Phytoplankton assemblages in Lake Orta: has functional structure recovered in one of the largest acidic lakes in the world?

Lake Orta (Northern Italy) became one of the world’s largest acidic lakes, following industrial pollution, beginning in the late 1920s. Prior to pollution, Lake Orta supported a rich and diversified phytoplankton community dominated by diatoms, cyanobacteria and dinoflagellates. Their taxonomic composition was comparable to that of the nearby Lake Maggiore, which provides a useful reference comparison. After pollution, Lake Orta was so acidic and contaminated with trace metals that only a few tolerant phytoplankton species persisted, supplemented by sudden and short living outbursts of occasional colonists. The lake was limed in 1989-1990. This has permitted the gradual recovery of its chemistry and biology, and many phytoplankton species that inhabit Lake Maggiore are now re-appearing in Lake Orta. I tested the two hypotheses that Lakes Orta and Maggiore would now have a similar phytoplankton taxonomic assemblages, and similar diversity of functional groups given their similar morphometry, physical features and trophic states. The two hypotheses were tested by comparing the phytoplankton assemblages of lakes Maggiore and Orta for the first 10 years after liming, i.e. 1990 to 2001. Phytoplankton was classified according the Reynolds' Morpho Functional Groups and five diversity indices were calculated (<em>S</em>, number of units; <em>H</em>, Shannon-Wiener; <em>E</em>, evenness; <em>D</em>, dominance; <em>J</em>, equitability). SHE analysis (an analysis of diversity changes based on the relationship among species richness (S), H Index (H) and evenness (E)) was also carried out, in order to compare the long term trend of both functional groups and taxa biodiversity. Both taxonomic and the functional composition differed in the two lakes, likely because chemical quality have played a role in <em>taxa</em>selection. Moreover, it was quite clear that, during the first post-liming decade, Lake Orta’s phytoplankton was characterized by low diversity and evenness and by marked year-to-year fluctuations. However, SHE analysis showed that the colonization rate was higher in Lake Orta than in Lake Maggiore, and that the environmental modifications caused by the liming were opening new ecological niches, allowing some colonists to thrive in the changing, albeit still unusual chemical environment of the lake.<p> </p>

Benthonic foraminifera in the Upper Miocene Cruse Formation at Quinam Bay, Trinidad, western tropical Atlantic Ocean, and their palaeoenvironmental significance

The Upper Miocene Cruse Formation of Trinidad yields predominantly agglutinated foraminifera. The limited assemblage has previously hampered palaeoenvironmental interpretations. Twenty-two samples taken from a basal Cruse section at 0.5 m intervals from Quinam Bay (10°05′07.7″N, 61°45′04.7″W) yielded 2938 foraminifera in 33 species, almost all agglutinated. The absence of calcite-cemented agglutinants suggests post-mortem dissolution of calcareous specimens. Dominant Spirosigmoilinella compressa indicates lower bathyal to abyssal palaeodepths, although the low values of the information function H are typical of shallower water. Subdominant Haplophragmoides carinatus and Haplophragmoides sp. 1 indicate low dissolved oxygen levels. Diversities measured using species richness S and H were especially low in the lowest 3.5 m of the section. The proportional abundance of the dominant species in each sample, max(pi), indicated three subsections, being low in the middle of the section but higher at the top and bottom. SHE analysis indicated six abundance biozones (ABs) containing one to seven samples each. Of the three ABs with more than three samples, two had Type 1 community structures and one had a Type 0 community structure. ABs with one or two samples indicate that environmental change at the top of the interval with low diversity is rapid. This is reflected in a change from abundant morphotype M3a (surficial epifauna flattened) at the base of the section to abundant M4a (shallow infauna planispiral) with M4b (deep infaunal) towards the top, which shows a downward shift in the position of the redox front part way through the section.

Size Dependence in Assemblage Measures: Essentialism, Materialism, and “She” Analysis in Archaeology

"Assemblage" is a fundamental archaeological construct. By their composition, we interpret assemblages as expressions of activity or cultural identity. Yet they are not simple products of these factors alone but also of formation processes. Assemblages accumulated over varying spans, with varying combinations of tool types and discard rates. They are contexts for the playing out of complex relationships, not static types. This is a materialist view, against the essentialist view that assemblages are exemplars of ideal types (e.g., "base camps," "Quina Mousterian"). Materialism implies that their size and composition, fundamental assemblage characteristics, are correlated variables, not fixed properties, and that composition varies as size increases. I document size dependence consistent with materialism in Paleoindian and Paleolithic assemblages. Among ways to analyze size-dependent assemblage data, I apply "SHE analysis"—the joint study of assemblage richness, heterogeneity, and evenness—to gauge data’s fit to theoretical models. Archaeologists acknowledge size dependence, but we misapprehend it as a methodological bias of assemblage measures that must be suppressed when, in materialist perspective, it reveals meaningful relationships that an essentialist view cannot.

Determining Boundaries between Abundance Biozones Using Minimal Equipment

The areal extent of a biological community is usually determined using statistical techniques that only give reliable results where samples contain similar and high numbers of specimens. This paper presents a simple, inexpensive method for determining the geographical limits of biological communities applicable where adjacent samples contain widely differing numbers of specimens. The method is a development of SHE Analysis, which discerns boundaries between adjacent abundance biozones (ABs), an AB being an area with a distinct community structure. As originally conceived, SHEbi(SHE Analysis for the identification of Biozones) commences with species' absolute abundances and works best with large samples of equal sizes. If the variance in (per sample) is high, SHEbimay place AB boundaries in unexpected locations. A modification, based on proportional abundances, is developed here using species' proportional abundances () for each sample where is the number of specimens in theith species in the sample. For intertidal foraminifera from the Caroni Swamp, Trinidad, where , the number of specimens, fluctuates widely between samples, the modification (SHEbip) gives ecologically more sensible results than does traditional SHEbi.

Micro-to macro-scale foraminiferal distributions: the contributions of Martin A. Buzas

The research that Martin A. Buzas has published over the past more than 40 years has influenced us greatly. That research has many strands that cannot be dealt with in this short review. However, the theme of micro- to macroscale foraminiferal distributions is interwoven throughout Buzas's research career. Distributions are something that Buzas is very fond of. He was trained in statistics as well as foraminifera and so it was inevitable that he would combine his knowledge of statistical distributions with foraminiferal distributions at several different scales. He has studied the distribution of foraminifera at microscales, horizontally within a 10 cm² area of the sea floor or vertically, cm by cm within a 20 cm core. He has also worked at the mesoscale, quantifying, through the pioneering use of the General Linear Model, the relationship of foraminiferal distributions and environmental variables in space and time. This research led to the hypothesis of pulsating patches. He has worked at the macroscale with S. J. Culver, defining the distribution of benthic foraminiferal provinces, showing that all foraminiferal distributions, particularly around the coasts of North and Central America, belong to the same statistical distribution. Their work has documented the assembly and disassembly of communities and the latitudinal patterns of deep-sea benthic foraminiferal diversity in the Atlantic basin. Most recently, with his coauthor, mathematical statistician L. C. Hayek, Buzas has delved deep into the intricacies of species diversity and solved a 50 year-old supposedly intractable problem of mathematically relating species richness with species evenness. This work led to the introduction of new approaches to understanding community structure and recognizing boundaries between adjacent communities (SHE analysis). Many of us work long hours and publish many papers over our careers but few of us truly influence the fundamentals of our science. Marty Buzas is one micropaleontologist whose work will be of lasting significance.