Radiocarbon reservoir ages and hardwater effect for the northeastern coastal waters of Argentina

Accelerator mass spectrometry (AMS) radiocarbon dates were obtained for 18 mollusk shells collected alive along the Buenos Aires province coast, Argentina, over the period AD 1914-1935. Reservoir ages were estimated for all samples on the basis of the tree-ring calibration curve for the Southern Hemisphere (SHCal04, McCormac et al. 2004) and the marine ΔR values calculated as the difference between the conventional 14C age and the age deduced from the marine, mixed-layer model calculation (Marine04, Hughen et al. 2004). For most coastal locations, a great ΔR scatter was observed, ranging from 191 to 2482 yr, which is explained by the input of varying content of dissolved carbonate by rivers and groundwater ("hardwater effect") and indicates a serious limitation for shell-based 14C chronologies. Within the interior of Bahía Blanca estuary, ΔR values ranged from -40 to 50 ± 46 as a consequence of the local geological particularities of the environment. This suggests that, with some restrictions, the marine calibration curve with standard parameters (ΔR = 0) could be used at this location.Facultad de Ciencias Naturales y Muse

Quistes de dinoflagelados de sedimentos holocenos y dinoflagelados modernos del estuario de Bahía Blanca, Argentina

En este trabajo se comparan los dinoquistes de sedimentos intermareales holocenos (perfil Canal del Medio) con los resultados de un estudio cualitativo de dinoflagelados en el área de Puerto Cuatreros. Tanto las asociaciones subfósiles como las modernas fueron analizadas en el sector interno del estuario de Bahía Blanca. Todas las especies de dinoquistes holocenas registradas en los sedimentos de las planicies de marea pertenecen a la Familia Gonyaulacaceae: Operculodinium centrocarpum (Deflandre y Cookson) Wall, Operculodinium centrocarpum de procesos cortos, Spiniferitesbulloideus (Deflandre y Cookson) Sarjeant, Spiniferites sp. cf. S. pachydermus (Rossignol) Reid, Spiniferites bentorii (Rossignol) Wall y Dale y Spiniferitesramosus (Ehrenberg) Loeblich y Loeblich. Por otro lado, el estudio de dinoflagelados modernos en la columna de agua mostró una asociación que incluye formas desnudas o atecadas, como Gymnodinium sp. y formas tecadas como Prorocentrum compressum (Bailey) Abé, Dinophysis sp., Protoperidinium conicum (Gran) Balech, Alexandrium tamarense (Lebour) Balech y Qeratiumspp. De estas especies actuales solamente Protoperidinium conicum, Alexandrium tamarense y Gymnodinium sp. producen quistes que pueden preservarse en el registro fósil. La forma móvil Protoceratiumreticulatum (Claparéde y Lachmann) Butschli que produce el dinoquiste Operculodinium centrocarpum no fue registrada hasta ahora en el fitoplancton del sector interno del estuario. Asimismo, las especies de Gonyaulax, tecas parentales de los dinoquistes del género Spiniferites, no fueron mencionadas para el plancton actual. Estas diferencias entre las asociaciones holocenas y las modernas sugieren cambios para el área de estudio, especialmente en la influencia oceánica y en otras condiciones del agua, como el contenido de nutrientes y la turbidez.The aim of this work is to compare the dinocysts of holocene intertidal sediments (Canal del Medio profile) with the results of a qualitative study of dinoflagellates in the Puerto Cuatreros area. The subfossil and modem associations were analyzed in the inner sector of the Bahia Blanca estuary. All the holocene dinocyst species registered in the sediments of the tidal flats belong to Familia Gonyaulacaceae: Operculodinium centrocarpum (Deflandre and Cookson) Wall, Operculodinium centrocarpum of short processes, Spiniferitesbulloideus (Deflandre and Cookson) Sarjeant, Spiniferitescf. S. pachydermus (Rossignol) Reid, Spiniferitesbentorii (Rossignol)Wall and Dale and Spiniferitesramosus (Ehrenberg) Loeblich and Loeblich. Otherwise, the study of modem dinoflagellates in the water column showed an association that includes unarmored or a the cate forms, such as Gymnodinium sp and armored or the cate forms like Prorocentrum compressum (Bailey) Abé, Dinophysis sp., Protoperidinium conicum (Gran) Balech, Alexandrium tamarense (Lebour) Balech and Ceratium spp. From these living species only Protoperidinium conicum, Alexandrium tamarense and Gymnodinium sp. produce cysts that may be preserved in the fossil record. The motile form Protoceratium reticulatum (Claparede and Lachmann) Butschli that produces the dinocyst Operculodinium centrocarpum was not registered hitherto in the phytoplankton studies carried out in the inner part ofthe estuary. Likewise, the species of Gonyaulax, parental thecae of the dinocyst of the genus Spiniferites, were not mentioned for the modem plankton. These differences between holocene and modem associations suggest changes for the study area, especially in the oceanic influence and in other water conditions such as nutrient contents and cloudiness.Material digitalizado en SEDICI gracias a la colaboración de la Facultad de Ciencias Astronómicas y Geofísicas (UNLP).Asociación Argentina de Geofísicos y Geodesta

Radiocarbon reservoir ages and hardwater effect for the northeastern coastal waters of Argentina

Accelerator mass spectrometry (AMS) radiocarbon dates were obtained for 18 mollusk shells collected alive along the Buenos Aires province coast, Argentina, over the period AD 1914-1935. Reservoir ages were estimated for all samples on the basis of the tree-ring calibration curve for the Southern Hemisphere (SHCal04, McCormac et al. 2004) and the marine ΔR values calculated as the difference between the conventional 14C age and the age deduced from the marine, mixed-layer model calculation (Marine04, Hughen et al. 2004). For most coastal locations, a great ΔR scatter was observed, ranging from 191 to 2482 yr, which is explained by the input of varying content of dissolved carbonate by rivers and groundwater ("hardwater effect") and indicates a serious limitation for shell-based 14C chronologies. Within the interior of Bahía Blanca estuary, ΔR values ranged from -40 to 50 ± 46 as a consequence of the local geological particularities of the environment. This suggests that, with some restrictions, the marine calibration curve with standard parameters (ΔR = 0) could be used at this location.Facultad de Ciencias Naturales y Muse

Comparison of phycotoxin composition and distribution in toxigenic plankton from the north and south Atlantic

Two oceanographic surveys for toxigenic phytoplankton in the South and North Atlantic Ocean, including the adjacent Irminger Sea and the Arctic coasts of Greenland and Iceland, were conducted for analysis of putative toxic microalgal species and their respective toxins. During both expeditions, plankton was sampled by phytoplankton net (20 μm mesh) vertical hauls with subsequent size-fractionation, and by filtration of Niskin bottle water samples from discrete depths. In addition, sediment samples at selected stations were taken for identification and analysis of organic-walled dinoflagellate cysts (dinocysts). Among the toxins detected in both areas were domoic acid (DA), pectenotoxins (PTXs), yessotoxin (YTX), and paralytic shellfish toxins (PSTs). In addition, in the northern hemisphere, dinophysistoxins (DTXs) and spirolides were present, but these toxins were not found in Argentinean waters. In the sediments of San Jorge Gulf of Argentina, cysts of the dinoflagellate species Alexandrium tamarense and Protoceratium reticulatum were found, and their respective toxins (PSTs and YTX) were associated with the planktonic samples from the same stations

Comparison of phycotoxin composition and distribution in toxigenic plankton from the north and south Atlantic

Two oceanographic surveys for toxigenic phytoplankton in the South and North Atlantic Ocean, including the adjacent Irminger Sea and the Arctic coasts of Greenland and Iceland, were conducted for analysis of putative toxic microalgal species and their respective toxins. During both expeditions, plankton was sampled by phytoplankton net (20 μm mesh) vertical hauls with subsequent size-fractionation, and by filtration of Niskin bottle water samples from discrete depths. In addition, sediment samples at selected stations were taken for identification and analysis of organic-walled dinoflagellate cysts (dinocysts). Among the toxins detected in both areas were domoic acid (DA), pectenotoxins (PTXs), yessotoxin (YTX), and paralytic shellfish toxins (PSTs). In addition, in the northern hemisphere, dinophysistoxins (DTXs) and spirolides were present, but these toxins were not found in Argentinean waters. In the sediments of San Jorge Gulf of Argentina, cysts of the dinoflagellate species Alexandrium tamarense and Protoceratium reticulatum were found, and their respective toxins (PSTs and YTX) were associated with the planktonic samples from the same stations

Protoceratium reticulatum (Dinophyceae) in the austral Southwestern Atlantic and the first report on YTX-production in shelf waters of Argentina

Protoceratium reticulatum is a dinoflagellate with a life cycle that includes a motile planktonic stage and a resting cyst stage in benthic habitat, both with a wide geographical distribution, including southern South America. P. reticulatum produces yessotoxins (YTX) – these can be accumulated in shellfish and show potent cytotoxicity, posing a risk to human health if contaminated shellfish is consumed. YTX have been reported from coastal shellfish of many localities, but until now it was unknown if they were present in the austral Southwestern Atlantic and also if local populations of P. reticulatum have the ability to produce these toxins. In this study we report the presence of YTX in plankton samples and its production in culture by two P. reticulatum strains isolated from the San Jorge Gulf (SJG). In addition, we describe the geographical distribution and seasonal abundance of this species based on data collected over the past two decades. The YTX cell quotas calculated from net hauls (∼10 pg cell−1) are in the same range as the toxin cell quotas observed in these two isolates. The phylogenetic analysis of sequences of the hypervariable region of the large subunit (LSU) 28S rDNA showed that the two clonal strains from the SJG were part of a monophyletic clade that subdivides P. reticulatum into two well-supported, divergent sub-clades. The sequences of the two strains of P. reticulatum from the SJG fell in the same clade as the majority of sequences of P. reticulatum, which belong to a geographically widely distributed evolutionary clade. P. reticulatum was occasionally observed from about 35° S in Uruguayan shelf waters up to 53° S on the Patagonian shelf and north of Tierra del Fuego, and it was present from coastal areas up to the shelf break zone. We recorded P. reticulatum in plankton samples during spring, summer and autumn but invariably in low abundance (maximum: 560 cells L−1). Viable cysts of the species in surface sediments also showed a wide geographical distribution. Together, the high total abundances and high relative numerical contribution to planktonic dinoflagellate assemblages near frontal areas, emphasize the necessity to pay attention to the dynamics of this species in areas of potential risk of harmful algal bloom development

Azadinium poporum from the Argentine Continental Shelf, Southwestern Atlantic, produces azaspiracid-2 and azaspiracid-2 phosphate

The marine dinophycean genus Azadinium has been identified as the primary source of azaspiracids (AZA), a group of lipophilic phycotoxins known to accumulate in shellfish. Blooms of Azadinium in the southern Atlantic off Argentina have been described from the 1990s, but due to a lack of cultures, the diversity of South-Atlantic Azadinium has not yet been fully explored and their toxin production potential is completely unknown. During a spring 2010 research cruise covering the El Rinco´n (ER) estuarine system (North Patagonian coast, Argentina, Southwestern Atlantic) a search was conducted for the presence of Azadinium. Although neither Azadinium cells nor AZA in field plankton samples were detected, 10 clonal strains of Azadinium poporum were successfuly established by incubation of sediment samples. Argentinean A. poporum were more variable in size and shape than the type description but conformed to it by the presence of multiple pyrenoids with starch sheath, in plate pattern and arrangement, and in the position of the ventral pore located on the left side of the pore plate. In contrast to all previous description of A. poporum, isolates of the Argentinean A. poporum possessed a distinct field of pores on the second antapical plate. Conspecificity of the Argentinean isolates with A. poporum was confirmed by molecular phylogeny of concatenated ITS and LSU rDNA sequences, where all Argentinean isolates together with some Chinese A. poporum strains formed a well-supported ribotype clade within A. poporum. All isolates produced AZA with the same profile, consisting of AZA-2 as the major compound and, to a lesser extent, its phosphated form. This is the first report of a phosphated marine algal toxin. This first confirmation of the presence of AZA producing Azadinium in the Argentinean coastal area underlines the risk of AZA shellfish contamination episodes in the Southwestern Atlantic region