AbstractsBiology & Animal Science

Laternula elliptica are large bivalves found in high densities in soft sediments in coastal regions of the Southern Ocean. L. elliptica form an important part of the ecosystem, due to significant sediment stabilisation and deposition. Despite the important role L. elliptica play in their environment, little is known about how projected ocean change will impact future populations of this species. Invertebrate larvae are considerably more sensitive to environmental stressors than juveniles and adults, and increases in mortality and minor reductions in dispersal could significantly reduce future population sizes. In a rapidly changing climate, some of the greatest changes are expected at high latitudes. The greatest rates of warming of surface waters are occurring in the Southern Ocean. Additionally, undersaturation of aragonite due to ocean acidification is expected to affect these waters within decades. Calcifying organisms such as molluscs may be particularly sensitive to reduced pH and saturation states associated with ocean acidification. However, information on larval responses to these stressors in Antarctic species is limited. The larvae of L. elliptica are large and lecithotrophic. Maternally provided energy reserves sustain development until the completion of metamorphosis. While large reserves may support long development times and extended encapsulation, they are finite and cannot be replenished. Any stress during larval development could increase metabolic costs and deplete reserves, preventing metamorphosis. These stressors may also impact the calcification process and shell structures, resulting in weaker larvae at settlement that are more vulnerable to injury. Small reductions in larval survival could limit recruitment and population growth may decline. Various responses to ocean acidification (OA) and warming were studied in the larvae of L. elliptica. Larvae were raised under control pH and temperatures (~8.00 and - 1.7°C, respectively) and conditions representing projections for the Antarctic by the end of the century and 2300 (pH 7.80, 7.65 and -0.5, +0.5 and +1.5°C), both individually and in combination. The effect of these stressors on fertilisation rates, development timing and rates of abnormalities at various life stages were examined. Furthermore, SEM analysis determined the impacts of OA and warming on larval shell growth and morphology. Respiration rates and lipid reserves in developing larvae were also determined. Information on OA and temperature responses in Antarctic larvae is limited, and this is the first study on the effects of these stressors in Antarctic bivalves. Elevated temperatures largely improved development, increased early fertilisation rates, and accelerated development through all larval stages and larvae reached competency 5 d ahead of larvae at the control temperature. This would allow for faster settlement, significantly reducing time spent in more vulnerable development stages. Elevated temperatures also improved calcification in later D-stage larvae increasing shell… Advisors/Committee Members: Ken, Ryan, Vonda, Cummings.