Ivan Valiela

Bio: Ivan Valiela is an academic researcher from Marine Biological Laboratory. The author has contributed to research in topics: Salt marsh & Eutrophication. The author has an hindex of 73, co-authored 272 publications receiving 21141 citations. Previous affiliations of Ivan Valiela include Rutgers University & Woods Hole Oceanographic Institution.

Mangrove forests: one of the world's threatened major tropical environments.

Abstract: he mass media and scientific press have widely reported losses of tropical environments, such as fellingof rain forests and bleaching of coral reefs.This well-meritedattention has created a worldwide constituency that supportsconservation and restoration efforts in both of these threat-ened ecosystems. The remarkable degree of public aware-ness and support has been manifested in benefit rock concertsat Carnegie Hall and in the designation of ice cream flavorsafter rain forest products. Mangrove forests are another im-portant tropical environment,but these have received muchless publicity.Concern about the magnitude of losses of man-grove forests has been voiced mainly in the specialized liter-ature (Saenger et al. 1983, Spalding et al. 1997).Mangrove trees grow ubiquitously as a relatively narrowfringe between land and sea, between latitudes 25°N and30°S.They form forests of salt-tolerant species,with complexfood webs and ecosystem dynamics (Macnae 1968,Lugo andSnedaker 1974, Tomlinson 1986).Destruction of mangrove forests is occurring globally.Global changes such as an increased sea level may affect man-groves (Ellison 1993,Field 1995),although accretion rates inmangrove forests may be large enough to compensate for thepresent-day rise in sea level (Field 1995).More important,itis human alterations created by conversion of mangroves tomariculture,agriculture,and urbanization,as well as forestryuses and the effects of warfare, that have led to the remark-able recent losses of mangrove habitats (Saenger et al. 1983,Fortes 1988, Marshall 1994, Primavera 1995, Twilley 1998).New data on the magnitude of mangrove area and changesin it have become more readily available, especially with theadvent of satellite imagery and the Internet. Moreover, in-formation about the function of mangrove swamps, theirimportance in the sustainability of the coastal zone, and theeffects of human uses of mangrove forests is growing. Somepublished regional assessments have viewed anthropogenicthreats to mangrove forests with alarm (Ong 1982,Fortes 1988,Ellison and Farnsworth 1996),but reviews at the global scaleare dated (Linden and Jernelov 1980, Saenger et al. 1983).We collated and revised published information to reviewthe status of mangrove swamps worldwide.To assess the sta-tus of this major coastal environment, we compiled and ex-amined available data to quantify the extent of mangroveforest areas in different parts of the world,the losses of man-grove forest area recorded during recent decades, and therelative contributions by various human activities to theselosses.We first assessed current mangrove forest area in tropicalcountries of the world.It is difficult to judge the quality of thesedata in the published literature, because in many cases themethods used to obtain them were insufficiently described andthe associated uncertainty was not indicated. Much infor-mation based on satellite imagery is summarized in the

Macroalgal blooms in shallow estuaries: Controls and ecophysiological and ecosystem consequences

Abstract: Macroalgal blooms are produced by nutrient enrichment of estuaries in which the sea floor lies within the photic zone. We review features of macroalgal blooms pointed out in recent literature and summarize work done in the Waquoit Bay Land Margin Ecosystems Research project which suggests that nutrient loads, water residence times, presence of fringing salt marshes, and grazing affect macroalgal blooms. Increases in nitrogen supply raise macroalgal N uptake rates, N contents of tissues, photosynthesis-irradiance curves and P max , and accelerate growth of fronds. The resulting increase in macroalgal biomass is the macroalgal bloom, which can displace other estuarine producers. Fringing marshes and brief water residence impair the intensity of macroalgal blooms. Grazing pressure may control blooms of palatable macroalgae, but only at lower N loading rates. Macroalgal blooms end when growth of the phytoplankton attenuates irradiation reaching the bottom. In estuaries with brief water residence times, phytoplankton may not have enough time to grow and shade macrophytes. High phytoplankton division rates achieved at high nutrient concentrations may compensate for the brief time to divide before cells are transported out of the estuary. Increased N loads and associated macroalgal blooms pervasively and fundamentally alter estuarine ecosystems. Macroalgae intercept nutrients regenerated from sediments and thus uncouple biogeochemical sedimentary cycles from those in the water column. Macroalgae take up so much N that water quality seems. high even where N loads are high. Macroalgal C moves more readily through microbial and consumer food webs than C derived from seagrasses that were replaced by macroalgae. Macroalgae dominate O 2 profiles of the water columns of shallow estuaries and thus alter the biogeochemistry of the sediments. More frequent hypoxia and habitat changes associated with macroalgal blooms also changes the abundance of benthic fauna in affected estuaries. Approaches to remediation of the many pervasive effects of macroalgal blooms need to include interception of nutrients at their watershed sources and perhaps removal by harvest of macroalgae or by increased flushing. Although we have much knowledge of macroalgal dynamics, all such management initiatives will require additional information.

Marine ecological processes

Abstract: Contents Preface to the Third Edition Preface to the Second Edition Preface to the First Edition Part I Primary production in marine environments Chapter 1 Primary producers in the sea 1.1 Phytoplankton 1.2 Benthic producers Chapter 2 Production: the formation of organic matter 2.1 Photosynthesis 2.2 Chemosynthesis 2.3 Measurement of producer biomass and primary production 2.4 Contributions by different marine primary producers Chapter 3 Factors affecting primary production 2.1 Light 2.2 The Uptake and Availability of Nutrients 2.3 Temperature and Interactions with Other Factors 2.4 Distribution of Phytoplankton Production Over the World Ocean Part II Consumers in Marine Environments Chapter 3 Dynamics of Populations of Consumers 3.1 Elements of the Mathematical Description of Growth of Populations 3.2 Survival Life Tables 3.3 Fecundity Life Tables 3.4 Some Properties of Life Table Variables 3.5 Reproductive Tactics Chapter 4 Competition for Resources Among Consumers 4.1 Population Growth in Environments with Finite Resources 4.2 The Nature of Competition 4.3 Density-Dependent Control of Abundance 4.4 Density-Dependent Versus Density-Independent Effects on Abundance 4.5 Resource Partitioning 4.6 Niche Breadth and Species Packing Chapter 5 Feeding and Responses to Food Abundance 5.1 Introduction 5.2 Functional Response to Prey Density 8.3 Control Mechanisms in Benthic Communities Chapter 9 Trophic Structure 2: Components and Controls in Water Column Food Webs 9.1 Food Webs in Marine Water Columns 9.2 Microbial Food Webs 9.3 The Classic Microplankton Food Web 9.4 Speculations as to Control of Prey Populations by Larger Predators in the Marine Water Column Chapter 10 Taxonomic Structure: Species Diversity 10.1 Introduction 10.2 Measurement of Diversity 10.3 Factors Affecting Diversity 10.4 Integration of Factors Affecting Diversity and Some Consequences Chapter 11 Spatial Structure: Patchiness 11.1 Scales of Patchiness 11.2 Description of Spatial Distributions 11.3 Sources of Patchiness 11.4 Ecological Consequences of Patchiness 11.5 The Problem of Upscaling Chapter 12 Development of Structure in Marine Communities: Colonization and Succession 12.1 Introduction 12.2 Colonization Processes 12.3 Case Histories of Colonization and Succession 12.4 Interaction Among Communities at Different Stages of Succession 12.5 Generalized Properties of Succession in Marine Environments Part IV Functioning of Marine Ecosystems Chapter 13 The Carbon Cycle: Production and Transformations of Organic Matter 13.1 Inorganic Carbon 13.2 The Carbon Cycle in Aerobic Environments 13.3 The Carbon Cycle in Anoxic Environments Chapter 14 Nutrient Cycles and Ecosystem Stoichiometry 14.1 Phosphorus 14.2 Nitrogen 14.3 Sulfur 14.4 Ecosystem Energetics and Stoichiometry Chapter 15 Seasonal Changes in Marine Ecosystems 15.1 Introduction 15.2 Water Column Seasonal Cycles 15.3 Benthic Seasonal Cycles 15.4 Control of Seasonal Cycles Chapter 16 Long-Term and Large-Scale Change in Marine Ecosystems"/p> 16.1 Introduction 16.2 Large-Scale Effects of Long-Term Atmospheric Changes 16.3 Depletion of Fishery Stocks 16.4 Eutrophication 16.5 Toxic Contamination 16.6 Spread of Exotic Species 16.7 Harmful Algal Blooms 16.8 Interception of Freshwater Inputs and Sediment Loads 16.9 Multiple Factors in Concert: The Case of Black Sea 16.10 Implications of Long-Term, Large-Scale Changes References Index

Nitrogen-stable isotope signatures in estuarine food webs : A record of increasing urbanization in coastal watersheds

Abstract: Nutrient enrichment as a result of anthropogenic activity concentrated along the land-sea margin is increasing eutrophication of near-shore waters across the globe. Management of eutrophication in the coastal zone has been hampered by the lack of a direct method to trace nitrogen sources from land into coastal food webs. Stable isotope data from a series of estuaries receiving nitrogen loads from 2 to 467 kg N ha -1 yr -1 from the Waquoit Bay watershed, Cape Cod, Massachusetts, indicate that producer and consumer 15 N-to- 14 N ratios record increases in wastewater nitrogen inputs. Nitrate from groundwater-borne wastewater introduces a 15 N-enriched tracer to estuaries. This study explicitly links anthropogenically derived nitrogen from watersheds to nitrogen in estuarine plants and animals, and suggests that wastewater nitrogen may be detectable in estuarine biota at relatively low loading rates, before eutrophication leads to major changes in species composition and abundance within estuarine food webs.

Couplings of watersheds and coastal waters: sources and consequences of nutrient enrichment in Waquoit Bay, Massachusetts

Abstract: Human activities on coastal watersheds provide the major sources of nutrients entering shallow coastal ecosystems. Nutrient loadings from watersheds are the most widespread factor that alters structure and function of receiving aquatic ecosystems. To investigate this coupling of land to marine systems, we are studying a series of subwatersheds of Waquoit Bay that differ in degree of urbanization and hence are exposed to widely different nutrient loading rates. The subwatersheds differ in the number of septic tanks and the relative acreage of forests. In the area of our study, groundwater is the major mechanism that transports nutrients to coastal waters. Although there is some attenuation of nutrient concentrations within the aquifer or at the sediment-water interface, in urbanized areas there are significant increases in the nutrient content of groundwater arriving at the shore’s edge. The groundwater seeps or flows through the sediment-water boundary, and sufficient groundwater-borne nutrients (nitrogen in particular) traverse the sediment-water boundary to cause significant changes in the aquatic ecosystem. These loading-dependent alterations include increased nutrients in water, greater primary production by phytoplankton, and increased macroaglal biomass and growth (mediated by a suite of physiological responses to abundance of nutrients). The increased macroalgal biomass dominates the bay ecosystem through second- or third-order effects such as alterations of nutrient status of water columns and increasing frequency of anoxic events. The increases in seaweeds have decreased the areas covered by eelgrass habitats. The change in habitat type, plus the increased frequency of anoxic events, change the composition of the benthic fauna. The data make evident the importance of bottom-up control in shallow coastal food webs. The coupling of land to sea by groundwater-borne nutrient transport is mediated by a complex series of steps; the cascade of processes make it unlikely to find a one-to-one relation between land use and conditions in the aquatic ecosystem. Study of the process and synthesis by appropriate models may provide a way to deal with the complexities of the coupling.

Effects of biodiversity on ecosystem functioning: a consensus of current knowledge

Abstract: Humans are altering the composition of biological communities through a variety of activities that increase rates of species invasions and species extinctions, at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a strong potential to alter ecosystem properties and the goods and services they provide to humanity. Ecological experiments, observations, and theoretical developments show that ecosystem properties depend greatly on biodiversity in terms of the functional characteristics of organisms present in the ecosystem and the distribution and abundance of those organisms over space and time. Species effects act in concert with the effects of climate, resource availability, and disturbance regimes in influencing ecosystem properties. Human activities can modify all of the above factors; here we focus on modification of these biotic controls. The scientific community has come to a broad consensus on many aspects of the re- lationship between biodiversity and ecosystem functioning, including many points relevant to management of ecosystems. Further progress will require integration of knowledge about biotic and abiotic controls on ecosystem properties, how ecological communities are struc- tured, and the forces driving species extinctions and invasions. To strengthen links to policy and management, we also need to integrate our ecological knowledge with understanding of the social and economic constraints of potential management practices. Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain.

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

Abstract: The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Global Change and the Ecology of Cities

Abstract: Urban areas are hot spots that drive environmental change at multiple scales. Material demands of production and human consumption alter land use and cover, biodiversity, and hydrosystems locally to regionally, and urban waste discharge affects local to global biogeochemical cycles and climate. For urbanites, however, global environmental changes are swamped by dramatic changes in the local environment. Urban ecology integrates natural and social sciences to study these radically altered local environments and their regional and global effects. Cities themselves present both the problems and solutions to sustainability challenges of an increasingly urbanized world.

Supporting Online Material for Spreading Dead Zones and Consequences for Marine Ecosystems

Abstract: Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. The formation of dead zones has been exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels. Enhanced primary production results in an accumulation of particulate organic matter, which encourages microbial activity and the consumption of dissolved oxygen in bottom waters. Dead zones have now been reported from more than 400 systems, affecting a total area of more than 245,000 square kilometers, and are probably a key stressor on marine ecosystems.

The value of estuarine and coastal ecosystem services

Abstract: The global decline in estuarine and coastal ecosystems (ECEs) is affecting a number of critical benefits, or ecosystem services. We review the main ecological services across a variety of ECEs, including marshes, mangroves, nearshore coral reefs, seagrass beds, and sand beaches and dunes. Where possible, we indicate estimates of the key economic values arising from these services, and discuss how the natural variability of ECEs impacts their benefits, the synergistic relationships of ECEs across seascapes, and management implications. Although reliable valuation estimates are beginning to emerge for the key services of some ECEs, such as coral reefs, salt marshes, and mangroves, many of the important benefits of seagrass beds and sand dunes and beaches have not been assessed properly. Even for coral reefs, marshes, and mangroves, important ecological services have yet to be valued reliably, such as cross-ecosystem nutrient transfer (coral reefs), erosion control (marshes), and pollution control (mangroves). An important issue for valuing certain ECE services, such as coastal protection and habitat-fishery linkages, is that the ecological functions underlying these services vary spatially and temporally. Allowing for the connectivity between ECE habitats also may have important implications for assessing the ecological functions underlying key ecosystems services, such coastal protection, control of erosion, and habitat-fishery linkages. Finally, we conclude by suggesting an action plan for protecting and/or enhancing the immediate and longer-term values of ECE services. Because the connectivity of ECEs across land-sea gradients also influences the provision of certain ecosystem services, management of the entire seascape will be necessary to preserve such synergistic effects. Other key elements of an action plan include further ecological and economic collaborative research on valuing ECE services, improving institutional and legal frameworks for management, controlling and regulating destructive economic activities, and developing ecological restoration options.