Marine ecosystem of Bransfield strait, Admiralty bay and around of Joinville and Elephant islands. ANTAR XXII

Abstract

In the austral summer 2014, the Instituto del Mar del Peru developed the scientific XXII Peru Campaign to Antarctica, XXII ANTAR, aboard the BIC Humboldt. The results of research on the Antarctic marine ecosystem disclose the interrelationships between Antarctic krill (Euphausia superba), wildlife and accompanying flora, predators and oceanographic conditions prevailing in the middle. The sea surface temperature varied between -1.5 and 1.6 °C, associated with cold waters of the Weddell Sea, oxygen ranged between 5.3 and 8.24 mL/L. The phytoplankton community was composed of diatoms (i) central: Corethron criophilum, Proboscia alata and Rhyzosolenia styliformis; (ii) pennatales, with more frequent genres like Fragilaria sp., Fragilariopsis sp., Navicula sp. and Pseudo-nitzschia. The most important species of copepods zooplankton community were Calanoides acutus, Metridia gerlachei and Rhincalanus gigas, the quetognato Sagitta sp. and euphausiid Thysanoessa macrura. The pelagic community was dominated by krill E. superba (94.7%), followed by Salpa thompsoni (3.6%), and scyphozoas jellyfish Desmonema sp. and Peryphylla peryphylla (1.34%). Catching fish and ice lantern fish belonging to the families Channichthyidae, Paralepididae and Myctophidae was recorded. Antarctic marine biodiversity verified at depths between 90 and 161 m, was composed of 65 species belonging to 9 taxonomic groups. The dominant species in terms of relative abundance were: Asteroidea (Labidiaster annulatus, Pomachocrinus kerguelensis, Ophiuroidea 1), Teleostei (Notothenia gibberifrons, Chionodraco rastrospinosus and Chaenocephalus aceratus), Tunicata (Styela rotunda), Polychaeta (Phyllodocidae) Porifera (Sponge) Nudibranchia (Doris sp.), Cephalopoda (Paraledone sp., Eledone sp.), Cnidara (gorgonians) and Isopoda (Natatolona sp.). 25 species of seabirds belonging to 3 orders and 8 families were recorded, the most abundant species petrel (Daption capense), followed by petrel silver (Fulmarus glacialoides) and chinstrap (Pygoscelis antarctica) and 7 species marine mammals, belonging to 2 orders and 3 families, represented by observations of cetaceans (75.96%) and pinnipeds (24.04%). Among the cetaceans, they highlighted the humpback whale Megaptera novaeangliae, the fin whale Balaenoptera physalus, B. borealis and B. bonaerensis. Among the pinnipeds, Arctocephalus gazella was the most prevalent species. Wide distribution of krill in the study area were recorded, the largest acoustic densities (>1000 m/mn²) were observed around the Elephant and Joinville Islands; while lower acoustic densities (250-1000 m²/mn²) was recorded in the Bransfield Strait. One hydroacoustic biomass krill 7’330,574 t and 2’926,906 t by methods reflectivity (White Strength, TS) Stochastic Approximation Distorted Wave (SDWBA) and Greene, respectively estimated. These results were obtained greater than 2013 (876.367 t SDWBA method), mainly due to higher assessed area (Antar XXII, 21,071 nm2, 2014) compared to the previous season (Antar XXI, 8,040 nm2, 2013). The estimated around Elephant Island (4’569,039 t) biomass accounted for 62.3% of all existing biomass in the study area. High values of concentrations of Aromatic Hydrocarbons Total (HAT) and mercury in seawater in different areas Bransfield Strait, around Deception Island, south of Elephant Island and Admiralty Bay were recorded. High concentrations of mercury in samples of muscle tissue of fish N. gibberifrons (0.18 and 0.36 mg/kg) were observed.