Description: 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.

Description: 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.

Description: This dataset comprises data from two experiments analysed with two different tools, a FlowCam and a microscope. The heterotrophic dinoflagellate Oxyrrhis marina was subjected to different feeding treatments (starved, or fed with either F/2 nutrient reach, nitrogen-limited, or phosphorus-limited phytoplankton of the species Rhodomonas salina). The carbon:nitrogen:phosphorus stoichiometry of the different phytoplankton and dinoflagellate cultures was measured. The nitrogen-limited and phosphorus-limited phytoplankton were mixed and the mixture was offered as food to the dinoflagellates previously fed on either nitrogen-limited, or phosphorus-limited phytoplankton. The selective feeding of the dinoflagellate on the two mixed algal qualities was measured.

Description: Cellular elemental stoichiometry of two phytoplankton species, Rhodomonas salina and Teleaulax sp., grown in nutrient replete F/2 medium and in P-limited conditions, as well as cellular elemental stoichiometry of the heterotrophic dinoflagellate Oxyrrhis marina fed with these four types of phytoplankton individually.

Description: The ongoing acidification process of the oceans is likely to have consequences for many marine biota. Although evolutionary responses are expected during persisting environmental change, little is known about the adaptability of copepods. Therefore, we set up a 3 ½ years long selection experiment, culturing Acartia tonsa populations in water treated with 200 and 800 µatm pCO2, feeding them with algae grown in f/2 medium under 200 µatm pCO2 and in f/2 N P medium under 800 µatm pCO2. After three reciprocal transplant experiments we measured copepods' developmental rates, carbon to nutrient ratios, egg production and hatching rates. Under high CO2 conditions, stoichiometric discrepancies between the requirements of A. tonsa and its food resulted in a significantly decreased developmental rate independent from the selective history. After one year, these discrepancies appeared alleviated by an optimised homeostasis regulation of the copepods, indicating a high body stoichiometry regulation plasticity. Egg production and hatching success were unaffected by the experimental conditions, however, results indicated a premature hatching of eggs from females with a high CO2 selective history. Over the experimental period we did not detect any beneficial adaptations of the copepods cultured under high CO2 conditions of elevated seawater pCO2 and associated food quality reduction. Towards the end of the experiment, copepods cultured under elevated pCO2 and fed with high CO2 algae, showed an increased body mass and decreased prosome length. Such physiological changes could have profound long term consequences for marine copepods, food web interactions, and ultimately ecosystem structures and functions.

Description: The copepod Temora longicornis depends on constant prey availability. Given that climate change may induce food regime shifts, our research goal was to understand copepod energy allocation in relation to diet quality. The working hypothesis was that Temora performs better on the diet whose elemental ratio is closest to its own. Diatoms (Diat) and dinoflagellates (Dino) cultured in nutrient-replete (+) and nitrogen-depleted (-) conditions were fed to the copepods. Ingestion, respiration, excretion, and egg and faecal pellet production rates were measured. Carbon (C) and nitrogen (N) budgets were built to investigate differences in dietary C and N partitioning. Copepods fed with nitrogen-depleted diatoms (Diat-), which had the most different C:N ratio to that of T. longicornis, had high metabolic losses and low growth. In contrast, copepods fed with nitrogen-rich dinoflagellates (Dino+) of closer C:N ratio had high metabolic losses, but the highest investment into somatic and reproductive tissue. The results indicate that, under the current climate scenario and nutrient-replete conditions, dinoflagellates are a better food source for T. longicornis. Furthermore, ingestion, respiration, and faecal pellet integrity are adversely affected by low quality food; and egestion is a main pathway in copepods for eliminating excess carbon.

Description: 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.