Spatial connectivity and marine disease dispersal: missing links in aquaculture carrying capacity debates

Abstract One major societal challenge is meeting the constantly increasing demand for (sea)food in a sustainable way. With marine aquaculture on the rise, it is crucial to define limits to aquaculture growth in order to ensure ocean health. Along these lines, the concept of aquaculture carrying capacity (CC) is increasingly intersected with the principles of the ecosystem approach to aquaculture. Its primary aims are to estimate sustainable production potential and limits of locally defined regions. However, the ocean is a fluid environment, subject to large- and small-scale dynamics, including ocean currents, tidal fluctuations, and human action. These dynamics introduce spatial connectivity between aquaculture sites and more distant ecosystems than considered in current CC estimates. We argue that far-reaching effects of aquaculture on the ocean, such as introduction and spread of invasive species and marine diseases, are thus underestimated when providing recommendations. Marine diseases can impact biodiversity, society, and overall ocean health and it is imperative to guide aquaculture development to reduce the risk of marine disease dispersal. We, therefore, suggest to embrace spatial ocean connectivity into the CC concept by using hydrodynamic modelling and dispersal simulations as high-throughput methods to estimate potential impact areas and provide risk assessments. In this work, we focus on the example of dispersing infectious diseases in bivalve farming and discuss ecological as well as social consequences of spatial connectivity. Both are applicable to a wide range of organisms and marine aquaculture systems internationally. Summary The concept of aquaculture carrying capacity (CC) aims at defining sustainable limits to aquaculture growth in order to ensure ocean health. Usually, estimations are based on locally defined regions and on the farm-scale. However, interactions of aquaculture with the ocean can have far-reaching effects, such as introduction and spread of invasive species and marine diseases. The ocean is a fluid environment, subject to large- and small-scale dynamics that introduce spatial connectivity between aquaculture sites and more distant ecosystems than considered in current CC estimates. We, therefore, suggest to embrace spatial ocean connectivity into the CC concept by using hydrodynamic modelling and dispersal simulations as high-throughput methods to estimate potential impact areas and provide risk assessments. Here, we focus on the example of dispersing infectious diseases in bivalve farming and discuss ecological as well as social consequences of spatial connectivity. Both are applicable to a wide range of organisms and marine aquaculture systems internationally.