First discovery – and a new species – of Coelogynopora (Platyhelminthes, Proseriata) in the Southern Hemisphere

Coelogynoporidae (Platyhelminthes) includes comparatively large and slender Proseriata, usually occurring in shallow benthic environments. Coelogynopora Steinböck, 1924 is the most frequently reported genus and the one with the highest species diversity. Notwithstanding that, the genus has never been reported from the Southern Hemisphere. A recent analysis of sediment from the Magellan Strait shores (Chile) resulted in the discovery of a new species of Coelogynopora, the first representative of the genus to be found in austral waters. The new species is defined by the following combination of characters: sclerotised copulatory system consisting of a slender, ventrally curved stylet with a broad base and three pairs of symmetrically arranged spines, the proximal ends of which are fused laterally to the base of the stylet; distal ends of the three pairs of spines hooked, with apophyses at progressively longer distances from the tip; accessory spines and solar organ absent. Based on the morphological characters, the new species appears to be more related to species from the Pacific Ocean than to those from the Atlantic Ocean. The present work suggests a vast biogeographic disjunction in the genus Coelogynopora, which may be described as a bipolar or amphitropical pattern of distribution.

Estimates of Fuegian sprat consumption by humpback whales in the Magellan Strait feeding area as predicted by a bioenergetic model

Knowing the biomass of prey consumed by a marine predator is a prerequisite for assessing the potential of the predator for competition with fisheries. Here, we estimated the biomass of Fuegian sprat Sprattus fueguensis consumed annually by a small subpopulation of humpback whales Megaptera novaeangliae in the Magellan Strait feeding area. We used a velocity-dependent bioenergetic model that integrates annual energy requirements by sex, age class, and reproductive status, proportion of Fuegian sprat in the diet, and annual population size of whales. The annual energy required in kcal per individual whale was estimated to be 18.88 × 107 for calves, 27.92 × 107 for adults, 30.71 × 107 for pregnant females, and 42.59 × 107 for lactating females. These estimates result in an energy requirement of 19.32 × 109 and 23.41 × 109 for a seasonal abundance of 78 and 96 whales, respectively. Bayesian dietary mixing models predict that Fuegian sprat represented between 27 and 33% of the diet of the whales. This implies that humpback whales remove between 2965 and 3896 t of Fuegian sprat per year during a feeding period of 120 d. However, if estimates are extended to an abundance of 204 humpback whales during the period 2004-2017, the consumption is elevated to 8167-8383 t yr-1. The estimates provided here are useful to apply as input data for consumption by humpback whales in the Fuegian sprat fishery management as well as for conservation plans of this small and vulnerable feeding subpopulation of humpback whales.

IMPORTANCE OF REMOTE SENSING FOR THE STUDY OF SPATIAL DYNAMICS OF ESTUARINE NEUSTON FROM SOUTHERN CHILE

Zooplankton aggregation, hydrographic and remote sensing data were employed to relate the spatial dynamics of neustonic communities with chlorophyll a (Chl a) and suspended organic matter (SOM) at a spatial mesoscale (10 to 1000 km) in the southern Chilean fjords system along Magellan Strait, Chile (CIMAR 16: October/November 2010 and CIMAR 25; September/October 2019) in order to identify oceanographic process producing aggregation of neuston. Preliminary evidence of CIMAR 25 shows significant concentrations of Chl a and SOM around Dawson Island (DI), Magellan Strait. During CIMAR 16 important aggregation of specific neustonic taxa (copepodites of Microsetella rosea, larvae of the polychaete Polygordius sp and cyphonautes of the bryozoan Membranipora isabelleana) was observed around DI, Magellan Strait. Satelital images in the area of CIMAR 16 provide evidence of important aggregation of chlorophyll a/SOM around DI. CIMAR Cimar 25 showed that the Chl a and SOM aggregation around DI is recurrent and could to explain the high concentration of neuston around this island to spite of mesotrophic conditions. Remote sensing in this study area provides a tool to understanding oceanographic and topographic factors that potentially regulate the abundance and spatial distribution of surface zooplankton to spatial meso-scale along Magellan Strait.

Dynamical connections between large marine ecosystems of austral South America based on numerical simulations

The Humboldt Large Marine Ecosystem (HLME) and Patagonian Large Marine Ecosystem (PLME) are the two largest marine ecosystems in the Southern Hemisphere and are respectively located along the Pacific and Atlantic coasts of southern South America. This work investigates the exchange between these two LMEs and its seasonal and interannual variability by employing numerical model results and offline particle-tracking algorithms. Our analysis suggests a general poleward transport on the southern region of the HLME, a well-defined flux from the Pacific to the Atlantic, and equatorward transport on the PLME. Lagrangian simulations show that the majority of the southern PS waters originate from the upper layer in the southeast South Pacific (<200 m), mainly from the southern Chile and Cape Horn shelves. The exchange takes place through the Le Maire Strait, Magellan Strait, and the shelf break. These inflows amount to a net northeastward transport of 0.88 Sv at 51∘ S in the southern PLME. The transport across the Magellan Strait is small (0.1 Sv), but due to its relatively low salinity it greatly impacts the density and surface circulation of the coastal waters of the southern PLME. The water masses flowing into the Malvinas Embayment eventually reach the PLME through the Malvinas Shelf and occupy the outer part of the shelf. The seasonal and interannual variability of the transport are also addressed. On the southern PLME, the interannual variability of the shelf exchange is partly explained by the large-scale wind variability, which in turn is partly associated with the Southern Annular Mode (SAM) index (r=0.52).

Dynamical Connections between Large Marine Ecosystems of Austral South America based on numerical simulations

The Humboldt Large Marine Ecosystem (HLME) and Patagonian Large Marine Ecosystem (PLME) are the two largest marine ecosystems of the Southern Hemisphere, respectively located along the Pacific and Atlantic coasts of southern America. This work investigates the exchange between these two LMEs and its variability, employing numerical model results and offline particle tracking algorithms. 27 years of a 1/12° ROMS configuration (CMM) show a general poleward transport on the Southern region of HLME, and equatorward on the Patagonian Shelf (PS). A mean transport across Cape Horn's shelf (68.1° W) is 0.95 Sv. Lagrangian simulations show that the majority of the southern PS waters originate from the upper layer in the southeast South Pacific (> 200 m), mainly from the southern Chile and Cape Horn shelves. The exchange takes place through Le Maire Strait, Magellan Strait, and the shelf-break. These inflows account to a net northeastward transport of 0.88 Sv at 51° S in the southern PLME. The transport across Magellan strait is small (0.1 Sv) but due to its relatively low salinity it impacts greatly the density and surface circulation of the coastal waters of the southern PLME. The water masses flowing into the Malvinas Embayment eventually reach the PLME through the Malvinas Shelf and occupy the outer part of the shelf. The seasonal and interannual variability of the transport are also addressed. On the southern PLME, the interannual variability of the shelf exchange is partly explained by the large-scale wind variability, which in turn is partly associated with the SAM index (r = 0.52).