Surface distribution of size-fractionated chlorophyll a and participate organic matter in the Strait of Magellan

Self Cite

SUMMARY: The elemental and biochemical composition of particulate organic matter (POM) was investigated in the Straits of Magellan during February-March 1991. Twenty-two stations were selected in order to identify different areas of the Magellan ecosystem from a trophic point of view. The Strait of Magellan can be divided into three subsystems characterized by different hydrological and geomorphological conditions. Seston concentrations were mostly constrained by physical events, particularly the influence of oceanic and land run-off water inputs and the strong vertical mixing and resuspension events. POM composition displayed quali-quantitative differences between the three areas. In the first subsystem, influenced by Pacific waters, the low seston and POM concentrations and the high POC/Chl-a ratio values indicated the general predominance of the detrital and heterotrophic fractions. In the second subsystem, characterized by superficial stratification, higher seston and organic matter concentrations and lower values of POC/Chl-a ratio were found, indicating that this subsystem was influenced by an active autotrophic component. Shallow waters with intense tidal regime and strong vertical mixing characterized the third subsystem, connected to the Atlantic Ocean, which displayed an increasing importance of the inorganic fraction (values of the POC/TSM ratio lower than in the other systems). Moreover, the third subsystem showed higher values of the RNA/DNA ratio, possibly indicating that resuspension events may enhance the metabolic state of the organic particles mainly dominated by heterotrophic components.Key words: Particulate organic matter, biochemical composition, Straits of Magellan . RESUMEN: COMPOSICIÓN DE LA MATERIA ORGÁNICA PARTICULADA EN UN SISTEMA PERIANTÁRTICO SEMI-CERRADO: EL ESTRE-CHO DE MAGALLANES. -Se estudió la composición elemental y bioquímica de la POM (materia orgánica particulada) en el Estrecho de Magallanes durante el periodo febrero-marzo de 1991. Se eligieron 22 estaciones a fin de identificar diferentes áreas del ecosistema magallánico desde un punto de vista trófico. De acuerdo con las características hidrológicas y geomorfológicas dicho Estrecho se puede dividir en 3 subsistemas. Las concentraciones de seston estuvieron condicionadas, principalmente, por los fenómenos físicos y, en particular, por los aportes oceánicos y terrestres, por la mezcla vertical y por los fenómenos de resuspensión. La composición de la materia orgánica particulada (POM) mostró diferencias cualitativas y cuantitativas en las tres áreas. En el primer subsistema, influenciado por las aguas del Océano Pacífico, las bajas concentraciones de seston y POM y los altos valores de la relación POC/clorofila a indicaron una predominancia general de las fracciones detrítica y heterótrofa. En el segundo subsistema, caracterizado por una estratificación superficial, se encontraron altas concentraciones de seston y de materia orgánica y bajos valores de la relación POC/clorofila a, señalando una influencia de la componente...

Section: Discussionsupporting

confidence: 79%

Particulate organic matter composition in a semi-enclosed Periantarctic system: the Straits of Magellan

Fabiano¹,

Pedrini²,

Danovaro³

et al. 1999

Self Cite

“…cit.). This significant contribution of picoplankton and also microphytoplankton (2-10 µm) to the total chlorophyll was also emphasized for the Chilean fjord region during late summer Carrada et al, 1994;Carrada et al, 1996) as well as their very low contribution during spring (Panella et al, 1991).…”

Section: Trends and Order In The Plankton Assemblagementioning

confidence: 85%

“…Temperature, salinity and density profiles along the Straits of Magellan (Pickard, 1971;Artegiani and Paschini, 1991;Panella et al, 1991) support these conclusions. From the faunistic point of view, the sill on the Pacific entrance and the shallow Angosturas extending to the Atlantic shelf seem firm barriers for the penetration and distribution of oceanic plankton into the Straits of Magellan (Antezana et al, 1992), as has been demonstrated for copepods (Mazzocchi and Ianora, 1991), phytoplankton (Uribe, 1991;Cabrini and Fonda Umani, 1991;Marino et al, 1991) and chlorophyll (Panella et al, 1991;Saggiomo et al, 1994;Carrada et al, 1994). A degree of variability to these limits was found in microzooplankton indicating that the Atlantic entrance basin extends only to Bahía Inútil and the Pacific entrance basin reaches Cabo Froward (Fonda Umani and Monti, 1991).…”

Section: Linkages In a Spatial Gradientmentioning

confidence: 90%

Plankton of Southern Chilean fjords: trends and linkages

Antezana¹

1999

SUMMARY: The present paper compiles and reviews past and recent results from Magellan and Fuegian fjords for an overview of the planktonic assemblage there. It first examines linkages to local, adjacent and remote environments. The plankton assemblage presents deviations from the biota of the Magellan biogeographic Province, where the occasional presence of Antarctic species is related to oceanographic phenomena at the Polar Front. Complex bathymetric and hydrographic features within the fjords suggest that the plankton is rather isolated. Adaptations and constraints for population survival, and the role of diel migrators and gregarious zooplankters with regard to bentho-pelagic coupling are discussed. Results on seasonal differences in the plankton of the largest and most isolated basin of the Strait of Magellan are compiled. In spring the plankton was dominated by large diatoms suggesting a short food chain where most of the phytoplankton bloom goes to the bottom, to the meroplankton and to a few dominant holoplankters. In summer, the phytoplankton was dominated by picoand nanophytoplankton suggesting a more complex food web mediated by a bacterial loop. High abundance of holo-and meroplanktonic larvae coincided with spring blooming conditions. Key words: Estuarine, Subantarctic, adaptations, patterns, seasonal, migration, food webs. RESUMEN: PLANCTON DE LOS FIORDOS DEL SUR DE CHILE: TENDENCIAS Y CONEXIONES. -Este trabajo compila y revisa los resultados pasados y recientes de los fiordos fueguinos y magallánicos para proporcionar una visión integral de la comunidad planctónica. Primero se examinan las conexiones con los ambientes locales adyacentes y remotos. La comunidad planctónica presenta desviaciones de la biota de la Provincia biogeográfica Magallánica, donde la presencia ocasional de especies antárticas se relaciona con fenómenos oceanográficos en el Frente Polar. Rasgos batimétricos e hidrográficos complejos en los fiordos sugieren que el plancton está más bien aislado. Se discuten las adaptaciones y limitaciones para la supervivencia poblacional y el papel de los migradores diarios y del zooplancton gregario con respecto al acoplamiento bentopelágico. Se resumen los resultados sobre diferencias estacionales en el plancton de la más vasta y aislada cuenca del Estrecho de Magallanes. En primavera, el plancton estuvo dominado por diatomeas grandes, sugiriendo una cadena trófica corta, en la que la mayor parte de la biomasa producida va al fondo, al meroplancton y a unos pocos organismos dominantes del holoplancton. En verano, el fitoplancton estuvo dominado por pico-y nanofitoplancton, sugiriendo una red trófica más compleja mediada por un bucle bacteriano. La gran abundancia de larvas holo-y meroplanctónicas coincidió con las condiciones de proliferación primaveral.

“…In the third area, towards the Pacific Ocean, the particulate matter is characterized by large amounts of heterotrophic detritus (0.36 Chl-a µg l -1 ) of quite low energetic value (C:N = 6.07; Carrada et al, 1994).…”

Section: Pelagic-benthic Coupling In the Straits Of Magellanmentioning

confidence: 99%

The role of pelagic-benthic coupling in structuring littoral benthic communities at Terra Nova Bay (Ross Sea) and in the Straits of Magellan

Cattaneo‐Vietti¹,

Chiantore²,

Misic³

et al. 1999

SUMMARY: In Antarctic and peri-Antarctic regions, benthic communities are persistent in time and show high biomass and large numbers of individuals, mainly consisting of suspension and deposit feeders. In fact, apart from recruitment, the major factor structuring these communities is the high flow of organic matter from the pelagic domain to the bottom, representing an important energy source for the benthic organisms. The aim of this paper is to review, compile and compare the data from earlier investigations in Terra Nova Bay (Ross Sea) and the Straits of Magellan, in order to come to a more general conclusion about the role of the pelagic-benthic coupling in structuring littoral benthic communities in southern coastal areas. Few measurements of flux rates and the biochemical composition of the sinking particles occurring in Antarctic and peri-Antarctic shallow waters are available, but a compilation of our own data and others allows a comparison of these two systems. The different environmental conditions between Antarctica and the Straits of Magellan lead to differences in the origin of the particulate organic matter and in its biochemical composition, and consequently in the coupling between pelagic and benthic domains. At Terra Nova Bay the summer particulate matter shows a high labile fraction of a good food value: its flux has been evaluated at about 0.67 g m -2 d -1 . Conversely, the Straits of Magellan show multi-structured ecosystems where the quality and quantity of the organic matter flux towards the bottom change according to the local geomorphology and current dynamics. Moreover, the three-dimensional assemblages of suspension-feeders, so common in Antarctic shallow waters, seem to be absent in the Magellan area. In particular sponges, gorgonarians and bryozoans play a secondary role inside the Straits of Magellan, where polychaetes (60%) and molluscs (9-10%) are dominant on soft bottoms, and where they reach high values in density and biomass. Bivalves seem to play an important role in both regions: for instance, at Terra Nova Bay, the scallop Adamussium colbecki processes about 14 % of the total carbon flux, with an assimilation efficiency of 36 %. This scallop seems to be able to adapt its reproductive period and its trophic behaviour to the changes in the quality and quantity of the pelagic events. The pulsing trend of the vertical flux, which in a few weeks can reach the total annual input, produces significant changes in the physiology (growth, reproduction, spawning) and trophic behaviour of many benthic species, such as sponges and polychaetes. The study of the pelagic-benthic coupling could be essential in the evaluation of the trophic capacity and the environmental response around sites of sea-farming, which are an ever-growing activity in the Magellan area.