José Luis Iriarte

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

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

Primary production and biomass of size-fractionated phytoplankton off Antofagasta, Chile (23-24°S) during pre-El Niño and El Niño 1997

During a major study focusing on the fate of primary production through the food web in an upwelling system located in the Humboldt Current System, Antofagasta, Chile (23–24°S), we examined the spatial variation of phytoplankton size structure. One of the main objectives was to estimate primary production (14C) and chlorophyll-a biomass for three phytoplankton size fractions; pico-, nano- and micro-phytoplankton, at coastal ( 23 μm) increased its relative contribution to primary production from oceanic (12%) to coastal (21%) stations and was related to an upwelling process which was restricted to a narrow inshore band (<15 nmi). During July (El Nino conditions), primary productivity ranged from 0.39 to 10.7 mg C m−3 h−1 (mean=3.4 mg C m−3 h−1). The pico- and nanoplankton fractions dominated both oceanic and coastal stations and both fractions accounted for 67% of the primary production and chlorophyll-a biomass. We suggest that an oceanographic anomaly observed during July (1997 El Nino), associated with the intrusion of warmer oceanic waters to the coastal border, reduced the upwelling of nutrient-rich waters in the upper 200 m to a narrow coastal band (<6 nmi) leading to a higher dominance of pico- and nanoplankton populations in inshore waters. These observations show that pico- and nanoplankton size fractions make a significant contribution to the production and biomass, and may thus represent an alternative energy flow pathway within this upwelling area.

Phytoplankton biomass in the sub-Antarctic area of the Straits of Magellan (53°S), Chile during spring-summer 1997/1998

Abstract In order to provide a better understanding of the dynamics of phytoplankton in the coastal regions of high latitudes, a study was carried out to estimate the dynamics of carbon biomass of autotrophic and heterotrophic algal groups over the austral spring-summer 1997/1998 period. At a fixed station located in the central basin (Paso Ancho) of the Straits of Magellan (53°S), surface water samples were collected at least once a week from September 1997 (early spring) to March 1998 (late summer). Quantitative analysis of biomass of phytoplankton was estimated from geometric volumes, using non-linear equations, and converted to biomass. The pattern of chlorophyll a showed a strong temporal variability, with maximum values (mean 2.8 mg m−3) at the austral spring phytoplankton increase or bloom (October/November) and minimum values during early spring (September: <0.5 mg m−3) and summer (January/March: 0.5–1.0 mg m−3). During the spring bloom, diatoms made up to 90% of the total phytoplankton carbon (0.01–189 μg l−1), followed by a maximum of thecate dinoflagellates (0.08–34 μg l−1), and sporadic high biomass of phytoflagellates during summer. Heterotrophic algal groups such as Gymnodinium and Gyrodinium spp. dominated (70%, in the 5- to 25-μm size range) shortly before the main diatom bloom, and small peaks were observed within spring and early summer periods (0–0.4 μg l−1). Phytoflagellates dominated earlier (spring) with higher carbon biomass (8 μg l−1) and post-bloom periods (summer) when carbon biomass ranged between 1 and 4 μg l−1.

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

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

Influence of hydrological regime of an Andean river on salinity, temperature and oxygen in a Patagonia fjord, Chile

Patagonian fjord ecosystems might experience new scenarios due to climate variability (decreasing annual precipitation and glacier melting) in the short term. Herein, we studied the seasonal variability of the Puelo River regime (North Patagonia, 1944–2007, mean streamflow: 650 m3/s) and analyses its influence on surface salinity, temperature and dissolved oxygen in the well-stratified Reloncaví Fjord (41.5°S). Our results show a decreasing trend in the Puelo River streamflow since the late 1970s that is frequently associated with regimes lacking a defined interannual pattern. During the study period, years with prolonged periods of low streamflows in autumn and winter were common. On a scale of hydrological years, the influence of the Puelo River on the surface layer of the Reloncaví Fjord varied strongly in function of both the rivers streamflow level and regimes. Years with markedly mixed regimes (rainfall/snowmelt), high autumn and spring streamflows (Q>1000 m3/s) resulted in significantly cooler, fresher conditions in the fjord. These temporal patterns, in turn, determined high, constant saturations (100%) and concentrations (10 mg/l) of surface dissolved oxygen. By contrast, the discharge pattern of 2007 led to stable, low streamflows in autumn and winter (Q=250 m3/s) that did not influence temperature or salinity. A significant association was found between the temporal variability of the salinity (increasing from 6 to 28 psu) and low dissolved oxygen saturation (<50%) and concentration (<5 mg/l), largely dominated by wind events.

Naturalized Chinook salmon in the northern Chilean Patagonia: Do they originate from salmon farming?

En los rios del sur de Chile se han registrado individuos desovantes de salmon Chinook (Oncorhynchus tschawytscha). Esta especie fue introducida a partir del 1900 hasta los 80� y se cultiva actualmente en el mar. Nuestro objetivo fue identificar la procedencia de los salmones Chinook asilvestrados en el rio Petrohue, mediante el uso de 3 loci microsatelites. Los resultados fueron comparados con muestras de individuos obtenidos desde cultivo. Los resultados mostraron mayor variabilidad genetica en los individuos asilvestrados que la obtenida en los individuos de cultivo y ademas se observo divergencia genetica entre ellos, lo que permite indicar que las poblaciones de salmones desovantes en el rio Petrohue actualmente no son explicadas por posibles escapes desde los grupos de salmones de cultivo, sino mas bien corresponderian a poblaciones generadas desde los grupos liberados con fines de repoblamiento antes del comienzo de su cultivo.

Chlorophyll-a MODIS mesoscale variability in the Inner Sea of Chiloé, Patagonia, Chile (41-43°S): Patches and Gradients?

Satellite images are powerful tools to describe meso- and large-scale spatial structures, thus helping in the comprehension of the physical-biological proces...

Hydroclimatic conditions trigger record harmful algal bloom in western Patagonia (summer 2016)

A harmful algal bloom (HAB) of the raphidophyta alga Pseudochattonella cf. verruculosa during the 2016 austral summer (February-March) killed nearly 12% of the Chilean salmon production, causing the worst mass mortality of fish and shellfish ever recorded in the coastal waters of western Patagonia. The HAB coincided with a strong El Niño event and the positive phase of the Southern Annular Mode that altered the atmospheric circulation in southern South America and the adjacent Pacific Ocean. This led to very dry conditions and higher than normal solar radiation reaching the surface. Using time series of atmospheric, hydrologic and oceanographic data we show here that an increase in surface water temperature and reduced freshwater input resulted in a weakening of the vertical stratification in the fjords and sounds of this region. This allowed the advection of more saline and nutrient-rich waters, ultimately resulting in an active harmful algal bloom in coastal southern Chile.

Mesoscale primary production and bio-optical variability off Antofagasta (23-24º S) during the transition to El Niño 1997-1998

The spatial variability of primary production (PP), chlorophyll-a (Chl-a) and the photosynthetic parameters were studied off Antofagasta, Chile (23-24° S, 70-72° W) during austral summer and winter. Between cruises (January and July 1997), significant changes occurred in the water column, including higher temperatures in the euphotic zone (Z eu ) deepening of thermocline below Z eu , an increase of oxygen concentration and the intrusion of Subtropical Waters with potential limitation of nutrients. These strong physical anomalies due to the transition period of El Nino 1997-1998 appeared in this study area during March 1997. During the July cruise, the El Nino event 1997-1998 was in the middle of its development (IOS–2). The hypothesis that chlorophyll-a concentrations and primary production differ significantly in the coastal areas in the Antofagasta region due to year-round coastal upwelling was tested in this study. Photosynthesis versus irradiance (P-E) experiments were performed daily, using simulated in situ incubations with samples collected within the Z eu . Also in vitro incubations were done at several selected stations. For results analyses, stations were pooled in coastal and oceanic sites according to distance from the narrow shelf and differential influence of local upwelling. Integrated Chl-a values during both cruises were significantly higher at the coastal stations, and since between cruises no differences were found, a mean value of 44 mg Chl-a m can be reported for the coastal area. Daily PP values were significantly different in space and time (P < 0.001), and at the coast also between cruises (P < 0.004) as a result of the high mean coastal value in January, 3,129 mg C m d in comparison to 942 mg C m d in July. The attenuation coefficient k d of photosynthetic active radiation (PAR), determined a significant change in the mean depth of Z eu between coastal and oceanic stations (44 ± 20 and 80 ± 17 m, respectively) during both sampling periods. Notwithstanding the spatial differences in chlorophyll-a concentrations and primary production, the observed weaker upwelling favourable winds during both cruises, the increase in depth of the mixing layer and light limitation in July, and the higher mean values of zooplankton grazing rate during January contributed to the similar abundance of chlorophyll-a in time. Although the El Nino event could negatively affect primary production during July, prevailing space and seasonal variability masked this effect.

Influence of seasonal freshwater streamflow regimes on phytoplankton blooms in a Patagonian fjord

ABSTRACT Large-scale regional phenomena and global climate trends may alter the freshwater discharge of large Patagonian rivers and could modify local circulation patterns in ways that influence phytoplankton dynamics. Modifications detected in the streamflow regime of the Puelo River (41.5° S, Patagonia, Chile) in recent decades may affect the regularity of seasonal phytoplankton blooms in Reloncaví Fjord. We examined the occurrence/frequency of spring–summer and autumn phytoplankton blooms in Reloncaví Fjord with respect to seasonal and inter-annual changes in freshwater streamflows from 2003 to 2011. Surface chlorophyll-a derived from satellite-ocean colour and phytoplankton abundances revealed that significant recurrences of autumn phytoplankton blooms (> 2 mg Chl-a m−3, > 500 cell mL−1) were associated with historical low mean freshwater streamflows, mainly in autumn (< 350 m3 s−1). On the other hand, the occurrence of spring–summer blooms was related to high streamflows (> 470 m3 s−1) that increased mixing in the upper photic layer enough to enhance phytoplankton growth. Our findings imply that the intensity of autumn blooms in Reloncaví Fjord could be modulated by streamflow strength.