ID:27 Shifting trophic networks along the Arctic land-coast-ocean continuum

22 February 2023 | 10:30 - 12:30 (GMT+1)

Open Session - HYBRID

 

Room: Hörsaal 3

 

Session Conveners: Marja Koski (Technical University of Denmark, National Institute for Aquatic Resources, Denmark); Kai Bischof (University of Bremen, Germany); Bruce Forbes (University of Lapland, Finland)

 

Session Description: 

Rain-on-snow-events, thawing permafrost soil, retreating glacier fronts and decreasing sea ice are manifests of cryosphere reduction, which will significantly alter Arctic ecosystem functions and related services. Complex trophic interactions from primary producers to apex predators and, ultimately, food provision to humans, have established in Arctic social-ecological systems and may experience considerable re-structuring due to shifts in biodiversity and productivity. Trophic networks and their interaction with environmental factors connect terrestrial, coastal and ocean systems, allowing for a bidirectional exchange of nutrients and energy. The EU H2020 Projects CHARTER, ECOTIP and FACE-IT invite all types of contributions from the natural and social sciences dealing with marine or terrestrial biodiversity changes that have implications to trophic networks and their related social-ecological systems. Understanding shifts in exchange processes along the land-coast-ocean continuum and their overall implications to ecosystems and human livelihoods, including farming, hunting, fisheries and tourism are of particular relevance to conservation and management needs for Arctic resources.

 

Presentations: 

• unfold_moreIdentifying drivers of phytoplankton diversity and communities in Arctic fjords – From time series modelling to experiments

  Tobias Vonnahme¹; Thomas Juul-Pedersen¹; Diana Krawczyk¹; Anna Vader²; Cheshtaa Chitkara^{2
  1}Greenland Institute of Natural Resources; ²UNIS - University Centre in Svalbard

  Abstract:

  In Arctic fjords, the base of the food web is typically comprised of lipid-rich chain-forming diatoms. However, the community can be dominated by a variety of different diatoms or other phytoplankton taxa such as the colony-forming flagellate Phaeocystis. Different algae species may not be equally suitable or nutritious as food source for higher trophic levels. Increased Atlantic water inflow, with warmer temperatures, altered salinity, and changes in sea ice cover will likely change the diversity of the dominant primary producers. We studied the role of different drivers in an Arctic fjord system on Svalbard (Isfjorden), and a sub-Arctic fjord system in Greenland (Nuup Kangerlua) using two different approaches. Firstly, we analyzed time series in Nuup Kangerlua and Isfjorden using multivariate autoregressive state space models (MARSS) to identify potential environmental drivers of different key phytoplankton groups. Despite nitrate being typically the key limiting nutrient for primary production, our model in Greenland found the nutrients phosphate and silicate to determine the dominance of diatoms or flagellates. Based on the MARSS output, we incubated natural phytoplankton communities from Nuup Kangerlua and Isfjorden under different nutrient conditions. The experiment confirmed the regulatory role of phosphate and silicate. Thus, future projections of phytoplankton community changes need to consider the full spectrum of nutrients.

• unfold_moreRising temperatures and a deteriorating light climate are limiting the expansion of temperate kelp species in the Arctic

  Sarina Niedzwiedz¹; Kai Bischof^{1
  1}Universität Bremen

  Abstract:

  Kelps act as foundation species on many polar rocky shore coastlines. The main drivers for their latitudinal and vertical distribution are temperature and the underwater light climate. With temperatures rising globally, an Arctic kelp expansion and accelerated glacial melt are predicted. It was our aim to investigate the effects of retreating glacier and rising temperatures on the potential kelp habitat in the Arctic. We analysed the underwater light climate in three areas of different glacial influence in Arctic Kongsfjorden, Svalbard and studied temperature-induced changes in the light-use characteristics of two kelp species (Alaria esculenta, Saccharina latissima) at 3, 7, and 11°C. With increasing glacial influence, we not only observed reduced light intensities but also a reduction of the light quality for photosynthesis due to changed light absorption properties of the water column. Rising temperatures lead to a significantly higher compensation irradiance of A. esculenta and an increased dark respiration rate of S. latissima, which correlated with a decreasing carbon content. The chlorophyll a concentration of A. esculenta was ~78% higher than in S. latissima. We conclude that the predicted latitudinal biomass increase of kelps in the future Arctic might be impaired by the shoaling of the lower distribution depth. As kelps provide a range of ecosystem services of vast socio-economic importance, this many have cascading effects on fisheries, tourism and coastline protection.

• unfold_moreGrazing by sea urchins in the arctic Porsanger fjord

  Marie Koch¹; Simon Jungblut²; Reinhard Saborowski^{1
  1}Alfred-Wegener-Institute; ²University of Bremen

  Abstract:

  Extreme grazing events by sea urchins occurred in the 1970s at several sites along the Norwegian coast, leaving an area of 2000 km2 of formerly dense kelp forest completely barren. Slowly these areas have recovered along with a decline of the sea urchin population. The sea urchins Strongylocentrotus droebachiensis (Müller, 1977) and S. pallidus (Sars, 1872) are the main grazers in the Porsanger fjord, North Norway. Kelp forests show sea urchin abundances of 20 ± 10 Ind∙m-2 and neighboring sea urchin barren 147 ± 54 Ind∙m-2. A feeding experiment showed highest grazing rates of both species at 14 °C (S. droebachiensis: 37 mg∙g-1∙d-1; S. pallidus: 46 mg∙g-1∙day-1). The theoretical algae wet mass that would be grazed per day by both species accounts for 28 g·m-2 (kelp) and 48 g·m-2 (barren). Although it is not completely clear what algae source is used by sea urchins from the barren, individuals from the kelp forest as well as from the barren had full guts, containing mainly pieces of brown algae. S. droebachiensis and S. pallidus are able to graze high amounts of algae and grazing pressure on the kelp community depends on temperature. With the ongoing reduction of sea ice and therefore prolonged periods of elevated sea surface temperatures (14 °C), grazing pressure on kelp will increase. Alongside with a decline of kelp, ecosystem functions, like carbon fixation and nursery for commercially important fish and crab species, are likely to be reduced or even lost.

• unfold_moreDisease in the midst of rapid climate change: Long term trends in pathogen seroprevalence in polar bears (Ursus maritimus) in the western Canadian Arctic

  Kayla Buhler¹; Emily Jenkins¹; Nicholas PIilfold²; Evan Richardson³; John Ellis¹; Brad Scandrett⁴; Adrian Hernandez-Ortiz¹; David McGeachy³; Kelly Konecsni⁴; Vladislav Lobanov⁴; Batol Al-Adhami⁴; Megan Owen²; Bruce Rideout²; Nicholas Lunn^{3
  1}University of Saskatchewan; ²San Diego Zoo Global; ³Environment and Climate Change Canada; ⁴Canadian Food Inspection Agency

  Abstract:

  The Canadian Arctic is warming at three times the global rate, altering the transmission, survival and impact of climate-sensitive pathogens. As polar bears are iconic indicators for rapid effects of climate change, we examined 425 serum samples from 381 adult polar bears, collected in the western Hudson Bay, Canada, for antibodies to selected pathogens across three time periods: 1986-1989 (n=157), 1995-1998 (n=159), and 2015-2017 (n=109). We ran serological assays for antibodies to several pathogens: Toxoplasma gondii, Neospora caninum, Trichinella spp., Francisella tularensis, California serogroup viruses (CSV), Bordetella bronchiseptica, canine morbillivirus (CDV), and canine parvovirus (CPV). Seroprevalence of zoonotic parasites and bacteria (T. gondii, Trichinella, F. tularensis, and B. bronchiseptica) was high (>50%) and generally increased over the three periods. Toxoplasma gondii seroprevalence was higher following wetter summers, supporting increased oocyst transmission either directly to bears or their prey. Seroprevalence of Trichinella was higher in polar bears previously captured in human settlements (especially adult males), and in years with warmer summer and winter temperatures, which may be due to increased consumption of terrestrial carnivores and other bears, and/or increased access to muscle larvae in carcasses. Seroprevalence for antibodies to F. tularensis increased following years that polar bears spent more time on land and seroprevalence of antibodies to CSV increased with warmer summer temperatures, suggesting that transmission may increase as the climate warms and polar bears encounter rodents and insects more frequently on land.

• unfold_moreDrivers of vertebrate trophic networks in terrestrial Arctic ecosystems under global change

  James Speed
  Norwegian University of Science and Technology

  Abstract:

  Global environmental change can impact on terrestrial ecosystems through bottom-up processes such as warming climate and changing productivity, and through top-down processes caused by changing biodiversity and shifting species ranges. These co-occurring changes may have different impacts on trophic networks in terrestrial ecosystems in the Arctic. Here drivers of the structure of vertebrate herbivore and carnivore guilds, along with trophic networks, are investigated across the Arctic tundra biome. We used biogeographic and remotely sensed data to quantify spatial variation in vertebrate herbivore and carnivore communities across the Arctic tundra biome. We then tested whether trophic structures are determined primarily by top-down or bottom-up drivers. The inference of findings are discussed in relation to ongoing environmental changes in the Arctic, including Arctic greening and shrubification.

• unfold_moreMeasuring Traditional Indigenous Practices of Monitoring Wind on St. Lawrence Island, AK

  Jon Rosales
  St. Lawrence University

  Abstract:

  This project mimics traditional indigenous methods of monitoring their environment in Savoonga, AK. Via these methods, the current project investigates one of the most disruptive elements of climatic change in the Arctic for indigenous hunters, gatherers, and herders – change to wind patterns and their ability to predict the weather on the land-coast-ocean continuum for hunting success and safety. Of key importance to the subsistence practitioners in this area is the ability to predict weather conditions through direct observation, as opposed to instrumental data from weather stations, before deciding to venture out on the landscape or to decide when to head back home. When deciding on when and where to hunt they observe wind patterns, among other elements. Monitoring wind direction, speed, and variability patterns is an important skill developed by coastal subsistence practitioners in the Arctic to assess potential weather-related risks. This project measures wind direction the way indigenous knowledge holders in Savoonga observe wind direction – by grass lay direction, wind in the tufts of grass, and grass morphology. Preliminary results from focus group meetings with elders, hunters, herders, and gatherers, and grass plot measurements will be presented. This investigation represents the latest investigation of the Alaskans Sharing Indigenous Knowledge (AKSIK) project. Since 2009, AKSIK projects seek to measure climatic change by mimicking traditional ecological knowledge methods of observing their landscapes in Shaktoolik on the mainland of Alaska and Savoonga on St. Lawrence Island.

• unfold_moreCurrent environmental and landscape transformation of Sørkapp Land (Spitsbergen) – the most advanced in the European High Arctic?

  Wieslaw Ziaja
  Jagiellonian University in Cracow

  Abstract:

  Sørkapp Land – the southern Spitsbergen peninsula – is a land wedge between the Greenland and Barents seas, separated from its mainland by two fjords: Hornsund and Hambergbukta. At the end of the Little Ice Age, in 1899–1900, the peninsula was mostly (in 77%) glaciated and isolated (due to a long sea-ice season). Then, its environment and landscape have been transformed a lot due to climate warming, especially big since the end of the 20th c. (according to data from Polish Polar Station nearby). In 2004–2005, glaciers covered only 54% of the region. Today, the shrinking glaciers occupy only about half of it. New landscape (landforms, Quaternary deposits, water bodies, etc.) develops in land areas abandoned by glaciers. Animal colonization and plant succession lead to soil formation and new ecosystems development. Simultaneously, new seascape and marine ecosystems origin, especially off the northern and eastern coasts where majority of the area released from glaciers was flooded with sea water. In result, biodiversity changes and increases quickly. If climate does not cool the peninsula will be transformed into a new island after connection of two mentioned fjords into a new strait, 50 km long, due to a progressive melting of the glacial isthmus between them in the nearest future. This new island would be the biggest in the Arctic (> 1000 km2). This new strait would connect two aforementioned seas, changing circulation of the sea currents and thus all the environment there.