Dense Bathymetry in Turbid Coastal Zones Using Airborne Hyperspectral Images

We used airborne hyperspectral images to generate a dense survey of bathymetric data in the Bahía Blanca estuary (Buenos Aires Province, Argentina). This estuarine area is characterized by intense sediment transport turning the water muddy, and thus optical bathymetric estimations are difficult. We used 24 spectral bands in a range of 500–900 nm acquired with a hyperspectral camera aboard an unmanned aerial vehicle, together with 100 bathymetry data points surveyed with a sonar sensor aboard an unmanned surface vehicle, covering an area of about 800 m2. Random-forest and support-vector-machine regressors were trained with this data set. The resulting model yielded a determination coefficient of 0.815 with unseen data, a root-mean-square error of 0.166 m, and an absolute average error less than 2%. These results allow dense and accurate reconstructions of the underwater profile in wide, muddy, shallow regions of the Bahía Blanca estuary, showing the feasibility of hyperspectral imagery combined with sonar data in turbid shallow waters.

Description of a new species of Nannopus Brady, 1880 (Copepoda: Harpacticoida: Nannopodidae) from Argentinean waters, including an updated key to species

Both sexes of a new brackish-water species, Nannopus sinusalbi sp. nov. (Nannopodidae) are described from the Bahía Blanca estuary (38°53’S, 62°07’W) in Buenos Aires Province, Argentina. The only previous record of the genus in the study area was identified as the type species, Nannopus palustris Brady, 1880, with no description or illustrations, hence its authenticity cannot be confirmed. Nannopus brasiliensis Jakobi, 1956 is relegated to species inquirenda in the genus rather than being considered a junior synonym of the type species. Nomenclatural issues related to the usage of the alternative spellings Iliophilus Lilljeborg, 1902 and Ilyophilus sensu Sars (1909) and the unavailability of Ilyophilus canui Kim, Choi & Yoon, 2017 are discussed. An updated key to the 18 identifiable species of Nannopus (excluding the type species N. palustris) is presented. The harpacticoid assemblage at the type locality showed a distinct seasonality with N. sinusalbi sp. nov. representing about 8% of the community. The new species showed densities below 5 ind.cm‑2 during most of the year, reaching an abrupt peak of 40.17 ind.cm‑2 towards the end of the summer, when the maximum proportion of ovigerous females was recorded.

Distribution of butyltin compounds in the coastal environment of the Bahía Blanca estuary, Argentina

This study evaluates for the first time the distribution and accumulation of butyltin compounds (BTs) in different compartments as seawater, sediments, suspended particulate matter (SPM) and mussels (Brachidontes rodriguezii) in the Bahía Blanca estuary. The samples were collected from six sampling sites with different anthropogenic impact. A better visualization and interpretation of data were achieved using chemometric tools (Tucker4 model), which made it possible to reveal the main relationships between the variables. This analysis showed the presence of BTs in all environmental compartments along the estuary, even in sites with low human intervention. The relationships found between BTs levels, seasons and environmental matrices show the importance of biological processes such as phytoplankton blooms and remobilization of sediments (by tidal dynamics and/or periodic dredging) in the BTs distribution and degradation. In addition, partition coefficients showed that mussels mainly bioaccumulate tributyltin through sediment, water and, to a lesser extent, from SPM.

STOMACHICOLA LYCENGRAULIDIS N. SP. (DIGENEA, HEMIURIDAE), PARASITE OF THE ATLANTIC SABRETOOTH ANCHOVY LYCENGRAULIS GROSSIDENS (CLUPEIFORMES, ENGRAULIDAE)

This paper describes and illustrates a new species of digenetic trematode, parasitic in the stomach of the sabretooth anchovy Lycengraulis grossidens (Agassiz, 1829) from the Bahía Blanca estuary and the Paraná River, Argentina, designated as Stomachicola lycengraulidis n.sp. The new taxon differs from S. bayagbonai and S. singhi congeneric species from the Gulf of Guinea and Indian Ocean respectively, mainly in the body size, the structure of the reproductive system, the development of the ecsoma and the sinus sac. It differs from the first one mainly in the presence of two frontal protuberances at the level of the preoral lobe, which are absent in the specimens studied here. Also in general terms, S. bayagbonai is comprised of slightly larger individuals, with larger pharynx, testicles and ovary. And it differs from S. singhi by their smaller duct and hermaphroditic sac and for having a well developed seminal receptacle, which is absent in the Bay of Bengal specimens. When comparing the relative size of the ecsoma, we found significant differences among both of the populations of digeneans examined, the worms collected in the Paraná River was more developed than those from the Bahia Blanca estuary. The host, L. grossidens, migrates to the Paraná river in winter and spring and then, from December to March it makes a trophic migration towards the sea and is found all along the Atlantic coast of Buenos Aires province. For this reason, it is here hypothesized that the relative development of the tail, is affected by environmental conditions, such as pH and osmolarity of the stomach, salinity and/or water temperature.