UNDERSTANDING ECOSYSTEM COMPLEXITY –
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UNDERSTANDING ECOSYSTEM COMPLEXITY – BASIC PREREQUISITE FOR THE SUSTAINABLE DEVELOPMENT OF THE NW BLACK SEA. Prof. Marian-Traian GOMOIU GeoEcoMar - Constantza, Romania, E-mail: [email protected] Basic Principles and New Approaches on the NW Black Sea Ecosystems State Assessment :.

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UNDERSTANDING ECOSYSTEM COMPLEXITY – BASIC PREREQUISITE FOR THE SUSTAINABLE DEVELOPMENT OF THE NW BLACK SEA

Prof. Marian-Traian GOMOIU

GeoEcoMar - Constantza, Romania, E-mail:[email protected]


Basic Principles and New Approaches on the

NW Black Sea Ecosystems StateAssessment :

  • applying the integrative, holistic approach to the knowledge and management of the NW Black Sea ecosystem;

  • benthic ecosystems as barometer of the ecological health state of the sea, which generates resources and services for socio-economic systems;

  • emerging role of marine geology in benthic ecology;

  • developing basic ecological concepts – complexity of ecosystems, resilience, vulnerability, disturbance, integrality of natural systems and socio-economic systems etc. in order to improve knowledge and management of the Black Sea;

  • understanding of the Black Sea biodiversity process and building human resources in the field.


Current adaptive management targets for the Black Sea and Danube Basin (Mee 2001)

Long term objective (EcoQO): “to take measures to reduce the loads of nutrients and hazardous substances discharged to such levels necessary to permit Black Sea ecosystems to recover to conditions similar to those observed in the 1960s”

First operational target: “urgent measures should be taken in the wider Black Sea Basin in order to avoid that the loads of nutrients and hazardous substances discharged into the Seas exceed those that existed in the mid 1990s (these discharges are only incompletely known)”


Conceptual framework for the integrated Program Impact, Disturbance, Resilience and Rehabilitation on the

Black Sea Biodiversity and Health of Ecosystems

Conceptual framework for the integrated Program Impact,

Disturbance, Resilience and Rehabilitation on the

Black Sea Biodiversity and Health of Ecosystems


Sources/ Disturbance, Resilience and Rehabilitation on the types of complexity :

Spatial- visible in the forms of vegetation patterns and species distributions our ability to describe or quantify spatial pattern is poor

Temporal- arises from population dynamics, effects of fluctuating climate and weather, and from spatial complexity (include metapopulation dynamics, temporal population fluctuations, extinctions, invasions, succession, predator-prey cycles, etc.)

Structural- relationships within an ecosystem (include food web structure, community composition, networks of competition, and facilitation, etc.)

Ecosystem complexity


Sources/ Disturbance, Resilience and Rehabilitation on the types of complexity :

Process- many steps or components (soil formation, the decay of logs, and succession; during the decay of a log many organisms physically alter the log in a sequential manner over a prolonged period; succession involves facilitation, competition, immigration, changes in physical conditions (e.g., development of a litter layer), and even changes in the local climate. Piecing together the entire process is rarely easy in such cases.

Geometric- geometric aspects of ecological objects add considerable complexity to systems. An obvious example is a forest canopy or individual tree crown.

Ecosystem complexity


Sources types of complexity
Sources/ Disturbance, Resilience and Rehabilitation on the types of complexity :

Behavioral - often-overlooked aspect of overall ecosystem complexity; in contrast to the building blocks of physics, such as ideal gases and identical protons, living organisms exhibit behaviors based on the information contained in their DNA. Plants adapt their growth form to extant conditions. Animals become more adept at catching prey as they gain experience. In a few cases, models have tried to incorporate movement decisions or foraging behaviors into animal home range models, as well as in a few other contexts.

Ecosystem complexity


Ecosystem stress response can be described by using some simple notions such as
Ecosystem stress response Disturbance, Resilience and Rehabilitation on the Can be described by using some simple notions such as:

  • Stability - the degree of oscillation, the system exhibits, about its stable equilibrium pointand

  • Resiliency -minimum distance from the equilibrium point to the edge of the cloud, is measured by the minimum disturbance necessary to disrupt the system and cause it to move to a new equilibrium state.

  • Integrityof asystem refers to our sense of it as a whole. If a system is able to maintain its organization in the face of changing environmental conditions then it is said to have integrity. If a system is unable to maintain its organization than it has lost its integrity.


Ecosystem stress response Disturbance, Resilience and Rehabilitation on the

  • Change in Organization refers to changes in the function of a system and its internal connections (structure) so as to better carry out some organizational imperative. Environment refers to the biotic and abiotic components external to an ecosystem which impact upon it, including humans.)

  • Stress-response must be characterized by a richer set of concepts and the concept of integrity must be seen as multi-dimensional and encompassing a rich set of ecosystem behaviours (Kay, 1991) .


Properties of ecosystems determining stress recovery characteristics cairns and dickson 1977
Properties of ecosystems Disturbance, Resilience and Rehabilitation on the determining stress recovery characteristics(Cairns and Dickson 1977)

  • VULNERABILITY - lack of ability to resist irreversible damage (which requires a recovery time greater than a human life span); could be measured by the size of disturbance necessary to cause irreversible damage;

  • ELASTICITY - ability to recover after displacement of structure and/or function to a steady state closely approximating the original; could be measured by the rate of recovery after disturbance;

  • INERTIA - ability of an ecosystem to resist displacement or disequilibrium in regards to either structure or function; could be measured by the size of the disturbance needed to displace the system;


Properties of ecosystems Disturbance, Resilience and Rehabilitation on the determining stress recovery characteristics

  • RESILIENCY (Holling, 1973) - number of times a system can undergo the same disturbance and still snap back; Syn.: AMPLITUDE - area over which the system is stable (the same as Holling's resilience). Resilience - the minimum distance from the equilibrium point to the edge of the cloud; thus resilience is measured by the minimum disturbance necessary to disrupt the system and cause it to move to a new equilibrium state.


Stability - the degree of oscillation, the system exhibits, about its stable equilibrium point.

Although the Black Sea before the ’60s experienced extreme oscillations in some populations, the system almost always bounces back to its original state. It was resilient. Holling notes that resilient systems normally aren't stable and vice versa.

  • There are two kinds of stability involved (Hill, 1975) :

  • "no-oscillation" stability - refers to the stability of the state variables in the absence of stress;

  • "stability-resilience" - refers to the stability of the state variables while the system is under stress and after the stress is removed; this stability refers to the degree of oscillation (flutter) the system experiences while under stress and how quickly this is dampened out when the stress is removed.


Orians (1975) has identified seven properties of ecosystems which are related to their stability:

CONSTANCY - the lack of change in some parameter of the system;

PERSISTENCE - the survival time of the system;

INERTIA - the ability to resist external perturbations;

ELASTICITY - the rate at which the system returns to its former state following a perturbation;

AMPLITUDE - the area over which the system is stable (the same as Holling's resilience);

CYCLICAL STABILITY - the property of a system to cycle about some central point or zone;

TRAJECTORY STABILITY - the property of a system to move towards some final end point or zone despite differences in the starting points.


Human activities impact and pressures: which are related to their stability:


Human activities impact and pressures: which are related to their stability:


Ecosystem States: which are related to their stability:


Ecological changes: which are related to their stability:

·the changes may be short term with the environment returning to its previous condition, or

·the change may persist.

What immediate effect will this have on the ecosystem's organization and hence its integrity? A series of questions must be asked:

1. Will the system be moved away from its optimum operating point?

· If the response is no, then organization and integrity are not immediately affected.

· If the response is yes, then the question becomes:

2. Does the system return to its original optimum operating point?

If the answer is yes, then there are three issues:

·How far is the system moved from its optimum operating point before returning?

· How long will it take to return to its optimum operating point?

· What is the stability of the system upon its return?


Certainly we know many ecological disturbances and change occurring in the Black Sea environment

Nevertheless, let’s hope the ecological pressure will decrease simultaneously with the diminishing fertilizers and other chemicals used in agriculture or with the reduction of the fishing effort. But this is far from being all. There are also the manipulations of the hydrologic regime of Black Sea tributaries. There are also the large-scale variations. There are the global changes. There are so many steps to establish, to know, without which it is hard to predict the Black Sea evolution.


  • A occurring in the Black Sea environment- in a benign environment with low probabiliry of catastrophic perturbations;

Trajectory of ecologicol succession

  • B – in stressful environment subject to periodic perturbations that disruptand send back the developmental process; In situarion B, two hypothetical ser-bock loops ore shown following disrurbances indicated by the arrows; the biotic community becomes adaptively perturbarion-dependent by moinroining a lower level of organization that would be achieved in rhe absence of stress input.


Ecological changes: occurring in the Black Sea environment


Ecological changes: occurring in the Black Sea environment




Evolution of nutrient loads in danube water
Evolution of nutrient loads in Danube water Black Sea Coast

Ecological changes:


Evolution of nutrient loads in Danube water Black Sea Coast

Ecological changes:


A series of questions must be asked: Black Sea Coast

1. Will the system be moved away from its optimum operating point?

· If the response is no, then organization and integrity are not immediately affected.

· If the response is yes, then the question becomes:

2. Does the system return to its original optimum operating point?

If the answer is yes, then there are three issues:

· How far is the system moved from its optimum operating point before returning?

· How long will it take to return to its optimum operating point?

· What is the stability of the system upon its return?


After the Black Sea ecological crisis was confirmed worldwide, studied and managed equally by the scientific community, political factors and civil society, and numerous publications appeared as a final proof, today specialists think that the ecosystem ecological state witnesses a slight recovery.

May we speak of a gradual recovery of the Black Sea? Do we witness an improvement of the ecological situation of this sea? A betterment of the planktonic and benthic ecosystems? A redressing of the fishing resources? Is the economic decline of the riparian countries really saving the Black Sea?


Stopping the flow of littoral currents of Danubian sediments worldwide, studied and managed equally by the scientific community, political factors and civil society, and numerous publications appeared as a final proof, today specialists think that

Ecological changes

of habitats

and biodiversity

Deviating offshore

the southward littoral drift of sediments

Disappearance of Ophelia – Mesodesma biocoenoses

Reduction in the populations of calciferic species forming sediments

C

O

N

E

X

A

CT

I

V

I

T

I

E

S

Sand exploitation

Deficit of the sedimentary balance of touristic beaches

Removing the shell deposits from the beach

Disappearance of algal populations attenuating erosion energy

Artificial sand deposits

Beach erosion

Withdrawal of the shore line with 15 - 70 m between

1979 - 1997

Emergency hydrotechnical works, without scientific basis

Movement of erosion field towards

neighbouring zones

Impact of building harbours on the marine ecosystems - Romanian Black Sea Coast

Building harbour breakwaters

Midia, Constanţa Sud - Agigea and Mangalia



Main ecological chain changes triggered Danube River

by the development of maritime transport


CONCLUSIONS Danube River

Slight recovery of the NW Black Sea ecosystems:

  • Biodiversity, with a little higher number of species is slightly better than in the last decades, 272 taxa (250 spcies and 22 supra-specific taxa – Nematoda and Nemertini worms, Harpacticoida crustacians, Bryozoa, Chironomida etc.).

  • Abundance of benthic populations is regular towards better, the general average values for the NW Black Sea, 0 – 125 m being 159,000 indvs.m-2for numerical density and 470 g.m-2 for biomass.

  • There is a large variation of the abundance of benthic populations from one station to another, but the average values of the three continental shelves (Ukraine, Romania, Bulgaria) are similar: 9246 - 12660 indvs.m-2 and 462.14 - 465.2 g.m-2 for macrobenthos and 149795 - 164376 indvs.m-2 and 5.6 - 20.9 g.m-2 for meiobenthos.


CONCLUSIONS Danube River

  • The occurrence of some recurrent species, considered almost extinct 2-3 decades ago, represents a positive event, promising for the future recovery of the ecosystem.

  • Benthos populations have a random distribution, in patches, being characterized by occurrence of some meta-populations.

  • The existence of two-year old mussels in this area is also promising and contrasts with the situation in the late 1980s where all new recruits were killed by the annual appearance of the dead zone.

The recovery of the benthic system is rather weak. There are still uncertainties and it is too early to draw a high confidence conclusion on the recovery, the evaluation of the Black Sea ecosystem state represents a complex, laborious, time consuming and rather imprecise process for the moment.


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