Benthic and Fish Interactions With Pipeline Protective Structures in the North Sea

Abstract

An increasing number of pipelines and associated protective materials in the North Sea are reaching the end of their operational life and require decommissioning. Identifying the optimal decommissioning option from an environmental perspective requires an understanding of ecological interactions; currently there is little knowledge as to species associations with pipelines and associated protective materials. This study utilises industry ROV footage from the North Sea to quantify these interactions. A total of 58 taxa were identified, including 41 benthic taxa and 17 fish taxa. Taxa were grouped into seven groups for analysis including four groups for benthic epifauna: grazers, suspension/filter feeders, decapods, and colonial/encrusting taxa. Fish were organised into three groups: pollock, other fish, and other gadoids. Using zero-inflated generalised linear mixed models, we show that abundances of benthic epifauna and fish vary between types of protective structure (e.g., concrete mattresses, rock dump), depth, levels of fishing effort and proximity to oil and gas platforms. Six taxa groups exhibited higher abundances on concrete mattresses than bare pipelines with benthic epifaunal decapods showing the highest difference at 3.04 (1.83, 4.84, 95% CrI) times higher on mattresses compared to bare pipelines. Six groups were higher in abundance within the 500 m fisheries exclusion zone around platforms, compared to outside of the zone, with other gadoids showing the highest difference at 1.83 times (1.09, 2.89, 95% CrI) times higher inside zones. Five groups decreased in abundance with an increase in fishing effort, with the biggest effect observed on grazers which decreased in abundance by 28% (14 – 40, 95% CrI) per 50 h of fishing. We show that pipelines and protective materials are operating as artificial reefs, and our results suggest that removal of infrastructure could result in the loss of habitat and species.

Habitat value of subsea wells and pipelines for fishery target species in Australia

“…pipeline spans have been reported previously in the NW (McLean et al, 2017;Bond et al, 2018a;Schramm et al, 2021) and the North Sea (Redford et al, 2021). This pattern may also reflect known associations of this species with rocky habitat during the adult phase and soft habitat in the juvenile phase (Seiler et al, 2012).…”

Context-Based and Image-Based Subsea Pipeline Degradation Monitoring

“…Various attempts have been made to determine the positive and negative effects of pollution and corrosion from offshore structures on the behavioral patterns of opportunistic species [10][11][12][13][14][15]. The mutual impacts of opportunistic organisms and subsea anthropogenic structures, such as offshore oil platforms, can be summarized in two focus areas:…”

Influence of offshore oil and gas structures on seascape ecological connectivity

“…Barriers to movement may decrease or modify physical connectivity in a system, and movement connectivity within species distributions. Although no studies have focused on the effect of pipelines on movement and habitat connectivity for mobile invertebrates, mobile invertebrate species use features of pipelines such as free-spans, field joins, protective mattresses, scour support structures and the benthic sessile communities that colonise pipelines (Glaholt, 2008;Lacey & Hayes, 2020;McLean et al, 2020;Redford et al, 2021;Rouse et al, 2019). O&G structures appear to provide feeding opportunities (Arnould et al, 2015;Robinson et al, 2013;Russell et al, 2014) and facilitate dispersal of protected species (Henry et al, 2018).…”