Oceanographic Processes in Chilean Fjords of Patagonia: from Small to Large-Scale Studies

Progress in Oceanography 129 (2014) 1–7

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Progress in Oceanography

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Preface Oceanographic Processes in Chilean Fjords of Patagonia: From small to large-scale studies

Introduction from the fjords generating sharp vertical and horizontal salinity gradients (Fig. 1)(Dávila et al., 2002; Acha et al., 2004; Subantarctic ecosystems, such as the inner shelf of southern Valle-Levinson et al., 2007; Pérez-Santos et al., 2014; Schneider Chile (41–55°S), are characterized by a complex system of fjords, et al., 2014). Consequences of freshwater input are (1) a sizable channels, gulf, estuaries, bays, and are affected by physical regimes supply of terrigenous material from large rivers (600– that may strongly modulate biological productivity. Rhythms and 800 m3 sÀ1), ice melt and rainfall (2000–7000 mm yÀ1; e.g., colored rates of primary production in these highly fluctuating fjord envi- Dissolved Organic Matter, González et al., 2013; Lafon et al., 2014), ronments depend to a large extent on the timing and magnitude of particulate organic matter (Sepúlveda et al., 2011), (2) a cold and nutrient supply and light availability for primary producers. In freshwater layer overlying a salty-warm water layer that would such complex fjord systems, the interaction between oceanic favor small-scale double-diffusive layering processes, quantified waters and freshwater from multiple sources (e.g., rivers, surface for the first time in Chilean Patagonian fjords (Pérez-Santos et al., and groundwater runoff, snow/glacier melting, and precipitation) 2014), and (3) sharp latitudinal and longitudinal gradients of silicic produces strong vertical and horizontal gradients in salinity, den- acid due to surface water mixing between nitrate-rich but sity, organic and inorganic nutrient ratios and light availability Si-depleted oceanic subantarctic waters and Si-rich but nitrate (Pickard, 1971; Dávila et al., 2002; Silva and Palma 2006; Jacob depleted continental waters (Aracena et al., 2011; González et al., et al., 2014). The vertical structure of the water column (strati- 2011; Torres et al., 2014). fied/mixed), modulated by the seasonal and inter-annual changes Biological consequences of these water column processes are of the pycnocline may affect biomass and composition of pelagic evident: the stratifying effect of buoyancy is a key regulator of pri- and benthic assemblages, and ultimately spatial and temporal pat- mary production and biomass, limiting the depth of turbulent mix- terns of carbon fluxes (the ‘‘Biological Pump’’), and biogeochemical ing and thereby keeping algal cells within the photic zone (Jacob balances in this large region. In addition, the region is particularly et al., 2014). On the other hand, stratification isolates algae from vulnerable to climate change and anthropogenic influences (Iriarte their principal source of nutrients below the pycnocline and thus et al., 2010). Remote and large-scale climatic-oceanographic phe- may lead to the eventual shutdown of production after short nomena (e.g., ENSO and Southern Annular Mode) and global cli- bloom periods. Here, semidiurnal internal waves can increase ver- mate trends may alter freshwater discharge of large rivers such tical mixing of deep nutrients toward the surface, through shear as the Puelo and Palena, as has also been suggested for the Baker instabilities, which would favor primary production for more River located between Patagonian Ice fields and other northern extended periods than in classical seasonal systems (Ross et al., fjords shown by paleo-oceanographic (Sepúlveda et al., 2009; 2014). In addition, Valle-Levinson et al. (2014) demonstrated the Rebolledo et al., 2011) and dendrochronological studies (Lara existence (related to twilight) of semi-diel patterns of vertical et al., 2008). Although changes in climate are expected to alter migrations of euphausiids and decapods, which could be a com- the regional atmospheric forcing such as the West Wind Drift mon strategy in fjords. Furthermore, some of the Patagonian fjords (Quintana and Aceituno, 2012; Garreaud et al., 2013) and the local receive significantly higher loads of fine suspended sediments from ocean circulation in this region, including the northward expansion snow and glacier melt, which may limit the light available for pho- of the subantarctic water, the impact of these changes on physical tosynthesis in near-surface waters, and may explain the low bio- dynamics, biogeochemical and plankton properties are still logical production found in these fjords (Jacob et al., 2014). unclear. The information presented in this Special Issue (SI) will Distributions of harmful algal blooms (HABs, such as Chaetoceros be important to the understanding and modeling of future changes convolutus, Alexandrium catenella), known for their significant in the marine carbon cycle in Subantarctic zones off Patagonia. impact on aquaculture and human health and environmental issues, represent major research challenges in coastal waters of Main features of the coastal marine ecosystem the entire Patagonia marine ecosystem. The approaches used by Paredes et al. (2014) allow us to conclude the importance of extrin- The southern region of Chile contains one of the major fjord sic environmental factors (nitrate, temperature) to explain the regions of the world where salty waters of the Subantarctic Surface regional spatial scale of microphytoplankton groups, while toxic Water and Modified Subantarctic Waters mix with freshwater dinoflagellate species dynamics may be related to changes in the http://dx.doi.org/10.1016/j.pocean.2014.10.004 0079-6611/Ó 2014 Elsevier Ltd. All rights reserved. 2 Preface / Progress in Oceanography 129 (2014) 1–7 composition of microphytoplankton community at smaller spatial scales. Vertical migration, feeding, and reproduction of pelagic fish and zooplanktonic populations are also affected to the point that their spatial distribution results from the interaction of fresh and oceanic waters, mainly through the semi-permanent pycnocline observed in fjords and channels. The effect of river outflow was clearly demonstrated by Meerhoff et al. (2014) who pointed out that early and late-stage barnacle larvae were more abundant in waters of low temperature, high oxygen and high chlorophyll, while bivalve larvae were associated with warmer waters of oceanic origin. Population properties such as the ontogenic feeding pattern and distributions of fishes Sprattus fuegensis and Strango- mera bentincki, appeared to benefit from taking advantage of short-term food pulses and thus overcoming changes in oceanographic conditions in fjords (Contreras et al., 2014).

Biogeochemical processes

Muñoz et al. (2014) and Zapata-Hernández et al. (2014) studied a newly discovered shallow cold seep site with bacterial sulfur mats in a Chilean Fjord. Cold seeps have been studied in many regions of the world, but as the authors point out, this is novel for Patagonian fjords. Stable isotope geochemistry of carbon, nitro- Fig. 2. Map showing the oceanic section from 40°Sto60°S off the Patagonia marine system (from World Ocean Database 2013). gen and water, as well as vent fluid geochemistry helped establish that the cold seeps represent a site of chemosynthetic activity that sustain bacterial sulfur mats and are the source of methane in the and more saline subsurface layer are the main drivers of spring water column (Muñoz et al., 2014). In the community associated pulses in primary production and autotrophic biomass in the inner with the cold seeps, the food web is maintained mainly by photo- seas of Patagonia (González et al., 2013). The concentrations of synthetic primary production, and bacterial filaments of the mat inorganic nutrients show a strong seasonal signal, with high nitrate may be incorporated into the diet of some grazers (Zapata- and orthophosphate concentrations during winter, and lower val- Hernández et al., 2014). These studies characterize the chemical ues during spring, presumably caused by a sharp increase in pri- composition of reduced compounds in the vent fluids emanating mary productivity when light availability in near-surface waters from the rocks that might help understand the presence of bacte- increases (Iriarte et al., 2007; González et al., 2011; Torres et al., rial mats nearby, and the functioning of shallow water reducing 2011; Jacob et al., 2014). Oxygen concentrations in the fjords is systems. mostly the result of horizontal advection of adjacent well-oxygen- Vertical mixing and the exchange of nutrients among the ated Subantarctic Waters (5–6 mL LÀ1) that represents the major low-salinity, low nutrient and turbid surface layer and the warmer source of oxygen in the deep layers of the inner seas of Patagonia

Fig. 1. Schematics of important coastal processes considered in this compilation of articles showing geomorphology (glaciers), physical forcing (wind stress, atmosphere– ocean temperature exchange) and distributions of waters of different temperature and salinity in Patagonian fjords. Permanent surface freshwater plumes from the rivers’ watershed, and ice melt from glaciers, on top of warm and salty oceanic waters promote a sharp near surface stratiﬁcation (halocline and pycnocline) of the water column. Nutrient enrichment of the near surface waters (photic layer) may occur through tidal fronts, tidally induced internal waves, shear instabilities and small scale processes such as double diffusive convection. (Figure credits, Dr. Ivan Peréz-Santos). Preface / Progress in Oceanography 129 (2014) 1–7 3

Fig. 3. Hydrography and oxygen data collected from 40°Sto60°S. (a) Temperature, (b) salinity, (c) oxygen, (d) oxygen saturation. Water with salinity of ca. 33.5 in the upper 100 m to 50°S is shown in purple. Note the intrusion of subsurface oxygen (3 mL LÀ1, 100–200 m) of Equatorial Subsurface Waters extending southward to 47°S (northern Patagonia section). (For interpretation of the references to color in this ﬁgure legend, the reader is referred to the web version of this article.)

(Silva and Vargas, 2014). The authors suggest that oxygen levels column in the inner continental shelves of Patagonia. Oceano- below saturation found near fjord heads were the result of bacte- graphically, the fjords and channels of southern Chile could be con- rial respiration of autochthonous and allochthonous particulate sidered as a transitional marine system, influenced by oceanic deep organic matter, as ocean waters flow towards the continental fjord waters of high salinity and nutrients and surface freshwater of low heads, where near-hypoxic (2–3 mL LÀ1) or hypoxic levels salinity and nutrients (Schneider et al., 2014). Surface estuarine (<2 mL LÀ1), and increasing phosphorus and nitrate concentrations waters have low concentrations of nitrate and orthophosphate have been reported. with the oceanic Subantarctic Surface Waters being the main subsurface source (Silva and Neshyba, 1979; González et al., 2011; Oceanic effects on Patagonian inner coastal waters Pérez-Santos et al., 2014). To a large extent, the input of silicic acid (DSi) to surface waters is driven mainly by river runoff through the A better understanding of fjord dynamics will require a resolu- weathering of continental rocks (Tréguer and De la Rocha, 2013). tion of meso- and large-scale processes occurring in oceanic waters Thus, strong changes in availability of silicic acid for primary pro- adjacent to the fjord region. Future studies should focus on the ducers may result from fluctuations in freshwater discharges understanding of large-scale oceanic circulation, water masses (Torres et al., 2014), which in addition to seasonal processes, properties, their dynamics and their effect on the variability of bio- may be undergoing longer-term changes associated with global cli- logical productivity and biogeochemical cycling through the water mate trends (Tréguer and De la Rocha, 2013). 4 Preface / Progress in Oceanography 129 (2014) 1–7

Fig. 4. Depth distribution of phosphate (a), nitrate (b), silicic acid (c) from 40°Sto60°S Waters with relatively low phosphate (<1 lM) and nitrate (<10 lM) in the upper 50 m between 41° to 50°S are shown in blue-purple. (For interpretation of the references to color in this ﬁgure legend, the reader is referred to the web version of this article.)

Although the studies in this Special Issue focused on the inner et al., 1998), including the Antarctic Polar Front waters character- seas and fjords of Patagonia, we also provide basic knowledge for ized by low temperatures (<6 °C), high salinities (33.7–34.5) and a more comprehensive and integrative framework for ecosystem oxygen concentration above 6 ml LÀ1 (Fig. 3). research. Specifically, it has become clear that the importance of The entire oceanic region adjacent to the Patagonian fjords pre- large-scale oceanic processes, such as the entrainment of south- sents relatively high inorganic nutrient concentrations with pro- ern/northern water masses into the fjords, their interaction with nounced north–south and depth gradients (Fig. 4). Both nitrate freshwater discharges, and the effect on the biological productivity and orthophosphate concentrations increased southward in fresh- need to be addressed. At present, characterization of the deep oce- water, in the subantarctic zone and Antarctic Polar Front, with anic region south of 41°S and how it influences the inner shelves of lower surface (<100 m) values (<10 lM nitrate, <1 lM orthophos- Patagonia still lacks adequate oceanographic information. Avail- phate) in the northern-central sections (41–50°S). Silicic acid able information (Fig. 2; World Ocean Atlas, 2013) indicates that concentrations increased markedly southward up to 20 lM at the open ocean waters adjacent to the fjords are characterized by Antarctic Polar Front, with low values (<5 lM) at surface layer marked vertical (surface to 400 m) and horizontal (>100 km) phys- along the Patagonian margin (<50°S) (Fig. 4). In the region between ical and chemical gradients (Figs. 3–5). First, we note a marked the Subantarctic zone and the Antarctic Polar Front (50–55°S), we contrast between the northernmost section off Patagonia (41– suggest that advection of nitrate and orthophosphate into the 45°S) and the Antarctic Polar Front (55°S). Average temperature near-surface by upwelling of water from below (about 150 m decreases and salinity increases southward until it reaches the depth) could be important to provide nutrients for phytoplankton Antarctic Polar Front. Second, the northern and central sections growth. However, the region north of the Antarctic Polar Front off Patagonia (Subantarctic Zone at 41–50°S) are defined by tem- (50°S) was characterized by low surface silicic acid concentration perature >10 °C and salinity <34.0 in the upper 100 m (Fig. 3) until (<5 lM; Fig. 5) probably due to entrainment of subantarctic cur- they encounter subantarctic waters (55°S). Surface water salini- rents bringing low silicic acid waters into the southernmost section ties vary between 33 and 33.7 due to coastal freshwater input from off Patagonia (Torres et al., 2014). Along the northern coast of Chile larger rivers along the coast (i.e., the Puelo, Palena and Baker riv- in the Humboldt Current System, nutrient availability of surface ers). Freshwater decreases the density of near surface layer and waters is mainly controlled by the interplay between costal creates a steep horizontal density contrast across the shelf break upwelling (inorganic nutrients source) and microalgal productivity (Fig. 5). Third, several remotely-formed water masses are present (inorganic nutrients sink). Off the southern fjords, the adjacent in the subantarctic zone (41–55°S: Equatorial Subsurface Water, oceanic area may control inorganic nutrient availability in the Subantarctic Water, Freshwater Modified Subantarctic Water; Silva coastal ocean, and although it is beyond the scope of the present Preface / Progress in Oceanography 129 (2014) 1–7 5

Fig. 5. Distribution of surface temperature (a), salinity (b), oxygen (c), phosphate (d), nitrate (e), and silicic acid (f) in the southeastern Paciﬁc Ocean (40–60°S), showing the oceanic spread of coastal freshwater with salinity in the range 32.2–33.7. Note the intrusion of waters with low silicic acid concentration (2–3 lM) extending southwards reaching inner waters at ca. 50°S.

Special Issue, it needs to be resolved if we are to more finely under- result of a comprehensive regional assessment, combining stand mechanisms triggering phytoplankton productivity in the capabilities such as synoptic seasonal oceanographic cruises fjord ecosystems of southern Chile. with observations with buoys and sensors of hydrographic, physical–chemical and meteorological variables, all to address pro- Summary cess-oriented studies. Environmental features and ecological vulnerabilities were important criteria in the decision to choose The articles of this Special Issue on Oceanographic Processes in to research the Patagonian marine system, given its sensitivity Chilean Fjords of Patagonia: from small to large-scale studies are the to effects of climate change in a pristine coastal zone that it is 6 Preface / Progress in Oceanography 129 (2014) 1–7 undergoing increasing human development, and is being affected González, H.E., Castro, L.R., Danieri, G., Iriarte, J.L., Silva, N., Tapia, F., Teca, E., Vargas, by intensive aquaculture industry (salmon and mussel farms) and C.A., 2013. Land-ocean gradient in haline stratificaction and its effects on plankton dynamics and trophic carbon fluxes in Chilean Patagonian fjords other activities such as land-use change and deforestation along (47–50°S. Progress in Oceanography 119, 32–47. the coast. This Special Issue allowed us to integrate research that Iriarte, J.L., González, H.E., Liu, K.K., Rivas, C., Valenzuela, C., 2007. Spatial and encompasses organisms of a wide size spectra (bacteria, benthic temporal variability of chlorophyll and primary productivity in surface waters of southern Chile (41.5–43°S). Estuarine Coastal and Shelf Science 74, and pelagic invertebrates, and early life stages of fishes), several 471–480. types of habitats (headwaters of the forested watersheds down- Iriarte, J.L., González, H.E., Nahuelhal, L., 2010. Patagonian Fjord ecosystem in stream to pelagic and benthic coastal marine ecosystems, includ- southern Chile as a highly vulnerable region: problems and needs. Ambio 39, 436–466. ing shallow water seep sites), as well as governing physical Jacob, B., Quiñones, R.A., Iriarte, J.L., Daneri, G., Tapia, F., Montero, P., Sobarzo, M., dynamics and chemical processes (hypoxia, macronutrients flux). 2014. Springtime size-fractionated primary production across hydrographic These results will motivate additional studies in the near future and PAR-light gradients in Chilean Patagonia (41–50°S). Progress in Oceanography. to better understand how this marine ecosystem will respond Lafon, A., Silva, N., Vargas, C.A., 2014. Contribution of allochthonous organic carbon to climate change and non-climatic multi-stressors, which are across the Serrano River Basin and the adjacent fjord system in Southern major drivers of change of the structure and function of marine Chilean Patagonia: insights from the combined use of stable isotope and fatty food webs. The two major drivers of change in the Patagonian acid biomarkers. Progress in Oceanography. Lara, A., Villalba, R., Urrutia, R., 2008. A 400–year tree-ring record of the Puelo River marine ecosystem that need to be understood include: (1) summer-fall streamflow in the Valdivian Rainforest eco-region. Climate Change changes in stream flows which will affect the physical dynamics 86, 331–356. of the water column, and (2) changes in fluxes of macro- and Meerhoff, E., Tapia, F., Castro, L., 2014. Spatial structure of the meroplankton community along a Patagonian fjord - role of changing freshwater inputs. micro-nutrients in the upper layers caused by oceanic currents, Progress in Oceanography. atmospheric dynamic, and nutrient discharges due to human Muñoz, P., Sellanes, J., Villalobos, K., Zapata-Hernández, G., Mayr, C., 2014. activity. Geochemistry of reduced fluids from shallow cold vents hosting chemosynthetic communities (Comau Fjord, Chilean Patagonia, 42°S). Progress in Oceanography. Acknowledgements Paredes, M.A., Montecino, V., Anic, V., Egaña, M., Guzmán, L., 2014. Diatoms and dinoflagellates macroscopic regularities shaped by intrinsic physical forcing variability in Patagonian and Fuegian fjords and channels (48–56°S). Progress in This article and the production of this Special Issue on Oceanography. Oceanographic Processes in Chilean Fjords of Patagonia: from small Pérez-Santos, I., Gárces-Vargas, J., Schneider, W., Ross, L., Parra, S., Valle-Levinson, to large-scale studies were sponsored by the COPAS Sur-Austral A., 2014. Double-diffusive layering and mixing in Patagonian fjords. Progress in Oceanography. Basal Program, grant # PFB-31. Special thanks go to the Editor of Pickard, G.L., 1971. Some physical oceanographic features of inlets of Chile. Journal Progress in Oceanography, Dr. Francisco Werner, for his support of Fisheries Research and Board of Canada 28, 1077–1106. throughout the production process. The authors wish to Quintana, J.M., Aceituno, P., 2012. Changes in the rainfall regime along the acknowledge the Hydrographic and Oceanographic Service of the extratropical west coast of South America (Chile): 30–43°S). Atmósfera 25, 1– 22. Chilean Navy (SHOA) and the National Oceanographic Committee Rebolledo, L., González, H.E., Muñoz, P., Iriarte, J.L., Lange, C.B., Pantoja, S., (CONA) for their support through the marine research program Salamanca, M., 2011. Siliceous productivity changes in Gulf of Ancud CIMAR FIORDOS. The holistic view (‘‘stressors’’ and ‘‘drivers’’ sediments (42° S, 72°W), southern Chile, over the last 150 years. Continental Shelf Research 31, 356–365. perspective) for Patagonian fjords was inspired by the Ocean Ross, L., Pérez-Santos, I., Valle-Levinson, A., Schneider, W., 2014. Semidiurnal Certain program EU-FP7 # 603773, and by the people of Caleta internal tides in a Patagonian fjord. Progress in Oceanography. Tortel and the Ilustre Municipalidad de Caleta Tortel in the Region Schneider, W., Pérez-Santos, I., Ross, L., Bravo, L., Hernández, F., Seguel, R., 2014. On the hydrography of Puyuhuapi channel (Chilean Patagonia). Progress in of Aysén. 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José L. Iriarte Giovanni Daneri Institute of Aquaculture, University Austral of Chile, Puerto Montt, Chile Center for Ecosystem Research in Patagonia, CIEP, Coyhaique, Chile COPAS Sur-Austral Program, University of Concepción, Chile COPAS Sur-Austral Program, University of Concepción, Chile E-mail address: [email protected] E-mail address: [email protected] Silvio Pantoja Available online 22 October 2014 Department of Oceanography, University of Concepción, Chile COPAS Sur-Austral Program, University of Concepción, Chile E-mail address: [email protected]