Magnetic proxies of continental shelf sediments and their implication for the benthic zone and shrimp fishing activities

Abstract

The San Jorge Gulf is an ecosystem of great economic importance in the southern hemisphere. It is a breeding and spawning area for various fish and crustacean species. In particular, the Pleoticus muelleri shrimp in different stages of its life cycle and the benthic system are linked. Therefore, in recent decades, it has been of interest for this shrimp resource to carry out interdisciplinary studies focused on the properties of the marine substrate. The concentration of single domain + multidomain magnetite, paramagnetic minerals, and organic matter of seabed sediments vary widely within a study area of about 60400 km2. Values of specific magnetic susceptibility (χ), anhysteretic ratio (χARM/χ), total organic carbon (TOC), and total nitrogen (TN) range between 18.3–323.1 × 10−8m3kg−1, 1.5–13.2, 0.14–1.58%, and 0.02–0.19%, respectively. The spatial correlations between TOC and TN with χ (ρK = −0.72 and −0.59, respectively) and χARM/χ (ρK = 0.90 and 0.71) for these seabed sediments provide good magnetic proxies, which can be determined readily and with low cost. The spatial distribution of geochemical variables and magnetic proxies shows well-delimited areas concerning coastal, inner gulf, eastern, and northeastern zones, which could benefit the management of shrimp resource.