Keywords

1 Introduction

Chilean Patagonia covers a marine area of 121,948 km2 located between Reloncaví Sound and the Diego Ramírez Islands (41° 42'S 73° 02'W; 56° 29'S 68° 44'W); the linear extension of the continental coastline, including fjords, channels, islands, islets and rocky areas, is 100,627 km [69]. This generates marine coastal ecosystems that are among the most biologically structured in the world [13, 31, 38]. The region is characterized by pronounced physical and chemical gradients, which together with the factors mentioned above result in highly diverse sublittoral habitats, considered “hotspots” of marine diversity [21, 31], which are among the least studied in the world [4].

There were no taxonomic surveys and biodiversity inventories of hard or consolidated sublittoral bottoms in Chilean Patagonia until about 20 years ago. Over the last 20 years, our team has used SCUBA diving (self-contained underwater breathing apparatus) to conduct numerous on-site inventories of macrobenthicepifauna, mainly on hard bottoms and rocky walls, down to 35 m depth. The influence of the low salinity layer (LSL) is very pronounced in the first 10–15 m in these environments but is no longer evident below those depths [39]. According to our studies, the benthic communities of Chilean Patagonia can be divided into three biogeographic provinces with 13 ecoregions (adapted from [31]). Approximately 50% of Chilean Patagonia’s land area is protected, but the 11 marine protected areas (MPAs) represent only 6% of marine Patagonia (excluding areas that are part of the National System of State Protected Wild Areas, see [69]). These MPAs have little or no protection, and there is no integrated conservation system for marine Patagonia [38, 69].

2 Scope and Objectives

Our objectives for this chapter, based on our publications, literature review and scientific observations are: (i) to describe the biocenoses or forests of hard-bottom benthic macroinvertebrates and macroalgae, which are important bioengineering species; (ii) to provide information on the biodiversity of these species for each of the biogeographic provinces; (iii) to identify the main anthropogenic and natural impacts on these benthic systems; (iv) to identify the main knowledge gaps and research opportunities; and (v) to provide recommendations for the protection and conservation of these biocenoses.

3 Methods

Between 1989 and 2019, in the area of Chilean Patagonia between Valdivia (ca., 40°S) and the Beagle Channel (ca., 55°S), we: (i) collected samples of sublittoral benthic macroinvertebrates (>5 mm length) from hard bottoms at 405 sites to a maximum depth of 35 m using SCUBA diving (Fig. 1a); (ii) recorded videos of many of these macroinvertebrates at 93 sites between 0–500 m depth with a remotely operated vehicle; (iii) conducted photo-transects at 53 sites down to 28 m (49 photos at seven different depths at each site); (iv) have created species occurrence lists of 26 taxa from ten phyla at 167 sites since 2011, using a predefined list of 70 species that can be reliably identified from high-quality underwater photos; and (v) photographed, collected, documented and preserved 12,181 specimens of these macroinvertebrates. We also analyzed the literature for reliable taxonomic records and compiled a list of 1,811 species of benthic macroinvertebrates for Chilean Patagonia [31]. The information is contained in the PAtagonia MArine DAtabase (PAMADA), which is a collection of biological (mainly benthic), physico-chemical and oceanographic data, currently containing 20,159 species occurrence points. This chapter contains a summary of this information. We have also reviewed the Chilean National Inventory of Species Conservation Category according to the Wildlife Species Classification Regulations of the Ministry of the Environment, (in Spanish Ministerio del Medio Ambiente, MMA) (https://clasificacionespecies.mma.gob.cl/).

Fig. 1
3 maps of Patagonia. A, Chilean Patagonia with northern and central Patagonia with multiple survey sites. B and C, Patagonia with locations of prominent sublittoral marine invertebrate forests and a site with ascidian accumulation marked.

a Map of Chilean Patagonia showing the boundaries of the provinces of Northern Patagonia (NP), Central Patagonia (CP) and Southern Patagonia (SP) and the sites surveyed (black dots) between 1998 and 2019. b and c Maps of the most prominent sublittoral marine invertebrate forests. No sublittoral invertebrate forests were observed in SP

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4 Results

4.1 Biogeographical Subdivisions in Chilean Patagonia and Latitudinal Trends in the Number of Hard-Bottom Sublittoral Macroinvertebrate Species

Our studies of sublittoral hard-bottom marine macroinvertebrates at more than 400 dive sites in Chilean Patagonia allow us to propose a latitudinal division of Chilean Patagonia into three marine biogeographic provinces: (i) Northern Patagonia (NP): 42°–47°S; (ii) Central Patagonia (CP): 47°–54°S; and (iii) Southern Patagonia (SP): 54°–56°S (Fig. 1a). Each province includes three main ecoregions: Fjords, channels and exposed coast. Due to geomorphological aspects and other oceanographic conditions, at least four other ecoregions are proposed: (i) the east coast of Chiloé Island, with extensive muddy bottoms; (ii) the Corcovado Gulf; (iii) the Gulf of Penas; (iv) the large semi-enclosed inland seas in SP, such as the Otway and Skyring Sounds [31].

In the Taitao Peninsula (47°S), which separates the NP and CP provinces, a part of the West Wind Drift Current meets the continent, and the division between the Cape Horn Current and the Humboldt Current occurs. The boundary between the CP and SP provinces is in the deep Straits of Magellan (54°S), where a strong component of the circumpolar current predominates, flowing through the strait from west to east, thus hindering latitudinal dispersal of organisms with planktonic larvae [58]. In comparison to the glacier-free fjords of NP, the intracontinental fjords in CP and SP are strongly influenced by glacial erosion. In the NP province, the sea anemone Anthothoe chilensis is abundant on mussel banks, other species restricted to this region are the encrusting anemone Parazoanthus elongatus and gorgonians of the genus Swiftia; there are also several bioengineering benthic invertebrates (sensu [42], such as stony corals (Fig. 2a), ectoprocts, brachiopods (Fig. 2b), mussels, barnacles and gorgonians (Primnoella chilensis and Thouarella spp.) [31].

Fig. 2
4 photos. A, a dense forest of Desmopyhllum dianthus stony corals. B, a Magellania venosa brachiopod forest. C, a Thouarella brucei gorgonian forest with feather like strands extending in water. D, Macrocystis pyrifera macroalgal forest with extended algae.

Photographs of sublittoral benthic forests in Chilean Patagonia. a Forest of

Desmopyhllum dianthus stony corals. b Magellania venosa brachiopod forest. c Thouarella brucei gorgonian forest. d Macrocystis pyrifera macroalgal forest

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The fjords in the CP province have subtidal walls with steep slopes and low invertebrate colonization. The soft coral Alcyonium glaciophilum and the gorgonians Acanthogorgia sp. 1 and sp. 2 are species restricted to this province. The presence of hydrocorals, gorgonians (Acanthogorgia spp., Muriceides spp., Thouarella spp. (Fig. 2c), Primnoella chilensis), ectoprocts and sponge gardens is outstanding in the CP channels. In this province, limestone archipelagos such as Madre de Dios harbor a low number of anthozoans, and there are hydrocoral reefs in channels with strong currents.

Brown macroalgal forests are common in shallow coastal sites in the SP Province (Fig. 2d). Anthozoan and decapod species are generally very scarce. However, the anemones Stomphia coccinea and Bunodactis octoradiata, the decapod Pagurus forceps and the bivalves Aequiyoldia eightsii, Cuspidiaria patagonica, Policordia radiata and Cyclochlamys multistriata are typical for this province [31]. Our current database for species numbers of five hard-bottom invertebrate taxa from Chilean Patagonia shows that (i) anthozoans initially increase in species numbers south of Puerto Montt (42°S) and then decrease toward the extreme south: 15 species at 40°S; 41 at 45°S; 37 at 50°S and 15 at 55°S; (ii) gastropods decrease toward higher latitudes: 34 species at 40°S; 28 at 45°S; 25 at 50°S and 24 at 55°S; (iii) bivalves and pycnogonids show relative stability in the number of species throughout Patagonia: 35 species of bivalves and six species of pycnogonids at 40°S; 39 and 11 species at 45°S; 38 and 9 species at 50°S; 37 and 10 species at 55°S, respectively; (iv) decapods decrease toward higher latitudes across Patagonia: 59 species at 40°S; 48 at 45°S; 42 at 50°S and 14 at 55°S.

4.2 Sublittoral Benthic Hard-Bottom Species of Outstanding Importance

4.2.1 Sublittoral Forest-Forming Species of Macroinvertebrates and Brown Macroalgae

Our inventory of benthic biodiversity allowed us to identify 13 communities of different macroinvertebrates and brown macroalgae that form sublittoral forests (Figs. 1 and 2). These habitat-forming species or ecosystem bioengineers [42] modulate the abiotic and biotic environment and therefore maintain a self-organized habitat, which is used by diverse associated fauna [62]. Forest-forming invertebrates and algae are subdivided into five subsets: (i) species with massive endoskeletons: cold-water stony corals, hydrocorals and Ectoprocta (ii) species with massive exoskeletons: bivalves, brachiopods and barnacles; (iii) species with scattered calcified structures or with spicules: gorgonians and sponges; (iv) non-calcifying invertebrate species; (v) macroalgal species (see details in Table 1).

Table 1 Sublittoral forests of macroinvertebrates and brown algae in the coastal zone of Chilean Patagonia. CP: Central Patagonia
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  1. (i)

    Sublittoral forests of cold-water stony corals, hydrocorals and ectoprocts. The cosmopolitan stony coral Desmophyllum dianthus (Scleractinia) has been described in Chilean Patagonia from 7 to 2,460 m depth, with a distribution between 42°–56°S [23]. D. dianthus grows on steep rock faces with a slope > 80° and on lower surfaces of boulders and below the influence of the LSL. In NP, it can form banks with a density of up to 1,500 individuals/m2 and has a maximum length of up to 40 cm [31].

    Individuals can grow on top of others with up to five individuals, forming colony-like structures. These coral banks are found between 20–400 m in Comau [22], Reloncaví and Reñihue fjords [23]. A patch of 100 m2 was also found in Pitipalena Fjord (Fig. 1b). The species is scarce in the rest of Patagonia, with accumulations of small individuals at the mouth of the Messier Channel. The species is a sessil predator [37] and grows relatively fast [41], with marked seasonal reproduction and high fecundity [20]. Hundreds of species are associated with these forests, including sponges, echinoderms, snails, anemones, ectoprocts, polychaetes, scleractinian corals, brachiopods (Magellania venosa), bivalves (Aulacomya atra and Acesta patagonica) and the fish Sebastes oculatus.

    The hydrocoral Errina antarctica (Stylasterina) is distributed in semi-exposed and exposed environments below the LSL from south of Chiloé (43°S) to the Subantarctic islands between 10–771 m. In CP, it is locally abundant in some channels with strong currents; its colonies can grow fan-shaped on steep walls or as bushes on the bottom of channels, reaching up to 40 cm in diameter and creating reef-like formations [33]. Hydrocoral reefs provide habitat and shelter for numerous species (58 associated taxa have been identified, [78] and serve as substrate for sedentary filter-feeding species such as the crinoid Gorgonocephalus chilensis and the feather star Florometra magellanica. The dead areas of these colonies are used by a large number of sessile, sedentary, mobile and burrowing organisms [30]. Aggregations and sublittoral forests of several species of calcifying ectoprocts such as Aspidostoma giganteum, Adeonella spp. and Microporella hyadesi occur in exposed or semi-exposed sites with strong currents. Individuals reach a diameter of up to 30 cm and create highly structured habitats for semi-sessile and mobile organisms such as the hermit crab Pagurus comptus, the gastropod Calliostoma consimilis and ophiuroids (e.g. Ophiacantha rosea).

  2. (ii)

    Sublittoral forests of bivalves, brachiopods and barnacles. Numerous sites in Patagonia’s rocky intertidal zone are dominated by bivalves such as Mytilus chilensis and Brachidontes purpuratus; the former being more abundant in fjords and channels and the latter on the exposed coast. Aulacomya atra is abundant in the subtidal zone down to 20 m. The mussel beds can be up to 30 cm thick and host numerous invertebrate species, especially when the beds have various age structures, such as the anemones Anthothoe chilensis (NP), Metridium senile (a species introduced to Patagonia, being on the rise throughout North and South Patagonia, [35], and creating huge problems for sea urchin fisherfolks, gastropods of the genus Crepidula, echinoderms, sponges, polychaetes and crustaceans, which typically live inside the matrix of the beds.

    In some fjords of NP (Reloncaví, Comau, Reñihué, Pitipalena) and in Magdalena Sound, there are forests of the brachiopod Magellania venosa [6, 7]. This species can numerically dominate the benthos in Comau Fjord on steep rocky walls between 15–35 m, where densities of up to 416 ind./m2 have been observed [6]. The species is also observed in soft bottoms at the mouths of some fjords at depths from 150 to 200 m (e.g. Comau Fjord). Shell growth is rapid, which may explain its high population density and coexistence with mussels [6]. Aggregations of the giant barnacle Austromegabalanus psittacus have been observed on the exposed coast and semi-exposed channels below the LSL with individuals growing on top of each other. At sites with higher and more stable salinity and moderate wave intensity, individuals grow at rates between 0.06 and 0.13 mm/day [45] and can reach heights of up to 30 cm, forming large banks.

  3. (iii)

    Sublittoral forests of gorgonians and sponges. The sea whip Primnoella chilensis dominates on moderately steep slopes of fjords and channels in NP; in this province the gorgonia Swiftia comauensis is restricted to Comau and Reñihué Fjord. Although present in some channels of NP, gorgonians of the genus Thouarella dominate in the channels of CP. The branching gorgonians of the genera Acanthogorgia and Muriceides are restricted to fjords and channels of CP that are impacted by fine sediment. Gorgonian forests provide habitat for numerous species such as the anemone Dactylanthus antarcticus and the nudibranch Tritonia odhneri, which prey or graze on gorgonians of the genera Primnoella and Thouarella [31]. Throughout Chilean Patagonia, in some semi-exposed and exposed sites below 5–10 m, sponges of the classes Demospongiae and Calcarea with calcified spicules form sponge gardens (e.g. Tedania mucosa and Mycale magellanica). These gardens are especially common in the channels of CP, where Amphimedon maresi have three-dimensional structures which provide refuges and habitats for numerous other species. Encrusting sponges often dominate the benthic fauna, especially in the first few meters of wave-exposed sites; a significant percentage of these species have not yet been identified. Approximately 70% of the sponge species collected in our surveys had not yet been described [31]. Some invertebrates such as the starfish Poraniopsis echinaster and the gastropods Fissurellidea sp. and Buchanania onchidioides may prey on sponges.

  4. (iv)

    Sublittoral forests of polychaetes, ascidians, and encrusting anemones. Forests of the polychaete Chaetopterus variopedatus are present in fjords and channels of CP, with dense fields of up to 100 m2 at depths between 10–20 m. The tubes of these polychaetes can reach up to 50 cm length and provide habitat for a great variety of species, such as hydrozoans and sponges (Halisarca magellanica), decapods (Campylonothus vagans) and echinoderms (Gorgonocephalus chilensis). Forests of other non-calcifying invertebrate species are very scarce in the biogeographic provinces of Patagonia; some patches of encrusting anemones Parazoanthus elongatus (Comau and Reñihué Fjord and Slight Estuary) are found in NP, and an accumulation of the ascidian Sycozoa sigillinoides in the Beagle Channel (SP).

  5. (v)

    Sublittoral brown macroalgal forests. The combination of high nutrient load and a salinity between 33 and 34 along the exposed rocky coasts of Chilean Patagonia creates the conditions for the formation of sublittoral forests of brown macroalgae that provide habitat, shelter and food for a large diversity of species [2, 8, 15, 28]. The main forests are formed by: (i) Macrocystis pyrifera, which can reach up to 15 m in length and is found in shallow intertidal and subtidal habitats down to 15–18 m [51, 54, 76, 77], (ii) Durvillea incurvata (30°–43°S) and D. antarctica (44°–55°S) [26], which are commonly found in shallow, exposed or very exposed inter- or subtidal habitats; and (iii) the genus Lessonia, which in Patagonia includes two species: L. flavicans (47°–55°S; [65]), which forms inter- and subtidal forests in the Magallanes Region, and L. spicata (30°–48°S), which forms intertidal forests at semi-exposed and exposed coasts [61]. Ojeda and Santelices [54] described the autecology and population dynamics of M. pyrifera, while [64] summarized the ecological relationships of invertebrate and algal communities in these Patagonian forests. Trophic webs of up to 122 invertebrate and algal species have been described for these forests [1, 3, 15, 52, 59] and in mixed forests of M. pyrifera and Lessonia spp. [27]. Generalist top predators such as the starfish Cosmasterias lurida [74], the crab Peltarion spinosolum, carnivorous anemones and predatory nemerteans are prominent in the trophic webs. Vásquez et al. [75] studied the trophic webs of the sea urchins (Loxechinus albus, Pseudechinus magellanicus, Arbacia dufresnei and Austrocidaris canaliculata) living in these forests and found that there was no trophic competition among adults, and that predation on adult urchins is not an important factor in regulating their densities.

  6. (vi)

    Sublittoral rhodolith beds. Red coralline algae form rhodolith beds (unidentified species of Melobesiodeae; [60]. Rhodoliths extend from shallow zones to the maximum depth of the photic zone (down to 270 m), creating habitat, refuge, or settlement sites for a large number of marine species. For Chilean Patagonia, there is only one report of rhodolith beds in the Guaitecas and Madre de Dios archipelagos [46].

4.3 Sublittoral Benthic Macroinvertebrate Hard-Bottom Species in Chilean Patagonia Included in the Ministry of Environment’s List “Conservation Category According to the Wildlife Classification Regulation”

The list of species whose continued existence is considered problematic, published by the Chilean Ministry of Environment,Footnote 1 is based on expert opinions. This list includes six sublittoral macroinvertebrate species: (i) the gorgonian Swiftia comauensis, only observed in Comau and Reñihué Fjord, 42°10' to 42° 30'S 72°E (Fig. 3c) is considered to be “critically endangered”; (ii) the sea whip Primnoella chilensis (41°–55°S), also present in Brazil and Argentina (Fig. 3b) is categorized as “endangered”; (iii) the shallow water ecotype of the hydrocoral Errina antarctica (43°–54°S), also present in the southwest Atlantic and Subantarctic islands (Fig. 3a), is considered “vulnerable”; (iv) the cosmopolitan stony coral Desmophyllum dianthus (42°–53°S), also present in the Juan Fernández archipelago (Fig. 3c) is considered to be “near threatened”; (v) the rock shrimp, Campylonothus vagans (41°–56°S), which is also present in the southwest Atlantic (Fig. 3B) is categorized under “minor concern”; (vi) for the non-retractile anemone, Bolocera kerguelensis, 41°–54°S; also present in the Antarctic and southwest Atlantic, and the deep-water ecotype of the hydrocoral Errina antarctica the category “data deficient” applies.

Fig. 3
3 maps of Chilean Patagonia. The maps mark the location of Bolocera karguelensis in Northern Patagonia, Errina antarctica in Central Patagonia, Campylonotus vagans, Primnoells chilensis, and Desmophyllum dianthus are present in all 3. Swiftia comauensis is in the Northern Patagonia.

Distribution map of benthic invertebrate species of sublittoral hard bottoms of Chilean Patagonia included in the list of conservation categories of endangered wildlife; according to the Wildlife Species Classification Regulations (MMA). a Bolocera kerguelensis (“data deficient”), Errina antarctica (shallow water ecotype: “vulnerable”, deep water ecotype: “data deficient”) b Campylonotus vagans (“least concern”), Primnoella chilensis (“endangered”) c Swiftia comauensis (“critically endangered”), Desmophyllum dianthus (“near threatened”)

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4.4 Threats to Marine Macroinvertebrate Biodiversity in Chilean Patagonia from Local Stressors

Patagonian marine ecosystems are subject to a vast anthropogenic transformation that can, and in many cases already has, affected biological conservation. An important number of species that form invertebrate forests are unique, fragile and sensitive to increased sedimentation, eutrophication, use of various chemicals, overfishing and deforestation [11, 12, 40, 50]. The main threats to the benthic communities of Patagonian fjords and channels are aquaculture, infrastructure and industrialization projects, fishing and invertebrate harvesting [25, 55, 57]. The steady increase in salmonid production over the last two decades has had an important impact on the ecology of Chilean Patagonia, for example, eutrophication and increased sedimentation poses a threat to benthic species [36]. The combination of high solar radiation, increased surface temperature and decreased precipitation associated with climate change, especially in El Niño years, has also resulted in a more pronounced vertical stratification of the water column. Because of the above factors, harmful algal blooms (HABs) are occurring more frequent and widespread in Patagonia [43, 47]. When the microalgae in these blooms die, they sink, and there is increased oxygen consumption by bacterial flora. This leads to hypoxia events, which can cause stress, mortality, and changes in food webs [48, 56]. For example, in 2012, 99% of the specimens of the coral D. dianthus died along approximately 15 km coastline of Comau Fjord, possibly due to a hypoxia event in combination with elevated hydrogen sulfide levels [18, 24]. The biological changes observed in Comau Fjord between 2003 and 2013, such as the decrease in the abundance of gorgonians, ectoprocts and long-lived anemones [32], could also be a consequence of the constant increase in the production and growth of salmonids in this fjord during these years [9, 10]. The continued use of chemical products by the industry, including antibiotics and crustacean control products [10], is harmful to Patagonian ecosystems. The abundance of some decapods has declined significantly in some Patagonian locations, as drugs against salmon lice have lethal and sublethal effects on crustacean larvae [29, 32].

The amount of waste remaining in the water and boat traffic have increased considerably during recent decades [32]. Several infrastructure and industrialization projects accompany this development, such as the construction or expansion of coastal roads and harbors. This kind of construction increases the exposure of benthic fauna to sediment and can destabilize the terrestrial vegetation layer, leading to landslides, which in turn can cause local tsunamis [66]. Artisanal fishing has increased significantly in Chilean Patagonia over the last 25 years [50], and the heavy extraction of species such as the gastropod Concholepas concholepas (loco), mussels, giant squid and algae may cause modifications in the benthic ecosystem, including macroinvertebrate forests and marine algae [32]. There is evidence of the direct impact of fisheries on Patagonian ecosystems. For example, the mussel banks of Reloncaví Fjord and Comau Fjord were considerably reduced between 2003 and 2013 [32, 49], and at some locations, e.g. in Comau Fjord, anemones monopolized the freed space. [17] demonstrated that the extraction of the urchin L. albus affects both the exploited populations and the associated benthic communities. Volcanic eruptions in Patagonia also have caused adverse effects on marine ecosystems. For example, the eruption of the Chaitén Volcano in 2008 released large amounts of sediments that affected the filtration processes of benthic organisms (Rogers, 1990). Volcanic activity can also affect pH and alkalinity and increase methane and sulfide levels in the water, negatively affecting the survival of benthic organisms [73].

5 Discussion

Our analyses of the distribution and diversity of the hard-bottom sublittoral macroinvertebrate fauna of Chilean Patagonia suggest the existence of three biogeographic provinces with different species assemblages: NP, CP, and SP. These coincide in latitude with what [63] classified as three ecoregions: Chiloé-Taitao, Kawésqar and Magallanes. Our results also indicate the existence of three ecoregions in each province: fjords, channels and exposed coasts (nine ecoregions in total) and at least four additional ecoregions (see results) characterized by variables such as salinity, water temperature, currents, slope and substrate [71].

This chapter describes 13 Patagonian macroinvertebrate and macroalgal communities that form sublittoral forests. These bioengineering species maintain self-organized habitats, host hundreds of species and are fundamental to Patagonian ecosystems. Only six of these species of benthic macroinvertebrates are included in the Ministry of Environment’s list “Conservation Categories according to the Wildlife Species Classification Regulations”, mainly due to the low number of existing scientific studies. More research and long-term monitoring are required to understand the threats to benthic macroinvertebrates and to develop conservation strategies.

Our records show that the number of species of anthozoans, gastropods and decapods decreases from low to high Patagonian latitudes; for decapods this agrees with the observations of Thatje and Arntz [68]. For bivalves and pycnogonids, a stable number of species was observed across latitudes. However, Valdovinos et al. [72], who analyzed all described Patagonian mollusks, reported a decrease in species numbers from low to high latitudes. Our approach of using only valid species with records confirmed by a specialist, which are observed atleast five sites, may account for the disparity of these results.

In contrast to the brown macroalga M. pyrifera forests in the Northern Hemisphere (California, Alaska), where sea urchins control kelp abundance and distribution, sea urchins do not play such a structuring ecological role in the Magallanes Region (Beagle Channel) [14]. While the sea otter Enhydra lutris nereis is a key predator that controls the density of urchins Strongylocentrotus spp. in Californian kelp forests, there is no such key predator of L. albus in the Magellanic forests [14, 15], see also [16].

The marine ecosystems of Chilean Patagonia are threatened by local anthropogenic (salmon farming, transport, HABs, and others), natural (volcanic eruptions) and global (climate change) stressors, natural stressors being of inferior importance. The NP biogeographic province is the most threatened of Patagonian marine ecosystems [47, 50]. However, salmon farming, artisanal and industrial fishing, and transport activities are expanding in CP and SP [50, 53]. A synthesis of some of the major local (eutrophication of waters, HAB) and global (climate change) threats in the marine areas of Chilean Patagonia can be found in [12, 34, 47, 67, 70].

The alteration or disappearance of species in marine ecosystems is imperceptible to the public and authorities without constant and long-term monitoring, as they occur below the surface. Patagonian marine ecosystems are at high risk of losing species and diverse ecosystem services [12, 40], those species forming sublittoral forests of macroinvertebrates and macroalgae should be protected as a priority. Marine Protected Areas (MPAs) are one of the most widely used tools for this purpose worldwide. Current knowledge suggests that between 25 and 75% of the global coastal zone would need to be protected to avoid serious ecological crises [5]. Tecklin et al. [69] described the current situation of MPAs in Chilean Patagonia in detail, pointing out that excluding the coastal-marine extensions of the large Patagonian National Parks, only 6% of the marine area is under (paper) protection. Edgar et al. [19] compared MPAs around the world and concluded that four of five characteristics must be met for an MPA to be effective: large size, isolation (from impacted areas), age older than 10 years, good surveillance, and high level of protection. No MPA in Chilean Patagonia meets these conditions. In addition to creating an integrated system of MPAs in Patagonia, including some with high protection or without intervention (no-take), efforts must be made to regulate fisheries [50] and revise current salmon farming practices [11, 47].

Fig. 4
A photograph of a forest of Desmophyllum dianthus stony corals.

A cold-water coral bank dominated by Desmophyllum dianthus in Comau Fjord, 30 m depth

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6 Conclusions and Recommendations

We provide the following recommendations addressing knowledge gaps, urgent conservation needs and threats to the Patagonian hard-bottom benthic communities and ecosystems that make up sublittoral forests.

  • The greatest gaps in knowledge are found in the channels and exposed coasts between 50° and 56°S, which are generally difficult to access due to climate instability and the high cost of expeditions (Fig. 1a). However, there is an urgent need to promote and fund basic research to understand ecosystem structures and dynamics in all sublittoral ecoregions, especially of western Patagonia and to develop long-term time series.

  • The status of sublittoral macroinvertebrate species classified by the MMA as having conservation problems is still poorly understood. Further research efforts are needed to obtain more thorough assessments and to register further species with conservation concerns in the Red List of the International Union for Conservation of Nature.

  • Conservation efforts for the existing MPAs in Patagonia, most of which do not have management plans, monitoring, park rangers or funds to manage them, should be strengthened. The creation of an integrated land‒sea system of MPAs should also be accelerated, including a set of reference or non-intervention marine-coastal areas for each of the biogeographic ecoregions. In addition, oceanographic data collected by the aquaculture industry must be made accessible.

  • The negative impacts of various anthropogenic, global and natural stressors on Patagonian benthic ecosystems should be studied and evaluated as soon as possible, to determine the carrying capacity of the ecosystems. Regarding artisanal and industrial fisheries and aquaculture (especially in NP), it is necessary to apply precautionary fishing and ecosystem principles and introduce sustainable guidelines, such as reducing the nutrient loads entering the fjords and channels to avoid hypoxia. In addition, the carbon footprint of these activities needs to be significantly reduced, to lower the global impact.