Brad deYoung
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Transcript of Brad deYoung
Brad deYoung
Open Pelagic Ecosystems
Roadmap
Ecosystem structure – considerations of the issues and how to think about them
Regime shifts in the ocean – examples of some observed behaviour that we do not quite understand
Variability and modelling of marine ecosystems, some examples
Food web structure, and model structures?
Nutrient Pool
Mass balance models –NPpZzD …
Structured population model
Simplified life history model or data Top down view
more life history driven >> structured models
Bottom up view more process driven – represent metabolism, mass-balance
Challenge : With a target species focus to couple structured models (even if not IBM) and predators and prey below which may have different model structures or data
All models are wrong, but some models are useful. George Box
What criteria do we use to simplify our ecosystem food web? Selection
of target species
A mixture of theory, observation and pragmatism
Functionally important/ecologically significant Extensive data sets (spatial and temporal) Choose a food web in which the first PCA contains
relatively few species Concurrence with other relevant data sets Understanding of life history Widely distributed/across the basin Economic and societal importance Well resolved taxonomy …
Chavez et al. Science (2002)
Modelling can be driven by
data exploration (see right)
process exploration
forecast simulations
Low frequency changes are more important than we once thought
The long-period changes lead to larger spatial scales >> basins
Shifts in physical (temperature, mixed layer depth, …) and biological properties (phytoplankton, zooplankton,…)
Trophic complexity – maintaining fidelity to life history as it becomes more complex and also more difficult to model
Number of state variables
Probable number of species
Top predators
Tro
phic
leve
l
Bacteria
Detail of resolution
Key taxa
Predation
Feeding
ICES - Report of the Study Group on spatial and temporal integration, University of Strathclyde, Glasgow, Scotland, 14-18 June 1993. ICES CM 1993/L:9, (1993).
Functional Complexity
Tro
ph
ic level
Phytoplankton/nutrient focus
Zooplankton/fisheries focus
Physical Ocean
Predators
Life HistoryLife History
Chemistry
WithoutWithoutLife HistoryLife History
deYoung et al. Science. 2004
ZooplanktonFocus
Fish - myctophids, redfish, herring, blue whiting;Zooplankton - gelatinous, euphausiids
Fish - sandlance, capelin, herring, sprat, mackerel, Norway put, blue whiting;Zooplankton - gelatinous, euphausiids
Physics and chemistry – high resolution large scale circulation, coupling between global, basin and shelf models
Food for zooplankton: Microzooplankton, diatoms, non-diatoms, Phaeocystis
Unstructured competitors for structured zooplankton
Zooplankton – Structured population representations of key basin distributed species – variously, particularly congeneric Calanus spp., euphausiids
First Order Horizontal Structure
Top-down predation
Challenge lies in coupling the structured and unstructured models and data
Coupling with the structured components will likely be one-way
Low frequency ‘cycles’ are not likely as linear as they may appear
deYoung et al. Prog. Ocgy. ( 2004), TREE 2008
linear shifts, i.e. nothing special happening
abrupt shifts but reversible in principle
non-linear shifts that are not easily reversible
how linear is the fundamental behaviour that we are trying to represent?
Anderson et al. TREE 2008
DEFINITION OF THE REGIME SHIFT
Working definition : a regime shift is a relatively abrupt change between contrasting persistent states in an ecosystem
Erosion of resilience
Environmental driver
Env
ironm
enta
l sta
teErosion of resilience
Review of a few examples of regime shifts in pelagic
ecosystems• Scotian Shelf – driven primarily by fishing,
cascading trophic impacts• North Sea – combined drivers:
natural=biogeographic shift and human=fishing• North Pacific – complex natural state change(s)
Explore characteristics of the drivers and response of differing examples – time and space scales, trophic structure, predictability
Scotian Shelf – Frank et al. 2005
-30% +30%
Colour display of 60+ indices
for Eastern Scotian Shelf
Red – below average
Green – above average
Grey seals - adults Pelagic fish - #’s
Pelagic:demersal #’s Pelagic:demersal wt. Inverts - $$ Pelagics - wt
Diatoms Grey seals – pups
Pelagics - $$ Greenness
Dinoflagellates Fish diversity – richness 3D Seisimic (km2)
Gulf Stream position Stratification anomaly
Diatom:dinoflagellate Sea level anomaly
Volume of CIL source water Inverts – landings
Bottom water < 3 C Sable winds (Tau)
SST anomaly (satellites) chlorophyll – CPR
Temperature of mixed layer NAO
Bottom T – Emerald basin Copepods – Para/Pseudocal
Shelf-slope front position Storms Bottom T – Misaine bank
Groundfish landings Haddock – length at age 6
Bottom area trawled (>150 GRT) Cod – length at age 6
Average weight of fish Community similarity index
PCB’s in seal blubber Relative F
Pollock – length at age 6 Calanus finmarchicus
Groundfish biomass – RV Pelagics – landings
Silver hake – length at age Condition – KF
Depth of mixed layer Condition – JC
Proportion of area – condition RIVSUM
Sigma-t in mixed layer Oxygen
Wind stress (total) Wind stress (x-direction)
Wind stress amplitude SST at Halifax
Groundfish - $$ Salinity in mixed layer Ice coverage
Wind stress (Tau) Number of oil&gas wells drilled
Nitrate Groundfish fish - #’s
Shannon diversity index –fish Seismic 2D (km)
1970 1975 1980 1985 1990 1995 2000
Grey seals, pelagic fish abundance, invertebrate landings, fish species richness, phytoplankton
Bottom temp., exploitation, groundfish biomass & landings, growth-CHP, avg. fish weight, copepods
Top Predators
(Piscivores)
Forage (fish+inverts)
(Plankti-,Detriti-vores)
Zooplankton
(Herbivores)
Phytoplankton
(Nutrivores)
+
-
+
-Frank et al. 2004/2005 Science et al.
Scotian Shelf – top down story
North Pacific regime shift – Hare and Mantua (2000)
Physical forcing – air temperature - but there are dozens, and dozens of other such time series
The technique of Hare and Mantua has been criticized as being subject to false positives – taking the normalized variance anomalies of many different time series with red spectra can lead to ‘apparent’ shifts
The lack of sufficient clear data is one problem
The time series are too short
The regimes are likely never completely in equilibrium
Many different possible states are likely
Anderson et al. Reviewed the different approaches, and confirm the basic result of Hare and Mantua
North Sea regime shift – a mixture of biogeography, environmental change and fishing
Mean number of calanoid species per CPR sample
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101112
11.522.533.544.55
Years
MONTHS
Line in black: warm-temperate species
Line in red: temperate species
-10 -5 0 5 10
50
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North Sea
France
Mean
num
ber of sp
ecies p
er CP
R sam
ple
Before 1980 After 1980
-0.400.40.8
-2-10123-3-2-10123
-2-1012
Second principal
component (31.36%)
SST (central North Sea)
58 62 66 70 74 78 82 86 90 94 98Years (1958-1999)NHT anomaliesMean umber of species per asse
mblage
-0.4
0
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-2-10123-3-2-10123
-2-1012
Sec
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pri
ncip
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com
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nt (
31.3
6%)
SS
T
(cen
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Nor
th S
ea)
58 62 66 70 74 78 82 86 90 94 98Years (1958-1999)
NH
T a
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ean
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Gadoid species (cod)
SST
NHT anomalies
plankton change-4
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N o m a tc h fo r a n y o f th e c a la n o id c o p e p o d a s se m b la g e s
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Flatfish
salinity
Westerly wind
plankton change
-2.4-2
-1 .6-1.2-0.8-0.4
00 .40.81 .21.6
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C alanoid copepods
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Sta
nd
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F i sh to ta l b iom a ss (5 spe cie s)
Beaugrand & Ibanez (in press, MEPS)
Beaugrand G (2004) Progress in Oceanography
Beaugrand & Ibanez (in press, MEPS)
-2.4-2
-1 .6-1.2-0.8-0.4
00 .40.81 .21.6
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195
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960
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Sta
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evia
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C alanoid copepods
-2-1.6-1.2-0.8-0.4
00.40.81.21.6
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Sta
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F ish tota l b io ma ss (5 spe c ie s)
Beaugrand G (2004) Progress in Oceanography
0%
20%
40%
60%
80%
100%
C. finmarchicus
C. helgolandicus
1962
1964
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1970
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Long-term changes in the abundance of two key species in the North Sea
Per
cen
tage
of
C. h
elgo
lan
dicu
s
Reid et al. (2003)
Consequences of plankton changes on higher trophic level
Mismatch between the timing of calanus prey and larval cod
Abundance of C. finmarchicus
60 65 70 75 80 85 90 95123456789101112
0.20.40.60.81.01.21.41.6 Abundance (in log(x+1))
10
Gadoid Outburst
Abundance of C. helgolandicus
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60 65 70 75 80 85 90 95
0.10.20.30.40.50.60.70.80.91.0 Abundance (in log(x+1))
10
Gadoid Outburst
Beaugrand, et al. (2003) Nature. Vol. 426. 661-664.
0.2
0.4
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1
1960 1970 1980 1990 2000 Year
Propn. of eggs from age 5+ cod
Fishing mortality rate (age 3+)
But there is also a significantinfluence of fishing – howmuch??
50
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pa
wn
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bio
ma
ss
('0
00
T)
1950 1960 1970 1980 1990 2000 Year
Meteorological/oceanographic forcing
Ocean circulation
Biogeographic shift
Ocean conditions
Ecosystem status and function
Fishing
North Sea - dynamics
ICES Report on Ocean Climate 2006. Prepared by the Working Group on Oceanic Hydrography Sarah L. Hughes and N. Penny Holliday, Editors. ICES cooperative research
report no. 289 special issue September 2007 (from Figure 4).
From the NOAA Optimum Interpolation SSTv2 dataset, provided by the NOAA-CIRES Climate Diagnostics Center, USA. The anomaly is calculated with respect to normal conditions for the period 1971–2000. The data are produced on a one-degree grid from a combination of satellite and in situ temperature data. Regions with ice over for >50% of the averaging period are left blank.
Seasonal sea surface temperature anomalies over the North Atlantic for 2006
Expected Result: Major impact for marine exploited resources and biogeo-chemical processes (e.g. sequestration of CO2 by the ocean).
Biological consequences expected under climatic warmingOr changes in water mass structure.
• Changes in the range and spatial distribution of species.
• Shifts in the location of biogeographical boundaries, provinces,
and biomes.
• Change in the phenology of species (e.g. earlier reproductive season).
• Modification in dominance (e.g. a key species can be replaced by
another one).
• Change in diversity.
• Change in other key functional attributes for marine ecosystems.
• Change in structure and dynamics of ecosystem with possible
regime shifts.
Warm-water species have extended their distribution northwards by more than 10° of latitude, while cold-water species have decreased in number and extension.
(Beaugrand, G. ICES Journal of Marine Science, 62: 333-338 (2005)
Long-term changes in the mean number of species per assemblage based on three periods: 1958-1981, 1982-1999, and 2000-2002.
Calanus finmarchicus in the North Atlantic
- open ocean, deep and shallow, spreads out onto shelf, for some species some evidence for genetic separation, copepods key organisms for food web, coupled with circulation
-60 -50 -40 -30 -20 -10 0 1050
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-1800 -1400 -1000 -600 -200
M edian depth (m below sea surface)
Diapause depth – how deep do they go?
Heath et al. (2004)
Calanus in the Labrador Sea
Population achieves maximum growth rate when emergence is 1 month prior to the spring bloom
Timing of population peaks is closely matched observations
Phytoplankton
Temperature
Non-diapausing individuals
Biological model – with a lot of detail on copepod development and growth – in this case the numerical organism eats satellite (SeaWifs) chlorphyll data
The physical model represents the seasonal circulation in the Labrador Sea and the organisms are carried around in it
In the vertical the zooplankton behaviour determines their position
Diapausingindividuals
Tittensor et al. Fish. Ocgy. 2004
Advection Latitudinally
dependent emergence, starting in South (March) and later to the North (May)
only start out in water > 1000m deep (none on the shelf)
results in a peak in the centre of the Labrador Sea
some Calanus move up onto the shelf
Locally sustainable population
January
July November
May
Tittensor et al. Fish. Ocgy. 2004
Model design for the North Atlantic Calanus problem – Heath, Speirs, Gurney et al. (2005)
PhotoperiodLow foodH2
Development at depth
Low foodH1
Entry Exit
Use the model to test different hypotheses of diapause – a process for which we have no direct process model
Surface Copepodites
Diapausers
Newly surfaced overwinterers
No diapausers in spring
Sharp drop at awakening
H1 H1
H3H3
OWS Mike - hypothesis test
Long-term spatial structure and advection through the basin
Year 1
Year 3
Year 6
Speirs et al. Fish. Ocgy. (2005)
Preliminary conclusion is hat biology dominates over circulation
Requires some ‘adjusting’ different parts of the basin
Is able to reproduce the population dynamics at the basin scale – for the first time.
If god had consulted me before embarking on the creation, I would have suggested something simpler. Alfonso of Castile (15th century)