Coastal Lagoons - Chapter 2 docx

Identification of the Lagoon EcosystemsAngheluta Vadineanu CONTENTS 2.1 Introduction2.2 Conceptual Framework of Sustainable Use and Development2.3 Spatio-Temporal Organization of Lagoon

Identification of the Lagoon Ecosystems

Angheluta Vadineanu

CONTENTS

2.1 Introduction2.2 Conceptual Framework of Sustainable Use and Development2.3 Spatio-Temporal Organization of Lagoon Ecosystems2.3.1 Lagoon Ecotone

2.3.2 HGMU Spatio-Temporal Organization2.3.3 Biocoenose’s Spatio-Temporal Organization2.3.4 General Homomorph Model for Lagoons2.4 Scientific Achievements Relevant for Sustainable Management

of Lagoons and Land/Seascapes2.5 Challenges for Ecosystem ModelingReferences

2.1 INTRODUCTION

Lagoon ecosystems are ecotones, or transition units of landscapes and sea/waterscapes

A key aspect of lagoons is highly sensitive areas known as wetlands, the interface areasbetween the land and the water

According to the definition accepted by the Ramsar Convention, wetlands exist

in a wide range of local ecosystems and landscapes or waterscapes distributed overcontinents and at the land/sea interface They are natural, seminatural, and human-dominated ecological systems that altogether cover an average of 6% of the Earth’sland surface.1

Wetlands are diverse in nature They include or are part of areas such as beaches,tidal flats, lagoons, mangroves, swamps, estuaries, floodplains, marshes, fens, andbogs.1,2 The world’s wetlands consist of about three quarters inland wetlands and onequarter coastal wetlands Palustrine and estuarine wetlands, which include lagoons,account for most of them.1

Exponential increase in human population and the corresponding demandfor food and energy resources as well as for space and transport have in the lastcentury stimulated the promotion of economic growth driven by the principles

of neoclassical economy Current philosophy has promoted, and unfortunately

2

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still promotes today, the extensive substitution of natural and seminatural logical systems, or the self-maintained components of Natural Capital (NC),into human-dominated components Consequently, most of the natural and semi-natural components, particularly wetlands, have been seen until recently as

eco-“wastelands.” These areas are being extensively replaced by intensive crop farms,tree plantations, commercial fish culture, harbors, and industrial complexes orhuman settlements.2–6

The lack of scientific background for understanding and estimating the functional role of wetlands associated with the sectoral approach has resulted in lack

multi-of appreciation by policy and decision makers multi-of the resources and services thatthese types of systems have produced

However, these are some of the most productive units in the ecosphere Theyprovide a wide range of self-maintained resources and services, from the viewpoint

of energy and raw materials They replace such self-regulated systems totally or,

to a very great extent, they depend on the input of fossil auxiliary energy andinorganic matter (e.g., chemical fertilizers) as well as on human control mechani-zation (e.g., high-tech equipment for agriculture) Thus the ecological footprint(EF) of many local and national socio-economic systems (SESs) themselves becomehighly dependent on fossil fuels and underperform in providing services The EFbasically tries to assess how much biologically productive area is needed to supplyresources and services, to absorb wastes, and to host the built-up infrastructure ofany particular SES.7

There has been an increase in scientific understanding and awareness among agrowing number of policy and decision makers, especially in recent years Theynow recognize that the structure and metabolism of any sustainable SES should bewell rooted in a diverse, self-maintained, and productive EF This has launched anew philosophy, derived from the theory of systems ecology and ecological eco-nomics, dealing with “sustainable market and sustainable socio-economic develop-ment.” This is an ecosystem approach, and new managerial patterns have emerged,consisting of ecosystem rehabilitation or reconstruction for the improvement of the

EF and conservation through adaptive management of spatio-temporal relationshipsamong SES and the components of NC

In recent years much work has been done to promote these new concepts.Objectives and patterns now focus on reconstruction and management of natural orseminatural ecological components (e.g., wetlands) as major initiatives in the EF ofmany SESs However, principally we are still in the process of conceptual clarifi-cation, strategy, and policy development as well as designing and developing theoperational infrastructure or smaller scale of projects implementation

This chapter presents a comprehensive analysis of the existing concepts, edge, and practical achievements in the integrated or ecosystem approach for sus-tainability or adaptive management of the relationships among SES and the compo-nents of NC It is an attempt to improve the conceptual framework and provide anoperational infrastructure for modeling and sustainable use and development oflagoons, one of the components of the coastal landscape most sensitive and vulnerable

knowl-to human impact This chapter thus provides the overall framework for developmentsdiscussed in the following chapters of the book

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In this respect, this is an attempt to assess and integrate a wide range ofoperational definitions that have been developed and checked in recent years.3–6,8–24

The following were identified as the basic requirements that must be met in order

to put into practice the concept of sustainability

1 Assessment of the conceptual and methodological development of ability that ensures establishment of state-of-the-art definition and identifi-cation of main gaps and shortcomings and, therefore, the need for furtherdevelopment and improvement

sustain-2 Formulation of the basic elements of a dynamic model for co-development

of SES and NC or for sustainable use and development to serve as thebasis for promoting local, regional, and global transition

3 Identification of the advantages and opportunities that each country andregion may have as well as the limits or constraints with which they may

be faced in the designing and implementing of long-term ment” strategies and action plans

“co-develop-4 Identification of existing shortages and gaps in the policy and making process dealing with sustainability and formulation of a compre-hensive and dynamic model for the “decision support systems (DDSs).”This will serve as the interface, or the operational infrastructure, and thusenable us to balance the spatio-temporal relationships and the mass andenergy exchanges between the NC structure, serving as the footprint, andthe SES

decision-What follows is a brief description of the basic conceptual and methodologicalelements to be relied upon in the co-development of SES⇔NC vision of sustainability

as well as the structure of the dynamic DSS that can put sustainability into practice.The concepts and methods dealing with the “environment” have changed andimproved as ecological theory usually described as “biological ecology” has developedfrom its early stage The current ecological theory is more often and more appropriatelydefined as “systems ecology” (Figure 2.1) The identification and description of thenatural, seminatural, human-dominated, and human-created environment has changed

as well This change was from a former conceptual model that defined the environment

as an assemblage of factors—air, water, soil, biota, and human settlements—to theL1686_C02.fm Page 9 Monday, November 1, 2004 3:28 PM

FIGURE 2.1 Growth and evolution of the science of ecology (After Vadineanu, A., Sustainable Development: Theory and Practice,

Bucharest University Press, Bucharest, 1998 With permission.)

The development of theory focused on the concept

of the hierarchical organization of the natural, physical, chemical, and biological environment

as well as on that which humankind dominated and created.

System identification and dynamics of productivity and carrying capacity are the main objectives.

Modeling and systems analysis are the basic tools.

The development of theory was focused

on a concept of ecosystems that recognized the strong relationships between biocoenoses and physical and chemical environments (biotops) The identification of real entities was focused mainly on biocoenoses.

Sectoral and reductionist approach still prevail.

The development of theory was focused on concepts dealing with individuals, cohorts, populations/

species, plant associations, animal associations, and biocoenoses Intra- and inter-specific relationships as well as the relationships between

“organisms and abiotic factors” have been the main tasks.

The identification of real entities was neglected, and the sectoral approach has prevailed.

AUTECOLOGY

SINECOLOGY

STRUCTURE ENERGETICS

BIOGEOCHEMICAL CYCLES

DIVERSITY/

STABILITY

SYSTEMS ECOLOGY

most recent thinking that considers the environment as a “hierarchical spatio-temporalorganization.”6,25–27 (Figure 2.2 and Figure 2.3) Ecological systems, as organized unitsand components of the hierarchy, are described as self-organizing and self-maintainingsystems, or as “life-supporting systems.” They have been described as nonlineardynamic and adaptive systems with evolving production and carrying capacity Thesenonlinear systems go through successive phases of adaptive cycles: growth (R); accu-mulation or maturization (K); release or “creative destruction” (Ω); and restructuringand reorganization (α).28,29

FIGURE 2.2 Relationships between taxonomic and organizational hierarchies of the living systems (A) and their integration within the hierarchy of life-supporting systems or ecological systems (B) A1 = diversity of living organisms and hierarchical order of the taxa established based on the similarity between ordered entities A2 = hierarchical organization of living organisms in large and complex biological systems B = hierarchy of spatio-temporal orga- nization of the upper layer of lithosphere, hydrosphere, troposphere, and biosphere (After Vadineanu, A., Sustainable Development: Theory and Practice, Bucharest University Press, Bucharest, 1998 With permission.)

Ecosphere

Land or Seascapes

Elementary Ecosystems

Biomes

Hierarchy of life-supporting systems

Macroland

or Seascapes

Regional complex

of biocoenoses Biosphere

Biocoenoses

Kingdom Subkingdom Phylum Subphylum Class Subclass Order Suborder Family Subfamily Genus L1686_C02.fm Page 11 Monday, November 1, 2004 3:28 PM

FIGURE 2.3 Hierarchical organization of the natural, human-transformed, and human-created physical, chemical, and biological environment According to existing knowledge concerning the organization of life, we can distinguish five hierarchical levels above biological individuals and four spatio-temporal levels within the ecological hierarchy It must be noted that three- dimensional space of the hierarchical organization integrates upper lithosphere, ocean basins, and troposphere, and the time constants of the ecological systems are in years, decades, centuries,

or millennia (After Vadineanu, A., Sustainable Development: Theory and Practice, Bucharest University Press, Bucharest, 1998 With permission.)

Macroregional assemblage of biocoenoses or BIOMs

Regional complex

of biocoenoses

Regional network

III MACROREGIONAL COMPLEX OF ECOSYSTEMS (Macroland or Seascapes)

EL E MENTARY ECOSYSTEM

IV ECOSPHERE

Hierarchy of Life Systems Hierarchy of Hydrogeomorphological

Units (HGMU) I

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The ecological hierarchy comprises two main hierarchical chains of ecologicalsystems that show a marked and evolving dichotomy in spatio-temporal development:

1 Self-maintained natural and seminatural ecological systems that provide

a wide range of natural resources and services

2 Human-dominated ecological systems that depend to varying degrees oncommercial auxiliary energy and material inflow (e.g., agriculture, aquac-ulture) and human-made systems (e.g., urban ecosystems, industrial com-plexes), which are totally dependent on commercial energy and materialinflow.6,25,27

The divergent dynamics of these systems is the core of the so-called “ecologicalcrisis.” Thus, the ecological hierarchy integrates both the components of the NC andthose of the SES

Accordingly, the term biodiversity in its broad meaning covers, on the one hand,the components of NC together with their taxonomic and genetic diversity and, onthe other hand, human social organization, and ethnic, linguistic, and culturaldiversity

Biodiversity consists of NC and social and cultural capital It provides both the

EF that supports the SES with resources and services and the interface between

NC and the structure and metabolism of the “economic subsystem” (Figure 2.4)

It must be noted that, in order to make the transition from the current status of

a strong dichotomy between SES⇔NC to that of co-development, there is a need

to establish an internal balance between the economic subsystem and social andcultural capital

In the last decade a rapid shift has been observed from the sectoral, reductionistic,and inappropriate temporal (months and years) and spatial scale approach toward aholistic, adaptive, and long-term approach (decades and centuries) Systems analysisand modeling are used more extensively for the identification and description of theecological systems (including SES) as large, complex, dissipative, and dynamicsystems

However, the relationship between humans and nature more recently referred to

as a “development and environmental” relationship or “economy and ecology”should be further reformulated It should be recast as the mediated and dynamicrelationship at local, regional, and global scales between the structure and metabo-lism of SES on one side, and the structure, productivity, and carrying capacity ofthe natural, seminatural, and human-dominated systems (NC) on the other (seeChapter 8 for details)

The following conclusions are set forth:

1 Sustainability deals with co-development or balancing the dynamics ofthe spatio-temporal relationship between SES and NC

2 The principles of free market economy, which negatively limit NC fromcontributing to SES, should be replaced by principles of “sustainablemarket economy.” This will require identification of the overall dynamicframework for co-development, according to the structure, productivity,L1686_C02.fm Page 13 Monday, November 1, 2004 3:28 PM

and carrying capacities of the local, regional, and global NC In addition,ethical and moral criteria for sharing of resources and services within andamong generations and among jurisdictions must be considered

3 There is a need to establish thresholds for the constituent units of the NCand for the spatial relationship between NC and SES Specifically, self-maintained and self-regulated ecological systems should represent morethan 50% of the total NC of a country or region So, the structure andmetabolism of a particular SES should have a high degree of complemen-tarity with the structure, productivity, and carrying capacity of the domesticNC

4 Although we refer to the NC as the EF for a particular SES, wetlands,and in particular lagoons, are a major component in the EF of any SES

FIGURE 2.4 The general physical model of the socio-economic system and its relationships with Natural Capital (NC)

A = the human-made physical capital: I = the infrastructure of the economic subsystem dependent on the renewable resources provided by the components of the NC; II = the industrial infrastructure of the economic subsystem dependent on “non-renewable” resources; III = systems for commercial energy production using fossil and nuclear fuels and hydro-power potential as primary resources; and IV = the human settlements infra- structure 4.1, 4.2, and 4.3 identify the energy flow pathways; B = social capital; C = cultural

components of the NC: 1 = flow of renewable resources; 2 = flow of raw materials; 3 = flow of fossil and nuclear fuels; 4 = flow of electrical energy; 5 = material and energy inputs (fertilization, agrotechnical works, irrigation, selection, etc.) to support the management of human-dominated systems; 6 = dispersion of heat and of secondary products (wastes) in the troposphere and in the HGMU components (After Vadineanu, A., Sustainable Development: Theory and Practice, Bucharest University Press, Bucharest, 1998 With permission.)

4.3 4.1

4.2 3

2

1 6

5

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It might be easier to use terms such as ecological crisis, integrated or ciplinary approach to the environment, or carrying capacity However, it is verydifficult to conceptualize the link between the ecological crisis and the dichotomy

interdis-in the development of NC components and SES The interdis-integrated or systemic approachalso requires an understanding that the physical, chemical, and biological environ-ment has a hierarchical organization that integrates the SES as human-dominatedand human-created ecological systems dependent on mass and energy transfer withthe other components of the hierarchy It also must be understood that the carryingcapacity of NC is linked to stability in a broad sense as well as to the dynamiccapacity of the ecological systems to provide goods and services and to assimilatethe wastes of SES.5,6,11,16

inte-To approach and understand how these systems work and how they can bemanaged as NC, resources and service providers as well as spatio-temporal orga-nization and structure must be identified This structural model that representsthe real world environment by depicting the dynamic components and theirrelationships in time and space is called a homomorph model.30,31 Homomorphmodels are necessary for most scientists and managers to operate in the realworld Development and understanding of homomorph models are necessary forintegrated management and for sustained use of NC that provide support for theSES There have been, and still are, users of basic theoretical principles of thescience of systems ecology who cannot associate these concepts with any realcounterpart Or, even if they do, such a structural model is either very superficial(with inappropriate space scales or oversimplification) or has no true agreementwith the real system

One of the major targets in the field of applied systems ecology is the ment of a specific methodology for ecosystem identification and landscape orsea/waterscape identification.26,31–38

develop-L1686_C02.fm Page 15 Monday, November 1, 2004 3:28 PM

Identification of the lagoons and the land/sea/waterscapes to which they belong

is a step-by-step process that involves:

1 Development and implementation of extensive and intensive research andmonitoring programs, at appropriate time and space scales, consisting offield observations, measurements, and sampling, combined with air pho-tography and remote sensing

2 Analysis of historical information and data

3 Identification of fauna and flora taxa and estimation of biomass, dance, distribution, and dominance, as well as the trophic niche, relation-ship (food webs), production, and demographic structure

abun-4 Assessment and description of the three-dimensional space distribution ofmajor components of the hydrogeomorphic unit (HGMU) and variability

of the lagoons (e.g., water volume, water movement, water retention time,stratification, and water-level oscillation, bottom nature, and chemistry)

5 Identification of lagoon ecotones, boundary conditions, and external ing forces

In summary, all these steps are described in detail in various chapters of thisbook This chapter identifies the crucial need for information systems dealing withthe functioning and dynamics of lagoons in order to carry out sustainable use oradaptative management of lagoon resources and services The remainder of thissection provides a brief summary of information relative to lagoon function, dynam-ics, and management for sustained use and development

The ecotones, or transition zones, are the border areas between the local ecosystems.They are elementary structural and functional units in various types of landscapes andsea/waterscapes The physical, chemical, and biological components of ecotones have

a linear development of tens of kilometers and usually a narrow transversal ment of a few meters or, only very rarely, of hundreds of meters In ecotones the jointHGMUs exhibit a marked discontinuity in at least one constituent (see Chapter 3)

develop-There is a very extensive literature dealing with the role of ecotone components

of lagoons.39–53 Useful conclusions that support managerial purposes are:

• A spatio-temporal organization for biological components allows for theunderstanding of mass and energy exchanges between lagoon systems andsurrounding ecosystems (e.g., agricultural, forests, urban, or marine shelfecosystems) In fact, lagoon ecotones modulate and establish boundaryconditions that are driving forces for the lagoon’s inner structural andfunctional dynamics

• As buffers, wetlands are more sensitive to the antropogenic forces as well

as regional and global climate changes Wetlands and, in fact, lagoon tones are habitats for many vulnerable species, a space for microevolution,

eco-or a space feco-or longitudinal migration

• Due to their structural and functional features, lagoon ecotones shouldreceive special consideration in any strategy and management programL1686_C02.fm Page 16 Monday, November 1, 2004 3:28 PM

for both natural and human-oriented landscape management actionsand should be key sites in the monitoring for climate changes Theecotone component protects lagoons from anthropogenic activities insurrounding areas For example, where farming is intensively practiced

or urban development has occurred within the catchments area, lands provide an effective control of nutrients and other chemicalcompounds or mineral particles from agricultural or urban areas Wet-lands are also the habitats of many efficient predators or pests thataffect crop production Therefore, preservation, restoration, or devel-opment of these lagoon ecotones, particularly the wetland components,

wet-is important for dealing with pollution abatement and/or integrated pestcontrol Likewise, these ecotones are the major habitats of many vul-nerable plant and animal species The management of ecotones should

be designed to reach biodiversity conservation objectives, since versity is clearly indicative of conservation of NC and likely of SESbenefits (see Chapter 8 for details)

Chapter 6 of this book provides strong arguments to support the need for an accuratedescription of the structure and spatio-temporal organization of a lagoon’s HGMU.Such arguments are needed in order to select or develop appropriate hydrodynamicand transport models as a part of the modeling package used for the overall description

of the structure and function dynamics (productivity and carrying capacity) of thelagoon system Based on data concerning water exchange between lagoons and adja-cent seas, the Kjerfve classification system of choked, restricted, and leaky lagoons isproposed (see Chapter 5) Ten morphohydrometric parameters are introduced that,when quantified for a particular lagoon, provide an in-depth understanding of innerphysical and hydrochemical heterogeneity (see Chapter 6, Section 6.3, for details).Time series measurements of morphometric parameters as described in Chapter 7

provide information on changes in the shape and bottom relief of a lagoon HGMUunder the pressure of many external driving forces (e.g., tides, waves, floods, erosion,

or deposition) The complementary relationship between the spatio-temporal zation of a lagoon HGMU and biocoenoses must be stressed again On the one hand,changes in many physical and chemical variables (e.g., salinity, temperature, dissolvedoxygen, nutrient availability, depth, water renewal rate, turbulence, light availability,and bottom structure) describe the dynamic state of HGMUs as inner driving forcesfor component populations and the entire community (e.g., species composition, pop-ulation size, distribution, cost of maintenance, and primary and secondary productiv-ity) On the other hand, the ranges of fluctuations of those variables are usuallymodulated by the activity of biological components (see Chapter 5 for details).The physical, chemical, and biochemical processes widely involved in bio-geochemical cycling of nutrients and chemical compounds in lagoon systems aredescribed in Chapters 3 and 4 These chapters focus on some of the main features

organi-of the processes organi-of energy and mass transfer, which are organi-of great importance forsustainable management

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2.3.3 B IOCOENOSE ’ S S PATIO -T EMPORAL O RGANIZATION

To identify the spatio-temporal organization of a lagoon biocoenose, it is extremelyimportant to give special attention to the intensive and extensive field investigationprocedures employed (see Chapter 7 for details) This includes the sample size,which needs to consider estimation of the component species/population size at anerror rate below 20%; sampling frequency, which should reflect the specific features

of the life cycles of the component species; sampling methods (e.g., transects,random and systematic sampling, mark–recapture); and equipment, in order to iden-tify the heterogeneity inside HGMUs and the mobility and dispersion of individualsand cohorts from different populations.54 The bulk of the data gained by field sampleanalysis should be used to estimate population size, spatial distribution, abundance,biomass, and dispersion through immigration and emigration Populations whosecombined abundance and biomass account for up to 80% and 90%, respectively, arethose populations that play a significant role in the spatio-temporal organization ofthe biocoenose In addition, specific sampling analysis should allow the identification

of trophic spectrum or functional niche, age structure, estimation of production, andbiomass turnover time for each dominant population

If reliable data for the above parameters are available, then the next steps areaggregating the dominant populations into modules according to some effectivecriteria and establishing the network of mass and energy transfer among dominantpopulations from different trophic modules

A critical step in any attempt to identify the biocoenose of a lagoon system isdealing with the identification of the network of trophodynamic modules, whichpreserve structural and functional attributes of the respective biocoenose The solutionshould be a homomorph model This avoids structural oversimplification (e.g., tradi-tional trophic levels and linear pathways connecting them) but accepts loss of struc-tural information (e.g., retain only the dominant populations or cohorts after the firstphase of empirical data analysis and then establish the trophodynamic modulesthrough aggregation of the dominant populations by applying effective procedures)

It is expected that, similar to the real world, the network of trophodynamic modulesthrough which we identify a dynamic and complex biocoenose resembles food websmore than food chains.26,37

The internal structure of a lagoon system (components and the direct and indirectrelationships among them, or so-called network patterns) should be identified inorder to be able to find out reasonable answers to questions such as:

1 What is the relationship between stability, used here with a broader ing than resilience55 of a lagoon ecosystem, and the spatio-temporal orga-nization and dynamic diversity among trophodynamic modules?

mean-2 To what extent does the nature and heterogeneity of an HGMU determinethe internal organization of the biocoenose?

The identity of the network compartments and the nature of spatio-temporalinteraction patterns are crucial for the construction of an adequate homomorph modeland are dependent on the quality of research and monitoring programs (see belowand Chapter 7 for details)

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Typical temporal and spatial scales on which a trophic unit operates and therelationship to the network is the meaning of spatio-temporal organization of the

biocoenose underlying a lagoon HGMU The biocoenose is subject to continuous

change because any unit, like a population or a group of populations, can have only

a finite lifetime and a finite spatial distribution, as described in Chapter 5

The basic unit for the network describing the spatio-temporal organization of alagoon biocoenose is a trophic dynamic module (TDM), first introduced by Pahl-

Wostl.26 The modules are defined for both dynamic and trophic function According

to Pahl-Wostl,26 a trophic dynamic module comprises all populations that have the

same dynamic characteristics and the same functional niche in the trophic web and

that coexist over the same finite period in time and space Thus, having reliable data

and estimates concerning the variables listed earlier for a given biocoenose, we can

identify the homomorph or structural model by applying the following stepwise

3 By taking into consideration the functional characteristics of populations

or cohorts, as expressed by their functional niches (Cik), the dynamic modules are established (MTDikra)

trophic-The following definitions apply:

• Cohort—Embodies a group of individuals that are part of the structure

of a given population that have the same or similar age and share the samefunctional niche

• Dynamic Class (C i)—Includes all populations or cohorts whose biomassturnover time (τ) is in a range where τ remains a constant value on alogarithmic scale

• Dynamic Module (MDikr)—Comprises all dominant populations andcohorts belonging to the same dynamic class (C i) that co-exist within thesame time and space interval

• Trophic–Dynamic Module (MTDikra)—Comprises all dominant tions and cohorts belonging to a dynamic module (MDikr) that have thesame functional niche (Cia)

popula-• Functional Niche (Cia)—Indicates the position occupied by dominantpopulations and cohorts within the trophic connection network, or theirposition within the network as matter and energy carriers Primary pro-ducers (Figure 2.5) are taken as the reference position for establishing theposition within the network of the other functional niches

• i = dynamic class (i = 1,…, n)

k = time interval by units τi

r = space indicated by units S i

a= functional niche

τ = biomass turnover time (B/P)L1686_C02.fm Page 19 Monday, November 1, 2004 3:28 PM

FIGURE 2.5 A potential homomorph model for the identification of lagoon ecosystems DOC = dissolved organic carbon; POC = particulate organic carbon; Pp = primary producers; M1 = bacterioplankton; M2 = benthic micro- organisms; C1= herbivores; C1′′ = microfiltrators (e.g., rotifers, small cladocera); D = detritus-feeding populations;

C2 and C2′′ = zooplanktonic carnivores; C2′ = carnivore invertebrate species; C3′ = benthos-feeding fish species; C3′ = plankton-feeding fish species; C4= predator fish species; S and S ′ = available stock of chemical elements or compounds.

Solar energy input (short wavelengths) Radiation

subsurf ace run-off

surf ace run-off

unidirectional mass and energy transfer

macro- and micro-elements recycling

heat dissipation

Export of concentrated energy and macro- and micro-elements

2.3.4 G ENERAL H OMOMORPH M ODEL FOR L AGOONS

When the identification process of a given lagoon system is completed, the resultshould be a structural and functional model that preserves the basic structural andfunctional attributes of the lagoon and its spatio-temporal relations to other eco-systems from the land–seascape complex to which it belongs (Figures 2.5 and 2.6).Thus, the structural and functional or biophysical model through which a givenlagoon system is identified comprises:

1 The major components in the structure of HGMU and the trophic–dynamicmodules in the structure of biocoenose

2 The most active relationships for mass, energy, and information transferwithin the lagoon itself and between it and surrounding ecosystems(including lower troposphere)

The network and coupled processes are continuously fueled by solar, ical, or auxiliary energy (e.g., wind and tide energy; concentrated energy in

chem-FIGURE 2.6 HGMU’s identification of the lagoon system and its spatial relations with

ecosystems from the land–seascape complex A = agricultural system; E, E1, E2= Ecotones;

E1= hedgerow and E2= riparian vegetation as ecotones; C = lagoon; F = Forest.

Precipitation

Wind erosions

River Sedimentation

Resuspension

Gases exchange Turbulence

E2

E2

E1

nonliving organic matter or fossil energy), and makes the lagoon function as aproductive, self-regulating, and self-maintaining system This involves a perma-nent inner transfer of mass, energy, and information that consists of three overallprocesses:

1 Energy flow

2 Biogeochemical cycling of chemical elements which ends in production

of natural resources and services as well as an entropy dissipation, and

3 Information flows which develop multiple self-regulating mechanismsThe identification process also requires defining the structural and functionalparameters and corresponding vectors by which the state of the lagoon at a given

time ti as well as the set of external driving forces and boundary conditions could bedescribed (see Chapter 3 and Chapter 4 for details) In other words, we may considerthat the homomorph model of a lagoon system is a simplified copy of the real system,developed by ignoring some elementary components and aggregating others A veryimportant fact is that the model should preserve the characteristics of spatio-temporalorganization of the lagoon and its connectivity to the upper hierarchical system, that

is, the land/sea/waterscape

The homomorph model provides the only operational and effective way to copewith the complexity of lagoons when designing and implementing appropriateresearch and monitoring programs Further, a homomorph model is the most pow-erful tool for designing and implementing sustainable management plans

Productivity and self-regulation of a particular lagoon system define its carryingcapacity or potential role in the EF for an SES Lagoons are also dynamic, nonlinearsystems driven by both natural and anthropogenic external forces as well as internalones Usually, at large time scales they exhibit structural and functional changesthat, in turn, lead to changes in their production and carrying capacity Particularreference is made to Chapter 5 for information concerning structural and functionalchanges in lagoon systems in relation to eutrophication, renewal rates, and practicesfor extensive and intensive fisheries management

2.4 SCIENTIFIC ACHIEVEMENTS RELEVANT FOR SUSTAINABLE MANAGEMENT OF LAGOONS AND LAND/SEASCAPES

The last decades of the 20th century were very productive in terms of significantachievements in energetics, biogeochemistry, and ecotoxicology within a widerange of ecological systems Critical analysis and integration of the results thathave been carried out by many ecologists6,32,55–64 prove that natural and seminat-ural ecological systems are resources and service providers to the SES, usually

at their own expense Among the components of the NC, lagoon ecosystems haveproved to be the most productive This is the reason for trying to discriminateand bring to the forefront some fundamental achievements, which may help informulating and implementing strategies and action plans for integrated and

sustainable management of complex land/seascapes, where lagoons are majorcomponents.

• On average, only 0.25% of the solar energy reaching the land and oceansurface and 0.5% of the solar energy absorbed by the primary producersare concentrated in biomass26,54,58 (Figure 2.7a)

• The greatest part of the planet, about 75% of the surface, includingoceans and land, has the lowest efficiency in absorption and concentra-tion of solar energy The density of the energy flow concentrated in thesetypes of ecological systems does not exceed 1000 kcal⋅m−2⋅yr−1, andthis provides only 35% of the ecosphere’s gross primary production(35% of the energy is concentrated by the primary producers of theecosphere)

• The density of the energy flow is concentrated at the level of the primaryproducers from the following natural and semi-natural ecological systems:estuaries and lagoons, coral reefs, wet forests, floodplains, and agriculture.These ecological systems represent only 10% of the total of the ecosphere,but nonetheless the density of energy flow is of the greatest values(10,000–40,000 kcal⋅m−2⋅yr−1) The primary producers of these categories

of ecological systems provide almost 38% of the ecosphere’s gross mary production

pri-• Agriculture covers about 0.8–1% of the total surface of the planet andprovides 5% of the gross primary production of the ecosphere In order

to maintain a concentrated solar energy flow, equal to that of the estuaries,lagoons, wet tropical, and subtropical forests, etc., agriculture requires alarge amount of fossil fuel (up to 1000–2000 kcal⋅m−2⋅yr−1)

• The quantity of energy absorbed and concentrated by the dominant ulations or cohorts in the tropho-dynamic modules, represented by thefirst-order (herbivorous) and by the second- and third-order consumers,decreases from one tropho-dynamic module to another In general, theenergy assimilated (absorbed and concentrated) by a tropho-dynamicmodule made up of heterotrophicspecies represents only 5–20% of theenergy concentrated by the tropho-dynamic module, which is the energysource (Figures 2.7b and c)

pop-This rule explains why the sequence of tropho-dynamic modules directly

or indirectly using the energy concentrated by the primary producers(Figure 2.7a) includes, in any ecological system, only three to four modules.Note also that organic matter (and the potential energy it stores) that is notconsumed or digested by the components of a trophic module, or that isrepresented by intermediary metabolites (containing considerable quantities

of concentrated energy) is transferred into two main reservoirs These aredissolved organic carbon (DOC) and particulate organic carbon (POC).They become, in turn, sources of concentrated energy that support the othertwo series of tropho-dynamic modules which are complementary to the firstone Note that natural and seminatural ecological systems have and developstructures which use “waste” having a concentrated energy content They