Piotr Balazy

Unexpected Levels of Biological Activity during the Polar Night Offer New Perspectives on a Warming Arctic

The current understanding of Arctic ecosystems is deeply rooted in the classical view of a bottom-up controlled system with strong physical forcing and seasonality in primary-production regimes. Consequently, the Arctic polar night is commonly disregarded as a time of year when biological activities are reduced to a minimum due to a reduced food supply. Here, based upon a multidisciplinary ecosystem-scale study from the polar night at 79°N, we present an entirely different view. Instead of an ecosystem that has entered a resting state, we document a system with high activity levels and biological interactions across most trophic levels. In some habitats, biological diversity and presence of juvenile stages were elevated in winter months compared to the more productive and sunlit periods. Ultimately, our results suggest a different perspective regarding ecosystem function that will be of importance for future environmental management and decision making, especially at a time when Arctic regions are experiencing accelerated environmental change [1].

Evidence of season-dependency in vegetation effects on macrofauna in temperate seagrass meadows (Baltic Sea).

Seagrasses and associated macrophytes are important components of coastal systems as ecosystem engineers, habitat formers, and providers of food and shelter for other organisms. The positive impacts of seagrass vegetation on zoobenthic abundance and diversity (as compared to bare sands) are well documented, but only in surveys performed in summer, which is the season of maximum canopy development. Here we present the results of the first study of the relationship between the seasonal variability of seagrass vegetation and persistence and magnitude of contrasts in faunal communities between vegetated and bare sediments. The composition, abundance, biomass, and diversity of macrozoobenthos in both habitats were compared five times throughout the year in temperate eelgrass meadows in the southern Baltic Sea. Significant positive effects of macrophyte cover on invertebrate density and biomass were recorded only in June, July, and October when the seagrass canopy was relatively well developed. The effects of vegetation cover on faunal species richness, diversity, and composition persisted throughout the year, but the magnitude of these effects varied seasonally and followed changes in macrophyte biomass. The strongest effects were observed in July and coincided with maximums in seagrass biomass and the diversity and biomass of other macrophytes. These observations indicate that in temperate, clearly seasonal systems the assessment of macrophyte impact cannot be based solely on observations performed in just one season, especially when that season is the one in which macrophyte growth is at its maximum. The widely held belief that macrophyte cover strongly influences benthic fauna in marine coastal habitats, which is based on summer surveys, should be revisited and complemented with information obtained in other seasons.

Hermit crabs (Pagurus spp.) at their northernmost range: distribution, abundance and shell use in the European Arctic

Hermit crabs are important components of Arctic benthic systems, yet baseline data on their densities and distribution patterns in this rapidly changing region are still scarce. Here we compile results of numerous research expeditions to Svalbard, the Barents Sea and northern Norway that were carried out from 1979 to 2011 by the Institute of Oceanology, Polish Academy of Sciences. The diversity of hermit crabs at the northern edge of their occurrence is very low; in Svalbard waters only one species (Pagurus pubescens) was detected. Another species (P. bernhardus), found in northern mainland Norway, north of the Arctic Circle, is likely to extend its distribution northward as the climate warms. Where the two species co-occur, competition between them probably accounts for the smaller sizes and poorer quality shells used by P. pubescens. The composition of the mollusc shells inhabited by these crabs differs between northern Norway and Svalbard, reflecting local mollusc species pools. Hermit crab densities were significantly higher than previously reported (max. mean 10 ind. m−2), suggesting their increasing level of dominance in benthic communities in the studied areas. The first to report the distribution of hermit crabs among habitats, this study showed that most individuals occurred at shallow depths (5–150 m), away from glacier termini and on hard bedrock rather than on soft substrata.

Growth Rate of Selected Sheet-Encrusting Bryozoan Colonies Along a Latitudinal Transect: Preliminary Results

Climate change driven alterations of sea-water temperature, salinity, acidity and primary production in many coastal regions will probably affect the ecophysiological performance of sedentary organisms. Despite bryozoan ubiquitous and often dominant occurrence in coastal zones there are few studies on their growth dynamics. Here we report growth rates of selected sheet-encrusting bryozoans from four contrasting (in mean annual water temperature) environments: Adriatic Sea (44° N), Baltic Sea (54° N), northern Norway (68° N), and Spitsbergen (78° N). Perspex panels were photographed underwater and colonies’ growth rates analyzed backwards using digital images. We found a negative trend between growth rate and latitude. Congeneric bryozoan species from lower latitudes grew faster: the average growth rate of the cyclostome genus Diplosolen from the Adriatic Sea was 75 mm2 after 5 months (~180 mm2/year) while Diplosolen arctica from Spitsbergen grew only 4 mm2/year. Similarly the average surface area of Microporella arctica individuals after 12 months in northern Norway was 12 mm2 compared to 2 mm2 in Spitsbergen. An exception from this general pattern was Einhornia crustulenta in the brackish environment of the Baltic Sea, which grew relatively rapid for this latitude and water temperature (surface area of up to 657 mm2/month after settlement).

Hyas spp. crabs and sea anemones—new species associations from Svalbard

In the literature, there is a large amount of evidence on mutual and commensal associations between actiniarians and decapods (see Ross 1983 and references therein). Among all these studies, only Davenport (1962) and Schrieken (1965) dealt with Hyas spp. Their work, however, was performed in aquaria and concerned only young crab individuals (Davenport 1962) and a single sea anemone species—Tealia felina (Linnaeus, 1767) (= Urticina felina) (Davenport 1962; Schrieken 1965). Here, we describe the association of mature H. araneus (Linnaeus, 1758) and H. coarctatus Leach, 1816 with Cribrinopsis similis Carlgren, 1921, Hormathia nodosa (Fabricius, 1780) and Urticina crassicornis (O.F. Mueller, 1776), which to our knowledge are reported for the first time. The associations were recorded during the summers of 2011 and 2012 on the rocky bottom of an Arctic fjord—Isfjord (Spitsbergen Island, Svalbard Archipelago) at 10–15 m depth. Direct underwater observations (Fig. 1a–h) indicate that the crabs were in contact with sea anemones for several minutes. When approached by a diver, the crabs did not escape from the anemone but got closer to it. On one specific occasion, removing the rock, marked in Fig. 1g with an arrow, revealed a large (∼5 cm diameter of the pedal disc) specimen ofC. similis attached to the crab by its verrucae (Fig. 1h). Although sufficiently large sea anemones such as Urticina sp. have occasionally been noted in the past to feed on these crabs in this area (Gulliksen and Svensen 2004), it seems instead that the crabs, while avoiding contact with the tentacles, are searching for protection from predators (e.g. bottom-dwelling fish, octopus) as previously reported for other decapods, including those closely related toHyas spp. (Ross 1983). More studies are needed to verify and confirm whether these associations have just a short-term facultative commensalistic character.

Factors affecting biodiversity on hermit crab shells

This study explores the abundance, diversity and assemblage structure of epifauna on the shells used by two hermit crab species (Pagurus bernhardus and P. pubescens) in the Arctic (Svalbard and Northern Norway) and investigates the biotic and physical drivers of such patterns. Contrary to our expectations, we found that location (which reflects the variability in environmental conditions and the local species pool of potential colonizers) is a key determinant not only in the cold, ice-scoured, glacier-dominated Arctic shallows of Svalbard but also in boreal Norwegian fjords, where other factors were hypothesized to be more important. Depending on region, shell area and identity were of lesser magnitude, with larger and more irregular shells containing more diverse assemblages. Crab host species also played a role (P.pubescens-inhabited shells supported larger number of individuals and higher diversity than those of P. bernhardus) but this effect might be species or region specific. In this study, no effect of crab gender could be detected. The study indicated that epifaunal assemblages of hermit crab shells are influenced by complex set of factors that interact together to different degree at various locations.

Recruitment pattern of benthic fauna on artificial substrates in brackish low-diversity system (the Baltic Sea)

Recruitment pattern of benthic fauna in temperate marine ecosystems is still not well recognized, particularly in inland coastal seas with distinct environmental and ecological conditions. This study investigates the effect of natural surrounding community structure, environmental variables and substrate orientation on short-term recruitment of motile and sessile epibenthos in the southern Baltic Sea. Recruitment on topsurface and undersurface of Perspex panels deployed on the seafloor in a horizontal position was monitored monthly from March 2008 to March 2010 in two coastal habitats (sandy and gravelly) in the Gulf of Gdańsk. Recruitment of epibenthic invertebrates took place primarily over a growing season (March–October) indicating that reproduction and settlement are driven by water temperature and gross primary production. Communities of recruits showed relatively homogenous spatial taxonomic composition but total epifaunal abundance varied between bottom types. Planktonic larvae supply and species-specific recruitment behaviour account primarily for settlement success, particularly on panel topsurface which hosted more diverse and more abundant recruits than panel undersurface. Relative to vertical substrates, horizontal panels had less numerous barnacle recruits probably due to inhibitory effect of sediment deposition and organic biofilm.

Diver deployed autonomous time-lapse camera systems for ecological studies

ABSTRACT Photographic time-lapse techniques are especially useful in the marine realm for visualising long-term processes and remote monitoring of sites/objects/organisms where the presence of researchers might cause some study bias, or access is limited or impossible. With rapid advances in technology development there is easy access to new tools for time-lapse photography and setting up systems is relatively inexpensive. The essential requirements for low-cost autonomous time-lapse camera systems to be self-sufficient and reliable enough to withstand the extended periods of deployment (up to one year) on the sea floor at up to 50 m depth are presented. In this example a custom-made system developed originally for monitoring the activity of filter/suspension feeders and scavenging fauna in the polar conditions is described. The major issues encountered during the preparation and deployment which should be of benefit to users involved in underwater time-lapse photography are considered.

Direct evidence of sea anemone predation on Arctic echinoids

Predator–prey interactions are considered a major evolutionary driver and a key biological factor affecting recent organisms, but little is known about their influence on Arctic benthic life. It is not easy to document predatorial behaviour in situ in the marine realm, especially in polar seas, and thus usually only indirect evidence is available. Palaeoecologists use several proxies to infer predation on echinoids (Wilson et al. 2015), namely drill holes, repair scars, ejecta deposits