Humberto E. González

Patagonian Fjord Ecosystems in Southern Chile as a Highly Vulnerable Region: Problems and Needs

Southern Chile encompasses one of the most extensive fjord regions of the world, the Patagonia, currently exposed to natural and anthropogenic perturbations. These fjord ecosystems provide important services to humans, which have not been adequately measured and valued. As a consequence, ecosystem services are commonly ignored in public policy design and in the evaluation of development projects. Here we tackle questions that are highly relevant for the nation’s development, namely (1) understanding fjord functioning, and (2) developing management strategies based on ecosystem services, in order to secure simultaneous and adequate use of these ecosystems which area influenced by ecological (e.g., biogeochemical) and productive (e.g., aquaculture, fisheries) processes. We also seek to strengthen the analysis of fjord ecosystem value from the economical (including coastal zoning), socio-cultural, institutional, and governmental points of view. In addition, the investigation of current and future effects of climate change on this large region offers a unique opportunity to understand the social and economic consequences of a global phenomenon at local to regional scales. Biogeochemical and socio-economic models will be used to simulate future scenarios under a gamut of management options.

Occurrence of cyclopoid copepods and faecal material in the Halley Bay region, Antarctica, during January–February 1991

Faecal material and cyclopoid copepods were collected during the expedition ANT IX/3, in the Halley Bay area (Weddell Sea, Antarctica), between January and February 1991. Faecal material comprised pellets produced by krill, copepods, ostracods and appendicularians. Cyclopoid copepods were represented by two genera, Oithona and Oncaea. In the Halley Bay area, higher concentrations of krill faecal material (420.9 mm3 m−2) and chl.-a (39.3 mg m−2) were found within the upper 200 m of the water column of the polynya than in ice-covered open-ocean areas (58.2 mm3m−2 and 25.5 mg m−2, respectively). At an ice-drift station, high concentrations of krill faecal strings under fest-ice were found. In addition, similarities between diatom assemblages in the pack-ice algae and krill faecal strings contents suggest an active utilization of ice-algae by krill populations. Sedimented material collected at 50 m depth by a sediment trap was dominated by krill faecal strings. Contents of small oval pellets (of probable cyclopoid copepod origin) resemble those of krill faecal pellets suggesting that coprophagy was involved. This suggestion is supported by: (1) The small quantity of food particles (other than krill faecal matter) available in the water column (< 0.3 μg chl.-al−1). (2) The negative in situ correlation between krill faecal strings and cyclopoid copepods. (3) The structure of cyclopoid copepod buccal appendages, which are more adapted for raptorial feeding.

Assessing the micro-phytoplankton response to nitrate in Comau Fjord (42°S) in Patagonia (Chile), using a microcosms approach

Anthropogenic (aquaculture) changes in environment nutrient concentrations may affect phytoplankton (biomass and taxa composition) in marine coastal waters off the Chilean Patagonia. The effects of adding nitrate (NO3−) to natural phytoplankton assemblages were evaluated considering biomass, cell abundance, and taxonomic composition. Microcosm experiments were performed in the spring, summer, and winter in the Comau Fjord located in Subantarctic Patagonia. At the end of the experiments, NO3− decreased rapidly and was undetectable in treatments, indicating a strong NO3− deficiency associated with an exponential increase in Chl-a concentrations, particulate organic nitrogen, and carbon in these treatments. Moreover, given the depleted nitrate concentrations of the spring and summer experiments, the micro-phytoplankton taxa structure shifted from mixed diatom and dinoflagellate assemblages (Ceratium spp., Dinophysis spp., Coscinodiscus sp., Rhizosolenia pungens) to assemblages dominated by blooms of the classic chain-forming diatoms found in temperate and cold waters such as Chaetoceros spp., Skeletonema spp., and Thalassiosira spp. Thus, nitrogen sources (i.e., nitrate, ammonia) may influence phytoplankton abundance and biomass accumulation dynamics in the northern section of Patagonia. It also emphasizes the importance of diatom taxa in regards to the short-term response of phytoplankton to changing environmental nutrient conditions due to natural (decreasing freshwater stream flow) and anthropogenic (aquaculture) events. This situation may be one of the future scenarios in the Patagonian fjords, thus stressing the needs for active environmental monitoring and impact assessment.

Effects of the 1997-98 El Niño on the Oceanographic Conditions and Zooplankton Community Structure in the Coastal Upwelling System Off Northern Chile

This study was supported by FONDECYT Grant 1000419, 5960002-1996 and PCCI CONICYT/CSIC 2000-2-083

Structure and functioning of two pelagic communities in the North Chilean Patagonian coastal system

The size composition of primary producers is important for how energy is channeled through a food web and on to the higher trophic levels and eventually to fisheries. To evaluate this, we studied the productive patterns for large (micro) versus small (nano) phytoplankton in two south marine Patagonian ecosystems: The Inner Sea of Chiloe—ISCh and, Moraleda Channel—MCh. We built Ecopath models (EwE), and evaluated the hypothesis that the overall primary productivity—rather than the ratio of large to small primary producers—constitutes an adequate proxy for predicting the amount of secondary and tertiary production and biomass (up to the fisheries). The EwE model included four small-scale fisheries and 36 functional groups. The functioning of both ecosystems was similar but the ecosystem parameters (biomass, energy transfer efficiencies from primary producers, secondary, and tertiary production) were twice as much in the basin with more microphytoplankton biomass. Overall, the hypothesis was rejected, albeit it was possible to highlight the importance of the quality and size spectrum of plankton on the structure of marine ecosystem, and to demonstrate the key role of the microbial loop over traditional food web in the functioning of the carbon biological pump in Patagonia ecosystems.

Size‐spectrum based differential response of phytoplankton to nutrient and iron‐organic matter combinations in microcosm experiments in a Chilean Patagonian Fjord

The Patagonian fjords have been recognized as a major region of relatively high primary productivity systems during spring–summer bloom periods, where iron‐organic matter forms may be essential complexes involved in key growth processes connected to the carbon and nitrogen cycles. We used two dissolved organic matter (DOM) types, marine polysaccharide and siderophore, as a model to understand how they affect the bioavailability of Fe to phytoplankton and bacteria and to assess their ecological role in fjord systems. A 10‐day microcosm study was performed in the Comau Fjord during summer conditions (March 2012). Pico‐, nano‐, and microphytoplankton abundance, total chlorophyll‐a and bacteria abundance, and bacterial secondary production estimates were analyzed in five treatments: (i) control (no additions), (ii) only nutrients (NUT: PO4, NO3, Si), (iii) nutrients + Fe(II), (iv) polysaccharide (natural diatoms extracted: 1–3 beta Glucan), and (v) Hexandentate Desferroxiamine B (DFB, siderophore). Our results showed that while DFB reduced Fe bioavailability for almost all phytoplankton assemblages in the fjord, polysaccharide did not have effects on the iron bioavailability. At Nutrients + Fe and Polysaccharide treatments, chlorophyll‐a concentration abruptly increased from 0.9 to 20 mg m−3 during the first 4–6 days of the experimental period. Remarkably, at the Nutrients + Fe treatment, the development of the bloom was accompanied by markedly high abundances of Synechococcus, picoeukaryotes, and autotrophic nanoflagellates within the first 4 days of the experiment. Our study indicated that small plankton (phytoplankton <20 μm and bacteria) were the first to respond to dissolved Nutrients + Fe compared to large sized micro‐phytoplankton cells (>20 μm). This could be at least partially attributed to biological utilization of Fe (2 to 3 nM) by <20 μm phytoplankton and bacteria through the interaction with organic ligands released by bacteria that eventually could increase solubility of the Fe dissolved fraction thus having a positive effect on the small‐sized phytoplankton community.

Obituary: Francesc Pagès (1962–2007)

Francesc Pages was born in Barcelona on 6th July 1962. He started studies on gelatinous plankton as an undergraduate student of biology at the University of Barcelona, in 1989, and maintained his enthusiasm for these organisms throughout his professional career. Francesc’s first project was a careful study of the Mediterranean gelatinous fauna under the supervision of Josep-Maria Gili, and this would later become the topic of his PhD thesis. It was surprising that a person of his age could have such a clear professional interest. Those were fantastic years, when he learned the taxonomy and ecology of jellyfish and siphonophores. That period was especially hard for Francesc because he had to balance his passion and inclination for gelatinous species with the demands of his undergraduate studies.

Downward fluxes of particulate organic matter in coastal and oceanic areas off Chile: The role of the OMZ and functional groups of the plankton

Flujos verticales de particulas han sido estimados durante la ultima decada en sistemas costeros y oceanicos frente a Chile centro-sur. Trampas cilindricas derivando con la corriente han sido usadas bajo la capa de mezcla de sistemas costeros, mientras que trampas automaticas conicas han sido ancladas en sistemas oceanicos profundos. Los flujos hacia 2300 m de profundidad frente a Coquimbo estuvieron dominados por carbonado de calcio (~70 mg m-2 d-1) mas que carbono organico particulado (POC ~7 mg m-2 d-1), donde foraminiferos (Neogloboquadrina pachyderma) y pellet fecales de Euphausia mucronata y Oikopleura spp, juegan un papel muy importante como vehiculos de carbonato y carbono, respectivamente. En sistemas de surgencia costera (i.e., Concepcion), el flujo vertical dominante fue POC, principalmente gobernado por pellets fecales de eufausidos y diatomeas de los generos Thalassiosira, Chaetoceros y Skeletonema. La degradacion bacteriana de material organico exportado hacia zonas mas profundas del oceano no aparece significativamente afectada por los niveles caracteristicos de concentracion de oxigeno disuelto oxicos versus hipoxicos en las diferentes masas de agua.

Correction to: Influence of summer conditions on surface water properties and phytoplankton productivity in embayments of the South Shetland Islands

This correction serves to provide the correct rendering of Table 3 with its respective symbols corrected to superscript (provided below and not in the original article). Additionally with this correction the author would like to bring to attention the revision of the original article, correcting typographical errors in the Abstract, Tables 1, 2, 3 and Figure 7. For the abstract this entailed the changing of ‘productivityon’ to simply ‘productivity’. For Tables 1, 2 and 3, this entailed the changing of “five” to “four”. And for Fig. 7 this entailed changing the footnote from “at the five of the SSI” to “at the four stations of this study”. The author and the copyeditors apologize for the mistakes in the original version of this article. The original article has been corrected.

Effect of Siderophore on Iron Availability in a Diatom and a Dinoflagellate Species: Contrasting Response in Associated Bacteria

Organic ligands play a key role controlling trace metal bioavailability in the world oceans, yet the species-specific requirements determining whether certain iron forms can be metabolized largely remain unclear. Siderophores are considered relevant within this pool of ligands keeping iron soluble. We used desferrioxamine B (DFB) to study the siderophore effect on cultures of Skeletonema costatum and Alexandrium catenella. The experimental approach used semi-continuous additions of iron(II) and DFB over time, reaching final concentrations of 1 and 10 nM Fe and 10-10000 nM DFB. The negative effect of DFB over growth in S. costatum was evident and sharp until day 9 for treatments above 500 nM. Delayed growth occurred at 10000 nM, reaching ~ 80 % of cell density in Controls under both iron conditions. A. catenella exhibited a more attenuated negative effect of DFB over growth, only significant at 10000 nM, while growth was enhanced at lowest DFB. Total bacterial abundance in diatom and dinoflagellate cultures presented inversed trends. While negatively correlated to DFB in diatom cultures, bacteria in high DFB treatments in dinoflagellate cultures reached highest abundances. Delayed growth exhibited in S. costatum at the highest DFB, indicates favorable changes for Fe uptake occurred over time, suggesting involvement of other mechanism facilitating the diatom cell membrane reduction. Overall unaffected growth in A. catenella suggests the potential to utilize FeDFB and therefore capacity to access strongly complexed Fe sources. Contrasting responses in the bacterial community associated with each species, highlight the complexity of these interactions, while suggest that for A. catenella it may represent an advantage for acquiring Fe. The DFB effect exhibited the capacity for different uptake strategies among phytoplankton species of different functional groups and underlines the necessity to broaden the study of iron bioavailability on a species basis, alongside interaction with other microbial components such bacteria, to reflect interactions in natural ecosystems.