Ole Jacob Broch

Modelling seasonal growth and composition of the kelp Saccharina latissima

A dynamical model for simulating growth of the brown macroalga Saccharina latissima is described. In addition to wet and dry weights, the model simulates carbon and nitrogen reserves, with variable C/N ratio. In effect, the model can be used to emulate seasonal changes in growth and composition of the alga. Simulation results based on published, environmental field data are presented and compared with corresponding data on growth and composition. The model resolves seasonal growth, carbon and nitrogen content well, and may contribute to the understanding of how seasonal growth in S. latissima depends simultaneously on a combination of several environmental factors: light, nutrients, temperature and water motion. The model is applied to aquaculture problems such as estimating the nutrient scavenging potential of S. latissima and estimating the potential of this kelp species as a raw material for bioenergy production.

The role of environmental biotechnology in exploring, exploiting, monitoring, preserving, protecting and decontaminating the marine environment

In light of the Marine Strategy Framework Directive (MSFD) and the EU Thematic Strategy on the Sustainable Use of Natural Resources, environmental biotechnology could make significant contributions in the exploitation of marine resources and addressing key marine environmental problems. In this paper 14 propositions are presented focusing on (i) the contamination of the marine environment, and more particularly how to optimize the use of biotechnology-related tools and strategies for predicting and monitoring contamination and developing mitigation measures; (ii) the exploitation of the marine biological and genetic resources to progress with the sustainable, eco-compatible use of the maritime space (issues are very diversified and include, for example, waste treatment and recycling, anti-biofouling agents; bio-plastics); (iii) environmental/marine biotechnology as a driver for a sustainable economic growth.

Assessing impacts of simulated oil spills on the Northeast Arctic cod fishery

We simulate oil spills of 1500 and 4500m3/day lasting 14, 45, and 90days in the spawning grounds of the commercial fish species, Northeast Arctic cod. Modeling the life history of individual fish eggs and larvae, we predict deviations from the historical pattern of recruitment to the adult population due to toxic oil exposures. Reductions in survival for pelagic stages of cod were 0-10%, up to a maximum of 43%. These reductions resulted in a decrease in adult cod biomass of <3% for most scenarios, up to a maximum of 12%. In all simulations, the adult population remained at full reproductive potential with a sufficient number of juveniles surviving to replenish the population. The diverse age distribution helps protect the adult cod population from reductions in a single years recruitment after a major oil spill. These results provide insights to assist in managing oil spill impacts on fisheries.

Spatiotemporal Dispersal and Deposition of Fish Farm Wastes: A Model Study from Central Norway

Abstract A spatially explicit coupled hydrodynamic-mass transport model system was used to simulate dispersal of particulate organic matter from Atlantic salmon (Salmo salar) farming in central Norway. Model setups of 32 m horizontal resolution were run for periods of up to 650 days for 3 sites of different oceanographic characteristics: one fjord location, one medium-exposed location influenced by fjord water and one coastal location. Records on feed used for each cage at each location were converted to feces released based on a published mass balance model. The results from the simulations were compared with scores from corresponding mandatory benthic surveys (MOM-B) of the sediment layer beneath the farms. The correspondence between simulated and measured thickness of the sediment layer was good, and improved with the inclusion of resuspension processes. At all sites the distribution of organic matter in the bottom layer was non-homogeneous, with significant temporal variation and transport and settling of matter up to at least 0.5 km away from one of the farms. Our results indicate that the monitoring practice used in Norway until now, with a few sediment grab samples taken mainly within the fish farm, may not adequately determine the areal impacts of all salmon farming operations. The patchy distribution of organic matter and the correspondence between simulation and survey results is attributed to the use of full 3D current fields of a high spatiotemporal resolution and a good model for resuspension processes that some previous model studies have failed to properly account for.

A note on the harmonic measure doubling condition

We present a detailed and self-contained proof of the harmonic measure doubling characterization of bounded quasidisks due to Jerison and Kenig.