Botanica Marina 2018; 61(4): 421–428 Short communication Anna M. Kubiszyn* and Camilla Svensen First record of a rare species, Polyasterias problematica (Prasinophyceae), in Balsfjord, northern Norway https://doi.org/10.1515/bot-2017-0123 identified a single specimen of the extremely rare and Received 12 December, 2017; accepted 25 May, 2018; online first poorly known prasinophyte Polyasterias problematica 13 June, 2018 (Cleve) Meunier (Figure 2). This organism was collected in a short-term sediment trap deployed from 19 to 20 June Abstract: Polyasterias problematica is a poorly investi- 2017 in a thermally stratified water column with a tem- gated prasinophyte species, practically known only from a perature of 11°C at the surface and a gradual decrease to few, primarily historical studies. Fragmentary information approximately 7°C, 6°C and 5°C at depths of 15 m, 30 m on the species indicates that P. problematica is mainly dis- and 50 m, respectively. The sediment trap (KC Denmark) tributed in the euphotic zone of the Canadian and Russian consisted of two transparent polyvinyl chloride (PVC) Arctic, Atlantic Canada, the mid-Atlantic and some Euro- cylinders (opening diameter 72 mm, cylinder height pean seas. Here, we present the first record of this species 450 mm) mounted on a steel frame equipped with a steer- in the Balsfjord waters, northern Norway. A detailed mor- ing fin. Five pairs of sediment traps were mounted on a phological description, with line drawings and micros- mooring to collect material at depths of 20, 30, 50, 90 and copy-based photographs, as well as information on its 120 m. The sediment trap mooring was anchored to the up-to-date geographical distribution and possible expla- seafloor to avoid drifting. The specimen of P. problemat- nations for its extraordinary scarcity are provided. ica was found in the sediment trap deployed at the 30-m Keywords: Balsfjord; northern Norway; planktonic pro- depth, a sufficient distance from the seafloor at 170 m tists; Polyasterias problematica; Prasinophyceae. to avoid resuspension of sediment material. After a 24-h deployment, the sediment trap mooring was retrieved and the contents of the two cylinders from each depth Balsfjord, a 45 km long and 2–3 km wide fjord with a were gently pooled together. From this material, a 100-ml south-south-east orientation (69°N, 19°E; Figure 1), is an subsample was taken for phytoplankton identification. example of a well-monitored environment in northern Samples for cell identification and enumeration were Norway, with a long history of planktonic protist studies fixed with glutaraldehyde-Lugol’s solution (GA-Lugol; (e.g. Gaarder 1938, Eilertsen et al. 1981, Bech 1982, Eiler- 2% final concentration, Rousseau et al. 1990). Sub- tsen and Taasen 1984, Lutter et al. 1989, Sandberg 1996, samples were qualitatively and quantitatively analysed Degerlund and Eilertsen 2010). Previous investigations under an inverted microscope (Nikon Eclipse TE-300) have provided knowledge on the qualitative and quanti- equipped with phase and interference contrast optics, tative protist community structure of the area, which is an ocular magnification of 10× and objective magnifica- represented by taxa belonging to the Arctic and boreal tion of 10× (Nikon Plan Fluor, 0.30 NA) and 40× (Nikon regions (Throndsen et al. 2007). Plan Fluor, 0.60 NA), using protocols by Utermöhl (1958) Through recent plankton studies at the Svartnes and modified by Edler (1979), as described in Kubiszyn station (69°22′N, 19°07′E) in Balsfjord, we found and et al. (2014). The taxonomic identification of this species was made *Corresponding author: Anna M. Kubiszyn, Department of Marine on the basis of schematic line drawings and morphologi- Ecology, Institute of Oceanology Polish Academy of Sciences, cal descriptions given in Cleve (1900a,b) and Meunier Centre for Polar Studies KNOW (Leading National Research Centre), (1910, 1919), as well as a single light microscopy-based Powstańców Warszawy 55, 81-712 Sopot, Poland, photograph of the dorsal view, presented by Brunel e-mail: [email protected] (1962) and Bérard-Therriault et al. (1999). In addition to Camilla Svensen: Department of Arctic and Marine Biology, Faculty for Biosciences, Fisheries and Economics, UiT the Arctic University these works, we did not find any other study describing of Tromsø, N-9037 Tromsø, Norway or illustrating the morphological characteristics of this Brought to you by | Universitetsbiblioteket i Tromsoe Authenticated Download Date | 11/2/18 3:29 PM 422 A.M. Kubiszyn and C. Svensen: Polyasterias problematica in Balsfjord Figure 1: Location of Balsfjord, northern Norway, with the Svartnes sampling station in the Svartnes Basin. species. The hitherto pelagic records of P. problematica, marine environment with proximity to river inlets and/ largely referring to papers at least 50 years old, indicate or meltwater plumes (Kunz-Pirrung 1998, Sorrel et al. the Arctic-boreal distribution of the species (Figure 3, 2006, Price and Pospelova 2011, Milzer et al. 2013). Unfor- Table 1). According to these papers, P. problematica is tunately, because many of the cited studies, conducted mainly distributed in the euphotic zone of the Canadian in a relatively large area (inter alia, throughout a bay or and Russian Arctic, Atlantic Canada, the mid-Atlantic along multi-kilometre transect), do not provide the exact and some European seas (Figure 3, Table 1). Based on the position of the P. problematica record (e.g. Meunier 1910, large range of the species occurrence, it appears to prefer Bursa 1961, Horner 1984), the location of points in Figure brackish or euryhaline waters. The literature documented 3 is largely indicative. Most studies are limited to qualita- a biogeographical distribution that generally corresponds tive species information, in some cases supplemented by to the raw plankton data integrated in the Ocean Biogeo- comments on the rareness of the cells. Scarcely occurring graphic Information System [OBIS: http://www.iobis. data on abundance range from 1 to 750 cells l−1 (Anderson org; 249 records from 1903 to 2012, of which almost half 1979, Pederson 2004, Martin et al. 2006). Here, we present are up to 1911; 70% of the later data was obtained in the the first record of P. problematica in the northern Norway continuous plankton recorder (CPR) survey; Figure 3]. area. We also provide a detailed description of the mor- Although, OBIS is considered to be the most complete phological characteristics and possible explanations for and comprehensive data repository in existence on the its extraordinary scarcity. distribution of marine taxa, due to the known issues with The basionym of Polyasterias problematica [synonym: regards to taxonomic completeness, geographical biases, Ovum hispidum problematicum (Cleve) Lohmann] is Hexas- and biogeographical accuracy (Webb et al. 2010), the terias problematica, described by Cleve (1900a). This cell given number and positions of records should, however, was first observed by Hensen (1887; presented as “Röhren- be regarded as uncertain and treated with caution. As a statoblast”) in the western Baltic Sea. Cleve (1900a) estab- palynomorph, P. problematica has been observed on the lished the genus Hexasterias (Chlorophyta) on the basis of continental shelves of the Canadian and Russian Arctic, observations of individuals with six rays, which he con- the North Atlantic, the north-eastern Pacific, and in a sidered as conservative. Later studies have shown that the series of marine basins extending from the Mediterranean number of rays may vary from four to eight (this difference to the Aral seas (Figure 3, Table 1), where it is generally still remains unclear) and the 6-arm forms were the least linked to low saline/brackish cold surface waters in a common (Meunier 1910). Since Meunier (1910) considered Brought to you by | Universitetsbiblioteket i Tromsoe Authenticated Download Date | 11/2/18 3:29 PM A.M. Kubiszyn and C. Svensen: Polyasterias problematica in Balsfjord 423 A B CD Figure 2: Micrographs (A, B) and line drawings (C, D) of Polyasterias problematica taken in light microscopy at 400×. (A) Stack image of a cell with seven arms in dorsal view. (B) Side view of a cell showing the hook-like structures of the arms. (C) Schematic dorsal view of a cell. (D) Schematic side view of a cell. that introducing the term Hexasterias octoradiata, as an specimen (e.g. Horner 1984, Heiskanen et al. 2005). Addi- example for an 8-arm form, would be too paradoxical, tional taxonomic confusion, causing difficulty in merging he decided to replace the genus name with Polyasterias, species data, results from the use of more than one species which did not clearly indicate the number of processes. name in the literature. Generally, in planktonic works, it Interestingly, he negated the taxonomic affiliation of the appears as P. problematica, while in sediment studies, it species proposed by Cleve, claiming that the cell does not is included as H. problematica. In pelagic investigations, have the characteristics of a plant and it is probably an egg the exceptions are Häyrén (1931), Horner (1984) and Heis- or a cyst of an unknown animal, with which it will soon kanen et al. (2005) (H. problematica), as well as Bērziņš be bound. Additionally, Lemmermann (1908) expressed (1932) (Ovum hispidum problematicum), whereas in sedi- doubts about the taxonomic classification of Hexasterias, ment approaches, the exceptions are Rubino et al. (2009) but these considerations mainly concerned its affiliation and Van Hauwaert (2016) (P. problematica). with the Pleurococcaceae. Until recently, many authors did Despite the different views on species taxonomic not trust the validity of its affiliation in the Prasinophyceae affiliation, both Cleve (1900a,b) and Meunier (1910, 1919) and preferred to present it as an “other” or “unknown” presented very similar species descriptions, to which the Brought to you by | Universitetsbiblioteket i Tromsoe Authenticated Download Date | 11/2/18 3:29 PM 424 A.M.