# Fast and slow depurators of amnesic shellfish toxin: a bioenergetic modelling approach to compare two pectinid species

Eline Le Moan, Laure Régnier-Brisson, Laure Pecquerie, Caroline Fabioux, Fred Jean, Philippe Cugier, Hélène Hégaret, Jonathan Flye-Sainte-Marie

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## ► To cite this version:

Eline Le Moan, Laure Régnier-Brisson, Laure Pecquerie, Caroline Fabioux, Fred Jean, et al.. Fast and slow depurators of amnesic shellfish toxin: a bioenergetic modelling approach to compare two pectinid species. 8th International symposium on Dynamic Energy Budget Theory for Metabolic Organization, Jun 2023, Bâton-Rouge, LA, United States. . hal-04179840

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# Fast and slow depurators of amnesic shellfish toxin: a bioenergetic modelling approach to compare two pectinid species

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LEMAR

lemoan@univ-brest.fr

Eline Le Moan¹, Laure Régnier-Brisson², Laure Pecquerie¹, Caroline Fabioux¹, Fred Jean¹, Philippe Cugier², Hélène Hégaret¹ et Jonathan Flye-Sainte-Marie¹

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DEB2023 - 8th International Symposium and Thematic School
on Dynamic Energy Budget Theory for Metabolic Organization
School: 4-13 June 2023 Symposium: 14-16 June 2023

¹Univ Brest, IRD, CNRS, Ifremer, IUEM, 6539 LEMAR, F-29280 Plouzané, France – ²Ifremer, Dyneco, LEBCO, F-29280 Plouzané, France

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## Introduction

* Microalgae *Pseudo-nitzschia sp.* (Psn) produce domoic acid (DA) and are responsible for amnesic shellfish poisoning (ASP)

* Bivalves as filter-feeders can accumulate the toxin

→ DA concentration in their tissues is monitored

→ If DA concentrations overpass sanitary threshold, fishing activities are closed

* The king scallop *Pecten maximus* and the variegated scallop *Mimachlamys varia* are economically important species in France

* Closures, due to DA presence, implicate socio-economic loss

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**MaSCoET project:** better understanding the development of Psn and the difference in accumulation and decontamination processes between pectinid species

→ The king scallop accumulates more DA and retains it for a longer time

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**Aims:** to determine processes for the king scallop's slow decontamination

* Bioenergetic modelling approach to investigate physiological processes and their links to environmental conditions

* Importance of the size of the individual?

* Comparing pectinid species to understand the differences

* How to model different toxin kinetics?

## Materials & Methods

* **Abj DEB model** for king scallop (Lavaud *et al.*, 2014) and for the variegated scallop (Regnier-Brisson *et al.*, poster)

* Parameters: • from AmP for the king scallop • from a new estimation for the variegated scallop

* **Toxin kinetic module** based on Pousse *et al.*, 2019; contamination of *Crassostrea gigas* by *Alexandrium minutum*, producer of Paralytic Shellfish Toxin (PST)

* **2-compartments model: fast** (egestion, unassimilated toxins) and **slow depuration** (elimination, assimilated toxins)

* Gut retention time: dependent on the organism length and the functional response

* First order kinetic for elimination of assimilated toxins

* **No effect on metabolism** (Liu *et al.*, 2007)

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$$t_g = \frac{V^{1/3} [M_{gm}]}{f \{j_{XAm}\}}$$

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### Environment

* **Temperature and food conditions:** *in situ* monitoring in the Bay of Brest (Regnier-Brisson *et al.*, poster)

* **Toxic food conditions:** from REPHYTOX monitoring, average of several years and locations

* Representation of 3 years, from Fourier parameters

### Sensibility analysis

$$SI(\%) = \frac{1}{n_{days}} \sum \frac{|[DA]_{new\ param} - [DA]_{standard}|}{[DA]_{standard}} 100$$

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## Results

### Dilution by growth

#### Simulations

* 5 adults with different initial shell heights and flesh dry weights

* Same environment, simulations for 3 years

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#### Growth in shell height

* **Higher and longer** length growth for **small individuals**

* Ultimate length around 12.5 cm

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#### Toxin concentration

* At the peak: **higher toxin concentration** for smaller individuals

* **Smaller scallops**

* Faster contamination

* Faster decontamination

* **Bigger scallops**

* Toxin remains for a longer time

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Remark: little increase of the concentration at spawning events (loss of weight)

### Comparison between species

#### Simulations

* DEB parameters for the king scallop, same environment, simulations for 3 years

* 2 individuals – 1 “fast” (variegated scallop-like), 1 “slow” (king scallop-like) depurator

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Slow

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Fast H1

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Fast H2

* 2 hypothesis for faster depuration

* **Hypothesis 1: Lower toxin uptake**

* 50% reduction of the $\kappa_{X_{tox}}$ value

* **Hypothesis 2: Greater toxin elimination**

* 50% increase of the $\dot{k}_{elim}$ value

* Sensitivity analysis (SI) on the toxin concentration for parameters variation of 50%

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#### Toxin concentration

* Lower toxin concentration with **lower** assimilation but similar dynamic

* Faster decrease with **higher elimination**

#### Sensitivity analysis
* The elimination parameter is more sensitive ($SI = 56\%$) than the assimilation parameter (38%)

## Discussion

### Environment

* Need to better define the availability of toxic algae

### Dilution by growth

* Representation of the contamination and decontamination of the toxin as expected

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* The contamination is quick and punctual

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VS

* The decontamination is quick for the first days, then it is very slow, as observed

* Smaller animals accumulate the toxin more rapidly. Thus, they reach a higher toxin concentration

* They depurate faster than the bigger individuals

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* The model will permit to test hypotheses on differences between species for toxin concentration

### Perspectives

* Coupling approaches between modelling, experimentation and *in situ* observations

* Contamination of *P. maximus* by *Pseudo-nitzschia sp.* with a large interval of shell heights

This work was supported by ISblue project, Interdisciplinary graduate school for the blue planet (ANR-17-EURE-0015) and co-funded by a grant from the French government under the program "Investissements d'Avenir" embedded in France 2030.

We would like to acknowledge France Filière Pêche and Brest Metropole for their financial support for the project and thus the PhD thesis. We also would like to acknowledge the Brittany region for their financial support for the PhD thesis.

## References

Pousse, É., Flye-Sainte-Marie, J., Alunno-Bruscia, M., Hégaret, H., Rannou, É., Pecquerie, L., Marques, G. M., Thomas, Y., Castrec, J., Fabioux, C., Long, M., Lassudrie, M., Hermabessiere, L., Amzil, Z., Soudant, P., & Jean, F. (2019). Modelling paralytic shellfish toxins (PST) accumulation in *Crassostrea gigas* by using Dynamic Energy Budgets (DEB). *Journal of Sea Research*, 143, 152-164. https://doi.org/10.1016/j.seares.2018.09.002

Lavaud, R., Flye-Sainte-Marie, J., Jean, F., Emmery, A., Strand, Ø., & Kooijman, S. A. L. M. (2014). Feeding and energetics of the great scallop, *Pecten maximus*, through a DEB model. *Journal of Sea Research*, 94, 5-18. https://doi.org/10.1016/j.seares.2013.10.011

Liu, H., Kelly, M., Campbell, D., Dong, S., Zhu, J., & Wang, S. (2007). Ingestion of domoic acid and its impact on king scallop (*Pecten maximus*, Linnaeus 1758). *Journal of Ocean University of China*, 6, 175-181. https://doi.org/10.1007/s11802-007-0175-6