North Atlantic marine species are responding to climate change in multiple ways including changes in species distributions (bioegeographical shifts), community composition and alterations to seasonal cycles.  Plankton, with their short lifespans and sensitivity to their surroundings, are particularly responsive to environmental change. While climate change is driving large-scale alterations to our seas, society is recognising the need to manage human activities impacting the marine environment. In Europe, this is happening via the Marine Strategy Framework Directive, the objective of which is to achieve Good Environmental Status (GES) in European seas by 2020 (for more on the MSFD, check out my recent blog post). The simultaneous influence of manageable human pressures and climate change on Europe’s seas presents formidable challenges to EU policy makers and marine scientists:  what are the interactions between climate change and the MSFD descriptors? how can we separate changes driven by climate, unmanageable at the MSFD time scale, from those driven by manageable anthropogenic pressures? and, will climate change prevent the achievement of GES?

From Elliott et al 2015: Species re-distribution and community response due to altered temperature regime. MSFD descriptor numbers in parentheses. Descriptor 1 (D1): Biodiversity, D2: Non-indigenous species, D3: Commercial fish, D4: Foodwebs, D6: Seafloor integrity.

In the new paper by Elliot et al (2015) we show how one aspect of climate change (altered temperature regimes) interacts with one aspect of marine ecology (species re-distribution and community response). These effects have been observed in CPR data where we’ve found that marine plankton are responding to warming oceans through biogeographical shifts. So, as North Atlantic sea surface temperature increases, warm-water plankton are shifting northwards, while cold-water taxa are squeezed poleward (Beaugrand et al 2002). The conceptual model shows what we know, or think we know, about this small aspect of climate change influence on the plankton, and in Elliott et al 2015 we provide several such figures examining a range of interactions (I selected this one for here as it is plankton relevant). This model illustrates the complex nature of interactions between climate change and marine ecology, which interact with MSFD descriptors. It is these interactions which foster confusion when setting baselines, defining GES, and constructing environmental targets.

As North Atlantic sea surface temperature increases, warm-water plankton are shifting northwards, while cold-water taxa are squeezed poleward (Beaugrand et al 2002). This is an illustration of a climate-driven biogeographical shift.

The marine ecosystem we see today is different from that of a century ago and different still from what it will be in twenty years. While part of ecosystem change is attributable to anthropogenic pressures, climate change is also a key influence, affecting the temperature, chemistry and hydrology of our seas, and shifting the baselines needed to set targets. This means that ecological targets set today may not be applicable in a decade’s time. If we set, for example, an abundance target representing GES for plankton, or for any other mobile species, how do we account for climate-driven distributional and range shifts in that species which may prevent us from meeting our target? Baselines, and therefore targets, must be dynamic, rather than static, triggering management action only where necessary.

Monitoring is needed to evaluate the current state of the marine environment and to assess progress towards Good Environmental Status targets. If we don’t have a clear picture of our ecosystem and how it’s changing, how will we know if we have indeed achieved GES? Maintaining ecological time-series, particularly those, such as the Continuous Plankton Recorder survey, which are spatially expansive and cost effective, are crucial for providing the data necessary to inform baselines used for target setting and to asses and interpret change. When it comes to managing the marine environment during this time of unprecedented climate change, it is no surprised that gaps in our scientific knowledge exist and there are still many things we don’t understand, such as how climate change affects organisms’ physiology, community interactions and responses to habitat change. While modelling advancements are increasing our knowledge of ecosystem responses to climate change, ecological data, often obtained from monitoring programmes, are needed to further our understanding of many issues.

So, will climate change affect our ability to achieve GES? Is the achievement of GES force majeure – out of our control? There is no doubt (in my mind, as I have previously mentioned on Plankton and Policy) that climate change is the greatest challenge to effective marine environmental management. I don’t think, however, that climate change must prevent achievement of GES. GES is still attainable through the setting of robust targets that accommodate climate change but trigger management action when undesirable change is caused by an anthropogenic pressure. Separating the climate signal from that caused by anthropogenic pressure, however, is not an easy task, and remains a key scientific challenge. Good data is integral to meeting this challenge, giving monitoring programmes like our Continuous Plankton Recorder survey a place to shine.  Actually using this data to set robust targets is another issue still, but that’s the subject for a different blog post (and another paper!).

Abigail, Plankton and Policy

Read more: Elliott, M., Borja, Á., McQuatters-Gollop, A., Mazik, K., Birchenough, S., Andersen, J.H., Painting, S. and Peck, M., 2015. Force majeure: will climate change affect our ability to attain Good Environmental Status for marine biodiversity? Marine Pollution Bulletin, in press.