Distribution of biological, anthropogenic, and volcanic constituents in the San Francisco Bay Coastal System

Although conventional sediment parameters (mean grain size, sorting, and skewness) and provenance have typically been used to infer sediment transport pathways, most freshwater, brackish, and marine environments are also characterized by abundant sediment constituents of biological, and possibly anthropogenic and volcanic, origin that can provide additional insight into local sedimentary processes. The biota will be spatially distributed according to its response to environmental parameters such as water temperature, salinity, dissolved oxygen, organic carbon content, grain size, and intensity of currents and tidal flow, whereas the presence of anthropogenic and volcanic constituents will reflect proximity to source areas and whether they are fluvially- or aerially-transported. Because each of these constituents have a unique environmental signature, they are a more precise proxy for that source area than the conventional sedimentary process indicators. This San Francisco Bay Coastal System study demonstrates that by applying a multi-proxy approach, the primary sites of sediment transport can be identified. Many of these sites are far from where the constituents originated, showing that sediment transport is widespread in the region. Although not often used, identifying and interpreting the distribution of naturally-occurring and allochthonous biologic, anthropogenic, and volcanic sediment constituents is a powerful tool to aid in the investigation of sediment transport pathways in other coastal systems.

Age and growth parameters of skates of the genus Bathyraja obtained between 2003-2005 along the Argentine continental shelf

In the last 20 years directed shark and ray fishery has increased alarmingly everywhere in the world. For most species though, no data on growth rate, mortality, fecundity and other life history aspects exist as of now and management of the fishery is therefore insufficient. Also there still exist methodological difficulties in the age determination of elasmobranchs fishes, a fact which complicates the investigation of growth parameters. This study tried to identify the best ageing methods and estimate growth parameters for ten skate species of the genus Bathyraja, all occurring in the southwest Atlantic in depths of 50m and more. 720 samples were collected on board of argentine research vessels in between 2003 and 2005. Crystal violet and a new staining method using potassium permanganate, both applied on sagittal sections of vertebral centra, proved to be most effective in enhancing the banding pattern in most of the species. Thorns were also tested and readings were consistent with the ones made on vertebral sections. Growth parameters could be derived for six species and for the other four estimates could be made. Growth rate as well as infinite length varied between species, with those attaining bigger sizes having lower growth rates. No latitudinal differences in growth rate could be detected but a comparison with samples from other studies showed that total lengths were always reported to be higher around the Malvinas Islands.