Mussel production and Water Framework Directive targets in the Limfjord, Denmark: an integrated assessment for use in system-based management

Growth of human activities often conflict with nature conservation requirements and integrated assessments are necessary to build reliable scenarios for management. In the Limfjord, Denmark's largest estuary, nutrient loading reductions are necessary to fulfill EU regulations criteria, such as the Water Framework Directive (WFD). Cuts in nutrient loadings do not necessarily result in corresponding reductions in eutrophication impacts or in improving primary and higher trophic-level production. Similarly, the socioeconomic consequences of a mussel fishery and aquaculture production are complex and hard to predict. This study focuses on the usefulness of a System Approach Framework (SAF) implementation for stakeholder understanding of complex systems and development of sustainable management. Ecological-social-economic (ESE) model simulations clearly demonstrated the potential problems of WFD implementation for mussel fishers and mussel farmers. Simulation of mussel fishery closures resulted in a tenfold increase in the hitherto fishable mussel biomass and a similar decrease in the biomass of shallow-water mussels and medium-sized ones in deep water. A total closure of the mussel fishery could result in an annual profit loss of ~6.2 million. Scenario simulation of the introduction of one, two, three, and four mussel culture farms of ~19 ha showed that the introduction of line-mussels would decrease the biomass of wild mussels both in shallow and deep waters, affecting the catch and profit of fishers. The SAF, which included consultation with stakeholders at all stages, differs from the traditional public consultation process in that (1) communication was verbal and multilateral, (2) discussion among stakeholders was facilitated, and (3) stakeholder opinions and priorities formed the focus of the ESE assessment

Coupling bacterioplankton populations and environment to community function in coastal temperate waters

Bacterioplankton play a key role in marine waters facilitating processes important for carbon cycling. However, the influence of specific bacterial populations and environmental conditions on bacterioplankton community performance remains unclear. The aim of the present study was to identify drivers of bacterioplankton community functions, taking into account the variability in community composition and environmental conditions over seasons, in two contrasting coastal systems. A Least Absolute Shrinkage and Selection Operator (LASSO) analysis of the biological and chemical data obtained from surface waters over a full year indicated that specific bacterial populations were linked to measured functions. Namely, Synechococcus (Cyanobacteria) was strongly correlated with protease activity. Furthermore, seasons exerted a profound effect on the substrate utilization capacity and composition of the communities. However, the pattern of substrate utilization capacity could not be directly linked to the community dynamics. The overall importance of dissolved organic matter (DOM) parameters in the LASSO models indicate that bacterioplankton respond to the present substrate landscape, with a particular importance of nitrogenous DOM. The analyses exemplifies that high taxonomic resolution can reveal links between individual populations and bulk bacterioplankton functions, and that for some taxa rRNA analyses are a necessary descriptor when attempting to correlate functions with communities. The reconciliation of patterns from two different systems indicates that the identified drivers of bacterioplankton community functions may be of broader relevance in coastal temperate waters

Anti-cyanobacterial activity of Moringa oleifera seeds

Filtrates from crushed Moringa oleifera seeds were tested for their effects on growth and Photosystem II efficiency of the common bloom-forming cyanobacterium Microcystis aeruginosa. M. aeruginosa populations exhibited good growth in controls and treatments with 4- and 8-mg crushed Moringa seeds per liter, having similar growth rates of 0.50 (±0.01) per day. In exposures of 20- to 160-mg crushed Moringa seeds L−1, growth rates were negative and on average −0.23 (±0.05) .day−1. Presumably, in the higher doses of 20- to 160-mg crushed seeds per liter, the cyanobacteria died, which was supported by a rapid drop in the Photosystem II efficiency (ΦPSII), while the ΦPSII was high and unaffected in 0, 4, and 8 mg L−1. High-density populations of M. aeruginosa (chlorophyll-a concentrations of ∼270 µg L−1) were reduced to very low levels within 2 weeks of exposure to ≥80-mg crushed seeds per liter. At the highest dosage of 160 mg L−1, the ΦPSII dropped to zero rapidly and remained nil during the course of the experiment (14 days). Hence, under laboratory conditions, a complete wipeout of the bloom could be achieved. This is the first study that yielded evidence for cyanobactericidal activity of filtrate from crushed Moringa seeds, suggesting that Moringa seed extracts might have a potential as an effect-oriented measure lessening cyanobacterial nuisance