An analysis of the interactions between pelagic food web processes and element cycling in lakes. While some findings are examined in terms of classical concepts from the ecological theory of predator-prey systems, special emphasis is placed on exploring how stoichiometric relationships between primary producers and herbivores influence the stability and persistence of planktonic food webs. The author develops simple dynamic models of the cycling of mineral nutrients through plankton algae and grazers, and then goes on to explore them both analytically and numerically. The results thus obtained are of great interest to both theoretical and experimental ecologists. Moreover, the models themselves are of immense practical use in the area of lake management.

Two of the most powerful ways in which humans have altered ecosystems are by increasing productivity and changing the densities of important consumers. The bottom-up effects of productivity and the top-down effects of consumers have been identified as primary determinants of biological diversity, though the links between them remain unclear. Understanding how consumers and productivity act and interact to yield differences in diversity is of both conceptual and pragmatic importance. Here, I describe three experiments designed to examine the links between grazing, productivity, and diversity in rocky intertidal systems in Oregon and New Zealand. In two experiments I used fully-factorial designs in which I manipulated both grazing and nutrients. Both experiments revealed the primary importance of grazing as a structuring force of algal assemblages. In the Oregon experiment, I also document an interaction between grazing and productivity, with nutrient enrichment decreasing algal diversity at low grazer densities and increasing algal diversity at high grazer densities. This interaction was not apparent in the New Zealand experiment. In the absence of grazers, nutrient addition led to increased abundance of foliose algae at this site but had no net effect on algal diversity. In the third experiment, also conducted in New Zealand, I used natural variation in nearshore productivity as a backdrop against which I manipulated the access of grazers. In this experiment, I found that grazers had negative impacts on benthic algal diversity and abundance at sites with lower productivity and negligible impacts on benthic algal assemblages at sites with higher productivity. Overall these three studies suggest that in these intertidal grazer-dominated communities, the strong top-down effects often documented in such systems can be modified by more subtle bottom-up effects. Together, results from these experiments elucidate factors that determine algal diversity in these systems and underscore the importance of the evolutionary context in which experiments are conducted. Finally, I conclude with a synthesis of the literature in which I put these and other findings to work by exploring the ways in which basic marine ecological research can inform the management of human activities that affect the marine environment.

Nutrient enrichment is common in Irish streams yet despite extensive reports of algal nutrient requirements, generally, this study found no differences in algal biomass across a wide nutrient gradient. In addition, increases in light levels resulted in no net change in algal biomass. Nevertheless, greater densities of grazing benthic macroinvertebrates (grazers), principally Baetis rhodani, were found in high nutrient, high light streams. The ability of grazers to effectively prevent the accrual of highly productive algae was demonstrated through a series of invertebrate grazer exclusion experiments. These experiments also revealed greater grazing pressures at more nutrient rich sites, presumably a function of greater productivity of the grazers{u2019} algal food source. Top-down grazer control of algae was also shown to be highly variable in time and space. Vigorous algal growth during periods of reduced grazing pressure resulted in rapid accrual of the nuisance filamentous alga Cladophora glomerata. Established filaments developed a degree of grazer resistance and there was evidence that these filaments benefitted from the presence of microphyte grazers, suggesting that grazing pressure can shift between a negative and a positive force depending on algal morphology. High-flow events overrode all other interactions and effectively reduced previously accrued algal biomass to levels near zero yet did not negatively effect grazers. Post-spate algal-invertebrate interactions were subsequently reverted to grazer top-down control. During a prolonged low-flow period, Cladophora in shaded habitats accrued to similar levels as in unshaded habitats. These results indicate that despite light-limited growth, algal biomass can attain similar levels over time in shaded habitats, the threshold of which is governed by flow conditions. This study has demonstrated the dominant roles that small bodied grazers and hydraulic disturbance play in regulating algal standing stock in streams in south-west Ireland. These aspects of stream ecosystem function deserve greater attention from a stream management perspective.

Environmental problems in coastal ecosystems can sometimes be attributed to excess nutrients flowing from upstream watersheds into estuarine settings. This nutrient over-enrichment can result in toxic algal blooms, shellfish poisoning, coral reef destruction, and other harmful outcomes. All U.S. coasts show signs of nutrient over-enrichment, and scientists predict worsening problems in the years ahead. Clean Coastal Waters explains technical aspects of nutrient over-enrichment and proposes both immediate local action by coastal managers and a longer-term national strategy incorporating policy design, classification of affected sites, law and regulation, coordination, and communication. Highlighting the Gulf of Mexico's "Dead Zone," the Pfiesteria outbreak in a tributary of Chesapeake Bay, and other cases, the book explains how nutrients work in the environment, why nitrogen is important, how enrichment turns into over-enrichment, and why some environments are especially susceptible. Economic as well as ecological impacts are examined. In addressing abatement strategies, the committee discusses the importance of monitoring sites, developing useful models of over-enrichment, and setting water quality goals. The book also reviews voluntary programs, mandatory controls, tax incentives, and other policy options for reducing the flow of nutrients from agricultural operations and other sources.

Addresses reservoirs as unique ecological systems and presents research indicating that reservoirs fall into two or three highly concatenated, interactive ecological systems ranging from riverine to lacustrine or hybrid systems. Includes some controversial concepts about the limnology of reservoirs, which make for interesting reading.

This book presents an in-depth discussion of the biological and ecological geography of the oceans. It synthesizes locally restricted studies of the ocean to generate a global geography of the vast marine world.Based on patterns of algal ecology, the book divides the ocean into four primary compartments, which are then subdivided into secondary compartments.*Includes color insert of the latest in satellite imagery showing the world's oceans, their similarities and differences*Revised and updated to reflect the latest in oceanographic research*Ideal for anyone interested in understanding ocean ecology -- accessible and informative

The advent of space travel has been accompanied by an increased appreciation of the algae as organisms which are of use to man. These organisms, when grown on human wastes, hold promise of serving as gas exchangers, waste disposers, and food sources for crew members of space vehicles.

Biodiversity and Climate Change Adaptation in Tropical Islands provides comprehensive information on climate change, biodiversity, possible impacts, adaptation measures and policy challenges to help users rehabilitate and preserve the natural resources of tropical islands. While biodiversity and climate change of tropical islands has previously received less attention, it is ironically one of the most vulnerable regions in this regard. The core content of the work derives largely from the ideas and research output from various reputed scientists and experts who have recorded climate change impacts on aquatic and coastal life in tropical regions. Contributors have direct working experience with the tribes in some of the tropical islands. All of their expertise and information is compiled and presented in the work, including coverage related to climate change. This work highlights the ever-growing need to develop and apply strategies that optimize the use of natural resources, both on land and in water and judicious use of biodiversity. It functions as a critical resource on tropical island biodiversity for researchers, academicians, practitioners and policy makers in a variety of related disciplines. - Covers a huge range of biodiversity documentation, conservation measures and strategies that can be applied to various sectors, from forests to agriculture - Brings together expertise from researchers in the area who have direct experience in the regions described - Contains a wealth of field research related to biodiversity conservation and its applications from a variety of tropical islands