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

58 62 66 70 74 78 82 86 90 94 98123456789

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

55

60

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

0.4

0.8

-2-10123-3-2-10123

-2-1012

Sec

ond

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nt (

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SS

T

(cen

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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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f sp

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e

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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5 8 6 2 6 6 7 0 7 4 7 8 8 2 8 6 9 0 9 4 9 8Ye a r s (1 9 5 8 -1 9 9 9 )

Flatfish

salinity

Westerly wind

plankton change

-2.4-2

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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)

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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

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

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1998

2000

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

123456789101112

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

0.6

0.8

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

100

150

200

250

300 S

pa

wn

ing

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

55

60

65

70

-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)