Equatorial Front Research Articles

Octocoral Distribution Patterns at the Equatorial Front (Tropical Eastern Pacific): Muricea and Leptogorgia

The Equatorial Front, in the southern part of the Tropical Eastern Pacific (TEP) region, has been characterized as a hotspot of functional biodiversity due to the mixing of warm and cold waters. Nevertheless, the biogeographic patterns for some organisms, such as octocorals, remain unknown in some coastal regions. Therefore, we aimed to assess the distribution of two common octocoral genera in this area, Muricea and Leptogorgia, including 14 species based on museum specimen records, along the mainland coast of Ecuador. Statistical analyses were performed on the environmental and geographical patterns (Sea Surface Temperature (SST), bathymetry, chlorophyll (CHL-a), and Photosynthetic Active Radiation (PAR)) that influence the Equatorial Front, which is subdivided into five biogeographic regions. Our results showed two hotspots of octocoral biodiversity. The SST was found to be the main environmental factor related to octocoral distribution along the Equatorial Front. Finally, the highest abundance of Muricea over Leptogorgia suggests the former species’ higher resilience to thermal fluctuations. We discuss the possible role of substrates at suitable depths, active photosynthetic radiation, and temperature in the occurrence of octocorals in the two hotspots.

Distribución espacial de diversidad y abundancia de copépodos planctónicos en el Pacifico ecuatoriano durante octubre del 2017

The spatial distribution, abundance and diversity of pelagic copepods and their relationship with hydrographic variables was studied at 19 stations in the Ecuadorian Pacific in October 2017. Collections were made by surface trawling, with a standard net of 30 cm mouth diameter and 220 ? mesh size. Sixty-three species of copepods were identified, with abundance ranging from 173 org.m-3 to 2246 org.m-3 and diversity ranging from 2.13 to 5.40 bit.org-1. Generally, copepod diversity and abundance were higher near the mainland and the Galapagos Islands. According to the ACC, the variable that most influenced distribution, abundance and diversity was the SST, an environmental parameter that explains the dynamics of the copepod community. In general, the distribution, diversity and abundance of copepods was largely related to the development of the equatorial front displaced south of the coast of Ecuador and to upwelling processes controlled by coastal and oceanic currents. Most of the identified species are common in tropical and subtropical water masses of neritic and oceanic environment.

Environmental forcing on zooplankton distribution in the coastal waters of the Galápagos Islands: spatial and seasonal patterns in the copepod community structure

The oceanographic setting of the Galápagos Archipelago results in a spatially diverse marine environment suitable for a variety of species with different climatic requirements. The goal of this study is to demonstrate that the community of zooplankton in the Galápagos is highly structured by regional differences in productivity patterns and advective sources. Results are mostly based on biodiversity patterns of the copepod community collected over the Galápagos shelf between 2004 and 2006. Two contrasting marine environments were observed: a nutrient-rich upwelling system with a shallow mixed layer and a diatom-dominated phytoplankton community in the west, and a non-upwelling system with a deeper mixed layer, lower surface nutrient concentrations, and a phytoplankton community dominated by small cells in the east. These conditions drive spatial structuring of zooplankton that varies seasonally, with 3 distinct copepod communities separated geographically in western, central, and southeastern regions. The western upwelling region has a high-abundance and low-diversity community, whereas the non-upwelling eastern region has a lower-abundance and higher-diversity community. The eastern community is further differentiated into central and southeastern regions, the former with tropical species advected from the north, the latter with temperate species advected from the south. During the warm season, when the equatorial front moves south, species typical of the central region spread southwest across the archipelago. This is the first taxonomically comprehensive list of copepod species for the Galápagos Islands. A total of 164 copepod species are identified, including 22 species previously unreported from the Eastern Tropical Pacific.

Variabilidad de la clorofila y su relación con el Frente Ecuatorial, Islas Galápagos durante los años 2014 al 2016

A total of 20 oceanographic stations were analyzed in the Ecuatorian sea during the years 2014 to 2016. Chlorophyll a distribution maps were elaborated, and its relationship with physical and chemical parameters was evaluated.  Physical oceanographic conditions favored the presence of the Equatorial Front and the equatorial upwelling to the west of the Galapagos Islands. The development of the El Niño 2015-2016 event, did not follow a defined pattern, but presented particular characteristics for each region of the Southern Pacific Ocean. In Ecuador it was observed that primary productivity increased considerably during the Cruise CO-1-2016 Cruise, with the presence of upwelling with an increase in chlorophyll, high cells concentrations an increase in relative abundance.

The Equatorial Current System West of the Galápagos Islands during the 2014–16 El Niño as Observed by Underwater Gliders

AbstractThe strong El Niño of 2014–16 was observed west of the Galápagos Islands through sustained deployment of underwater gliders. Three years of observations began in October 2013 and ended in October 2016, with observations at longitudes 93° and 95°W between latitudes 2°N and 2°S. In total, there were over 3000 glider-days of data, covering over 50 000 km with over 12 000 profiles. Coverage was superior closer to the Galápagos on 93°W, where gliders were equipped with sensors to measure velocity as well as temperature, salinity, and pressure. The repeated glider transects are analyzed to produce highly resolved mean sections and maps of observed variables as functions of time, latitude, and depth. The mean sections reveal the structure of the Equatorial Undercurrent (EUC), the South Equatorial Current, and the equatorial front. The mean fields are used to calculate potential vorticity Q and Richardson number Ri. Gradients in the mean are strong enough to make the sign of Q opposite to that of planetary vorticity and to have Ri near unity, suggestive of mixing. Temporal variability is dominated by the 2014–16 El Niño, with the arrival of depressed isopycnals documented in 2014 and 2015. Increases in eastward velocity advect anomalously salty water and are uncorrelated with warm temperatures and deep isopycnals. Thus, vertical advection is important to changes in heat, and horizontal advection is relevant to changes in salt. Implications of this work include possibilities for future research, model assessment and improvement, and sustained observations across the equatorial Pacific.

Spatio-temporal variability of the equatorial front in the eastern tropical Pacific from remote sensing salinity data (2010–2015)

In the eastern Pacific, the Equatorial Front (EF) separates the relatively cold and salty Equatorial Surface Water to the South from the relatively warm and fresh Surface Tropical Water to the North. Although previous studies have succinctly described the main EF characteristics, little is known about its spatial pattern and temporal variability beyond seasonal scale. In this study, we used 5 years of remote-sensing sea surface salinity (SSS) data, acquired by SMOS in a synoptic and continuous manner, to describe the spatio-temporal variability of the haline EF (HEF). After validating the SSS satellite dataset with concomitant in situ data, we developed an algorithm based on maximum SSS gradients to automatically identify the HEF position on every SMOS SSS map. This algorithm applied to the 4-day resolution SMOS SSS product, allows us to investigate the spatio-temporal variability of the HEF between 2010 and 2015. Seasonally, west of the Galapagos Islands, the HEF is centered at ~2°N and shows relatively weak meridional displacements. In contrast, east of the Galapagos Archipelago, the HEF varies on average between ~4°S in spring and ~2°N in autumn. At intraseasonal scales, the HEF shows meridional fluctuations of ±1.25° around its average position. These intraseasonal fluctuations are partly related to Kelvin Waves, which was more noticeable since 2014. Over the 5-year studied period, the HEF position showed a northward trend of 0.3–0.4 latitudinal degrees per year between 2010 and 2015. However, the relatively short time series does not permit to investigate whether this low-frequency trend is due to long-term variability or interdecadal fluctuations.

Satellite Tracking and Site Fidelity of Short Ocean Sunfish, Mola ramsayi, in the Galapagos Islands

Ocean sunfishes, with their peculiar morphology, large size, and surface habits, are valuable assets in ecotourism destinations worldwide. This study investigates site fidelity and long-range movements of short ocean sunfish, Mola ramsayi (Giglioli 1883), at Punta Vicente Roca (PVR) off Isabela Island in the Galapagos Islands. Five individuals were tracked between 32 and 733 days using ultrasonic receivers and transmitters. Two of the 5 were also tracked with towed pop-off satellite tags. One travelled to the equatorial front covering 2700 km in 53 days, with dive depths in the upper 360 m at temperatures between 9.2°C and 22°C. During its westward travel, dives extended to 1112 m (the deepest depth yet recorded for Molidae) into temperatures ranging between 4.5°C and 23.2°C. The remaining four individuals demonstrated site fidelity to PVR and were detected at the site between 128–1361 times for a total of 3557 reports. Forty-eight percent of the reports occurred during daytime hours and 52% after dark. Presumed cleaning session durations had a median of 15 minutes and a maximum of nearly 100 minutes. No other ultrasonic arrays around Galapagos or in the Eastern Pacific regional network recorded the presence of tagged individuals. These data are combined with tourist vessel sightings and submersible observations to confirm Punta Vicente Roca as an important sunfish hotspot.

Spatial and temporal variability of central Indian Ocean salinity fronts observed by SMOS

Soil Moisture and Ocean Salinity (SMOS) Sea Surface Salinity (SSS) measurements, in addition to other data, are used to study the occurrence of salinity fronts in the poorly sampled Indian Ocean, which exhibits unique seasonal wind and current reversals. The strength and extent of salinity fronts are analyzed to understand their variabilities. Salinity fronts computed from SMOS compare favorably with those computed from Argo floats data, with SMOS showing higher magnitudes and more detailed structure of the fronts than Argo. Strong salinity fronts are observed along the equatorial region, with meridional migration of the fronts following the migration of the Intertropical Convergence Zone (ITCZ) and meridional ocean currents. Linked with these fronts are less saline subsurface waters that are sustained by the ITCZ-influenced precipitation and warm near-surface layer. During the 2010 negative Indian Ocean Dipole event, the equatorial front was influenced more by the increased SSS along the equator rather than precipitation. Additional factors, such as advective processes, aid the dynamics of fronts in the tropical Indian Ocean. Zonal currents advect less saline waters from the eastern Indian Ocean into the central Indian Ocean. Additionally the Indonesian Throughflow transports less saline waters to the region south of the equator, which eventually influence SSS front dynamics.

RECENT PLANKTONIC FORAMINIFERA FROM DEEP-SEA SEDIMENTS FROM THE EASTERN EQUATORIAL PACIFIC: PROXIES OF THE EQUATORIAL FRONT IN THE LATE QUATERNARY

Planktonic foraminifera recovered from 25 deep-sea sediment samples (core-lops) Irom the eastern Equatorial Pacific were analyzed tor thoir geographic distribution and possible environmental controls. Samples colloctod doopor than tho carbonato lysoclino (-2800 m) show significant signs of dissolution, - when compared to sediment-trap samples resulting in the increase of the solutionresistant species Neogloboquadrlna duterlrei. NeogOboquadnna pachyderma and Gioborotaha Cufrata and the reduction of tho soíuüon-suscoptiblo spocios Globigonmta glutmata. Globigennotdes ruber and Gtobigohnoidos saccuMor. Threo bioprovincos woro rocognizod by cluster analysis: (1) bioprovince I that occurs on tho Cocos Ridgo whore G. cultrata and N. pachyderma are dominant. (2) bioprovince II that occurs on the Carnegie Ridge where N. duterlrei, N. pachyderma and Globorolatia intlata aro dominant, and (3) bioprovince III that occurs in the Panama Basin whore G. saccuhtor and G. ruber aro dominant. Bioprovinces I and II reflect a shallow thormocllno inducod by upwelhng. although AOU, NO , and PO, and SiO, are significantly higher in tho lattor rogion. B-oprovinco III reflects a deeprrvxod layor and low nutriont contonts. Possiblo proxies ol tho Equatorial Front in the past are: (1) the Shannon diversity indox. ovonness and the number ot species that show a latitudinal break at -1.5*S and. (2J the G. cultrata / G. dutertrei ratio that decreases southward

Sea surface and subsurface circulation dynamics off equatorial Peru during the last ~17 kyr

AbstractThe complex deglacial to Holocene oceanographic development in the Gulf of Guayaquil (Eastern Equatorial Pacific) is reconstructed for sea surface and subsurface ocean levels from (isotope) geochemical proxies based on marine sediment cores. At sea surface, southern sourced Cold Coastal Water and tropical Equatorial Surface Water/Tropical Surface Water are intimately related. In particular since ~10 ka, independent sea surface temperature proxies capturing different seasons emphasize the growing seasonal contrast in the Gulf of Guayaquil, which is in contrast to ocean areas further offshore. Cold Coastal Water became rapidly present in the Gulf of Guayaquil during the austral winter season in line with the strengthening of the Southeast Trades, while coastal upwelling off Peru gradually intensified and expanded northward in response to a seasonally changing atmospheric circulation pattern affecting the core locations intensively since 4 ka BP. Equatorial Surface Water, instead, was displaced and Tropical Surface Water moved northward together with the Equatorial Front. At subsurface, the presence of Equatorial Under Current‐sourced Equatorial Subsurface Water was continuously growing, prominently since ~10–8 ka B.P. During Heinrich Stadial 1 and large parts of the Bølling/Allerød, and similarly during short Holocene time intervals at ~5.1–4 ka B.P. and ~1.5–0.5 ka B.P., the admixture of Equatorial Subsurface Water was reduced in response to both short‐term weakening of Equatorial Under Current strength from the northwest and emplacement by tropical Equatorial Surface Water, considerably warming the uppermost ocean layers.

Palynological characterization and genetic divergence between accessions of chilli and sweet peppers

This study characterised pollen grains morphologically and studied the genetic divergence between accessions based on morphopollinic characters. Seven accessions, including domesticated, semi-domesticated and wild species of Capsicum (C. annuum var. annuum, C. chinense, C. baccatum var. pendulum, C. frutescens, Capsicum annuum var. glabriusculum, C. baccatum var. baccatum and C. parvifolium), were cultivated in a greenhouse and their pollen grains collected and fixed during flowering. The pollen grains were acetolysed and described based on 13 pollinic characteristics (polar and equatorial axes, in an equatorial front view; ratio between polar axis and equatorial axis; equatorial axis in a polar view; thicknesses of the exine, sexine and nexine; apocolpus side; polar area index; length and diameter of the pore and colpus). The genetic divergence analysis between the accessions was based on the standardised average Euclidean distance, and the grouping analysis was based on Ward's method. PCA (principal component analysis) is another multivariate method that was used. Based on Ward's method and PCA, it was possible to group the accessions into two groups, and the groups formed correlated with the classification of the gene pool complexes already described for the genus. According to this classification, the Capsicum genus comprises three major groups: C. annuum, C. chinense and C. frutescens form the annuum complex; C. baccatum and C. pratermissum form the baccatum complex; and C. eximium, C. cardenasii and C. pubescens form the pubescens complex. The variable width of the pores was the most discriminating in this morphopollinic study of Capsicum spp.

Near collapse of the meridional SST gradient in the eastern equatorial Pacific during Heinrich Stadial 1

[1] Sea surface temperatures (SST) and inorganic continental input over the last 25,000 years (25 ka) are reconstructed in the far eastern equatorial Pacific (EEP) based on three cores stretching from the equatorial front (~0.01°N, ME0005-24JC) into the cold tongue region (~3.6°S; TR163-31P and V19-30). We revisit previously published alkenone-derived SST records for these sites and present a revised chronology for V19-30. Inorganic continental input is quantified at all three sites based on 230Th-normalized fluxes of the long-lived continental isotope thorium-232 and interpreted to be largely dust. Our data show a very weak meridional (cross-equatorial) SST gradient during Heinrich Stadial 1 (HS1, 18–15 ka B.P.) and high dust input along with peak export production at and north of the equator. These findings are corroborated by an Earth system model experiment for HS1 that simulates intensified northeasterly trade winds in the EEP, stronger equatorial upwelling, and surface cooling. Furthermore, the related southward shift of the Intertropical Convergence Zone (ITCZ) during HS1 is also indicative of drier conditions in the typical source regions for dust.

Thermohaline intrusions in the thermocline of the western tropical Pacific Ocean

The existing high-resolution hydrographic data in the western tropical Pacific Ocean are used to explore the spatial distribution and primary characteristics of thermohaline intrusions in the thermocline. Statistics show that the vertical scales of intrusions are 20-40 m in the upper thermocline (22.0-26.0 sigma(0)) and 40-80 m in the lower thermocline (26.0-27.2 sigma(0)). In the upper thermocline, the most intensive intrusions exist at the equatorial front (EF) where north/south Pacific water masses converge, and the westward spreading of the north Pacific tropical water (NPTW) in the Philippines Sea also produces patches of intrusions surrounding its high-salinity tongue. In the lower thermocline, intrusions are also strong at the tropical front (TF) which is the boundary between the north Pacific subtropical/tropical waters. At the bottom of the thermocline (at about 27.0 sigma(0)), intrusions mainly exist near the western boundary, which are produced by intermediate water convergence through the advection of subthermocline western boundary flows. Most strikingly a "C"-shape distribution of intrusions at around 26.4 sigma(0) is revealed, covering the vicinity of the EF, the TF, and the Mindanao Current (MC), i.e., the western boundary pathway of the north Pacific subtropical cell (STC). Synoptic section analysis reveals that intrusions are more prominent on the warm/salty flank of the fronts, implying more cross-front tongues of cold/fresh water. Among the intrusions, those at the EF are of best lateral coherence which implies a unique driving mechanism involving near-inertial velocity perturbations near the equator.

Les avancées d'AMMA sur les interactions océan-atmosphère

Dédiée aux sciences de l'atmosphère, au climat et à d'autres domaines connexes, tels que l'océanographie ou la glaciologie, La Météorologie, révisée par des pairs et publiée en français, s'adresse aux professionnels de la météo et du climat, aux enseignants, aux étudiants, aux amateurs et aux utilisateurs. La Météorologie a succédé en 1925 à l'Annuaire de la Société météorologique de France (1852-1924) qui avait lui-même succédé à l'Annuaire météorologique de la France (1849-1851).

Epipelagic copepod distributions in the eastern equatorial Pacific during the weak La Niña event of 2001

We determined the distribution and abundance of pelagic copepods in the eastern equatorial Pacific between the coast of Ecuador and the Galapagos Islands under oceanographic conditions associated with the weak La Nina event of 2001. In September-October 2001, negative anomalies of sea surface temperature from this event still remained in the eastern equatorial Pacific, mainly between Ecuador and the Galapagos Islands. The event allowed the incursion of the Humboldt Current farther north and of the Equatorial Undercurrent into the study area, favouring a strong Equatorial Front and upwelling processes. There was evidence of mesoscale eddies in the study area and of the presence of the South Equatorial Current going westward at about 1°N. We identified 107 copepod species and analyzed the distribution of the 10 most abundant ones: Oncaea venusta, Subeucalanus pileatus, S. crassus, S. subtenuis, Paraeucalanus attenuatus, Pleuromamma borealis, Scolecithrix danae, Clausocalanus farrani, Temora discaudata and Calanus chilensis . Copepod distribution and abundance exhibited marked latitudinal differences related to the oceanographic conditions; abundance was highest to the southeast of the Galapagos Islands. Oncaea venusta, Pleuromamma borealis, Calanus chilensis , and Subeucalanus subtenuis were the species that best defined the Equatorial Front and the upwelling process.

Tracking the equatorial front in the eastern equatorial Pacific Ocean by the isotopic and faunal composition of planktonic foraminifera

Abstract Core-top samples from the eastern tropical Pacific (10°N to 20°S) were used to test whether the ratio between Globorotalia menardii cultrata and Neogloboquadrina dutertrei abundance (Rc/d) and the oxygen isotope composition (δ18O) of planktonic foraminifera can be used as proxies for the latitudinal position of the Equatorial Front. Specifically, this study compares the δ18O values of eight species of planktonic foraminifera (Globigerinoides ruber sensu stricto (ss) and sensu lato (sl), Globigerinoides sacculifer, Globigerinoides triloba, Pulleniatina obliquiloculata, Neogloboquadrina dutertrei, Globorotalia menardii menardii, Globorotalia menardii cultrata and Globorotalia tumida) with the seasonal hydrography of the region, and evaluates the application of each species or combination of species for paleoceanographic reconstructions. The results are consistent with sea surface temperature and water column stratification patterns. We found that in samples north of 1°N, the Rc/d values tend to be higher and δ18O values of G. ruber, G. sacculifer, G. triloba, P. obliquiloculata, N. dutertrei, and G. menardii cultrata tend to be lower than those from samples located south of 1°N. We suggest that the combined use of Rc/d and the δ18O difference between G. ruber and G. tumida or between P. obliquiloculata and G. tumida are the most suitable tools for reconstructing changes in the latitudinal position of the Equatorial Front and changes in the thermal stratification of the upper water column in the eastern tropical Pacific.

More humid interglacials in Ecuador during the past 500 kyr linked to latitudinal shifts of the equatorial front and the Intertropical Convergence Zone in the eastern tropical Pacific

[1] Studying past changes in the eastern equatorial Pacific Ocean dynamics and their impact on precipitation on land gives us insight into how the Intertropical Convergence Zone (ITCZ) movements and the El Nino‐Southern Oscillation modulate regional and global climate. In this study we present a multiproxy record of terrigenous input from marine sediments collected off the Ecuadorian coast spanning the last 500 kyr. In parallel we estimate sea surface temperatures (SST) derived from alkenone paleothermometry for the sediments off the Ecuadorian coast and complement them with alkenone‐based SST data from the Panama Basin to the north in order to investigate SST gradients across the equatorial front. Near the equator, today’s river runoff is tightly linked to SST, reaching its maximum either during the austral summer when the ITCZ migrates southward or during El Nino events. Our multiproxy reconstruction of riverine runoff indicates that interglacial periods experienced more humid conditions than the glacial periods. The north‐south SST gradient is systematically steeper during glacial times, suggesting a mean background climatic state with a vigorous oceanic cold tongue, resembling modern La Nina conditions. This enhanced north‐south SST gradient would also imply a glacial northward shift of the Intertropical Convergence Zone at least in vicinity of the cold tongue: a pattern that has not yet been reproduced in climate models.

Eastern equatorial Pacific cold tongue during the Last Glacial Maximum as seen from alkenone paleothermometry

We present new alkenone‐based sea surface temperature (SST) estimates from the eastern equatorial Pacific (EEP) for the last 30 kyr. By combining these new results with recently published records from the region, we reconstruct the spatial pattern of changes in SST during the Last Glacial Maximum (LGM). Alkenone‐based SST estimates show a greater glacial cooling in the upwelling environment of the cold tongue than in sites located further north in the equatorial front and eastern Pacific Warm Pool. This result agrees with the paradigm of stronger glacial winds, increased upwelling, steeper zonal thermocline tilt, and stronger advection of cold water in the Peru Current. Furthermore, we investigate possible changes in glacial surface hydrography by using the alkenone‐based SST reconstructions to correct planktonic foraminifera δ18O for the temperature effect. After additional correction for the global ice volume effect, the residual changes in seawater δ18O show a clear latitudinal pattern that would be consistent with a southward shift of the Intertropical Convergence Zone. We thus suggest that changes in sea surface salinities could explain contrasting SST reconstructions based on planktonic foraminifera δ18O, which implied a weakening of the cold tongue. The controversial LGM dynamics of the EEP reconstructed by different proxies, i.e., a weakening or a strengthening of the cold tongue, highlight the necessity to better assess the influence of various biases on these proxies.

Air–sea interaction over ocean fronts and eddies

Air–sea interaction at ocean fronts and eddies exhibits positive correlation between sea surface temperature (SST), wind speed, and heat fluxes out of the ocean, indicating that the ocean is forcing the atmosphere. This contrasts with larger scale climate modes where the negative correlations suggest that the atmosphere is driving the system. This paper examines the physical processes that lie behind the interaction of sharp SST gradients and the overlying marine atmospheric boundary layer and deeper atmosphere, using high resolution satellite data, field data and numerical models. The importance of different physical mechanisms of atmospheric response to SST gradients, such as the effect of surface stability variations on momentum transfer, pressure gradients, secondary circulations and cloud cover will be assessed. The atmospheric response is known to create small-scale wind stress curl and divergence anomalies, and a discussion of the feedback of these features onto the ocean will also be presented. These processes will be compared and contrasted for different regions such as the Equatorial Front in the Eastern Pacific, and oceanic fronts in mid-latitudes such as the Gulf Stream, Kuroshio, and Agulhas Return Current.

Phytoplankton biomass distribution and identification of productive habitats within the Galapagos Marine Reserve by MODIS, a surface acquisition system, and in-situ measurements

The Galapagos Marine Reserve (GMR) is one of the most diverse ecosystems in the world. Phytoplankton are the base of the ecosystem food chain for many higher trophic organisms, so identifying phytoplankton biomass distribution is the first step in understanding the dynamic environment for effective management of the GMR. Moderate Resolution Imaging Spectroradiometer (MODIS) and hyperspectral surface acquisition system derived chlorophyll, in-situ chlorophyll fluorescence, nitrate, salinity, and temperature were collected from March 2005 to the onset of a mild El Niño in November 2006. Islands in the eastern GMR, such as San Cristobal and Espanola, are the first to experience impacts of El Niño and southern migration of the Equatorial Front. Productive habitats were defined as surface waters with salinities > 34, temperatures < 24 °C, and chlorophyll a > 0.4 mg m − 3 . Six temporally variable productive habitats identified were: west of Isabela Island, southwest of Floreana Island, south of Santa Cruz, between Santiago and Santa Cruz Islands, and on the eastern side near San Cristobal Island. Model results coupled with surface acquisition system derived chlorophyll indicated productive habitats may also occur for short periods and at a distance from islands such as when the Equatorial Undercurrent (EUC) and South Equatorial Current (SEC) collide over the seamounts north of Isabela Island. All productive habitats were related to topographic upwelling from the EUC into surface waters.