Artificial habitat and biofouling species distributions in an aquaculture seascape

Abstract

The global proliferation of marine artificial habitats is rapidly altering the physical structure of coastlines, with knock-on effects on physical, chemical, and ecological processes at seascape scales. Ecological consequences of maritime sprawl associated with aquaculture are poorly understood, despite the fact that these suspended structures are particularly prone to biofouling, which can affect the industry and seascape around it. We characterised seascape-scale spatial and temporal distribution patterns of 10 biofouling taxa in relation to the presence and distance to Perna canaliculus mussel farms in New Zealand’s largest aquaculture region. Seven of 10 taxa had significantly higher cover on farms than in natural habitats throughout the region. The cover of 4 of those 7 taxa, including the high-profile pests Mytilus galloprovincialis and Undaria pinnatifida, exponentially decreased with distance from the nearest farm, while some taxa were absent from natural habitats (e.g. the ascidian Ciona robusta). In contrast, several opportunistic macroalgal species, such as Cladophora ruchingeri and Pylaiella littoralis, had colonised extensive areas of natural habitat. Our results suggest that biofouling is a persistent issue on mussel farms and that farm structures may act as reservoirs or ‘stepping stones’ for the dispersal of potential marine pests. These distributional and dispersal patterns can inform integrated pest management efforts focusing on spatial management strategies, such as ‘firebreaks’ in farm connectivity, avoidance of pest hotspots, and farm fallowing.

The loss of seed mussels in longline aquaculture

“…125,126 Consequently, the resulting communities can be dynamic in their structure and function 127 and attain considerable cover and biomass. 128,129 Early colonists in the successional sequence are often microscopic organisms (bacteria and diatoms in biofilms) or propagules of macroscopic taxa (including mussels) that modify the subsequent pattern of settlement and determine community dynamics. 20,123,[130][131][132][133] Mussel seed can experience trickle or pulse settlement of other (biofouling) species or conspecifics, [134][135][136] followed by competition for food and space 128,137,138 and modifications to their local environment, such as reduced dissolved oxygen and water flow, due to gradually increasing fouling biomass.…”

Toward integrated pest management in bivalve aquaculture

“…Regional alignment of management interventions may provide more holistic (and ultimately cost‐beneficial) mitigation of pest populations beyond the boundaries of single farms. A recent study by Atalah et al 15 . began to characterize the distribution and occurrence of pests of mussel aquaculture throughout Marlborough Sounds in New Zealand.…”

“…In jurisdictions with regulations to manage aquaculture biosecurity risks, the presence of nonindigenous pests on farms also can threaten freedom to operate when constraints are placed on movements or other activities to prevent further pest spread. Subsequent spill‐over impacts from pests can extend well beyond bivalve aquaculture because proliferation on farms can lead to subsequent infestation of adjacent or connected natural or modified environments 15 . As such, there is an opportunity to boost bottom lines and improve sustainability by more actively managing pests in bivalve aquaculture.…”

“…Subsequent spill-over impacts from pests can extend well beyond bivalve aquaculture because proliferation on farms can lead to subsequent infestation of adjacent or connected natural or modified environments. 15 As such, there is an opportunity to boost bottom lines and improve sustainability by more actively managing pests in bivalve aquaculture.…”

Managing Biofouling on Submerged Static Artificial Structures in the Marine Environment – Assessment of Current and Emerging Approaches

“…This dichotomy reflects clear economic incentives, which are well-documented for maritime vessels where even 'light' biofouling causes hydrodynamic penalties that can dramatically increase power requirements, fuel usage, and associated emissions (Townsin, 2003, International Maritime Organization [IMO], 2011Schultz et al, 2011). The benefits of preventing biofouling on SSAS are less apparent or longer term, but there is a growing awareness that unmanaged fouling on these structures can also threaten economic, environmental, and socio-cultural values (e.g., Polman et al, 2013;Atalah et al, 2020). Proactive biofouling management of these structures is often context specific or experimental, but there is an emerging array of approaches and tools that could offer viable solutions for broad applicability, scalability, and cost-effectiveness.…”