Food depletion in mussel cultivation has been rarely studied and seldom demonstrated. In this study, concentrations of phytoplankton in and around a blue mussel Mytilus galloprovincialis raft culture unit in the Ría de Vigo were measured during a 2 wk study period in July 2004. Flow direction and current speed were measured using an Aanderaa current meter and fine-scale Acoustic Doppler Velcimeter probes at different positions in the raft. Flow speeds were reduced compared to outside the raft, but a clear tidal signal and significant flow velocities could still be observed inside the raft. At the upstream corners of the raft, a zone of high turbulence but reduced advection was observed. Concentrations of chlorophyll a (chl a) were measured on 3 different spatial scales. On a macro-scale, fluorescence profiles were taken inside and outside the raft on several occasions and there was depletion of chlorophyll inside the raft corresponding to ~80% of the outside concentration, whereas there was no depletion below the ropes. On a meso-scale, from just upstream to just downstream of the raft, fluorescence profiles, as well as water samples, at several depths revealed similar depletion, however, with larger depletion of size-fractionated chl a >2 µm. On a micro-scale, water was sampled within 20 cm of the ropes using siphon mimics. In the middle of the raft, concentration profiles towards the mussel ropes could be observed at 2 depths, whereas less clear profiles were observed on the turbulent upstream corner. The present study documents food depletion in a mussel culture and emphasizes the importance of physical forcing and phytoplankton composition for food availability

This paper presents the results of an internationally coordinated contingent valuation study on the benefits of reducing marine eutrophication in the Baltic Sea according to current policy targets. With over 10,500 respondents from the nine coastal states around the sea, we examine public willingness to pay (WTP) for reduced eutrophication and its determinants. There are considerable differences in mean WTP between countries, with Swedes being willing to pay the most and Latvians the least. The aggregate annual WTP is approximately €3600 million. In addition, we find that countries are heterogeneous in terms of the effects of income, attitudes and familiarity on WTP. Income elasticities of WTP are below 1 for all countries, ranging between 0.1 and 0.5. Attitudes and personal experience of eutrophication are important determinants of WTP, but the specific effects differ between countries. The findings can be used in economic analyses for the European Union (EU) Marine Strategy Framework Directive and to justify additional eutrophication reduction measures in the Baltic Sea.

Distribution, production and grazing of the copepod community were investigated in the northern Aegean Sea, which is characterized by a permanent thermohaline front. Cruises were conducted along a transect crossing the frontal area during spring and late summer. Biomass and production of autotrophs were measured by size fractionation and heterotrophic nanoflagellates and ciliates were also studied. Copepod biomass, production and grazing impact on the phytoplankton and ciliate populations were estimated. The copepod community was sampled with a 45 μm net to include the smallest species and their developmental stages. The size, structure and distribution of the phytoplankton imply that most carbon was fixed by picoplankton during both seasons and throughout the study area. The partitioning of carbon among the different plankton compartments was not a broad-based pyramid and the biomass of heterotrophs was higher than that of autotrophs, except in the non-frontal region during spring. Copepod biomass was substantially higher in the frontal area. Our results showed that the small-sized copepods (calanoids and cyclopoids) dominated in terms of biomass and production, but also had a greater influence on the efficiency of the trophic coupling between the primary producers and the protozooplankton than the larger species, stressing their importance in the northern Aegean Sea and the Eastern Mediterranean in general.