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2009 | Buch

Ecological Connectivity among Tropical Coastal Ecosystems

herausgegeben von: Ivan Nagelkerken

Verlag: Springer Netherlands

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Über dieses Buch

Mangrove forests, seagrass beds, and coral reefs are circumtropical ecosystems that are highly productive, and provide many important biological functions and economic services. These ecosystems cover large surface areas in the shallow tropical coastal seascape but have suffered from serious human degradation, especially in the last few decades. Part of their diversity, productivity, and functioning seems to be based on their juxtaposition. Especially in the last decade significant advances have been made on new insights into their ecological connectivity. This authoritative book provides a first-time comprehensive review of the major ecological interactions across tropical marine ecosystems that result from the mutual exchange of nutrients, organic matter, fish, and crustaceans. A group of leading authors from around the world reviews the patterns and underlying mechanisms of important biogeochemical and biological linkages among tropical coastal ecosystems in 15 chapters. Included are chapters that review cutting-edge tools to study and quantify these linkages, the importance of such linkages for fisheries, and how tropical ecosystems should be conserved and managed for sustainable use by future generations. The book uses examples from all over the world and provides an up-to-date review of the latest published literature. This book is a ‘must read’ for professionals working on the conservation, management, and ecology of mangrove, seagrass and coral reef ecosystems.

Inhaltsverzeichnis

Frontmatter
Chapter 1. Introduction
Coral reefs, mangrove forests, and seagrass beds are dominant features of tropical coastlines. These tropical coastal ecosystems have long been known for their high productivity, rich biodiversity, and various ecosystem services (Harborne et al. 2006). For example, coral reefs have important economic, biological, and aesthetic values; they generate about $30 billion per year in fishing, tourism, and coastal protection from storms (Stone 2007). The extent of mangroves has frequently been linked to a high productivity in adjacent coastal fisheries (Manson et al. 2005, Meynecke et al. 2008, Aburto-Oropeza et al. 2008) which can approach economic values of up to US$ 16,500 per hectare of mangrove (UNEP 2006). Nutrient cycling of raw materials by seagrass beds has been estimated to value US$ 19,000 ha-1. yr-1 (Constanza et al. 1997).
Ivan Nagelkerken

Part 1: Biogeochemical linkages

Chapter 2. Nitrogen and Phosphorus Exchange Among Tropical Coastal Ecosystems
Abstract
The concentration and flux of nitrogen (N) and phosphorus (P) through mangrove wetlands, seagrass meadows, and coral reef habitats are mediated by a wide range of hydrodynamic and chemical pathways determined by both natural and anthropogenic drivers. The direct proximity of these coastal habitats to burgeoning urban centers makes them quite susceptible to excessive nutrient loading, subsequent land-use impacts, the related effects of eutrophication and of course the associated loss of ecosystem services. For this reason mangrove, seagrass, and coral reef ecosystems are among the most threatened ecosystems in the tropics. While quantifying the exchange of materials between coastal wetlands and nearshore waters has been the focus of estuarine research for nearly half a century, a concerted effort to understand the net exchange of N and P across these habitats has only begun in the last 20 years. Furthermore, attempts to better understand the interplay of N and P cycles specifically between each of these three habitats has been all but nonexistent. The role mangrove and seagrass ecosystems play in buffering nearshore coral habitats from land-based influences remains a topic of great debate. Critical to understanding the nutrient dynamics between these ecosystems is defining the frequency and magnitude of connectivity events that link these systems together both physically and biogeochemically. In this chapter we attempt to address both N and P water column concentrations and system-level exchanges (i.e., water-mediated fluxes and nutrient loading). We consider how the interactions of N and P between these systems vary with geomorphology, hydrography, seasonal programming, and human influences.
Stephen E. Davis, Diego Lirman, Jeffrey R. Wozniak
Chapter 3. Carbon Exchange Among Tropical Coastal Ecosystems
Abstract
Tropical rivers provide about 60% of the global transport of organic and inorganic carbon from continents to the coastal zone. These inputs combine with organic material from productive mangrove forests, seagrass beds, and coral reefs to make tropical coastal ecosystems important components in the global carbon cycle. Carbon exchange has been measured over multiple spatial scales, ranging from the transport and fate of terrestrial organic matter to the coastal zone, export of organic matter to the open ocean, exchange of leaf litter between mangroves and adjacent seagrass beds, to movement of carbon (at a scale of meters) between adjacent saltmarsh and mangrove habitats. Carbon is exchanged directly as particulate or dissolved material, or through migration of animals or through a series of predator-prey interactions known as trophic relay. This chapter first examines riverine carbon inputs to the tropical coastal zone, and how this material is processed in estuaries. The mechanisms and extent of carbon exchange among tropical coastal ecosystems are then discussed, showing their importance in ecosystem carbon budgets, and the implications for faunal and microbial communities.
Steven Bouillon, Rod M. Connolly

Part 2: Ecological linkages

Chapter 4. Dynamics of Reef Fish and Decapod Crustacean Spawning Aggregations: Underlying Mechanisms, Habitat Linkages, and Trophic Interactions
Abstract
Spawning migrations are an important life-history event for many species of commercially important tropical reef fishes and decapod crustaceans. Spawning aggregations are highly predictable events in which hundreds to thousands of individuals migrate across multiple habitats to converge on specific sites for reproduction. Species that undergo spawning migrations provide a potential mechanism to interlink and possibly influence local food webs along their migratory pathways and at aggregation sites. The rapidly declining condition of many aggregating species world-wide emphasizes the urgency with which we need to increase our under-standing of how spawning aggregations function within complex coral reef and other tropical ecosystems. This chapter provides a comprehensive review of reef fish and decapod crustacean spawning aggregations, including mechanisms under-lying their timing and periodicity, characteristics of spawning aggregation sites, and the spatial and temporal patterns of movement and migration. This overview provides the foundation for a discussion of the habitat linkages and potential trophic interactions that occur during migration and spawning, and highlights the existing gaps in our knowledge of how spawning aggregations function and their importance to ecological processes and fisheries sustainability.
Richard S. Nemeth
Chapter 5. The Senses and Environmental Cues Used by Marine Larvae of Fish and Decapod Crustaceans to Find Tropical Coastal Ecosystems
Abstract
Almost all demersal tropical teleost fishes have pelagic larvae that may disperse, in common with most tropical marine decapod larvae. The degree to which behavior and sensory abilities of the larvae influence or control dispersal, and thus the spatial scale of connectivity, is largely unknown, but emerging evidence indicates that this influence is large. Until recently, the established opinion was that the sensory abilities of tropical larval fishes and decapods were mainly irrelevant for the location of the first benthic settlement habitat. However, an increasing number of studies show that pre-settlement coral reef fishes are not only capable swimmers but also show directed swimming in relation to the location of nearby relevant habitat. Many species of tropical decapod larvae and postlarvae also seem capable of detecting environmental habitat cues and may use this ability to move toward a suitable habitat. In this chapter, we review studies on the topics of senses and environmental cues used by marine fish and decapod crustacean larvae to find tropical coastal ecosystems.
Michael Arvedlund, Kathryn Kavanagh
Chapter 6. Mechanisms Affecting Recruitment Patterns of Fish and Decapods in Tropical Coastal Ecosystems
Abstract
The early benthic life history of fishes and decapods in tropical coastal ecosystem can be partitioned into three main stages—settlement, post-settlement transition, post-settlement stage—which culminate in recruitment. Although most species go through these early life history stages, not all species follow the same strategy. Life history strategies occur in three general categories: habitat specialists, habitat generalists, and ontogenetic shifters. Despite this variation in life history strategy, common processes affect the early life history stages of tropical marine fishes and decapods. The life history transition from planktonic larva to benthic post-larva connects oceanic and coastal habitats. However, benthic features and benthic processes affect early life history stages so that settlement and post-settlement distributions are not perfect reflections of larval supply patterns. The abundances and distributions of settlement and post-settlement life history stages result from complex interactions of larval supply, larval behavior, and the interactions of early settlers with the benthic environment. Since much of the very high mortality that occurs during settlement and early post-settlement appears to be due to predation, the direct effects of predators may be the most important factors acting on these early life history stages. Habitat selection, priority effects, predator avoidance, inter- and intra-specific competition, and aggression during and after settlement are also important influences on abundances and distributions of settlement and post-settlement fishes and decapods. The connection between nursery habitat availability and adult population abundances has been demonstrated, so it is likely that these other interactions of early life history stages with the benthic environment have demographic implications that are not yet understood.
Aaron J. Adams, John P. Ebersole
Chapter 7. Habitat Shifts by Decapods—an Example of Connectivity Across Tropical Coastal Ecosystems
Abstract
Decapod life cycles are complex and many utilize a range of habitats throughout their development. Many species tend to settle on shallow (often vegetated) inshore habitats and commonly move offshore into deeper water as they grow. The species that exhibit an inshore/offshore life history are often large individuals and may support commercial fisheries. In this chapter the habitats of a range of tropical decapods are described and likely mechanisms underlying habitat shifts are discussed. It is generally accepted that in most animals these mechanisms are aligned with maximizing the animal’s fitness. Possible mechanisms include minimizing mortality risk (μ), maximizing absolute growth rates (g), or a trade-off in which the animal chooses the habitat that minimizes the ratio of mortality risk to growth rate (minimize μ/g). There do not appear to be any studies that address these issues for tropical decapods and this is identified as an important topic for future research. Similarly, studies that have explicitly demonstrated habitat shifts in tropical decapods are rare; most shifts have been implied by comparing length frequencies in different habitats and it is recommended that future studies consider the use of natural and artificial tags to assist in more accurate characterization of connectivity between coastal habitats.
Michael D.E. Haywood, Robert A. Kenyon
Chapter 8. Diel and Tidal Movements by Fish and Decapods Linking Tropical Coastal Ecosystems
Abstract
Short-term movements of fishes and decapods can lead to regular changes in biomass, diversity, mortality, predation, and flux of energy between adjacent ecosystems. At low latitudes the day-night cycle is relatively stable and uniformly affects activity rhythms of marine organism at all longitudes. In contrast, tidal ranges and tidal types differ significantly between coasts and regions. On coasts with weak tides, twilight migrations connect adjacent habitats. On tidal coasts, migrations are tightly coupled to the interactive effect of the diel and tidal cycles which results in complex but predictable patterns of change within and between ecosystems. Diel and tidal migrations share several similarities (connection of resting and feeding sites, sequence of species and size groups, site fidelity, homing, constant pathways). The spring-neap tide cycle and its interaction with the diel cycle is a key factor influencing regular short-term variations on tidal coasts. The home range of a species on a macrotidal coast may be an order of magnitude greater than that of conspecifics from a microtidal coast, suggesting a need for larger marine parks on macrotidal coasts. Regional comparisons, e.g., between the Caribbean and the Indo-West Pacific, often disregard the significant tidal differences inherent to the ecosystems. It is suggested here that broad-scale comparisons must be redefined; regional comparisons should focus on geographical regions with similar tidal regimes, or on systems with different tidal regimes but with similar species communities.
Uwe Krumme
Chapter 9. Living in Two Worlds: Diadromous Fishes, and Factors Affecting Population Connectivity Between Tropical Rivers and Coasts
Abstract
Among the large range of life history patterns of tropical fishes, about 200 species from 20 fish families undertake diadromous migrations. In most diadromous fish species, only a proportion of the population undertakes migrations and this proportion varies widely between species and families. Three different types of migration are anadromy, catadromy, and amphidromy. Tropical anadromous species are mostly clupeoids, including several shads and herrings. These species spawn in freshwater and migrate to the sea as juveniles, and most of the population matures there before returning to breed in freshwater. Catadromous species have the opposite behavior – they spawn in the sea before migrating to freshwater where they mature. Anguillid eels, mullets, and many centropomids from tropical regions are catadromous. The most common form of diadromy in the tropics is amphidromy. The largest groups of amphidromous fishes are the gobies and gudgeons. Amphidromous fishes spawn in freshwater and the larvae migrate to the sea before migrating back to freshwater, and are common on many islands of all the major oceans. The freshwater and marine components of diadromous fish populations rely on freshwater flows to maintain their connectivity. Most tropical diadromous fishes migrate between habitats during seasonal monsoonal floods. The construction of dams, and shifts in the intensity and reductions in the quantity of rainfall from changing climate are two of the major threats to maintaining connectivity between freshwater and marine populations. The examples of these effects presented here suggest that tropical diadromous fishes will face increasing challenges in maintaining their populations unless greater effort is made to facilitate their migrations.
David A. Milton
Chapter 10. Evaluation of Nursery function of Mangroves and Seagrass beds for Tropical Decapods and Reef fishes: Patterns and Underlying Mechanisms
Abstract
Shallow-water tropical coastal habitats, such as mangroves and seagrass beds, have long been associated with high primary and secondary productivity. The ubiquitous presence of juvenile fish and decapods in these systems has led to the hypothesis that they act as nurseries. Earlier studies mainly focused on the faunal community structure of these systems, leaving us with little detailed insight into their potential role as nurseries. Habitats are considered nurseries if their contribution, in terms of production, to the adult population is greater than the average production of all juvenile habitats, measured by the factors density, growth, survival, and/or movement. High food abundance and low predation risk form the most likely factors that contribute to the attractiveness of tropical nursery habitats. Here, the current state of knowledge on nursery function of shallow-water coastal habitats, particularly mangroves and seagrass beds, is reviewed for each of the above-mentioned factors. Most data show that mangroves and/or seagrass beds have high densities of various fish species and some of their food items, and a lower predation risk for fish and decapods due to factors such as low predator abundance, high water turbidity, and complex habitat structure. In contrast, growth rates of fish appear higher on coral reefs. There is increasing evidence that at least part of the fish or decapod population in these putative nurseries eventually moves away to offshore habitats. The current review shows that mangrove and/or seagrass habitats may act as nurseries through higher juvenile densities and survival rates than offshore habitats, but that trade-offs may exist to the detriment of growth rate. With the lack of detailed movement studies, the exact degree to which mangroves and seagrass beds sustain offshore fish and decapod populations remains largely unclear.
Ivan Nagelkerken
Chapter 11. Sources of Variation that Affect Perceived Nursery Function of Mangroves
Abstract
Mangroves are considered among the most productive ecosystems on the planet. While mangroves provide numerous critical ecosystem services to surrounding environments, there is particular interest in the role of mangroves as nursery habitats for fish and decapods. Despite this interest, scientific consensus regarding the role of mangroves as nurseries remains elusive. In this chapter, we identify four principal sources of variability that underlie conflicting conclusions regarding the function of mangroves as nursery habitat. We provide brief sketches of the reasons why these sources of variability may affect the role of mangroves as nursery habitat, drawing particularly on recent empirical advances in the field, and conclude with a conceptual model summarizing the different levels at which the nursery function of mangroves is evaluated.
‘It is time that we biologists accept diversity and variability for what they are, two of the essential features of the biological world. We would be wise to restructure our search for orderly patterns in the natural world. We should stop thinking primarily in terms of central tendencies … .Variation among and within species is fundamental to organisms. Analysis of variation can offer insights just as surely as can traditional delineation of central tendencies.’ (Bartholomew .
Craig H. Faunce, Craig A. Layman

Part 3: Tools for studying ecological and biogeochemical linkages

Chapter 12. Tools for Studying Biogeochemical Connectivity Among Tropical Coastal Ecosystems
Abstract
To understand ecosystem functioning in coastal zones it is essential to identify the main pathways and magnitude of nutrient and organic matter fluxes. The different methods that have been applied to quantify material fluxes in tropical coastal ecosystems can be categorized into two fundamentally distinct approaches: direct flux measurements (Section 12.2) and chemical tracer techniques (Section 12.3). For direct flux measurements, the bidirectional flow of water is determined and multiplied with concentrations to obtain fluxes of inorganic nutrients or organic constituents. Water discharge can be measured directly with help of current meters and gauges, or indirectly through use of water tracers. The source of nutrients and organic matter can then be identified with help of specific chemical tracers, mainly isotopes or molecular properties. A combination of tracer techniques and direct flux measurements is most powerful to obtain quantitative information on the fluxes of organic matter and nutrients from the various sources in coastal systems but has very rarely been applied. Regarding source assessments of suspended and sedimentary organic matter, a large number of molecular biomarkers are readily available (Section 12.4). For dissolved organic matter, emerging molecular fingerprinting techniques including ultra-high resolution mass spectrometry may lead to major advances in the future.
Thorsten Dittmar, Boris Koch, Rudolf Jaffé
Chapter 13. Tools for Studying Biological Marine Ecosystem Interactions—Natural and Artificial Tags
Abstract
Determining connectivity of organisms is difficult especially for early life history stages (larvae and juveniles). Fortunately, a variety of natural and artificial tags, some of which date back to the 1600’s, have been developed to help address the issues of movement. Over the years a vast literature on tagging has emerged, of which I provide an updated review. In this chapter, I discuss five broad areas of tagging (external tags, external marks, internal tags, telemetry, and natural tags) and provide additional information on genetic and chemical methods. For each method I highlight their advantages and disadvantages, and provide examples, where possible, of connectivity among tropical coastal ecosystems. Advances in many of the methodologies are expected to continue, and future studies should consider combining more than one approach especially where natural tags are utilized.
Bronwyn M. Gillanders
Chapter 14. A Landscape Ecology Approach for the Study of Ecological Connectivity Across Tropical Marine Seascapes
Abstract
Connectivity across the seascape is expected to have profound consequences for the behavior, growth, survival, and spatial distribution of marine species. A landscape ecology approach offers great utility for studying ecological connectivity in tropical marine seascapes. Landscape ecology provides a well developed conceptual and operational framework for addressing complex multi-scale questions regarding the influence of spatial patterning on ecological processes. Landscape ecology can provide quantitative and spatially explicit information at scales relevant to resource management decision making. It will allow us to begin asking key questions such as ‘how much habitat to protect?’, ‘What type of habitat to protect?’, and ‘Which seascape patterns provide optimal, suboptimal, or dysfunctional connectivity for mobile marine organisms?’. While landscape ecology is increasingly being applied to tropical marine seascapes, few studies have dealt explicitly with the issue of connectivity. Herein, we examine the application of landscape ecology to better understand ecological connectivity in tropical marine ecosystems by: (1) reviewing landscape ecology concepts, (2) discussing the landscape ecology methods and tools available for evaluating connectivity, (3) examining data needs and obstacles, (4) reviewing lessons learned from terrestrial landscape ecology and from coral reef ecology studies, and (5) discussing the implications of ecological connectivity for resource management. Several recent studies conducted in coral reef ecosystems demonstrate the powerful utility of landscape ecology approaches for improving our understanding of ecological connectivity and applying results to make more informed decisions for conservation planning.
Rikki Grober-Dunsmore, Simon J. Pittman, Chris Caldow, Matthew S. Kendall, Thomas K. Frazer

Part 4: Management and socio-economic implications

Chapter 15. Relationships Between Tropical Coastal Habitats and (offshore) Fisheries
Abstract
The economic welfare and productivity of many tropical fisheries, inshore or offshore, depends on the integrity of coastal habitats, particularly mangroves and coral reefs. Fisheries within coastal systems in developing countries are usually artisanal or subsistence in nature, whereas offshore fisheries are usually commercial or industrial. Relationships between fisheries production and areas of mangrove have been quantified, notably for penaeid prawns, but in most cases the causal links have not been established. Nevertheless, evidence of the value of mangroves to fisheries continues to mount and the importance of the relationship has gained widespread acceptance. Coral reef fisheries are largely the domain of small-scale fishers, but their relative importance is very great with global catches in excess of 2 × 106 tonnes. Their fisheries productivity is less than that of estuarine and coastal waters. The connectivity between reef fisheries and mangroves and seagrasses, and connectivity between reefs are relevant to offshore fisheries. Coral reefs support some pelagic fisheries, such the pole-and-line tuna fleets in the Pacific and Indian Oceans. For most tropical fisheries, the key issue is the depleted state of the resources, e.g., for most tropical Asian countries biomass has declined to <10% of baseline estimates. The major contributor to this is overfishing linked to poverty among fishing communities—symptoms of lack of effective management. Strategies to address the situation relate to ecological connectivity and dependence on mangroves or coral reefs, the balance between small-scale and industrial fisheries, and scales of management as well as use of Marine Protected Areas (MPAs).
Stephen J. M. Blaber
Chapter 16. Conservation and Management of Tropical Coastal Ecosystems
Abstract
All major coastal ecosystems in the tropics are being degraded. The problems include losses of biodiversity, reduced ecosystem functions, and costs to coastal human societies. Declines in species’ abundances, and habitat loss and modification are the result of the demands for aquaculture, port construction, trawling, excessive nutrient loads, overfishing and collecting, sedimentation from catchment activities, invasive species, and climate change. A global response to these changes has been conservation and management approaches that aim to reduce, reverse, and prevent unnatural changes and address their underlying causes. Successes in conservation and management are likely when actions are designed to achieve the fundamental ecological goals of ensuring resilience, maintaining ecosystem connectivity, protecting water quality, conserving species-at-risk, conserving representative samples of species and assemblages, and managing at the appropriate spatial scale. Achieving societal aspirations for coastal ecosystems requires that management approaches address the socio-economic aspects of issues and include stakeholder consultation, participation, and education. Achieving long-term success in conservation and management requires coastal nations to address fundamental issues such as lack of information for management decision-making, population growth and poverty, limited technical and management capacity, poor governance, lack of stakeholder participation, the mismatches between the issue and the geographic scale of management, lack of an ecosystem perspective, ineffective governance and management, and a lack of awareness of the effects of human activities.
William Gladstone
Backmatter
Metadaten
Titel
Ecological Connectivity among Tropical Coastal Ecosystems
herausgegeben von
Ivan Nagelkerken
Copyright-Jahr
2009
Verlag
Springer Netherlands
Electronic ISBN
978-90-481-2406-0
Print ISBN
978-90-481-2405-3
DOI
https://doi.org/10.1007/978-90-481-2406-0