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Ber. Polarforsch. 201 (1996) ISSN 0176 - 5027 Katrin Iken

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Ber. Polarforsch. 201 (1996) ISSN 0176 - 5027 Katrin Iken Ber. Polarforsch. 201 (1996) ISSN 0176 - 5027 Katrin Iken Alfred-Wegener-Institut füPolar- und Meeresforschung Postfach 12 01 61 Columbusstraß D - 27568 Bremerhaven Die vorliegende Arbeit ist die im wesentlichen unverändert Fassung einer Dissertation, die in der Sektion Biologie I bei Prof. Dr. W. Arntz angefertigt und 1995 dem Fachbereich 2 (BiologieIChemie) der UniversitäBremen vorgelegt wurde. Inhaltsverzeichnis ZUSAMMENFASSUNG .................................................................................... IV SUMMARY ......................................................................................................... VI 1. Einleitung ............................................................................................................1 2. Untersuchungsgebiet .........................................................................................4 2.1 Geographische Lage ...............................................................................4 2.2 Topographie ...........................................................................................4 2.3 Hydrographie .........................................................................................6 2.4 Zonierung antarktischer Makroalgen .....................................................6 2.5 Zeitpunkt und Ort der Probennahmen ....................................................7 3. Nahrungsbeziehungenzwischen Herbivoren und Makroalgen: Wer fri§was? ..................................................................................................10 3.1 Material und Methoden ..........................................................................11 3.1.1 Algen-Netzproben ......................................................................11 3.1.2 Magenanalysen zur Identifizierung von Herbivoren .................12 3.1.2.1 Nacella concinna ..............................................................-12 3.1.2.2 Laevilacunaria antarctica ..................................................13 3.1.2.3 Nereidae ..............................................................................15 3.1.2.4 Gondogeneia antarctica .....................................................16 3.1.2.5 Bovallia gigantea ...............................................................17 3.1.2.6 Plakarthrium punctatissimum ............................................18 3.1.2.7 Odontaster validus .............................................................18 3.1.2.8 Notothenia neglecta ............................................................19 3.2 Ergebnisse ..............................................................................................24 3.2.1 Algen-Netzproben ......................................................................24 3.2.2 Auswahl der Tiere füNahrungsanalysen ..................................32 3.2.3 Nahrungsanaly sen ......................................................................33 3.2.3.1 Nacella concinna ................................................................33 3.2.3.2 Laevilacunaria antarctica ..................................................37 3.2.3.3 Nereidae ..............................................................................40 3.2.3.4 Gondogeneia antarctica .....................................................41 3.2.3.5 Bovallia gigantea ...............................................................46 3.2.3.6 Plakarthrium punctatissimum ............................................47 3.2.3.7 Odontaster validus .............................................................48 3.2.3.8 Notothenia neglecta ............................................................50 3.2.4 Nahrungsbeziehungen ................................................................64 3.3 Diskussion ..............................................................................................66 3.3.1 Methodendiskussion ...................................................................66 3.3.1.1 Algen-Netzproben ..............................................................66 3.3.1.2 Nahrungsanalysen .............................................................. 67 3.3.2 Nahrungsbeziehungen von Makroalgen und Herbivoren ..........76 3.3.2.1 Algen-Netzproben .............................................................. 76 3.3.2.2 Herbivoren-Spektrum ......................................................... 78 3.3.2.3 Trophische Interaktionen ....................................................80 L Konsumtion von Laevilacunaria antarctica ..................................................95 4.1 Material und Methoden .......................................................................... 97 4.1.1 Probennahme und Hälterunvon L. antarctica ......................... 97 4.1.2 Einteilung in Größenklassbei L. antarctica ...........................97 4.1.3 Probennahme und Hälterunder Makroalgen ........................... 98 4.1.4 Fraßtestzur Bestimmung der Konsumtion ...............................99 4.1.5 Abundanz von L. antarctica und relative Biomasseanteile einzelner Makroalgenarten .......................................................100 4.1.6 Berechnung der Konsumtion von L. antarctica ....................... 101 4.2 Ergebnisse ............................................................................................105 4.2.1 Mittleres Kotballengewicht pro Größenklas......................... 105 4.2.2 Egestion und Konsumtion ....................................................... 106 4.2.3 Gesamtkonsumtion von L. antarctica an Makroalgen im EU-und Sublitoral des Pefion 1 ................................................111 4.3 Diskussion ............................................................................................119 4.3.1 Methodendiskussion .................................................................119 4.3.1.1 Bestimmung der Konsumtion ...........................................119 4.3.1.2 Auswahl der Untersuchungsorganismen ..........................121 4.3.1.3 Fraßexperimentzur Bestimmung der Konsumtion von L. antarcfica ..............................................................122 4.3.2 Konsumtion von L. antarctica an verschiedenen Makroalgenarten ......................................................................123 4.3.3 Vergleich der Konsumtion von L. antarctica mit anderen Gastropoden ................................................................123 5. Fraßschutzmechanismebei antarktischen Makroalgen ..........................127 5.1 Material und Methoden ........................................................................128 5.1.1 Cm-Analy se .............................................................................128 5.1.2 Veraschung ...............................................................................129 5.1.3 Chemische Analyse von Algenextrakten .................................129 5.1.4 Fraßexperimentmit homogenisierten Algen ..........................134 5.2 Ergebnisse ............................................................................................136 5.2.1 Cm-Verhäitni......................................................................... 136 5.2.2 Organischer Gehalt von Makroalgen .......................................139 5.2.3 Chemische Analyse von Sekundärrnetabolite in Algenextrakten ......................................................................141 5.2.4 Fraßexperimentzur Uberprüfunstruktureller Fraßschutzmechanismevon Makroalgen ...............................147 5.3 Diskussion ............................................................................................ 149 5.3 1 Methodendiskussion ................................................................. 149 5.3.2 Fraßschutzmechanisme.......................................................... 150 5.3.2.1 Nährwerantarktischer Makroalgen ................................. 151 5.3.2.2 Sekundärmetabolitin antarktischen Makroalgen ........... 155 7 .Literaturverzeichnis ......................................................................................166 8. Anhang ............................................................................................................189 Danksagung ........................................................................................................206 ZUSAMMENFASSUNG Im Rahmen dieser Arbeit wurde die Bedeutung der Makroalgen fiir das Nahrungsnetz eines antarktischen Flachwassersystems untersucht. Die Arbeiten wurden in der Potter Cove auf der King George-Insel, der Hauptinsel der der Antarktischen Halbinsel vorgelagerten Süd-Shetland-Inselndurchgeführt Die Schwerpunkte lagen dabei auf der qualitativen und quantitativen Erfassung der Makroalgen in der Nahrung wichtiger pflanzenfressender Tiere (Herbivore). Außerde standen Fragen nach mögliche Fraßschutzmechanismeder Algen im Vordergrund. Folgende Ergebnisse lassen sich aus den Untersuchungen zusammenfassen: - Makroalgen könne - entgegen dem bisherigen Wissen uber Nahrungsnetze in antarktischen Gewassern - in Flachwassersystemen der Antarktis einen entscheidenden Anteil an der Nahrung von Herbivoren haben. Magenanalysen und Fraßexperiment zeigten, da Gastropoden, Amphipoden, Polychaeten, Isopoden und Fische, möglicherweisauch Echinodermen, als Herbivore an Makroalgen fressen. - Neben Generalisten, die eine Vielzahl von Algenarten als Nahrungsquelle nutzen (z.B. Laevilacunaria antarctica (Gastropoda) und Gondogeneia antarctica (Amphipoda)), haben sich bei einigen Herbivoren auch Spezialisierungen auf wenige Algenarten herausgebildet (z.B. Nacella concinna
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