TY - RPRT
TI - 2024 State of the Science Report - Chapter 3: Marine Renewable Energy: Stressor-Receptor Interactions
AU - Garavelli, L
AU - Hemery, L
AU - Rose, D
AU - Farr, H
AU - Whiting, J
AU - Copping, A
AB - Chapter 3 encompasses the progress made on understanding the major stressor-receptor interactions that help delineate potential risks from MRE development. Each interaction has been the focus of multiple research and monitoring studies since the 2020 State of the Science report.COLLISION RISK FOR MARINE ANIMALS AROUND TURBINESUncertainty around collision risk of marine animals with turbine blades continues to be a key barrier to consenting new tidal and riverine energy projects. The steps that could result in a marine animal colliding with a rotating turbine blade have been parsed into a series of actions that must take place sequentially. There are differing terminologies and thoughts on each step, but generally the animal must be in the vicinity of a turbine for a potential encounter to occur, and determine whether to avoid the turbine by swimming in the opposite direction, above, below, or around the turbine. If the animal progresses closer to the turbine, there is still an opportunity for it to evade, or take last minute action, to move away from the rotating blades. If these actions fail, a collision may occur. Additional research studies have added evidence to the likelihood that marine mammals may detect the turbine, and avoid the rotor swept areas when the tidal currents increase and the blades begin to rotate. Increasing use of underwater video to examine marine animal interactions with turbines is adding to our understanding of the risk of collision. Research has shown that adult salmon in a river are not likely to be close enough to rotating riverine turbine blades to collide. However, salmon smolts are more likely to pass through the rotor swept area and become disoriented, although longer-lasting harm has not been shown. Diving seabirds have not been observed near rotating turbines but appear to gather in areas where turbines might be installed. The accuracy and validation of numerical models simulating collisions have improved, particularly with the addition of agent-based models that depict single fish, as well as the more traditional collision risk and encounter risk models that examine marine mammals and fish. The low number of deployments and the challenges of collecting nearfield data limit our understanding of collision risk. There is a need for additional data collection and research studies before collision risk can be considered for retirement.RISKS TO MARINE ANIMALS FROM UNDERWATER NOISE GENERATED BY MARINE RENEWABLE ENERGY DEVICESThe potential risk to marine animal behavior from underwater noise continues to be of concern to stakeholders and regulators for both turbines and wave energy converters (WECs). Measurements of acoustic output from MRE devices have become an important aspect of monitoring around deployed devices. The international specification developed by the International Electrochemical Commission Technical Committee 114 (TC114) provides guidance on how to accurately measure noise from an MRE device; the specification has been tested and appears to be headed toward adoption as a standard, following updates. This will provide much needed comparability among underwater noise measurements. Coupled with the US standards and guidance for levels of underwater noise that will disturb or harm marine mammals and fish, the outcome of monitoring to date from turbines and WECs suggests that the operational noise is not likely to be harmful for marine species, at least for small numbers of devices. New frameworks for examining and measuring underwater noise, and new modeling approaches provide further confidence that this stressor is unlikely to be a significant risk for marine animals, for small developments. This risk is considered to be retired for these conditions.ELECTROMAGNETIC FIELD EFFECTS FROM POWER CABLES AND MARINE RENEWABLE ENERGY DEVICESThere have been relatively few field studies of potential electromagnetic field (EMF) effects on marine animals in the past four years, although new methods for detection in the field and laboratory studies have continued. Laboratory studies have challenged many EMF-sensitive marine species with levels of EMFs that are higher than those found from MRE export cables. The marine animals most likely to be susceptible to EMF effects, including certain species of sharks, rays, skates, as well as benthic crustaceans like crab and lobster, have been the focus of most investigations. While the specific biology, physiology, and life stage of many species may show differing levels of sensitivity, for the level of power carried by export cables from MRE devices, the EMFs signatures are generally believed to be below a significant risk level. This has led to the understanding that this risk is considered to be retired for small numbers of devices.CHANGES IN BENTHIC AND PELAGIC HABITATS CAUSED BY MARINE RENEWABLE ENERGY DEVICESChanges in benthic and pelagic habitats are inevitable with any development in the marine environment. However, the small footprint of MRE anchors, foundations, mooring lines, cables, and surface floats from small numbers of devices are not likely to cause significant harm to the marine environment, provided they are sited carefully. Many studies related to changes in habitats have been undertaken in the past four years, including those focusing on understanding marine animal distributions and habitat use pre- and post-installation of MRE devices, as well as characterizing the composition of biofouling and artificial reef assemblages. The lack of evidence of harm to benthic and pelagic habitats has led the risk from this stressor-receptor interaction to be considered as retired for small number of devices.CHANGES IN OCEANOGRAPHIC SYSTEMS ASSOCIATED WITH MARINE RENEWABLE ENERGY DEVICESChanges in wave heights, water circulation, and water column stability as a result of the operation of MRE devices continue to be investigated using numerical models, with some attempts to validate the models with field data collection. These field studies have not yielded results because the changes that could be attributed to small numbers of MRE devices appear to be less than the natural variability of the system. Until large arrays are deployed, it is likely that numerical models will continue to provide the best insights into potential risks to oceanographic systems. For small numbers of devices, the risk is considered to be retired. With OTEC under consideration for tropical waters, the risk from the discharge of large volumes of cold water to the upper water column and the marine animals and plants that live there must be considered. With few operational OTEC plants in the world, there is limited evidence of the magnitude of the risk. The risk will be mitigated by designing the cold water discharge to place the return water below the thermocline for all OTEC developments.ENTANGLEMENT RISK WITH MARINE RENEWABLE ENERGY MOORING LINES AND UNDERWATER CABLESThe risk of large marine animals becoming entangled among mooring lines or draped cables between MRE devices remains theoretical. There is no evidence to date that entanglement will occur; however, stakeholder concerns remain. The advent of floating offshore wind platforms has raised this issue in recent years. While nothing definitive can be said about this risk, for small numbers of MRE devices, it should be considered not to be significant. As larger arrays are deployed, monitoring results from floating offshore wind farms and MRE arrays may provide further insight into the potential risk. This chapter summarizes what little can be determined from available information.DISPLACEMENT OF ANIMALS FROM MARINE RENEWABLE ENERGY DEVELOPMENTOnce larger MRE arrays are deployed, migratory marine species and those that move across short distances in the water column or on the seafloor may have their normal movement patterns disrupted by the presence and operation of the devices. Displacement is defined as the outcome of attraction, avoidance, or exclusion that may be triggered by animal responses to one or more stressors, with potential consequences at the individual to the population levels. This risk is considered to be low at this time, with models used to determine the likely risk dependent on location and populations, however little data to inform this risk will be gathered until larger arrays are deployed. This chapter lays out a framework and recommendations for addressing displacement as the MRE industry grows, including knowledge gaps that remain to be filled.  The 2024 State of the Science Report consists of 11 chapters which can be downloaded as a whole or individually. Download Chapter 3: Marine Renewable Energy: Stressor-Receptor Interactions here.
DA - 2024/09//
PY - 2024
PB - Pacific Northwest National Laboratory (PNNL)
LA - English
KW - Marine Energy
KW - OTEC
KW - Tidal
KW - Wave
KW - Changes in Flow
KW - Collision
KW - Displacement
KW - EMF
KW - Entanglement
KW - Habitat Change
KW - Noise
KW - Birds
KW - Ecosystem Processes
KW - Fish
KW - Invertebrates
KW - Marine Mammals
KW - Physical Environment
KW - Reptiles
ER -