Definitions of diversity. Measuring species diversity. Choosing an index and interpreting diversity measures. Sampling problems. Structural diversity. Applications of diversity measures. Summary.

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Ecological Diversity and its Measurement

Since 65 million years ago (Ma), Earth's climate has undergone a significant and complex evolution, the finer details of which are now coming to light through investigations of deep-sea sediment cores. This evolution includes gradual trends of warming and cooling driven by tectonic processes on time scales of 10(5) to 10(7) years, rhythmic or periodic cycles driven by orbital processes with 10(4)- to 10(6)-year cyclicity, and rare rapid aberrant shifts and extreme climate transients with durations of 10(3) to 10(5) years. Here, recent progress in defining the evolution of global climate over the Cenozoic Era is reviewed. We focus primarily on the periodic and anomalous components of variability over the early portion of this era, as constrained by the latest generation of deep-sea isotope records. We also consider how this improved perspective has led to the recognition of previously unforeseen mechanisms for altering climate.

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Trends, Rhythms, and Aberrations in Global Climate 65 Ma to Present

Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change. Historical abundances of large consumer species were fantastically large in comparison with recent observations. Paleoecological, archaeological, and historical data show that time lags of decades to centuries occurred between the onset of overfishing and consequent changes in ecological communities, because unfished species of similar trophic level assumed the ecological roles of overfished species until they too were overfished or died of epidemic diseases related to overcrowding. Retrospective data not only help to clarify underlying causes and rates of ecological change, but they also demonstrate achievable goals for restoration and management of coastal ecosystems that could not even be contemplated based on the limited perspective of recent observations alone.

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Historical overfishing and the recent collapse of coastal ecosystems.

Interactions between organisms are a major determinant of the distribution and abundance of species. Ecology textbooks (e.g., Ricklefs 1984, Krebs 1985, Begon et al. 1990) summarise these important interactions as intra- and interspecific competition for abiotic and biotic resources, predation, parasitism and mutualism. Conspicuously lacking from the list of key processes in most text books is the role that many organisms play in the creation, modification and maintenance of habitats. These activities do not involve direct trophic interactions between species, but they are nevertheless important and common. The ecological literature is rich in examples of habitat modification by organisms, some of which have been extensively studied (e.g. Thayer 1979, Naiman et al. 1988).

Organisms as ecosystem engineers

The management and conservation of the world's oceans require synthesis of spatial data on the distribution and intensity of human activities and the overlap of their impacts on marine ecosystems. We developed an ecosystem-specific, multiscale spatial model to synthesize 17 global data sets of anthropogenic drivers of ecological change for 20 marine ecosystems. Our analysis indicates that no area is unaffected by human influence and that a large fraction (41%) is strongly affected by multiple drivers. However, large areas of relatively little human impact remain, particularly near the poles. The analytical process and resulting maps provide flexible tools for regional and global efforts to allocate conservation resources; to implement ecosystem-based management; and to inform marine spatial planning, education, and basic research.

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A Global Map of Human Impact on Marine Ecosystems

Reconstruction of productivity from the sedimentary record

Pioneers of Marine Geology

EXTRACT (SEE PDF FOR FULL ABSTRACT):

Torrey pine (Pinus torreyana Parry ex Carr.) has one of the most limited geographical ranges and population size in the Pinus genus; it is present only on Santa Rosa Island and on the coast between San Diego and Del Mar, where our research was conducted. A 168-year chronology (1827-1994) was developed using 28 increment cores extracted from 15 living and 2 dead stranding trees at Torrey Pines State Reserve, San Diego, California. ... The spatial correlation with western North America winter and spring precipitation, as well as with published tree-ring chronologies, indicates a connection with the American Southwest. Global correlation maps with winter sea level pressure and sea surface temperature are consistent with the hypothesis that San Diego precipitation is affected by a southerly displaced North Pacific storm track and by warmer water farther south, both leading to higher transport of lower latitude moisture.

Long-term response of Torrey pine to coastal climate: precipitation, temperature, and fog

In paleoclimatic reconstruction, fossil planktonic Foraminifera usually are related to ancient surface-water conditions. Processes on the ocean floor, however, are able to alter faunal composition drastically. Ten core samples from various depths were taken in the Santa Barbara basin which is anaerobic below a sill depth of about 480 m. Sixteen samples were analyzed for their microfossil content, in four size fractions. In each size fraction there is a pronounced difference in composition between samples above and below sill depth. The anaerobic, black, laminated sediments obtained below sill depth contain numerous species and specimens, including very fragile forms such a Hastigerina digitata. Fragments are almost absent; pelagic gastropods and pelecypods (aragonite) are plentiful, as are thin-walled calcareous benthonic Foraminifera. Just above sill depth, sediments are dark green and homogeneous, suggesting moderate aeration. The percentages of Globoquadrina dutertrei and of Globigerina pachyderma s.s. are much greater there than in the anaerobic samples. Fragments of both planktonic and benthonic Foraminifera are abundant. Thin-walled benthonic Foraminifera are much scarcer than in the deeper samples; aragonitic shells are virtually absent. Well above sill depth sediments are light green and homogeneous and appear well aerated. Both planktonic and benthonic foraminiferal numbers are greatly reduced and G. dutertrei strongly dominates all but the finest fraction. Fecal pellets are abundant. There are several possible causes for the pronounced change in fossil fauna across the anaerobic-aerated boundary: (1) changes in supply, (2) mechanical destruction by benthonic organisms, and (3) chemical dissolution. A change in supply from the overlying water is unlikely, because the effects of the aeration boundary do not extend into the productive zone. Mechanical destruction by benthonic animals is possible in the aerated zone. The siliceous skeletons of diatoms and Radiolaria, however, are much less affected by the aeration boundary than are calcareous fossils, which suggests that chemical dissolution is the most important factor. Two mechanisms may be responsible: (1) production of CO2 by the oxygenation of organic matter in the aerated zone, and (2) a more vigorous exchange of interstitial solutions with bottom water by burrowing activity. These two effects of bottom aeration should enhance calcite solution. The study of the distribution of the resistant Foraminifera, such as G. dutertrei, G. pachyderma s.s., G. End_Page 468------------------------------ truncatulinoides, and G. inflata, in ancient Californian sediments should lead to a better understanding of paleobasin oceanography by making it possible to determine sill depths and oxygen minimum distributions. Such studies have obvious applications in the determination of petroleum source rocks, because organic material is preserved in anaerobic conditions but destroyed in aerated sediments. End_of_Article - Last_Page 469------------

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Anaerobic Basin Sedimentation and Differential Preservation of Planktonic Foraminifera: ABSTRACT

From simple suggestions sometimes spring great accomplishments. For Wolfgang Berger the beginning was a suggestion from his doctoral advisor, Fred Phleger, who said, in response to a question about what Wolf might pursue for a dissertation, “study planktonic foraminifera.”

At the time the suggestion probably would not have been of interest to a geophysics or geochemistry student, but luckily for all of us, Wolfs early training was in paleontology and stratigraphy, and he took Fred's suggestion. The result has been a rich flow of ideas about the formation and preservation of biogenic sediments in the deep-sea carbonate dissolution, climatic change, global ocean productivity, and the Cenozoic ocean.

Wolfgang H Berger

Papers

Reconstruction of productivity from the sedimentary record

Pioneers of Marine Geology

Long-term response of Torrey pine to coastal climate: precipitation, temperature, and fog

Anaerobic Basin Sedimentation and Differential Preservation of Planktonic Foraminifera: ABSTRACT

1988 Ewing Medal to Wolfgang H. Berger