Broadcast Spawning into a Changing Marine Environment - Are Sperm the 'Weak Link' in a Marine Invertebrate's Life Cycle?

Lead Research Organisation: University of Exeter
Department Name: Biosciences

Abstract

Marine coastal ecosystems support some of the most productive and diverse communities on Earth and are globally important in terms of the ecosystem services and functions that they provide, such as nutrient cycling and nursery grounds, and as the base of the coastal marine food chain. Marine invertebrates make up the largest percentage of the animals in these communities and have vital roles in the functioning of all marine ecosystems; however the contributions that marine invertebrates make to these important ecological processes are under threat from anthropogenic influences such as pollution and climate change. A vast quantity of industrial and domestic waste is discharged into the aquatic environment every year. Additionally the increased carbon dioxide in our atmosphere that is causing global warming is also leading to our oceans becoming more acidic. These pose major challenges to the health of the aquatic environment, with the potential to disrupt the life cycles of marine invertebrates and affect their ability to reproduce. Marine invertebrates have evolved many different ways of reproducing, but the majority of these simple animals have maintained the ancestral strategy of releasing sperm freely into the water, so anything that reduces the survival or swimming ability of their sperm may greatly affect fertilization rates and hence the number of offspring that they produce. This strategy leaves sperm vulnerable to changes in environmental conditions, such as those threatened by pollution and climate change. We currently know very little about how sperm might be affected by increasing pollution or ocean acidification. My research will investigate whether the chemicals polluting our seas and the increase in acidity of our oceans can damage sperm or affect sperm swimming, using sperm from three ecologically important marine invertebrate species. I will use the common mussel, a sea urchin species and a polychaete worm, to look at how environmental pollution can damage their sperm by using a number of techniques that measure damage to the sperm DNA and determine whether their sperm are swimming properly. I plan to examine mussels living in contaminated environments to determine the extent of DNA damage in their sperm caused by the polluted waters that they inhabit and compare them to animals from 'clean' habitats to see if they have adapted their sperm in able for them to survive and successfully reproduce in polluted environments. I will also look at how acidified seawater affects sperm swimming behaviour by using sperm tracking equipment and determine if it makes sperm more susceptible to the effects of the environmental chemicals. In parallel studies, cultures of marine worms will be established in the aquarium and the impacts of DNA damaging chemicals frequently found in the marine environment (the polyaromatic hydrocarbon benzo(a)pyrene and copper, a heavy metal) will be studied. Both the nature and extent of damage to DNA will be measured, along with an evaluation the capacity of sperm cells to repair this DNA damage. This research will determine whether marine invertebrate sperm have defence mechanisms that protect them against environmental damage, or whether there is long lasting damage that affects future generations, leading to long term changes in the structure and fitness of the whole population. It will also help us understand how marine invertebrates adapt and survive in polluted environments. Ultimately, the results of my work will enhance our understanding of the long term environmental impact of the changing chemsitry of our seas and the methods used by organisms to protect themselves.

Publications

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Campbell AL (2016) Ocean acidification changes the male fitness landscape. in Scientific reports

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Lewis C (2010) Sperm toxicity and the reproductive ecology of marine invertebrates in Integrated Environmental Assessment and Management

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Lewis C (2012) Infertility in male aquatic invertebrates: a review. in Aquatic toxicology (Amsterdam, Netherlands)

 
Description My Fellowship set out to determine the susceptibility of marine invertebrate sperm to environmentally induced damage caused by the changes in ocean chemistry associated with increased pollution and ocean acidification (OA).



First a theoretical framework was developed (Lewis and Galloway, 2010) outlining potential mechanisms by which reduction in sperm function in broadcast spawning marine invertebrates may be caused by exposure to a range of anthropogenic factors, such as chemical pollution and ocean acidification. A number of potential consequences of environmentally induced sperm damage for a population's reproductive ecology were also hypothesised. A review paper on male infertility in aquatic invertebrates (Lewis and Ford, 2012) was also published providing a synthesis of our current understanding of these impacts. This highlighted a number of key knowledge gaps in our understanding of anthropogenic influences on male fertility and presented a 'tool box' of suitable bioassays that can be used to address these knowledge gaps.



Field collected data on DNA damage in both sperm and somatic cells for natural populations of three polychaetes species (N. virens, Arenicola marina and Pomatoceros lamarckii), mussels, sea urchins, scallops and limpets was collected (paper in preparation) clearly demonstrating environmentally induced damage to sperm does occur in polluted habitats.



Data on natural levels of sperm motility and longevity for three polychaetes species (N. virens, Arenicola marina and Pomatoceros lamarckii), mussels, sea urchins, scallops and limpets was collected. Sperm sensitivity to a range of environmental contaminants, ocean acidification and temperature for three polychaetes species (N. virens, Arenicola marina and Pomatoceros lamarckii), mussels, urchins, scallops and limpets was also collected via laboratory exposures. The impacts of this reduced sperm function on fertilisation success for two polychaete species and an urchin was collected via laboratory experiments and modelling approaches (Lewis et al., 2013 in press and further papers in preparation).
Sectors Environment

 
Description My research expeditions to the Canadian High Arctic as part of additional work undertaken during my Fellowship have been used as the inspiration for a highly successful national schools education programme, introducing oceans education to schools both nationally and internationally. My research expeditions to the Canadian High Arctic as part of additional work undertaken during my Fellowship have been used as the inspiration for a highly successful national schools education programme, introducing oceans education to schools both nationally and internationally. I teamed up with Digital Explorer, a non-profit organisation that pioneers educational expeditions, to provide free inspirational lesson plans and multi-media resources on ocean acidification and Arctic climate change to classrooms both nationally and internationally. The resulting education resources, inspired by my fieldwork in the Arctic, are already being used by 514 UK secondary schools (13% of secondary schools in the UK), reaching over 387,000 pupils within the first 9 months of being launched. These school's resources are also now being used internationally including a training programme in Alaska and as ocean acidification outreach examples across Europe and have to date been seen by over 2.5 million children worldwide.
First Year Of Impact 2012
Sector Education,Environment
Impact Types Societal

 
Description NERC Standard grant
Amount £700,000 (GBP)
Funding ID NE/L007010/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 07/2014 
End 06/2017
 
Description BBC coverage of the recent ES&T publication 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact The BBC covered our recent publication in ES&T showing how ocean acidification increases the toxicity of copper to marine worms. They used our paper in connection to a release for the UK Governments Chief Scientific advisor on ocean acidification.

I did a piece for the Radio 4 Today Programme and an online article for the main BBC news web site. This article was reposted by over 1140 other news outlets that day and there were at least 500 retweets on the article on Twitter.

I was approached by several other online new blobs wanting to cover the story.
Year(s) Of Engagement Activity 2014
URL http://www.bbc.co.uk/news/science-environment-29746880