scholarly journals Influence of coastal upwelling on micro-phytoplankton variability at Valparaíso Bay (~33ºS), Central Chile

2020 ◽  
Vol 55 (1) ◽  
pp. 11
Author(s):  
Pilar Aparicio-Rizzo ◽  
Italo Masotti ◽  
Mauricio F. Landaeta
Keyword(s):  
Thermal Stratification ◽  
Coastal Upwelling ◽  
Phytoplankton Abundance ◽  
Local Wind ◽  
Central Chile ◽  
Shadow Area ◽  
Phytoplankton Variability ◽  
Upwelling Index ◽  
Local Wind Forcing ◽  
Oceanographic Conditions

In this work 10 years of data (1986-1996) from a fixed station located in the northern part of Valparaíso Bay (33º00’S; 71º35’W) were analysed to study the influence of coastal upwelling activity on the temporal variation of micro-phytoplankton (20-200 μm) and their relationship with oceanographic conditions. The upwelling activity at the bay was associated to semi-annual wind regime with an intensification of upwelling-favourable S-SW winds from September to March followed by a decrease and the occurrence of downwelling events from April to August. Oceanographic conditions showed the ascent of cold, nutrient-rich salty water in spring (September-November). However, during summertime under highest upwelling index, thermal stratification conditions were registered. This stratification might be associated to either the solar radiation or the presence of an upwelling shadow area in the bay. The upwelling period had the highest micro-phytoplankton abundance mainly dominated by diatoms. This period was associated with an increase in biomass and richness in the bay. Meanwhile during non-upwelling period —under homogenous conditions of temperature, salinity and nutrients— an increase in diversity (but low abundance and richness) associated to dinoflagellates and silicoflagellates was noted. Therefore, the results suggest the presence of a bi-modal regime of micro-phytoplankton in the bay in response to changes in oceanographic conditions related to local wind forcing and mixing/stratification.

Detecting Subtle Seasonal Transitions of Upwelling in North-Central Chile

2015 ◽  
Vol 45 (3) ◽  
pp. 854-867 ◽  
Author(s):  
David A. Rahn ◽  
Benjamín Rosenblüth ◽  
José A. Rutllant
Keyword(s):  
Wind Stress ◽  
Large Scale ◽  
Coastal Upwelling ◽  
Southern Oscillation ◽  
Biological Productivity ◽  
Wind Stress Curl ◽  
Two Phase ◽  
North Central ◽  
Central Chile ◽  
Upwelling Index

AbstractBiological productivity in the ocean along the Chilean coast is tied to upwelling that is primarily forced by equatorward wind stress and wind stress curl on the ocean surface. Southerly alongshore flow is driven by the southeast Pacific (SEP) anticyclone, and its intensity and position vary on a range of time scales. Variability of the SEP anticyclone has been linked to large-scale circulations such as El Niño–Southern Oscillation and the Madden–Julian oscillation. The actual timing, duration, and nature of the seasonal meridional drift of the SEP anticyclone are associated with the onset, demise, and strength of the local upwelling season. Seasonal variation is especially marked at the Punta Lavapié (37°S) upwelling focus, where there is a clear upwelling season associated with a change of the cumulative upwelling index (CUI) slope between positive and negative. The Punta Lengua de Vaca (30°S) focus typically exhibits upwelling year-round and has less distinct transitions, making it more difficult to identify an enhanced upwelling season. A two-phase linear regression model, which is typically used to detect subtle climate changes, is applied here to detect seasonal changes in CUI at Punta Lengua de Vaca. This method objectively finds distinct transitions for most years. The spring-to-summer transition is more readily detected and the slackening of the upwelling-favorable winds, warmer waters, and longer wind strengthening–relaxation cycles change the coastal upwelling ecosystem. While the spring-to-summer transition at Punta Lengua de Vaca could be influenced by large-scale circulations, the actual dates of transition are highly variable and do not show a clear relationship.

scholarly journals LOCAL WIND FORCING AND SMALL SCALE UPWELLING

1982 ◽  
Vol 1 (18) ◽  
pp. 144
Author(s):  
Cairns A.R. Bain
Keyword(s):  
Wind Stress ◽  
Coastal Upwelling ◽  
Wind Forcing ◽  
Small Scale ◽  
Local Wind ◽  
Coastal Site ◽  
Sea Temperature ◽  
Stress Effects ◽  
Wind Events ◽  
Local Wind Forcing

This study characterizes some wind stress effects on a coastal site which is a focus of small scale upwelling having a scale of the order of 10 km. Two time scales are considered. Firstly the seasonal character of wind stress with the associated sea temperature fluctuations is described. Secondly individual wind events of a few days duration are characterized by extent and rate of upwelling and offshore displacement of the thermocline front. Data on the thermocline displacement is fitted to Csanady's model of coastal upwelling, which leads to the prediction of upwelling parameters for given wind events.

scholarly journals Coastal Upwelling Front Detection off Central Chile (36.5–37°S) and Spatio-Temporal Variability of Frontal Characteristics

2018 ◽  
Vol 10 (5) ◽  
pp. 690 ◽  
Author(s):  
Vera Oerder ◽  
Joaquim Bento ◽  
Carmen Morales ◽  
Samuel Hormazabal ◽  
Oscar Pizarro
Keyword(s):  
Temporal Variability ◽  
Coastal Upwelling ◽  
Central Chile ◽  
Spatio Temporal ◽  
Front Detection

scholarly journals Vertical segregation among pathways mediating nitrogen loss (N<sub>2</sub> and N<sub>2</sub>O production) across the oxygen gradient in a coastal upwelling ecosystem

2017 ◽  
Vol 14 (20) ◽  
pp. 4795-4813 ◽  
Author(s):  
Alexander Galán ◽  
Bo Thamdrup ◽  
Gonzalo S. Saldías ◽  
Laura Farías
Keyword(s):  
Coastal Upwelling ◽  
Nitrite Reduction ◽  
15N Tracer ◽  
Ammonium Oxidation ◽  
N Loss ◽  
N2o Production ◽  
Coastal System ◽  
Central Chile ◽  
N Removal ◽  
Bottom Waters

Abstract. The upwelling system off central Chile (36.5° S) is seasonally subjected to oxygen (O2)-deficient waters, with a strong vertical gradient in O2 (from oxic to anoxic conditions) that spans a few metres (30–50 m interval) over the shelf. This condition inhibits and/or stimulates processes involved in nitrogen (N) removal (e.g. anammox, denitrification, and nitrification). During austral spring (September 2013) and summer (January 2014), the main pathways involved in N loss and its speciation, in the form of N2 and/or N2O, were studied using 15N-tracer incubations, inhibitor assays, and the natural abundance of nitrate isotopes along with hydrographic information. Incubations were developed using water retrieved from the oxycline (25 m depth) and bottom waters (85 m depth) over the continental shelf off Concepción, Chile. Results of 15N-labelled incubations revealed higher N removal activity during the austral summer, with denitrification as the dominant N2-producing pathway, which occurred together with anammox at all times. Interestingly, in both spring and summer maximum potential N removal rates were observed in the oxycline, where a greater availability of oxygen was observed (maximum O2 fluctuation between 270 and 40 µmol L−1) relative to the hypoxic bottom waters ( <  20 µmol O2 L−1). Different pathways were responsible for N2O produced in the oxycline and bottom waters, with ammonium oxidation and dissimilatory nitrite reduction, respectively, as the main source processes. Ammonium produced by dissimilatory nitrite reduction to ammonium (DNiRA) could sustain both anammox and nitrification rates, including the ammonium utilized for N2O production. The temporal and vertical variability of δ15N-NO3− confirms that multiple N-cycling processes are modulating the isotopic nitrate composition over the shelf off central Chile during spring and summer. N removal processes in this coastal system appear to be related to the availability and distribution of oxygen and particles, which are a source of organic matter and the fuel for the production of other electron donors (i.e. ammonium) and acceptors (i.e. nitrate and nitrite) after its remineralization. These results highlight the links between several pathways involved in N loss. They also establish that different mechanisms supported by alternative N substrates are responsible for substantial accumulation of N2O, which are frequently observed as hotspots in the oxycline and bottom waters. Considering the extreme variation in oxygen observed in several coastal upwelling systems, these findings could help to understand the ecological and biogeochemical implications due to global warming where intensification and/or expansion of the oceanic OMZs is projected.

scholarly journals Abiotic ammonification and gross ammonium photoproduction in the upwelling system off central Chile (36° S)

2012 ◽  
Vol 9 (12) ◽  
pp. 18479-18518
Author(s):  
A. Rain-Franco ◽  
C. Muñoz ◽  
C. Fernandez
Keyword(s):  
Organic Matter ◽  
Coastal Upwelling ◽  
Archaeal Community ◽  
Simultaneous Occurrence ◽  
Diatom Species ◽  
Chaetoceros Muelleri ◽  
Central Chile ◽  
Upwelling System ◽  
Simulated Solar Radiation ◽  
Radiation Conditions

Abstract. We investigated the production of ammonium via photodegradation of dissolved organic matter (DOM) in the coastal upwelling system off central Chile (36° S). Photoammonification experiments were carried out using exudates obtained from representative diatom species (Chaetoceros muelleri and Thalassiosira minuscule) and natural marine DOM under simulated solar radiation conditions. Additionally, we evaluated the use of photoproduced ammonium by natural microbial communities and separated ammonium oxidizing archaea and bacteria by using GC-7 as an inhibitor of the archaeal community. We found photoammonification operating at two levels: via the transformation of DOM by UV radiation (abiotic ammonification) and via the simultaneous occurrence of abiotic phototransformation and biological remineralization of DOM into NH4+ (referred as gross photoproduction of NH4+). The maximum rates of abiotic ammonification reached 0.057 μmol L−1 h−1, whereas maximum rates of gross photoproduction reached 0.746 μmol L−1 h−1. Our results also suggest that ammonium oxidizing archaea could dominate the biotic remineralization induced by photodegradation of organic matter and consequently play an important role in the local N cycle. Abiotic ammonium photoproduction in coastal upwelling systems could support between 7 and 50% of the spring-summer phytoplankton NH4+ demand. Surprisingly, gross ammonium photoproduction (remineralization induced by abiotic ammonification) might support 50 to 180% of spring-summer phytoplankton NH4+ assimilation.

Local wind forcing of the Monterey Bay area inner shelf

2005 ◽  
Vol 25 (3) ◽  
pp. 397-417 ◽  
Author(s):  
Patrick T. Drake ◽  
Margaret A. McManus ◽  
Curt D. Storlazzi
Keyword(s):  
Wind Forcing ◽  
Monterey Bay ◽  
Local Wind ◽  
Inner Shelf ◽  
Bay Area ◽  
Local Wind Forcing

Influence of coastal upwelling on the surface current in the Bay of Bengal using HF radar and satellite observations

2021 ◽  
Author(s):  
Shouvik Dey ◽  
Sourav Sil ◽  
Samiran Mandal
Keyword(s):  
Coastal Upwelling ◽  
Surface Current ◽  
Hf Radar ◽  
Second Phase ◽  
Biological Productivity ◽  
Maximum Peak ◽  
Current Observation ◽  
Ekman Layers ◽  
Ocean Surface Current ◽  
Upwelling Index

&lt;p&gt;Coastal Upwelling is a phenomenon in which cold and nutrient-enriched water from the Ekman layers reaches the surface enhancing the biological productivity of the upwelling region. In this work, an attempt is made to understand the influence of coastal upwelling on surface current variations during May 2018 to August 2018, when HF radar current observation (source: NIOT, India) is available. The wind-based Upwelling Index(UI&lt;sub&gt;wind&lt;/sub&gt;) showed coastal upwelling throughout the study period. But the SST based upwelling index (UI&lt;sub&gt;sst&lt;/sub&gt;) showed upwelling occurred only from May to the first week of June. Cross-shore components of HF radar-derived ocean surface current (CSSC)&amp;#160; showed strong similarity with UI&lt;sub&gt;sst&lt;/sub&gt;. The first phase of upwelling from UI&lt;sub&gt;sst&lt;/sub&gt; is observed to start on 5&lt;sup&gt;th&lt;/sup&gt; May and lasts till 14&lt;sup&gt;th&lt;/sup&gt; May with a maximum peak on around 10&lt;sup&gt;th&lt;/sup&gt; May and having a horizontal extension of ~40 km. Then, there is a break period for about three days and after that, the second phase of upwelling starts on 17&lt;sup&gt;th&lt;/sup&gt; May and lasts till 25&lt;sup&gt;th&lt;/sup&gt; May with a maximum peak on around 20&lt;sup&gt;th&lt;/sup&gt; May, but this time the horizontal extension is ~100 km which is much larger than during the first phase. A strong positive (from coast to offshore) CSSC is observed to start on around 5&lt;sup&gt;th&lt;/sup&gt; May and lasts till 13&lt;sup&gt;th&lt;/sup&gt; May with a maximum peak on around 10&lt;sup&gt;th&lt;/sup&gt; May and having a horizontal extension of ~40 km, as observed from UIsst. A reversal of CSSC (towards coast) is noted on 14&lt;sup&gt;th&lt;/sup&gt; May when the break of coastal upwelling is evident from UI&lt;sub&gt;sst&lt;/sub&gt;. The CSSC then again started intensifying 15&lt;sup&gt;th&lt;/sup&gt; May onwards and continued for ten days till 25&lt;sup&gt;th&lt;/sup&gt; May, similar to UI&lt;sub&gt;sst&lt;/sub&gt;.&amp;#160; The horizontal extension of the upwelling signature in the second phase of upwelling is ~70 km. Therefore, a 7-10 days of the coastal upwelling and its horizontal extension are identified in this study. This study suggests the use of high resolution (~6 km) HF radar current observation on the monitoring of coastal upwelling processes.&lt;/p&gt;

Upwelling Bays: How Coastal Upwelling Controls Circulation, Habitat, and Productivity in Bays

2020 ◽  
Vol 12 (1) ◽  
pp. 415-447 ◽  
Author(s):  
John L. Largier
Keyword(s):  
Ocean Acidification ◽  
Wind Stress ◽  
Coastal Waters ◽  
Coastal Upwelling ◽  
Coastal Currents ◽  
Local Wind ◽  
Phytoplankton Blooms ◽  
Local Extrema ◽  
High Recruitment

Bays in coastal upwelling regions are physically driven and biochemically fueled by their interaction with open coastal waters. Wind-driven flow over the shelf imposes a circulation in the bay, which is also influenced by local wind stress and thermal bay–ocean density differences. Three types of bays are recognized based on the degree of exposure to coastal currents and winds (wide-open bays, square bays, and elongated bays), and the characteristic circulation and stratification patterns of each type are described. Retention of upwelled waters in bays allows for dense phytoplankton blooms that support productive bay ecosystems. Retention is also important for the accumulation of larvae, which accounts for high recruitment in bays. In addition, bays are coupled to the shelf ecosystem through export of plankton-rich waters during relaxation events. Ocean acidification and deoxygenation are a concern in bays because local extrema can develop beneath strong stratification.

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