Pelagic-benthic coupling describes the connection between surface-water production and seafloor habitats via energy, nutrient and mass exchange. Massive ice loss and warming in the poorly studied ...Arctic Chukchi Borderland are hypothesized to affect this coupling. The strength of pelagic-benthic coupling was compared between 2 years varying in climate settings, 2005 and 2016, based on δ
C and δ
N stable isotopes of food-web end-members and pelagic and deep-sea benthic consumers. Considerably higher isotopic niche overlap and generally shorter isotopic distance were found between pelagic and benthic food web components in 2005 than in 2016, suggesting weaker coupling in the latter, low-ice year. δ
N values indicated more refractory food consumed by benthos in 2016 and fresher food reaching the seafloor in 2005. Higher δ
C values of zooplankton indirectly suggested a higher contribution of ice algae in 2005 than 2016. The difference in pelagic-benthic coupling between these years is consistent with higher energy retention within the pelagic system, perhaps due to strong stratification in the Amerasian Basin in the recent decade. Weaker coupling to the benthos can be expected to continue with ice loss in the study area, perhaps reducing benthic biomass and remineralization capacity; monitoring of the area is needed to confirm this prediction.
•Warmer conditions have promoted range extensions by Arctic benthos.•Modeled temperatures changes are up to +8°C.•Shelf regions of the Chukchi, Kara, and Barents Seas, and West Greenland, are ...hotspots for expansion.•Apparent temperature thresholds help identify candidate taxa for expansion.•A better understanding of species autecologies is needed to improve predictions.
One of the logical predictions for a future Arctic characterized by warmer waters and reduced sea-ice is that new taxa will expand or invade Arctic seafloor habitats. Specific predictions regarding where this will occur and which taxa are most likely to become established or excluded are lacking, however. We synthesize recent studies and conduct new analyses in the context of climate forecasts and a paleontological perspective to make concrete predictions as to relevant mechanisms, regions, and functional traits contributing to future biodiversity changes. Historically, a warmer Arctic is more readily invaded or transited by boreal taxa than it is during cold periods. Oceanography of an ice-free Arctic Ocean, combined with life-history traits of invading taxa and availability of suitable habitat, determine expansion success. It is difficult to generalize as to which taxonomic groups or locations are likely to experience expansion, however, since species-specific, and perhaps population-specific autecologies, will determine success or failure. Several examples of expansion into the Arctic have been noted, and along with the results from the relatively few Arctic biological time-series suggest inflow shelves (Barents and Chukchi Seas), as well as West Greenland and the western Kara Sea, are most likely locations for expansion. Apparent temperature thresholds were identified for characteristic Arctic and boreal benthic fauna suggesting strong potential for range constrictions of Arctic, and expansions of boreal, fauna in the near future. Increasing human activities in the region could speed introductions of boreal fauna and reduce the value of a planktonic dispersal stage. Finally, shelf regions are likely to experience a greater impact, and also one with greater potential consequences, than the deep Arctic basin. Future research strategies should focus on monitoring as well as compiling basic physiological and life-history information of Arctic and boreal taxa, and integrate that with projections of human activities and likely ecosystem consequences to facilitate development of management strategies now and in the future.
Climate-driven regime shifts in Arctic marine benthos Kortsch, Susanne; Primicerio, Raul; Beuchel, Frank ...
Proceedings of the National Academy of Sciences - PNAS,
08/2012, Volume:
109, Issue:
35
Journal Article
Peer reviewed
Open access
Climate warming can trigger abrupt ecosystem changes in the Arctic. Despite the considerable interest in characterizing and understanding the ecological impact of rapid climate warming in the Arctic, ...few long time series exist that allow addressing these research goals. During a 30-y period (1980–2010) of gradually increasing seawater temperature and decreasing sea ice cover in Svalbard, we document rapid and extensive structural changes in the rocky-bottom communities of two Arctic fjords. The most striking component of the benthic reorganization was an abrupt fivefold increase in macroalgal cover in 1995 in Kongsfjord and an eightfold increase in 2000 in Smeerenburgfjord. Simultaneous changes in the abundance of benthic invertebrates suggest that the macroalgae played a key structuring role in these communities. The abrupt, substantial, and persistent nature of the changes observed is indicative of a climate-driven ecological regime shift. The ecological processes thought to drive the observed regime shifts are likely to promote the borealization of these Arctic marine communities in the coming years.
•We provide a review of studies carried out during the Arctic polar night.•Ecologically relevant light during the polar night changes with latitude.•Ecologically, “polar night” and “winter” are not ...synonymous.•The polar night represent a major gap in knowledge concerning Arctic ecosystem understanding.
Several recent lines of evidence indicate that the polar night is key to understanding Arctic marine ecosystems. First, the polar night is not a period void of biological activity even though primary production is close to zero, but is rather characterized by a number of processes and interactions yet to be fully understood, including unanticipated high levels of feeding and reproduction in a wide range of taxa and habitats. Second, as more knowledge emerges, it is evident that a coupled physical and biological perspective of the ecosystem will redefine seasonality beyond the “calendar perspective”. Third, it appears that many organisms may exhibit endogenous rhythms that trigger fitness-maximizing activities in the absence of light-based cues. Indeed a common adaptation appears to be the ability to utilize the dark season for reproduction. This and other processes are most likely adaptations to current environmental conditions and community and trophic structures of the ecosystem, and may have implications for how Arctic ecosystems can change under continued climatic warming.
Climate change is leading to increases in freshwater discharge to coastal environments with implications for benthic community structure and functioning. Freshwater inputs create strong environmental ...gradients, which potentially affect the community structure of benthic infauna. In turn, changes in functional trait composition have the potential to affect the processing of terrestrially-derived nutrients and organic matter along the freshwater to marine continuum. We investigated the effects of riverine inputs on benthic community structure, functional traits, taxonomic and functional diversity, and utilization of terrestrial organic matter in two contrasting northern Norwegian fjords. Results of this study revealed extensive impacts of riverine inputs on community structure and functional traits. Communities directly affected by the river were characterized by diminished taxonomic and functional diversity, with species and trait composition indicative of an environment influenced by high sedimentation rates. Large, deep-dwelling, biodiffusors and upward conveyors dominated these communities. High community biomass at the river outlet as well as indications of terrestrial organic matter utilization evidenced by stable isotope analyses, suggest that such river-influenced communities may be important for the cycling of terrestrial carbon and nutrients in the coastal zone.
Display omitted
•Riverine inputs drive strong gradients in benthic biodiversity and functional traits.•Higher mobility and surface deposit feeding are associated with river inputs.•Terrestrially-derived organic matter is utilized by coastal benthic communities.•River-impacted species display traits related to sediment carbon and nutrient turnover.•Climate change is expected to increase riverine impacts on benthic fjord communities.
Arctic marine ecosystems support fisheries of significant and increasing economic and nutritional value. Commercial stocks are sustained by pelagic food webs with relatively few keystone taxa ...mediating energy transfer to higher trophic levels, and it remains largely unknown how these taxa will be affected by changing climate and the influx of boreal taxa. Calanus species store large quantities of lipids, making these zooplankton a critical link in marine food-webs. The Arctic Calanus species are usually larger and, importantly, have been suggested to contain disproportionately larger lipid stores than their boreal congeners. Continued climate warming and subsequent changes in primary production regimes have been predicted to lead to a shift from the larger, lipid-rich Arctic species, Calanus glacialis and Calanus hyperboreus, toward the smaller, boreal Calanus finmarchicus in the European Arctic, with negative consequences for top predators. Our data show that lipid content is closely related to body size for all three species, i.e. is not a species-specific trait, and that there is considerable overlap in size between C. finmarchicus and C. glacialis. A trait-based life-history model was used to examine an idealized scenario where, in a changed Arctic with a longer period of primary production, C. glacialis- and C. hyperboreus-like copepods are indeed replaced by C. finmarchicus-like individuals, whether through competition, plasticity, hybridization, or evolution. However, the model finds that transfer of energy from primary producers to higher predators may actually be more efficient in this future scenario, because of the changes in generation length and population turnover rate that accompany the body-size shifts. These findings suggest that Arctic marine food webs may be more resilient to climate-related shifts in the Calanus complex than previously assumed.
Tight coupling between pelagic and benthic communities is accepted as a general principle on Arctic shelves. Whereas this paradigm has been useful for guiding ecological research, it has perhaps led ...to a disproportionate focus on POM and ice algae as the most likely sources of carbon for the benthic food web. Arctic shelves are complex systems, including banks, fjords, and trough systems up to 350 m or more in depth. In this stable-isotope study, thirteen different potential carbon sources were analysed for their contribution to the food-webs of Isfjorden, Svalbard. A mixing model with herbivorous copepods and grazing sea urchins as end-members was applied to determine the relative contributions of the most likely carbon sources to pelagic and benthic taxa. Most taxa from the benthos feed on a broad mixture of POM and macroalgal detritus, even at depths down to 410 m. Most suspension-feeding bivalves had isotopic signals consistent with more than a 50% contribution from kelps and rockweeds. In contrast, nearly all pelagic species had diets consistent with an overwhelming contribution of pelagic POM. These results indicate that macroalgal detritus can contribute significantly to near-shore Arctic food-webs, a trophic link that may increase if macroalgae increase in the Arctic as predicted. These weaker quantitative links between pelagic and benthic components of coastal systems highlight the need for thorough sampling of potential carbon-baselines in food-web studies. A large detrital-carbon component in diets of Arctic benthos may dampen the impacts of strong seasonality in polar primary producers, leading to higher ecosystem resilience, but may also result in lower secondary productivity.
The aim of this study was to assess bioturbation rates in relation to macrozoobenthos and environmental variables in the Svalbard fjords, Barents Sea and Nansen Basin during spring to summer ...transition. The results showed differences in benthic community structure across sampled area in relation to sediment type and phytopigment content. Fjords, Barents Sea and the shallow parts of Nansen Basin (<400 m) were characterized by high functional groups diversity, and by biodiffusive and non-local rates ranging from 0.05 to 1.75 cm−2 y−1 and from 0.2 to 3.2 y−1, respectively. The deeper parts of Nansen Basin (>400m), dominated by conveyors species, showed only non-local transport rates (0.1–1 y−1). Both coefficients intensity varied with benthic biomass. Non-local transport increased with species richness and density and at stations with mud enriched by fresh phytopigments, whereas biodiffusion varied with sediment type and organic matter quantity. This study quantified for the first time the two modes of sediment mixing in the Arctic, each of which being driven by different environmental and biological situations.
•This is the first report on bioturbation over a large depth gradient in the Arctic Ocean during spring time.•Benthic community structure and bioturbation activities varied in Svalbard fjords, Barents Sea and Nansen Basin.•Changes in environmental conditions had impact on benthic communities and bioturbation.•Large inputs of fresh OM to the seabed can trigger bioturbation activities.
PDF
