BIOPHYSICAL INTERACTIONS OFF WESTERN SOUTHAMERICA Vivian Montecino and Ted Strub

1. BIOPHYSICAL INTERACTIONS OFF WESTERN SOUTHAMERICA Vivian Montecino and Ted Strub Tim Baumgartner, Juan Tarazona, Francisco Chavez

2. 1. Introduction • 2. Physical characteristics and dynamics • 3. Lower trophic level bio-physical interactions and bio-geochemical patterns. • 3.1Patterns and interactions in space • 3.2Patterns and interactions in time • 3.3CO2 fluxes, productivity and interactions of multiple scales • 4. Holozooplankton and merozooplankton. • 4.1 Composition and distribution of plankton species, considering relative body size and behavior. • 4.2. Grazing, growth and secondary production • 5. Benthic and nearshore biogeochemistry and biogeographic patterns • 5.1 Sedimentation, nutrient regeneration and the benthic continental shelf habitat • 5.2.The nearshore ecosystems • 6. Fish distribution and regime shifts • 7. Energy transfer, carbon cycles and links to intertidal in some example systems • 7.1.Several locations selected according to longer term research and width of the shelf • 7.1.1 The Gulf of Guayaquil and Peruvian bays. • 7.1.2. Mejillones Península • 7.1.3. Gulf of Arauco, several bays and the Concepción shelf. • 7.2.Trophic relationships, energy transfer and carbon cycles • 7.3.Links to intertidal • 8. Anthropogenic influences • 9. Conclusions

3. Main bottom and coastal features: Andes, Nazca Ridge, trench, shelf, islands, inland Sea Courtesy: O.Pizarro & G. Yuras

4. Winds and Currents: Seasonality is weak in comparison to the Northern Hemisphere (Figure from Strub et al 1998).

5. Seasonal changes in Atmospheric pressure; NCEP climatology.

6. A = Subtropical Anticyclone • CT = Land-Ocean Thermal Contrast • AI = Subtropical Anticyclone influence in austral winter • AA = Subtropical Anticyclone • influence year round • BC = Coastal Lows influence zone of Bup • AV = Subtropical Anticyclone Influence in Summer • Blow = Polar front perturbation zone represented by extra-tropical cyclones and associated fronts Metorological factors of UFW

7. Offshore Ekman Transports – ERS-2 Scatterometer

8. North of 40ºS, the system has all of the features expected of Eastern Boundary Current upwelling systems (Figure from Hill et al., 1998).

9. Oxygen in 1 degree box next to the coast from NODC data (F. Chavez)

10. Oxygen in 1 degree box next to the coast from NODC data (F. Chavez). S. Hemisphere.

11. Monthly time series of the depth of the oxycline and thermocline at different latitudes off northern Chile (from Morales et al., 1999).

12. WOCE Lines Perú

13. WOCE Lines Chile

14. Regions of the Main Secondary Nitrite Maximum (Codispoti et al., 1989).

15. Phytoplankton primary production Chlorophyll Holo and meroplankton

16. Summer (left) and Winter Surface Chlorophyll Concentration from SeaWiFS Satellite data (non-El Nino Years).

19. Chlorophyll a 23º S 30º S R. Torres et al. 2002

20. Atkinson et al

21. CHILE- Inland Sea 9 January 1999

22. Thomas et al. 2001

23. Primary production (mgC m-2 d-1)

24. Phytoplankton size Montecino 2001

25. ANOVA All conditions: Place, Upwelling and ASL

26. R. Torres et al. 2002

27. Gonzalez & Marin 1998 Most abundant species in the Chilean coast C. chilensis and Centropagus braquiatus. Life cycles mechanisms.... no vertical migration > abundance within 10 km

29. Three/four provinces: *Panamic, *Peruvian *Perú-Chile *Magellanic Breaks, discontinuities and diversity hotspots. M. Fernandez et al 2000

30. Intertidal biogeography Seaweeds of Perú and Chile indicate an effective isolation from the Western Pacific, the Central Pacific Islands and the Eastern Tropical Pacific. Principal characteristic: contributions of tropical and subantarctic elements, combined with high endemism. Tropical and subantarctic influence extends to littoral fish diversity off Chile, which remains fairly constant along the coast down to 40ºS and declining south of this latitude. Processes are driven by differential reproductive seasonality and larval recruitment. Temporal variability is caused by large-scale changes in advection patterns- ENSO cycle. These cause recruitment changes and southward range extensions of some broadcasting species, which normally have warmer water affinities.

31. 1601 macroinvertebrate species Mollusca 611, Polychaeta 403, Crustacea 370 52% endemism Lancellotti & Vasquez 2000

32. Spatial patterns across the continental shelf off Chile, in which Beggiatoa and Thioploca mats occupy the anoxic regions, provide habitat for other species, allowing different degrees of bioturbation (Arntz et al. 1991, Gallardo et al. 1995, Schulz et al. 1996, Gutiérrez et al. 2000). These mats store nitrate that is used in the sulfide oxidation so the bacteria may grow autotrophically or mixotrophically using acetate or other organic molecules as a carbon source. The filaments of Thioploca stretch up into the overlying seawater, from which they take up nitrate, and then extend down 5-15 cm deep into sediments to oxidize sulfide formed by intensive sulfate reduction. The very high sulfate reduction rates contribute further to anoxic conditions of the bottom water. Thioploca mats are responsible for converting new nitrogen into biologically available substrate in the seabed of the eastern Pacific shelf, catalyzing reactions like nitrite amonification. In the sediments off Concepción, the NO3- consumed may be reduced to NH4+, rather than to N2, which increases the oxidative capacity of the NO3- pool by 60% (Farías 1998) This increase in amonium fluxes contributes to low CO2: NH4+ accumulation ratios in the bay and shelf sediments and confirms the extremely high carbon oxidation rates, in which sulfate reduction is the dominant pathway near the surface sediments. As Fe distribution decreased with depth, the importance of SO42- reduction increases and Fe reduction becomes the second most important in carbon oxidation of continental margin sediments (Thamdrup and Canfield 1996). Ammonium fluxes obtained from the flocculent layer and Beggiatoa mat cultures, represent about 39% of total ammonium out-flux during the spring-summer period bloom. Products of this process are mainly ammonia, nitrite, di-nitrogen, and elemental sulfur. (Fossing 1990, Fossing et al. 1995, Jôergensen and Gallardo 1999). Bacterial mats could also contribute to nitrogen losses in upwelling areas through their biomass preservation and burial in the sediments (Farías 1998). Large interannual variability exists in this anoxic biogeochemical cycling due to perturbations of the depth of the thermocline and oxycline, associated with the ENSO cycle. During El Niño years, especially close to the coast, the significantly deeper oxycline subjects the shallow sediments to strong oxygenation. During ‘normal’ and La Niña years, the rise of the oxycline extends anoxic conditions over the same shallow sediments. During this time, Thioploca act as an efficient benthic habitat detoxifier (Arntz et al. 1991).

33. Tº, O2 Nº species Macrobenthos density Bahía Ancon 1981-1997 Tarazona & Sanchez 1999

34. Schwartzlose et al. 1999 Fish distribution and regime shifts

35. Schwartzlose et al 1999 Biomass- recruitment

36. Salmon production for 2001 aprox. 300 000 tons Thousand millions US$ 70% in the X Region, the rest to the south 50% of production is Salmo salar, the rest Coho and trouth. Doris Soto, pers. Comm.

37. Red Tides monitoring stations events VPM Guzman et al. 2002

38. CONCLUSIONS 1. Seasonal changes in wind forcing and circulation are weaker at mid-latitudes than in the California Current. Seasonal changes in radiation, SST and stratification are strong, especially at low latitudes. 2. In the PUC *the oxygen minimum is strong and determines the nature of denitrification off southern Perú and northern Chile. *nutrients are concentrated which serves as the source of upwelled water in many locations. 3. As in other systems, CO2 outgassing occurs during upwelling. 4. Primary Production values are large off both Perú and Chile.

39. 5. Much of the chlorophyll biomass is found within 100-200 km of the coast. The maximum in surface chlorophyll in the region within 100 km of the coast occurs in austral summer off both Perú and Chile, although the maximum upwelling winds occur in winter off Perú and summer off central Chile. 6. During upwelling pulses and relaxations off central Chile, physical and chemical variables respond in a simple fashion, but a multiscale approach is needed to understand phytoplankton and zooplankton patterns. 7. Advection of mesoscale structure contributes to the complexity of the measured variables.

40. 8. Small pelagic fish undergo multidecadal scale fluctuations, with instances of alternating species. 9. South of 42ºS in the inland sea region, high levels of precipitation creates regions of buoyancy-driven flow, while strong tidal currents increase the rate of flushing of the systems. 10. This same southern region is used for the growing Salmon Aquaculture industry. The flushing may help reduce the effects of eutrophication. 11. Harmful algal blooms are a growing problem in the regions off southern and central Chile.

41. ACKNOWLEDGEMENTS: IOC-UNESCO IAI GLOBEC-USA PRODAC UNIVERSIDAD DE CHILE