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.

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

http://www.no-sea-and-earth-pollution.org/ALBATROSS-ARTICLES_files/pollution-of-the-marine-environment-derraik-2002.pdf

The pollution of the marine environment by plastic debris: a review.

To a first approximation, the distribution of biodiversity across the Earth can be described in terms of a relatively small number of broad-scale spatial patterns. Although these patterns are increasingly well documented, understanding why they exist constitutes one of the most significant intellectual challenges to ecologists and biogeographers. Theory is, however, developing rapidly, improving in its internal consistency, and more readily subjected to empirical challenge.

Global patterns in biodiversity

Trabajo presentado en el 39th CIESM Congress, celebrado en Venecia, Italia, del 10 al 14 de mayo de 2010

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Biodiversity of the Mediterranean Sea: estimates, patterns and threats

The Mediterranean Sea is a marine biodiversity hot spot. Here we combined an extensive literature analysis with expert opinions to update publicly available estimates of major taxa in this marine ecosystem and to revise and update several species lists. We also assessed overall spatial and temporal patterns of species diversity and identified major changes and threats. Our results listed approximately 17,000 marine species occurring in the Mediterranean Sea. However, our estimates of marine diversity are still incomplete as yet—undescribed species will be added in the future. Diversity for microbes is substantially underestimated, and the deep-sea areas and portions of the southern and eastern region are still poorly known. In addition, the invasion of alien species is a crucial factor that will continue to change the biodiversity of the Mediterranean, mainly in its eastern basin that can spread rapidly northwards and westwards due to the warming of the Mediterranean Sea. Spatial patterns showed a general decrease in biodiversity from northwestern to southeastern regions following a gradient of production, with some exceptions and caution due to gaps in our knowledge of the biota along the southern and eastern rims. Biodiversity was also generally higher in coastal areas and continental shelves, and decreases with depth. Temporal trends indicated that overexploitation and habitat loss have been the main human drivers of historical changes in biodiversity. At present, habitat loss and degradation, followed by fishing impacts, pollution, climate change, eutrophication, and the establishment of alien species are the most important threats and affect the greatest number of taxonomic groups. All these impacts are expected to grow in importance in the future, especially climate change and habitat degradation. The spatial identification of hot spots highlighted the ecological importance of most of the western Mediterranean shelves (and in particular, the Strait of Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well.

This abstract has been translated to other languages (File S1).

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The Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats

Introduction Part I. The Development of Deep-Sea Biology, The Physical Environment and Methods of Study: 1. Historical aspects 2. The physical environment of the deep-sea 3. Methods of study of the organisms of the deep-sea floor Part II. Organisms of the Deep-Sea Benthic Boundary: 4. The megafauna 5. Smaller animals Part III. Patterns in Space: 6. Small-scale spatial patterns 7. Abundance and size structure of the deep-sea benthos 8. The diversity gradient 9. Depth-related patterns in community composition 10. Zoogeography, speciation and the origins of deep-sea fauna Part IV. Processes Patterns in Time: 11. Food resources, energetics and feeding strategies 12. Metabolic processes: microbial ecology at the deep-sea bed 13. Reproduction, recruitment and growth of deep-sea organisms 14. Animal sediment relations in the deep-sea Part V. Parallel Systems and Anthropogenic Effects: 15. Deep-sea hydrothermal vents and cold seeps 16. Anthropogenic impacts: man's effects on the deep-sea.

Deep-Sea Biology: A Natural History of Organisms at the Deep-Sea Floor

The environmental sensitivies of cold-water corals and their associated biota are likely to be determined by the natural variability of the cold-water coral reef environment. The sensitivity of reef biota to sedimentation and resuspension events is largely unknown and the influence of seasonal phytodetrital deposition is poorly understood. Here we describe the use of a benthic photolander to monitor this variability by the Sula Ridge reef complex on the mid-Norwegian continental shelf and from the Galway carbonate mound in the Porcupine Seabight. The photolander provides a platform for time-lapse digital and film cameras to image the seabed while recording the current regime and optical characteristics (light transmission, backscatter and fluorescence) of the seawater. In its first two deployments carried out in 2001 and 2002 by the Sula Ridge the lander recorded a dynamic environment around the reef site with a tidal current regime and periods of sediment resuspension. Current speeds by the Sula Ridge reef complex reached a maximum of 28 cm s−1 and 70 cm s−1 on the Galway carbonate mound, reinforcing much speculation about the dependence of these communities on current-swept conditions. Seabed photographs show intense feeding activity of echiuran worms (Bonellia viridis) near the Sula Ridge reef complex pointing to rapid bioturbation of the sediment. Fish were recorded sheltering near sponges that had colonised glacial dropstones. Longer term monitoring in situ is needed for study of seasonal change, to identify functional roles of associated fauna and to monitor potential coral spawning events. Benthic landers and seafloor observatories have great potential in these areas. Only with a better understanding of the natural variability of the cold-water coral environment can informed decisions about the environmental sensitivity of cold-water coral reefs and their management be made.

Monitoring environmental variability around cold-water coral reefs: the use of a benthic photolander and the potential of seafloor observatories

The relationships of environmental factors with measures of macrobenthic community diversity were examined for the total fauna, and for polychaetes only, from 40 bathyal stations in the North Atlantic, eastern Pacific and Indian Oceans (154–3400 m). Stepwise multiple regression revealed that depth, latitude, sediment organic-carbon content and bottom-water oxygen concentration are significant factors that together explained 52–87% of the variation in macrobenthic species richness (E[s100]), the Shannon–Wiener index (H′), dominance (D), and evenness (J′). Percent sand and percent clay were not significant factors. After removal of depth and latitudinal effects, oxygen and organic-carbon concentrations combined accounted for 47, 67, 52 and 32% of residual variation in macrobenthic E(s100), H′, D, and J′, respectively. Organic carbon exhibited a stronger relationship than oxygen to measures of community evenness, and appeared to have more explanatory power for polychaetes than total macrobenthos. When only stations with oxygen Examination of rarefaction curves for Indo-Pacific stations reveals that total macrobenthos, polychaetes, crustaceans and molluscs all exhibit reduced species richness within oxygen minimum zones (OMZs). However, representation under conditions of hypoxia varies among taxa, with polychaetes being most tolerant. Molluscs and crustaceans often (but not always) exhibit few individuals and species in OMZs, and sometimes disappear altogether, contributing to reduced macrobenthic diversity and elevated dominance in these settings. The linear negative relationship observed between bathyal species richness and sediment organic-carbon content (used here as a proxy for food availability) may represent the right side (more productive half) of the hump-shaped, diversity–productivity curve reported in other systems. These analyses suggest there are potentially strong influences of organic matter and oxygen on the diversity and composition of bathyal macrobenthos, especially in the Indo-Pacific Ocean.

Relationships between oxygen, organic matter and the diversity of bathyal macrofauna

Investigations of macrobenthos were carried out within and beneath the oxygen minimum zone (OMZ, E[S 100 ], H′ and J′ across the transect; grain size and % TOC did not yield significant regressions. Pigments, assumed to reflect food availability and possibly oxygen effects on organic matter preservation, were negatively correlated with species richness and evenness, and positively correlated with dominance. The reverse was true for water depth. Macrobenthic patterns of calcification and lifestyle within the Oman margin OMZ (0.13–0.3 ml l−1) match the dysaerobic biofacies of paleo-environmental reconstruction models.

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Macrobenthic community structure within and beneath the oxygen minimum zone, NW Arabian Sea

Foreword: the value of diversity Crispin Tickell 1. Marine biodiversity in its global context M. H. Williamson 2. Gradients in marine biodiversity J. S. Gray 3. Pelagic biodiversity M. V. Angel 4. Biological diversity in oceanic macrozooplankton: more than counting species A. C. Pierrot-Bults 5. Large scale patterns of species diversity in the deep sea benthos M. A. Rex, R. J. Etter and C. T. Stuart 6. Diversity, latitude and time: patterns in the shallow sea A. Clarke and J. A. Crame 7. High benthic species diversity in deep-sea sediments: the importance of hydrodynamics J. D. Gage 8. Diversity and structure of tropical Indo-Pacific benthic communities: relation to regimes of nutrient input J. D. Taylor 9. Why are coral reef communities so diverse? A. J. Kohn 10. The biodiversity of coral reef fishes R. F. G. Ormond and C. M. Roberts 11. The historical component of marine taxonomic diversity gradients J. A. Crame and A. Clarke 12. Population genetics and demography of marine species J. E. Neigel 13. Discovering unrecognised diversity among marine molluscs J. Grahame, S. L. Hull, P. J. Mill and R. Hemingway 14. Ecosystem function at low biodiversity - the Baltic example R. Elmgren and C. Hill 15. Land-seascape diversity of the US east coast coastal zone with particular reference to estuaries G. C. Ray, B. P. Hayden, M. G. McCormick-Ray and T. M. Smith 16. The development of mariculture and its implications for biodiversity M. C. M. Beveridge, L. G. Ross and J. A. Stewart 17. Protecting marine biodiversity and integrated coastal zone management J. S. H. Pullen 18. Conserving biodiversity in north-east Atlantic marine ecosystems K. Hiscock Index.

John D. Gage

Papers

Deep-Sea Biology: A Natural History of Organisms at the Deep-Sea Floor

Monitoring environmental variability around cold-water coral reefs: the use of a benthic photolander and the potential of seafloor observatories

Relationships between oxygen, organic matter and the diversity of bathyal macrofauna

Macrobenthic community structure within and beneath the oxygen minimum zone, NW Arabian Sea

Marine Biodiversity: Patterns and Processes