松花江流域大型底栖动物群落结构与水质评价

【目的】松花江流域是中国最早的工业基地之一,其水生态环境遭到严重破坏,环境保护工作面临巨大挑战。开展松花江流域水质评价及典型生物类群多样性状况调查,可为松花江流域生态系统的保护和修复提供依据。【方法】于2016年7月调查整个松花江流域近岸的大型底栖动物群落组成和测定水质理化指标,开展其水质理化特征评价和生物指数评价,并探讨底栖动物群落分布与水环境因子间的关系。【结果】理化指标评价结果显示,南源松花江水质状况最差,处于中度污染;北源松花江处于轻度污染;梧桐河水质最好,处于良好状态。松花江流域3个河段的底栖动物群落结构存在空间差异性。另外,梧桐河的物种多样性最高,北源松花江次之,南源松花江最低。溶解氧和营养元素K的浓度是驱动底栖动物群落组成发生显著性差异的主要环境因子。生物指数评价结果显示,3个河段水质均处于轻度污染状态。【结论】松花江流域水质处于轻度到中度污染状态。有机污染是松花江流域面临的主要水质环境问题,对松花江流域底栖动物群落结构产生了显著影响。因此,控制有机质的输入是维持松花江流域水生态系统平衡的重要举措之一。     

European common frog (Rana temporaria) recolonized Switzerland from multiple glacial refugia in northern Italy via trans‐ and circum‐Alpine routes

The high mountain ranges of Western Europe had a profound effect on the biotic recolonization of Europe from glacial refugia. The Alps present a particularly interesting case because they form an absolute barrier to dispersal for most taxa, obstructing recolonization from multiple refugia in northern Italy. Here, we investigate the effect of the European Alps on the phylogeographic history of the European common frog Rana temporaria. Based on partial cytochrome b and COXI sequences from Switzerland, we find two mitochondrial lineages roughly north and south of the Alpine ridge, with contact zones between them in eastern and western Switzerland. The northern haplogroup falls within the previously identified Western European haplogroup, while the southern haplogroup is unique to Switzerland. We find that the lineages diverged ~110 kya, at approximately the onset of the last glacial glaciation; this indicates that they are from different glacial refugia. Phylogenetic analyses suggest that the northern and southern haplogroups colonized Switzerland via trans‐ and circum‐Alpine routes from at least two separate refugia in northern Italy. Our results illustrate how a complex recolonization history of the central European Alps can arise from the semi‐permeable barrier created by high mountains.     

Human time in tree rings

‘Human time’ means time in the context of human culture and activities. It is shown how ‘human time’ is biologically archived in and dendrochronologically extracted from tree rings. For illustration, examples in the late medieval Hanseatic city of Lübeck are selected.     

Nutrient fluxes in intertidal communities of a South European lagoon (Ria Formosa) – similarities and differences with a northern Wadden Sea bay (Sylt-Rømø Bay)

During an annual cycle, flux rates of oxygen, nitrate, nitrite, ammonium, phosphate and silicate were measured in light and dark bell jars at three sites in Ria Formosa (Algarve, Portugal) enclosing either a natural macrophytic community (macroalgae on sand or mud, a seagrass bed of Zostera noltii) or bare sediments. The results are compared with a preceeding study in which the same bell jar technique has been applied in the Sylt-Rømø Bay of the northern Wadden Sea. Nitrate flux was mainly directed from the water column to the benthic communities in Ria Formosa, as well as in the Sylt-Rømø Bay. However, nitrate uptake was higher in the northern, more eutrophic study area. In Ria Formosa, nutrient concentrations were lower than in the Sylt-Rømø Bay possibly due to strong water exchange with Atlantic waters. High temperatures and strong insolation had a greater impact on nitrate fluxes in Ria Formosa than in the Sylt-Rømø Bay. Bioturbating macrofauna increased ammonium efflux in the Sylt- Rømø Bay while this effect was not as pronounced in the Ria Formosa study sites. Benthic phosphate uptake dominated in the Ria Formosa and was correlated to initial phosphate concentrations in incoming waters. At both study sites, oxygen and nutrient fluxes were correlated with temperature. Additionally, flux rates were strongly influenced by biotic components and levels of eutrophication. A literature survey showed that mainly in temperate regions, material fluxes increase with temperature, whereas in warmer areas, ammonium and phosphate fluxes between sediment and water were generally lower.     

Glacial refugia and recolonization pathways in the brown seaweed Fucus serratus

The last glacial maximum (20,000-18,000 years ago) dramatically affected extant distributions of virtually all northern European biota. Locations of refugia and postglacial recolonization pathways were examined in Fucus serratus (Heterokontophyta; Fucaceae) using a highly variable intergenic spacer developed from the complete mitochondrial genome of Fucus vesiculosus. Over 1,500 samples from the entire range of F. serratus were analysed using fluorescent single strand conformation polymorphism. A total of 28 mtDNA haplotypes was identified and sequenced. Three refugia were recognized based on high haplotype diversities and the presence of endemic haplotypes: southwest Ireland, the northern Brittany-Hurd Deep area of the English Channel, and the northwest Iberian Peninsula. The Irish refugium was the source for a recolonization sweep involving a single haplotype via northern Scotland and throughout Scandinavia, whereas recolonization from the Brittany-Hurd Deep refugium was more limited, probably because of unsuitable soft-bottom habitat in the Bay of Biscay and along the Belgian and Dutch coasts. The Iberian populations reflect a remnant refugium at the present-day southern boundary of the species range. A generalized skyline plot suggested exponential population expansion beginning in the mid-Pleistocene with maximal growth during the Eems interglacial 128,000-67,000 years ago, implying that the last glacial maximum mainly shaped population distributions rather than demography.     

Depth-related patterns in benthic community condition along an estuarine gradient in Chesapeake Bay,USA

We tested whether macrobenthic community condition varies significantly with water depth in a variety of regions of Chesapeake Bay, USA. Benthic community condition was characterized using the Benthic Index of Biotic Integrity (B-IBI) previously developed for the Bay. We applied two water depth thresholds intended to emphasize the ecological importance and/or anthropogenic impacts upon shallow-water regions. The first threshold of 2 m emphasizes restoring and supporting submerged aquatic vegetation while the second threshold of 4 m emphasizes the zone of maximum anthropogenic impact upon natural ecosystem functions. An a priori expectation is that benthic community condition may worsen with increasing depth, specifically in regions (1) where water column stratification at depth results in prolonged low dissolved oxygen levels or (2) where net deposition at depth results in higher levels of hydrophobic, sediment-bound contaminants. Samples collected from a major tributary of Chesapeake Bay, the York River estuary, spanned the entire salinity range from tidal freshwater to polyhaline. We also tested the shallow-water depth thresholds using data from the Virginia Mainstem of Chesapeake Bay and the Southern Branch of the Elizabeth River. These two polyhaline regions are characterized as having the best and worst benthic community condition in Chesapeake Bay. At the scale of the entire tidal York River system, there were no significant differences in benthic community condition with water depth. However, two salinity regions, low mesohaline and polyhaline, had significant depth effects with the shallowest water depth zone significantly different from the other two depth regions. For the low mesohaline region benthic community condition was worse at the shallowest depth and for the polyhaline region the shallowest depth was better comparing the three depth regions. No depth-related differences in the B-IBI were found for the two additional Chesapeake Bay strata, the Virginia Mainstem characterized with the lowest levels of benthic community degradation and for the Southern branch of the Elizabeth River, characterized by the highest levels of benthic community degradation. We conclude that the ecological state of Chesapeake Bay subtidal benthic communities is adequately characterized by randomly sampling all depths without further stratification into shallow and deeper regions.     

Deep-sea ecosystem variability of the Aegean Sea during the past 22 kyr as revealed by Benthic Foraminifera

Specific responses of the regional deep-sea ecosystems to climatic and oceanographic processes during the last 22 kyr are revealed by benthic foraminiferal faunas from two cores in the northern and southern Aegean Sea. Under glacial boundary conditions, high-diversity benthic foraminiferal faunas and elevated benthic foraminiferal numbers indicate enhanced organic matter availability and well-ventilated deep-water masses in the whole Aegean Sea. The glacial termination is accompanied by significant fluctuations in productivity and deep-water ventilation. In the northern Aegean Sea, meltwater inflow from mountain glaciers during the Bølling/Allerød warm period resulted in a restriction of local deep-water formation, as mirrored by a dominance of bolivinids. During the deposition of sapropel S1, drops in benthic foraminiferal number and diversity are more significant in the southern Aegean Sea when compared to the north. This suggests the persistence of local deep-water formation in the northern Aegean Sea during S1 deposition. In addition, faunal fluctuations within S1 at both sites suggest the repeated influence of short-term cooling events on the re-ventilation and re-colonization of Aegean deep-sea ecosystems. During the middle and late Holocene, benthic foraminiferal faunas document the establishment of oligotrophic and well-ventilated conditions in the southern Aegean Sea. The corresponding faunas from the northern Aegean Sea reflect generally mesotrophic conditions and variable deep-water oxygenation. During the entire Holocene, the deep-sea ecosystems of this region responded very sensitively to short-term changes in humidity and temperature. These abrupt climate changes controlled the inflow of nutrients from rivers and the Black Sea and the formation of local deep-water masses.     

Eocene -Oligocene paleoceanography of the deep Bay of Biscay: Benthic foraminiferal evidence

A major change in benthic foraminiferal assemblages occurred in the deep Bay of Biscay (> 3 km water; DSDP Sites 119, and Site 400A) between early middle Eocene and earliest Oligocene. Predominant Eocene deep-sea taxa (Nuttallides truempyi, Clinapertina spp., Abyssamina spp.) and associated rarer species became extinct in this interval. These extinctions were followed by an increase in abundance of bathymetrically wide-ranging and stratigraphically long-ranging taxa: Globocassidulina subglobosa, Oridorsalis spp., Gyroidinoides spp., and the Cibicidoides ungerianus plexus. The extinctions cannot be dated precisely from the stratigraphic record recovered to date in the Bay of Biscay; however, the replacement of the N. truempyi-dominated assemblage has been noted previously in the deep South Atlantic/Caribbean as occurring near the middle/late Eocene boundary. Other than the decrease in abundance and extinction of N. truempyi, no major abundance changes are noted within the Eocene at the shallower Site 401 (～ 2 km water) in the Bay of Biscay. During the Oligocene, Nuttallides umbonifera replaced the Eocene species N. truempyi as the predominant deep-sea benthic foraminifera, reaching peak abundance in the middle Oligocene at Sites 119 and Site 400A. In the modern oceans, the abundance ot N. umbonifera is positively correlated with increased corrosiveness of bottom water, while at Site 119 the abundance of Nuttallides spp. is negatively correlated with δ ¹³C values in benthic foraminifera. As lower δ ¹³C values are often associated with older water masses, large numbers of Nuttallides spp. are thought to reflect older, and more corrosive bottom water. The faunal data and oxygen and carbon isotopic data are compared with a circulation model derived from North Atlantic seismic stratigraphic studies to show that old, warm, corrosive, and sluggish Eocene bottom water was replaced by younger, colder, less corrosive, more vigorously circulating bottom water of northern origin by the early Oligocene. Faunal and isotopic data suggest that bottom water became older and more corrosive again in the middle Oligocene, reflecting a reduction in circulation that can also be inferred from the seismic record in the nearby Rockall Plateau region.     

Dinoflagellate cyst distribution in surface sediments along the south-western Mexican coast (14.76° N to 24.75°N)

In this study, we explore the relationship between the modern assemblages of organic-walled dinoflagellate cysts and sea-surface conditions (temperature, salinity, primary productivity) and water depth and distance to the coast. Statistical treatments were performed on 95 surface sediment samples from sites located along the south-western Mexican coast (14.76° N to 24.75°N). Redundancy analysis (RDA) illustrates that the principal parameters correlated with the regional cyst distribution are the distance to the coast and the productivity in the upper water column, which is closely related to upwelling intensity. Empirical observations coupled with RDA provide insight into the spatial coverage of some cyst taxa produced by dinoflagellate species potentially responsible for harmful algal blooms along the coast. They also allow the recognition of four zones of assemblages, which are linked to the upwelling intensity and the productivity and characterize La Paz Bay, the south-western Mexican margin (from 15.95° N to 23.11° N), the northern part of the Gulf of Tehuantepec and the southern part of the Gulf of Tehuantepec.     

Molecular phylogeography of the microturbellarian Monocelis lineata (Platyhelminthes: Proseriata) in the North‐East Atlantic

Monocelis lineata is a complex of cryptic species (three in the Mediterranean and one in the Atlantic) widespread in midlittoral habitats. Throughout the range, populations with or without an ocular pigmented shield are found. We investigated the genetic structure of the North‐East Atlantic populations with the aim of shedding light on their phylogeography and reconstructing possible patterns of recolonization after the Würmian glaciation. Fourteen samples were investigated using cytochrome c oxidase subunit I (COI) and 13 by inter‐simple sequence repeats (ISSRs). COI did not exhibit a clear pattern of decreased genetic diversity along a latitudinal gradient. Populations from Ferrol (Spain), Doolin (Ireland), and Helsingør (Denmark) showed a higher genetic variability, whereas a reduction in the number of haplotypes was found at the northernmost edge of the distribution and in northern Ireland and Scotland. Two genetically differentiated areas (southern Europe and south‐western Ireland versus northern Atlantic) were revealed by ISSR data. The results obtained provided evidence of three refugia (Iberian Peninsula, south‐western Ireland, and North Sea), and the occurrence of secondary contacts that shaped the genetic variability of some of the populations examined. Two different recolonization pathways of north‐western Europe during the post‐Würmian glaciations have been detected. Furthermore, ISSR analysis provided evidence of genetic divergence among populations with and without pigmented eyespot, suggesting the action of ecological differentiation. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 117–135.     

Current distribution and potential expansion of the harmful benthic dinoflagellate Ostreopsis cf. siamensis towards the warming waters of the Bay of Biscay,North-East Atlantic

In a future scenario of increasing temperatures in North-Atlantic waters, the risk associated with the expansion of the harmful, benthic dinoflagellate Ostreopsis cf. siamensis has to be evaluated and monitored. Microscopy observations and spatio-temporal surveys of environmental DNA (eDNA) were associated with Lagrangian particle dispersal simulations to: (i) establish the current colonization of the species in the Bay of Biscay, (ii) assess the spatial connectivity among sampling zones that explain this distribution, and (iii) identify the sentinel zones to monitor future expansion. Throughout a sampling campaign carried out in August to September 2018, microscope analysis showed that the species develops in the south-east of the bay where optimal temperatures foster blooms. Quantitative PCR analyses revealed its presence across almost the whole bay to the western English Channel. An eDNA time-series collected on plastic samplers showed that the species occurs in the bay from April to September. Due to the water circulation, colonization of the whole bay from the southern blooming zones is explained by inter-site connectivity. Key areas in the middle of the bay permit continuous dispersal connectivity towards the north. These key areas are proposed as sentinel zones to monitor O. cf. siamensis invasions towards the presumably warming water of the North-East Atlantic.     

Glacial history and colonization of Europe by the blue tit Parus caeruleus

Mitochondrial control region sequences from European populations of the blue tit Parus caeruleus were used to reveal the Pleistocene history and the post-glacial recolonization of Europe by the species. The southern subspecies, P. c. ogliastrae was found to represent a stable population with isolation-by-distance structure harboring a lot of genetic variation, and the northern subspecies P. c. caeruleus a recently bottlenecked and expanded population. We suggest that after the last Ice Ages, the subspecies have colonized Europe from two different southern refuges following previously proposed general recolonization routes from the Balkans to northern and Central Europe, and from the Iberian Peninsula north- and eastwards. The two subspecies form a wide secondary contact zone extending from southern Spain to southern France.     

Assessment of Littoral Benthic Invertebrate Communities at the Land–Water Interface in Lakes Recovering from Severe Acid- and Metal-Damage

Benthic invertebrate communities within confluence sites, or areas of sediment deposition, are shaped by the input of catchment products including coarse woody debris, organic and inorganic particulates, and contaminants, but these sites also appear to be potential “hotspots” where recolonization of severely damaged ecosystems begins. Two species of leaf packs and a sweep netting technique were used to assess benthic invertebrate communities across a gradient of 14 confluence sites in 3 recovering lakes near the copper and nickel smelters in Sudbury, Canada. Environmental variables including delta habitat composition, delta area and length, and composition of deposited materials were used to detect spatial patterns in littoral benthic invertebrate communities. Benthic invertebrate community relationships with water chemistry were also assessed. Partial redundancy analysis (pRDA) showed that all sampling methods detected similar gradients of increasing invertebrate community richness and diversity as area and length of the sediment delta and the surface organic matter abundance increased. Two-way nested ANOVAs showed significant differences (p < .05) in taxa richness and diversity metrics among sites. Of the three methods, the benthic invertebrate community measurements from the birch leaf packs provided the strongest correlations with measures of organic matter inputs or habitat characteristics of the confluence zones. These correlations suggest that tree planting in riparian areas, or organic matter or macrophyte additions to littoral zones, may enhance littoral benthic invertebrate richness and diversity in acid and metal damaged lakes.     

Annual cycles of macro-invertebrates of a river in southern Ghana

The results of a quantitative study of the benthic invertebrates of a riffle area in the upper reaches of the Pawmpawm River in the forest of southern Ghana are presented. The investigation was carried out over a period of 17 months with a Surber Sampler. The seasonal fauna changes are discussed in relation to changes both in water flow and in the vegetational substrate, and a model for the succession of recolonization of the river after the resumption of flow is outlined. The earliest colonizers of the river were primary consumers, Chironomidae, Centroptilum and Simulium., which were followed after a few weeks (once a mat of vegetation had become established) by the carnivorous Cheumatopsyche (Trichoptera) and Centroptiloides (Ephemeroptera). After 2 to 3 months, the attached vegetation matured and was able to support a greater diversity of fauna. The strategy of survival in intermittent tropical rivers is discussed and it is concluded that recolonization from eggs laid by flying adults is the most important method.     

Impact of late Quaternary environmental changes on deep-sea benthic foraminiferal faunas of the Red Sea

Fluctuations in abundance, diversity and species composition of benthic foraminifera from two sites of the northern and southern Red Sea indicate strong variability of deep-sea ecosystems during the last four glacial to interglacial cycles. In total, five and four different benthic foraminiferal assemblages have been identified in the northern core and southern core, respectively. Comparison with recent faunas from the Red Sea and adjacent oceans allowed the reconstruction of temporal changes in deep-water ventilation, salinity and food availability at the seafloor. Generally, the abundance of infaunal and miliolid taxa increase during glacial intervals indicating increased organic matter fluxes, oxygen decrease and salinity increase in deep waters during these times. These fluctuations are attributed to enhanced oxygen consumption rates and temporarily reduced deep-water formation in the northern Red Sea during glacial intervals. The recorded environmental changes are a reflection of both high- and low-latitude climate changes. The northern Red Sea is mainly influenced by glacio-eustatic sea level fluctuations that control deep-water formation rates and by mid-latitude climate changes of the Mediterranean region that control surface productivity. In contrast, deep-sea ecosystem variability of the southern Red Sea is additionally influenced by low-latitude climate changes attributed to the NE monsoon intensity that drives the inflow of nutrient-rich surface waters from the Gulf of Aden. These results demonstrate the high sensitivity of deep-sea ecosystems of the Red Sea to both global and regional climate changes.     

Species diversity and distribution of aquatic macrophytes in the Northern Quark, Baltic Sea

The occurrence of aquatic macrophytes was studied in a northern transition area of the Baltic Sea; the Northern Quark, Gulf of Bothnia. In the area there is a gradual, marked change in environmental conditions, the most prominent of which is a decrease in salinity from 5.0% in the Bothnian Sea to 3.5% in the Bothnian Bay. In all, 40 species of macrophytes were observed; 10 fucophyceans, 10 bangiophyceans, 8 chlorophyceans, 3 charophyceans, 1 tribophycean, 1 nostocophycean, 6 phanerogams and 1 water moss. 26 of the observed species were of marine and 14 of lacustrine origin. There was a clear change in species composition and community structure from south to north over the area. The vegetation at the southernmost localities had a marine character, with belt-forming Fucus vesiculosus and a comparatively diverse flora of macroalgae. Further north, an ephemeral, lacustrine vegetation dominated by benthic diatoms and Cladophora aegagropila prevailed. The ratio marine: lacustrine species decreased from 4.2 to 1 when comparing a southern and a northern sub-area of the Northern Quark. The species observed include 57 % of the marine macrophytes noted in the Aland and Archipelago Seas (N Baltic Proper) during the past two decades. Two marine species, Aglaothamnion roseum and Ahnfeltia plicata , are reported for the first time from the Northern Quark. This comprises a northern extension of their distribution limit with approximately 300 km.     

Zeitgeschichte der Humangenetik in Deutschland

Together with the German Society for Human Genetics (Deutsche Gesellschaft für Humangenetik, GfH) a team of researchers from the Department for the History, Philosophy, and Ethics of Medicine of Heinrich Heine University Düsseldorf in cooperation with the Department for History of Medicine and Science Studies of the University of Lübeck has begun a research project on the history of human genetics in Germany since the 1970s. We employ the method of oral history to add to printed secondary and primary sources. In this contribution we present the project, its research questions and situate it in the historiography of human genetics in Germany. Approaches to writing contemporary history of medicine and challenges of conducting and analyzing expert interviews are discussed.     

A benthic perspective in assessing the ecological status of estuaries: The case of the Mondego estuary (Portugal)

In transitional waters the process of defining reference conditions (in the scope of the WFD) must account for the natural great variability of such environments. Therefore, stretches reflecting different physical–chemical and biological conditions throughout the system should be defined in order to correctly establish benthic specific reference conditions. Both salinity and sediment structure are major factors controlling physical–chemical conditions and therefore organisms’ distribution within an estuary. These environmental variables (salinity, sediment grain size composition and organic matter content) patterns were studied in the Mondego estuary and some clear gradients emerged. Also, ecological indices (AMBI, Margalef and Shannon-Wiener) were applied to subtidal benthic communities of the Mondego estuary and, generally, there was not only evidence of a decrease in diversity in the estuary from the downstream section towards its inner parts, but also differences were found between areas of distinct sediment composition. After comparing environmental patterns with biodiversity trends, the information was used to define homogeneous sectors along a temperate estuary in Portugal. In the Mondego estuary six zones, covering the main physical gradients affecting benthic communities, were defined: four in the northern arm and two in southern arm. Zones established will allow future determination of benthic reference conditions adjusted for each of the sectors, according to their characteristics, and consequently the conditions they provide for benthic assemblages settlement.     

Population structure of the South American Estuarine crab, Chasmagnathus granulatus (Brachyura: Varunidae) near the southern limit of its geographical distribution: comparison with northern populations

Crabs are among the most conspicuous and ecologically important invertebrates of the large intertidal zones that characterize estuarine and protected coastal areas in temperate regions. The habitat, population structure and breeding cycle of Chasmagnathus granulatus (Brachyura: Varunidae), a semiterrestrial burrowing crab endemic to the warm temperate coasts of the Southwestern Atlantic, were studied in San Antonio Bay (Argentina), near the southern limit of its range. San Antonio Bay has no freshwater input, winter is relatively colder, and summer warmer, than northern habitats of this species. Crabs lived both in vegetated and unvegetated zones, but density and sex ratio varied among dates and zones. The maximum observed density was 136 crabs/m² , the maximum carapace width (CW) was 32 mm (males) and 29.8 mm (females), ovigerous females were found only in November and January, and the smallest ovigerous female measured 17 mm CW. The population structure, spatial distribution, and recruitment pattern of C. granulatusdid not differ between San Antonio Bay and northern habitats. The higher density, smaller maximum size and shorter reproductive cycle observed in San Antonio cannot be atributed to changes associated with a latitudinal cline and other factors, such as thermal amplitude and food availability, need to be studied.     

Oxygen minimum expansion in the Sulu Sea,western equatorial Pacific,during the last glacial low stand of sea level

The Sulu Sea in the western equatorial Pacific is presently a shallowly-silled, dysaerobic, deep-marine basin. Deep waters in the Sulu Sea are ventilated through a single sill at 420 m depth which connects it to the China Sea. Benthic and planktonic foraminiferal oxygen and carbon isotope records, benthic and planktonic foraminiferal census data and total organic carbon measurements have been used to evaluate changes in water mass conditions in the Sulu Sea between the last glacial maximum (18,000 yrs. B.P.) and the present day.An increase in the abundance of the planktonic foraminiferaNeogloboquadrina dutertrei and relatively light planktonic foraminiferal δ¹⁸O values suggest that during the last glacial maximum surface water salinities were reduced in the Sulu Sea. Enhanced isolation of the basin due to glacio-eustatic lowering of sea level and reduced surface salinities resulted in stagnation of deep water and an expansion of the mid-water oxygen minimum layer. Increased organic carbon preservation at mid-water depths occurs at this time. Benthic carbon isotope data and an increase in the abundance of benthic foraminiferal species considered to prefer low oxygen environments support the conclusion of an oxygen-minimum expansion at mid-water depths during the last glacial maximum. At water depths greater than 4000 m, bottom waters appear to have maintained some degree of oxygenation during the last glacial maximum. Stronger Pacific Ocean trade winds at this time may have caused the influx of denser Celebes Sea surface water into the southern part of the Sulu Sea. The slow sinking of this water would have then ventilated bottom waters in this part of the basin.At the transition from glacial to interglacial conditions, rising sea level caused denser water to flow over the deepest sill into the Sulu Sea. Vertical circulation increased, resulting in a greater downward flux of oxygen and a dissipation of the oxygen minimum. Continued post-glacial sea level rise caused periodic ventilation of deep water until the present dysaerobic conditions were established.