environmental and ecological effects of ocean renewable energy

8/10/2019 Environmental and Ecological Effects of Ocean Renewable Energy

1/14Oceanography Vol.23, No.268

ENVIRONMEN AL ANDECOLOGICAL EFFECOF OCEAN RENEWABLE

ENERGY DEVELOPMEA Current Synthesis

B Y G E O R G E W. B O E H L E R A N D A N D R E W B . G I L L

M A R I N E R E N E WA B L E E N E R G Y | I N A R E G U L A O RY E N V I R O N M E N

IN RODUC IONRenewable energy resources may repre-sent one o humankinds best hopes orreducing our substantial contributionto global warming (Krupp and Horn,2008). echnology to capture the energy

rom wind, the sun, and biomass areall in various stages o development. Inmany areas o the world, marine renew-able energy has great promise but manyo the approaches remain to be devel-oped to commercial standards. Energy

rom marine wind, tides, currents,waves, and thermal gradients may allhold immense potential or electricalenergy generation. Te development othe technology, however, is not withoutenvironmental and social concerns(Pelc and Fujita, 2002; Gill, 2005; Cadaet al., 2007; Boehlert et al., 2008; Inger

ABS RAC .Marine renewable energy promises to assist in the effort to reducecarbon emissions worldwide. As with any large-scale development in the marineenvironment, however, it comes with uncertainty about potential environmentalimpacts, most o which have not been adequately evaluatedin part because many othe devices have yet to be deployed and tested. We review the nature o environmentaland, more specically, ecological effects o the development o diverse types o marinerenewable energycovering marine wind, wave, tidal, ocean current, and thermalgradientand discuss the current state o knowledge or uncertainty on how theseeffects may be mani ested. Many o the projected effects are common with other typeso development in the marine environment; or example, additional structures lead toconcerns or entanglement, habitat change, and community change. Other effects arerelatively unique to marine energy conversion, and specic to the type o energy beingharnessed, the individual device type, or the reduction in energy in marine systems.While many potential impacts are unavoidable but measurable, we would argue itis possible (and necessary) to minimize others through care ul device developmentand site selection; the scale o development, however, will lead to cumulative effectsthat we must understand to avoid environmental impacts. Renewable energydevelopers, regulators, scientists, engineers, and ocean stakeholders must worktogether to achieve the common dual objectives o clean renewable energy and ahealthy marine environment.


2/14Oceanography June 2010 69

et al., 2009). Many countries require acomprehensive examination o potential

environmental effects (e.g., or waveenergy: Wilson and Downie, 2003; FaberMaunsell and ME OC PLC, 2007; and

or offshore wind: MMS, 2008). Tedevelopment o various rameworksto evaluate environmental effects isunderway (e.g., EquiMAR, http://www.equimar.org; Simas et al., 2009). In theUnited States, the Minerals ManagementService (Michel et al., 2007) and

Department o Energy (DOE, 2009) haveinstituted similar efforts. In this article,we briey review the potential environ-mental effects o development o marinerenewable energy on a worldwide basis.

Te consideration o environmentaleffects is complex; the multiplicity otechnologies (Bedard et al., 2010), oceanareas, and ecosystems likely or develop-ment o marine renewable energy makea comprehensive treatment impossiblein a single short article. In keeping withthe goals o this volume, the scope othe present article will be limited towind, wave, tidal, current, and thermalgradient approaches in ocean renew-able energy development (re erred toherein as ORED, adapted rom Gill,2005). We ocus on providing exampleso environmental effects that are either

well documented or, where uncertaintyis high, on providing appropriate sources

o re erence where pertinent. Effects arediscussed in the context o a rameworkthat crosses technology types.

A FRAMEWORK FOR EVALUA INGENVIRONMEN AL EFFEC STe description o environmental effectso marine renewable energy can benet

rom a classication o those effectswithin a ramework. In this paper, wediscuss potential impacts cutting acrosstechnology types through the construc-tion, operation, and decommissioningstages as well as across spatial andtemporal scales. We use a classicationand ramework modied rom that used

or wave energy by McMurray (2008)and place the effects o marine renewableenergy development in the context oecological risk assessment by consideringstressors and receptors. Stressors are eatures o the envi-

ronment that may change withimplementation o renewable energyduring installation, operation, or

decommissioning o acilities. Receptors are ecosystem elements

with potential or some orm oresponse to the stressor.

Te stressors and receptors rom thatramework applied to wave energy have

been modied to account or the broaderapproach o this synthesis. Our ocus ison the unique eatures o ORED and itsinteraction with the environment, and,

or that reason, we only deal with issueso installation, operation, and decommis-sioning as they differ rom other marineconstruction projects and activities.

S RESSORSScale of StressAny stresses related to ORED need tobe considered in terms o the stage odevelopment (i.e., survey, construction,operation, and decommission; sensu Gill, 2005), and the spatial and temporalextent o the stress, particularly itsduration, requency, and intensity. Forany single development, the scale is a

George W. Boehlert ([email protected]) is Professor of Marine

Fisheries, Hat eld Marine Science Center,Oregon State University, Newport, OR,

USA.Andrew B. Gill is Senior Lecturerin Aquatic Ecology, Natural Resources

Department, School of Applied Sciences,Cran eld University, Bedfordshire, UK.

RENEWABLE ENERGY DEVELOPERS, REGU

SCIEN IS S, ENGINEERS, AND OCEAN S AKEH

MUS WORK OGE HER O ACHIEVE HE COMDUAL OBJEC IVES OF CLEAN RENEWABLE

AND A HEAL HY MARINE ENVIRONMEN



potential major actor as small develop-ments may have very localized effects,which consequently may be consideredminor or even negligible (such as singledevices used in testing). Effects o a

large, commercially operating energydevelopment will be at a signicantlygreater scale (e.g., large wind arm arraysin northern European waters will occupyseveral hundred square kilometers othe coastal environment). Furthermore,plans or multiple developments in

adjacent waters are likely to need an evengreater scale o consideration. Tey willoccupy more o the coastal environment,and the survey and construction phase odevelopment will likely extend the dura-

tion and requency o stressors in the vicinity. Hence, the cumulative effect oa number o developments could resultin a different set or scale o effects thatwill ultimately require a different scaleor set o management actions (Masdenet al., 2010). Given the importance o the

spatial and temporal scale in evaluatingeffects and impacts, we suggest that they

orm the basis o any consideration ostressors relating to ORED.

When assessing the environmental

implications o offshore renewableenergy, it is important to ollow anappropriate sequence o questioning.Figure 1 outlines such a sequence, whichsets out the relationship between theOREDs and the apparent stressors andreceptors that have been considered

Marine Renewable Energy ( Level 1 )Wind Wave Near Shore Tidal Ocean Current Ocean Thermal

Physical Presenceof Devices

Dynamic Effectsof Devices

Energy RemovalEffects Chemical Acoustic

ElectromagneticFields

PhysicalEnvironment PelagicHabitat Fish andFisheriesBenthic Habitatand Species MarineBirds MarineMammals Ecosystem andFood Chain

Single/Short Term Single/Long Term Multiple/Short Term Multiple/Long Term

Population Change Community Change Biotic Process Alteration

Spatial Temporal Other Human Activities

Physical Structure/Process Alteration

Environmental Stressors ( Level 2 )

Environmental Receptors ( Level 3 )

Environmental Effect ( Level 4 )

Environmental Impact ( Level 5 )

Cumulative Impact ( Level 6 )

Figure 1. Framework for the consideration of environmental effects of marine renewable energy encompassing different scales. Each ORED will haveassociated stressors that affect different receptors. Effects vary across scales and receptors; if the effects are sufficient to have impacts, those impactscan apply across different levels from population through biological and physical processes. Cumulative impacts must be considered as an additionaldimension to the impacts and should consider stressors from other human impacts.



through studies and the literature. Notethat identi ying the stressor(s) then leadsto a set o receptors that may or may notshow the effect(s) o the stress(es). Teremay be single or multiple stressors and

single or multiple receptors; resultanteffects may be short term (e.g., duringconstruction or decommissioning)or long term (during the operationalphase). Tis will have consequences orthe scale o the effect and any cascadingeffects that are central to understandingthe ecological context.

Effect or Impact?

When discussing stressors in environ-mental systems, an important semanticdistinction should be made between aneffect o a stressor (Level 4 in Figure 1)on a receptor and an impact (Level 5).Te two terms are ofen used inter-changeably, but effect does not indicatea magnitude or signicance, whereasimpact implicitly deals with severity,intensity, or duration o the effect.Furthermore, impact also deals withdirection o effect, which means therecan be positive or negative outcomes tothe effect o the stressor. Te distinctionbetween effect and impact is o crucialimportance when considering ORED; anumber o studies present ndings thatsuggest or show an effect, but urtherwork is usually required or it to beinterpreted as an impact. In terms oFigure 1, the current state o knowledgeis at Level 4 rather than Level 5.

In order to move rom Level 4 to 5 inFigure 1, there needs to be evidence thatthe effect o the stressor is signicantenough to cause change that will bemani ested either within a species popu-lation or community o species. Suchimpacts can occur either through direct

pathways or through more indirectchanges to biotic or physical processes.I there are no discernible changes topopulations or communities, then it isalso necessary to consider whether there

may be signicant alterations to ecolog-ical processes, such as trophic cascade,altered primary production, or nutrientenrichment. Such indirect effects aremore difficult to determine but shouldbe considered when determiningimpacts, particularly over longer periodso time or when cumulative effects oother OREDs are being incorporated(see Figure 1).

Physical Presence of DevicesTe mere physical presence o newstructures in marine ecosystems resultsin undamental changes to the habitat,both above and below the water sur ace.Above the water sur ace, seabird andmigratory bird impacts are o greatestconcern. Marine wind energy deviceswill have the greatest vertical proleand the most moving parts and poten-tial effects; these effects have beenaddressed in several studies (Larsen andGuillemette, 2007; MMS 2008). Waveenergy devices have differing prolesabove water, leading to lower potential

or seabird collisions, but this hazardremains to be evaluated.

At the sea sur ace, some wavedevices (e.g., Pelamis, Sea Dragon)may take up signicant areas that mayneed to be considered or migratorysur ace dwellers in terms o a physicalbarrier. Furthermore, shoreline andestuarine devices may represent largeimmovable and impassable objects

or migratory species and mustbe designed appropriately.

Below water, devices will include

buoys, rotors or other moving struc-tures (ocean current and tidal), cablingsystems, hard-xed structures (suchas monopoles or jackets), rock scourprotection, anchors, electrical cables, or

pressurized pipes. In the case o land-based ocean thermal energy conversion(O EC), large pipes will extend alongthe ocean bottom to signicant depths.Tese new hard sur aces will alterbottom communities; or wave energyin particular, most oscillating deviceswill be deployed in eatureless sandysedimentary habitats. Te physicalstructures will result in settlement

habitat or different organisms, creatingan articial ree effect as has been thecase or offshore oil and gas plat ormsand offshore wind arms in Europe (seebenthic habitat receptor discussion).In midwater, i no anti- ouling is used,the new structure will provide settle-ment habitat and likely attract pelagicorganisms, the principle that makes shaggregation devices effective (Dempsterand aquet, 2004).

Dynamic Effects of DevicesMoving parts o marine renewabledevices can lead to blade strike, typi-cally viewed as a problem with migratorybirds and wind energy devices. In-waterturbines, such as current or tidal energydevices, generally move at slower speedsand thus the likelihood o blade strikeis lower. However, the speed o the tipo some horizontal axis rotors couldbe an issue or cetacean, sh, or divingbird strikes (Wilson et al., 2007), and

urther analysis is merited. An additionalconsideration is that the energy with-drawn rom air, water, or waves may alsohave potential effects in both near- and

ar-eld scales. Although not generally



viewed as an issue by wind energyengineers and scientists, energy removalby devices in water, as well as blockageeffects, can lead to localized changesin water movement energy and turbu-

lencethese changes, in turn, can causebenthic sediment scouring and resultanthabitat changes. In the water column,modications to water movement energyand turbulence could lead to changes inturbulence and stratication, potentiallyaltering vertical movements o marineorganisms and resulting in prey andpredator aggregation.

In the ar eld, energy reduction

could lead to changes in currents andsubsequent alterations in sediment trans-port. Although ew studies have beenundertaken, surveys at an installed wind

arm in the North Sea that used mono-pole oundations with scour protection

showed secondary scouring (Rees et al.,2006). Further, a modeling study basedon wind arm data highlighted ar-elddeposition downstream o the windturbine oundations (Besio and Losada,2008). Te impact o this effect has notbeen determined, but i an ORED site isrelatively nearshore (e.g., within a ewkilometers), beach replenishment anderosion/accretion may be affected, with

implications or coastal de ense andmanagement. Furthermore, i the site isadjacent to navigation/shipping lanes,then the dredging regime may requirealteration. A related effect could be

changes to seasonal opening and closingo small estuarine areas, potentiallyaltering the availability o those systemsto migratory animals like salmonids(Largier et al., 2008). Te existing sedi-ment dynamics and amounts o sedi-ment movement need to be actored intothe analysis. Tese examples demon-strate how the level and scale o effectsover time need to be assessed be ore

trying to assign impact.Removal o sufficient tidal energy

could result in changes in tidal range,potentially impacting communitiesdependent upon periodic exposure; theextreme o this case is seen in the tidal

barrage, where blockage o water owwill result in lower water exchange andtidal heights as compared to the naturalsituation (Goss-Custard et al., 1991).Tis change in tidal range, in turn, couldhave impacts on intertidal ecosystems,affecting oraging habitat or shorebirdsand distribution o intertidal animals(Goss-Custard et al., 1991). Modelingo turbine-based tidal devices in Puget

Sound, Washington, suggests that theproposed amounts o energy reductionwill have a relatively minor effect on tidalheight (Polagye et al., 2009). Amongmarine renewable energy devices, those

that pressurize water pumped to shore-based turbines may move moderateamounts o water. For O EC, very large volumes o both cold deep and warmshallow water are moved to take advan-tage o the thermal difference betweenthem. Te potential or impingementand entrainment o mobile species isan issue in this case, analogous to thecooling waters o conventional power

plants (Harrison, 1987) or desalinationplants; the problem is less severe or thedeep cold water intakes due to the lowerdiversity and biomass o organisms.Warm water intakes may have signicantimpacts on planktonic and perhapspelagic organisms (Harrison, 1987), aswell as more general effects o O ECon sheries (Myers et al., 1986). Teresponse may be expressed ecologicallywith increased production as a result omore nutrients rom the deep water.

Chemical EffectsIn most cases, the effects o chemicalsused in marine renewable energy willdiffer little rom other marine construc-tion projects. During deployment,routine servicing, and decommis-sioning, the expected risks associatedwith marine vessel operations will beencountered. In normal operations, thepotential or spills exists, particularly

or those devices that use a hydraulicuid. Continuous leaching o chemicalsmay occur i anti- ouling paints areused to minimize biological oulingo devices. As technologies develop,in ormation is needed on the nature

I IS CLEAR HA MUCH WORK IS NEEDED OADDRESS HE ENVIRONMEN AL EFFEC S OF MARINE

RENEWABLE ENERGY, AND INDEED O DEVELOP ANUNDERS ANDING OF PO EN IAL IMPAC S.



o toxic compounds to be used, poten-tial amounts that could be released,responses o receptors, and the ateo the contaminants.

A special case is involved or O EC,

and additional concerns emerge. Teworking uid in a closed system (typi-cally proposed to be ammonia, which ishighly toxic to sh) could be subject toleaks or spills. Te natural chemistry othe deep waters brought to the sur acehave the potential to alter chemicalconditions in the location where water isdischarged. Carbon dioxide, or example,could be outgassed to the atmosphere.

Higher amounts o nutrients dischargedin sur ace waters could induce algalblooms in areas normally low in sur acenutrients (Harrison, 1987). Higher heavymetal concentrations, either rom deepnatural sources or rom heat exchangers,could have toxic effects (Fast et al., 1990).Mitigation or these effects has beensuggested (Abbasi and Abbasi, 2000;Pelc and Fujita, 2002). An additionalconcern could be acidication effectsas noted or naturally upwelled watersby Feely et al. (2008).

Acoustic EffectsTe ocean is an acoustically diverse envi-ronment. From a biological perspective,acoustics are vitally important in animalcommunication, reproduction, orienta-tion, and prey and predator sensing.

In terms o sounds produced byOREDs, there are a number o potentialsources as well as different temporal andspatial scales to consider. It is widelyregarded that the construction phaseo an ORED will be the most acousti-cally diverse and the noisiest (Tomsenet al., 2006). Tere will be a largeamount o shipping movements in and

out o the area, seismic surveys at thestart o the project, and constructionnoise. I the energy devices require any

orm o piling, then the predominantnoise issue will be associated with pile

driving, which is currently o greatestconcern or its effects on acousti-cally sensitive species (Tomsen et al.,2006). Pile driving is associated withmonopole wind and tidal turbines andother devices that require small piles orsecuring jacket oundations. Pile drivingcan generate very-high-intensity butrelatively short-duration noises.

Te operational phase o ORED will

likely add to the normal backgroundacoustic environment. Devices withsubsur ace moving parts, such asunderwater turbines or hydroplanes,are assumed to be the noisiest; however,data to quanti y the noise are lacking.Acoustic proles rom all device types,cables, and other sound-producingcomponents will require measurementto determine the levels and requenciesabove background sound.

Te main perceived impact o anthro-pogenic underwater noise is currently

ocused on sh (Hastings and Popper,2005) and marine mammals (Southallet al., 2007). Other organisms, such ascrustaceans, have not, to our knowledge,been considered in the context o renew-able energy devices. However, literatureindicates that the crab and lobster larvaeare oriented or settling by ree noise(Montgomery et al., 2006). Evidence

rom Danish studies suggests thatmarine mammals respond by movingaway rom an area where constructionis taking place (Brandt et al., 2009).Once the noisy activities have ceased,there appears to be no effect, and themammals occupy the ORED area as

much as other adjacent habitats. Hence,there is a denite effect in terms oavoidance, but the effect is not perma-nent (Brandt et al., 2009). Te temporarynature o the avoidance recorded to date

is not interpreted as an impact on themarine mammals. With the advent olarger turbines and more extensive arrayso devices, however, the constructionperiod will be extended. Furthermore, inareas such as the strategic developmentzones in the seas o northern Europe,the cumulative effect o the constructiono multiple OREDs is likely to render alarge area un avorable or species that

react to the noise through avoidance.Clearly, a better understanding o thetransmission o the sounds producedand any threshold intensities (and/ordistances rom the noise) is required(Tomsen et al., 2006). Whether there isany reaction to sound signals rom oper-ational devices has not yet been deter-mined and will inevitably be raised as aquestion at some point in the uture. It isalso possible that some animals could beattracted to the produced noise, resultingin other unknown effects like entangle-ment or area restricted movement.Alternatively, detection o operationalnoise could lead to avoidance o devices,resulting in ewer interactions. As yet,these are merely points o speculation. Itis crucial that these acoustic studies beimplemented as rapidly as possible.

Modeling noise in the marineenvironment is difficult but relativelyadvanced, certainly in comparison tounderstanding its effects. Future acousticmodeling o noise should be aimed atunderstanding the intensity and acousticprole rom a variety o devices suchas buoys, turbines, pumps, and cablesas they may be use ul to assess impacts



rom various scales o energy acilitybuild-out. Modeling studies o acousticpropagation in ORED areas should alsobe undertaken to assess the characteristicdistances where effects may be located.

Electromagnetic EffectsWith the exception o shore-based O ECor devices that pump pressurized water,marine renewable energy devices by their very nature are required to transmit theelectricity produced to shore. Tis maybe accomplished through a network ocables that transmits power rom severaldevices to a large collector cable that is

connected to a shoreline substation, oran offshore substation that trans ormsthe energy or the receiving electricalgrid system. During transmission othe produced electricity, the cables willemit low- requency electromagneticelds (EMFs; Figure 2). At present,the industry standard or design o the

cables requires shielding, which restrictsthe directly emitted electric elds butcannot shield the magnetic componento an EMF. Te movement o waterand organisms through the emitted

magnetic eld will then induce localizedelectric elds (Ohman et al., 2007). IAC cables are used, the magnetic eldassociated with the cable has a rotationalcomponent, which also induces electricelds in the surrounding environment(CMaCS, 2003).

A number o organisms that inhabitthe coastal and offshore environmentare able to sense either magnetic elds,

electric elds, or both. axa that havebeen determined to be magneto-sensitiveare generally those that undertakelarge-scale migrations or use Earthsnatural geomagnetic elds or orienta-tion (examples can be ound amongthe cetaceans, herptiles, teleosts, andcrustaceans; Kirshvink, 1997). In terms

o electroreception, the whole taxo-nomic class o the Chondrichthyes, theAgnathans, and the Chondrostei have thesensory apparatus to detect and respondto electric elds (Collin and Whitehead,

2004). Such species use electroreceptionas a undamental sensory mode to detectthe very low- requency bioelectric eldsemitted by prey to locate mates and ororientation. Hence, EMFs emitted bythe marine renewable energy harnessingprocess is most likely to affect animalsthat use EMFs or spatial location, large-scale movement, small-scale orientation,

eeding, or mate nding.

In a review o the state o knowledge,Gill et al. (2005) ound that little wasknown concerning electrically andmagnetically sensitive marine animals;

or offshore wind arms, there were nostudies o direct relevance. However, asmall number o studies now exist, someo which relate to just subsea cables (notnecessarily rom a renewable energysource) and others that have started toaddress the dearth o in ormation avail-able on the topic.

Tere is evidence that eels can tempo-rarily respond to EMFs rom cablesduring their migration by diverting romtheir path o movement (Westerbergand Lagen elt, 2008). Recent studiesconducted in the UK have given initialinsight by showing that benthic elasmo-branchs can respond to EMFs emittedby subsea cables and also that the cables

rom an operating wind arm do produceEMFs within the range o intensitiespreviously predicted rom models (Gillet al., 2009). EMF responses were vari-able between individuals, something thatis consistent with individual variabilitywithin a population, and indicated anattraction to the route o a subsur ace

Figure 2. Te magnetic eld ( esla) outside an industry standard 13 kV subsea cable buried to 1 m.Te seabed surface is shown as the horizontal blue line.Source: Centre for Intelligent MonitoringSystems, University of Liverpool, UK



cable when electricity was being trans-mitted. Te ew studies to date havehighlighted that this is an area o consid-erable uncertainty, but there appear to besome responses to EMFs emitted by the

cables. Tere are no data available thatallow an assessment o impact.

Be ore-and-afer baseline assessmento EMFs associated with cable networkswithin an array o devices in additionto the main cables to shore is needed.Furthermore, there needs to be a greaterresearch effort to determine the detect-ability by the potential receptors o arange o elds emitted; the response

and potential biological signicanceo detection, i any, also remains to bedetermined. At present, major areaso uncertainty exist about the effect oEMFs on receptors.

Termal aspects o electricity-transmitting cables may also need to beconsidered. Tere are predictions thatelectricity production will increase thetemperature in the surrounding sedi-ment and water. A current suggestion isthat the thermal effect is a small rise intemperature within a ew centimeters othe cable. Whether this small tempera-ture change will represent a stressor tobenthic communities is yet to be deter-mined, but will have to be considered inthe context o the effect on the benthiccommunity o major disturbance o sedi-ment during cable laying.

RECEP ORSPhysical EnvironmentWith the exception o O EC, marinerenewable energy devices operate byremoving kinetic energy rom water(or air in the case o offshore wind).For devices at sea or in estuaries, theresultant reduction o energy may lead

to downstream effects. idal energydevices may result in local accelerationand scouring in some cases, but havethe potential to decrease tidal amplitudein downstream areas (the proceed-

ings o a scientic workshop on theenvironmental effects o tidal energydevelopment held at the University o

Washington March 2224, 2010, will beavailable at: http://depts.washington.edu/nnmrec/workshop). Shadow effects owave energy devices may alter sedimenttransport and deposition as well as havean effect on beach processes (Milleret al., 2007; Largier et al., 2008). Pilotprojects across the world to understandand model wave reduction effects areunderway. Analysis o project geometry,density, and distance rom shore makesmodeling easible to assess effects, butthese models have yet to be calibrated indeployments o real devices, particularlyat commercial scales.

O EC represents a special casebecause the energy is derived rom athermal difference between cold deepwater and warm sur ace water, mostofen in the tropics or subtropics. Temixed effluent rom these acilitieswill be released at depths ar shallowerthan where the cold water was taken,resulting in altered thermal regimes(Harrison, 1987).

Pelagic HabitatTe buoys, cables, turbines, spars, and vertical pillars associated with mostrenewable energy devices will modi ypelagic habitats by creating structure

where none existed. Tis will likely havea minimal impact on phytoplankton andmost zooplankton, but positive effects

on abundance (through aggregation)o other species (e.g., krill, mysids, andshes). Tis, in turn, will likely result inattraction o additional predators thatmight not otherwise aggregate there.Tis effect is well known in pelagicenvironments, and, in act, in certainplaces, so-called sh aggregationdevices (FADs) serve an equivalent

unction to articial ree s in benthicenvironments (Addis et al., 2006; Ingeret al., 2009; Figure 3). Tese structuresmay also serve to acilitate settlemento meroplankton in habitats ormerlylacking adequate structure or thesespecies. Impingement, blade strike, colli-sion, and entanglement issues also exist,given the added structural complexity inmidwater rom many devices. Becauseo the large water volumes required orO EC, impingement mortality o plank-tonic organisms on screens at the plantswill likely be a signicant problem. Inaddition, the coldwater effluent, withits higher nutrient level, may stimulate

SE ING ENVIRONMEN AL S ANDARD

OREDs IS PAR ICULARLY URGEN , YE HESE SMUS S RIKE AN APPROPRIA E BALAN



blooms, depending upon the depthdistribution o the discharge andmixing. Blooms could change the natureo pelagic habitat at selected scales,including water quality and clarity.

Benthic HabitatIntroduction o manmade structuresinto marine environments may havethe greatest impact on benthic habitatsand ecosystems, based on structuralhabitat changes as well as modicationsto water circulation and currents. Tearticial ree effect will stimulate somespecies but may negatively affect others(Langhamer and Wilhelmsson, 2009).Placements in sand bottoms will likelyresult in greater biodiversity (Ingeret al., 2009), but this may also affectadjacent benthic communities throughgreater predation (Langlois et al., 2005).Community growth on buoys (as shownby Langhamer et al., 2009), anchors,and lines may also have effects as theseorganisms will likely accumulate onthe seaoor (e.g., by sloughing off or by

routine maintenance o mooring linesand buoy structures; Figure 4). Te shellmounds evident under long-deployedoil plat orms represent an extreme caseo benthic habitat modication, but mayconstitute productive sh habitat (Loveet al., 1999; Goddard and Love 2008).Effects on the benthos will likely scale ina nonlinear ashion, affected by connec-tivity as multiple acilities interact. In thecase o new hard bottom over ormerly

long stretches o sand habitat, orexample, these sites have the potentialto serve as steppingstones or species,including invasives.

Depending upon the location odischarge and degree o mixing, cold,dense water rom O EC acilities mayalter benthic communities as it owsdownslope. Te large volume o waterhas the potential to impinge uponbenthic environments such as coral ree s,

Figure 4. Shell mounds accumulateon formerly soft bottoms under oilplatforms off California change thenature of the benthic habitat andattract a different community oforganisms, including the seastarsshown here and shes (Goddardand Love, 2008).Donna Schroeder,Minerals Management Service

Figure 3. unas and otherpelagic species will aggregatearound drifting or mooredobjects as they do around shaggregating devices, locallychanging the nature of pelagichabitat. National Oceanic and

Atmospheric Administration,Danilo Cedrone (UNFAO)



creating thermal stress or the organismsliving there (Harrison, 1987). Over thelong term, this could lead to changes inthe benthic community and, in turn, tostructural changes to the habitat.

FishesOREDs will affect sh communitystructure through changes in speciescomposition (Wilhelmsson et al., 2006).As noted above, structures will result inattraction o both pelagic and benthicspecies. Structures will likely increase thesettlement habitat or some species, anddiversity and abundance o others in the

regions o the renewable energy devices,but it is uncertain to what degree popu-lation size will change and thus, whetheran impact will occur.

Assuming that there are no avoid-ance effects o ORED operation (due tonoise or EMF) or shed species, it hasbeen suggested that larger-scale OREDswill act as de acto marine reserves dueto potential exclusion o shing withindeployment areas (DOE 2009). Tus,they may potentially serve as sources

or recruitment to adjacent shed areas.Attraction o large predatory shesthat were absent in the pre-deploymenthabitat may result in increased mortalityo resident species as well as new speciesattracted to the devices. Fish thatmigrate through areas where renewableenergy devices will be deployed may beaffected. In the US Pacic Northwest,

or example, juvenile and adult salmon,elasmobranchs, and sturgeon movethrough regions proposed or waveenergy development. As discussed understressors, behavioral effects resulting

rom electromagnetic elds, chemicalor acoustic signals, or a combination osuch stressors could impact movement

patterns o these species. Whether thereare any interactions between these effectsand whether they constitute impactsremain to be evaluated.

Marine Birds and MammalsTis group o receptors is, in general,given the greatest attention in environ-mental assessments in many countries.For many species, past human activitieshave led to negative impacts on popu-lations. In addition, they are highly visible, have greater public interest, andare ofen protected by laws (e.g., theMarine Mammal Protection Act in the

United States ; International Union orConservation o Nature [IUCN] clas-sications; EU Habitat and Speciesdesignations). For these reasons, and asspecies-based conservation managementis currently the ocus o our activitieswhen considering human impact on theenvironment, impacts to marine birdsand mammals may have greater conse-quences or the development o marinerenewable energy. However, more recentmoves toward ecosystem-based coastalmanagement will require greater balancein the considerations o many receptorsand the cumulative impacts o ORED onthe environment.

Tere is signicant current interestin the potential effects o ORED onseabirds. Lighting and above-waterstructures may attract seabirds, poten-tially resulting in collisions, particularlyat night when less is known aboutseabird distribution and behavior.However, evidence to date suggests thatbirds avoid wind turbine structuresand are well able to navigate throughthe array o turbines (Desholm andKahlert, 2005). In contrast to onshorewind arms, there are comparatively ew

records o collision by seabirds withoffshore devices. A possible impact maybe related to the energy that the birdsuse in avoiding a wind arm (Masdenet al., 2009). When an organism has to

signicantly alter its path o movement,it expends some energy; how muchenergy it costs the organism is the effectthat needs to be considered. In a recentmodeling-based study using data ondaily energy demand in several birdspecies, it was determined that whilethere is an increase in energy use bylarge-scale migratory birds on encounterwith a single wind arm, they are well

able to cope with it. However, the morelocal, diurnal migratory species have aproportionately greater energetic burden,which may then have impact on thetime and energy they have available oracquiring ood i the burden is prolonged(Speakman et al., 2009). Te cumulativeeffect o multiple installations there orerequires consideration in the uture.

In the ocean, as ORED structuresalter habitats, communities, and preydistributions, certain seabirds could haveenhanced eeding opportunities and thusaggregate near sites; similarly, changes tobeach processes or tidal excursions mayaffect shorebird oraging. Diving birdsmay ace entanglement, collision, orblade strike with subsur ace componentsor devices. Data gaps to be lled includespatial and temporal abundance o birds,particularly bird activity at night, impor-tant areas o bird activity ( or examplenear nesting colonies) that should beavoided, important migration patterns,and potential effects on seabird prey.

As noted above, a diversity oconcerns exists or marine mammalsacross all ORED technologies; entangle-ment and collision, mainly or cetaceans,



are primary concerns. Blade strike inthe case o ocean current or tidal devicesmay also be o concern (Wilson et al.,2007). For those devices with cables andmoorings, the nature o mooring cables(slack or taut, horizontal or vertical,diameter) is critical to entanglementissues. Should sh and invertebratesbe concentrated around devices aspredicted, both cetaceans and pinni-peds could be attracted by the eedingopportunity (as has been suggested instudies around Danish wind arms onceconstruction has ceased; DONG Energyet al., 2006), thereby increasing the likeli-hood o impact. Special attention shouldbe paid to migratory routes or special

eeding grounds. In the case o graywhales along the Pacic coast o NorthAmerica, the migration along the coastpasses through optimal regions or waveenergy device deployment (Herzing

and Mate, 1984; Figure 5). Te acousticsignature o the devices could eitherattract or repel marine mammals. EMFeffects on marine mammals is poorlyknown; or species that rely on Earthsgeomagnetic eld, there is the potential

or orientation to the magnetic eldsemitted i they are large enough and/ordiscernible rom background levels, andthis should be investigated. Fundamentalbaseline data will be needed (mammalbiology, presence/absence/speciesdiversity, in ormation on prey species)to understand projects impacts and thecumulative effects as ORED reachescommercial scales. As pilot or demon-stration projects are put in the water,immediate monitoring o potentialreceptor cetaceans and pinnipeds(e.g., videography, beachings, tagging, vessel surveys) will be needed to under-stand how they interact with OREDs.

CONCLUSIONSAn analysis o published literaturedemonstrates a dramatic increase inthe number o studies dealing withrenewable energy; the percentage

that deals with environmental effects,however, is relatively meager (Gill,2005). Troughout this article, we havenoted research needs, but they are toonumerous to identi y in any one place.Instead, able 1 provides re erences bytechnology type that identi y neededresearch; or those documents not widelyavailable, URLs are cited.

It is clear that much work is needed

to address the environmental effects omarine renewable energy, and indeed todevelop an understanding o potentialimpacts (Figure 1). Fortunately, OREDsare proceeding somewhat more slowlythan terrestrial-based renewables suchas wind and solar. In northern Europe,there are a number o operationaloffshore wind arms. Environmentaleffects research, however, is increas-ingly lagging behind the developingtechnology; there is thus an urgent need

or such research (Inger et al., 2009).In the United States and in many othercountries, ORED demonstration proj-ects or pilot-scale acilities are underdevelopment. Concurrent environmentalresearch at these sites will help reduceuncertainty o effects and identi yimpacts or all stressor and receptorgroups. Tis research, in turn, will leadto improvements in the best practices

or design o devices and arrays and tobetter per ormance standards and moni-toring requirements or application tocommercial-scale development. Settingenvironmental standards or OREDs isparticularly urgent, yet these standardsmust strike an appropriate balance. I

Figure 5. Gray whales (Eschrichtius robustus) migrate along the west coast of North America, often withinthe depth zones where wave energy is proposed for development. Te behavioral response of marinemammals to OREDs is an area of high uncertainty.Craig Hayslip, OSU Marine Mammal Institute



environmental assessments are too lax,we risk severe environmental damage.I the required assessments are overlyrestrictive, however, there is a risk oinhibiting the development o renewableenergy technologies that have the poten-tial to reduce our reliance on ossil uels.

ACKNOWLEDGEMEN SWe thank the guest editors o this specialissue o Oceanography or their work(and persistence) in organizing this

valuable volume. We also thank GlennCada, Sarah Henkel, and Roger Bedard

or comments on an earlier version o themanuscript. GWB acknowledges support

or this work rom the US Departmento Energy (Award Number DE-FG36-08GO18179 or the Northwest NationalMarine Renewable Energy Center) and

rom the Oregon Wave Energy rust.ABG acknowledges support romcolleagues and Craneld University.

able 1. Available literature that provides recommendations for needed environmentalresearch on ocean renewable energy developments (ORED)1

ORED Technology Available References

Offshore Wind

MMS, 2008 COWRIE publications (http://www.o shorewind.co.uk/Pages/Publications/Archive) Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR), 2008 Wind farms: http://www.ospar.org/documents/dbase/publications/p00385_Wind-farms%20assessment.pdf Scottish Department for Business Enterprise & Regulatory Reform (BERR), 2008.

Reef e ects: http://www.berr.gov.uk/ les/ le43528.pdf Punt et al., 2009 OSPAR, 2009. Cables:

http://www.ospar.org/documents/dbase/publications/p00437_JAMP%20assessment%20cables.pdf OSPAR, 2009. Noise:

http://www.ospar.org/documents/dbase/publications/p00436_JAMP%20Assessment%20Noise_ nal.pdf

O EC Harrison, 1987 Myers et al., 1986

Wave

Boehlert et al., 2008 (http://hdl.handle.net/1957/9426) California Energy Commission, 2008. Potential Socio-Economic and Environmental E ects

(http://www.energy.ca.gov/2008publications/CEC-500-2008-083/CEC-500-2008-083.PDF) Inger et al., 2009 ABP Marine Environmental Research (ABPMer), 2009. Management Strategies:

http://www.abpmer.co.uk/ les/R1451_Final_05Mar09.pdf

idal Proceedings of Environmental E ects of Tidal Energy Development: A Scienti c Workshop 2

(http://depts.washington.edu/nnmrec/workshop) ABPMer, 2009 (http://www.abpmer.co.uk/ les/R1451_Final_05Mar09.pdf)

Ocean Currents For the most up-to-date information, see DOE (2009)

Multiple OREDtechnologies

DOE, 2009 (http://www1.eere.energy.gov/windandhydro/pdfs/doe_eisa_633b.pdf) Faber Maunsell and METOC PLC, 2007 (http://www.seaenergyscotland.co.uk) European Marine Energy Center (EMEC), 2008. Environmental Impact Assessment:

http://www.emec.org.uk/pdf/EMEC%20EIA%20Guidelines%20GUIDE003-01-03%2020081106.pdf 1 Many of these documents are not readily available in the published literature, and we thus provide URLs where they may be found.2 Te workshop was held March 2224, 2010; proceedings will be published as a NOAA echnical Memorandum and available from this Web site.

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