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

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.