Fig 1.
Distribution of sampling sites in subpolar fjords.
Boxes indicate the subpolar WAP fjords (1) Andvord, (2) Flandres and (3) Barilari Bays. Panels 1–3: multibeam bathymetry superimposed on satellite imagery of the three WAP fjords. White lines indicate phototransect positions: I = inner basin (IA = inner basin A and IB = inner basin B); M = middle basin; O = outer basin; and MTH = fjord mouth. ‘G’ indicates the location of a tidewater glacier. Note that each fjord has multiple tidewater glaciers 10–15 km long carrying ice from the Peninsula ice cap (previously described by [46]). Data available from the U.S. Geological Survey. Satellite images are public domain USGS Products. Reprinted from [44].
Table 1.
Station locations and environmental CTD data for megacore-collected specimens of Ptychogastria polaris from Andvord and Flandres Bays.
Fig 2.
Representative images of the seafloor and the trachymedusa Ptychogastria polaris in Andvord and Flandres Bays.
Typical view and occurrence of P. polaris in the (A) outer basin of Andvord Bay and (B) inner basin A of Flandres Bay. Scale bars are 1 cm. (C) Close-up view of P. polaris in the outer basin of Andvord Bay. Scale bar is 2 cm. (D) Bell diameter measurements taken in three horizontal directions (X, Y and Z). Note that black arrows are used to indicate the position of a representative selection of individual P. polaris in panels (A-C). Other P. polaris not identified by black arrows in the field of view were still counted.
Table 2.
Seafloor photosurveys undertaken in Andvord, Flandres and Barilari Bays.
Fig 3.
Morphological and molecular representations of Ptychogastria polaris.
(A) Photograph of a live P. polaris, as photographed by Maria Stenzel, Photographer, collected by megacore in the outer basin of Andvord Bay, WAP (64.77934' S, 62.72885' W), 556 m, 22 February 2010 (Cruise NBP10-01, CRS1339). Scale bar is 1 cm. Reprinted from http://mariastenzel.photoshelter.com under a CC BY license, with permission from Maria Stenzel, original copyright 2010. (B) In situ photograph of the subboreal specimen of P. polaris collected off Okushiri Island, Sea of Japan (42.30216' N, 139.4744' E), 1062 m, 10 March 2012 (Cruise KR12-07, Dive no. 7K#0549). Scale bar is 1 cm.
Table 3.
Pairwise Kimura-2 parameter distances in % calculated for mitochondrial cytochrome oxidase (COI) from Ptychogastria polaris specimens.
Fig 4.
Bayesian phylogenetic hypothesis of Trachylina, including Ptychogastria polaris.
The phylogenetic tree was rooted on Limnomedusae following [47]. Branches in black indicate a posterior probability ≥ 0.95 while grey branches represent a posterior probability < 0.95. The families of Trachymedusae are highlighted in grey. Note that the P. polaris specimen from Antarctica is lacking a 16S sequence.
Fig 5.
Abundance of the trachymedusa Ptychogastria polaris in Andvord, Flandres and Barilari Bays.
Data are plotted (m-2) as a function of (A) distance to the nearest tidewater glacier, and (B) position in basins down fjord.
Table 4.
Spatial dispersion of Ptychogastria polaris in Andvord and Flandres Bays.
Fig 6.
Percentage frequency distribution of the trachymedusa Ptychogastria polaris in Andvord and Flandres Bays.
Percentage frequency distribution of P. polaris are plotted by fjord and by fjord basins using the mean + standard deviation across phototransects. (A-B) Andvord Bay and (C-D) Flandres Bay. Note that panels A and C are by fjord, and B and D are by fjord basin. Fjord basins are indicated as follows: AMTH = Andvord Bay mouth; AO = Andvord Bay outer; AM = Andvord Bay middle; AI = Andvord Bay inner; FO = Flandres Bay outer; FIA = Flandres Bay inner A; and FIB = Flandres Bay inner B. X-axes are on different scales for Andvord and Flandres Bays. N = number of phototransects and n = number of P. polaris.
Fig 7.
Percentage size frequency distribution of bell diameter for the trachymedusa Ptychogastria polaris in Andvord and Flandres Bays.
Percentage of P. polaris in each size category (mm) are plotted by fjord and by fjord basins using the mean + standard deviation across phototransects. (A-B) Andvord Bay and (C-D) Flandres Bay. Note that panels A and C are by fjord, and B and D are by fjord basin. Fjord basins are indicated as follows: AMTH = Andvord Bay mouth; AO = Andvord Bay outer; AM = Andvord Bay middle; AI = Andvord Bay inner; FO = Flandres Bay outer; FIA = Flandres Bay inner A; and FIB = Flandres Bay inner B. N = number of phototransects and n = number of P. polaris.
Table 5.
Skewness characteristics of Ptychogastria polaris size frequency distributions observed in Andvord and Flandres Bays.