Studied species

Echinoderms
Echinoderms are a vital component of the marine environment with representatives in virtually every ecosystem; where they are often keystone ecosystem engineers. In addition, many are indirect developers (e.g. urchins, brittlestars) where both larva and adult have critical (and quite different) episodes of skeletogenic calcification. In contrast others (Asteroids) exhibit adult but not larval skeletogenesis. In this way echinoderms offer a valuable and tractable model experimental system for exploring the impacts of OA on marine biota. We are using our CO₂–based sea water acidification system to investigate the affects of increasing acidity on early developmental success in the brittlestars Amphiura filiformis and Ophiothrix fragilis, the sea star Asterias rubens and the sea urchin Strongylocentrotus droebachiensis. Our data show that the impact of acidification on larval development is species-specific and highlight the danger of extrapolation from just a few species, even within closely related taxa. In parallel we are exploring the impact of OA on adult echinoderm growth and development by employing the unique regenerative capacity of echinoderms as a tool to analyse adult skeletogenesis under conditions of increasing ocean acidity.

Tunicates
Until now, tunicates have not been a priority target for research on the consequences of OA. However it is important to note that some tunicates are keystone species in many ecosystems and some are known for their potential as invasive species. With only few predators, they can spread rapidly and endanger native taxa while some are also considered a major threat to aquaculture. We are investigating the impact of pH changes predicted by the year 2100 (0.2 – 0.4 pH units) on the long term development of two benthic tunicates; Ciona intestinalis and Ascidiella aspersa, both of which can form dense populations with up to several thousand individuals per square meter and the pelagic Oikopleura dioica, an important component of this ecosystem bridging between small primary producers and higher consumers. Our results indicate that, surprisingly, tunicates perform better in acidified water for all tested parameters. For example, they grow and develop more rapidly and we observed a significant increase in fecundity.