Shallow, shelf and deep-sea Habitats

• North Sea infaunal (burrowing) species have shifted their distributions in response to changing sea temperature, however, most species have not been able to keep pace with shifting temperature, meaning that species are subjected to warmer conditions. Leading (expanding) edges are responding more quickly than trailing (retreating) edges, which has been observed elsewhere in the world. 
   
• Changes in the relative abundance of several UK kelp species, linked to sea-temperature rise, is leading to alterations in the structure of kelp forest assemblages. This has implications for kelp-forest community structure and habitat resilience. 
   
• Changes in phytoplankton and zooplankton communities attributable to climate change impacts affecting primary production directly alter the flux of Particulate Organic Carbon (POC) to the seabed, therefore reducing food supply to deep-sea organisms. 
   
• Deep sea sponge communities have shown resilience to changes in prevailing environmental conditions, therefore may be more adapted to climate change, however the impact of ocean acidification on calcareous and siliceous sponges is poorly understood.  

More detailed confidence rationale and ratings are provided below.  

LOW CONFIDENCE

• Shallow and shelf habitats (Medium evidence, Low consensus). There have been a few studies investigating the impacts of climate change in the UK’s shallow and shelf seas since the last relevant MCCIP Report Card in 2020, but we would suggest that this is for a limited number of species and either over a very limited spatial scale or a global scale. For example, there is strong evidence that some species of kelp are responding to changes in temperature, but we know little about how this is affecting the large number of species reliant on kelp forests for habitat and food. We are also increasingly confident of the drivers of change in infaunal communities associated with a single long-term monitoring site in the North Sea but have much less knowledge regarding the other regions of the UK. For this reason, we assess that the observational evidence is medium, but the level of consensus remains low. 
   
• Deep-sea habitats (Low evidence, Medium consensus). There is a high level of agreement and medium level of evidence concerning how the environment (food supply, physical oceanography) structures and shapes deep-sea communities and ecosystems. However, there is a medium level of agreement and low amount of evidence concerning how deep-sea habitats are currently being affected by climate change. The current dataset of deep-sea habitats is insufficient for the variety that exist within the UK. Even globally, few in situ observations exist that can confirm the projected consequences of change in deep sea oceanographic conditions to species and productivity redistributions, habitat compression, biodiversity loss and changes in body size.

• Modelling suggests that there will be significant shifts in range, distribution and abundance of kelp across the UK by 2050, under low (Representative Concentration Pathways of greenhouse gases, RCP, 2.6), moderate (RCP 4.5) or high (RCP 8.5) emission scenarios in the future, altering the structure, functioning and ecosystem services provided by kelp forests. 
   
• Modelling of climate change impacts on benthic infauna and epifauna within the North Sea also shows altered community structures under a range of emission scenarios by end of century. Such changes are likely to have implications for food-web dynamics, fisheries, carbon cycling and ultimately human society. 
   
• Changes in temperature and pH could lead to increased mortality of the reef forming Desmophyllum pertusum in situ. Lower pH also increases the dissolution of dead coral framework thereby breaking down the reef infrastructure. 
   
• Changes in temperature and pH could lead to increased mortality of the reef forming Desmophyllum pertusum in situ. Lower pH also increases the dissolution of dead coral framework thereby breaking down the reef infrastructure. 
   
• Projections to end of the century conditions have predicted a severe decline in habitat suitability for cold-water corals, for example D. pertusum might see the largest decline in suitable habitat with only 30 to 42% of present-day habitat persisting as climate refugia. 
   
• Global and regional predictions demonstrate that UK deep-sea sediment habitats could be adversely affected by the impact of climate change in terms of primary production, by 2100. Under emissions scenarios RCP 4.5 and 8.5, global declines in seafloor biomass are projected to be <1% by the year 2020, declining by 3% by 2050 and 5.9% by the year 2080.

More detailed confidence rationale and ratings are provided below.

LOW CONFIDENCE

• Shallow and shelf habitats (Medium evidence, Low consensus). Marine Heat Waves (MHWs) are predicted to increase in frequency, spatial extent and duration into the future. While there is currently no published evidence of the impacts of MHWs in shallow and shelf seas in UK waters, this is likely to change into the future. Ecological Niche Models (ENMs) are becoming increasingly sophisticated and estimate current species distributions with some confidence, but again these are limited to a small number of taxa. In addition, such models do not take into account interacting stressors or changes in biotic interactions that may occur in response to climate change. We suggest that the evidence from models is still ‘medium’ since the last review, but the level of consensus is still low due to the limited number of taxa investigated and the range of interacting factors that are not included in ENMs. 
   
• Deep-sea habitats (Low evidence, Medium consensus). There is a medium level of agreement on the possible effects of climate change on UK deep-sea habitats. The models used to predict the effects of climate change on deep-sea habitats are in agreement and there is good consensus on the direction of the effects of climate change. However, the models do not provide a consensus on the magnitude of the effect of climate change on deep-sea habitats and our understanding of species resilience is incomplete. The amount of evidence is low because most of the models provide global or ocean basin level predictions, with few studies providing regional predictions, for example the UK deep sea or even the North Atlantic. To increase the level of confidence in predictions of the future effects of climate change on UK deep-sea habitats, further modelling studies are required at a local scale, for example specifically within UK waters.

• There is clear evidence on the impact of marine heat waves on intertidal and shallow sea communities, however the impact is less well known in the shelf and deep-sea environments. Field-based observational research would be improved with better monitoring of a range of ecological response variables across wider geographical scales, with a focus on regions that are poorly studied but likely affected by MHWs. The usefulness of controlled experiments would benefit from more sophisticated manipulations involving multiple stressors, simulations of MHWs with different properties and a greater diversity and number of experimental organisms.
   
• Given the complexity and uniqueness of the region, more-targeted research is needed to understand the future biogeochemical, ecological and societal consequences, or potential opportunities, of MHWs in UK waters.
   
• There are few direct observation monitoring programmes in UK waters therefore it is difficult to observe what impacts climate change is having on them. Deep-sea habitats in UK waters are generally poorly sampled in time and space except for Station M in the Rockall Trough, Darwin Mounds and the Mingulay reef complex, although both sites lack systematic repeat sampling. More investment is required to fully understand what changes in communities are happening in UK waters.
   
• Regional, rather than ocean-scale, predictions are required to understand how UK habitats will respond to future climate change. Models must consider impacts of multiple stressors on both benthic and pelagic habitats, for example the interaction between ocean acidification and changes in POC.