Author: Publisher: ISBN: Category : Dissertations, Academic Languages : en Pages : 65
Book Description
Chapter 1. We developed methods to measure juvenile growth rates of the spionid polychaete Polydora cornuta in nature. We transplanted and recovered small vials containing labeled individuals and measured each worm's body volume before and after worms spent a week in field sediments. We transplanted labeled individuals to three elevations on an intertidal sandflat in Oneonta Slough within the Tijuana River National Estuarine Research Reserve: a high elevation 0.7 m above mean lower low water (MLLW), a mid elevation 0.4 m above MLLW, and a low elevation 0.1 m above MLLW. To include a range of environmental conditions, we performed two 7-d transplantations in July 2009 and two in November 2009. On average, we recovered one-third of the transplanted juveniles. Mean relative growth rates (RGR) declined significantly from 7.7 % d-1 at the low elevation to 2.4 % d-1at the high elevation. There was a positive correlation between RGR and the time each elevation was submerged, suggesting the decline in RGRs with increasing elevation was due to a reduction in the time available for suspension feeding. RGRs during one transplantation (12-19 November) were significantly slower than RGRs during the other three transplantations, especially at the high and mid elevations. Due to seasonality in the mixed semidiurnal tides, the 12-19 November period was the only transplantation that experienced lower low tides during the afternoon. The slower RGRs during this time of exposure to afternoon sunlight and temperatures suggest physiological stress may have contributed to reduced RGRs during this transplantation. Chapter 2. Sublethal predation can be a significant trophic pathway in sediment communities, and the regeneration of damaged tissue affects the activity, growth, and reproduction of prey. A field experiment was conducted 12-18 July 2010 in the Tijuana Estuary, California (+32.56617°, -117.13152°) to measure in-situ rates of body growth and palp regeneration of the polychaete Polydora cornuta after simulating sublethal predation by removing 2, 1, or 0 palps from labeled individuals. After 3 d in the field, individuals that had 2 palps removed grew significantly slower than worms that had 0 palps removed; 1-palp worms had intermediate growth. After 6 d in the field, rates of body growth were faster than those of worms recovered after 3 d, with similar trends among the three palp treatments. During the 3-d transplantation, removed palps regenerated to half the initial length of unmanipulated palps. After 6 d, palp lengths did not differ significantly among treatment groups, indicating complete regeneration. The regeneration rate of removed palps was significantly faster than the growth rate of undamaged palps, and palp-regeneration rate did not differ significantly between worms that had 1 or 2 palps removed. Chapter 3. Most spionid polychaetes are interface feeders that switch between suspension feeding in fast flows and deposit feeding in slow flows. Experiments in laboratory flumes show that growth rates of spionids increase with current speed and the flux of suspended food. These results have yet to be tested in the field where hydrodynamic conditions and other environmental variables are more complicated than in laboratory flumes. We constructed paired flow-manipulation channels (FMCs) that either increased or decreased the local velocities of the ambient tidal currents in Oneonta Slough, Tijuana Estuary. Paired FMCs were replicated in four trials that each lasted 4.3-9.0 days. During each trial, approximately 100 pre-measured Polydora cornuta were established in individually labeled vials that were transplanted into the subtidal sediment near the center of each FMC. At the end of each trial, recovered individuals were re-measured to calculate their relative growth rates. Acoustic dopler velocimitry (ADV) was used to measure 3-dimensional velocity and turbulence during ebb tide. On average, FMCs either increased ambient current velocity by 52% or decreased it by 45%. Calculations of turbulence (RMS) indicated that both types of FMC also altered turbulence relative to the ambient flow. In contrast to results from laboratory flumes, which were limited to velocities too slow to erode sediments, juvenile P. cornuta transplanted to FMCs that decreased the ambient velocity grew significantly faster than individuals transplanted to FMCs that increased the ambient velocity. We suspect the slower growth of P. cornuta in FMCs that increased ambient velocity was due to reduced particle capture during suspension feeding. Results of our field experiment suggest that P. cornuta grows fastest in intermediate flows, as shown for several bivalves and other suspension-feeding benthos.
Author: John Terborgh Publisher: Island Press ISBN: 1597268194 Category : Science Languages : en Pages : 487
Book Description
Trophic cascades—the top-down regulation of ecosystems by predators—are an essential aspect of ecosystem function and well-being. Trophic cascades are often drastically disrupted by human interventions—for example, when wolves and cougars are removed, allowing deer and beaver to become destructive—yet have only recently begun to be considered in the development of conservation and management strategies. Trophic Cascades is the first comprehensive presentation of the science on this subject. It brings together some of the world’s leading scientists and researchers to explain the importance of large animals in regulating ecosystems, and to relate that scientific knowledge to practical conservation. Chapters examine trophic cascades across the world’s major biomes, including intertidal habitats, coastal oceans, lakes, nearshore ecosystems, open oceans, tropical forests, boreal and temperate ecosystems, low arctic scrubland, savannas, and islands. Additional chapters consider aboveground/belowground linkages, predation and ecosystem processes, consumer control by megafauna and fire, and alternative states in ecosystems. An introductory chapter offers a concise overview of trophic cascades, while concluding chapters consider theoretical perspectives and comparative issues. Trophic Cascades provides a scientific basis and justification for the idea that large predators and top-down forcing must be considered in conservation strategies, alongside factors such as habitat preservation and invasive species. It is a groundbreaking work for scientists and managers involved with biodiversity conservation and protection.
Author: Curtis Richardson Publisher: Springer Science & Business Media ISBN: 0387689230 Category : Science Languages : en Pages : 696
Book Description
The Florida Everglades ecosystem is recognised world-wide as a significant wetland whose natural processes have been altered and remain threatened. State and Federal US agencies face critical decisions about the course of conservation and restoration efforts. Synthesising nearly ten years of laboratory and field research of the Duke University Wetland Center, this book provides the long-term integrated scientific studies needed to understand the functioning of this region. Background information about the current and historical ecological conditions of the region set the context for reports of long-term research projects, while a series of gradient studies determine the effects of hydrology and nutrient changes. Subsequent sections present models for predicting responses to various conditions and analyse the studies and models, focusing on management and restoration of the Everglades.
Author: Stephen A. Bortone Publisher: CRC Press ISBN: 1420038184 Category : Nature Languages : en Pages : 559
Book Description
Acknowledging the present inability to determine objectively the status and trends among estuarine ecosystems, the environmental research community has recently stepped up efforts to develop and evaluate meaningful estuarine indicators. This goal requires the effort of researchers from a broad spectrum of disciplines. In order to expedite this init
Author: G.Allen Burton Publisher: CRC Press ISBN: 1351093452 Category : Science Languages : en Pages : 362
Book Description
Sediment Toxicity Assessment provides the latest information regarding how to evaluate sediment contamination and its effects on aquatic ecosystems. It presents an integrated ecosystem approach by detailing effective assessment methods, considerations, and effects to each major component of marine and freshwater systems, including the benthos, plankton, and fish communities. The approaches emphasize defining habitat conditions (physical and chemical), toxicant bioavailability, factors influencing toxicity (lab and field), biomarkers, acute and chronic toxicity, study design, collection methods, and EPA management strategies. The book also explains how to integrate the assessments. Sediment Toxicity Assessment will be useful to to all environmental managers, environmental scientists, ecotoxicologists, environmental regulators, aquatic ecologists, environmental contractors and consultants, instructors, students, conservation commissions, and environmental activist organizations.
Author: Mark B. Bain Publisher: ISBN: Category : Aquatic habitats Languages : en Pages : 234
Book Description
Abstract: Habitat is now the basis of most impact assessments and resource inventories, and it is the basis of many species management plans, mitigation planning, and environmental regulation. Habitats are relatively stable through time, easily defined in intuitive physical terms, and provide a tangible resource for negotiations and decision making. Numerous and varied methods of analyzing and reporting habitat conditions have been developed by federal, state, provincial, and private agencies. Habitat assessment approaches vary greatly among regions of the continent. The great variability in methods and an unusually wide range of practices have impeded the ability of agencies to share and synthesize information. A diversity of methods is desirable in the initial stages of a rapidly developing field, but enough time has passed to assess the state-of-knowledge and identify the best of the currently used methods and techniques. This manual is intended to provide fisheries biologists with a limited set of techniques for obtaining aquatic habitat data. The manual also describes the range of information collected and used in agency habitat analyses. Agencies planning habitat programs should review the synthesis of established and documented methods being used in North America (Appendix 1) and the planning recommendations in Chapter 2. Then, the remaining chapters should be reviewed to determine what types of habitat data should be included in the agency's program.
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Author: John Terborgh
Author: Robert Scott Carr
Author: Earl L. Bozeman
Author: Curtis Richardson
Author: Stephen A. Bortone
Author: G.Allen Burton
Author: Mark B. Bain