The effects of climate warming and heatwaves on in situ benthic marine community development

Understanding how, and predicting, the future impact of climate warming on biodiversity is one of the great challenges for environmental sciences, for ecologists and for society. Currently two main approaches exist to address this problem: 1. The matching of species and communities to current environments and predicting from models where those environments will be in future to assess likely new distributions; 2. Assessing the performance of species in experimentally manipulated systems. Both have advantages and drawbacks. The former from unknowns, especially around ability to colonise and distances that can be covered, the importance of biodependencies between species and effects of environmental barriers. The latter suffers from unrealistic rates of change compared to natural systems and a lack of ecological realism, because the vast majority of studies are laboratory based where conditions are held constant with the exception of the variable under investigation. On land experiments have included both laboratory and field based manipulations (e.g. Fordham 2015), and the latter has provided key information not available from lab based studies. Field based experimental manipulations in the sea are more difficult to conduct, especially for temperature because of the large specific heat capacity of water and currents that rapidly remove heat from experimentally warmed areas. However, a method has recently been developed that allows the heating of surfaces of panels in situ in the sea. Biological communities develop on the heated surfaces and the 3-5 mm boundary layer of water over a panel such that for small species the whole life cycle from settlement to reproductive adult is in warmed conditions. This method has great advantages because apart from heating all other ecological factors such as water currents, food supply, salinity, light regime, tides etc remain natural. The approach has been tested in Antarctica where 1°C warming caused growth rates to double in some species and community composition was dramatically impacted (Ashton et al. 2017). Further studies showed that species living on 2°C warmed panels had failed to acclimatize to the higher temperature after 18 months (Clark et al. 2019) and that competitive interactions increased with 1°C warming (Barnes et al. 2021).

The approach encourages small encrusting species to attach to panels, primarily spirorbid worms, bryozoan, sponges and ascidians, all members of the biofouling community. Biofouling of marine structures has serious economic consequences. For example, the blockage of pipes and equipment in the US power industry is estimated to cost around US$60 million per year, and the increased fuel costs for ships due to hull biofouling are suggested to be as high as US$150 billion annually (Selim et al. 2017). In addition, biofouling of fish and shellfish cages is a serious problem for aquaculture, accounting for, 5-10% of production costs (Bannister et al. 2019). The aim of this project is to understand how biofouling in a temperate site will be affected under future climate warming for both constant warming and heatwaves. The project will also address how multiple generation exposure to warmed conditions affects biological performance.

Preliminary trials of these panels in the UK have also shown that even +1°C can produce tipping points in some species in warm summers, and trials of similar panels currently running in New Zealand are showing very large differences of impacts on species performance and community effects in different seasons. So far no one has tested the effects of heatwaves or conducted multiple generation in situ manipulations.


The research will comprise two main components.
1. Heated panels will be deployed at a site near Newcastle University’s Dove Marine laboratory. Four panels will be unheated controls and four panels will be set at each of 1°C and 2°C warming. A fourth set of panels will be allowed to colonise under ambient conditions and then exposed to periods of warming of 2°C of between 1 and 4 weeks, and also repeated heatwaves. Growth rates of colonizing species will be assessed by regular monitoring. Previous pilot work has indicated that monitoring every 2-4 weeks is sufficient to allow growth rates to be assessed and 3 months allows full panel colonization. After full colonization panels will be cleaned and reset to allow impacts in spring, summer, autumn and winter to be evaluated separately. Some panels will be allowed to colonise and grow beyond the 3 month full coverage period to support the assessment of warming on later colonizing species and secondary community development. At the end of standard trials thermal limits will be assessed using rapid warming experiments to identify upper thermal limits. Competition will be quantified as in Barnes et al. (2022).
2. For a separate set of warmed panels colonization will be allowed to continue until full cover. These panels will then be brought into the laboratory where they will be placed in tanks of water warmed to the same temperature as the panel. New uncolonised panels will be placed in the same tanks and colonisation of the new panels allowed to continue. After sufficient colonization has occurred the new panels will be placed in the sea and allowed to develop in situ for 2-3 months. From high quality photographs F1 individuals will be tracked and their growth performance assessed. These panels will then be returned to the laboratory and all non F1 organisms on panels will be removed. The process of colonization of new panels will be repeated to produce an F2 generation, and these will be returned to the sea for further in situ development and assessment of performance. At the end of each cycle the F1 and F2 will have their thermal limits assessed in rapid warming trials to allow performance of growth and thermal resistance to be evaluated across generations in future warming conditions.

If funds permit, or if extra funds can be obtained there will be the possibility of using molecular (gene expression transcriptomic) technologies to assess stress responses and acclimation to altered conditions in the experimentally manipulated species.

The student will be primarily based in Newcastle, but will spend substantial amounts of time in Cambridge.

Project Timeline

Year 1

• Training in panel use, set up of panels and initial trials
• Training in microscopy and identification of key species colonizing panels
• Monitoring of panel colonization and growth performance of key species.
• Presentation of project aims and outlines in suitable conference outlets

Year 2

• Continuation of seasonal evaluations of heated panel experiments to provide >18 months of data.
• Set up and running of multiple generation experiments
• Set up and running of heatwave experiments informed by seasonal data from year 1
• Analysis of data from first rounds of experiments

Year 3

• Complete 2 years of seasonal deployment.
• Analyse seasonal and inter-annual differences in warming impacts
• Write first paper on seasonal and inter-annual effects of warming.
• Repeat multiple generation and heatwave experiments in different seasons
• Analyse data on multiple generation and heatwave impacts
• Present results at suitable conference outlets
• If appropriate conduct gene expression analyses of responses to warming from selected parts of the project

Year 3.5

• Complete data analyses
• Write papers on multiple generation and heatwave aspects of the project
• Produce thesis

& Skills

NU and BAS will provide training in taxonomy, experimental design, molecular techniques and public engagement. NU will provide training in marine community and biodiversity analyses. The student will benefit from being part of a NU DTP cohort where the student will acquire data analysis skills through existing ecological modelling and related post-graduate modules at NU, as well as being a part of the BAS DTP cohort with dedicated training courses and wider training opportunities within the Cambridge area. Other cross-disciplinary skills (e.g. project planning and management; scientific writing and critical analysis; data analysis and statistics) will be gained through specialist modules at NU.

References & further reading

Ashton, G., Barnes, D., Morley, S., Peck, L.S. (2017). Response to van der Meer. Current Biology 27, R1303-1304
Bannister et al. (2019). Biofouling in marine aquaculture: a review of recent research and developments. Biofouling 35, 631-648.
Barnes, D.K.A., Ashton, G.V., Morley, S.A., Peck, L.S. (2021). 1 °C warming increases spatial competition frequency and complexity in Antarctic marine macrofauna. Communications Biology 4, 208.
Clark, M.S., Villota Nieva, L., Hoffman, J.I., Davies, A.J., Trivedi, U.H., Turner, F., Ashton, G. & Peck, L.S., (2019). Lack of long-term acclimation in Antarctic encrusting species suggests vulnerability to warming. Nature Communications 10, 3383.
Fordham, G.A. (2015). Mesocosms reveal ecological surprises from climate change. PLoS Biology 13, e1002323
Selim et al. (2017). Recent progress in marine foul-release polymeric nanocomposite coatings. Progress in Materials Science 87, 1-32.

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