Influence of man-made structures in the ecosystem

2015-2017 Research Projects

“Assessing the Ecological Connectivity between man-made structures in the North Sea (EcoConnect)”

Organisation: Centre for Environment Fisheries and Aquaculture Science, Lowestoft, UK (CEFAS)
Principal Investigator: Dr Kieran Hyder

Man-made structures including rigs, pipelines, cables, renewable energy devices, and shipwrecks, offer hard substrate in the largely soft-sediment environment of the North Sea. These structures become colonised by sedentary organisms and non-migratory reef fish and form local ecosystems that attract larger predators including seals, birds and fish. It is possible that these structures form a system of interconnected hard substrate through three mechanisms:

  1. the ‘planktonic dispersal’ of the pelagic stages of organisms between the structures by ocean currents;
  2. ‘movement’ of mobile organisms.
  3. Changes to the overall arrangement of hard substrate areas through removal or addition of individual man-made structures which will affect the interconnectivity and could impact on the ecosystem.

In this project, network analysis will be used to assess if a network of hard substrate exists and the extent to which man-made structures in the North Sea contribute to an interconnected system of hard substrate. Connectivity will be assessed using models that simulate the drift of planktonic stages and using existing knowledge of mobile organisms. The effect of changes to man-made structures will be assessed for native and non-native species, different ages of structures, and relationships with both natural habitats and Marine Protected Areas will be investigated. The impact of removal of oil and gas infrastructure will then be assessed using network analysis and compared to existing man-made structures and natural substrate.

“Investigating food web effects due to man-made structures using Coupled Spatial Modelling (COSM)”

Organisation: Centre for Environment Fisheries and Aquaculture Science, Lowestoft, Suffolk, UK (CEFAS)
Principal Investigator: Dr Christopher Lynam

Is there an influence of man-made structures on ecosystem structure and functioning at the scale of the North Sea?

COSM will address this question by developing a spatio-temporally dynamic model of the food web coupled directly with a Geographic Information System (GIS). In this way, spatial information on habitat type (substrates and bathymetry), environment (temperature, salinity, stratification, primary production) and pressure data (fishing) will be used to model the distribution of benthic and pelagic ecosystem components from infauna to seabirds.

Consumption of prey (e.g. benthic fauna) by functional groups (e.g. benthivorous fish) will be modelled in relation to their habitats and the subsequent flow of this mass through the system to higher predators (i.e. piscivorous fish, mammals and seabirds) will be examined. The foundation for this will be a published calibrated model, quality controlled in accordance with guidance by the International Council for the Exploration of the Sea. The resolution of the model will be tailored to the finest scale possible that is appropriate based on the resolution of data and the scenarios required to address specific questions.

Man-made structures will be considered in terms of additional habitat for benthic fauna and thus additional foraging areas for predators and as potential corridors and stepping stones linking biological assemblages.

Once calibrated using the available data, the model will be used to predict the effect of including or excluding man-made structures in terms of the consumption and biomass of predatory groups. The natural variability of the ecosystem will be characterised to contrast any effect of man-made structures by driving the model with a series of maps of environmental variables and primary production. Any effect of man-made structures would then be compared to the effect of other pressures (e.g. fishing) in order to put this on context.

The study will generate hypotheses and identify what potential data gaps are necessary to fill in order to improve our understanding and prediction of the dynamics of the North Sea ecosystem and its sensitivity to pressure. As an ‘experimental tank’ the model will help serve to make available mutually compatible data on the ecosystem, while at the same time expose weaknesses and uncertainties in data and knowledge necessary to address in future. Additional data collection in the next stages of INSITE would allow for further model validation and improvement, particularly in relation to habitat dependencies and movement patterns of fauna. COSM will develop and publish applied modelling tools that will benefit the scientific community and improve our knowledge of those food web interactions that are fundamental to ecosystem functioning.

“Reef effects of structures in the North Sea: Islands or connections? (RECON)”

Organisation: IMARES, Texel, Netherlands
Principal Investigator: Prof. Dr. Han Lindeboom

The aim of this study is to investigate and model the species distribution and inter-connectivity of reef communities on offshore structures in the North Sea using different techniques. First, it provides community data from taxonomic species inventories. Second, a cost efficient method for inventory of communities is developed using state-of-the-art DNA metabarcoding. Third, the genetic population structures of the mussel Mytilus edulis and crustacean Jassa Herdmani, abundant invertebrates with different dispersal strategies, are analysed. Ultimately, the data from this study and other available data are used to model the distribution of species on offshore structures and their inter-connectedness. The methodology is proposed to address three main questions:

  1. What is the species composition of marine growth on offshore structures?
  2. To what extent is this composition explained by abiotic factors (e.g. depth, temperature, location, platforms age, marine growth cleaning frequency, et cetera) and biotic factors (e.g. food availability, proximity to marine growth on other offshore structures, distance to coastal populations, et cetera)?
  3. To what extent are the communities on the structures isolated from or connected to each other and how is this explained by the factors noted earlier?

In addition to analysing existing footage collected with remotely operated vehicles, we carry out fieldwork in a highly cost efficient manner, using fully equipped mobilized diving-vessels already present at offshore installations for regular inspection and maintenance work. GDF-SUEZ provides in-kind co-funding by allowing our certified offshore diver-marine biologists to access their dive support vessels. This approach was implemented frequently by IMARES in 2014 and is a highly successful, unique and cost-efficient method for field inventories of reef communities on offshore installations. Part of the work is financed with cooperation and co-funding from several companies.

“Measuring the shadow of artificial structures in the North Sea and its effect on the surrounding soft bottom community”

Organisation: Netherlands Institute for Sea Research (NIOZ), Texel, The Netherlands
Principal Investigator: Prof dr Gert-Jan Reichart

Artificial structures in the North Sea offer hard substrate to a rich and diverse epifauna in an area covered by soft sediments. The biomass of epifauna, of which a high proportion are filter feeders, is estimated to be up to 500-fold the biomass found on a similar surface of soft sediment. On this basis we hypothesize that the epifauna on artificial structures act as biofilter, depleting primary organic matter in the water column and enriching it by producing faeces, nutrients, dissolved organics and larvae. Hereby the environmental conditions and particle fluxes are altered in the wake of an artificial structure, which will casts a so-called “shadow” which will also affect the soft sediment ecosystem near that structure. In addition, we hypothesize that artificial structures act as stepping stones, enhancing biodiversity in the North Sea. Larvae produced by the epifauna will contribute to the persistence of rare and endangered species in the heavily-trawled North Sea.

To test our hypothesis we will

  1. measure concentrations and fluxes of particles and solutes around a platform in a shallow and deep water setting in the North Sea
  2. measure impacts on the surrounding soft bottom community;
  3. model the shadow effect, and d) identify and quantify the production of larvae.

These goals will be accomplished by a combination of field studies including long and short-term deployments of moorings with particle traps and laboratory analysis of water, sediment and fauna samples. The study will provide independent scientific data to assess the present day role of artificial structures in the North Sea in maintaining and improving biodiversity, and its potential to influence the overall ecosystem status of this sea.

“Appraisal of Network Connectivity between North Sea subsea oil and gas platforms” ANChor”

Organisation: University of Edinburgh, School of GeoScience, Edinburgh, UK
Principal Investigator: Dr. Lea-Anne Henry

Installations of oil and gas platforms across the North Sea have introduced substantial amounts of hard substrate to the seafloor. These structures promote dense growth of hard-bottom marine organisms: algae, mussels, tube-building worms, hydroids, anemones and reef-building corals all colonise these platforms from the top of the platform jacket down to the footings resting at the depths of the seafloor. Platforms have been thought to function as “artificial reefs” in the North Sea for decades. However, the magnitude of effects these man-made structures have had in creating a larger inter-connected hard substrate reef system is not known, but current tests of this concept suggest connectivity varies across North Sea regions.

As the North Sea enters the decommissioning era, we also do not understand how platform removal will affect the overall structure and functioning of North Sea ecosystems. The ANChor project, “Appraisal of Network Connectivity between North Sea subsea oil and gas platforms”, adopts an innovative approach to appraise connectivity of today’s mature North Sea platform network and its sensitivity to re-configuration. For INSITE’s Foundation Phase, we will use industry marine growth surveys and cutting-edge computer simulations of high-resolution coastal ocean conditions and dynamics to estimate dispersal potential of common rig species between “donor” and all potential “recipient” platforms. Species’ depth on the platform and propagule properties (mode, timing of release, and duration) will be key input for these simulations.

Using a graph theoretic approach allows visualising and mapping the North Sea network, with the “graph” formed by platform “nodes” connected to each other by “edges” that vary in strength according to the number of connections each platform potentially makes either as a donor or recipient of propagules. Effects of decommissioning on network connectivity will be simulated by removing the strongest donor platform nodes to assess changes in overall network connectivity and thus determine how strongly the integrity of North Sea ecosystem connectivity depends on these man-made structures.

“Influence of Man-Made Structures in the ecosystem: is there a planktonic signal?”

Organisation: Sir Alister Hardy Foundation for Ocean Science (SAHFOS), Plymouth, UK
Principal Investigator: Professor Willie Wilson

In the North Sea the presence of man-made structures (MMS), such as oil platforms, has greatly expanded. This research project will examine whether there has been an impact on the abundance, distribution and seasonal timing of the plankton community in the Greater North Sea. Plankton lie at the base of the marine food web and as such they initiate and sustain all marine ecosystems - many commercially important organisms such as fish are dependent upon them.

The plankton community is made up of both plant (phyto) plankton and animal (zoo) plankton, some of which spend their entire life cycle in the plankton community (holoplankton). The remainder only spend a short part of their life as plankton, these are known as meroplankton, and examples of these are crabs, lobster, barnacles and starfish. As plankton generally grow and reproduce at a rapid rate, their high population turnover can be useful when looking at impacts on the community as a whole. For example, plankton are known to respond rapidly to climate change.

This study will use data from the Continuous Plankton Recorder Survey, run by the Sir Alister Hardy Foundation for Ocean Science (SAHFOS), based in Plymouth. SAHFOS has an archive of plankton abundance covering the entire North Sea (and beyond) extending back many decades, and will use information from almost 63,000 samples collected from the study area. The research will focus on trying to identify whether MMS have had an impact on the plankton community, and will use statistical methods to remove environmental signals from plankton time series, and compare this from areas where MMS are absent.

“UNDerstanding the INfluence of man-made structures on the Ecosystem functions of the North Sea (UNDINE)”

Organisation: Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine Research, Germany
Principal Investigator: Dr Jennifer Dannheim

Abstract: Offshore man-made structures are rapidly expanding in the North Sea. Whereas artificial structures such as oil and gas rigs and ship wrecks have long been present, this expansion is nowadays mainly due to the construction of offshore wind farms. The introduced hard substrates host a fauna that is fundamentally different from the naturally occurring soft sediments that dominate the North Sea ecosystem. These offshore structures hence induce changes in biodiversity and ecosystem functions. Knowledge on the magnitude of these effects is indispensable to assess the impact at the ecosystem level, but is currently lacking.

UNDINE will evaluate (i) the ecological impact of man-made structures on trophic functioning and (ii) potential changes in connectivity by man-made structures using dispersion models validated by genetic population structure. Trophic functioning and connectivity are considered key issues as man-made structures start proliferating in the marine environment. They necessitate the extrapolation of artificial hard substrate effects from local to regional scales, all of which will be tackled by UNDINE. This research will synthesize and integrate state of the art knowledge to understand ecosystem structure and functioning. This will be useful for a sustainable management of North Sea ecosystems, especially in relation to hard substrate habitats. Additionally, UNDINE will identify knowledge gaps and provide scientific recommendations for future research priorities.

UNDINE will use offshore wind farms and data from other man-made structures in order to understand the ecological impact of man-made structures. Particularly, the high amount of high-quality data from offshore wind farms monitoring programmes will be of use here. UNDINE’s approach of combining different datasets will ensure its outcomes to be transferable to a more generic man-made structure effect context.

“Man-made structures and Apex Predators: Spatial interactions and overlap (MAPS)”

Organisation: Sea Mammal Research Unit (SMRU), Scottish Oceans Institute, University of St Andrews, UK
Principal Investigator: Dr Deborah Russell

The effect of man-man structures on the marine ecosystem is likely to depend on the type and status of the structure. Commissioning and decommissioning of structures can cause disturbance and displacement of marine mammals. Established structures may also result in displacement due to operational noise, presence of maintenance vessels or habitat destruction. However, such structures may provide refuge for predators or their prey due to access and fishing restrictions within their vicinity. Furthermore, such structures can host artificial reefs and may present foraging opportunities for some predators, for example in a recent paper (Russell et al., 2014) the applicants demonstrated that some seals use such structures for foraging. How either deterrence or attraction to these structures may affect the marine environment is still poorly understood.

We will map the distributions of top predators in the North Sea, including seabirds, seals and cetaceans, and quantify overlap with man-made structures. We will examine how the distributions of apex predators are influenced by proximity to man-made structures, while considering other temporal and spatial variation in their environment (e.g. habitat, depth, temperature). This will provide information on the current effect of man-made structures on the distribution of key apex predators and also on the proportion of the population of each species which could be potentially impacted by disturbance resulting from commissioning and decommissioning.

For finer spatial scale analyses, we will use data from animal-borne devices which record and transmit locational and in some cases behavioural data on harbour and grey seals (minimum sample size of 282) and five species of seabird (n=700). These data will allow us to quantify the encounter rate with man-made structures and also the proportion of encounters that result in the use of structures for foraging. We will investigate how the results vary among individuals, species, structure type and age. Along with the overlap between species and man-made structures, this will allow us to report on the extent to which manmade structures may influence foraging behaviour at a population level. Our results will inform the review of OSPAR Decision 98/3 and any commissioning and decommissioning processes to reduce any negative impact on the ecosystem.

A data initiative which will provide useful data as the research progresses is also being undertaken to create another source of material from industry and to identify the best way to manage data generated through INSITE projects.