Sea urchin reproductive performance in a changing ocean: Poor males improve while good males worsen in response to ocean acidification

This is the final version. Available on open access from the Royal Society via the DOI in this recordData accessibility: The datasets supporting this article have been uploaded as part of the electronic supplementary material.Ocean acidification (OA) is predicted to be a major driver of ocean biodiversity change. At projected rates of change, sensitive marine taxa may not have time to adapt. Their persistence may depend on pre-existing inter-individual variability. We investigated individual male reproductive performance under present-day and OA conditions using two representative broadcast spawners, the sea urchins Lytechinus pictus and Heliocidaris erythrogramma. Under the non-competitive individual ejaculate scenario, we examined sperm functional parameters (e.g. swimming speed, motility) and their relationship with fertilization success under current and near-future OA conditions. Significant inter-individual differences in almost every parameter measured were identified. Importantly, we observed strong inverse relationships between individual fertilization success rate under current conditions and change in fertilization success under OA. Individuals with a high fertilization success under current conditions had reduced fertilization under OA, while individuals with a low fertilization success under current conditions improved. Change in fertilization success ranged from −67% to +114% across individuals. Our results demonstrate that while average population fertilization rates remain similar under OA and present-day conditions, the contribution by different males to the population significantly shifts, with implications for how selection will operate in a future ocean.European Union Horizon 2020Marie Curie Alumni AssociationCompany of BiologistsNSW Environmental Trus

Larval cloning in the crown-of-thorns sea star, a keystone coral predator

The crown-of-thorns starfish (COTS), Acanthaster cf. solaris, is an iconic keystone predator whose population outbreaks have devastating consequences for Indo-Pacific coral reefs. We tested the effects of algal food supply and larval density on the frequency of larval cloning by culturing the early bipinnaria larvae of COTS under variable conditions. Here we show that larval COTS are able to clone themselves in both low and high food conditions, and that the frequency of larval cloning increases with levels of food, but is unaffected by larval density. Across all density treatments (0.3, 1.0 and 3.0 larvae ml-1), the per-capita rate of cloning increased from 4.3% in low, oligotrophic conditions (0.17 µg chl a l-1) to 7.9% in high food conditions (1.7 µg chl a l-1). Larval cloning has the potential to increase both COTS larval supply and the dispersal distance of planktonic larval stages, both of which are critical factors in predicting the timing and location of outbreaks of this species. In addition, the relationship between algal food supply and larval cloning frequency lends support to bottom-up hypotheses (e.g. nutrient enrichment) as predictors of COTS outbreaks. However, cloning was observed even under the oligotrophic conditions characteristic of coral reefs

Inoculating legumes: a practical guide

Elizabeth Drew, David Herridge, Ross Ballard, Graham O’Hara, Rosalind Deaker, Matthew Denton, Ron Yates, Greg Gemell, Elizabeth Hartley, Lori Phillips, Nikki Seymour, John Howieson and Neil Ballar

Inoculating Legumes: Practice and Science

Atmospheric nitrogen (N) is fixed by symbiotic root-nodule bacteria (rhizobia) associated with pasture and pulse legumes and has a national value of about $3.5 billion annually. This is based on nitrogen fixation rates of about 70 kilograms per hectare per year, crop and pasture legume areas of close to 50 million ha and fertiliser N costed to the grower at$0.76/kg, which equates to $1.00/kg plant-available N in the soil after accounting for N losses. The price of carbon-based fossil fuels, used in the production of nitrogenous fertilisers, is expected to increase in the future which will push fertiliser costs higher. Added to that are the environmental costs associated with the production, distribution and application of nitrogenous fertilisers. Therefore, the historical and ongoing interest by Australian farmers in using legumes which fix nitrogen in their farming systems makes good economic and environmental sense and needs to be sustained into the future

Knowledge gaps in the biology, ecology, and management of the Pacific crown-of-thorns sea star, Acanthaster sp., on Australia's Great Barrier Reef

Published online 17 November 2021Crown-of-thorns sea stars (Acanthaster sp.) are among the most studied coral reef organisms, owing to their propensity to undergo major population irruptions, which contribute to significant coral loss and reef degradation throughout the Indo-Pacific. However, there are still important knowledge gaps pertaining to the biology, ecology, and management of Acanthaster sp. Renewed efforts to advance understanding and management of Pacific crown-of-thorns sea stars (Acanthaster sp.) on Australia’s Great Barrier Reef require explicit consideration of relevant and tractable knowledge gaps. Drawing on established horizon scanning methodologies, this study identified contemporary knowledge gaps by asking active and/or established crown-of-thorns sea star researchers to pose critical research questions that they believe should be addressed to improve the understanding and management of crown-of-thorns sea stars on the Great Barrier Reef. A total of 38 participants proposed 246 independent research questions, organized into 7 themes: feeding ecology, demography, distribution and abundance, predation, settlement, management, and environmental change. Questions were further assigned to 48 specific topics nested within the 7 themes. During this process, redundant questions were removed, which reduced the total number of distinct research questions to 172. Research questions posed were mostly related to themes of demography (46 questions) and management (48 questions). The dominant topics, meanwhile, were the incidence of population irruptions (16 questions), feeding ecology of larval sea stars (15 questions), effects of elevated water temperature on crown-of-thorns sea stars (13 questions), and predation on juveniles (12 questions). While the breadth of questions suggests that there is considerable research needed to improve understanding and management of crown-of-thorns sea stars on the Great Barrier Reef, the predominance of certain themes and topics suggests a major focus for new research while also providing a roadmap to guide future research efforts.Morgan S. Pratchett … Camille Mellin … et al