Detailed visual seabed survey at drilling site 7218/11-1
Detailed visual seabed survey at drilling site 7218/11-1
Detailed visual seabed survey at drilling site 7218/11-1
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Table of Contents<br />
PREFACE ................................ ................................ ................................ ................................ ..........................4<br />
1 INTRODUCTION ................................ ................................ ................................ ................................ .............5<br />
1.1BACKGROUND................................ ................................ ................................ ................................ ...................5<br />
1.2SUMMARYOFPREVIOUSURVEYSATDARWIN................................ ................................ ................................ .........5<br />
1.2.1Baseline<strong>survey</strong>20<strong>11</strong>................................ ................................ ................................ ............................. 5<br />
1.2.2Additionalstudies2012................................ ................................ ................................ .........................6<br />
1.3AIMSANDCHALLENGES FORPRESENTSURVEY................................ ................................ ................................ ..........7<br />
2 MATERIALSANDMETHODS................................ ................................ ................................ ..........................8<br />
2.1VESSELANDNAVIGATION................................ ................................ ................................ ................................ .....8<br />
2.2ROV,VIDEOANDSTILLIMAGES................................ ................................ ................................ ............................. 8<br />
2.3SURVEYTRACKANDWAYPOINTS................................ ................................ ................................ ..........................10<br />
2.4OBSERVATIONLOGSANDEVENTLOGGING................................ ................................ ................................ .............<strong>11</strong><br />
2.4.1Stepstakento addresschallenges................................ ................................ ................................ .......<strong>11</strong><br />
2.4.2Eventlogging................................ ................................ ................................ ................................ .......12<br />
3 ABOUTSPONGESANDCHALLENGES FORASSESMENT................................ ................................ ...............13<br />
3.1OSPARHABITATCLASSIFICATI ONOFSPONGES ................................ ................................ ................................ .......13<br />
3.2SPONGESIN THESOUTH-WESTERNBARENTSEA................................ ................................ ................................ ....13<br />
3.3ABOUTSPONGES IN GENERAL................................ ................................ ................................ .............................. 16<br />
3.4RED-LISTEDSPONGES ................................ ................................ ................................ ................................ ........18<br />
3.5SPONGESASECOSYSTEMENGINEERS ................................ ................................ ................................ ....................19<br />
4 ABUNDANCEQUANTIFICATIONCHALLENGES - CASESTUDYSALINA,JUKSAANDDARWIN.........................21<br />
4.1GENERAL................................ ................................ ................................ ................................ ........................21<br />
4.2CURRENTAPPROACHES – ASSESSINGCOVERAGE ................................ ................................ ................................ .....22<br />
5 RESULTSANDDISCUSION................................ ................................ ................................ ...........................25<br />
5.1GENERALOBSERVATIONS ................................ ................................ ................................ ................................ ...25<br />
5.2SEAFLOORCONDITIONS................................ ................................ ................................ ................................ .....26<br />
5.2.1Sedimentcomposition................................ ................................ ................................ .........................26<br />
5.2.2Litter andotherhumanimpacts................................ ................................ ................................ ..........26<br />
5.2.3Seashorealgaeandfishfalls................................ ................................ ................................ ................27<br />
5.3DISTRIBUTIONMAPSANDSELECTED IMAGES................................ ................................ ................................ ..........27<br />
5.3.1Generaloverview................................ ................................ ................................ ................................ . 27<br />
5.3.2Plotsof spongedistributionanddensity................................ ................................ .............................. 28<br />
5.3.3Overallassessmentof spongedensities<strong>at</strong> the Darwin<strong>site</strong>................................ ................................ . 36<br />
5.3.4Integr<strong>at</strong>edassessment – baseline<strong>survey</strong>anddetailed<strong>site</strong><strong>survey</strong>................................ ......................37<br />
5.3.5Dominantspongespeciesrecordedin the current<strong>survey</strong>................................ ................................ ...38<br />
5.3.6Trawltracks................................ ................................ ................................ ................................ .........44<br />
5.3.7Generalimpressions(images)................................ ................................ ................................ ..............45<br />
5.4ENVIRONMENTALCOSTSANDBENEFITSFORDISCHARGESCENARIOS ................................ ................................ ............48<br />
5.4.1Dischargescenarios................................ ................................ ................................ ............................. 48<br />
5.4.2Depositionscenariosrel<strong>at</strong>edto areaof impactto sponges................................ ................................ . 50<br />
5.4.3Compar<strong>at</strong>iveassessment ................................ ................................ ................................ .....................56<br />
5.5ASSESSINGVULNERABILI TYOFSPONGEASSEMBL AGESTODRILLINGDISCHARGES ................................ ............................ 56<br />
5.5.1Wh<strong>at</strong> do sensitivityandvulnerabilitymean?................................ ................................ .......................56<br />
5.5.2Ongoingandplannedexperimentalandin situ workon assessingsensitivityof spongesto <strong>drilling</strong><br />
cuttings................................. ................................ ................................ ................................ ........................57<br />
6 REFERENCES ................................ ................................ ................................ ................................ .................58<br />
APPENDICES ................................ ................................ ................................ ................................ ....................60<br />
<strong>Detailed</strong> <strong>site</strong> <strong>survey</strong> <strong>at</strong> PL531 Darwin<br />
Akvaplan-niva AS Rapport 6051 - 1