Seasonal data on Rose Bengal stained foraminifera in the head of Kongsfjorden, Svalbard

Current ‘Atlantification’ of the Arctic Ocean affects benthic communities leading to the changes in their structure and abundance. Such areas as Svalbard that are seasonally affected by Atlantic and Arctic water masses may give a possibility to preliminary estimate the response of benthic communities to short-term environmental changes and to evaluate their sensitivity. We have sampled Kongsfjorden for modern benthic foraminifera in three different seasons. The record includes data on the abundances of benthic foraminiferal species in the surface sediments (0–2cm). This data gives an insight into the seasonal dynamics of the near-glacial foraminiferal community of Kongsfjorden.


Data
Glaciated subpolar fjords are widely represented in the Northern Hemisphere. These are dynamic systems that are characterized by specific circulation [1] and are influenced by glacial meltwater runoff that brings vast amount of rapidly accumulating mineral matter [2,3]. Both these factors influence fjord benthic communities.
Kongsfjorden is a glacially fed fjord located in the western part of West Spitsbergen (Fig. 1). The fjord is influenced by both Atlantic and Arctic water masses that mix and interchange throughout the year [4,5]. Benthic foraminiferal community of Kongsfjorden has been investigated by a number of authors. However, in most of the previous studies sampling was carried out in late spring e early autumn and did not include winter months [6,7]. Still little is known of the changes it undergoes interannually.
Here we present a two-year dataset that covers three subsequent seasons: winter 2015, autumn 2015 and spring 2016 ( Table 1). The data are living foraminiferal abundances normalized to 10cm 3 of sea-floor surface sediment (Tables 2e4).

Experimental design, materials and methods
We sampled sea bottom sediments in the head of Kongsfjorden during three cruises with RV Helmer Hanssen (Fig. 1). Sampling with a 50 Â 50cm box corer was carried out in January and September 2015 and June 2016 (Table 1). Three replicates of 0e2cm surface sediment of arbitrary volume (approx. 80e120ml) were taken from each box corer with the exception of station 7 where only two replicates were taken due to the partly disturbed sediment. Sediment was collected into cylindrical jars and the volume of each sample was calculated as a volume of cylinder (V ¼ p*r 2 *h, where r -is the radius of the jar, h e is the height of the sediment in a jar). To distinguish living foraminifera we preserved samples with 96% alcohol solution of Rose Bengal dye. The staining period was 14 days minimum to provide the time for thorough staining of all living foraminifera. In the laboratory we washed the sediment on a sieve with 63um mesh size, kept it in 30% alcohol overnight to remove excess dye and dried it at 100 C. We split samples to obtain practical aliquots containing 100 to 300 stained specimens. To split samples, we did not use a dry micro-splitter. Instead, we applied a splitting procedure which provides, in our experience, more reproducible results. We placed the dry residue on a glass plate and divided the heap with two cross cuts by a razor blade into four parts. The mixing of the opposite quarters gave us two identical halves. When necessary, the procedure was repeated to obtain 1/4, 1/8, or 1/16. Then an aliquot was processed as a whole. All 100 to 300 stained specimens were identified to the lowest possible taxonomical level and counted. The number of specimens in the sample was calculated as N*2 s Specifications table

Subject area
Earth and Planetary Sciences More specific subject area Benthic Foraminifera Type of data Tables, figure How data was acquired Samples were collected during three expeditions to Kongsfjorden from 2015 to 2016 (in January, September and June), using box corer, stained with Rose Bengal; live and benthic foraminifera were identified to the species level and counted.

Data format
Tables with densities of live foraminifera; a table with station list, coordinates, water depth.

Experimental factors
Sampling was carried out in January 2015, September 2015 and June 2016 to cover different seasons and get a grasp on seasonal changes in the foraminiferal community Experimental features The surface sediment was collected with a box corer. Samples were stained with Bengal Rose and washed on a 63um sieve.

Data source location
Kongsfjorden, Svalbard archipelago (GPS coordinates are provided in the table)

Value of the data
The data traces the seasonal dynamics of living benthic foraminiferal assemblages based on the Rose Bengal staining. The data keeps record of foraminiferal response to the changing throughout the year water masses.
The data provides an insight into the structure of near-glacial foraminiferal community.
(where N was the number of stained specimens counted in the split and S was the number of splits). Foraminiferal abundance was normalized to 10cm 3 of wet sediment using the measured volume of the sediment in the sample bottle. Taxonomical guides were H€ oglund [8], Loeblich and Tappan [9], and Knudsen [10]. The data set comprises information organized in three sets of data: 1. Station list is including coordinates, months sampling, water depths (Table 1)