Understanding basic life-history characteristics of white abalone (Haliotis sorenseni), such as estimated lifespan, is critical to making informed decisions regarding the recovery of this endangered species. All predictive modelling tools used to forecast the status and health of populations following restoration activities depend on a validated estimate of adult lifespan. Of the seven Haliotis species in California, white abalone is considered to have the highest extinction risk and was the first marine invertebrate listed as an endangered species under the Federal Endangered Species Act (ESA). Lifespan was previously estimated from observations of early growth; however, no study has generated ages for the largest white abalone. To address questions of age and growth, bomb radiocarbon (?14C) dating was used on shells from large white abalone. Measured bomb ?14C levels were compared to regional ?14C reference records to provide estimates of age, growth and lifespan. Bomb radiocarbon dating indicated that growth was variable among individuals, with a maximum estimated age of 27 years. The findings presented here provide support for previous age and growth estimates and an estimated lifespan near 30 years. These age data support the perception of a critical need for restoring the remnant aging and potentially senescent population.

In this study we used decades-old shells of the endangered Northeast Pacific white abalone Haliotis sorenseni to produce high-quality DNA sequences for identification and historical diversity analysis. We obtained mitochondrial (mt) and nuclear DNA sequences (cytochrome c oxidase subunit I and histone H3 respectively) from shells with collection dates bracketing a period of population decline due to overexploitation, from throughout the species’ range. Illustrating the potential of shell DNA for forensic and conservation studies, we found two cases of misidentification among archival shell specimens. Diversity at the mitochondrial marker was lower in H. sorenseni throughout the 20th century than levels recently observed in two sympatric species that also suffered declines. The cause of comparatively low mtDNA diversity in white abalone is unclear; however, it cannot be exclusively linked to exploitation. DNA entombed in shells allowed us to directly establish historical genetic baselines for restoration of this endangered species. Vast repositories of shells exist in museum, aquaculture and private collections; the DNA contained within may be broadly investigated for studies of evolution, archaeology and conservation.

Ice scouring is one of the strongest agents of disturbance in nearshore environments at high latitudes. In depths, less than 20 m, grounding icebergs reshape the soft-sediment seabed by gouging furrows called ice pits. Large amounts of drift algae (up to 5.6 kg/m²) that would otherwise be transported to deeper water accumulate inside these features, representing an underestimated subsidy. Our work documents the distribution and dimensions of ice pits in Fildes Bay, Antarctica, and evaluates their relationship to the biomass and species composition of algae found within them. It also assesses the rates of deposition and advective loss of algae in the pits. The 17 ice pits found in the study area covered only 4.2% of the seabed but contained 98% of drift algal biomass, i.e., 60 times the density (kg/m²) of the surrounding seabed. Larger ice pits had larger and denser algal accumulations than small pits and had different species compositions. The accumulations were stable over time: experimentally cleared pits regained initial biomass levels after one year, and advective loss was less than 15% annually. Further research is needed to understand the impacts of ice scouring and subsequent algal retention on ecosystem functioning in this rapidly changing polar environment.