Morphological types and seasonal variation in eggs of zooplankton species from bottom sediments in Bahia Blanca Estuary, Argentina

Resting egg production is a survival mechanism in zooplankton species against adverse environmental conditions. Egg accumulation in the upper layer of the bottom sediments is fundamental to the resurgence of the populations of these species when conditions become more favourable. Rotifers, such as Synchaeta sp. and planktonic copepods such as Acartia tonsa and Eurytemora americana are commonly found in Bahía Blanca Estuary and they produce resting eggs. We studied eggs isolated from samples of bottom sediments obtained from two sites located within the inner part of Bahía Blanca Estuary (Cuatreros Port and Ing. White Port). The aims of our work were to describe the morphological types of eggs found in bottom sediments; to try to identify to which species they belong; to corroborate the identity of some of them by means of incubations; and to determine either the spatial or seasonal presence of morphological types according to the sampling site. Sediment samples were collected from Cuatreros Port on a monthly basis from January to December 2003 and samples from Ing. White Port were collected from the area close to the industrial zone only in April 2004. All samples were treated following the sugar flotation method of Onbé. The eggs were observed under stereomicroscope and light microscope. Besides, incubation experiments with eggs were sometimes carried out. Five morphological types of eggs (type A, B, C, D and E) were found in the sediments from Cuatreros Port whereas three types of eggs were found at Ing. White Port (F, G and H). Of the 8 morphological types of eggs found in this study, only those of the rotifer Synchaeta sp. in Cuatreros Port and the copepod A. tonsa in the two sampling sites were confirmed to be respectively diapausal and “delayed -hatching”. As regards the seasonal variation of the eggs found in the sediments from Cuatreros Port and the active forms of the populations of Synchaeta sp. and A. tonsa, our study confirms the presence of eggs in the sediment either in periods of time during which no active forms have been previously reported in the plankton or in periods of time during which only some active forms have been reported at very low densities. Concerning the spatial variation at Ing.White Port, the differences in the presence of eggs across the sampling areas may be due to sediment modifications produced by anthropic impact, where industrial effluents are discharged.Fil: Diodato, Soledad Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Berasategui, Anabela Anhi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Tecnológica Nacional; Argentin

Water quality index including periphyton chlorophyll-a in forested urban watersheds from Tierra del Fuego (Argentina)

The city of Ushuaia, Argentina, has experienced a rapid and unorganized population growth with possible consequences on the dynamics and functioning of urban lotic ecosystems. Urban expansion was not largely accompanied by the development of infrastructure for the provision of services such as drinking water and sewers to all the population. Currently, only 65% of the population is connected to the main sewage system (pre-treatment) and the city does not have a secondary wastewater treatment plant yet. We evaluated the impact of wastewater discharges and non-point contamination on the water quality of the three main water courses that cross the city of Ushuaia: Pipo river (PR), Buena Esperanza stream (BES) and Arroyo Grande river (AGR). We sampled four sites per watershed from spring to autumn in two consecutive years (2018 and 2019): S1 (not urbanized at the upper section), S2 (transitional section), S3 (urbanized at the middle-low section), and S4 (urbanized, close to the outlet). We developed the Fuegian Water Quality Index (F_WQI) as a tool for environmental monitoring in forest streams which includes several indicators of organic inputs (dissolved oxygen, nitrogen-ammonium, total phosphorus, fecal coliform bacteria) and periphyton chlorophyll-a (Peri Chl-a). The variables were ranked and weighed, and the index was constructed using a mathematical formula. Urbanization negatively impacted the water quality of these ecosystems; the F_WQI showed “very bad” and “bad” water quality categories at S4 in BES and AGR, both sites impacted by wastewater discharges and large percentage of urbanized area. Likewise, in the PR watershed, with less urbanization and sewage discharges, the F_WQI indicated “very good” water quality. The F_WQI summarizes the water quality of forested watersheds in a simple numerical scale, resulting in a useful tool for monitoring studies in temperate rivers and streams. We encourage the inclusion of Peri Chl-a in water quality indices, due to its ubiquity in these ecosystems and the fact that it increased the sensitivity of the index.Fil: Granitto, María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Diodato, Soledad Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego; ArgentinaFil: Rodriguez, Patricia Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego; Argentin

Ammonia toxicity in Southern King Crab (Lithodes santolla, Molina 1742) larvae

Effects of ammonia on zoea I of the Southern King Crab, Lithodes santolla (Decapoda, Lithodidae) were analyzed through acute (96 h) and chronic (29 days in total) assays (seven total ammonia nitrogen (TAN) concentrations: 9, 15, 25, 41, 67, 110, and 182 mg L−1, plus control). The estimated LC50-96 h was 107.97 mg TAN L−1 (1.93 mg NH3-N L−1), while the safe level of ammonia was 10.79 mg TAN L−1 (0.19 mg NH3-N L−1). Survival was highest in the three lowest ammonia concentrations throughout 96 h (93.3%, 90% and 93.3% in 9, 15 and 25 mg TAN L−1, respectively). In chronic assays, the percentage of survival decreased along with the exposure time and the ammonia concentration. Zoeae´s mean life time tended to increase almost gradually with the increment of ammonia concentration. Mean molting time from zoea I to II was 4.06 days, while it increased from zoea II to III, and zoea III to the post-larval stage (6.00 and 8.39 more days, respectively) with ammonia concentration. The percentage of individuals that have molted in every molt stage tended to decrease while ammonia concentration increased. Therefore, the results obtained in the present study bring new information about ammonia toxicity in early stages of development of crab Lithodes santolla, an important commercial species of the Beagle Channel.Fil: Diodato, Soledad Lorena. Universidad Nacional de Tierra del Fuego; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Amin, Oscar Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Comoglio, Laura Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

The use of chronic bioassays in Daphnia magna for the environmental evaluation of an urban stream in Tierra del Fuego (Argentina)

El desarrollo de la urbanización impacta negativamente sobre los ambientes acuáticos, ya que los convierte en receptores finales de una variedad de sustancias antrópicas, muchas de ellas causantes de eutrofización. En Ushuaia (Tierra del Fuego), el Arroyo Buena Esperanza (ABE) ha sido sometido a estos impactos, habiéndose detectado que la calidad del agua disminuye a medida que el arroyo atraviesa el ejido urbano y desemboca en la Bahía Encerrada (BE). Sin embargo, se desconoce si presenta toxicidad sobre la biota. Evaluamos la calidad del agua del ABE a lo largo de su recorrido por el ejido urbano y en su desembocadura en la BE mediante el efecto sobre la supervivencia (48 horas) y el crecimiento (21 días) de Daphnia magna. Realizamos bioensayos agudos y crónicos con neonatos de D. magna expuestos a aguas de cuatro sitios del ABE: uno sin impacto urbano, uno con impacto intermedio y dos con impacto alto. La calidad del agua disminuyó a medida que el arroyo atraviesa el ejido urbano, con valores elevados de amonio, fosfatos, materia orgánica particulada, sólidos totales en suspensión y bacterias coliformes (por el aporte de efluentes cloacales sin tratar). La supervivencia de D. magna a las 48 horas fue cercana al 100%, lo cual indica la ausencia de toxicidad aguda del agua. La biomasa individual varió según el sitio y el tiempo ensayado; aumentó gradualmente, pero no de forma pareja entre los sitios. Los organismos expuestos a los sitios más impactados presentaron mayor biomasa y tasa de crecimiento en comparación con los sitios con menor impacto. Esto se vincula a la peor calidad del agua de los sitios impactados. El crecimiento de D. magna resultó ser una herramienta de diagnóstico ambiental aplicable para detectar efectos subletales de las aguas de arroyos fueguinos, y un complemento adecuado del monitoreo ambiental.The development of urbanization has a negative impact on aquatic environments, making them the final receptors for a variety of anthropic substances, many of which lead to eutrophication. In Ushuaia (Tierra del Fuego), the Arroyo Buena Esperanza (ABE) has been subjected to these impacts. Its water quality decreases as the stream crosses the urban zone and discharges into Bahía Encerrada (BE). However, it is unknown whether its waters are toxic to the biota. We evaluated the water quality of the ABE all along its path through the urban zone and at its mouth in the BE through the effect on survival (48 hours) and growth (21 days) of Daphnia magna. Acute and chronic bioassays were conducted with D. magna neonates exposed to waters from four sites of the ABE: one with no urban impact, one with intermediate impact, and two with high impact. Water quality decreased as the stream crosses the urban zone, finding high values of ammonia, phosphates, particulate organic maer, total suspended solids and coliform bacteria; caused by the contribution of untreated sewage effluents. The survival of D. magna at 48 hours was close to 100%, which indicates the absence of acute toxicity of the water. The individual biomass varied according to the site and the time tested, increasing gradually but not evenly between sites. The organisms exposed to the most impacted sites presented higher biomass and growth rate in comparison to the sites with the least impact. This is linked to the poorer water quality of the impacted sites. The growth of D. magna was an environmental diagnostic tool with high applicability for the detection of sublethal effects of the waters of Fuegian streams, which adequately complements the environmental monitoring.Fil: Albizzi, Carla Antonela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Diodato, Soledad Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego; ArgentinaFil: Gonzalez Garraza, Gabriela Carolina. Universidad Nacional de Tierra del Fuego; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Vegetation recovery one year after a wildfire in Tierra del Fuego.

En enero de 2012 un incendio forestal se desató en cercanías de la laguna Las Yeguas, a 15 km de Bahía Torito (54°36’S 68°16’W). Este disturbio, dadas las condiciones topográficas del lugar y las condiciones climáticas del momento, fue de gran magnitud y afectó a 1349 ha de bosques, turberas. El objetivo de este trabajo fue evaluar la recuperación de la vegetación. En abril de 2012 y 2013 se realizó un muestreo de la vegetación del sotobosque en zonas total y parcialmente quemadas y en zonas no afectadas (control). El número de especies encontradas en los controles varió entre 9-19, en las zonas quemadas no se encontró vegetación inmediatamente después del incendio. A un año de producido el incendio, el número de especies se incrementó a 7-18 en las zonas quemadas. El índice de diversidad de Simpson mostró que para los controles los valores fueron de 0,63-0,83; en las zonas totalmente quemadas por el incendio resultó de 0,05-0,08 y entre 0,68-0,80 para zonas parcialmente quemadas. El 78% de las especies muestreadas en la zona afectada se encontraron presentes en los controles. Hasta el momento, la recuperación de la vegetación está siguiendo los patrones normales de sucesión ecológica luego de producido un incendio, con presencia casi exclusivamente de especies nativas.Fil: Selzer, Luciano Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina;Fil: Oro Castro, Natalia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina;Fil: Mansilla, Paula Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina;Fil: Diodato, Soledad Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina;Fil: Escobar, Julio Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina;Fil: Moretto, Alicia Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina

Contribution of planktonic and detritic fractions to the natural diet of mesozooplankton in Bahía Blanca estuary

The relative importance of phytoplankton and microzooplankton in the natural diet of mesozooplankton was assessed in Bahía Blanca Estuary, Argentina, in December 2005. Grazing experiments were performed using 200-to-2,000 µm grazers and natural food <100 µm. Individual and community filtration and ingestion rates were estimated for each food fraction after 24 h incubation. Abundance and carbon data of prey and grazers were qualitatively and quantitatively analyzed. Phytoplankton was mainly composed of diatoms and microzooplankton mainly of tintinnids. Both fractions were less abundant than detritus. Most of the grazers belonged to the copepod Acartia tonsa. Mean filtration and ingestion rates on phytoplankton + microzooplankton were 6.44 ml grazer-1 day-1 and 0.03 µg C grazer-1 day-1, respectively. This figure increased to 6.95 ml grazer-1 day-1 and 1.65 µg C grazer-1 day-1 when detritus was included. Mean carbon-specific ingestion rates on phytoplankton and microzooplankton were 0.006 and 0.005 µg C µg C-1 day-1, respectively, whereas after the addition of detritus, the overall rate increased to 0.588 µg C µg C-1 day-1. Highly significant differences were found between grazing rates on detritus and planktonic fractions. Consumers showed higher filtration rates on microzooplankton than on phytoplankton although 78% of the cells ingested (54.7% µg C) came from the latter. The results point to a higher contribution of detritus to the natural diet of mesozooplankton in late spring. The omnivory of A. tonsa and the high turbidity of Bahía Blanca estuary may explain the differences observed among food fractions in terms of carbon intake.Fil: Diodato, Soledad Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Tecnológica Nacional; Argentin

Responses of the resident rocky crab (Halicarcinus planatus, Decapoda) to natural stressors and effluent discharges in Ushuaia Bay, Tierra del Fuego, Argentina

Ushuaia City has been growing since 1980 and industrial and domestic effluents have been discharged along its coasts. The present study evaluates the acute exposure of the rocky crab Halicarcinus planatus to three environmental stressors (salinity, pH and ammonia) and to in situ coastal whole effluents (Industrial Zone (IZ), Yacht Club (YC) and Encerrada Bay (EB)). Neither mortalities nor molting events were recorded during the study period. The highest physiological rates were at salinity 25, at pH 9.5 and at 3mg N-NH 3L -1 (174.38±17.76μg O 2h -1g -1 and 12.80±4.54μg N-NH 3h -1g -1; 199.45±11.86μg O 2h -1g -1 and 27.82±6.88μg N-NH 3h -1g -1; and 232±43.5μg O 2h -1g -1 and 26.29±3.42μg N-NH 3h -1g -1, respectively). Crabs exposed to the studied areas also showed a tendency to increase physiological parameters. Acetylcholynesterase (AChE) activity showed maximal inhibition in organisms from YC (0.14±0.07nmolmin -1mgprotein -1). H. planatus showed responses to both specific and complex environmental stressors and its use as a suitable bioindicator of environmental changes is discussed.Fil: Diodato, Soledad Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Comoglio, Laura Ines. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Camilión, María Carolina. No especifica;Fil: Amin, Oscar Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Integrated biomarker response in Mytilus chilensis exposed to untreated urban discharges along the coast of Ushuaia Bay (Beagle Channel, Argentina)

The short-term effects of coastal untreated effluents from Ushuaia Bay, Beagle Channel, on the biochemical and physiological biomarkers of Mytilus chilensis were assessed. An integrated biomarker response (IBR) index was calculated as a helpful tool to represent the general stress of the experimental organisms. Cultured mussels were exposed during 96 h to three coastal sites impacted by sewage effluents. At the beginning (T0) and every 24 h, mussels were subsampled from each site and different biochemical and physiological biomarkers were determined. There was no mortality registered in the experiments during the 96 h. However, biochemical and physiological biomarkers presented significant variations. Lipid peroxidation mean levels in mussels decreased in mantle and increased in digestive gland with respect to T0 in almost all cases. Acetylcholinesterase activity was inhibited in all sites, reaching a maximal decrease of 35% with respect to T0. Catalase remained stable and glutathione-S-transferase was activated. Oxygen consumption and ammonia excretion rates increased in organisms from two sites and, consequently, O:N ratio decreased, denoting a symptom of stress. IBR values showed the existence of different stress levels between exposed and unexposed mussels. These results exhibited an alteration of the general metabolism of mussels exposed for a short period of time to untreated coastal wastewater, suggesting the use of these organisms as early indicators of changes in the environmental quality of coastal waters of Ushuaia Bay.Fil: Diodato, Soledad Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego, Antártida e Islas del Atlántico Sur. Instituto de Ciencias Polares, Ambientales y Recursos Naturales; ArgentinaFil: Comoglio, Laura Ines. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Camilion, Carolina. Universidad Nacional de Tierra del Fuego, Antártida e Islas del Atlántico Sur. Instituto de Ciencias Polares, Ambientales y Recursos Naturales; ArgentinaFil: Amin, Oscar Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Marcovecchio, Jorge Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca; Argentina. Universidad FASTA "Santo Tomas de Aquino"; Argentin