of these shallow water habitats as nurseries for commercially valuable resource species and the interconnectivity among deep and shallow habitats is largely unknown.
The vast expanses of unfragmented habitats within the region have been recognized for their pristine condition, but efforts to maintain this healthy ecological state are challenged by a variety of human impacts including: overfishing, aquaculture, tourism, transportation, and insufficient management capacity [ 36 , 40 ].
Data were collected by all authors in a collaborative effort. This study was carried out in strict accordance with the recommendations of the Canadian Council on Animal Care guidelines on euthanasia of animals used in science.
Fish were euthanized using clove oil prior to preservation, and all efforts were made to minimize suffering. Our data are available at Data Dryad: doi: The park, established in , was the first marine national park in Chile, and was specifically designated to conserve feeding areas for humpback whales and breeding areas for Magellanic penguins Spheniscus magellanicus and South American sea lions Otaria flavescens [ 41 — 42 ].
The 67,ha park is also important for other marine mammals such as Antarctic Minke whales Balaenoptera bonaerensis , Orcas Orcinus orca , and southern elephant seals Mirounga leonina. Magellan Region, B. Cape Horn Archipelago, C. Francisco Coloane Marine Park, D. The waters of the Straits of Magellan are fresher, and cooler than the open shelf waters owing to the effects of melting water from numerous glaciers [ 43 ]. This semi-closed fjord system possesses an extensive and complex seascape that harbors a unique and diverse suite of species [ 44 — 45 ].
Cape Horn is the southernmost headland of the Tierra del Fuego Archipelago, marking the northern boundary of the Drake Passage where three great oceans meet [ 46 ]. The weather around Cape Horn is extreme, owing to intense winds, large waves, strong currents, and icebergs, making it notorious as one of the most hazardous shipping route in the world [ 50 ].
Cabo de Hornos National Park encompasses the entire Cape Horn Archipelago and is comprised of a series of islands and islets, including the main landmasses of Wollaston and Hermite islands. The terrain is almost entirely treeless peat except for some small wooded areas of beech forest Nothofagus spp. The archipelago is divided into a smaller northern group with six islets, and a larger southern group, separated by a 3-km wide pass. These islands are the southernmost inhabited outpost of South America, and are an important nesting site for numerous seabird species, including the black-browed albatross Thalassarche melanophris , grey-headed albatross T.
Characterization of the benthos was conducted by scuba divers along two 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 kelp forest.
For sessile and mobile invertebrates, the number of individuals was estimated on 1-m of either side of the transect line 50 m 2. For colonial organisms sponges, some cnidarians, bryozoans, and some tunicates colonies, rather than individuals, were counted.
When a species was extremely abundant i. A second diver counted the number of kelp Macrocystis pyrifera and Lessonia spp. Atmospherically-corrected imagery were obtained from the United States Geological Survey earthexplorer. Emergent canopy biomass density was estimated from the three sub-regions using Multiple Endmember Spectral Mixing Analysis [ 55 ].
This procedure models each pixel as a linear combination of one static kelp canopy endmember and one of 30 seawater endmembers unique to each image. The use of dynamic seawater endmembers accounts for changing water conditions e. The fraction of kelp canopy within each pixel is determined from the model with the lowest root mean squared error. Canopy biomass density was estimated from the derived kelp fraction using an empirical relationship established for giant kelp from diver-based canopy biomass estimates [ 56 ].
Regional giant kelp canopy biomass dynamics can be subject to strong seasonal patterns, especially in areas with periodic wave disturbance, nutrient inputs, and increased seasonal light cycles [ 57 — 59 ]. For this reason, only austral summertime imagery was used in the analysis December —March to coincide with anticipated kelp canopy biomass maximums and diver sampling.
Areas with persistent cloud cover during this time frame such as Hermite Island in western Cape Horn were filled with earlier Landsat 8 imagery for use in figures but were not included in the analysis. At each survey site, a scuba diver counted and sized all fishes within 1-m of either side of a 25 m transect line 50 m 2.
The transect extended to the surface or as far as visibility allowed, including species associated with the kelp canopy and water column. Total fish lengths were estimated to the nearest cm. Fish collections were conducted opportunistically using several methods.
Fish were also collected by hand or dip net from beneath stones in the upper to mid-intertidal zone exposed at low tide. We also deployed a Dropcam Mini, encased in a cm diameter borosilicate glass sphere and rated to 5, m. Viewing area per frame for both cameras was between 2—6 m 2 , depending on the steepness of the slope where the Dropcam landed. The relative abundance of each species was calculated as the maximum number of individuals per frame MaxN. The substrata for each Dropcam deployment was classified into standard geological categories following Tissot et al.
Seafloor type was defined by a two-letter code representing the approximate percent cover of the two most prevalent substrata in a habitat patch. Post hoc comparisons between sub-regions were tested using contrasts of the least squares means. In-situ measures of kelp taxa densities, and benthic assemblage characteristics e. A Bray—Curtis similarity matrix was created from abundance of benthic taxa, benthic functional groups, and fish species.
Sub-region was treated as a fixed factor. SIMPER identified the taxa most responsible for the percentage dissimilarities between islands using Bray-Curtis similarity analysis of hierarchical agglomerative group average clustering [ 66 ].
Principal Coordinate Analysis PCO was used to compare benthic and fish assemblage structure among sub-regions. Transect depths averaged During the expedition, water temperatures at 10 m around Francisco Coloane MP averaged 8.
Salinity averaged Kelp forests were the dominant nearshore marine ecosystem in the Magellan Region, with the giant kelp Macrocystis pyrifera being the most conspicuous component of this community. In many locations, the large brown seaweed Lessonia spp.
Kelp extent was higher on the eastern and northern coasts of the Cape Horn Archipelago, likely due to shelter from the prevailingly wind and swell that originate from the west Fig 2.
Francisco Coloane Marine Park, C. Overall in situ densities of M. Stipe densities of M. Densities of Lessonia spp. Box plots showing median black line , mean red dashed line , upper and lower quartiles, and 5th and 95th percentiles. Kruskal-Wallis Rank Sum comparisons among regions were statistically different for Lessonia spp. We recorded invertebrate taxa from 18 classes or infraclasses and 10 phyla during our surveys S1 Table. Mollusks were the richest phyla with 32 taxa, followed by echinoderms with 20, and sponges with Of the mollusks, gastropods were by far the most specious and abundant.
The order of magnitude greater abundance of individuals at Cape Horn was driven by the bivalve Gaimardia trapesina. Statistical results of Kruskal-Wallis rank-sum test X 2 with Steel-Dwass test for unplanned multiple comparisons. There was clear separation of sampling locations by sub-region in ordination space and relatively high concordance within sub-regions based on taxa abundance Fig 4. The sea star Porania antarctica drove the separation of Francisco Coloane, while the sea star Cosmasterias lurida and the painted shrimp Campylonotus vagans drove the separation of sites around Cape Horn.
The encrusting red sponge Scopalina sp. The sea cucumber Cladodactyla crocea croceoides accounted for The bivalve Gaimardia trapesina comprised Values are mean no. The dissimilarity in benthic assemblages based on taxa abundance between Francisco Coloane and Cape Horn was Active suspension feeders comprised If this species is excluded, then active suspension feeders accounted for Benthic assemblage structure based on abundance by functional group showed less separation among sub-regions, but identified a few unique locations that stood out from the rest Fig 4.
The two transects at Station 1 located in Canal Barbara within Francisco Coloane MP were extreme outliers from all other stations and were explained by the high abundance of the deposit feeding ophiuroid, Ophiactis asperula.
Cape Horn and Other Stories from the End of the World
Goodreads helps you keep track of books you want to read. Want to Read saving…. Want to Read Currently Reading Read. Other editions. Enlarge cover.
John Muir quote here