Upwelling events, coastal offshore exchange, links to biogeochemical processes - Highlights from the Baltic Sea Sciences Congress at Rostock University, Germany, 19-22 March 2007

The Baltic Sea Science Congress was held at Rostock University, Germany, from 19 to 22 March 2007. In the session entitled"Upwelling events, coastal offshore exchange, links to biogeochemical processes" 20 presentations were given,including 7 talks and 13 posters related to the theme of the session.This paper summarises new findings of the upwelling-related studies reported in the session. It deals with investigationsbased on the use of in situ and remote sensing measurements as well as numerical modelling tools. The biogeochemicalimplications of upwelling are also discussed.Our knowledge of the fine structure and dynamic considerations of upwelling has increased in recent decades with the advent ofhigh-resolution modern measurement techniques and modelling studies. The forcing and the overall structure, duration and intensity ofupwelling events are understood quite well. However, the quantification of related transports and the contribution to the overall mixingof upwelling requires further research. Furthermore, our knowledge of the links between upwelling and biogeochemical processes is stillincomplete. Numerical modelling has advanced to the extent that horizontal resolutions of c. 0.5 nautical miles can now be applied,which allows the complete spectrum of meso-scale features to be described. Even the development of filaments can be describedrealistically in comparison with high-resolution satellite data.But the effect of upwelling at a basin scale and possible changes under changing climatic conditions remain open questions

Copernicus Marine Service ocean state report, issue 4

This is the final version. Available from Taylor & Francis via the DOI in this record. FCT/MCTE

Copernicus Marine Service Ocean State Report, Issue 5

Demersal species play a fundamental role in fisheries, thus understanding their distribution and abundance through bottom trawl surveys is crucial for stock and fisheries management. Oceanographic (e.g. biogeochemical, physical) and fishing covariates might be considered, in addition to spatio-temporal variables (latitute, longitude, depth, year and month), to better explain trawl survey data. Here, we analyse biomass indices (kg/km2) for European hake, common sole, mantis shrimp, red mullet and common cuttlefish from scientific trawl surveys carried out in the Adriatic Sea and the Western Ionian Sea. We used three different Generalised Additive Model (GAM) approaches (Gaussian, Tweedie and Delta) to fit and predict species biomass distribution. In order to evaluate trade-offs in using different covariates, we compared the results obtained from GAM approaches based only on spatiotemporal variables and GAMs including also oceanographic and fishing effort covariates. The Delta-GAM approach performed better for European hake, mantis shrimp and common cuttlefish, while GAMs based on Gaussian and Tweedie were performing better for the red mullet and common sole, respectively. The results highlighted that adding specific oceanographic and effort covariates to spatiotemporal variables improved the performances of spatial distribution models especially for European hake, mantis shrimp and red mullet. Significant additional explanatory variables were bottom temperature, bottom dissolved oxygen, salinity, particulate organic carbon, and fishing effort for European hake; the same variables and pH for mantis shrimp; chlorophyll-a, pH, sea surface temperature, bottom dissolved oxygen, nitrate and effort for the red mullet; phosphate and salinity for common sole; bottom temperature, bottom dissolved oxygen, and phosphate for the common cuttlefish. The findings highlight that more accurate estimates of spatial distribution of demersal species biomass from trawl survey data can generally be obtained by integrating oceanographic variables and effort in GAMs approaches with potential impacts on stock assessment and essential fish habitats identification