Santa Barbara Channel LTER

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Santa Barbara Channel LTER Oceanographic data
from near-shore stations, 2001, with implications
for nutrient delivery to kelp reefs
Erika McPhee-Shaw David Siegel Libe
Washburn Mark Brzezinski
University of California Santa Barbara David
Salazar, Mike Anghera, Janice Jones, Bryn Evans,
Helene Scalliet
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• Santa Barbara Channel LTER (Long-Term Ecological
  Research) Study
• NSF-funded LTER Interdisciplinary study of
  ecosystems in land/ocean interface.
• Objectives study spatial and temporal scales
  of terrestrial and oceanographic forcing,
  determine the relative importance of terrestrial
  versus oceanic sources of nutrients and
  other constituents to the kelp forest
  ecosystem.

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• Outline
• Oceanographic data time series and monthly
  hydrography
• from near shore stations. 2001
• Focus on mechanisms for nutrient delivery to
  kelp reefs
• Possible Mechanisms
• Terrestrial input
• Upwelling
• Internal waves/ tidal bores
• Advection from Point Conception/islands/other
  locations

Sources of Nutrients SPATIAL GRADIENTS
Vertical gradient Geographic gradient
nutrients generally higher north of Point
Conception, where coastal upwelling is common.
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LTER near shore stations for moorings and monthly
sampling
18 km
Moorings CTD, ADCP, fluorometer,
backscatter Nitrate auto analyzer deployed
October and December
( ? - Plumes and Blooms Stations (ongoing since
1996))
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(AVHRR composites from Mark Otero, UCSB)
Upwelling common north of Point
Conception Within channel, a cyclonic synoptic
state most common Hendershott and Winant, 1996
- Harms and
Winant, 1998
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Vertical Gradients Nutrients at depth.
Depth of nutricline changes
seasonally.
oC
mmol/L
From Plumes and Blooms mid-channel station -
(plot from Olga Polyakov)
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2001- Time series data from reef moorings at
Carpinteria and Naples
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EVENTS
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Naples Reef Monthly Nitrate Profiles
Blue inshore, green- reef, red offshore.
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Carpinteria Reef Monthly Nitrate Profiles
Blue inshore, green- reef, red offshore.
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April 4
March 7
CTD profiles at Naples Once per month,
2001 March - June
May 3
June 5
Green reef Blue - offshore
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July 3
August 1
CTD profiles at Naples Once per month,
2001 July December
Green reef Blue - offshore
October 5
November 7
December 5
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Terrestrial Runoff Events
Hydrograph Winter Spring, 2001. Santa Barbara
Streams USGS gauges Mission Creek at Rocky Nook
and Mission St. Atascadero at Patterson San Jose
at Goleta
(data from Ed Beighly)
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March Storm event
(40-day period)
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Nutrient Concentrations in Santa Barbara
Streams, Storm of March 3 6, 2001.
Mean Nitrate Concentrations (mM/l) during the Mar
3 -6 storm Arroyo Burro 71.3 Atascadero 64.
6 Mission 52.2 Franklin 297 (?) Santa
Monica 50.4 Carpinteria 44.0 Rincon 55.6 Arroyo
Hondo 61.9 ------------------------------------- m
ean (without Franklin) 57 mM/L mean
(including Franklin) 87 mM/L
(From Lydecker data report, 2001)
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Use dilution by freshwater to estimate NO3
concentration Maximum freshwater dilution was
7.6 Seawater initial NO3 1
mM/L Freshwater initial NO3 40, 60 80, 100
mM/L
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Maximum NO3 concentration estimates from storm
event (for freshwater range of 40 to 80
mM/L) 3.8 to 8.3 mM/L at Carpinteria 3.1 to
6.3 mM/L at Naples
Ocean measurements from March 7, 2001
Carpinteria Offshore 1 m - 5.6 mM
5 m - 4.1 10 m - 2.4 Reef 1 m -
5.1 5 m - 3.6 Inshore 1 m -
5.5
Naples Offshore 1 m - 3.0 mM 5 m -
2.2 10 m - 2.1 Reef 1 m - 1.9
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Nearshore currents during storm
m/s E
m/s E
Eastward advection - March 6 to 9.
Arroyo Quemado
Naples
Carpinteria
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Probable upwelling events, April May, 2001.
40-day period
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Winds at West - Channel buoy, 2001
upwelling period
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AVHRR Sea surface temperature images from two of
the April temperature minima
and one from a relatively warm period between
the two cold periods
(data from Dave Siegel)
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Temperature Nitrate relationship from combined
Plumes and Blooms profiles
mM
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A first-guess linear fit - use temperature data
as a proxy for NO3 when direct measurements are
unavailable
Nitrate (nitrate nitrite) mMol/L
Temperature
Data from LTER cruise 1, March 21-26, 2001
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Nitrate estimated for 40-day upwelling period
using the linear temperature - NO3 relationship
from the March, 2001, cruise.
error
(an upper-bound estimate because it does not
include biological uptake)
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Summer relatively high stratification,
diurnal oscillations in temperature and
cross-slope flow
temperature depths 3m, 4 m, 9m, 14m
m/s E
m/s N
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TIDES
Barotropic tides mixed semidiurnal and diurnal
Summer baroclinic tides diurnal signal dominates
1 cpd
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Diurnal Tidal Oscillations temperature
fluctuations vary with depth onshore /
offshore current reversal with depth
Suggested as the major nutrient source for kelp
growth in summer, Catalina Island, (Zimmerman and
Kremer, 1984, Kopczak et al., 1991)
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WARM
Advection back and forth across shelf via
internal tides
COLD
Implications for nutrient delivery?
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Forcing? (frequency lt f (1.13 cpd)) Diurnal
tide Pineda, 1995, possible relationship to
spring/neap cycles Winds Lerczak et al., 2001.
Diurnal winds coupled with changes to relative
vorticity from mesoscale eddies
Wind Spectra
PSD
PSD
cpd
cpd
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December cooling and nitrate-increase event,
likely due to advection from Point Conception
m/s E
m/s N
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Nutrient gradient from west to east along
inner-shelf Dec 5, 2001 Arroyo Quemado,
Naples, and Carpinteria.
A.Q. lon 120.12o, Naples, lon 119.95o,
Carp, lon 119.54o
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Advection of nitrate from West to East
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Comparison of mechanisms for nitrate delivery to
inner-shelf reef depths
NO3 concentration integrated over 10-days
March Storm modeled/observed N
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109
April upwelling N estimated from T
47 (from 9 m) 13 (from 4 m)
July internal tides N estimated from T
December advective event measured N
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October non-event measured N
6
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Conclusions Mooring and monthly sampling
captured the effects of the one runoff event of
2001. Good chance of characterizing storms of
upcoming winters. Useful for modeling el niño
years versus drought years. Influx of nitrate
during low-frequency cooling events, via local
upwelling or from advection of water upwelled
north of Point Conception, is likely the dominant
mechanism for nutrient delivery to the
inner-shelf and kelp reefs. Nitrate delivery
from internal tides may be important when
conditions are nutrient-limited. Summer 2002
deployments of the nutrient auto analyzer may
measure this effect.
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Future Research Diurnal internal waves After
summer 2002 two seasons to compare. -
Investigate relationship to low-frequency
currents and vorticity (CODAR radar data
Washburn), relationship to winds and
stratification. (with C. Cudabeck and L.
Washburn) -Deploy thermistor arrays to measure
alongshore coherence, propagation velocity,
possibility for wave breaking? Local upwelling
events - Relationship to local winds (land and
sea), local wind gradients? Ecosystem
Response - modeling of simple ecosystem (kelp
and phytoplankton nitrate uptake and growth)
response to nitrate pulses at the time-scales
discussed here. - kelp growth rates (at
time scale of 1 month) will be available for
comparison.
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Extras follow
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hoping to work out some vertical and horizontal
tidal excursion stuff to characterize the diurnal
internal waves.
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May 3
March 7
April 4
Salinity
Temperature
June 5
July 3
August 1
Salinity
Temperature
December 5
October 5
November 7
Salinity
Temperature
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Santa Barbara Channel Synoptic States
AVHRR composites from Mark Otero, UCSB
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Address possibility of advection from other side
of the channel (not that it necessarily works
that way, but maybe?) by showing some of the CTD
and nutrient profiles from across the channel
from the LTER cruise 1, March 2001. Higher
nutrients near islands, deeper mixed layers, less
stratified so high nutrients throughout surface
50 meters or so.
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Changes in stratification from Spring to Summer
- Naples
Green reef Blue - offshore
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Change this for talk focus on just one site, and
show a time series of these profiles Through the
months of 2001. Do for nitrate and phosphate.
Nitrate Profiles from Monthly Sampling, 2001
Blue inner, green- reef, red outer.
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Box Model for stream inflow and increase in NO3
concentration

• Use observed salinity change to calculate
  residence time

Salinity change from 32.87 to min of 30.94
ppt Over t 0.91 days. ?? 15.0 days

• - Assumes well-mixed through inner shelf volume
• Depends strongly on C0 (Nitrate concentration
  in stream inflow)

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Box-model solutions for various values of stream
nitrate concentration, Co
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Salinity change (32.9 30.9)/32.9 represents
a 6 dilution of inner-shelf with stream
water Time scale 1 day. (After 1 day, salinity
started increasing). i.e. if N0 were 100 mM, we
would expect ocean concentration to be 6 mM
after 1 day, and this would represent maximum
contribution from storm inflow.
Ocean measurements from March 7, 2001
Carpinteria Offshore 1 m - 5.6 mM
5 m - 4.1 10 m - 2.4 Reef 1 m -
5.1 5 m - 3.6 Inshore 1 m -
5.5
Naples Offshore 1 m - 3.0 mM 5 m -
2.2 10 m - 2.1 Reef 1 m - 1.9