Category: Marine ecology

Molecular mechanisms underpinning transgenerational plasticity in the green sea urchin Psammechinus miliaris

Melody s. Clark, Coleen C. suckling, Alessandro Cavallo, Clara L. Mackenzie, Michael A.S. Thorne, Andrew J. Davies & Lloyd S. Peck

www.nature.com/articles/s41598-018-37255-6

The pre-conditioning of adult marine invertebrates to altered conditions, such as low pH, can significantly impact offspring outcomes, a process which is often referred to as transgenerational plasticity (TGP). This study describes for the first time, the gene expression profiles associated with tGp in the green sea urchin Psammechinus miliaris and evaluates the transcriptional contribution to larval resilience. RNA-Seq was used to determine how the expression profiles of larvae spawned into low pH from pre-acclimated adults differed to those of larvae produced from adults cultured under ambient pH. The main findings demonstrated that adult conditioning to low pH critically pre-loads the embryonic transcriptional pool with antioxidants to prepare the larvae for the “new” conditions. In addition, the classic cellular stress response, measured via the production of heat shock proteins (the heat shock response (HsR)), was separately evaluated. None of the early stage larvae either spawned in low pH (produced from both ambient and pre-acclimated adults) or subjected to a separate heat shock experiment were able to activate the full HSR as measured in adults, but the capacity to mount an HSR increased as development proceeded. this compromised ability clearly contributes to the vulnerability of early stage larvae to acute environmental challenge.

Oceanographic setting and short-timescale environmental variability at an Arctic seamount sponge ground

E.M. Roberts, F. Mienis, H.T. Rapp, U. Hanz, H.K. Meyer, A.J. Davies (Roberts is a Post-doc, and Meyer an MSc student with Davies)

Mass occurrences of large sponges, or ‘sponge grounds’, are found globally in a range of oceanographic settings. Interest in these grounds is growing because of their ecological importance as hotspots of biodiversity, their role in biogeochemical cycling and bentho-pelagic coupling, the biotechnological potential of their constituent sponges, and their perceived vulnerability to physical disturbance and environmental change. Little is known about the environmental conditions required for sponges to persist and for grounds to form, and very few studies have explicitly characterised and interpreted the importance of oceanographic conditions. Here, results are presented of the first observational oceanographic campaign at a known sponge ground on the Schultz Massif Seamount (SMS; Arctic Mid-Ocean Ridge, Greenland / Norwegian Seas). The campaign consisted of water column profiling and short-term deployment of a benthic lander. It was supported by multibeam echosounder bathymetry and remotely operated vehicle video surveys. The seamount summit hosted several environmental factors potentially beneficial to sponges. It occurred within relatively nutrient-rich waters and was regularly flushed from above with slightly warmer, oxygen-enriched Norwegian Arctic Intermediate Water. It was exposed to elevated suspended particulate matter levels and oscillating currents (with diurnal tidal frequency) likely to enhance food supply and prevent smothering of the sponges by sedimentation. Elevated chlorophyll a concentration was observed in lenses above the summit, which may indicate particle retention by seamount-scale circulation patterns. High sponge density and diversity observed on the summit is likely explained by the combination of several beneficial factors, the coincidence of which at the summit arises from interaction between seamount geomorphology, hydrodynamic regime, and water column structure. Neighbouring seamounts along the mid-ocean ridge are likely to present similarly complex oceanographic settings and, as with the SMS, associated sponge ground ecosystems may therefore be sensitive to changes over a particularly broad range of abiotic factors.

Full Citation

E.M. Roberts, F. Mienis, H.T. Rapp, U. Hanz, H.K. Meyer and A.J. Davies (2018) Oceanographic setting and short-timescale environmental variability at an Arctic seamount sponge ground, Deep-Sea Research Part I 138, 98-113. https://doi.org/10.1016/j.dsr.2018.06.007

Authors Accepted Manuscript

Download the Authors Accepted Manuscript here.

Publisher Version

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Dataset Download

https://doi.org/10.1594/PANGAEA.891035

Optimising stocking density for the commercial cultivation of sea urchin
larvae

Suckling CC, Terrey D, Davies AJ

Increased pressure on wild stocks of sea urchins had led to a requirement for aquaculture based production. However, effective and efficient methodologies still remain under development. The effects of stocking density on Psammechinus miliaris and Paracentrotus lividus were investigated in order to evaluate optimum stocking densities for large scale production. Larvae were reared at stocking densities of 1, 2, 3 and 4 larvae mL−1 and the effects on survival, development, abnormality and morphology were recorded. Additional cultures were maintained at a high density of 3 larvae mL−1 and then displaced to a lower density of 1 larvae mL−1 part way through the larval life cycle (‘displacement treatment’; day 13), to evaluate whether negative effects of high stocking densities could be mitigated. Responses from each species differed. P. miliaris demonstrated the highest growth at 1 larvae mL−1, resulting in larger larval and rudiment sizes by the end of the experiment (day 16). Rearing at 2 larvae mL−1 also demonstrated good growth performance, but only up to day 12. Higher densities of 3 and 4 larvae mL−1 did not affect survival or development, but significantly negatively impacted growth. There was no significant impact on survival, development, and morphology at any of the tested stocking densities for P. lividus. However, of note is that P. lividus reared at a high density of 4 larvae mL−1 had 25% lower survival than controls by the end of the experimental period (day 16). Displacement (larvae transferred from 3 to 1 larvae mL−1 on day 13) was effective for both P. miliaris and P. lividus with survival and rudiment sizes similar to larvae stocked continuously at low densities of 1 larvae mL−1. Although, P. lividus generally performed well at high densities, this demonstrates that displacement approaches could be possible for this species if required. However, of note is that displaced P. lividus had 30% lower survival than controls by the end of the experimental period (day 16). Therefore, this cultivation approach may be a generally viable option for large scale cultivation of these species. This study highlights that species responses can be different when reared at differing stocking densities highlighting a need to expand this approach to a wider range of marketable species. It also demonstrates that more efficient means of production (e.g. displacing larval densities part way through the production process) might be possible for some species (e.g. P. miliaris).

Full Citation

Suckling CC, Terrey D, Davies AJ (2018) Optimising stocking density for the commercial cultivation of sea urchin larvae, Aquaculture, 408: 96-104 DOI: 10.1016/j.aquaculture.2018.01.022

Link

https://doi.org/10.1016/j.aquaculture.2018.01.022