Zeevraag: Kunnen sponzen bijdragen aan kankerbestrijding?

Van alle zeeorganismen vormen sponzen de rijkste bron aan mariene natuurlijke producten inzetbaar als geneesmiddel. Ze worden ook wel de “darmen van de oceaan” genoemd omdat ze grote aantallen micro-organismen (zoals bacteriën) bevatten die het dier beschermen tegen vijanden. Aardig meegenomen is dat de stoffen die ze aanmaken ook in tal van geneeskundige toepassingen bijzonder nuttig blijken! Zo zijn er vandaag al twee bioactieve stoffen uit sponzen op de markt waarmee kanker bij mensen kan worden bestreden

Defining habitat characteristics influencing the distribution, density and growth of plaice (<i>Pleuronectes platessa</i>) and dab (<i>Limanda limanda</i>) on west of Ireland nursery grounds

Plaice (Pleuronectes platessa, L.) and dab (Limanda limanda, L.) are among the most abundant flatfishes in the north-eastern Atlantic region and the dominant species in shallow coastal nursery grounds. With increasing pressures on commercial flatfish stocks in combination with changing coastal environments, better knowledge of population dynamics during all life stages is needed to evaluate variability in year-class strength and recruitment to the fishery. The aim of this research was to investigate the complex interplay of biotic and abiotic habitat components influencing the distribution, density and growth of plaice and dab during the vulnerable juvenile life stage and to gain insight in spatial and temporal differences in nursery habitat quality along the west coast of Ireland. Intraspecific variability in plaice diet was observed at different spatial scales and showed a link with condition, recent growth and morphology. This highlights the effect of food availability on habitat quality and the need to consider small scale variation when attempting to link habitat quality to feeding, growth and condition of juvenile flatfish. There was evidence of trophic, spatial and temporal resource partitioning between juvenile plaice and dab allowing the co-existence of morphologically similar species in nursery grounds. In the limited survey years there was no evidence that the carrying capacity of the studied nursery grounds was reached but spatial and interannual variations in fish growth indicated fluctuating environments in terms of food availability, predator densities, sediment features and physico-chemical conditions. Predation was the most important factor affecting habitat quality for juvenile plaice and dab with crab densities negatively correlated to fish condition whereas shrimp densities were negatively associated with densities of small-sized juveniles in spring. A comparison of proxies for fish growth showed the advantage of Fulton’s K for routine use whereas RNA:DNA ratios proved less powerful when short-term environmental fluctuations are lacking. This study illustrated how distinct sets of habitat features can drive spatial variation in density and condition of juvenile flatfish highlighting the value of studying both variables when modeling habitat requirements. The habitat models generated in this study also provide a powerful tool to predict potential climate and anthropogenic impacts on the distribution and condition of juveniles in flatfish nurseries. The need for effective coastal zone management was emphasized to ensure a sustainable use of coastal resources and successful flatfish recruitment to the fishery

Growth and habitat requirements of juvenile flatfish at nursery grounds in Galway Bay, Ireland

Coastal zones are essential nursery habitats for most juvenile flatfish species. Fish stocks are highly dependent on suitable coastal habitat features for obtaining food, shelter, and rapid growth during the vulnerable juvenile life stage. Understanding the ecological habitat requirements for juvenile flatfish is important in determining their abundance and to reliably predict potential impacts of changing coastal ecosystems on fish stocks. The present study assesses the influence of habitat characteristics on the growth and abundance of juvenile dab and plaice in four nursery areas within Galway Bay, Ireland. Field sampling was carried out in summer 2008 using a beam trawl for the collection of flatfish and a van Veen grab for the collection of sediment. The distribution and abundance of the juvenile flatfish was assessed in relation to biotic (predator–prey abundance) and abiotic (sediment size, organic content, depth, temperature, and salinity) habitat features. The condition and growth of flatfish were compared in different nursery areas and a model of habitat requirements for juvenile plaice and dab was developed. Significant variability of the measured characteristics was observed between nursery areas and high-quality nursery areas for dab and plaice were identified. These results will act as the basis for mapping of essential flatfish habitats in Galway Bay