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The 1997-98 El Niño and its effects on the coastal marine ecosystem off Peru
Abstract
We summarize the important effects of the extraordinary El Niño 1997-98 on the Peruvian marine ecosystem, and we compare these with what was observed during the extraordinary El Niño 1982-83. The SST anomalies at coastal stations, as well as data from marine explorations carried out during 1996-98, show, among other things, that the preceding cold period ended in January-February 1997; that El Niño 1997-98 was clearly defined along all the Peruvian coast in March-May 1997 (earlier in the north) and ended between April and June 1998, beginning from the south; and that El Niño was followed by a moderately cold period, evident since August 1998 (winter in the Southern Hemisphere). The most dramatic alterations in chemical characteristics were observed in December 1997 and February 1998, when low concentrations of nitrate (0.15-1.1 μg-at/L) extended south from Callao. Apparently, chemical conditions were more extreme in the water column in 1997-98 than in 1982-83, because the oxycline and nutricline were located at greater depths. Anomalously small volumes of plankton were observed, and abundant dinoflagellates and copepods typical of warm waters entered the coastal waters with the equatorial surface waters (ESW) and subtropical surface waters (SSW), similar to what occurred during El Niño 1982-83. Anchovy were found near the coast in the first phase; in the second phase they shifted toward the south and into deeper water, while sardine increased in the first phase, and then migrated to the south. Hake widened their distributional range to the south and also vertically, because this species inhabits the zone influenced by the southern extension of the Cromwell Current (SECC). On the other hand, subtropical, equatorial, and even tropical species widened their distribution, being observed off the Peruvian coast. Of special relevance was the samasa, because its abundance and distribution reached 18°S, which made it an important resource for the Peruvian fishery during El Niño 1997-98.
... El Niño (EN) influences temperature, salinity, and density, as well as the mixed layer depth, the oxycline depth, and the vertical extent of the Oxygen Minimum Zone (OMZ) (Fuenzalida et al., 2009;. Strong events, such as EN 1997/98, affect the water mass distribution and circulation, causing the deepening of the OMZ and the occurrence of high oxygenation events in the water column and the sediments along the Peruvian and Chilean coasts (Morales et al., 1999;Sánchez et al., 2000;. Likewise, during the occurrence of the weak to moderate EN events of 2002(Ledesma et al., 2011, it was recorded the deepening of the upper boundary of the OMZ from a depth of ca. 30 m to 100 m at 20 nm off Callao. ...
... La magnitud que alcanzaron las anomalías térmicas costeras en el verano 2017, de hasta +6,0 °C en promedio, fue semejante a la registrada en los eventos El Niño extraordinario de 1982-83 o 1997-98 (Carr et al., 2002;Sánchez et al., 2000). Para la zona oceánica en cambio, las anomalías térmicas registradas al este de 100° W fueron similares a las del verano 2016, en la fase final de El Niño 2015-16 (Fig. 5). ...
... In summer 2017, the magnitude reached by the coastal thermal anomalies, up to +6.0 °C on average, was similar to that recorded in the extraordinary 1982/83 or 1997/98 EN events (Carr et al., 2002;Sánchez et al., 2000). On the other hand, the thermal anomalies recorded east of 100° W were similar to those of the summer of 2016, in the final phase of EN 2015/16 (Fig. 5). ...
... El Niño (EN) influences temperature, salinity, and density, as well as the mixed layer depth, the oxycline depth, and the vertical extent of the Oxygen Minimum Zone (OMZ) (Fuenzalida et al., 2009;Espinoza et al., 2019). Strong events, such as EN 1997/98, affect the water mass distribution and circulation, causing the deepening of the OMZ and the occurrence of high oxygenation events in the water column and the sediments along the Peruvian and Chilean coasts (Morales et al., 1999;Sánchez et al., 2000;Gutiérrez et al., 2008). Likewise, during the occurrence of the weak to moderate EN events of 2002, 2006(Ledesma et al., 2011, it was recorded the deepening of the upper boundary of the OMZ from a depth of ca. 30 m to 100 m at 20 nm off Callao. ...
... Es conocido que El Niño modula la temperatura, salinidad y densidad, así como la profundidad de la capa mezcla, la profundidad de la oxiclina y la extensión vertical de la Zona de Mínimo de Oxígeno (ZMO) (Fuenzalida et al., 2009;Espinoza et al., 2019). Eventos fuertes El Niño (EN), como el de 1997-1998, afectan la distribución de masas de agua y la circulación, causando la profundización de la ZMO y la ocurrencia de eventos de gran oxigenación en la columna de agua y en los sedimentos a lo largo de las costas de Perú y Chile (Morales et al., 1999;Sánchez et al., 2000;Gutiérrez et al., 2008). Asimismo, en los eventos EN débiles o moderados de los años 2002, 2006 y 2008, (Ledesma et al., 2011) se registraron la profundización del límite superior de la ZMO de ca. ...
... La magnitud que alcanzaron las anomalías térmicas costeras en el verano 2017, de hasta +6,0 °C en promedio, fue semejante a la registrada en los eventos El Niño extraordinario de 1982de -83 o 1997de -98 (Carr et al., 2002Sánchez et al., 2000). Para la zona oceánica en cambio, las anomalías térmicas registradas al este de 100° W fueron similares a las del verano 2016, en la fase final de El Niño 2015-16 (Fig. 5). ...
En el presente estudio describimos la asociación entre la variación de la temperatura del mar y los cambios en oxigenación, fertilidad y productividad durante el período 2016 - 2017 frente a la costa peruana. Para ello se utilizaron tanto datos in situ como satelitales, con énfasis frente al norte del Perú. El Niño Costero 2017 ocasionó disminución de las concentraciones denutrientes y una reducción significativa del área productiva frente a la costa para el verano, marzo 2017, hasta de 49% particularmente al norte de Callao (12°S). En cambio, frente a la costa sur los impactos fueron débiles o inclusive se registraron concentraciones elevadas de clorofila-a, posiblemente asociadas a la recuperación más rápida del afloramiento costero en dicha región. Asimismo, durante el verano 2017 se detectaron mayores concentraciones de oxígeno disuelto que lo habitual en la capa superior de la columna de agua y poca variación en la profundidad del límite superior de la zona de mínima de oxígeno.
... During warm phases of ENSO (El Niño) a weakening of the trade winds over the equatorial Pacific and an eastward displacement of the West Pacific warm pool (Picaut et al., 1996) cause warmer sea surface temperature anomalies in the central and eastern Pacific Ocean. Off the coast of Peru this causes the mixed layer (and thermocline/nutricline) depth to increase, decreasing the nutrient content (NO − 3 and iron, Fe) of upwelled waters and leading to a decrease in phytoplankton (mainly diatoms) abundance and productivity (Barber and Chávez, 1983;Chavez, 1989;Espinoza-Morriberón et al., 2017;Sanchez et al., 2000). In contrast, the cold phases of ENSO (La Niña) are associated with a stronger Walker circulation (west-east or zonal) and upwelling-favorable winds off the coast of Peru, resulting in negative sea surface temperature (SST) anomalies (Morón, 2000), a thermocline shoaling and higher phytoplankton productivity (Espinoza-Morriberón et al., 2017). ...
... 5b, 7a). This is in agreement with phytoplankton assemblage analyses during El Niño events when productivity has been reported to be dominated by nonsiliceous phytoplankton groups (Sanchez et al., 2000), which is also observed today further off the coast of Peru ( Fig. 3a; Grasse et al., 2016). Accordingly, with the prevalence of nonsiliceous phytoplankton groups, more NO − 3 than Si(OH) 4 is utilized (Conley and Malone, 1992;Wilkerson and Dugdale, 1996) and the ratio might shift to ratios of up to 15 : 1 (Figs. ...
The stable sedimentary nitrogen isotope compositions of bulk organic matter (δ15Nbulk) and the silicon isotope composition of diatoms (δ30SiBSi) both mainly reflect the degree of past nutrient utilization by primary producers. However, in ocean areas where anoxic and suboxic conditions prevail, the δ15Nbulk signal ultimately recorded within the sediments is also influenced by water column denitrification, causing an increase in the subsurface δ15N signature of dissolved nitrate (δ15NO3-) upwelled to the surface. Such conditions are found in the oxygen minimum zone off the coast of Peru, where, at present, an increase in subsurface δ15NO3- from north to south along the shelf is observed due to ongoing denitrification within the poleward-flowing subsurface waters, while the δ30Si signature of silicic acid (δ30Si(OH)4) at the same time remains unchanged.
Here, we present three new δ30SiBSi records between 11 and 15∘ S and compare these to previously published δ30SiBSi and δ15Nbulk records from Peru covering the past 600 years. We present a new approach to calculate past subsurface δ15NO3- signatures based on the direct comparison of δ30SiBSi and δ15Nbulk signatures at a latitudinal resolution for different time periods. Our results show that, during the Current Warm Period (CWP, since 1800 CE) and prior short-term arid events, source water δ15NO3- compositions have been close to modern values, increasing southward from 7 to 10 ‰ (between 11 and 15∘ S). In contrast, during the Little Ice Age (LIA) we calculate low δ15NO3- values between 6 ‰ and 7.5 ‰. Furthermore, the direct δ30SiBSi versus δ15Nbulk comparison also enables us to relate the short-term variability in both isotope compositions to changes in the ratio of nutrients (NO3-:Si(OH)4) taken up by different dominating phytoplankton groups (diatoms and non-siliceous phytoplankton) under the variable climatic conditions of the past 600 years. Accordingly, we estimate a shift from a 1:1 (or 1:2) ratio during the CWP and a 2:1 (up to 15:1) ratio during the LIA, associated with a shift from overall high nutrient utilization to NO3--dominated (and thus non-siliceous phytoplankton) utilization.
... Observations recorded along the Peruvian and Chilean coast have shown strong water column oxygenation during 1997/1998 El Niño event. These findings have suggested an influence of ENSO variability on the vertical extent of the oxygen-poor waters (Sanchez et al., 1999;Hamersley et al., 2007;Graco et al., 2017), with a reduction of the OMZ area off Peru and northern Chile by up to 61% (Helly and Levin, 2004). Here, analysing large-scale and long-term simulated ocean dynamics under realistic 15 atmospheric forcing, we have added further insights into the influence of ENSO variability on OMZ dynamics in the ETSP. ...
... This is also the case in the offshore region, where the lower margin of the SW also shoals during El Niño events (red line inFigure 4-f). This finding is in line with the results ofSanchez et al. (1999) andStramma et al. (2016) who documented a pronounced deepening of oxygenpoor waters along the Peruvian and Chilean coast during the 1997/1998 and 2015 strong El Niño events. These results suggest 25 that the well-oxygenated waters transported eastward by the undercurrents(Stramma et al., 2010; Czeschel et al., 2015) reach and ventilate the core waters of the ETSP-OMZ during El Niño events. ...
The El Niño Southern Oscillation (ENSO) with its warm (El Niño) and cold (La Niña) phase has strong impacts on marine ecosystems off Peru. This influence extends from changes in nutrient availability to productivity and oxygen levels. While several studies have demonstrated the influence of ENSO events on biological productivity, less is known about their impact on oxygen concentrations. In situ observations along the Peruvian and Chilean coast have shown a strong water column oxygenation during the 1997/1998 strong El Niño event. These observations suggest a deepening of the oxygen minimum zone (OMZ) along the continental shelf. However, due to reduced spatial coverage of the existing in situ observations, no studies have yet demonstrated the OMZ response to El Niño events in the whole Eastern Tropical South Pacific (ETSP). Furthermore, most studies have focused on El Niño events. Much less attention was given to the oxygen dynamics under La Niña influence. Here, we provide a comprehensive analysis of the ENSO influence on OMZ dynamics. Interannual variability of the OMZ during the period 1990–2010 is derived from a regional coupled physical-biogeochemical model forced with realistic atmospheric and lateral boundary conditions. Our results show a reduction of the vertical extent and a deepening of suboxic waters (SW) during the El Niño phase. During the La Niña phase, there is a vertical expansion of SW. These fluctuations in OMZ extent are due to changes in oxygen supply into its core depth mainly from lateral margins. During the El Niño phase, the enhanced lateral oxygen supply from the subtropics is the main reason for the reduction of SW in both coastal and offshore regions. During the La Niña phase, the oxygenated subtropical waters are blocked by the poleward transport along the southern margin of the OMZ. Consequently, oxygen concentrations within the OMZ are reduced and suboxic conditions expand during La Niña. The detailed analysis of transport pathways presented here provides new insights into how ENSO variability affects the oxygen-sensitive marine biogeochemistry of the ETSP.
... It is responsible for more than 10% of the worldwide marine fish catch (Zuta and Guillén, 1970). Because of the proximity and direct connections with the Equatorial Current System (ECS) (Montes et al., 2010), the Humboldt EBUS is very sensitive to equatorial oceanic perturbations, which renders the system very sensitive to phenomena such as El Niño Southern Oscillation(ENSO) (Sanchez et al., 2000;Colas et al., 2008;Montes et al., 2011). ...
... The beginning of EN in the observations was detected along the Peruvian coast on March-97, two peaks, extremely low nitrate concentrations (less than 1 mmol N m −3 ) were measured south of Callao. Also, low nitrate concentrations (< 5 mmol N m −3 ) were observed just above 100 m deep along the Peruvian coast (Sanchez et al., 2000). Thus our model results are consistent with the observations. ...
The response of the ocean biogeochemistry to intense El Niño Southern Oscillation (ENSO) events in the Northern Humboldt Current System (NHCS) is assessed with an eddy-resolving coupled physical-biogeochemical model. El Niño (EN) 1997-1998 and La Niña (LN) 1999-2000 are well reproduced, inducing large spatial and temporal variability of biogeochemical properties at three coastal upwelling centers along the Peruvian coast (Chimbote 9.4°S, Callao 12.1°S, and Pisco 14°S). During EN, the upper limit of the Oxygen Minimum Zone (OMZ) experiences an offshore displacement of, aproximately, 60 km and a deepening of, approximately, 150 m when compared to neutral-ENSO conditions, thus ventilating the upper 100 m of the water column. In contrast, during LN, the OMZ tongue outcrops over the continental shelf deoxygenating the water column at all locations. During LN, at the southernmost location, enhanced Eddy Kinetic Energy (EKE) induces a leaking of the coastal nutrient inventory by horizontally advecting nitrogen from the nearshore region into the oligotrophic ocean. This leads to a reduction of biological production in the coastal zone. During EN, nitrification is an order of magnitude larger than denitrification in supplying the nitrite coastal pool. During LN peak, nitrification is reduced by 80%, while denitrification becomes equally important, evidencing a coupling between these two oxygen-dependent processes. The nitrogen removal due to suboxic activity is mostly controlled by the Anaerobic Ammonium Oxidation (Anammox) in the southern domain during neutral-ENSO conditions. Our results show that during EN, denitrification contributes with 60% of the total nitrogen removal. In contrast, Anammox contributes with 70% during LN. The outgassing of nitrous oxide (N2O), an intermediate product of denitrification, is reduced and enhanced during EN and LN, respectively, and it is strongly modulated by the spatiotemporal variability of oxygen in the environment.
... This change in specific composition is closely related to the transition from vertically mixed to more stratified conditions. In oceanic waters, which can be found farther offshore, the phytoplankton community is dominated by dinoflagellates and large diatoms with low reproduction and assimilation rates [Ochoa and Gomez, 1981;Sanchez et al., 2000;Ochoa et al., 2010]. ...
... Consequently, during El Niño events upwelling delivers only warm, nutrient-poor waters to the surface due to a deepened thermocline [Huyer et al., 1987]. Tropical surface waters reach the Peruvian coast [Sanchez et al., 2000] reducing PP by about 50% and shifting the phytoplankton community to dinoflagellates and large subtropical diatom species [Barber and Chávez, 1983;Chavez, 1989]. In contrast, La Niña events are associated with a stronger Walker (west-east or zonal) circulation and a thermocline shoaling resulting in an intensification of the coastal cold tongue. ...
New records of stable silicon isotope signatures (δ30Si) together with concentrations of biogenic opal and organic carbon from the central (9° S) and northern (5° S) Peruvian margin reveal changes in diatom productivity and nutrient utilization during the past 20,000 years. The findings are based on a new approach using the difference between the δ30Si signatures of small (11-32μm) and large (>150μm) diatom fractions (Δ30Sicoscino-bSi) in combination with the variance in diatom assemblages for reconstruction of past upwelling intensity. Combination of our records with two previously published records from the southern upwelling area off Peru (12-15° S) shows a general decoupling of the environmental conditions at the central and southern shelf mainly caused by a northward shift of the main upwelling cell from its modern position (12-15° S) towards 9° S during Termination 1. At this time only moderate upwelling intensity and productivity levels prevailed between 9° S and 12° S interpreted by a more northerly position of Southern Westerly Winds and the South Pacific Subtropical High. Furthermore, a marked decrease in productivity at 12-15° S during Heinrich Stadial 1 coincided with enhanced biogenic opal production in the Eastern Equatorial Pacific, which was induced by a southward shift of the Intertropical Convergence zone and enhanced northeasterly trade winds. Modern conditions were only established at the onset of the Holocene. Past changes in preformed δ30Si signatures of subsurface waters reaching the Peruvian Upwelling System did not significantly affect the preserved δ30Si signatures.
... Two temperature peaks were observed in mid 1997 and early 1998, and the surface temperature reached as warm as 26°C, compared to the normal year of only about 14-16°C (Zuta and Guillen, 1970;Colas et al., 2008). Phytoplankton volume was reduced by about 75% along the coast and dropped from the coast to more than 108 km (60 nautical miles) offshore (Sanchez 2000;Sanchez, et al. 2000;Alheit and Niquen, 2004). ...
... These shifts in spatial distribution are also consistent with observations. Sanchez et al. (2000) suggested during February and April cruises in 1997, anchovy were found between 7-8°S and 9-12°S. Ganoza et al. (2000) showed that anchovy major population located from 9-19°S within 100 km inshore during 1998 spring (November-December) cruise. ...
The coastal waters of Peru support the world's largest single-species fishery, the Peruvian anchovy. The Peruvian anchovy catch vary dramatically year-to-year in response to the El Niño Southern Oscillation (ENSO). This dissertation uses a coupled physical-biological modeling approach to investigate the response of anchovy growth, survival, and distribution to seasonal and ENSO climatic variability.
A bioenergetics model was developed for the Peruvian anchovy that simulated growth and survival from egg to age-3. The model used constant temperature and concentrations of multiple plankton groups as input. The model simulated weight and length over time generally agreed with available field and laboratory observations. Sensitivity analyses showed that the model was robust in response to variation in temperature and prey.
The modeled monthly output from the Regional Ocean Model System (ROMS), coupled with the Carbon Silicate Nitrogen Ecosystem model (CoSINE), was used as input to the bioenergetics model to study growth and survival to recruitment length (5 cm). Anchovy cohorts showed faster growth in the early and the late parts of the year, and sensitivity analysis showed the importance of prey and that realistic distribution of monthly spawning yielded high recruitment. Simulation of monthly cohorts for the 1991-2007 period showed that anchovy grew extremely slowly and had low recruitment during 1997-1998 El Niño. Sensitivity analysis showed that both temperature and prey concentrations regulated anchovy growth during normal years, while temperature was critical during El Niño conditions.
Similar analyses were performed using the three-dimensional (3D) model output from the ROMS-CoSINE simulation and adding currents and behavioral movement to individuals in the bioenergetics model. Simulated growth and survival showed similar interannual variation as with the Box Model analysis. The more detail in the 3D case allowed anchovy to locate better conditions, which explained most situations when Box Model and 3D results differed. During El Niño events, however, both Box Model and 3D analyses predict slow growth and low recruitment because of harsh environmental conditions.
Coupling physical and ecological models offers a promising method for studying the complex responses of fish populations to environmental variation, which can be potentially used for ecological forecasting and fishery management.
... Two temperature peaks were observed in mid-1997 and early 1998, and the surface temperature reached 26 • C, compared to the 14-16 • C typical in normal years (Zuta and Guillen, 1970;Colas et al., 2008). Phytoplankton volume was reduced by about 75% along the coast and dropped from the coast to more than 108 km (60 nautical miles) offshore (Sanchez, 2000;Sanchez et al., 2000;Alheit andÑiquen, 2004). Zooplankton volume remained low during 1997-1998 (Ayon et al., 2004, corresponding with the low phytoplankton biomass. ...
... These shifts in spatial distribution are also consistent with observations. Sanchez et al. (2000) showed that during cruises in February and April 1997, anchovy were found between 7-8 • S and 9-12 • S. Ganoza et al. (2000) showed that the major locus of the anchovy population was located from 9 • S to 19 • S within 100 km from shore during the spring of 1998 (November-December) cruise. For comparison, during the spring of 1996, the population was spread from 5 • S to 17 • S and extended as far as 200 km from the coast. ...
A hydrodynamic-biogeochemical model was coupled to an individual-based fish model (IBM) to study the influence of physical and biological processes on Peruvian anchovy recruitment. Temperature and the concentrations of four plankton groups from a 1991 to 2007 simulation of a Pacific basin-scaled Regional Ocean Model System (ROMS) coupled with the Carbon Silicate Nitrogen Ecosystem (CoSiNE) model were used as inputs to the anchovy IBM. The anchovy IBM domain covered the upwelling area (0–20°S and 70–85°W) from 0 to 100 m depth, and was 166 by 120 cells with 10 vertical. A cohort of eggs was started each month from 1991 to 2007, and individuals within each cohort followed through daily development, growth, mortality, and movement for one year. Growth was represented with a bioenergetic equation that used temperature and plankton concentrations from the ROMS–CoSiNE simulation as input. Mortality rate was stage-dependent and length-dependent. Movement of eggs and larvae was based on passive transport, and movement of juveniles and adults was a combination of passive transport and behavioral movement. Average number of days required to reach 5 cm and the number surviving to 5 cm were used as measures of recruitment. Averaged temperature and plankton concentrations within the IBM spatial domain showed strong interannual variation, and spatial and temporal patterns typical of the Peruvian upwelling system. Modeled anchovy growth and survival also showed strong interannual variation that resulted in large fluctuations in recruitment. Growth in a normal year resulted in anchovy requiring about 60–80 days to reach 5 cm and the number of recruits was around 1010. Averaged anchovy length and number of survivors after 6 months for all monthly cohorts combined showed that good growth conditions and high survival occurred in the region from 5°S to 17°S, within 200 km offshore and in the upper 100 m. Vertically, centers of population distribution occurred at depths of 10 m and between 50 and 70 m. During the 1997–1998 El Niño, anchovy growth rate decreased so that it took fish 150–270 days to reach 5 cm, and the numbers of survivors was about five orders of magnitude lower. Model results showed anchovy during El Niño conditions were located closer to shore, farther south, and at deeper depths than in normal years. Model results of interannual variation were insensitive to the length of anchovy used to define recruitment, how passive transport and behavioral movement were combined within different life stages, and to the starting locations of the monthly egg cohorts within the IBM domain. We discuss how our results can be used to infer anchovy recruitment under future climate change.
... Frente a las costas de Perú, a escala intraestacional, la propagación periódica de ondas Kelvin atrapadas a la costa, más frecuentes e intensas durante El Niño, ventila la columna de agua (Morales et al. 1991. En los Niños extraordinarios de 1982/1983 y 1997/1998 el borde superior de la ZMO frente a Perú se profundizó 300 m desde su posición media (50 m) (Arntz et al. 1991, Sánchez et al. 2000. La variación del régimen de oxígeno a escalas temporales mayores es en cambio menos conocida. ...
... A diferencia de la variación exhibida por el contenido de clorofila-a, varios indicadores ecológicos en el SCHP muestran una señal interdecadal dominante. Desde la década de 1960, el volumen de fitoplancton en las primeras 30 millas a lo largo de la costa peruana experimentó un período de marcada disminución entre 1976 a 1987 (Sánchez 2000), aunque en la franja de los 30 y 60 mn de la costa muestra un aumento considerable desde fines de la década de los años ochenta (S. Sánchez, IMARPE, com. ...
Durante por los menos las últimas tres décadas, varias señales del calentamiento global han sido observadas en el océano Pacífico, que consisten en el aumento de las temperaturas superficiales del mar, el aumento de la estratificación térmica, así como la expansión de las zonas mínimas de oxígeno. Paralelamente, las series de tiempo disponibles sugieren una disminución de la temperatura superficial del mar desde la costa central del Perú hasta la costa norte de Chile, así como una tendencia positiva en la productividad primaria cerca de la costa. Otros parámetros oceanográficos, como la profundidad de la oxíclina, así como indicadores ecosistémicos en niveles tróficos superiores de cambios poblacionales y de distribución exhiben una fuerte variabilidad interdecadal que limita la determinación de tendencias recientes. Para el futuro, un alto grado de incertidumbre caracteriza los modelos regionales para las respuestas de corto y mediano plazo del sistema acoplado océano-atmósfera al calentamiento global en el Pacífico sudeste. Los modelos actuales convergen en general hacia un calentamiento significativo y a un aumento de la estratificación termal. Para el dominio costero, hay dos posibles escenarios en debate: el primero postula una intensificación del afloramiento costero debido a interacciones tierra-atmósfera-océano, mientras que el segundo visualiza un debilitamiento del afloramiento costero, asociado al debilitamiento de los vientos alisios y de la Circulación de Walker. Dicha incertidumbre refleja nuestro limitado conocimiento de los procesos físicos locales y regionales que pueden amplificar o amortiguar los efectos del calentamiento global. No obstante, considerando la variabilidad interdecadal o la inercia de las tendencias actuales, el primer escenario (enfriamiento costero) parece ser más probable en la próxima década, mientras que el escenario de calentamiento se desarrollaría con mayor probabilidad a más largo plazo o cuanto menor sea la mitigación de los gases de efecto invernadero. Ambos escenarios pueden desplazar al sistema de afloramiento costero fuera de la ‗ventana óptima ambiental‘ que sostiene a la inmensa población de la anchoveta, debido a la compresión de su hábitat natural o por la disminución en el éxito del reclutamiento. Un aspecto crítico para la evolución futura del sistema de afloramiento es si la capa mínima de oxígeno se aproximará a la superficie asociada a la intensificación de la estratificación termal, o si por el contrario se profundizará a causa de una mayor ventilación subsuperficial y de la reducción de la respiración en la columna de agua. En cualquiera de los casos se hacen necesarias medidas de adaptación para las pesquerías y las comunidades locales con el fin de aminorar la vulnerabilidad del ecosistema, sus recursos y pesquerías y de las poblaciones humanas costeras.
Palabras claves: Sistema de afloramiento costero, Perú, cambio climático, interacciones tierra-océano-atmósfera, vientos costeros, ventana óptima ambiental, oxígeno, pesquerías.
ABSTRACT
Several signs of global warming effects on the Pacific Ocean have been observed, consisting of an increase of sea surface temperatures, increase in thermal stratification, as well as and expansions of the oxygen minimum zones for at least the past three decades. At the same time, available time-series strongly suggest coastal cooling, that is detectable from Central Peru to Northern Chile, and an increasing trend of primary productivity off the Peruvian coast. Other oceanographic parameters, e.g. oxycline depth, as well as high trophic level ecosystem indicators of changes in population and distribution, show a substantial interdecadal variability that limits the determination of any recent trend. In the future, a high degree of uncertainty characterizes the regional models for the short and medium term responses of the ocean-atmosphere coupled system to global warming in the South Eastern Pacific. Nevertheless, most of the models converge towards a significant warming and an increase of the thermal stratification offshore. For the coastal domain, two scenarios are under debate; the first one states an intensification of coastal upwelling due to land/atmosphere/ocean regional feedbacks, whereas, the second one envisions a weakening of coastal upwelling due to the large-scale weakening of trade winds and the Walker circulation. That uncertainty reflects our limited current knowledge of those physical processes at regional/local scale that might amplify or buffer the global warming effects. However, taking into account the persistence of interdecadal variability and/or the inertia of the current trend, the first scenario is most likely to develop for the next decade, whereas the longer the time-horizon and the weaker the global mitigation of greenhouse emissions are, the more likely would be the warming scenario. For both scenarios, the physical changes could drive the Peruvian upwelling system away from the ‗optimum environmental window‘ that supports the huge anchovy population, due to the compression of its habitat and/or the decrease of its current recruitment. A critical issue for the future evolution of the Peruvian upwelling ecosystem is whether oxygen-depleted waters will shoal in tune with large-scale thermal stratification, or if they will be deepened due to increased subsurface ventilation and lower organic matter respiration in the water column. In any case adaptation measures for the fisheries and local communities are necessary, in order to lessen the vulnerability of the ecosystem, resources, fisheries and human coastal communities.
... It has been demonstrated that climatic events such as El Niño can also significantly decrease fish populations and therefore increase pressure on fish oil /meal supply (Barlow, 2000;Lehodey, et al., 2006;Gutierrez, et al., 2007). One quarter of the world's fish oil supply and one third of the fish meal for aquaculture diets come from one anchoveta (Engraulis ringens) fishery off the coast of Peru (Schwartzlose, et al., 1999;Sanchez, et al., 2000). Collapse of this fishery alone would increase the pressure on world fish meal and oil supply and threaten global aquaculture production security (Schwartzlose, et al., 1999;Sanchez, et al., 2000). ...
... One quarter of the world's fish oil supply and one third of the fish meal for aquaculture diets come from one anchoveta (Engraulis ringens) fishery off the coast of Peru (Schwartzlose, et al., 1999;Sanchez, et al., 2000). Collapse of this fishery alone would increase the pressure on world fish meal and oil supply and threaten global aquaculture production security (Schwartzlose, et al., 1999;Sanchez, et al., 2000). ...
... Based on an El Niño event that occurred in 2014, Conde et al. (2018) concluded that the phytoplankton community composition changed at different stages of this weak El Niño. However, research about the responses of phytoplankton biomass to climate modes in the Pacific Ocean has primarily focused on coastal areas, such as the Peruvian upwelling system in the eastern equatorial Pacific (Barber & Chávez, 1986;Carr, 2003;Carr et al., 2002;Espinoza-Morriberon et al., 2017;Mogollon & Calil, 2017;Sánchez et al., 2000) and the California Current system in the northeast Pacific (Cordero-Quiros et al., 2019), due to larger abundance of observations. There have been fewer studies that have examined the responses of phytoplankton chlorophyll in the western Pacific (Blanchot et al., 1992;Salihoglu, 2009). ...
The present study aims to investigate the influences of El Niño and Southern Oscillation (ENSO) events on chlorophyll biomass in the tropical Pacific under historical and RCP8.5 scenarios with simulations from the Community Earth System Model Large Ensemble (CESM‐LE) project. Large variance in surface chlorophyll concentrations is identified across the Peruvian Upwelling (PU), Equatorial Upwelling (EU), and Western Pacific (WP) regions within the tropical Pacific. Results suggest that responses of surface chlorophyll to ENSO in these regions are governed by different mechanisms. The increasing chlorophyll during La Niña is a consequence of increasing nutrients, influenced by local upwelling systems in the PU and EU regions, while the supplementary nutrients in the WP region arise from the eastern Pacific through stronger surface westward currents. Under RCP8.5 scenario, stronger water warming in the eastern equatorial Pacific leads to a remarkable reduction in the amplitudes of seasonal cycles and interannual variations of chlorophyll in both PU and EU regions. This results in less responsiveness of the chlorophyll biomass to El Niño and moderate La Niña compared to the historical period. However, though warming induces a decrease in chlorophyll concentrations in the WP region, the interannual variations of chlorophyll have shown an improvement in correlation with ENSO events. Meanwhile, despite the small phytoplankton‐dominated community being observed under future scenario, species dominance is likely to shift back to diatoms once extreme La Niña occurs, which is unseen in all El Niño and moderate La Niña cases.
... Durante El Niño 1997-98 frente a Perú, la distribución de la caballa estuvo asociada a las ASS, con temperaturas entre 19° a 21°C y una concentración de oxígeno mayor a 5 mL×L -1 (Sánchez et al., 2000). ...
Fish populations of the Humboldt Current System exhibit contractions or
expansions in their distribution in response to the intensity of the coastal upwelling
and oxygen deficiency at different time scales. However, the future impact of global
warming on fish populations is uncertain. The objective of the present research is
to reconstruct the responses in abundance and spatial distribution of the current
main fishery resources (anchovy, hake and others) off Peru to oceanographic
changes (temperature, deoxygenation and productivity) during Termination 1 (T1,
17.5-11.5 Kyrs BP). Fish remains were analyzed in laminated sediments extracted
off Callao (M772-005-3;12.09°S,79.52°W). The palaeoceanographic record
obtained off Callao were first compared with proxies of productivity, oxygenation
and sea surface temperature and then with similar records obtained off Pisco
(14.29°S,76.76°W) and Chimbote (09.30°S,79.52°W).
The results showed that anchovy vertebrae and bones fluxes were correlated with
the depth where the core was retrieved. This suggests that sea level increase is the
main factor that controls abundance of fish off Peru during T1. The fish productivity
was lower off Callao than off Chimbote or Pisco during T1. Hake fluxes exhibited
a latitudinal gradient during T1, with greater fluxes off Chimbote and lower fluxes
off Pisco. On the other hand, the abundance of oceanic fish (sardines, horse
mackerel and mackerel) was greater off Callao than Chimbote y Pisco during the
last part of T1. However, oceanic fishes did not show a significant relationship with
oxygenation, as it would be expected based on observations from the last decades.
... The passage of downwelling CTWs, which are more frequent and intense during El Niño in the Eastern Pacific (EN), deepen the OMZ upper limit Graco et al., 2017), while upwelling CTWs have the opposite effect of causing the OMZ to shoal (Espinoza-Morriberón et al., 2019). Therefore, Eastern Pacific EN events are associated with a deepening of the OMZ, exposing the shelf off Peru and northern Chile to oxygenated waters (Morales et al., 1999;Sánchez et al., 1999;Gutiérrez et al., 2008;Graco et al., 2017). ...
The epoch of the Anthropocene, a period during which human activity has been the dominant influence on climate and the environment, has witnessed a decline in oxygen concentrations and an expansion of oxygen depleted environments in both coastal and open ocean systems since the middle of the 20th century. This paper provides a review of system-specific drivers of low oxygen in a range of case studies representing marine systems in the open ocean, on continental shelves, in enclosed seas and in the coastal environment. Identification of similar and contrasting responses within and across system types and corresponding oxygen regimes is shown to be informative both in understanding and isolating key controlling processes and provides a sound basis for predicting change under anticipated future conditions. Case studies were selected to achieve a balance in system diversity and global coverage. Each case study describes system attributes, including the present-day oxygen
environment and known trends in oxygen concentrations over time. Central to each case study is the identification of the physical and biogeochemical processes that determine oxygen concentrations through the tradeoff between ventilation and respiration. Spatial distributions of oxygen and time series of oxygen data provide the
opportunity to identify trends in oxygen availability and have allowed various drivers of low oxygen to be distinguished through correlative and causative relationships. Deoxygenation results from a complex interplay of hydrographic and biogeochemical processes and the superposition of these processes, some additive and others
subtractive, makes attribution to any particular driver challenging. System-specific models are therefore required to achieve a quantitative understanding of these processes and of the feedbacks between processes at varying scales.
... Esto influye la respuesta biológica de muchas especies durante los eventos de El Niño. Por ejemplo durante El Niño 1997-1998, el cual según McPhaden (1999 ha sido el más fuerte que se ha registrado en el Pacífico Ecuatorial, en la costa de Perú hubo una drástica disminución en la concentración de nitrato debido a que la oxiclina y la nutriclina se localizaron a grandes profundidades, provocando una migración de la anchoveta (Engraulis sp.) y la sardina (Sardinops sp.) hacia el sur y algunas zonas más profundas y ocasionando graves consecuencias para la economía (Sánchez et al., 2000). ...
In December 2008 and 2009 were carried out cruises for the evaluation of small pelagic fishes resources (Peq Pelag 0812 y 0912). With the purpose of increasing the knowledge about the space-time dynamics of the anchovy resources in the Colombian Pacific (locally known as “carduma”) and its relation with environmental conditions, in each cruise a grid of 114 stations was used with a coverage of the entire continental shelf, where it was taken discrete surface temperature measurements (TSM, Spanish acronym), salinity (SSM, Spanish acronym), transparency, and for 2009 also chlorophyll, turbidity and oxygen, and additionally for that cruise it was evaluated the oceanographic behavior of the water column based on CTDO profiles. During December 2009, TSM, SSM and transparency where higher than 2008. Differences were due to La Niña in 2008 and El Niño in 2009. In this last period the thermocline was weaker and deeper, especially south of Cabo Corrientes. Probably, this condition reduced the concentration of chlorophyll in surface, because it could have created a barrier for the dilution of nutrients within the euphotic zone. La Niña - El Niño cycle generates persistent changes in the environment that are likely to end in altering the marine populations. In the case of anchovy of the Colombian Pacific, evidences show that reproductive disturbances and the consequent reduction in the catch during the past years are caused by the wide range of oceanographic conditions as result of the sequential presence of these anomalous events.
... During this event, coastal waters off Peru showed a pronounced positive sea surface temperature anomaly of up to 4 • C (Echevin et al., 2018;Garreaud, 2018), as a result of strong local alongshore wind anomalies and equatorial Kelvin waves propagating towards the Peruvian coast (Echevin et al., 2018;Peng et al., 2019). Due to a deepening of the thermocline, nutrients, such as DSi, do not upwell to the surface, causing nutrient-depleted conditions and a shift in the phytoplankton community from diatom-dominance (Blasco, 1971;Estrada and Blasco, 1985;DiTullio et al., 2005) to species such as dinoflagellates (Sanchez et al., 2000;Bach et al., 2020). During the coastal EN in 2017 remained lower in the surface ocean ranging on average from 4 to 16 µmol L −1 from north to south, with lowest DSi of 4 to 6 µmol L −1 north of 3.5 • S and higher concentrations of 9.0 to 15.9 µmol L −1 between 10 and 15 • S ( Figure 3D). ...
The global silicon (Si) cycle plays a critical role in regulating the biological pump and the carbon cycle in the oceans. A promising tool to reconstruct past dissolved silicic acid (DSi) concentrations is the silicon isotope signature of radiolaria (δ³⁰Sirad), siliceous zooplankton that dwells at subsurface and intermediate water depths. However, to date, only a few studies on sediment δ³⁰Sirad records are available. To investigate its applicability as a paleo proxy, we compare the δ³⁰Sirad of different radiolarian taxa and mixed radiolarian samples from surface sediments off Peru to the DSi distribution and its δ³⁰Si signatures (δ³⁰SiDSi) along the coast between the equator and 15°S. Three different radiolarian taxa were selected according to their specific habitat depths of 0–50 m (Acrosphaera murrayana), 50–100 m (Dictyocoryne profunda/truncatum), and 200–400 m (Stylochlamydium venustum). Additionally, samples containing a mix of species from the bulk assemblage covering habitat depths of 0 to 400 m have been analyzed for comparison. We find distinct δ³⁰Sirad mean values of +0.70 ± 0.17‰ (Acro; 2 SD), +1.61 ± 0.20 ‰ (Dictyo), +1.19 ± 0.31 ‰ (Stylo) and +1.04 ± 0.19 ‰ (mixed radiolaria). The δ³⁰Si values of all individual taxa and the mixed radiolarian samples indicate a significant (p < 0.05) inverse relationship with DSi concentrations of their corresponding habitat depths. However, only δ³⁰Si of A. murrayana are correlated to DSi concentrations under normally prevailing upwelling conditions. The δ³⁰Si of Dictyocoryne sp., Stylochlamydium sp., and mixed radiolaria are significantly correlated to the lower DSi concentrations either associated with nutrient depletion or shallower habitat depths. Furthermore, we calculated the apparent Si isotope fractionation between radiolaria and DSi (Δ³⁰Si ∼ ³⁰ε = δ 30Sirad − δ 30SiDSi) and obtained values of −1.18 ± 0.17 ‰ (Acro), −0.05 ± 0.25 ‰ (Dictyo), −0.34 ± 0.27 ‰ (Stylo), and −0.62 ± 0.26 ‰ (mixed radiolaria). The significant differences in Δ³⁰Si between the order of Nassellaria (A. murrayana) and Spumellaria (Dictyocoryne sp. and Stylochlamydium sp.) may be explained by order-specific Si isotope fractionation during DSi uptake, similar to species-specific fractionation observed for diatoms. Overall, our study provides information on the taxon-specific fractionation factor between radiolaria and seawater and highlights the importance of taxonomic identification and separation to interpret down-core records.
... The passage of downwelling CTWs, which are more frequent and intense during El Niño in the Eastern Pacific (EN), deepen the OMZ upper limit Graco et al., 2017), while upwelling CTWs have the opposite effect of causing the OMZ to shoal (Espinoza-Morriberón et al., 2019). Therefore, Eastern Pacific EN events are associated with a deepening of the OMZ, exposing the shelf off Peru and northern Chile to oxygenated waters (Morales et al., 1999;Sánchez et al., 1999;Gutiérrez et al., 2008;Graco et al., 2017). ...
The epoch of the Anthropocene, a period during which human activity has been the dominant influence on climate and the environment, has witnessed a decline in oxygen concentrations and an expansion of oxygen-depleted environments in both coastal and open ocean systems since the middle of the 20th century. This paper provides a review of system-specific drivers of low oxygen in a range of case studies representing marine systems in the open ocean, on continental shelves, in enclosed seas and in the coastal environment. Identification of similar and contrasting responses within and across system types and corresponding oxygen regimes is shown to be informative both in understanding and isolating key controlling processes and provides a sound basis for predicting change under anticipated future conditions. Case studies were selected to achieve a balance in system diversity and global coverage. Each case study describes system attributes, including the present-day oxygen environment and known trends in oxygen concentrations over time. Central to each case study is the identification of the physical and biogeochemical processes that determine oxygen concentrations through the tradeoff between ventilation and respiration. Spatial distributions of oxygen and time series of oxygen data provide the opportunity to identify trends in oxygen availability and have allowed various drivers of low oxygen to be distinguished through correlative and causative relationships. Deoxygenation results from a complex interplay of hydrographic and biogeochemical processes and the superposition of these processes, some additive and others subtractive, makes attribution to any particular driver challenging. System-specific models are therefore required to achieve a quantitative understanding of these processes and of the feedbacks between processes at varying scales.
... During the El Niño event, the total biomass of the ecosystem decreased, which mainly resulted from a remarkable decrease in primary production under climate variability. This trend is consistent with the findings from relevant studies of El Niño events elsewhere (Sanchez et al., 2000;Franco-Gordo et al., 2004;Hays et al., 2005;Zhao and Tang, 2007;Jackson et al., 2010) that caused dramatic variations in the entire ecosystem through bottom-up control. Tang et al. (2003) and Liu et al. (2019) suggested that El Niño may be one of the dominant factors driving the annual variation of phytoplankton in the Bohai and Yellow Sea. ...
El Niño events have great impacts on marine ecosystems worldwide, ranging from low trophic plankton production to fishery resources. Understanding how ecosystems respond to El Niño is the key to the success of ecosystem-based fisheries management (EBFM). However, few studies have focussed on the ecosystems respond to this natural perturbation in China seas, and the selection of effective ecological network analyses (ENA) indicators to evaluate the ecosystem response under El Niño conditions needs to be assessed. In this study, we constructed Ecopath models for Haizhou Bay in ENSO-neutral (2013) and El Niño (2015) years. Comprehensive analyses were conducted to evaluate ENA indicators in terms of sensitivity to the ecosystem variations, robustness to the model parameters uncertainties, and statistical check. Results showed that there were obvious variations in the species composition and biomass in the Haizhou Bay ecosystem under the El Niño event. Four optimal ENA indicators were selected, including total system throughput, total primary production, total system non-cycled throughflow, and ascendency. The indicators further showed a shrunken ecosystem size, increased energetic efficiency, and less organised ecosystem under the El Niño event. These findings enhance our understanding of ecosystem dynamics and underscore the need for precautionary management under El Niño conditions. Moreover, this work can be helpful in guiding the further selection of ENA indicators for evaluating and managing marine ecosystems during El Niño events elsewhere and thusly contribute to the implementation of EBFM.
... As a result, various groups along the food chain were affected, such as macroalgae species that disappeared from the intertidal zone (Vinueza et al. 2006); corals that suffered from bleaching (Reyes-Bonilla et al. 2002, Brainard et al. 2018; fisheries (e.g. jack mackerel in Chile and anchovy in Peru) (Sánchez et al. 2000, Arcos et al. 2001; sea lions that showed decreased reproductive success (Sielfeld & Guzmán 2002); and fin whales, for which a reduction in density was observed (Benson et al. 2002). ...
The El Niño-Southern Oscillation (ENSO), which includes El Niño and La Niña phases, affects oceanographic conditions and primary productivity of marine ecosystems at a global scale. During El Niño events, warm temperatures in the central and eastern tropical Pacific decrease primary productivity, affecting the biology of many species including sea turtles. We aimed to determine the effect of ENSO (as a global index) and primary productivity in the foraging areas (as a local index) on remigration intervals (number of years between nesting seasons) and seasonal reproductive output (clutch size and number of clutches in a season) of green turtles Chelonia mydas in the North Pacific off Costa Rica, an area highly influenced by ENSO. We used the Multivariate ENSO Index (MEI) and mean values of chlorophyll a from previously identified feeding areas for this population over different time periods (up to 3 yr before the nesting season). Chlorophyll a levels in foraging areas and MEI strongly influenced the reproductive frequency of green turtles. Variability in the remigration intervals was better explained by models that included MEI conditions 2 and 3 yr before the onset of the nesting season and chlorophyll levels in the previous 3 yr. Models using global and local indexes were equally good at predicting changes in the remigration intervals. Positive values of MEI (El Niño phase) and lower levels of chlorophyll a corresponded to longer remigration intervals. No statistically significant relationships were found between seasonal reproductive output and MEI or chlorophyll a levels. As El Niño events may become more frequent and last longer due to climate change, the lifetime reproductive output of green turtles in this area may be compromised in the future.
... Una capa deficiente de oxígeno (< 0.5 ml L-1), conocida como zona de mínimo oxígeno (ZMO), se ensancha, engrosa y es más intensa de norte a sur frente a la costa del Perú (Wooster & Gilmartin, 1961). Frente a los 5° S, el borde superior de la capa de mínima tiende a situarse debajo de los 100 m de profundidad; mientras que frente al Callao (12° S) la mínima de oxígeno puede extenderse hasta los 30-40 m debajo de la superficie (Sánchez et al., 2000). ...
The Peruvian continental margin includes the continental shelf and the continental slope. Its width can vary from 126 km off the coast of Pimentel, to 5 km in the south of Peru. The Peruvian - Chilean trench has a distance of more than 2100 km off the Peruvian coast and reaches a maximum depth of 7,415 m. Interpretation of the information obtained by geophysical prospecting methods, has delineated a rugged and dynamic seabed, with deep canyons, channels and geoforms of underwater landslides. The canyons dissect the slope in the form of “V”, their headwaters generally occur at the edge of the platform and continue towards the pit, channeling sediments from the basins of the upper upper slope into the pit. Between 6 ° and 9 ° 30’, 16 ° and 18 ° south latitude, the canyons are
between 2 and 14 km wide and between 200 and 1,000 m deep.
Its tectonosedimentary configuration is defined by 9 forearc basins; Cuenca Tumbes, Talara, Lancones, Sechura, Salaverry, Lima, Pisco, Moquegua and Mollendo. These basins are arranged parallel to the coastline in a NO-SE direction. They limit each other through major tectonic surveys, called “Altos”. Thus we have the Alto of the external platform which limits the basins Salaverry, Pisco and Mollendo and the Alto of the upper slope that limits the Lima and Trujillo basins. The Alto de Paita limits the Talara and Tumbes basins and the Amotapes mountain range limits the Sechura, Talara and Lancones basins.
Within the scheme of plate tectonics, corresponds to a typical convergence margin, where the Nazca Plate interacts with the South American Plate, with active behavior, both from the tectonic and seismic point of view.
These basins are filled by Mesozoic and Cenozoic sedimentary sequences deposited generally on a Paleozoic basement. The northwest basins are large oil systems that allow the generation and entrampe of hydrocarbons. Of the more than 14,500 wells drilled in Peru, 14,000 of them are in the Talara Basin, this being one of the basins with the largest hydrocarbon production. The Tumbes and Lancones basins are next in importance. As the main generating units are the Dead formations, constituted by lime-like limestones of the Albian; the Redondo Formation with Campanian shales (Talara Basin), The Heath Formation (Tumbes Basin). As reservoir rocks we have the shales of the Talara, Ostrea and Chira formations.
In addition to hydrocarbon resources, the Peruvian continental margin contains vast mineral resources such as polymetallic nodules, manganese crusts, as well as crusts and phosphate nodules. Those that occur mainly off the northern and central coasts of Peru, formed as a result of the intense biogeochemical processes that occur in the water column and seabed. Finally, the Peruvian continental margin in all its extension constitutes the floor of a large oceanic ecosystem and high specific diversity, with oceanic current systems that control the dynamics and climatic variability in the country.
... Una capa deficiente de oxígeno (< 0.5 ml L-1) conocida como Zona de Mínimo Oxígeno (ZMO), se ensancha, engrosa y es más intensa de norte a sur frente a la costa del Perú (Wooster & Gilmartin, 1961). Frente a los 5° S, el borde superior de la capa de mínima tiende a situarse debajo de los 100 m de profundidad, mientras que frente a Callao (12°S), la mínima de oxígeno puede extenderse hasta los 30-40 m debajo de la superficie (Sánchez et al., 2000). ...
The Peruvian continental margin includes the continental and slope shelf. It corresponds to a typical convergence margin, where the Nazca Plate collides with the South American Plate, with active behavior, both from the tectonic and seismic point of view. Its width can vary from 126 km off the coast of Salaverry, to 5 km in the south. The Peruvian - Chilean trench has a continuous kilometric route and reaches a maximum depth of 7,415 m. Its tectonosedimentary configuration is defined by 9 forearc basins Tumbes, Talara, Lancones, Sechura, Salaverry, Lima, Pisco, Moquegua and Mollendo, which are arranged parallel to the coastline following a NO-SE direction. They limit each other through major tectonic surveys, called "Altos". So we have the Alto of the external platform which limits the Trujillo, Lima, Pisco oeste and Mollendo basins and the Alto of the upper slope that limits these basins to the west. The Alto de Paita limits the Talara and Tumbes basins and the Amotapes mountain range limits the Talara, Lancones and Sechura basins.
The regional geomorphological studies show a rugged and dynamic seabed with canals, submarine canyons and extensive areas of subsidence and landslides. Impressive canyons dissect the slope in the form of "V", with headings that go generally from the edge of the platform to the pit, reaching extensions of 2 to 14 km wide and an average of 200 to 1,000 m of incision, channeling sediments of the basins of the upper slope towards the Peruvian trench.
In addition to hydrocarbon resources, investigations to date, point out that the Peru Basin and the Peruvian continental margin contain potential mineral resources such as polymetallic nodules and crusts, mainly off the northern and central coasts of Peru, in the case of this last. These have originated as a result of the intense biogeochemical processes that occur in the water column and seabed. Finally, the Peruvian continental margin in all its extension constitutes the floor of a large oceanic ecosystem and high specific diversity, with oceanic current systems that control the dynamics and climatic variability in the country.
... In the Eastern Tropical (Stenella coeruleoalba) and common dolphins (Delphinus spp.) inhabit upwelling-modified waters (Au and Perryman, 1985;Reilly and Fiedler, 1994). Likewise, dolphin distributions could change at different temporal scales as a response to prevailing environmental variations, seasonally (Neumann, 2001;Würsig et al., 2007) or inter-annually during strong ENSO events Forney, 2000;Sánchez et al., 2000;Benson et al., 2002;Henderson et al., 2014). ...
Odontocete cetaceans are important predators in pelagic ecosystems; however, patterns of spatial and temporal distribution in the marine ecosystem off Peru remain unknown for many species. In this study, we modeled the potential habitats for dusky (Lagenorhynchus obscurus), long-beaked common (Delphinus capensis), bottlenose (Tursiops truncatus) and short-beaked common (Delphinus delphis) dolphins using maximum entropy models to two conditions: non-El Niño and El Niño 97-98. Dolphin sightings positions, fishing net hauls with potential prey data, and oceanographic variables from 24 cruises along the southeast Pacific coast of Peru (03°30′S-18°21′S) between 1997 and 2014 were used to model potential habitats of dolphins and their prey. Our modeling predicts that during non-El Niño conditions, the different dolphin species have a segregated distribution according to the physiography. Dusky and long-beaked common dolphins use mainly habitats over neritic zones segregating partially their spatial distribution while bottlenose and short-beaked common dolphins showed potential habitats mainly over the shelf-break and oceanic waters, respectively. During El Niño 97-98, this physiographic segregation was predicted to be maintained by the models although with northward retraction for bottlenose, long and short-beaked commons dolphins. Accordingly, dusky and long-beaked common dolphin potential habitat overlapped mainly with neritic potential prey species (Peruvian anchovy, Engraulis ringens; silverside, Odonthestes regia regia; red squat lobster, Pleuroncodes monodon; common squids, Doryteuthis gahi and mackerels). Bottlenose and short-beaked common dolphin habitats were predicted to overlap mainly with oceanic potential prey (mackerels; Panama lightfish, Vinciguerria lucetia; myctophids; Humboldt squids, Dosidicus gigas and euphausiids). Our results predict that dolphins use specific physiographic areas throughout the Peruvian marine ecosystem and these habitats did not drastically change during El Niño 97-98.
... They occurred at the same time as the disappearance of the surface sulfur plumes. These events were generally accompanied by a deepening of the oxycline (Hamersley et al., 2007) and a reduction in the OMZ volume (Gutiérrez et al., 2008;Helly & Levin, 2004;Sánchez et al., 1999). The oxygenation episodes can reduce the H 2 S formation that commonly occurs in anoxic marine sediments through microbial sulfate reduction (Jørgensen, 1982;Lein, 1984), can impact the flux of H 2 S from the upper sediment to the bottom water layer usually controlled by sulfide-oxidizing bacteria (Ferdelman et al., 1997;Schulz et al., 1999), and can provide the removal of the H 2 S-enriched water by biological (Galán et al., 2014;Lavik et al., 2009;Schunck et al., 2013) and possibly chemical oxidation processes (Gutiérrez et al., 2008). ...
For the first time, the impact of the El Niño-Southern Oscillation (ENSO) on the surface sulfur
plumes off the Peruvian upwelling system has been studied. The investigations demonstrated a strong
correlation between the ENSO and the sulfur plumes in the coastal areas of Callao and Pisco. During the El
Niño phases, the sulfur plumes disappeared almost completely because of equatorial remotely forced
oxygenation episodes. The La Niña events were associated with strong oxygen deficiency over the Peruvian
shelf, supporting the formation of hydrogen sulfide and, consequently, the occurrence of sulfur plumes. This
impact was smaller at Callao, because the La Niña phases in this coastal area were interrupted by weak
oxygenation events. During the neutral phases, oxygen-poor waters were also present in the Peruvian shelf
areas, promoting the large size of sulfur plumes. However, they were not forced by the remotely driven
processes resulting from ENSO phenomena.
... This shift 392 towards a decreased Si(OH) 4 but an increased NO 3 demand further supports a change in the nutrient 393 uptake ratio by phytoplankton (NO 3 -: Si(OH) 4 = 2:1 or 15:1, Fig. 4d). This is in agreement with 394 observations from modern El-Niño events, which show a shift in surface productivity from siliceous 395 (diatoms) to non-siliceous (dinoflagellates) phytoplankton (Sanchez et al., 2000). ...
The sedimentary stable nitrogen isotope compositions of bulk organic matter (δ¹⁵Nbulk) and silicon isotope composition of diatoms (δ³⁰SiBSi) both mainly reflect the degree of past nutrient utilization by primary producers. However, in ocean areas where anoxic and suboxic conditions prevail, the δ¹⁵Nbulk signal ultimately recorded within the sediments is also influenced by water column denitrification causing an increase in the subsurface δ¹⁵N signature of dissolved nitrate (δ¹⁵NO3−) upwelled to the surface. Such conditions are found in the oxygen minimum zone off Peru, where at present an increase in subsurface δ¹⁵NO3− from North to South along the shelf is observed due to ongoing denitrification within the pole-ward flowing subsurface waters, while the δ³⁰Si signature of silicic acid (δ³⁰Si(OH)4) at the same time remains unchanged.
Here, we present three new δ³⁰SiBSi records between 11° S and 15° S and compare these to previously published δ³⁰SiBSi and δ¹⁵Nbulk records from Peru covering the past 600 years. We present a new approach to calculate past subsurface δ¹⁵NO3− signatures based on the correlation of δ³⁰SiBSi and δ¹⁵Nbulk signatures at a latitudinal resolution for different time periods. Our results show source water δ¹⁵NO3− compositions during the last 200 years, the Current Warm Period (CWP) and during short-term arid events prior to that, which are close to modern values increasing southward from 7 to 10 ‰ (between 11° S and 15° S). In contrast, humid conditions during the Little Ice Age (LIA) reflect consistently low δ¹⁵NO3− values between 6 and 7.5‰. Furthermore, we are able to relate the short-term variability in both isotope compositions to changes in the ratio of nutrients (NO3− : Si(OH)4) taken up by different dominating phytoplankton groups (diatoms and non-siliceous phytoplankton) under the variable climatic conditions of the past 600 years.
... The Humboldt Current System (HCS) sustains high levels of biologi- cal productivity due to yearlong upwelling-favorable southeast trade winds, which induce the vertical advection of cold, nutrient-rich and oxygen-poor waters from relatively shallow depths (Strub, Combes, Shillington, & Pizarro, 2013;Strub & Mes ıas, 1998). The low-latitude of the HCS allows a strong upwelling circulation due to larger off- shore Ekman transport but also makes it very sensitive to equatorial oceanic perturbations, such as El Ni~ no Southern Oscillation (ENSO) (Colas, Capet, McWilliams, & Shchepetkin, 2008;Mogoll on & Calil, 2017;Montes, Schneider, Colas, Blanke, & Echevin, 2011;Sanchez, Calienes, & Zuta, 2000). This intrinsic variability makes the HCS resi- lient to natural climate variability ( Bakun et al., 2015). ...
It has been hypothesized that global warming will strengthen upwelling-favorable winds in the Northern Humboldt Current System (NHCS) as a consequence of the increase of the land-sea thermal gradient along the Peruvian coast. The effect of strengthened winds in this region is
assessed with the use of a coupled physical-biogeochemical model forced with projected and climatological winds. Strengthened winds induce an increase in primary production of 2% per latitudinal degree from 9.5°S to 5°S. In some important coastal upwelling sites primary production is reduced. This is due to a complex balance between food availability, nutrient use efficiency, as well as eddy and wind-driven factors. Mesoscale activity induces a net offshore transport of inorganic nutrients, thus reducing primary production in the coastal upwelling region. Wind mixing, in general disadvantageous for primary producers, leads to shorter residence times in the southern and central coastal zones. Overall, instead of a proportional enhancement in primary production due to increased winds, the NHCS becomes only 5% more productive (+5 mol C m−2 yr−1 ), 10% less limited by nutrients and 15% less efficient due to eddy-driven effects. It is found that regions with a initial strong nutrient limitation are more efficient in terms of nutrient assimilation which makes them more resilient in face of the acceleration of the upwelling circulation.
... During ENSO episodes, equatorial fluctuations in sea level and currents propagate along the Peruvian coast, which behaves as an extension of the equatorial waves guide (Clarke and van Gorder, 1994). Strong El Niño (EN) events, like the 1997-1998 eastern Pacific El Niño, affect circulation and water mass distribution, causing the deepening of the OMZ and the occurrence of large oxygenation events in the water column and over the sediments along the Chilean and Peruvian coast (Morales et al., 1999;Sánchez et al., 1999;Gutiérrez et al., 2008). In fact, Helly and Levin (2004) reported that during the 1997-1998 El Niño, about 61 % of the OMZ volume off Peru and northern Chile was reduced. ...
Over the last decades, the Humboldt Current upwelling ecosystem, particularly the northern component off the coast of Peru, has drawn the interest of the scientific community because of its unique characteristics: it is the upwelling system with the biggest catch productivity despite the fact it is embedded in a shallow and intense oxygen minimum zone (OMZ). It is also an area of intense nitrogen loss and anammox activity and experiences large interannual variability associated with the equatorial remote forcing. In this context, we examined the oceanographic and biogeochemical variability associated with the OMZ off central Peru from a monthly time series (1996–2011) recorded off the coast of Callao (12∘02′ S, 77∘29′ W). The data reveal a rich spectrum of variability in the OMZ that includes frequencies ranging from seasonal to interannual scales. Due to the efficient oceanic teleconnection off Peru, the observed variability is interpreted in the light of an estimate of the equatorial Kelvin wave contribution to sea level anomalies considering the peculiarities of its vertical structure (i.e., the first two baroclinic modes). The span of the data set allows us to contrast two OMZ regimes. The “strong” regime is associated with the strong 1997–1998 equatorial Pacific El Niño, during which the OMZ adjusted to Kelvin-wave-induced downwelling conditions that switched off the upwelling and drastically reduced nutrient availability. The “weak” regime corresponds to the post-2000 period associated with the occurrence of moderate central Pacific El Niño events and enhanced equatorial Kelvin wave activity, in which mean upwelling conditions are maintained. It is shown that the characteristics of the coupling between physics and biogeochemistry is distinct between the two regimes with the weak regime being associated with a larger explained variance in biogeochemical properties not linearly related to the ENSO oceanic teleconnection. The data also reveal a long-term trend from 1999 corresponding to a deepening of the oxygen-deficient waters and warming. The implications of our results for understanding the OMZ dynamics off Peru are discussed.
... Within the Southeast Pacific it is distributed from Panama to Chile (45°41'S) including Cocos, Malpelo and Galapagos Islands (Collette et al. 2011). Off Peru, the chub mackerel is mainly associated with the water mass denominated Subtropical Surface Waters (SSW) (Sanchez et al. 2000) usually forming large shoals especially beyond 160 nautical miles (Dioses 1995). This species is considered as an opportunistic omnivorous being the Peruvian anchovy, copepods and euphausiids their main prey (Alegre et al. 2015). ...
The chub mackerel Scomber japonicus supports an important fishery in the Southeast Pacific, however, its population genetics is currently unknown. In the present study, we examined the genetic structure, the gene flow and the historical demography of this species in the Northern Humboldt Current System. Samples were collected during summer of years 2013-2014 from three fishing points (Paita, Ventanilla and Ilo), covering 12 degrees of latitude along the coast of Peru. A 532 bp segment of the mitochondrial control region was sequenced in 72 individuals, which allowed us to detect a total of 29 polymorphic sites, 35 haplotypes, moderate-to-high levels of haplotype diversity (0.793 – 0.969) and very low levels of nucleotide diversity (0.004 – 0.008). Gene flow analysis showed high levels of connectivity among populations in the sam- pling areas. Analysis of molecular variance (ФST= 0.00868, P = 0.1837), population pairwise ФST comparisons and genetic differentiation tests
confirmed the lack of genetic structuring among the three localities. These analyses suggest that sampling sites analyzed can be considered as a single gene pool. Migratory behavior, the high dispersal potential of early stages and the lack of oceanographic barriers may explain its genetic homogeneity along the Peruvian sea. Historical demography was also examined. Neutrality tests, mismatch distribution and Bayesian skyline plot suggested a population expansion scenario that took place during the Late Pleistocene. This study provides novel information on population genetics of the chub mackerel in the Southeast Pacific.
... Upwelling can become more intense due to stronger coastal winds south of 5°S, but nutrient-rich waters are not transported to the surface and primary production decreases significantly (Barber and Chavez 1983). For instance, the oxygen minimum zone deepens around 200-250 m (Guillén et al. 1985;Sánchez et al. 2000;Graco et al. 2016) and primary production declines 50% (Ochoa et al. 1985;Rojas de Mendiola et al. 1985;Chávez et al. 1989). With climate change, the circulation along the coast is expected to be modified due to changes in surface winds and increased stratification. ...
The Peruvian portion of the Humboldt Current System is highly productive and variable. The effects of environmental variability off Peru on marine life have been documented for decades. Interannual variability such as El Niño events appears to be associated with changes in distribution, changes in body size, biomass and recruitment, and catches of several species of commercial importance. Further changes in abundance, distribution and phenology of marine species are expected to exacerbate with climate change, which poses an additional and major stressor to marine life in the region.
Peru comprises one of the most important fisheries in the world; in terms of aquaculture, the production of this country has increased considerably in recent years and has great potential for development. Due to its dependency on fish and associated economic activities, Peru was identified in previous studies as moderately to highly vulnerable to climate change. Indeed, Peruvian fish production is projected to decline over the next few decades in response to climate change. Therefore, this project aims to pinpoint the most important climate stressors in the marine ecosystems of Peru and to identify the species of commercial and ecological importance that are most sensitive to such climate stressors. In detail, the objectives of this project are: 1) Elaborate species profiles of fishery and aquaculture species of the Peruvian marine ecosystem; 2) Identify physical and chemical parameters associated with climate change that may have potential impacts on key Peruvian fishery and aquaculture species; 3) Implement an ecological risk assessment of the impacts of climate change on Peruvian fishery and aquaculture species; 4) Prioritize key Peruvian fishery and aquaculture species based on their sensitivity to climate change; 5) Identify crucial information and data gaps on the impacts of climate change on key Peruvian fishery and aquaculture species to pinpoint future research needs.
Scientists, managers and stakeholders may be benefited with the outcomes of this project by anticipating and adapting to the potential impacts of climate change on commercially important species, to minimise the risks and to maximise the opportunities associated with changes driven by climate change. The outcomes achieved in this study are listed below:
1. The species profiles were elaborated for most species; most information was available for the species in the area of interest. The sources of information were mainly reports and theses from IMARPE and other Peruvian institutions, as well as publications in peer-reviewed scientific journals.
2. Some physical and chemical parameters associated with climate change and that are likely to affect the Peruvian marine ecosystems were identified. For instance, temperature was identified as a key physical factor that may affect the life history characteristics, distribution patterns, and abundance of pelagic, demersal and invertebrate fishery species, as well as the performance of farmed species. The low oxygen concentration associated to warm waters is expected to negatively affect the abundance of the species evaluated. Not only active species may be the most affected via an increasing metabolic demand but also sessile species such as scallops. Ocean acidification will negatively affect species with calcareous structures, and also will have complex ramifications on highly active fishes and invertebrates; for instance, the blood-oxygen binding in most active squids is highly pH sensitive. The reduction of upwelling conditions associated to warm waters (e.g. during El Niño events) towards the coast of Peru may cause the change in distribution and abundance of several species, with expected impacts on commercial catches. Freshwater flow and the associated sediment transport may cause significant negative impacts on scallop beds, increasing mortality and reducing the production of this resource. Via changes in salinity, freshwater flow will also affect species that migrate towards the coast, or near rivers or estuaries to spawn or to use those habitats as nursery grounds. Sea level rise, increased frequency and intensity of extreme events, and harmful algal blooms or pathogens are expected to have significant impacts on aquaculture industries.
3. Ecological risk assessments of the impacts of climate change were successfully implemented on Peruvian fishery and aquaculture species.
4. Key Peruvian fishery and aquaculture species were ranked based on their relative sensitivity to climate change. The most sensitive fishery species were the corvina drum, the Peruvian hake, the catfish, the mote sculpin, the Peruvian rock seabass, and the black ark. The most at risk aquaculture industries were the marine farmed scallop and the kelp, and the land farmed rainbow trout.
5. Key knowledge gaps were identified and allowed prioritising future research.
... The Tripos species are slow-growing, found round the year [4][5][6][7][8] , and are known to be a model species within the dinoflagellates for biogeographic and global change studies 9 . In relation to temperature some of its forms are referred as excellent water mass indicators, North Atlantic 4,10 , Mediterranean Sea 11,12 , Pacific 13,14 , Arctic 15 and Indian Ocean 16 . Phytogeographical studies also showed close relationship of individual species with temperature, while some are fairly tolerant towards wide temperature range 8 . ...
Tripos, a species-rich ubiquitous thecate dinoflagellate, serves as an excellent biological indicator of the water mass in the oceans. The inter- and intra-annual variations in the surface-water distribution of Tripos along the shipping routes of Chennai (C)–Port Blair (P)–Kolkata (K) in the Bay of Bengal was evaluated from October 2006 to September 2011. The highest numbers were recorded during fall intermonsoon (October 2007) in the C–P transect, and southwest monsoon (July 2010) in the P–K transect. In the C–P transect high numbers of T. furca can be attributed to mesoscale eddies, whereas in the P–K transect, it can be attributed to riverine discharge. The results point that, Tripos persists throughout the year in the Bay of Bengal and tend to increase with the elevation of nutrients.
... The Tripos species are slow-growing, found round the year [4][5][6][7][8] , and are known to be a model species within the dinoflagellates for biogeographic and global change studies 9 . In relation to temperature some of its forms are referred as excellent water mass indicators, North Atlantic 4,10 , Mediterranean Sea 11,12 , Pacific 13,14 , Arctic 15 and Indian Ocean 16 . Phytogeographical studies also showed close relationship of individual species with temperature, while some are fairly tolerant towards wide temperature range 8 . ...
Tripos, a species-rich ubiquitous thecate dinoflagellate, serves as an excellent biological indicator of the water mass in the oceans. The inter- and intra-annual variations in the surface-water distribution of Tripos along the shipping routes of Chennai (C)–Port Blair (P)–Kolkata (K) in the Bay of Bengal was evaluated from October 2006 to September 2011. The highest numbers were recorded during fall intermonsoon (October 2007) in the C–P transect, and southwest monsoon (July 2010) in the P–K transect. In the C–P transect high numbers of T. furca can be attributed to mesoscale eddies, whereas in the P–K transect, it can be attributed to riverine discharge. The results point that, Tripos persists throughout the year in the Bay of Bengal and tend to increase with the elevation of nutrients.
... In the Pacific Ocean, the distribution patterns of dinoflagellates appear to reflect the development of El Niño events [21] as some species are indicators of different water masses affected by this phenomenon. One example is Neoceratium breve which is considered as an indicator of Equatorial Surface Waters [21,22]. ...
Among the planktonic dinoflagellates, the species-rich genus Neoceratium has particularly remarkable features that include its easily recognizable outline and large size. This ubiquitous genus shows consistent presence in all plankton samples and has been a model for numerous studies since the end of the 19th century. It has already been described as a good candidate to monitor water masses and describe ocean circulation. We argue that the sensitivity displayed by Neoceratium to water temperature also makes it relevant as an indicator of ocean warming. The advantages and interests of using Neoceratium species to monitor climate change on a large scale are reassessed in view of recent advances in understanding their biology and ecology.
... For example, in the Gulf of California, large declines in seabird breeding success and survival occurred during El Niño events, affecting seabird population sizes for several years afterwards. Similarly, in Peru, seabirds experienced near-complete breeding failures and an increase in adult mortality during strong El Niño years because prey cannot be located for chicks and adults (Sanchez et al. 2000). The Pacific Decadal Oscillation is a longer, multi-decadal process in the North Pacific Ocean, with cold or warm water regimes present for 10 or more years at a time Mantua 2000, Mantua et al. 2002). ...
This chapter discusses the diversity of seabird characteristics that are relevant in studying how they alter islands. It focuses on two primary seabird mechanisms: nutrient deposition and physical disturbance. It analyzes the seabird's body size, nearshore vs. pelagic feeding habits and trophic position, temporal and spatial migratory patterns vs. maintenance of permanent residency, and nesting strategies and density. It also introduces a conceptual framework that determines the roles of nutrient inputs and physical disturbance and uses them to evaluate the impacts of seabirds on soils, plants, and animal communities.
... Entre 10 °S y 20 °S, el núcleo de la ZMO (<0.2 mL.L -1 ) se encuentra entre 75 a 312 metros, mientras que las concentraciones de oxígeno disuelto menores a 0.5 mL.L -1 se encuentra entre 57 a 368 metros (Helly y Levin, 2004). Durante eventos extremos como El Niño 1997/98, el borde superior de la ZMO se profundizó hasta 250 metros (Sánchez et al., 2000), por lo que los sedimentos que están normalmente en el borde de la ZMO podrían oxigenarse temporalmente, a escalas interanuales, durante eventos El Niño. Por lo tanto se puede esperar que los testigos colectados en el borde de la ZMO serían más susceptibles a degradación por algún mecanismo que involucre una mayor oxigenación en comparación a testigos colectados en el núcleo de la ZMO. ...
The overall objective of this study is to provide the foundation to reconstruct the history of the populations of small pelagic fish species using the remains that are preserved in marine sediments in the oxygen minimum zone (OMZ) off Peru. This work is based on two box cores that were collected off Pisco (14 ºS), one at 300 meters near the center of the OMZ, and the other at 200m near the upper limit of the OMZ, for the purpose of characterizing the variability in deposition of the fish remains. Comparison of the two cores provides the means to determine whether there are differences in the quality of preservation of fish scales that can be linked to the depth of the cores within the OMZ along the upper slope. Fish scale counts in both cores show a dominance of anchovy (Engraulis ringens) relative to the abundance of scales from sardine (Sardinops sagax sagax), jack mackerel (Trachurus symmetricus murphyi) and pacific mackerel (Scomber japonicus). The fish scale numbers in both cores suggest a relatively lower local anchovy population density (due to lower productivity and/or changes in spatial distribution) persisting from the beginning of the series at the bottom of the two cores to ~1840 (55cm in both cores) and a significantly higher local density of anchovy after ~1880 (~41cm in the two cores). The intermediate period (~1840-1880) is characterized by the absence or very low numbers of anchovy scales (and vertebrae) and the presence of species associated with more oceanic and warmer water habitat. To determine whether the lower numbers of anchovy scales in the period before ~1840 were due only to lower local abundance of anchovy or whether the effects of preservation of the fish scales in the sediments were also a significant factor, several indices were examined as possible indicators of fish scale preservation: 1) fish scale/vertebrate ratio, 2) the degree of coverage of fungi on the fish debris and 3) an index of fish scale integrity (estimate of degree of scale breakdown). These indices indicate that the lower numbers of fish scales in the earliest period could be largely explained by degradation and is more intense in the box core from 200m that is subject to somewhat higher oxygen concentrations within the OMZ as well as to occasional events of more intense oxygenation due to variation of the upper limit of the OMZ. A preliminary estimate was made to correct for the effects of degradation on the series of fish scale counts. This analysis indicates that the period prior to ~1840 does represent lower local anchovy biomass, but the difference is not as significant as indicated by the raw fish scales numbers. The effect of degradation during the earliest period is estimated to result in a decrease of up to ~70-85% in the number of fish scales deposited in both of the box cores analyzed.
... However it varies on seasonal and interannual timescales, allowing for the intrusion of benthic fauna from the upper slope that recurrently causes sediment mixing (Gutierrez et al., 2008). During the strong El Niño event of 1997e98, the upper OMZ boundary deepened to 190 m causing a mild oxygenation of an otherwise anoxic upper slope (200e300 m) allowing the presence of benthic fauna (Sanchez et al., 2000;Levin et al., 2002). The ETSP-OMZ is supplied with oxygen-rich water from zonal tropical currents: near the equator, EUC, the SSCCs and the Southern Intermediate Countercurrents (SICC; Furue et al., 2007). ...
... Since 1982/83 the extraordinary ENSO occurred, the scientist's interest to its impacts on marine ecosystem rapid growth especially in Pacific Ocean. They conclude that climate variability was impact on community composition, species abundance and distribution, recruitment level, and tropics structure [Arntz and Rarazona, 1990;Lehodey et al., 1997;Kimura et al., 1997;Sanchez et al., 2000;Sugimoto et al., 2001;Gaol, et al., 2002]. ...
The investigation is aimed to clarify the influence of the El Niño Southern Oscillation (ENSO) and the Dipole Mode (DM) events to the spatio-temporal evolution of the sea surface temperature (SST) and Chlorophyll-a (Chl-a) as well as assessing of their impact to fish catchability. A time series of provincial monthly averaged of SST and Chl-a derived from satellite data, are used in this investigation. Sardinella lemuru (Lemuru)andtuna fish catch are obtained from the fishery statistic data report and the logbooks of ten fishing vessels operated in the south of Java seawaters. The SST indicated that the coolest period with maximum anomalies was observed during July-September 1997. Warmest period was during February-March 1998. It was occurred in Arafuru Sea and southeast off Lombok Strait (LS). The blooming of phytoplankton followed the coolest phase caused by upwelling at south of Java and southeast of Lombok Strait. The same condition was also observed on July-September 1999, but the scale and its quantity was different and smaller than on 1997. Monthly mean catch of Lemuru sharply increased during 1997-1998. The maximum of total catch and annual mean hook rate of tuna were highest during 1997 than 1998 and 1999. It seems have close correlation to the termocline layer in 1997, the depth of thermocline become shallower due to the DM-induced strong upwelling. Occurrence of thermal fronts around upwelling area might also have contributed to increase the fish catchability by providing suitable ambient temperature and feeding grounds for tuna.
... Since 1982/83 the extraordinary ENSO occurred, the scientist's interest to its impacts on marine ecosystem rapid growth especially in Pacific Ocean. They conclude that climate variability was impact on community composition, species abundance and distribution, recruitment level, and tropics structure [Arntz and Rarazona, 1990;Lehodey et al., 1997;Kimura et al., 1997;Sanchez et al., 2000;Sugimoto et al., 2001;Gaol, et al., 2002]. ...
The investigation is aimed to clarify the influence of the El Niño Southern Oscillation (ENSO) and the Dipole Mode (DM) events to the spatio-temporal evolution of the sea surface temperature (SST) and Chlorophyll-a (Chl-a) as well as assessing of their impact to fish catchability. A time series of provincial monthly averaged of SST and Chl-a derived from satellite data, are used in this investigation. Sardinella lemuru (Lemuru) and tuna fish catch are obtained from the fishery statistic data report and the logbooks of ten fishing vessels operated in the south of Java seawaters. The SST indicated that the coolest period with maximum anomalies was observed during July-September 1997. Warmest period was during February-March 1998. It was occurred in Arafuru Sea and southeast off Lombok Strait (LS). The blooming of phytoplankton followed the coolest phase caused by upwelling at south of Java and southeast of Lombok Strait. The same condition was also observed on July-September 1999, but the scale and its quantity was different and smaller than on 1997. Monthly mean catch of Lemuru sharply increased during 1997-1998. The maximum of total catch and annual mean hook rate of tuna were highest during 1997 than 1998 and 1999. It seems have close correlation to the termocline layer in 1997, the depth of thermocline become shallower due to the DM-induced strong upwelling. Occurrence of thermal fronts around upwelling area might also have contributed to increase the fish catchability by providing suitable ambient temperature and feeding grounds for tuna.
... Mereka menyimpulkan bahwa variabilitas iklim berpengaruh terhadap komposisi spesies, kelimpahan spesies dan distribusi, tingkat rekruitmen dan struktur tropik sumberdaya perikanan (Arntz, and Tarazona. 1990; Lehodey et al., 1997; Kimura et al, 1997; S nchez et al., 2000; Sugimoto et al., 2001). Perairan SHBT mempunyai sifat yang unik karena merupakan penghubung antara Lauan Hindia dan Lautan Pasifik dimana massa air dari Lautan Pasifik masuk ke Lautan Hindia melalui beberapa selat di Indonesia. ...
ABSTRAK El Nino Southern Ossillation (ENSO) dan Indian Ocean Dipole (IOD) mempengaruhi kondisi Samudera Hindia. Namun, masih sedikit informasi yang mengungkap dampaknya terhadap ikan tuna mata besar. Penelitian ini bertujuan untuk memahami variabilitas (spatio-temporal) karakteristik oseanografi di Samudra Hindia Bagian Timur (SHBT) dan menganalisis dampaknya terhadap tangkapan tuna mata besar. Pada studi ini dianalisis data deret waktu suhu permukaan laut (SPL), konsentrasi klorofil-a fitoplanton dan tinggi paras laut (TPL) dari multi sensor satelit dan data hidrografi dari basis data world ocean data center (WODC). Data deret waktu tuna mata besar diperoleh dari PT. Perikanan Samoedra Besar (PSB) Benoa, Bali. Hasil analisis menunjukkan terjadi variabilitas tahunan dan antar-tahun dari parameter-parameter oseanografi di SHBT. Variabilitas tahunan berhubungan dengan angin Monsoon sedangkan antar tahun akibat dari kejadian El Nino dan IOD. Pada saat Monsoon Tenggara terjadi upwelling yang menyebabkan, SPL dan TPL menurun sedangkan konsentrasi klorofil-a meningkat. Pada saat El Nino dan IOD positif, terjadi anomali negatif SPL dan TPL sedangkan konsentrasi klorofil-a fitoplankton meningkat tajam (anomali positif). Variabilitas parameter-parameter oseanografi berpengaruh secara signifikan terhadap laju tangkap ikan tuna mata besar. Pada saat Monsoon Tenggara, Hook Rate (HR) ikan tuna mata besar meningkat dan lokasi daerah penangkapan ikan lebih dekat ke pantai. Demikian juga halnya pada saat El Nino, HR ikan tuna meningkat secara tajam. Peningkatan HR tuna selama El Nino dan IOD positif disebabkan pendangkalan lapisan termoklin yang lebih karena induksi upwelling yang kuat sehingga mata pancing longline lebih banyak menjangkau fishing layer tuna mata besar. Proses upwelling yang lebih intensif pada saat El Nino dan IOD positif juga menjadi faktor penyebab kondisi lingkungan perairan sesuai sebagai feeding ground tuna mata besar. Kata kunci: El Nino, klorofil-a, iklim, Indian Ocean Dipole, Suhu, Tuna mata besar. 1. PENDAHULUAN 1.2 Latar Belakang Samudra Hindia bagian Timur (SHBT) menjadi daerah penangkapan ikan bukan saja bagi nelayan Indonesia tapi termasuk bagi nelayan asing. Keberlanjutan sumberdaya ikan di perairan ini ditopang oleh proses upwelling yang terjadi secara musiman sehingga perairan ini tetap kaya nutrienyang dimanfaatkan oleh fitoplankton pertumbuhannya. Sejak kejadian ENSO yang luar biasa tahun 1982/83, perhatian para peneliti meningkat akan pengaruhnya terhadap ekosistem laut khususnya di Lautan Pasifik. Mereka menyimpulkan bahwa variabilitas iklim berpengaruh terhadap komposisi spesies, kelimpahan spesies dan distribusi, tingkat rekruitmen dan struktur tropik sumberdaya perikanan (Arntz, and. Perairan SHBT mempunyai sifat yang unik karena merupakan penghubung antara Lauan Hindia dan Lautan Pasifik dimana massa air dari Lautan Pasifik masuk ke Lautan Hindia melalui beberapa selat di Indonesia. Dengan demikian proses yang terjadi di kedua lautan ini juga mempengaruhi variabilitas perairan di SHBT. Para peneliti sebelumnya telah mengungkapkan bahswa variabilitas massa air di SHBT dipengaruhi oleh sistem angin musson (Wyrtki, 1962), ENSO (Meyer, 1996; Susanto 2006) dan fenomena Indian Ocean
... The intensity and vertical extension of the oxygen minimum zone (OMZ) vary at seasonal to centennial timescales inducing recurrent sediment mixing by benthic fauna in sediments from the upper slope (Kim and Burnett, 1988;Levin et al., 2003;Gutierrez et al., 2008). During the strong El Niño event of 1997-98, the upper OMZ boundary (normally located at~40 m water depth) deepened to 190 m causing a mild oxygenation of an otherwise anoxic upper slope (200-300 m) allowing the presence of benthic fauna (Sanchez et al., 2000;Levin et al., 2002). Several cores retrieved off Callao (~12°S) showed bioturbated zones, suggesting the presence of benthic fauna within the upper centimeters of the sediment column, homogenizing the otherwise laminated sequence (Levin et al., 2003). ...
Plain Language Summary
The El Niño Southern Oscillation (ENSO) is a climate variability that is associated with changes in the climate state every 2–7 years. It occurs due to changes in the sea surface temperature (SST) in the Equatorial Pacific (EP) and causes shifts in the atmospheric circulation. Influences on weather, agriculture and thus the lives of many people worldwide makes understanding the role of the atmosphere important. In order to uncover the role of the atmosphere, we model the atmospheric transport with specialized computer code. We find that the air from the EP Ocean, where the largest anomalies in SSTs occur, is relatively warm when arriving over the Atlantic Ocean and releases its heat into the Ocean. Over South Central America, northern South America, and West Africa warmer and drier air is arriving, which leads to droughts associated with the ENSO. Over Mexico, North America's Gulf Coast and along the Gulf Stream wetter air is arriving, thus favoring precipitation during El Niño. Our results show that the transport of temperature and moisture anomalies from the EP via the atmosphere plays an important role for the weather conditions in several regions.
Under the impact of natural and anthropogenic climate variability, upwelling systems are known to change their properties leading to associated regime shifts in marine ecosystems. These often impact commercial fisheries and societies dependent on them. In a region where in situ hydrographic and biological marine data are scarce, this study uses a combination of remote sensing and ocean modelling to show how a stable seasonal upwelling off the Kenyan coast shifted into the territorial waters of neighboring Tanzania under the influence of the unique 1997/98 El Niño and positive Indian Ocean Dipole event. The formation of an anticyclonic gyre adjacent to the Kenyan/Tanzanian coast led to a reorganization of the surface currents and caused the southward migration of the Somali-Zanzibar confluence zone and is attributed to anomalous wind stress curl over the central Indian Ocean. This caused the lowest observed chlorophyll-a over the North Kenya banks (Kenya), while it reached its historical maximum off Dar Es Salaam (Tanzanian waters). We demonstrate that this situation is specific to the 1997/98 El Niño when compared with other the super El-Niño events of 1972,73, 1982-83 and 2015-16. Despite the lack of available fishery data in the region, the local ecosystem changes that the shift of this upwelling may have caused are discussed based on the literature. The likely negative impacts on local fish stocks in Kenya, affecting fishers' livelihoods and food security, and the temporary increase in pelagic fishery species' productivity in Tanzania are highlighted. Finally, we discuss how satellite observations may assist fisheries management bodies to anticipate low productivity periods, and mitigate their potentially negative economic impacts.
Introducción:
La alteración de la temperatura del ambiente pelágico puede repercutir en la variación poblacional de los consumidores tope como las aves marinas.
Objetivo:
Evaluar la respuesta poblacional de tres especies de piqueros en isla Gorgona (Pacífico colombiano) con respecto a la variabilidad local y regional de las condiciones de temperatura superficial del mar (TSM).
Métodos:
Se analizaron las tendencias mensuales de la abundancia de Sula leucogaster, Sula nebouxii y Sula variegata en relación a la variación de la TSM en el área de influencia de Gorgona, la región de San José en la costa del Perú y la región Niño 1+2.
Resultados:
La mayor correlación positiva se presentó entre S. nebouxii y S. variegata con la TSM de la región Niño 1+2, con un desfase de cuatro y cinco meses, respectivamente. Este desfase temporal posiblemente corresponde al tiempo que demora su migración entre la costa peruana y Gorgona. En contraste, la abundancia de S. leucogaster disminuyó al aumentar la TSM mensual de Gorgona.
Conclusiones:
Es probable que las tendencias descritas estén relacionadas con la disminución de la productividad y disponibilidad de presas asociadas con temperaturas más cálidas en estas áreas. Se sugiere que la TSM puede influir sobre las tendencias de abundancia de los tres piqueros, y su continuo monitoreo permitirá mejorar el conocimiento sobre la variación natural de estas poblaciones.
GUTIÉRREZ D, ARONÉS K, CHANG F , QUIPÚZCOA L, VILLANUEVA P. 2005. Impact of the stational and interannual oceanographic variation on the assemblages of microphyto-plankton, mesozooplankton, ichthyoplankton and macrozoobenthos in two coastal areas of northern Perú from 1994 to 2002. Bol Inst Mar Perú 22 (1-2): 1-60.- It was analyzed the oceanographic variation and the responses of microphytoplankton, mesozooplankton, ichthyoplancton and macrobenthos assemblages in the coastal areas (< 20 nm) off Paita (05°S) and off San José (06°45’S) from 1994 to 2002. The oceanographic variation was composed by different time-scales, which were modulated by the ENSO cycle, the poleward
propagation of coastal trapped waves (CTWs) resulting from Kelvin waves impacting
the coast near the Equator, and the seasonal intensification of coastal upwelling. The
sequence of the events El Niño (EN) 1997-98 and La Niña (LN) 1998-99 showed welldefined
characteristics in the surface physical conditions and in the vertical structure
of the water column.
Before the official onset of the EN 1997-98 event in May 1997, a Kelvin wave
impacted the northern coast, triggering positive temperature anomalies, a deepening
of the vertical structure and the presence of some biological indicators of warm water
masses in February and in April 1997. These conditions prevailed or were intensified
until the end of the event.
The LN 1998-99 event was characterized by the absence of warm water masses
near the coast and the dominance of cold coastal waters, the absence of Kelvin waves,
the shallow position of cold, oxygen-poor waters, and the dominance of planktonic
indicators of cold coastal waters. Seasonally, there was a tendency that more oxygenated subsurface conditions (a deeper oxycline) were present during autumm/winter, while less oxygenated subsurface conditions (hypoxic, a shallower oxycline) were developed during summer. This pattern does not agree with the upwelling seasonal regime, but coincides with the expected dynamics of the Southern Extension of the Cromwell Undercurrent at
these latitudes. In most of the cases there was a good fit of the tolerance ranges of some planktonic species to the dominant water masses in the surface layer: Cold Coastal Waters
(CCW), Surface Equatorial Waters (SEW) and Surface Subtropical Waters (SSW), validating
the usefulness of these species as biological indicators of water masses. There were determined the tolerance ranges of temperature and salinity from the phytoplankters
Protoperidinium obtusum (CCW), Ceratium breve (SEW) y Ceratium praelongum
(SSW), and from the zooplankters Centropages brachiatus (CCW), Eucalanus inermis
(CCW), Centropages furcatus (SEW), Mecynocera clausi (SSW), among others.
The indicators varied their distribution along the study period. CCW indicators
were found most of the times but not during the EN 1997-98 event; (a) in this pe-riod the
dinoflagellate Goniodoma polyedricum reached its highest frequency off San José and the
dinoflagellate Pyrocystis lunula peaked in frequency off Paita; (b) the abundance of the copepod Centropages furcatus (SEW) was increased off Paita, and was found off San José; (c) during the EN 1997-98 event the species composition of plankton was changed, increasing the total number of species due to the input of non-resident species; (d) Phytoplankton and zooplankton volumes tended to show a direct relationship under neutral ENSO conditions, but showed a negative relationship under El Niño and La Niña events; (e) the macrobenthic communities were impacted negatively in abundance and diversity by the EN 1997-98 event in both areas, contrasting with the response of the benthic macrofauna to EN off the central Peruvian coast. This behaviour could respond to the disturbance of the sedimentary environment off Paita due to the highly enhanced discharges of the Chira river. Off San José the impo-verishment of the macrobenthos may have resulted from the local reduction of primary production and of particulate flux to benthos. It is postulated that in this area the food limitation for benthos, due to erosive processes in the bottom, sets up a key difference of the dynamics of the benthic communities, compared to those off the central coast that inhabit areas of enhanced deposition and accumulation of particulate organic matter. Gammarid amphipods, specially those belonging to the family Ampeliscidae, showed the most consistent response to the environmental variability, since the populations were significantly reduced during the EN 1997-98 event in both coastal areas.
KEYWORDS: El Niño (EN), La Niña (LN), oceanographic variation 1994 - 2002,
ecological assemblages, microphytoplankton, mesozooplankton, ichthyoplankton,
macrozoobenthos, coastal areas of northern Perú.
La variabilidad interdecadal en el reclutamiento de los stocks de peces afecta la productividad de las pesquerías, y por ende a la estructura, dimensión y dinámica de la pesca. Aunque las causas de la variabilidad del reclutamiento están siendo estudiadas en todo el mundo, es importante analizar sus consecuencias en el manejo pesquero, sobre todo cuando el reclutamiento puede variar a escala decadal. En Chile, la merluza de cola (Macruronus magellanicus) es un recurso importante. El reclutamiento promedio de la merluza de cola cambió a un nivel bajo desde el 2000, lo que puede ser reflejo de fluctuaciones decadales. Actualmente, el estado de la merluza de cola es de sobrexplotación por lo que es necesario un plan de recuperación de la biomasa del stock desovante.
En esta tesis, un modelo operativo estructurado por edad y multi-flota permitió evaluar el desempeño del modelo de evaluación y la recuperación potencial del stock bajo variabilidad decadal del reclutamiento. Los escenario de reclutamiento para evaluar recuperación potencial fueron: a) nivel de reclutamiento bajo, modulado por la relación stock-recluta (SR); b) nivel de reclutamiento alto, modulado por un cambio de régimen en la relación SR; y c) variabilidad decadal del reclutamiento modulado por con cambios cíclicos con amplitud y fase constante. Para todos los casos, la variabilidad interanual del reclutamiento consideró errores distribuidos log-normal. La hipótesis de trabajo considera que el desempeño del modelo de evaluación de stock y la estrategia de explotación objetivo son robustos a la variabilidad interdecadal del reclutamiento de merluza de cola. Los resultados mostraron que el modelo de evaluación sobreestimó el reclutamiento durante la fase de reclutamientos bajos y subestimó el reclutamiento cuando cambió a niveles altos, ya sea cuando el reclutamiento fue cíclico o escalonado. En términos de precisión, el mejor desempeño del modelo de evaluación ocurrió cuando el reclutamiento fue cíclico y con errores de proceso y de observación. El MARE fue de 5,7% para la biomasa desovante, 6,15% para la biomasa total y de 0,25% para el reclutamiento. La peor precisión del modelo de evaluación ocurrió cuando hubo un cambio de régimen escalonado en el reclutamiento, con errores de proceso y de observación, y mediante la aplicación de la tasa de explotación objetivo. El MARE fue de 13,9% para el reclutamiento, 14,24% para la biomasa de reproductores y 15,96% para la biomasa total. Sin embargo, la serie de tiempo del error relativo medio mostró sesgos importante en la estimación del reclutamiento, que fueron canalizados a la biomasa del stock reproductor y biomasa total durante la transición en que el reclutamiento cambia de un nivel bajo a otro alto.
Para el caso del análisis de la recuperación potencial, cuando la gestión pasa por alto el cambio de reclutamiento y la población se mantiene en el nivel de reclutamiento bajo, el stock no fue capaz de recuperarse bajo la tasa de explotación objetivo. Sin embargo, cuando se simuló un cambio en el reclutamiento de un nivel bajo a otro alto dentro de 10 años, el stock mostró una probabilidad de recuperación mayor a 50% después de 2035. Debido a que la recuperación depende de un cambio en el reclutamiento, la recuperación es incierta y se sugiere ajustar la tasa de explotación objetivo durante el régimen actual de reclutamientos bajos de la merluza de cola. Además, es recomendable incorporar un índice de reclutamiento para el modelo de evaluación con el objetivo de rastrear con menos sesgo los cambios en el reclutamiento. En cuanto a la recuperación, es aconsejable diseñar un plan de recuperación efectivo para el stock de la merluza de cola.
In this research a combination of univariate index, descriptive analysis and multivariate techniques were carried out in order to describe the icthyoplankton taxonomic composition, community structure, spatial pattern of distribution in the coastal region of Colombia Pacific (Influence zone of the Colombian Current), considering simultaneously the grade with the environmental factors temperature, salinity and chlorophyll-a during the terminal phase of ENSO 2006-2007. 543 fish larvae were collected, belonging to 87 species of 37 families. The most abundant families were Myctophidae (26%) and Bregmacerotidae (17%). The spatial distribution of icthyoplankton and abiotic parameter demonstrate a high biotic and abiotic homogeneity in the study zone. However, the results of this research suggest that El Niño 2006-2007 drastically affect the icthyoplankton structure and abundance in the coastal zone of Colombian Pacific ocean. Furthermore, confirm that the Colombia Current is the main agent for the icthyoplankton distribution in this region.
This is a short communication about the "El Niño modeling" using a variational finite element model. Novel features: a) Only regional forcings were used to get the time dependent solutions. b) A particular feature: The observed net incident radiation (a forcing function of the model) is strongly related to the time variation of SST in the study region. c) The integrated SST during the El Niño periods are according to the observed SST in the region. d)The solutions show that the regional forcings develop the main part of the ocean dynamics during the events..
Fish population and fisheries fluctuations are closely linked to climate dynamics through environmental variability that determines the distribution, migration and abundance of fish. Fishery science were largely focused on the great northern hemisphere fisheries, which some of them fluctuate at decadal time scales and show patterns of synchrony with low frequency signals, as reflected by climatic indices such as the North Atlantic Oscillation (NAO). However, there is scarce information about these patterns at lower latitudes like NW African coast, in spite of this area supports large international fisheries. The aim of this work was to analyze how climate variability described by NAO and the physical environment influences the
productivity of European hake abundance, growth and recruitment variability. The European hake is widely distributed in the North Atlantic and their southern distribution limit is located in NW Africa. Historically it has been carried out an important multinational fishery in this area. In order to understand why it is important to test the climatic hypothesis over European hake stock, I presented the background elements in three main discussion lines. In Chapter 1, I compared the biology and population dynamics between European hake of NW Africa and populations from North Atlantic and Mediterranean Sea. In Chapter 2, it is described and analyzed the structure and evolution of European hake fisheries in NW Africa, focused on unexplained variability of stock assessment procedures carried out until now. In Chapter 3, the main climatic and environmental features of NW African coast are described, emphasizing the potential deterministic influence that variability of these features might exert on the biology, population dynamics and fisheries of
European hake in this area. In Chapter 4, catch‐based abundance indices of Moroccan and Spanish fisheries were used as the dependent variables in correlation analysis with NAO index. Time series analysis techniques were applied to ICOADS data and satellite data of wind stress and phytoplankton biomass as upwelling proxies to assess their dependence with NAO index. It was found a positive relationship between the NAO and hake abundance. NAO explained 35‐45% variability of juveniles with 1‐year lag and 45‐
60% of small and large adults with 2‐3‐years lag. The NAO index is a proper tool to trace the annual growth of European hake, at least during the first three years of life. Based on this, it is suggested that the growth rate is greater than previous calculus in the area, and it supports the fast growing hypothesis proposed for North Atlantic and Western Mediterranean. The wind stress explained 83% of phytoplankton biomass variability and both of them were positively correlated with NAO index (41‐58% explained variability respectively). The hake abundance was positively related..
ish scales accumulating in marine laminated sediments can provide a record of population variability of small pelagic fishes. Although some studies have noted signs of scale degradation that could affect estimates of population variability, there are presently no well- developed means to evaluate degradation. We developed several indices as indicators of fish scale preservation in two box-cores that we collected off Pisco (14uS), one at 301 m near the center of the oxygen minimum zone (OMZ), and the other at 201 m near the upper limit of the OMZ. These indices include (1) an index of fish scale integrity (estimate of scale wholeness relative to fragmentation), (2) the fungi-free area of fish scales and vertebrae, (3) the ratio of fish scales to vertebrae (as well as fish scales to vertebrae and bones), and (4) the ratio of whole scales to fragments. We address whether lower numbers of anchovy scales occurring in association with reduced total organic carbon fluxes and higher bottom-water oxygen concentrations are due entirely to lower abundances of anchovy or whether differential preservation of the fish scales in the sediments plays an important role in reduced scale abundances. Comparison of temporal sequences between the two cores provides the means to assess whether there are differences in the preservation of fish scales. The combined indices indicate that the lower numbers of fish scales in the earliest period have been affected by degradation, and to a greater degree in the box-core from 201 meters, which can be subject to higher oxygen concentrations. On the other hand, decadal-scale variations in fish scale abundance within the period of better preservation are unlikely to be caused by degradation. We discuss the utility and drawbacks of different indices of preservation for reconstructing past changes in fish population sizes with fluxes of fish debris and also briefly discuss the utility of these indices to other paleobiological systems.
A quantitative study of metazoan meiofauna was carried out on bathyal sediments (305, 562, 830 and 1210m) along a transect within and beneath the oxygen minimum zone (OMZ) in the southeastern Pacific off Callao, Peru (12°S). Meiobenthos densities ranged from 1517 (upper slope, middle of OMZ) to 440–548ind. 10cm−2 (lower slope stations, beneath the OMZ). Nematodes were the numerically dominant meiofaunal taxon at every station, followed by copepods and nauplii. Increasing bottom-water oxygen concentration and decreasing organic matter availability downslope were correlated with observed changes in meiofaunal abundance. The 300-m site, located in the middle of the OMZ, differed significantly in meiofaunal abundance, dominance, and in vertical distribution pattern from the deeper sites. At 305m, nematodes amounted to over 99% of total meiofauna; about 70% of nematodes were found in the 2–5cm interval. At the deeper sites, about 50% were restricted to the top 1cm. The importance of copepods and nauplii increased consistently with depth, reaching ∼12% of the total meiofauna at the deepest site. The observation of high nematode abundances at oxygen concentrations
The origin of the Tropical Oceans-Global Atmosphere (TOGA) Program was closely related to the response of global atmospheric circulation to sea surface temperature variations in the tropical Pacific Ocean, which is evident by the El Nino phenomenon. During the two decades before the 1985 start of TOGA, advancements in scientific understanding of the tropical ocean and global atmosphere and advancements in technology provided strong foundations for TOGA. By the early 1980`s, research had demonstrated a strong linkage between tropical SST variations and global atmospheric circulation, and discussions of an international ocean-atmosphere program had begun. Probably the single most important event leading to the creation of TOGA was the unannounced arrival in 1982 of the largest El Nino in a century. 92 refs., 1 fig.
Ocean /atmosphere perturbations that generate large-scale thermal anomalies in the Pacific are natural processes that cause significant variability in living resources. Analysis of the 1982-83 El Niño indicates that depression of the nutricline set in motion a decrease in productivity that eventually affected survival and reproduction at higher trophic levels. This impact, together with large-scale southward redistributions, accounted for most of the observed changes in the abundance of living resources.
The origin of the Tropical Oceans-Global Atmosphere (TOGA) Program was closely related to the response of global atmospheric circulation to sea surface temperature variations in the tropical Pacific Ocean, which is evident by the El Niño phenomenon. During the two decades before the 1985 start of TOGA, advancements in scientific understanding of the tropical ocean and global atmosphere and advancements in technology provided strong foundations for TOGA. By the early 1980s, research had demonstrated a strong linkage between tropical SST variations and global atmospheric circulation, and discussions of an international ocean-atmosphere program had begun. Probably the single most important event leading to the creation of TOGA was the unannounced arrival in 1982 of the largest El Niño in a century.