Impacts of marine seismic surveying on the plankton community

A recent study by McCauley et al. (2017) describes the fascinating and worrying observation that the noise produced during marine seismic surveys, commonly used to map geology, may severely impact the plankton community which underpins the entire marine trophic structure and food web 1.

Noise pollution is often an overlooked impact of human activity on the oceans, but it may be having severe and unseen consequences for marine wildlife. One activity that appears to generate excessive amounts of noise is seismic surveying which is used regularly during: exploration for gas and oil deposits, marine engineering work, and, geological research. Typically, an array of air guns is towed just under the surface of the water, firing, repeatedly, a pulse towards the sea floor. The vibrations reflecting up from the sea floor, or objects in the water column, is measured using sonar technology and discrepancies in the returning signal is used to accurately map features on the sea floor 2.


Much of the previous research into the consequences of seismic surveying have focused on its impacts on taxa such as sea turtles, fish and especially cetaceans. Little attention however has been given to the impacts of seismic surveying on the plankton community.


McCauley et al’s. (2017) research shows how the use of a single air gun can reduce plankton abundance in the area immediately surrounding the test location. The researchers in-situ experiment off the south coast of Australia involved towing an active air gun like those used in seismic surveying along a transect, and using sonar to measure the returning backscatter, which alongside vertical plankton-net tows, was used to measure zooplankton abundance. Following exposure to the air gun, and after accounting for water drift, there were significantly less plankton individuals per m3 at all distances measured from the air gun transect. Interestingly, the sonar backscatter analysis also demonstrated a ‘hole’ appearing the returning signal which expanded over time following air gun exposure, indicating a reduction in plankton abundance 1.

The vertical plankton-net tows also indicated that airgun exposure may significantly increase the risk of plankton mortality. More dead plankton individuals were found following exposure compared to the control, and like abundance, this pattern was found at all distances measured from the transect. Interestingly, some taxa appeared more susceptible than others. All Krill larvae were found dead following exposure, and smaller Copepods were also particularly vulnerable. Given the delicate balance that the different marine trophic levels are in, even the slightest change in specific taxa abundance may have severe consequences on the entire marine ecosystem.

These worrying findings were observed after the use of only one air gun. Perhaps future research in the field could try to investigate the realistic impacts that an entire array of airguns would have on the plankton community. The experiment was replicated on two consecutive days and, whilst similar patterns were found on each day, it would be interesting to investigate the long-term impacts continuous seismic surveying may be having on the marine ecosystem. The mechanism by which seismic surveying kills and reduces the abundance of zooplankton is currently unclear and should be an immediate candidate for future research. The authors however hypothesise that the intense shock-waves produced by functioning air guns may damage the sensitive organs of individual plankton, specifically sensory organs imperative for locomotor ability. This may have even changed their orientation in the water, producing the characteristic ‘hole’ present in their backscatter analysis 1.

Though research into the impacts of noise on plankton appears in its infancy, this initial finding by McCauley and colleagues should be of immediate concern. Questions remain, how widespread is the damage, is it reversible, what are the consequences and how do we stop it? Answers which cannot come soon enough.

The long-awaited Blue Planet 2 series presented by Sir David Attenborough has recaptured the public’s fascination with the marine ecosystem (okay, maybe I’ve been slightly optimistic), and since our oceans are under immediate threat from human activity, what better time is there to push marine conservation issues further into the public consciousness. With recent geopolitical events, especially the governmental attitudes of some powerful nations towards internationally agreed environmental pledges, one ‘could’ be forgiven for resigning themselves to ignoring the depressing state of our planet’s natural ecosystems. We in the community however have a moral responsibility to communicate scientific findings to the wider audience to ensure that they are not continuously ignored.

  1. McCauley, R. D. et al. Widely used marine seismic survey air gun operations negatively impact zooplankton. Nat. Ecol. Evol. 1, 0195 (2017).
  2. Gisiner R. C. Sound and Marine Seismic Surveys. Acoustics Today: Winter 2016 10 – 18.



Microplastics and Zooplankton

With the long awaited Blue Planet 2 series around the corner, its presenter David Attenborough describes the heart-breaking tale of watching a breeding albatross mistakenly trying to feed plastic to her chick 1,2. Unfortunately these events are not uncommon, but dumping plastic into our oceans may be having another serious and yet unseen consequence.

Take a beaker of sea-water, put it under a microscope, and you will see it polluted with tiny plastic particles, under 5mm in diameter, called microplastics. These small plastics are produced specifically, such as for personal hygiene products, or result from the degradation of larger debris. Microplastics are now considered ubiquitous across the marine environment and they have been transported, via ocean currents, to even the remotest regions. Including arctic waters, isolated islands and to the bottom of our oceans 3.

Look at the beaker again, and you will see it is also teaming with microscopic animals called zooplankton. These organisms are a crucial energy transfer mechanism between marine trophic levels as they graze on bacteria and phytoplankton, and themselves are predated on by planktivorous species. They also play a role in marine nutrient cycling as their faecal pellets drift down through the water column, forming a component of the marine snow, providing a nutrient input into deeper waters 4.

Given their importance, it is worrying that research is now showing that the presence of microplastics in the marine environment is negatively impacting the zooplankton community.


Shampoo containing relatively large plastic microbeads

Several zooplankton taxa have been observed ingesting microplastics, including the ecologically important copepods, which may not be able to differentiate between them and similar sized prey 3,5,6. Cole et al. (2015) for example showed that the copepod Calanus helgolandicus would ingest 20µm diameter polystyrene microbeads via selective filter feeding, even in the presence of their algal prey. After microbead ingestion, C. helgolandicus consumed significantly smaller, and therefore less, algal cells. During reproduction, exposed individuals also suffered from producing smaller eggs with lower chances of hatching successfully 6. Research such as this suggests the physical effects of polystyrene microbeads are inhibitory to the behaviour and individual fitness of zooplankton, or at least, copepods. Perhaps future research should investigate their impact on alternative zooplankton taxa, and their potential chemical effects on the zooplanktons’ endocrine system by using less stable plastic compounds. Additionally, given the fact that exposed C. helgolandicus were shown to produce more eggs, even though they were smaller, it might be worthwhile investigating the influence of microplastics on overall reproductive fitness. Possibly over multiple generations and or at a population level. Nevertheless, the findings of this research are incredibly concerning, especially as it didn’t consider the influence of smaller microplastics that can adhere to the external surfaces of zooplankton. An issue that is likely to only add to their negative impact.


An example Copepod

If these findings are found to apply to other zooplankton taxa, something that research is continuing to address, microplastic pollution may reduce the abundance of zooplankton in the marine environment. This will reduce prey availability for planktivorous species, which will then have a knock-on effect for the predators at higher trophic levels. A sequence of events known as a trophic cascade. Exposed zooplankton also eject faecal pellets laden with microplastics, which may influence their role in marine nutrient cycling as they sink at a slower rate, and are more likely to be consumed by other organisms in the water column. Potentially reducing the amount of nutrients reaching the deeper ecosystems. The pellets that do reach bottom however may serve to pollute these areas with microplastics as well 7.

As human industrial activity continues to intensify, plastic production is likely to increase and we are only now beginning to understand the severity of microplastic pollution and its implications on the marine ecosystem. Moves such as the UK banning the use of microbeads in cosmetic and personal products is certainly a positive move, but, I fear this is not enough 8. Perhaps better waste management and the development of biodegradable materials are also necessary. As for the plastic already polluting our oceans, who knows? Perhaps the possibility of using plastic eating enzymes/bacteria in the near future will act as a solution 9, but regardless, we must start taking responsibility for protecting our oceans.

  1. Marris, S (2017, September 15th). Sir David Attenborough: Sea plastic’s impact on albatross is ‘heartbreaking’. SkyNews.
  2. Harvey, F (2017, September 25th). David Attenborough on the scourge of the oceans: ‘I remember being told plastic doesn’t decay, it’s wonderful’. The Guardian.
  3. Auta H.S., Emenike C.U., Fauziah S.H. (2017). Distribution and importance of microplastics in the marine environment: A review of the sources, fate, effects, and potential solutions. Environment International 102 165-176.
  4. Turner J.T. (2002). Zooplankton fecal pellets, marine snow and sinking phytoplankton blooms. Aquat Microb Ecol 27 57–102.
  5. Cole M., Lindeque P., Fileman E., Halsband C., Goodhead R., Moger J., Galloway T.S. (2013). Microplastic Ingestion by Zooplankton. Environ Sci Technol 47 6646–6655.
  6. Cole M., Lindeque P., Fileman E., Halsband C., Galloway T.S. (2015). The Impact of Polystyrene Microplastics on Feeding, Function and Fecundity in the Marine Copepod Calanus helgolandicus. Environ Sci Technol 49 1130–1137.
  7. Cole M., Lindeque P., Fileman E., Clark J., Lewis C., Halsband C., Galloway T.S. (2016). Microplastics Alter the Properties and Sinking Rates of Zooplankton Faecal Pellets. Environ Sci Technol 50 3239–3246.
  8. BBC News (2016, September 3rd). Plastic microbeads to be banned by 2017, UK government pledges. BBC
  9. Coghlan A. (2016, March 10th). Bacteria found to eat PET plastics could help do the recycling. New Scientist.


The New Epoch

The Age of Man may soon be taking on an entirely new meaning as the geological epoch, the Anthropocene, awaits formal approval. The distinct geological periods and epochs of our planet’s 4.6 billion year history each signify specific events in earth’s past, but, humans have had such an impact on the environment that it is now time to leave our current epoch, the Holocene, behind. One habitat in which we know humans have had a significant influence is the marine environment, but, as this website will attempt to explain, what exactly are the consequences of this anthropogenic activity upon it, and to what exact will this affect life as we know it.

What is the Anthropocene?

The Anthropocene, a term originally coined by Crutzen and Stoermer (2000)1, refers to a new geological epoch which is dominated by intense human activity and was officially proposed by the Working Group on the Anthropocene (WGA) at the 35th International Geological Congress (2016)2. Despite arguments regarding it’s start date, some suggesting the mid-20th Century, it would represent a significant step in the history of human kind and the end of the Holocene which has lasted since the end of the last Ice Age around 11,700 years ago 2,3,4.

To be accepted by the international geology community there must be a clear distinction between the Anthropocene and the Holocene evident in the sedimentary rock strata and ice beneath our feet. These markers can take on many forms but may include radioactive material from nuclear activity, processed metals and alloys, plastics and or ‘black carbon’ resulting from incomplete combustion of fossil fuels. Additionally, alterations in the patterns of erosion or sedimentation due to construction activity, anthropogenic influenced fossilisation and or differences in carbon dioxide and ozone trapped in ice core samples may also be used as boundary markers 5,6. Even whilst we wait for official acceptance, the impact of humans upon the natural world should not be ignored and instead efforts should be made to ensure everyone is aware of the influence we are having 2.

Why are the oceans important?

The oceans are a vital ecosystem for a large proportion of the global population, especially coastal and developing communities. It provides a vital source of nutrition, and through commercial activity, can play an important role in income generation and economic viability. Around 3.1 billion people rely on fish for 20% of their per capita animal protein consumption, it accounts for around 17% of global animal protein intake (6.7% of ‘all’ protein consumed), and is especially important for developing and ‘low-income food deficit’ communities. A role that is likely to increase in relevance as the human population continues to grow 7,8. Oceans are also important for global system and ecosystem functioning. Photosynthesising phytoplankton are thought to produce around two-thirds of the earth’s atmospheric oxygen and therefore helps to underpin life for all terrestrial animals 9. Additionally the oceans may be playing a substantial role in inhibiting the negative temperature raising effects of increasing atmospheric greenhouse gases as they have absorbed about 40% of all anthropogenically emitted carbon dioxide from the start of the industrial revolution 10. It’s clear that the oceans are a vital component for the functioning of our planet and effort should be made to understand the potential damage humans are inflicting on it in order to hopefully prevent further consequences.

Make sure to check back here at for opinion pieces and research summaries regarding marine conservation and other topics associated with human impacts on the marine environment.   

Source information

  1. Crutzen P.J, Stoermer E.F. (2000). The “Anthropocene”.  Global Change Newsletter 41
  2. Working group on the Anthropocene. What is the ‘Anthropocene’? – current definition and status. [Date accessed: 22/08/2017]
  3. International Commission on Stratigraphy. International Chronostratigraphic Chart. [Date accessed: 22/08/2017]
  4. International Commission on Stratigraphy. GSSP Table – All Periods. [Date accessed: 22/08/2017]
  5. Waters C.N. et al. (2016). The Anthropocene is functionally and stratigraphically distinct from the Holocene. Science 351 6269
  6. Jablonski D., Shubin N.H. (2015). The future of the fossil record: Paleontology in the 21st century. PNAS 112 16
  7. (2017). Worldometer. Dover, Delaware, USA.
  8. FAO (2016).The State of World Fisheries and Aquaculture 2016. Contributing to food security and nutrition for all. Rome. 200 pp.
  9. University of Leicester (2015). “Failing phytoplankton, failing oxygen: Global warming disaster could suffocate life on planet Earth.” ScienceDaily.
  10. Fletcher S.E.M. (2017). Climate science: Ocean circulation drove increase in CO2 uptake. Nature 542 169–170 doi:10.1038/542169a

Noise Pollution and Bluestreak Cleaner Wrasse

Two Bluestreak Cleaner Wrasse (Labroides dimidiatus)  cleaning the mouth of a patient Giant Moray Ell (Gymnothorax javanicus). Photograph by James A. Dawson


From the whirr and hum of ship propellers to the deafening booms of military and construction activity, the oceans are awash with noise. Often overlooked, this pollution may be having a far more detrimental effect on marine wildlife than once thought. An issue that has been recently demonstrated by a study investigating its influence on the behaviour of cleaner fish.



Nedelec et al. (2017) has shown that noise created by passing motorboats may disrupt the fascinating interaction between Bluestreak Cleaner Wrasse (Labroides dimidiatus) and their clientele, other fish of the reef. These cleaner wrasse remove ectoparasites from fish who visit their cleaning stations and is a vital process for the health of individual fish as well as the biodiversity of the reef 2. Under the influence of passing motorboats however, the authors demonstrated that Bluestreak Cleaner Wrasse spent longer cleaning clients and were also more likely to ‘cheat’ by feeding on the mucous instead of ectoparasites. This cheeky behaviour is usually punished by clientele, often through chasing, however under these noisy conditions this cheating is punished less often. A consequence that the authors speculate may result from cleaner wrasse taking advantage of distracted clientele 1.  Though the direct influence of this noise pollution on parasite behaviour and actual parasite removal rate was not investigated, this is a worrying pattern given the importance of these cleaning interactions for reef ecosystems 2. Maybe future research should focus additionally on the influence of louder noises, different sources of noise pollution, and its long-term effects, to truly the predict the potential consequence of future marine based human activity.

Source information

  1. Nedelec SL, Mills SC, Radford AN, Beldade R, Simpson SD, Nedelec B, Côté IM. Motorboat noise disrupts co-operative interspecific interactions. Scientific Reports 7, Article number: 6987(2017). doi:10.1038/s41598-017-06515-2
  2. Waldie PA, Blomberg SP, Cheney KL, Goldizen AW, Grutter AS. Long-Term Effects of the Cleaner Fish Labroides dimidiatus on Coral Reef Fish Communities. Liu DX, ed. PLoS ONE. 2011;6(6):e21201. doi:10.1371/journal.pone.0021201.