Human use of the oceans is increasing at an unprecedented rate: fishing and hydrocarbon exploration are increasingly targeting deeper parts of the ocean, and potential deep-sea mining for sulphide minerals on the mid-ocean ridge may bring a new set of impacts that could significantly affect Atlantic ecosystem health. Increasing exploitation of ocean resources is happening in parallel with climate change, which is bringing additional stresses in the form of ocean warming, acidification, and – in some regions – reduced oxygen levels and restricted food supply.
Our understanding of the impacts of multiple stressors on deep- and open-ocean ecosystems is limited because we know very little about how those ecosystems function, and how that functioning naturally varies over the Atlantic. Whilst some research has been done on the effects of single stressors on particular ecosystems, the synergistic effects of different stressors are poorly studied, and there are even bigger gaps in our understanding of how ecosystems in the deep- and open ocean respond to change.
These knowledge gaps limit our ability to predict how ecosystems will respond to stress from multiple sources, which presents a significant barrier to putting robust ecosystem-based management in place. Thus, a key challenge is to understand the synergies between different stressors associated with climate change and those linked to direct human impacts on Atlantic ecosystems.
iAtlantic examined the effects of different climate and man-made stressors on key deep pelagic and benthic organisms, in order to understand and predict how and where multiple stressors could drastically impact ecosystem functions and services. A range of experiments and observing programmes helped provide new information, particularly in areas of the Atlantic where existing data coverage was poor.
iAtlantic took four key approaches:
- Baseline regional ecosystem investigations across natural gradients: using autonomous in situ instruments, field sampling and food web modelling to examine how ecosystem processes and functioning vary across different natural environmental settings in the north and south Atlantic (oligotrophic/eutrophic systems; deep-sea ecosystems located close to land; vulnerable marine ecosystems such as coral reefs) to predict stressor effects.
- Assessment of single and multiple stressors effects on hard-bottom species: Lab experiments measured the effects of changes in temperature, pH and oxygen (in line with the IPCC-predicted warming scenarios), and exposure to particulate matter in order to simulate plumes from deep-sea mining, and to sediments to simulate fishing plumes. Impacts on adult scleractinian corals, gorgonians, sponges, and vent mussels were studied.
- Assessment of single and multiple stressor effects on soft-sediment ecosystems: Lab experiments assessed the single and cumulative impacts of increased temperature and organic matter quality on soft sediment ecosystems using incubation experiments in eutrophic and oligotrophic ecosystems.
- Assessment of the effects of multiple stressors on deep open-ocean pelagic ecosystems: iAtlantic examined how deep-sea pelagic fauna (e.g. copepods, gelatinous zooplankton) and microbial communities responded to changes in ocean temperature and pH, and how sediment/particle plumes created during deep-sea mining will additionally impact these organisms.
Key objectives:
Quantify the impact of environmental stressors on deep-sea pelagic and benthic ecosystems in the Atlantic Ocean:
- Gain knowledge on the baseline functioning of deep-sea pelagic and benthic ecosystems;
- Assess the effects of different environmental stressors on deep-sea pelagic and benthic ecosystem functioning and integrity;
- Assess the effects of different environmental stressors on the larvae of VME organisms;
- Identify tipping points for deep-sea ecosystems in the Atlantic Ocean.
iAtlantic’s work on multiple stressors was led by Prof. Andrew Sweetman at Heriot-Watt University, supported by Dr Marina Carreiro-Silva at Instituto do Mar in the Azores.
