BIOPHYSICAL INTERACTIONS OFF WESTERN SOUTHAMERICA

Vivian Montecino and Ted Strub

Tim Baumgartner, Juan Tarazona, Francisco Chavez

1. Introduction2. 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 time3.3CO2 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 patterns5.1 Sedimentation, nutrient regeneration and the benthic continental shelf habitat

5.2.The nearshore ecosystems6. Fish distribution and regime shifts7. 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 cycles7.3.Links to intertidal

8. Anthropogenic influences9. Conclusions

Main bottom and coastal features: Andes, Nazca Ridge, trench, shelf, islands, inland Sea

Courtesy: O.Pizarro & G. Yuras

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

Seasonal changes in Atmospheric pressure;NCEP climatology.

Metorological factors of UFW•A = Subtropical Anticyclone

•CT = Land-Ocean Thermal Contrast

•AI = Subtropical Anticyclone influence in austral winter

•AA = Subtropical Anticycloneinfluence 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

Offshore Ekman Transports – ERS-2 Scatterometer

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

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

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

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

WOCE Lines Perú

WOCE Lines Chile

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

Phytoplankton primary production

Chlorophyll

Holo and meroplankton

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

23º S

30º S

Chlorophyll a

R. Torres et al. 2002

Atkinson et al

-74 -73

-40

-39

-38

-37

-36-74 -73

-40

-39

-38

-37

-36

50 (cm /s)50 (cm /s)

10 11 12 13 14 15 16 17 18 19

SST (°C)

AVHRR

(12/09/1998)

Chlorophyl [mg/m3]

SEAW IFS

(12/09/1998)

0.01 0.1 1.0 10 64

a) b)

Figure 4. a) Sea surface temperature from AVHRR for December 9, 1998. b) Surfacechlorophyll SeaWifs image for December 9, 1998. Currents at 4 meters depth, everyfifth observation, are plotted. 50 cm s-1 vector is indicated.

CHILE- Inland Sea 9 January 1999

Thomas et al. 2001

min mean max Reference Year Site390 1100 2580 Guillen & Calienes 1981 Chimbote, Perú

2290-4820 Chavez & Barber 1987-1985 Perú3200 a Chavez et al 1989 Perú

3700-5200 a Mendo et al 1989 Perú3500 Chavez 1995 Perú

0.7* 1.8* Daneri et al 2000 Nazca 1995539 5811 Pizarro... Iriarte 2000 Antofagasta, Chile

120-800 b 5100-9300 b Daneri et al 2000 Antofagasta, Chile140 2950 Montecino et al 1996 Coquimbo, Chile

660 b 2800 b Daneri et al 2000 Coquimbo, Chile200 w630-1920sp 7480 Montecino et al 2001 Concepción, Chile

320 b 5900 b Daneri et al 2000 Concepción, Chile500 6000 Daneri et al 2001 Concepción 1989-9198 1380 Pizarro et al 2000 Chilean Fjords 47º-50ºS

a=new production w=winterb=Oxygen sp=spring

HCS year = 500-930 g C m-2 y-1

Primary production (mgC m-2 d-1)

Primary production (mgC m-2 d-1)

Montecino 2001

Phytoplankton size

Upw

ANTOFAGASTA up p= 0.052 mean SD p= 0.007 mean SDNiño 13 130 141.6 Niño 10 50.2 30.8Niña 4 197.5 107.6 Niña 1 69 0

Trans 28 77.7 58.8 Trans 11 110.9 74.5

down p=0.008 mean SD p= 0.032 (K-W) mean SDNiño 15 100.3 Niño 15 80.6 20.8Niña 2 173.4 Niña 5 167.2 58.2

Trans 23 60.7 Trans 16 177.3 323

COQUIMBO up p=0.07 mean SD p= 0.52 mean SDNiño 13 79.0 50.8 Niño 6 44.4 31.1Niña 13 43.8 31.5 Niña 8 49.5 23.6

Trans 1 14.3 0.0 Trans 0

down p= 0.23 mean SD p= 0.40 mean SDNiño 8 32.1 17.1 Niño 4 42.7 17.1Niña 3 52 19.5 Niña 0

Trans 10 32.5 17.7 Trans 3 60.7 35.1

VALPARAISO up p= 0.008 mean SD p= 0.07 mean SDNiño 10 34.6 29.96 Niño 10 37.7 30Niña 4 79.8 27.64 Niña 4 75.9 27.6

Trans 0 Trans 0

p= 0.11 mean SD p= 0.51 mean SDdown Niño 6 32 47.1 Niño 8 45.6 39.2

Niña 6 57.4 28.6 Niña 4 60.3 21.8Trans 0 Trans 0

ASL

Active Relaxed

ANOVA All conditions: Place, Upwelling and ASL

R. Torres et al. 2002

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

Three/four provinces:

*Panamic, *Peruvian*Perú-Chile *Magellanic Breaks, discontinuities and diversity hotspots.

M. Fernandez et al 2000

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.

1601 macroinvertebrate speciesMollusca 611, Polychaeta 403, Crustacea 37052% endemism Lancellotti & Vasquez 2000

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).

Tarazona & Sanchez 1999

Tº, O2

Nº species

Macrobenthos density

Bahía Ancon 1981-1997

Schwartzlose et al. 1999 Fish distribution and regime shifts

Schwartzlose et al 1999

Biomass-recruitment

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.

Red Tides

monitoring stations

eventsVPM

Guzman et al. 2002

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.

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.

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.

ACKNOWLEDGEMENTS:ACKNOWLEDGEMENTS:

IOC-UNESCOIOC-UNESCO

IAIIAI

GLOBEC-USAGLOBEC-USA

PRODACPRODACUNIVERSIDAD DE CHILEUNIVERSIDAD DE CHILE