Recently developed techniques for estimating bacterial biomass and productivity indicate that bacterial biomass in the sea is related to phytoplankton concentration and that bacteria utilise 10 to 50 % of carbon fixed by photosynthesis. Evidence is presented to suggest that numbers of free bacteria are controlled by nanoplankton~c heterotrophic flagellates which are ubiquitous in the marine water column. The flagellates in turn are preyed upon by microzooplankton. Heterotrophic flagellates and microzooplankton cover the same size range as the phytoplankton, thus providing the means for returning some energy from the 'microbial loop' to the conventional planktonic food chain.

/pdf/the-ecological-role-of-water-column-microbes-in-the-sea-34dv8tiwzr.pdf

The Ecological Role of Water-Column Microbes in the Sea*

The use of recommender systems is an emerging trend today, when user behavior information is abundant. There are many large datasets available for analysis because many businesses are interested in future user opinions. Sophisticated algorithms that predict such opinions can simplify decision-making, improve customer satisfaction, and increase sales. However, modern datasets contain millions of records, which represent only a small fraction of all possible data. Furthermore, much of the information in such sparse datasets may be considered irrelevant for making individual recommendations. As a result, there is a demand for a way to make personalized suggestions from large amounts of noisy data.
Current recommender systems are usually all-in-one applications that provide one type of recommendation. Their inflexible architectures prevent detailed examination of recommendation accuracy and its causes. We introduce a novel architecture model that supports scalable, distributed suggestions from multiple independent nodes. Our model consists of two components, the input matrix generation algorithm and multiple platform-independent combination algorithms. A dedicated input generation component provides the necessary data for combination algorithms, reduces their size, and eliminates redundant data processing. Likewise, simple combination algorithms can produce recommendations from the same input, so we can more easily distinguish between the benefits of a particular combination algorithm and the quality of the data it receives. Such flexible architecture is more conducive for a comprehensive examination of our system.
We believe that a user's future opinion may be inferred from a small amount of data, provided that this data is most relevant. We propose a novel algorithm that generates a more optimal recommender input. Unlike existing approaches, our method sorts the relevant data twice. Doing this is slower, but the quality of the resulting input is considerably better. Furthermore, the modular nature of our approach may improve its performance, especially in the cloud computing context. We implement and validate our proposed model via mathematical modeling, by appealing to statistical theories, and through extensive experiments, data analysis, and empirical studies.
Our empirical study examines the effectiveness of accuracy improvement techniques for collaborative filtering recommender systems. We evaluate our proposed architecture model on the Netflix dataset, a popular (over 130,000 solutions), large (over 100,000,000 records), and extremely sparse (1.1%) collection of movie ratings. The results show that combination algorithm tuning has little effect on recommendation accuracy. However, all algorithms produce better results when supplied with a more relevant input. Our input generation algorithm is the reason for a considerable accuracy improvement.

/pdf/a-distributed-architecture-centric-approach-to-computing-31zmh6iinx.pdf

A distributed, architecture-centric approach to computing accurate recommendations from very large and sparse datasets

Communities of microscopic plant life, or phytoplankton, dominate the Earth's aquatic ecosystems. This important new book by Colin Reynolds covers the adaptations, physiology and population dynamics of phytoplankton communities in lakes and rivers and oceans. It provides basic information on composition, morphology and physiology of the main phyletic groups represented in marine and freshwater systems and in addition reviews recent advances in community ecology, developing an appreciation of assembly processes, co-existence and competition, disturbance and diversity. Although focussed on one group of organisms, the book develops many concepts relevant to ecology in the broadest sense, and as such will appeal to graduate students and researchers in ecology, limnology and oceanography.

/pdf/the-ecology-of-phytoplankton-4ev70n3jsq.pdf

The Ecology of Phytoplankton

Kelp forests are phyletically diverse, structurally complex and highly productive components of coldwater rocky marine coastlines. This paper reviews the conditions in which kelp forests develop globally and where, why and at what rate they become deforested. The ecology and long archaeological history of kelp forests are examined through case studies from southern California, the Aleutian Islands and the western North Atlantic, well-studied locations that represent the widest possible range in kelp forest biodiversity. Global distribution of kelp forests is physiologically constrained by light at high latitudes and by nutrients, warm temperatures and other macrophytes at low latitudes. Within mid-latitude belts (roughly 40–60° latitude in both hemispheres) well-developed kelp forests are most threatened by herbivory, usually from sea urchins. Overfishing and extirpation of highly valued vertebrate apex predators often triggered herbivore population increases, leading to widespread kelp deforestation. Such deforestations have the most profound and lasting impacts on species-depauperate systems, such as those in Alaska and the western North Atlantic. Globally urchin-induced deforestation has been increasing over the past 2–3 decades. Continued fishing down of coastal food webs has resulted in shifting harvesting targets from apex predators to their invertebrate prey, including kelp-grazing herbivores. The recent global expansion of sea urchin harvesting has led to the widespread extirpation of this herbivore, and kelp forests have returned in some locations but, for the first time, these forests are devoid of vertebrate apex predators. In the western North Atlantic, large predatory crabs have recently filled this void and they have become the new apex predator in this system. Similar shifts from fish- to crab-dominance may have occurred in coastal zones of the United Kingdom and Japan, where large predatory finfish were extirpated long ago. Three North American case studies of kelp forests were examined to determine their long history with humans and project the status of future kelp forests to the year 2025. Fishing impacts on kelp forest systems have been both profound and much longer in duration than previously thought. Archaeological data suggest that coastal peoples exploited kelp forest organisms for thousands of years, occasionally resulting in localized losses of apex predators, outbreaks of sea urchin populations and probably small-scale deforestation. Over the past two centuries, commercial exploitation for export led to the extirpation of sea urchin predators, such as the sea otter in the North Pacific and predatory fishes like the cod in the North Atlantic. The large-scale removal of predators for export markets increased sea urchin abundances and promoted the decline of kelp forests over vast areas. Despite southern California having one of the longest known associations with coastal kelp forests, widespread deforestation is rare. It is possible that functional redundancies among predators and herbivores make this most diverse system most stable. Such biodiverse kelp forests may also resist invasion from non-native species. In the species-depauperate western North Atlantic, introduced algal competitors carpet the benthos and threaten future kelp dominance. There, other non-native herbivores and predators have become established and dominant components of this system. Climate changes have had measurable impacts on kelp forest ecosystems and efforts to control the emission of greenhouse gasses should be a global priority. However, overfishing appears to be the greatest manageable threat to kelp forest ecosystems over the 2025 time horizon. Management should focus on minimizing fishing impacts and restoring populations of functionally important species in these systems.

/pdf/kelp-forest-ecosystems-biodiversity-stability-resilience-and-3rb156vhzw.pdf

Kelp forest ecosystems: biodiversity, stability, resilience and future

We review the effects of fishing on benthic fauna, habitat, diversity, community structure and trophic interactions in tropical, temperate and polar marine environments and consider whether it is possible to predict or manage fishing-induced changes in marine ecosystems Such considerations are timely given the disillusionment with some fishery management strategies and that policy makers need a scientific basis for deciding whether they should respond to social, economic and political demands for instituting or preventing ecosystem-based management Fishing has significant direct and indirect effects on habitat, and on the diversity, structure and productivity of benthic communities These effects are most readily identified and last longest in those areas that experience infrequent natural disturbance The initiation of fishing in an unfished system leads to dramatic changes in fish community structure As fishing intensity increases the additional effects are more difficult to detect Fishing has accelerated and magnified natural declines in the abundance of many forage fishes and this has lead to reduced reproductive success and abundance in birds and marine mammals However, such donor-controlled dynamics are less apparent in food webs where fishes are the top predators since their feeding strategies are rather more plastic than those of most birds and mammals Fishers tend to target species in sequence as a fishery develops and this leads to changes in the composition of the fished communities with time The dramatic and apparently compensatory shifts in the biomass of different species in many fished ecosystems have often been driven by environmental change rather than the indirect effects of fishing Indeed, in most pelagic systems, species replacements would have occurred, albeit less rapidly, in the absence of fishing pressure In those cases when predator or prey species fill a key role, fishing can have dramatic indirect effects on community structure Thus fishing has shifted some coral reef ecosystems to alternate stable states because there is tight predator–prey coupling between invertebrate feeding fishes and sea urchins Fishing has reduced, and locally extirpated, populations of predatory fishes These reductions do not have a consistent effect on the abundance and diversity of their prey: environmental processes control prey populations in some systems, whereas top-down processes are more important in others By-catch which is discarded during fishing activities may sustain populations of scavenging species, particularly seabirds We conclude by identifying the circumstances in which new research is needed to guide managers and stress the importance of unfished control sites for studies of fishing effects We discuss the advantages and disadvantages of closed area management (marine reserves) and the conditions under which such management is likely to provide benefits for the fishery or ecosystem

/pdf/the-effects-of-fishing-on-marine-ecosystems-4zb9eqofxt.pdf

The effects of fishing on marine ecosystems

Contents. Preface to Third Edition. Preface to Second Edition. Preface to First Edition. 1 Marine Ecology Comes of Age. Part A: Processes on a Scale of less than 1 Kilometer. 2 Biology and Boundary Layers. 3 Vertical Structure of the Open Ocean: Biology of the Mixed Layer. 4 Vertical Structure in Coastal Waters: Freshwater Run-off and Tidal Mixing. Part B: Processes on a Scale of 1-1000 Kilometers. 5 Vertical Structure in Coastal Waters: Coastal Upwelling Regions. 6 Fronts in Coastal Waters. 7 Tides, Tidal Mixing, and Internal Waves. Part C: Processes on a Scale of Thousands of Kilometers. 8 Ocean Basin Circulation: The Biology of Major Currents, Gyres, Rings, and Eddies. 9 Variability in Ocean Circulation: its Biological Consequences. 10 The Oceans and Global Climate Change: Physical and Biological Aspects. Part D: Discussion and Conclusions. 11 Questions for the Future. Appendix. References. Index

Dynamics of marine ecosystems:biological-physical interactions in the oceans

Dynamics of marine ecosystems

In both freshwater and marine habitats, vascular marine plants arc little used by animals that graze directly on them, because they have a relatively high content of indigestible fiber and a low content of nitrogen. The chief emphasis of detritus research in the 1970s was to show how microorganisms progressively reduce the content of fiber and increase the content of nitrogren in vascular plant detritus, rendering it nutritious for animals. Algal (seaweed, diatom, etc.) detritus starts with a lower fiber content and a higher nitrogen content. Many animals can use it directly, and a very short period of microbial colonization renders it highly nutritious. As a result, a high proportion of the algal carbon originally produced passes into animals via detrital food webs, while a low proportion of vascular plant carbon does so. Much more of the latter simply supports microbial respiration. In the 1980s it was shown, particularly for freshwater habitats, that the dissolved organic matter (DOM) released by plants while living or in the early stages of decomposition readily precipitates on surfaces and forms amorphous particulate matter with a low content of refractory material. These particles are highly nutritious for animals and are used directly by freshwater fish such as Sarotherodon (= Tifapia), which is commercially important, especially in Africa and South America. It is suggested that the DOM pathway may be ecologically more significant than the POM (particulate organic matter) pathway and that processes analogous to those shown for lakes and rivers probably occur in estuarine and coastal waters. There is much circumstantial evidence to suggest that planktonic food webs based on DOM are much more important than previously thought. The conversion of DOM to POM through the “microbial loop” and its utilization in higher trophic levels is a.n urgent topic for further study.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1988.33.4part2.0910

Production and use of detritus in various freshwater, estuarine, and coastal marine ecosystems

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1991.36.5.1066

Seaweeds: Their environment, biogeography, and ecophysiology

Preface. 1. The Subject and the Approach. Part One: Estuarine Ecosystems and their Components. 2. Estuaries: their Physical Properties in Relation to their Biological Functioning. 3. Salt-Marshes. 4. Mangroves. 5. Seagrass Systems. 6. The Fate of Macrophyte Detritus. 7. Estuarine Planktonic Systems. 8. Estuarine Benthic Systems. 9. Fish and Shellfish in Estuaries. 10. The Integrated Functioning of Estuaries. Part Two: Coastal Systems: Rocky Shortes and Beaches. 11. Intertidal Rocky Shores. 12. Subtidal Rocky Shores. 13. Sandy Beaches. Part Three: Shelf Ecosystems. 14. Planktonic Systems on the Continental Shelves. 15. Coastal Upwelling Ecosystems. 16. Coral Reefs. 17. Fish Production on the Continental Shelves. Part Four: Synthesis. 18. The Whole-Ecosystem Approach to Managing Coastal Waters: Questions for the Future. References. Suggestions for Further Reading: recent Developments and More. Advanced Topics. Index.

K.H. Mann

Papers

Dynamics of marine ecosystems:biological-physical interactions in the oceans

Dynamics of marine ecosystems

Production and use of detritus in various freshwater, estuarine, and coastal marine ecosystems

Seaweeds: Their environment, biogeography, and ecophysiology

Ecology of Coastal Waters: With Implications For Management