Open Pelagic Ecosystems
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Open Pelagic Ecosystems. Brad deYoung. 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.

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Roadmap
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



Top down view more life history driven >> structured models

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

Bottom up view more process driven – represent metabolism, mass-balance

Simplified life history model or data

Structured population model

All models are wrong, but some models are useful.George Box

Mass balance models –NPpZzD …

Nutrient Pool


What criteria do we use to simplify our ecosystem food web? Selection of target speciesA 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


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,…)

Chavez et al. Science (2002)


Predation Selection of target species

Key taxa

Feeding

Number of state

variables

Detail of resolution

Trophic complexity –maintaining fidelity to life history as it becomes more complex and also more difficult to model

Top predators

Trophic level

Bacteria

Probable number

of species

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).


Physical Ocean Selection of target species

Zooplankton/fisheries focus

Predators

Life History

Trophic level

Without

Life History

Phytoplankton/nutrient focus

Chemistry

Functional Complexity

deYoung et al. Science. 2004


Top-down predation Selection of target species

Challenge lies in coupling the structured and unstructured models and data

Coupling with the structured components will likely be one-way

Zooplankton

Focus

Open Ocean

Shelf

Planktivorous

Predators

Fish - sandlance, capelin, herring, sprat, mackerel, Norway put, blue whiting;

Zooplankton - gelatinous, euphausiids

Fish - myctophids, redfish, herring, blue whiting;

Zooplankton - gelatinous, euphausiids

Zooplankton – Structured population representations of key basin distributed species – variously, particularly congeneric Calanus spp., euphausiids

Unstructured competitors for structured zooplankton

Food for zooplankton: Microzooplankton, diatoms, non-diatoms, Phaeocystis

Physics and chemistry – high resolution large scale circulation, coupling between global, basin and shelf models

First Order Horizontal Structure


Low frequency ‘cycles’ are not likely as linear as they may appear

  • 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

deYoung et al. Prog. Ocgy. ( 2004), TREE 2008


DEFINITION OF THE REGIME SHIFT may appear

Working definition : a regime shift is a relatively abrupt change between contrasting persistent states in an ecosystem


Erosion of resilience may appear

Environmental state

Erosion of resilience

Environmental driver


Review of a few examples of regime shifts in pelagic ecosystems
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


-30% +30% ecosystems

Scotian Shelf – Frank et al. 2005


Colour display of 60 indices for eastern scotian shelf
Colour display of 60+ indices ecosystemsfor Eastern Scotian Shelf

Grey seals, pelagic fish abundance, invertebrate landings, fish species richness, phytoplankton

Grey seals - adults Pelagic fish - #’s Pelagic:demersal #’s Pelagic:demersal wt. Inverts - $$Pelagics - wtDiatoms Grey seals – pups Pelagics - $$ 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)

Red – below average

Green – above average

Bottom temp., exploitation, groundfish biomass & landings, growth-CHP, avg. fish weight, copepods

1970 1975 1980 1985 1990 1995 2000


Scotian Shelf – top down story ecosystems

Top Predators

(Piscivores)

+

Forage (fish+inverts)

(Plankti-,Detriti-vores)

-

Zooplankton

(Herbivores)

+

Phytoplankton

(Nutrivores)

-

Frank et al. 2004/2005 Science et al.




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 being subject to false positives – taking the normalized variance anomalies of many different time series with red spectra can lead to ‘apparent’ shifts

biogeography, environmental change and fishing

Line in black: warm-temperate species

Line in red: temperate species

12

5

11

4.5

M

O

N

T

H

S

10

4

9

8

3.5

7

3

6

2.5

5

2

4

1.5

3

2

1

1

58

62

66

70

74

78

82

86

90

94

98

Years

Mean number of calanoid

species per CPR sample

Before 1980

After 1980


Gadoid species (cod) being subject to false positives – taking the normalized variance anomalies of many different time series with red spectra can lead to ‘apparent’ shifts

Flatfish

plankton change

plankton change

salinity

SST

NHT anomalies

Westerly wind


Beaugrand & Ibanez (in press, MEPS) being subject to false positives – taking the normalized variance anomalies of many different time series with red spectra can lead to ‘apparent’ shifts

Beaugrand G (2004) Progress in Oceanography


Beaugrand & Ibanez (in press, MEPS) being subject to false positives – taking the normalized variance anomalies of many different time series with red spectra can lead to ‘apparent’ shifts

Beaugrand G (2004) Progress in Oceanography


Long-term changes in the abundance being subject to false positives – taking the normalized variance anomalies of many different time series with red spectra can lead to ‘apparent’ shifts

of two key species in the North Sea

Percentage of

C. helgolandicus

Reid et al. (2003)


Consequences of plankton changes on higher trophic level being subject to false positives – taking the normalized variance anomalies of many different time series with red spectra can lead to ‘apparent’ shifts

Abundance of C. finmarchicus

Abundance of C. helgolandicus

Mismatch between the timing of calanus prey and larval cod

Beaugrand, et al. (2003) Nature. Vol. 426. 661-664.


But there is also a significant being subject to false positives – taking the normalized variance anomalies of many different time series with red spectra can lead to ‘apparent’ shifts

influence of fishing – how

much??


North Sea - dynamics being subject to false positives – taking the normalized variance anomalies of many different time series with red spectra can lead to ‘apparent’ shifts

Ocean circulation

Biogeographic shift

Meteorological/oceanographic

forcing

Fishing

Ecosystem status

and function

Ocean conditions


Seasonal sea surface temperature anomalies over the North Atlantic for 2006

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.

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).


Biological consequences expected under climatic warming Atlantic for 2006

Or 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.

Expected Result: Major impact for marine exploited resources and biogeo-

chemical processes (e.g. sequestration of CO2 by the ocean).


Long-term changes in the mean number of species per assemblage based on three periods: 1958-1981, 1982-1999, and 2000-2002.

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)


Calanus finmarchicus assemblage based on three periods: 1958-1981, 1982-1999, and 2000-2002. 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


Diapause depth – how deep do they go? assemblage based on three periods: 1958-1981, 1982-1999, and 2000-2002.

Heath et al. (2004)


Calanus in the labrador sea
Calanus assemblage based on three periods: 1958-1981, 1982-1999, and 2000-2002.in the Labrador Sea

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

Non-diapausing

individuals

  • Population achieves maximum growth rate when emergence is 1 month prior to the spring bloom

  • Timing of population peaks is closely matched observations

Diapausing

individuals

Phytoplankton

Temperature

Tittensor et al. Fish. Ocgy. 2004


May assemblage based on three periods: 1958-1981, 1982-1999, and 2000-2002.

January

July

November

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

Tittensor et al. Fish. Ocgy. 2004


Model design for the north atlantic calanus problem heath speirs gurney et al 2005
Model design for the North Atlantic assemblage based on three periods: 1958-1981, 1982-1999, and 2000-2002.Calanus problem – Heath, Speirs, Gurney et al. (2005)


Entry assemblage based on three periods: 1958-1981, 1982-1999, and 2000-2002.

Exit

H1

Low food

Development at depth

H2

Low food

Photoperiod

Use the model to test different hypotheses of diapause – a process for which we have no direct process model


Ows mike hypothesis test
OWS Mike - hypothesis test assemblage based on three periods: 1958-1981, 1982-1999, and 2000-2002.

Surface Copepodites

Diapausers

H1

H1

H3

H3

Newly surfaced overwinterers

Sharp drop at awakening

No diapausers in spring


Long term spatial structure and advection through the basin
Long-term spatial structure and advection through the basin assemblage based on three periods: 1958-1981, 1982-1999, and 2000-2002.

  • 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.

Year 1

Year 3

Year 6

Speirs et al. Fish. Ocgy. (2005)


If god had consulted me before embarking on the creation, I would have suggested something simpler.

Alfonso of Castile (15th century)


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