Reproduction in a changing world

Long-term monitoring study

How is reproduction affected by environmental conditions? As the World’s oceans warm, will animals be more or less efficient at producing the next generation? Can we correlate trends in reproductive capacity with climate change?

Reproduction is very costly for any animal. Reproductive capacity and success can often be related to food supply, but it’s not that simple, other environmental factors can play a significant role. So how do we understand this complex process? In particular how do we identify any potential long term signals associated with climate change against what are often massive annual differences?

Monitoring of shallow brittlestars by SCUBA divers suggest they may be very sensitive to small rises in sea temperature.

To answer this question, we need to conduct monitoring studies over many years. Since 1997 we have been collecting monthly samples of five marine invertebrates (a sea star, brittle star, sea cucumber and nemertean and terrebellid worms) from the bays around Rothera Research Station to examine their reproductive capacities. A further three species (a sea urchin and two molluscs) were added from 2013. Multi-year studies of the reproductive patterns of polar marine invertebrates are rare and those that exist show dramatic variations between years.

This project contributes to the BAS Grand Challenge of Polar Change and is part of the RATS (Rothera Antarctic Time Series) biological programme.

BAS organises the monthly collections and preservation of material with analysis carried out with our collaborators in UK universities.

Monthly collections are made for each species. The gonads are then analysed by histological methods. We calculate the maturity index (size of eggs in the gonad or the volume of gonad taken up by sperm) and where possible, the gonad index (the weight of the gonad relative to the weight of the animal).

Our aims are to:

• Quantify seasonal and interannual variation in reproductive capacity
• Identify any long term trends in reproductive capacity
• Correlate any trends with food supply, ice, water chemistry,  phytoplankton and oceanographic measurements, as provided by the RATS oceanographic programme and wider scale climatic phenomenon such as El niño and the Southern Annual Mode (SAM)
• Identify any differences in response to environmental conditions with the thermal tolerances of each species.
• Identify any differences in response between trophic levels: is reproduction more or less variable in primary consumers, such as filter feeders compared with scavengers and predators?

Primary consumers:

Yoldia eightsii (mollusc: suspension and surface sediment feeder)

Heterocucumis steineni (sea cucumber: suspension feeder)

Terrebellid worms (suspension feeder)

Nacella concinna (limpet: mainly a grazer)

Omnivore:

Sterechinus neumayeri  (sea urchin: omnivore/scavenger/grazer)

Scavenger/Predators:

Odontaster validus (sea star)

Ophionotus victoriae (brittle star)

Predator/carnivore:

Parborlasia corrugatus

Project collaborators

Dr Laura Grange, University of Southampton/the National Oceanographic Centre:  analysing Odontaster validus*, Ophionotus victoriae*, Yoldia eightsii, Sterechinus neumayeri and Nacella concinna.

Dr Amanda Bates, University of Southampton/the National Oceanographic Centre: statistical analyses.

Dr Ben Wigham, University of Newcastle:  analysing Heterocucumis steineni* and Parborlasia corrugatus*.

Dr Gordon Watson, University of Portsmouth:  analysing Terrebellid worms*.

Species annotated with an asterisk have been collected since 1997.

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