HABITAT CLASSIFICATION - Gulf Of Maine

2.0Introduction and Goals of the ReportThis report presents information about habitatclassification relevant to management and conservationneeds in both the nearshore and offshore regions of theGulf of Maine. The report serves to inform discussionsamong stakeholders seeking to identify a classificationscheme appropriate for the region. It is a continuation ofthe work of the Habitat Conservation Subcommittee ofthe Gulf of Maine Council on the Marine Environmentand an activity identified in the Gulf of Maine Councilon the Marine Environment Action Plan 2007-2012 (seewww.gulfofmaine.org/actionplan).This report is meant to provide a basicunderstanding of marine habitat classification so thatstakeholders can participate equally in the discussion.The report includes definitions, an explanation of whyhabitat classification is important for conservationand management, and an overview of some commonresearch methods. The report also reviews some currentmarine classification schemes intended for applicationat the regional level within the Gulf of Maine region, in3.0an adjacent region, or on a national scale. This reviewincludes research that has yet to be published in peerreviewed literature.The report does not review schemes in depth, butit provides a clear, concise, and accessible description,so they can be understood and compared. Also, thisreport does not seek to endorse one scheme overanother. Each system was designed for a specificpurpose and therefore involves a unique set of strengthsand weaknesses. The report does, however, makerecommendations on various issues in an effort toprovide direction and framing to the conversation onmarine habitat classification in the Gulf of Maine.The information included in this report is derivedfrom a combination of research papers and interviewswith researchers. Additionally, a December 2006 draftcopy of the Massachusetts Office of Coastal ZoneManagement’s Feasibility Study on Habitat Classificationby Katie R. Lund and Anthony R. Wilbur provided usefulinsight into various schemes.Researching Marine Habitat Classification3.1 Marine Habitat Classification DefinedThe incredible diversity of organisms present in theworld mirrors a similarly diverse range of habitat types.In both cases, there are limitations in whether certaincharacteristics can or cannot be associated with oneanother. For example, organisms with gills rarely havefur. Similarly, the deep ocean floor (referred to as theabyssal plain) does not support seagrass communities.In some ways, however, designing a classificationscheme for habitats is more difficult than designingone for biological organisms. Because organisms are aproduct of their genetics, many characteristics simplycannot coexist based on their respective evolutionarypaths. The same is not always true of the physical,chemical, geological, and biological characteristics atplay in habitats, which makes habitat classification moredifficult and ultimately more subjective.Habitat is loosely defined as any area that providesthe conditions and resources that a species needs tosurvive. Following this definition, ‘marine habitat’ isany such area in the marine environment, including butnot limited to the sea bottom, water column, intertidalareas, deep seafloor, estuaries, and so on. Differentiatingamong these various marine habitats is the basic task ofmarine habitat classification and the basis for this report.Marine habitat classification is an area of researchthat describes discrete habitat types within a definedspatial scale. The descriptions are based on variousgeological and biological characteristics such as depth,substrate type, and the organisms associated with aparticular area. Many different classification schemesexist to differentiate these habitats from one another,reflecting the difficulty of dividing natural continuityinto a set of artificially distinct categories.Classification approaches are used to organizeitems in a variety of contexts—from grocery stores toliving organisms. While using a classification scheme toensure that all dairy products are kept together seemsrather straightforward, designing a taxonomic schemeto organize all known living organisms on the planet isa much greater challenge. The latter provides a muchbetter comparison for what researchers are attempting todo with marine habitats.Habitat Classification in the Gulf of Maine3.2 Classification Versus MappingWhen discussing habitats, people often use theterms classification and mapping interchangeably.1While both are important when converting continuous1 “Characterization” and “description” are two more terms sometimes used instead of “classification” and “mapping.” In general,habitat descriptions are qualitative narratives that define differenthabitats. Habitat characterization, on the other hand, refers to thegathering of data that characterize a specific habitat; this information often can be helpful in habitat classification efforts.www.gulfofmaine.org

habitat into discrete categories, they are differentprocesses. Habitat classification refers to the use ofcharacteristics such as salinity, sediment type, or speciesto define a given habitat type. Habitat mapping involvesspatially illustrating habitat distributions.Although classification and mapping are two verydifferent processes, the two are most useful whenapplied together; therefore, the distinctions betweenthem are less critical for the current discussion. Aclassification scheme without a spatial component isonly a tool for habitat taxonomy. It is important to knownot only the habitat types but the locations of the habitattypes. Hence the importance of habitat mapping. Forexample, while knowing that a habitat characterized by“rocky, immobile substrate with high rugosity2 and lowbiogenic structure3” exists is valuable, managers alsoneed to know where that habitat exists, how common itis, and what habitats surround it.The schemes covered in this report differ inthat some are aimed primarily at generating maps,while others are designed with maps as a secondarytool. Understanding the context of different schemesis critical when discussing how they may addressmanagement and conservation needs.to consistently describe specific habitats, managers andresearchers can help to ensure that communicationamong agencies, jurisdictions, regions, and studies isefficient and effective.Long-term resource tracking becomes more efficientwhen managers identify habitats in the same way fromyear to year. Furthermore, changes in the patterns ofresource use become easier to identify when many sitescan pool their data to permit regional analyses. If localand regional managers know the types and locationsof marine habitats in their jurisdictions, they arebetter equipped to address human impacts that affectparticular habitat types.Knowing what habitats are present in a given areaallows for better management of the marine resourcesand the potential uses (e.g., fisheries, mineral extraction,tourism) that are associated with those habitats. Itis difficult to understand the effects of one sectoron another without an understanding of where theyintersect, which often relates to habitat type. This appliesfor all scales of management from local to regional.3.4 Data Collection MethodsOcean mapping has greatly improved from thedays of attaching a lead weight to the end of a lineand lowering it from the side of a ship. A numberof technologies are currently available to map bothshallow and deep habitats. They provide data at differentresolutions and in different forms, but they all combineto provide a fuller understanding of the habitats targetedfor mapping. The majority of the technologies andmethods described below involve indirect or remotesampling. For these indirect methods, it is critical toensure that adequate direct sampling takes place to“ground truth” the habitat patterns and classificationsgenerated from the remotely collected data.The following list is not meant to be comprehensive.It merely serves the purpose of informing a broadaudience about the range and nature of technologiesthat are in practice today.3.3 Why Is Marine Habitat Classification Importantto Managers and Conservationists?Habitat classification allows people to communicate more effectively about the environment aroundthem. Lessons learned in one region need to beavailable to other regions that are facing similar issues.Classification allows some level of transferability ofthis kind of information, especially when determiningwhich environmental factors are important asindicators for system health. Without this transferability,conservationists and managers have to perpetuallyreinvent the wheel.Lessons learned are widely shared among terrestrialmanagers, partly because habitats are already classifiedand mapped at many levels of resolution. Terrestrialmanagers also enjoy the luxury of directly seeing andexperiencing the results of long-term adaptive strategies.The marine environment lags behind its terrestrialcousin in that we still do not have a sufficiently standardmarine classification system, nor do we have thebenefit of actually seeing in real time the impacts ofmanagement decisions. By using a standard framework2343.4.1 Satellite DataSince 1997, satellite altimetry4 has madeinformation available for many of the world’s oceans.This information is not generally of a sufficientresolution to be useful for direct mapping purposes, butit does provide a base level of water-depth informationRugosity is a measure of surface roughness or complexity, frequently defined as a ratio of the surface area of a region to its planar area.Biogenic structure is a term for physical formations—such as kelp forests, coral reefs, and shellfish beds—that are created by organisms.Altimetry is the measurement of altitude. In satellite altimetry of the ocean, satellites measure the small changes in sea-surface elevationthat reveal the presence of seafloor topographical features.Habitat Classification in the Gulf of Maine www.gulfofmaine.org

Differential GlobalPositioning arExamples of methods used to collect information about the seabed for habitat classification.width of the imaged swath is twice as wide as the wateris deep. In this way, very large stretches of ocean can bemapped quickly when in deeper water. As the water getsshallower, however, the swath gets smaller. Therefore,a greater number of “passes” are required in order tocover a given area. This makes multibeam sonar lessefficient for measuring bathymetry in shallow waters. Itis generally used in deep, offshore waters.Single-beam sonar works similarly to multibeamsonar, except that only a very small footprint directlyunder the array is measured with a single pulse ofsound. Because the footprint is so small, single-beam isnot useful for measuring depths across a large area, butit can generate very accurate bathymetric contours forthe route traveled by the research vessel. Single-beamsonar is effective in shallower waters (depths less than4 meters), however, so it can be used in conjunctionwith multibeam sonar, which is most effective in depthsgreater than 10 meters.In addition to providing depth information, thereturning sound waves also provide information aboutthe properties of the surficial substrate. Substrates reflectsound waves differently according to their specificproperties—the harder the substrate, as with bedrockor shell fragments, the stronger the returning signal or“backscatter.” The image generated from the backscatterappears in shades of white, grey, and black. Whiterepresents a very strong returning signal, and blackindicates no returned signal (also referred to as a void).With multibeam sonar, backscatter also providesa shaded view of the seafloor topography. Threedimensional features such as pinnacles and bouldersfor offshore areas. A more recent generation ofcommercial satellite systems called QuickBird waslaunched in 2001. QuickBird provides multi-spectralphotography of intertidal bottom conditions.Satellites also provide information on sea-surfacetemperatures and currents. Measurements of sea-surfacesalinity will be possible with the launch of a newEuropean satellite in 2007.3.4.2 Multibeam and Single-beam SonarMultibeam sonar uses sound waves to provide highresolution, three-dimensional data on ocean depthsand seafloor topography. It is especially useful in areasof deep water. The sound waves are generated froman array attached on a ship hull or in some cases on apole attached to the side of a boat. The array consistsof a number of transducers5—some that transmit andsome that receive—arranged in a specific pattern on aset of perpendicular bars. The transmitting portion ofthe array sends out a pulse of sound waves in a broadswath below the boat. The swath is wide to either sideof the ship but narrow from front to back. The soundwaves reflect off the substrate and return to the receivingportion of the array at specific angles.The time it takes for the sound waves to return to thearray provides depth measurements for various pointsalong the swath. The number of depth measurements(and therefore the resolution) is dependent upon howmany transducers are in the array, the specific shapeof the array, and the depth of the water. In general, the5Transducers are small devices that convert electrical impulsesinto sound waves and vice versa.Habitat Classification in the Gulf of Maine www.gulfofmaine.org

show up with the side facing the sonar array appearingbright white. The side facing away appears blackbecause it is in the “shadow” of the sound waves.3.4.3 Sidescan SonarSidescan sonar can be used in shallow waters, andit detects features of the substrate such as sand wavesand shipwrecks. Sidescan sonar operates similarly tomultibeam sonar in that it uses a swath of sound wavesreflecting off the seafloor. However, a sidescan sonararray is streamlined and is towed at some distancebehind and below the operating vessel. The sidescansonar array resembles a finned torpedo and is oftencalled a fish-tow because of its shape. Because the fishtow is much lower in the water, the sound waves strikethe seafloor at a shallower angle, providing a greateroverall footprint for imaging and highlighting threedimensional objects from a greater angle. Sidescansonar systems, however, tend to be more expensive thanhull- or pole-mounted multibeam systems.Iceberg gougesGlacier valley3.4.4 LiDAROften referred to as laser imaging, Light Detectionand Ranging (LiDAR) uses light waves in the placeof sound waves to measure heights of nearshorebenthic formations. Depth and water conditions (e.g.,turbidity) limit the effectiveness of LiDAR. Generally, itis used along the coastline to create three-dimensionalimages of intertidal areas and above the high-tidemark. Typically the LiDAR array is mounted on a lowflying aircraft, but it can be ground-based, dependingon the characteristics of the coastal topography.LiDAR produces very high-resolution measurements.Light waves have a shorter wavelength than soundwaves, so LiDAR can measure smaller objects thansonar. An added benefit of LiDAR is that the habitatcharacterization data can be matched with a highresolution photograph of the targeted area.Sonar backscatter imagesreveal seafloor features inthe Gulf of Maine.usually required to measure or confirm the biologicalcharacteristics used in habitat classification.Direct sampling provides the highest-resolutioninformation, but it is also the most labor intensive.Consequently, direct sampling generally is used inconjunction with indirect methods. For example, directsampling is used to ground-truth the data produced bymultibeam and sidescan sonar.Direct sampling can take many forms. Visualsampling (both video and still) can be performedby remotely operated vehicles (ROVs), mannedsubmersibles, dropped and towed cameras, and diverswith appropriate gear. The appropriate method dependson the depth and characteristics of the habitats inquestion. ROVs and manned submersibles generallyare used for deeper, offshore waters. Physical samplinginvolves the collection of geological and biologicalsamples with grabs, cores, and other gear, which maybe deployed from a boat or ship. Just as with visualsampling, the appropriate method depends on thedepth, habitat type, and the type of data being sought.The data-collection methods described aboverequire processing time and analysis, and indirectmethods also require ground-truthing. As a result, timeand funding typically are major factors that limit theresolution of habitat data.63.4.5 Direct SamplingThe previous methods all involve indirect, orremote, sampling. Sound waves measure depth aftertaking into account angles and interference patternsbetween multiple transducers. Backscatter providesinformation about the substrate, but only after agreat deal of processing. Only by directly samplingthe substrate—its depth, composition, or othercharacteristics—can one be certain of the validity ofindirect measurements. For this reason, direct sampling,also referred to as ground-truthing, is an importantstep in habitat classification. Direct sampling isHabitat Classification in the Gulf of MaineEskers6 For a more detailed discussion of information- and data-gatheringfor identifying habitat characteristics and the use of variousmethods, see Valentine et al. (2005).www.gulfofmaine.org

4.0Habitat Classification Schemes4.1 General OverviewIn most cases, classification schemes are designedto address specific research questions. For instance,studying the geographic distribution of habitats requiresfirst classifying the habitat types. Therefore, whencomparing many different schemes, it is important tounderstand the intended use or application of eachscheme and the research context.Most schemes involve different levels of informationbased on some scale or metric. This means that mostschemes are, to some degree, organized in a hierarchyof characteristics. Some schemes target one specificregion or type of substrate, whereas others extendto all underwater habitats (i.e., intertidal to the deepseafloor, and everywhere between). In almost allcases, classification schemes have an associated codethat facilitates statistical analysis and mapping usingGeographic Information Systems (GIS).7 The codesrange in complexity and in the amount of informationthey convey, but they generally are a series of numbersand letters that have specific meanings within theclassification system. A few examples of codes areprovided in the next section. No classification schemeis right or wrong, because each has been designed toaddress a unique set of questions.The following section summarizes a number ofschemes that are prominent in the Gulf of Maineregion, and a few that have received national attentionas well. The goal of each summary is to providean understanding of the function, context, form,and usefulness of each scheme in addressing theclassification needs of the Gulf of Maine Council on theMarine Environment and its partners. The summariesdo not provide in-depth description; greater detail isavailable from the original published or in-press papers.Clockwise from top left: anemones; sea stars and flounder; sea star; cod. Next page (left to right): rocky habitat;sea star; sand dollars.Level 1/Regime: differentiated by a combination of salinity,geomorphology and depth.Level 2/Formation: large physical structures formed byeither water or solid substrate within systems.Level 3/Zone: water column, littoral, or sea bottom.Level 4/Macrohabitat: large physical structures thatcontain multiple habitats.Level 5/Habitat: a specific combination of physical andenergy characteristics that creates a suitable place forcolonization or use by biota.Level 6/Biotope: the characteristic biology associated witha specific habitat.CMECS also includes a number

classification relevant to management and conservation needs in both the nearshore and offshore regions of the Gulf of Maine. The report serves to inform discussions . 3.0 Researching Marine Habitat Classification 1 "Characterization" and "description" are two more terms some-times used instead of "classification" and "mapping .