Assessing the status, variability, and biodiversity conservation issues of Arctic benthic ecosystems of the Pechora Sea for improved management

Abstract

The biodiversity of the Arctic Ocean is described by the Arctic Council as an “irreplaceable cultural, scientific, ecological, economic and spiritual asset”. Global climate change together with industrial development pose major threats to Arctic ecosystems and biodiversity including but not limited to rise in water and air temperatures, loss of sea ice habitats, introduction of nonindigenous species (NIS) and anthropogenic pollution. The urgent need to protect Arctic marine ecosystems and biodiversity is emphasised in many national and international strategies and policy framework documents. Furthermore, improvement of baseline knowledge and implementation of ecosystem-based management are identified as key “actions for biodiversity”.

Macrobenthic communities are one of the most conservative biotic components of marine ecosystems and are therefore prominently used in ecological monitoring as indicators of good environmental status of ecosystems. At the same time, macrobenthic invertebrates are focal ecosystem components as they provide food resources to sustain benthic predators of higher trophic levels. Our knowledge of Arctic benthic ecosystems, their biodiversity, temporal variability, individual and cumulative impacts of environmental stressors remain fragmentary and often insufficient for knowledge-based decision-making. This thesis aimed to improve regional knowledge through assessing the status, variability and biodiversity conservation issues of Arctic benthic ecosystems of the ecologically significant area of the Barents Sea, the Pechora Sea, for improved management.

An extensive dataset on macrobenthos of the Pechora Sea was compiled through participating in a series of expeditions to the Pechora Sea with additional samples obtained in zoological collections or provided by partner institutions (Lomonosov Moscow State University Marine Research Center and Shirshov Institute of Oceanology, Russian Academy of Sciences). A total of 213 grab samples were used to study biodiversity and variability of macrobenthos in two research areas in the Pechora Sea – the Pechora Bay and Vaigach Island. Assessment of video footage obtained using remotely operated vehicles revealed likely increasing in time presence of important benthic NIS snow crab Chionoecetes opilio (O. Fabricius, 1788) near Vaigach Island. Morphological analysis of stomach content was performed to characterise trophic niches of C. opilio and assess overlap with the diets of native benthic decapods, Hyas araneus (Linnaeus, 1758) and Pagurus pubescens Krøyer, 1838. Accumulation of microplastics in benthic invertebrates of the Pechora Sea was then assessed and compared with samples from the Kara Sea, Laptev Sea and East-Siberian Sea.

Macrobenthos of the continental shallows of the Pechora Bay were described for the first time in this thesis. A monodominant community of Limecola balthica (Linnaeus, 1758) comprised of eurythermal and euryhaline forms with reduced biomass, was shown to be at the margins of its distribution. In contrast, near Vaigach Island a high biomass, heterogeneous, macrobenthic community was found. During the six years of observations (2015–2020), the mean biomass, abundance, production and species composition fluctuated with no clear trends between years. Twenty categories of prey items were identified in the diets of benthic decapods near Vaigach Island. Overlap in diets of the three species suggested that C. opilio likely competes for food resources with both H. araneus and P. pubescens. A conceptual diagram was generated to illustrate trophic interspecies relationships between benthic predators and macrobenthic communities in the Pechora Sea.

Microplastics were found to be a likely stressor on Arctic benthic ecosystems. Microplastic fibres were recorded in 29% of all samples of the Pechora Sea macrobenthos. Furthermore, an increase of average frequency of ingested microplastics in the field samples collected in 2017– 2018 compared to the historical samples from 2008 was proved statistically significant. Similar occurrence of ingested microplastics were discovered in other studied regions of the Eurasian Arctic (average 27±2%). No significant differences in occurrence of ingested microplastics were identified between species, feeding guilds or sampling sites. A conceptual diagram was developed to illustrate microplastic ingestion by benthic fauna from different feeding guilds in the Pechora Sea.

Overall, the outcomes of this thesis provided valuable data, which are essential to review the current state of benthic biodiversity in the Pechora Sea, characterise the observed and expected impacts of key drivers of environmental change on benthic ecosystems, and provide recommendations including monitoring parameters and techniques, integration of which into the regional ecological monitoring programmes will lead to a more comprehensive understanding of the state and dynamics of the Pechora Sea benthic ecosystems. The Pechora Sea provides a case study illustrating the importance of incorporating data on benthic ecosystems into the marine spatial planning and specifically the design of marine protected areas, as well as the need for establishment of long-term ecological monitoring programmes with standardised approaches to data collection and interpretation to underpin the informed decision-making needed for sustainable development of the Arctic region.