^ o i a r i N* Molluscs in Kongsfjorden (Spitsbergen, Svalbard): a species list and patterns of distribution and diversity Maria Wlodarska-Kowalczuk Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland Keywords Abstract Mollusca; glacial fjord; species list; species distribution; diversity; Svalbard. This paper presents a survey of the mollusc fauna in Kongsfjorden, an Arctic glacial fjord in Spitsbergen, Svalbard, based on 197 samples collected with van Correspondence Veen grabs, dredges, scuba-diving collections and baited traps at depths ranging M. Wfodarska-Kowalczuk, Institute of from 5 to 390 m. Eighty-seven mollusc species were recorded. The species Oceanology, PAS, Powstancow Warszawy distribution accords well with the distribution of the main substrata: barren 55, 81-712 Sopot, Poland. Email: rock, kelp bed, gravel and soft bottom. For the most common substrate type, [email protected] the soft bottom, the distribution and diversity of molluscs were analysed in d o l : 10.1 111/j. 1751-8369.2007.00003. X relation to environmental factors. Glacial activity (particularly the inflow of glacial meltwater loaded with mineral solids) is responsible for the main gradients of environmental variables in the fjord. Silt concentration in sedi­ ments, the water temperature near the bottom and inorganic suspensions in the surface water best predict the species distribution of the soft bottom. Two faunal associations located in glacial bays and three faunal associations in the central basin of the fjord can be distinguished for the fauna of the soft bottom. Molluscs are much more abundant in glacial bays (200-300 individuals (ind.) 0.1m 2) than in the central basin assemblages (30-40 ind./0.1 m2). Yoldiid (Yoldiella solidula, Y. lenticula an d Yoldia hyperborea) and thyasirid bivalves (Thya­ sira dunbari, T. gouldi a n d Axinopsida orbiculata) cope particularly well with glacial sedimentation and occur in high quantities in glacial bays. Although there is no effect of glacial disturbance on the molluscan sample species richness and species diversity, there are significant clines of evenness and taxonomic distinctness in areas near to the glacier. The patterns of molluscan diversity are not fully consistent with the patterns described for complete macrobenthic communities. Kongsfjorden is situated on the west coast of Spitsbergen, and Networking of Large-scale Long-term Marine Biodi­ which is the largest island of the Svalbard archipelago. versity in Europe (BIOMARE) project selected Kongs- Despite its high latitude location (79 °N) the fjord has a fj orden as one of the European Marine Biodiversity sub-Arctic character (Hop et al. 2002). The outer and Research Sites, which provide reference localities for central basins of Kongsfjorden are influenced by the large-scale European biodiversity studies (Warwick et al. warm Atlantic waters of the West Spitsbergen Current 2003). (Svendsen et al. 2002). Three tidal glaciers terminate in The biota inventory in selected sites is a crucial starting the fjord. Kongsbreen, situated in the innermost part of point for large-scale studies of temporal and spatial the fjord, is the most active glacier in the Svalbard archi­ changes of coastal biodiversity (Stork et al. 1996). Species pelago (Lefauconnier et al. 1994). There is an interna­ richness records are largely dependent on the sampling tional research centre in the settlement of Ny-Àlesund, effort (Magurran 2004). The assessment of species rich­ which makes Kongsfjorden one of the most intensively ness of a marine bay, an inlet or an island requires inten­ studied high latitude fjords. The physical and biological sive sampling using a variety of sampling techniques, and settings of the fjord have been reviewed by Svendsen preferably covering several sampling seasons (Bouchet et al. (2002) and Hop et al. (2002). The Implementation et al. 2002). 4 8 Polar Research 26 (2007) 48-63 © 2007 The Author M. Wlodarska-Kowalczuk Molluscs in Kongsfjorden (Spitsbergen, Svalbard) Molluscs are widely distributed and can be abundant in Study area a variety of marine habitats ranging from rocky shores to abyssal muddy plains. Molluscs can be highly responsive Kongsfjorden is an open fjord located on the north-west to local hum an activities (Terlizzi et al. 2005) as well as to coast of Spitsbergen in the Svalbard archipelago (12°E, either long-term or large-scale climatic changes (Miesz- 79 °N; Fig. 1). The fjord is 26 km long, with an area of kowska et al. 2006), and have been proposed as possible 231 km2. Depths rarely exceed 400 m. Two tidal glaciers surrogates for the study of the distribution and diversity (Kongsbreen and Conwaybreen) terminate in the inner of the whole macrobenthic community (Anderson et al. basin, whereas a third one, Blomstrandbreen, is situated 2005; Smith 2005). In Arctic fjords molluscs exhibit the on the northern mid-fjord coast. highest preservation potential among the marine mac­ The hydrology of Kongsfjorden is shaped by the inter­ robenthic biota (Aitken 1990). Between 30 and 60% of play among: ( 1 ) warm saline Atlantic waters entering the the modern Arctic mollusc fauna is represented in Qua­ fjord from the shelf [temperature ( T ) > 1 °C, salinity ternary marine Arctic macrofossils, and understanding (S) > 34.7]; (2) local fjord waters (r<l°C, salinity the environmental factors controlling the distribution of S > 34.4); (3) freshwater input from the glaciers (Svend­ living communities is crucial for reconstructing the palae- sen et al. 2002). In the inner basin there are deep depres­ oecology of Quaternary glaciations and interglaciations sions in which very cold winter waters ( T < - 0.5 °C, (Gordillo 8- Aitken 2000). S > 34.4), which are the remnants of winter cooling and The macrobenthic communities of Kongsfjorden have deep convection, can be also observed (Svendsen et al. been described in several publications. Kendall et al. 2 0 0 2 ). (2003), Wlodarska-Kowalczuk 8 Pearson (2004), Wlo­ Fairly uniform fine sediments cover much of the darska-Kowalczuk et al. (2005) and Somerfleld et al. Kongsfjorden subtidal region, particularly in the inner (2006) studied the distribution and diversity of subtidal basin where high sediment deposition rates are communities of the soft bottom at depths ranging from accompanied by relatively weak currents (Wlodarska- 30 to 300 m. The shallow subtidal macrofauna has been Kowalczuk 8 Pearson 2004). Gravel beds occur in described by Kaczmarek et al. (2005) and Bick 8 Arlt some parts of the outer fjord where strong bottom cur­ (2005). Lippert et al. (2001) studied the phytophylous rents winnow out fine sediments. Ice rafted pebbles and macrofauna at a single location close to the island of stones (drop-stones), typical of Arctic glaciated fjords Blomstrandhalvoya. Jorgensen 8 Gulliksen (2001) (Dale et al. 1989), are distributed all over the fjord. At investigated the fauna of the hard bottom at the Kvade- the edge of the fjord there are rocky shelves (Jorgensen huken at a depth of 20-30 m using a suction sampler 8 Gulliksen 2001) that gradually change into mixed and underwater photography. Rozycki (1991) published bottom (hard bottom with macroalgae and bedrock with a list of molluscs found at 12 stations sampled with pockets of soft sediment) in the shallow subtidal region grabs and dredges. Those studies were limited in scope in the middle of the fjord (Kaczmarek et al. 2005). Kelp to a single location, habitat or depth range within the forests (Alaria esculenta. Laminaria saccharina a n d L. digi­ fjord. tata) are restricted to sites sheltered from drifting ice­ The published information on mollusc diversity and bergs and with limited grazing by sea urchins (Lippert distribution in Kongsfjorden is scattered and incomplete. et al. 2001; Hop et al. 2002). In the present study I bring together extensive distribu­ The meltwater inflows from the Kongsfjorden glaciers tional data of molluscs collected in several benthic sur­ result in a steep gradient in both the concentration of veys carried out in Kongsfjorden by the Institute of mineral suspensions and the sedimentation rates in the Oceanology, Polish Academy of Sciences, in 1996-2000. water column (Svendsen et al. 2002). The sediment accu­ The material contains 197 samples taken with a variety of mulation rate decreases by about one order of magnitude sampling gear at a range of depths and habitats, and is from the Kongsbreen glacial bay (20 000 g n f2 a-1) to the likely to give a reliable assessment of the mollusc diversity central part of the fjord ( 1800-3800 g n r2 a-1) and, again, and distribution patterns in the fjord. The aims of the by another order of magnitude towards the outer fjord paper are to ( 1 ) present a mollusc species list for Kongsf- (200 g n r2 a-1; Svendsen et al. 2002). Intensive sedimen­ jorden; (2) identify the environmental predictors of tation results in the formation of unconsolidated labile the mollusc species distribution; (3) identify the species sediments (Syvitski et al. 1987). Near-glacier sediments characteristic for fjord habitats/mollusc associations; (4) may be scoured by icebergs (of up to 10 m in height) that quantify the response of molluscs at the soft bottom to either circulate or stay anchored in the inner basin glacial disturbance and compare it with the perturbation (Dowdeswell 8 Forsberg 1992). signal in the whole macrobenthic community (as The organic matter supply to benthic biota decreases described by Wlodarska-Kowalczuk et al. 2005). towards the inner basin, where primary productivity is Polar Research 26 (2007) 48-63 © 2007 The Author 4 9 Molluscs in Kongsfjorden (Spitsbergen, Svalbard) M. Wlodarska-Kowalczuk Greenland Svalbard Kongsfjorden Norwaj • van Veen grabs (38-380 m) H epibenthic sledges (30-390 m) Ö scuba diving (10 m) HH transects - shallow water dredging (5-50 m) D baited traps (5-60 m) glacier front Figure 1 Location o f sam pling stations.