Monitoring MarineLife from SpaceEnvisat Experience in Chile

Monitoring MarineLife from SpaceEnvisat Experience in Chile

T he use of satellite data, primarily frominstruments aboard ESA’s Envisat, togetherwith in situ sea measurements, provides a

powerful tool for monitoring the environmentalconditions of coastal waters and the health ofsouthern oceans. Ocean monitoring by satelliteremote sensing to protect public health and thefishing industry started in southern Chile in2002. Last year, a major advance was achievedwhen Envisat data products were received innear-realtime, allowing early detection ofmarine conditions that favoured harmful algalblooms and the growth of dangerous bacteria.

Dramatic Events Detected from Space South of Chiloe Island, where the PacificOcean meets one of the most beautifulareas of Chilean Patagonia, some micro-algal cells grew and proliferated in theGulfs of Ancud and Corcovado.Measurements in the sea could notreveal the extent but, from space, satelliteinstruments detected how this populationof micro-organisms evolved. Theseorganisms are lethal to human beings indoses of only 80 micrograms per gram ofshellfish. After two people died and ahundred were poisoned in 2002, theharvesting of shellfish was forbidden inthe whole area and the Presidentdeclared a national disaster.

This type of event tends to occur mostyears. It is normally well documented bythe press, particularly because the peopleof the region depend on natural marineresources and agriculture. Nowadays,the SeaSTAR, Terra, Aqua, ERS-2 andEnvisat satellites can study the wholesouthern Chilean region, where the

Cristina Rodríguez & Christian HaagMariscope Chilena Ltda, Puerto Montt, Chile

Maurizio FeaScience and Applications Dept., Directorate ofEarth Observation Programmes, ESRIN,Frascati, Italy

Héctor GutierrezApplications of Earth Observation, ChileanSpace Agency, Santiago, Chile

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Puerto Montt has the highest growthrate in Latin America. For the first timesince 2002, this region is being observedfrom space.

Having established the usefulness ofsatellite data in monitoring oceansurface conditions, significant progressis now being made in relating satelliteobservations to the bulk characteristicsof sea water when they are properlyintegrated with underwater measure-ments, particularly in ocean models.

This is very important because, aswith humans, the health of marine lifedepends largely on environmentalconditions. Very often, this dependencyis critical and even a minor change in thevalue of a physical or chemical parameter,such as temperature or oxygen content,can lead to dramatic consequences. Thatis why satellite coastal monitoring isindispensable, particularly in regionswith exponential economic growth intourism or industrial activity, and wheresystematic environmental monitoring isvery difficult owing to complex regionalgeography.

Characteristics of the Project AreaThe western Patagonian coast offersideal conditions for salmon farming, tothe point where the country became theworld’s top producer by the end of 2004.In addition, shellfish and algae farmingis growing further south, in Region XIof Chile, where the economic prospectsindicate explosive development in thenext few years.

The area of investigation is in thesouth-eastern part of the Pacific Ocean.Here, the coast of the South Americancontinent is broken up into thousands ofislands, which create a special environ-ment of bays, fjords and channels with acomplex geomorphology. The oceandynamics produce great environmentalvariability, enhanced by the stronginfluence of fresh water from heavyrainfalls and continental glaciers. Theregion has hydrographical and ecologicalpeculiarities that are not wellunderstood, but which determine thebiological variability of its marinecommunities.

The eastern boundary of the PacificOcean’s general circulation is stronglyinfluenced by the atmosphere’s dynamics.These meteorological conditions causegreat variability in the surface windstructure. Offshore, the winter circulationfrom the east subdivides into twobranches: the Humboldt Current offPeru and Chile, and the current off CapeHorn. The first is responsible forprobably the most important upwellingregion on Earth; the high inorganicnutrient influx from deeper levels createsthe conditions for a major fishing area.

The Humboldt Current flows frombelow 40ºS, up to the equatorial regionin two branches: oceanic and coastal.Under the coastal branch at depths of100 m to 400 m there is the equatorialcurrent, characterised by low oxygenconcentration (anoxia, or severehypoxia). The distribution of thesewater masses has been measured fromthe north of Peru down to the latitudesof Chiloé Island.

Some researchers have found anoxicconditions in the area damaging to

aquaculture, relating the conditions tothese water masses that occasionallyarrive during parts of the year. Theseare new areas for future oceanographicinvestigation.

Envisat Helps to Monitor Ocean ConditionsCombining data in the visible andinfrared spectral bands from Envisat’sMERIS (Medium Resolution ImagingSpectrometer) and AATSR (AdvancedAlong-Track Scanning Radiometer)instruments, respectively, has made itpossible to describe dynamic aspects ofboth the open ocean and the Gulf ofCorcovado in Chile’s Region X. Some ofthe most important observationsidentified areas where thermal fronts inthe ocean originate, with strongtemperature and probably salinitygradients. These zones retain nutrientsand provide phytoplankton withoptimal conditions for development.

These areas, as well as other locations,are risk areas for the development ofmarine algae blooms. Depending on thecomposition of the phytoplankton

Earth Observation

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Phytoplankton concentration derived from Envisat MERIS measurements of 9 February 2005. Red is equivalent to about 30 mg percubic metre of seawater. Strong gradients in the fronts around Chiloé Island match the sightings of blue whales and other cetaceans

population, these blooms can beharmful to humans, and they aregenerally harmful to fish farming. It hasalso been possible to develop risk mapsfor other marine agents, as detectedduring the outbreak of Vibrioparahaemolyticus in the southernsummers of 2004 and 2005.

Harmful Algal BloomsMicro-algal blooms are naturalphenomena known since ancient times.However, they have increased infrequency and now appear more widelyaround the planet. Furthermore, thegrowth in human population andcoastal settlements means that thesocio-economic impact of thesephenomena has become more dramaticin recent decades. In Chile, a majorexample is the paralytic poisoning ofmarine shellfish, first seen in PuntaArenas in 1972.

During 2002, an outbreak ofAlexandrium catenella was detected inthe research area and was responsiblefor 73 poisonings and two deaths. Theoutbreak affected an area where 60% ofthe shellfish are destined for export. Asa result, the zone to the south of 43ºSwas closed for shellfish extractionduring 2002 and 2004. An intensecontrol programme is now under wayfor marine products, and a permanentsanitary area has been established thatprohibits the export of shellfish productswithout certification to national andinternational destinations.

There is a clear need for a deeperunderstanding of the toxic micro-algaloutbreaks in the area.

MERIS and AATSRThe MERIS instrument on Envisat hasseveral mission goals, one of which is togenerate data for the analysis of thespatial and temporal distributions ofmarine biological activity in the surfacelayers of the ocean. AATSR’s key task isto provide data in the thermal-IR band,to generate sea-surface temperaturemaps.

The results from this project confirmthat both instruments have achieved

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those objectives. In the south of Chile,the combined use of MERIS andAATSR data provides early alerts oflocal and regional algal blooms, as wellas of other marine phenomena.However, this is not an easy orautomated task, because it requires adetailed knowledge and experience ofinterpreting satellite data, integratedwith other information from differentsources.

Envisat data were acquired as part ofan ESA Category 1 project. During thepilot phase, data were received with atime delay of several weeks. After theimplementation of new ground segmentprocedures by ESA, images werereceived from the servers at ESRIN (I)and Kiruna (S) in near-realtime, within3 hours of acquisition by Envisat.Thanks to those improvements, it waspossible to monitor large coastal areasin one of the remotest parts ofPatagonia, where rapid social andeconomic development can be affectedby natural phenomena.

The support provided by satelliteinformation for daily activities in the seaalso led to the parallel development ofsmall pilot applications. These wereaimed at evaluating and then demon-strating the usefulness of remote sensingfor the aquaculture industry,insurance companies andgovernmental organisations inmonitoring potential toxicoutbreaks through theconsumption of tainted seafood.

Benefits from New Technologies Research into phytoplanktonmonitoring using remote sensingbegan in 2002 with the use ofSeaWiFS and then MERIS andMODIS (Moderate ResolutionImaging Spectroradiometer onTerra and Aqua) satelliteproducts, with the purpose ofapplying sea-surface temperatureand ocean-colour information.

Algal bloom of Gymnodinium chlorophorum,occurring every year since 2003 and detectedby MERIS on 26 April 2005

Initial results indicated that it waspossible to focus research funding onselected specific areas.

Later, the use of Envisat satellite datademonstrated that it is possible topredict the occurrence of critical algalbloom periods, in order to mitigate thedamage to aquaculture. Advancewarnings of only 4 days allow enoughresponse to reduce the effects of an algalbloom. Experimental early warningssent to selected companies enabled themto make key decisions in time. Forexample, ‘smolts’ (young salmon) werenot introduced into areas affected by thealgal bloom: a small delay at this stageof the production process avoided theloss of several million dollars later on.

In addition, Envisat observationsdetected areas of maximum phyto-plankton activity in a zone wheremarine mammals such as the blue whalehad been recently seen. This zone wasthus proposed as a new protected marineecosystem. MERIS images have shownhigh phytoplankton concentrationsconnected with thermal fronts detectedby AATSR. These observations fit wellwith the positions of the whalesightings.

Threats to AquacultureAquaculture in southern Chile mainlyconcerns the production of salmon andshellfish. Algal blooms of differentspatial and temporal characteristicshave been observed. In some cases, theseexplosive growths of micro-algae lastedfor several weeks, as with the bloom of anew species, Gymnodinium chlorophorum,during southern autumn 2005. Whethertoxic or not, these micro-algae are solelyresponsible for changes in the feedingbehaviour of fish, slowing their growth.

After the exponential growth of algae,bacterial development follows throughdecomposition of the algae. Metabolicreactions reduce the concentration ofdissolved oxygen (hypoxia) in theseawater, killing the fish. In the case ofthe shellfish industry, the threat comesfrom species carrying toxins that thenaccumulate in the shellfish. Paralytic,diarrhoeic and amnesic toxins have alsobeen found between Regions III and XIIin Chile, with some isolated cases in thecentral zones of the country.

In 1993, the amount of exported bluemussels (Mytilus chilensis) was 3000 t,increasing to 60 000 t in 2003, and anestimate of 100 000 t for 2008. Carefulmanagement of the exploited areas isrequired for sustainable development.

For this, it is necessary to integrate allthe methods available for monitoringcoastal zones, in particular multi-disciplinary programmes involvingsatellite data.

Earth Observation and EpidemiologyIn 2003, some bacterial species weredetected for the first time in the area.One was identified as V. parahaemolyticus,responsible for more than 1500poisonings during the southern summerof 2004 and more than 10 000 cases in2005, including one death. The origin ofthese bacteria in the region was probablyballast water spilling from othercountries. This hypothesis is supportedby the results of the genetic analysis ofthe bacteria strains found in Chile, whichcorresponds to the pandemic complexseen in some Asian countries after 1996.

V. parahaemolyticus is a bacterium ofthe same genus as V. cholera, which livesin marine environments. Several para-meters influence its life cycle; watertemperature has been demonstrated tobe one of the most important factorsthat accelerate its growth. EnvisatAATSR data showed the rise of sea-surface temperature during January2004 in that area. The seafood areas atmost risk of being infected with thisbacterium were determined through theanalysis of AATSR and ancillary data.Eventually, remote-sensing data helpedlocal health authorities to establish awell-defined region of increased risk,and to avoid closing low-risk areas.

Unfortunately, during the southernsummer of 2005, preventive action waslimited to advising people to avoid rawshellfish during the critical period. Nosanitary barriers were established, andno restrictions were imposed on theshellfish extraction by area; such adifficult decision would have stronglyaffected local families dependent on theindustry. This led to more than 10 000cases of poisoning all over the country,and one death. The region is a key zonefor extracting and exporting shellfish.This could explain how the outbreakrapidly turned into a national epidemic.

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Sea-surface temperature derived from Envisat AATSR data of 21 February 2004. The thermal situation favoured theexponential growth of V. parahaemolyticus. The highesttemperature (ºC) is shown in red

Envisat data helped local authorities to define the region of highrisk of poisonings and to avoid closing low-risk areas

fish starvation in the cages. The amountof dead salmon is often so high that theload on the bottom of the net is toogreat for the installation to remainafloat. When the nets collapse and sink,they damage the surrounding nets.During these events, divers work forhours in the cages, often not followingthe necessary decompression proceduresafterwards. Serious decompressionaccidents sometimes kill the divers. Theinsufficient number of divers to copewith these emergencies in the moreremote regions of southern Chile meansthat the situation is not improving.

The use of satellite information to warnof an algal bloom can help to reduceaccidents and losses, as demonstrated in2005 through the use of Envisat MERISand AATSR data. This is an importantexample of the many ways in whichsatellite information is of real daily benefitto people around the world.

ConclusionThe integrated use of satellite and in situsea measurements is an important aid todecision-making for public and industryadministrators. However, data integrationand interpretation by skilled professionalsis a fundamental prerequisite given themajor socio-economic and public healthimpacts of their decisions. e

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Sea-surface temperatures derived from AATSR data of 9 February 2005, some days before theexponential growth in poisonings from raw shellfish consumption

Evolution of the number of poisonings during the 2005 outbreak of V. parahaemolitycus

Through remote sensing, it waspossible to demonstrate that the watertemperature was above 18ºC on9 February 2005 around the coastalzone with the highest populationdensity, which is also the principal areaof shellfish extraction. The temperaturecould have been one of the main reasonsfor the exponential growth of thebacteria. The Health and ConsumerProtection Directorate General of theEuropean Commission recommendsavoiding the extraction of marineresources during the critical period insummer. This recommendation shouldbe considered in equivalent regionsbeyond Europe.

By using satellite data, it is possible toforecast the most critical periods ofcontamination up to a week in advance.That certainly allows time to create atleast temporary sanitary barriers,

minimising the effects on the workers in the seafood industry, and on theregional and national population. Thistechnology adds value to the exportedproducts, in that it provides a sort ofquality certification to the monitoringconducted during the extraction period.

Novel Application to Human HealthAnother recent application of satellitedata with a positive effect on publichealth is the prevention of decompressionsickness in working divers of the region.The link between divers and satellitesmay appear surprising, but it confirmsthe value of space data in multi-disciplinary applications.

One of the routine tasks of divers inthe salmon industry is the daily clearingof dead salmon from nets to preventdisease in the remaining fish. An averageof 10 salmon are taken out of each cageevery day. A single diver normally doesthe job in up to 30 cages per farm. Thislevel of effort already affects the diver’shealth owing to the repetitive diving andthe accumulation of nitrogen bubbles inthe body.

During and after algal bloom events,these divers have to cope with massive

Routine work of divers in the salmon industry. Remote sensingdata help to plan their daily work and prevent decompressionsickness