The larvae of the reef-building polychaete Lanice conchilega can make up to 15% of the summer zooplankton biomass in the North Sea. Despite their importance for reef maintenance (which positively affects the benthic community), little is known about the trophic ecology of this meroplanktonic larva. Qualitative and quantitative estimates of carbon (C) transfer between trophic levels and of fatty acid (FA)-specific assimilation, biosynthesis, and bioconversion can be obtained by compound-specific stable isotope analysis of FA. The present work tested the hypothesis that the concept of fatty acid trophic markers (FATM), widely used for studies on holoplankton with intermediate to high lipid contents, is also applicable to lipid-poor organisms such as meroplanktonic larvae. The incorporation of isotopically-enriched dietary C by L. conchilega larvae was traced, and lipid assimilation did not follow FA-specific relative availabilities in the diet. Furthermore, FAs that were unavailable in the diet, such as 22:5(n-3), were recorded in L. conchilega, suggesting their bioconversion by the larvae. The results indicate that L. conchilega larvae preferentially assimilate certain FAs and regulate their FA composition (lipid homeostasis) independently of that of their diet. Their quasi-homeostatic response to dietary FA availability could imply that the concept of FATM has limited application in lipid-poor organisms such as L. conchilega larvae.
The larvae of the reef-building polychaete Lanice conchilega can make up to 15% of the summer zooplankton biomass in the North Sea. Despite their importance for reef maintenance (which positively affects the benthic community), little is known about the trophic ecology of this meroplanktonic larva. Qualitative and quantitative estimates of carbon (C) transfer between trophic levels and of fatty acid (FA)-specific assimilation, biosynthesis, and bioconversion can be obtained by compound-specific stable isotope analysis of FA. The present work tested the hypothesis that the concept of fatty acid trophic markers (FATM), widely used for studies on holoplankton with intermediate to high lipid contents, is also applicable to lipid-poor organisms such as meroplanktonic larvae. The incorporation of isotopically-enriched dietary C by L. conchilega larvae was traced, and lipid assimilation did not follow FA-specific relative availabilities in the diet. Furthermore, FAs that were unavailable in the diet, such as 22:5(n-3), were recorded in L. conchilega, suggesting their bioconversion by the larvae. The results indicate that L. conchilega larvae preferentially assimilate certain FAs and regulate their FA composition (lipid homeostasis) independently of that of their diet. Their quasi-homeostatic response to dietary FA availability could imply that the concept of FATM has limited application in lipid-poor organisms such as L. conchilega larvae.
The larvae of the reef-building polychaete Lanice conchilega can make up to 15% of the summer zooplankton biomass in the North Sea. Despite their importance for reef maintenance (which positively affects the benthic community), little is known about the trophic ecology of this meroplanktonic larva. Qualitative and quantitative estimates of carbon (C) transfer between trophic levels and of fatty acid (FA)-specific assimilation, biosynthesis, and bioconversion can be obtained by compound-specific stable isotope analysis of FA. The present work tested the hypothesis that the concept of fatty acid trophic markers (FATM), widely used for studies on holoplankton with intermediate to high lipid contents, is also applicable to lipid-poor organisms such as meroplanktonic larvae. The incorporation of isotopically-enriched dietary C by L. conchilega larvae was traced, and lipid assimilation did not follow FA-specific relative availabilities in the diet. Furthermore, FAs that were unavailable in the diet, such as 22:5(n-3), were recorded in L. conchilega, suggesting their bioconversion by the larvae. The results indicate that L. conchilega larvae preferentially assimilate certain FAs and regulate their FA composition (lipid homeostasis) independently of that of their diet. Their quasi-homeostatic response to dietary FA availability could imply that the concept of FATM has limited application in lipid-poor organisms such as L. conchilega larvae.
Gemessen an der Dauer des Eisauftretens an der deutschen Nordseekueste, nimmt der Winter 1995-1996 den 6. Rang in diesem Jahrhundert ein. In dem beschriebenen Teil des Projektes wird das spezifische Wirkungsprofil dieses strengen Winters durch einen Vergleich mit biologischen Daten aus den Vorjahren mit milden Wintern quantitativ fuer das Plankton und Benthos des Wattenmeeres untersucht. Damit wird der Interpretationsrahmen fuer den experimentellen Teil des Projektes bereitgestellt. Den strengen Winter als natuerliches Grossexperiment nutzend, werden fuenf Hypothesen zu pelagobenthischen Wechselbeziehungen geprueft. Geplant sind parallele Messserien im Plankton und Benthos sowie vergleichende Experimente zu den Ueberlebensraten von pelagischen Larven und juvenilen Benthosstadien der Bivalvia und Polychaeta. Gefragt wird, ob die benthische Makrofauna vorrangig durch Prozesse im Pelagial in ihrer Entwicklung angestossen oder gesteuert wird oder mehr durch Reaktionsfolgen im Benthos selbst.
DYSMON II (9): Die Bildung von Sulfid ist ein regelmaessig auftretender Prozess in austauscharmen, eutrophierten Oekosystemen (z.B. Flachwasserbereiche der Ostsee). Vor dem Hintergrund der massiven 'Einwanderung' des Polychaeten Marenzelleria Viridis in die Kuestenbereiche der Nord- und Ostsee soll untersucht werden, ob die Toleranz gegenueber Sulfid bzw. die Faehigkeit zur Sulfidentgiftung eine Rolle bei seiner erfolgreichen Ansiedlung spielt. In vergleichenden Untersuchungen mit dem Polychaeten Nereis Diversicolor, einem typischen Vertreter der autochthonen Benthosfauna, soll durch Laborexperimente und Freilanduntersuchungen geprueft werden, ob Marenzelleria Viridis besser an 'Extrembiotope' angepasst ist. So soll geklaert werden, ob eine Belastung mit Sulfid Auswirkungen auf die aerobe Energieproduktion bei reduziertem Sauerstoffangebot hat oder zu einer Beeintraechtigung der osmotischen Anpassung fuehrt, insbesondere in Lebensraeumen mit niedrigem Salzgehalt (z.B. Ostsee) und ob artspezifische Unterschiede festzustellen sind. Zudem soll geprueft werden, ob Sulfid auf diese Polychaeten als Stressfaktor wirkt und die Bildung von Stressproteinen induziert.