Shallow-Water Bryozoan Communities in a Glacier Fjord of West Svalbard, Norway: Species Composition and Effects of Environmental Factors

SIMPLE SUMMARY: Bryozoans are predominantly short-lived sessile organisms inhabiting both living and dead hard substrates. This group is considered a good biological indicator of environmental conditions. The Svalbard Archipelago is located at high latitudes, and the local benthic communities are affected by severe environmental conditions. In general, the bryozoan fauna in this region has been well studied, albeit to varying spatial degrees. Information regarding Grønfjorden is scarce and, therefore, we aimed to study species composition, diversity, and biomass of bryozoans in this glacier fjord. We found a rather diverse fauna with low biomasses for all species. Cluster analysis distinguished two groups of stations: one with lower diversity and biomass in warmer water, and the other with higher values in colder water. The most important factors shaping the bryozoan communities were water temperature and the proportional occurrence of macrophytes. Taking into account ongoing climate change, our results may be useful for further monitoring the effects of elevated temperatures on benthic organisms in the Arctic. ABSTRACT: Despite significant research efforts focused on benthic assemblages in West Spitsbergen, there is a lack of knowledge regarding the shallow water bryozoan communities in Grønfjorden, a glacier fjord belonging to the Isfjorden system, Norway. Here, we studied species composition, richness, distribution, and biomass of bryozoans in the intertidal and upper subtidal zones of Grønfjorden in summer. We found 62 bryozoan species, among which Celleporella hyalina (Linnaeus, 1767), Harmeria scutulata (Busk, 1855), and Tegella arctica (d’Orbigny, 1853) were most prevalent while the highest contributions to the total biomass were registered for Eucratea loricata (d’Orbigny, 1853), Tricellaria gracilis (Van Beneden, 1848), Turbicellepora incrassata (Lamarck, 1816), and Tricellaria ternata (Ellis and Solander, 1786). Alpha-diversity varied from 1 to 50 averaging 15.1 ± 2.6 species. Bryozoan biomass ranged from 0.008 to 10.758 g m(−2) with a mean value of 2.67 g m(−2) being lower than in the central and northern parts of the Barents Sea. For the first time, we registered the presence of the circumpolar bryozoan Amathia arctica in Svalbard waters probably as a result of stronger advection of Atlantic water into the fjord. Cluster analysis revealed two groups, mainly composed of stations in colder and warmer waters. A relatively high proportion of outlying stations reflected habitat heterogeneity in Grønfjorden. Redundancy analysis indicated that bryozoan diversity and biomass were strongly negatively associated with temperature. A positive relationship was found between bryozoan biomass and the proportional contribution of macrophytes to a pool of substrates. Our study provides a reference point for further monitoring of changing marine ecosystems at high latitudes.