Improving ecological models for a sustainable development of bivalve culture in eutrophic estuarine complexes

Description

The carrying capacity (number of living organisms that a region can support without environmental degradation) of coastal systems for bivalve culture has typically been investigated using mathematical models restricted to a Nutrient-Phytoplankton-Zooplankton-Detritus-Cultured Bivalve representation. This study aimed to develop a more detailed understanding of nutrient dynamics to accurately gauge the influence exerted by cultured bivalves. The addition of macroalgae, like sea lettuce, in a model may better refine primary production, especially in eutrophic systems. Wild bivalve population modules were also coupled to an existing ecosystem carrying capacity model.

Model development was supported by field and experimental work to characterize distribution, abundance and growth for both macroalgae and wild bivalves. Model application was performed for Malpeque Bay, Prince Edward Island; however, the model was given a generic structure allowing future applications to other coastal embayments (coastlines forming a bay). Adding these new modules increases model veracity and provides new insights into aquaculture-coastal ecosystem interactions, especially in quantifying the influence on species with commercial, recreational and Aboriginal value.

Findings

An ecophysiological model of sea lettuce (Ulva lactuca) was developed during this project to predict the growth of sea lettuce based on environmental conditions (temperature and nutrients) and to account for the role of sea lettuce (nutrient uptake) in the functioning of Malpeque Bay.

The addition of a macroalgae module to the coupled model showed that the development of blooming sea lettuce in Malpeque Bay may reduce cultured mussel growth in length by up to 7%. This reduction can be explained by a decrease in food availability for mussels as phytoplankton, the main food source for bivalves, competes with macroalgae for light and nutrients.

Ecophysiological models of the main wild bivalve species (American oysters and soft-shell clams) inhabiting Malpeque Bay were also developed through this project. Once coupled to the ecosystem model that also included cultured mussels and oysters, the complete modeling tool allowed the assessment of the effects of current and expansion farms on wild stocks as well as interactions between current and expansion farms.

Publications

Lavaud, R., Filgueira, R., Nadeau, A., Steeves, L. and Guyondet, T. (2020). A Dynamic Energy Budget model for the macroalga Ulva lactuca. Ecological Modelling 418. DOI

Lavaud, R., Guyondet, T., Filgueira, R., Tremblay R. and Comeau, L.A. (2020). Modelling bivalve culture - Eutrophication interactions in shallow coastal ecosystems. Marine Pollution Bulletin 157. DOI

Multimedia

Shedding light on the effects of oyster farming

Ocean School:

• North Atlantic\Healthy Habitats\Life in the Balance\The oyster and the eelgrass
• North Atlantic\Healthy Habitats\Life in the Balance\Ulva overload

Program Name

Program for Aquaculture Regulatory Research (PARR)

Years

2015 to 2018

Principal investigator

Thomas Guyondet
Research scientist, Fisheries and Oceans Canada, Gulf Fisheries Centre, Gulf Region
Email: Thomas.Guyondet@dfo-mpo.gc.ca