G. Douglas Haffner

Photoferrotrophs thrive in an Archean Ocean analogue

Considerable discussion surrounds the potential role of anoxygenic phototrophic Fe(II)-oxidizing bacteria in both the genesis of Banded Iron Formations (BIFs) and early marine productivity. However, anoxygenic phototrophs have yet to be identified in modern environments with comparable chemistry and physical structure to the ancient Fe(II)-rich (ferruginous) oceans from which BIFs deposited. Lake Matano, Indonesia, the eighth deepest lake in the world, is such an environment. Here, sulfate is scarce (<20 μmol·liter−1), and it is completely removed by sulfate reduction within the deep, Fe(II)-rich chemocline. The sulfide produced is efficiently scavenged by the formation and precipitation of FeS, thereby maintaining very low sulfide concentrations within the chemocline and the deep ferruginous bottom waters. Low productivity in the surface water allows sunlight to penetrate to the >100-m-deep chemocline. Within this sulfide-poor, Fe(II)-rich, illuminated chemocline, we find a populous assemblage of anoxygenic phototrophic green sulfur bacteria (GSB). These GSB represent a large component of the Lake Matano phototrophic community, and bacteriochlorophyll e, a pigment produced by low-light-adapted GSB, is nearly as abundant as chlorophyll a in the lakes euphotic surface waters. The dearth of sulfide in the chemocline requires that the GSB are sustained by phototrophic oxidation of Fe(II), which is in abundant supply. By analogy, we propose that similar microbial communities, including populations of sulfate reducers and photoferrotrophic GSB, likely populated the chemoclines of ancient ferruginous oceans, driving the genesis of BIFs and fueling early marine productivity.

The methane cycle in ferruginous Lake Matano

In Lake Matano, Indonesia, the worlds largest known ferruginous basin, more than 50% of authigenic organic matter is degraded through methanogenesis, despite high abundances of Fe (hydr)oxides in the lake sediments. Biogenic CH₄ accumulates to high concentrations (up to 1.4 mmol L⁻¹) in the anoxic bottom waters, which contain a total of 7.4 × 10⁵ tons of CH₄. Profiles of dissolved inorganic carbon (ΣCO₂) and carbon isotopes (δ¹³C) show that CH₄ is oxidized in the vicinity of the persistent pycnocline and that some of this CH₄ is likely oxidized anaerobically. The dearth of NO₃⁻ and SO₄²⁻ in Lake Matano waters suggests that anaerobic methane oxidation may be coupled to the reduction of Fe (and/or Mn) (hydr)oxides. Thermodynamic considerations reveal that CH₄ oxidation coupled to Fe(III) or Mn(III/IV) reduction would yield sufficient free energy to support microbial growth at the substrate levels present in Lake Matano. Flux calculations imply that Fe and Mn must be recycled several times directly within the water column to balance the upward flux of CH₄. 16S gene cloning identified methanogens in the anoxic water column, and these methanogens belong to groups capable of both acetoclastic and hydrogenotrophic methanogenesis. We find that methane is important in C cycling, even in this very Fe-rich environment. Such Fe-rich environments are rare on Earth today, but they are analogous to conditions in the ferruginous oceans thought to prevail during much of the Archean Eon. By analogy, methanogens and methanotrophs could have formed an important part of the Archean Ocean ecosystem.

UNIQUE ISLAND HABITATS MAY BE THREATENED BY DOUBLE-CRESTED CORMORANTS

Abstract Double-crested cormorant (Phalacrocorax auritus) populations on the Great Lakes expanded greatly during the past 2 decades. On Lake Erie, the number of breeding cormorants increased from 174 birds (87 nests) in 1979 to 26,542 (13,271 nests) in 2000. In 2000, 81% of the breeding population was on 2 western-basin islands (East Sister and Middle Islands). The plant communities on these islands represent some of the last remnants of Carolinian vegetation in Canada. Our study is the first to quantitatively assess the relationship between the distribution of nesting cormorants and forest health. On East Sister Island, 2 measures of forest cover were obtained using infrared aerial photographs and ground-based measurements of leaf area index. These measures of forest cover were correlated (rs = 0.70, P < 0.001), which validated the use of remotely sensed data to assess forest cover. Cormorant nest density was negatively correlated with tree cover on both East Sister and Middle Islands. Temporal comparisons of Middle Island data indicated a reduction in tree cover from 1995 to 2001, and these reductions coincided with a large increase in the islands cormorant population. Although correlational in nature, our results suggest that cormorants may be detrimentally affecting island forests.

The relative importance of species invasions and sediment disturbance in regulating chemical dynamics in western Lake Erie

PCB congener concentrations were measured in aquatic biota and sediment from the western basin of Lake Erie during 1993–1994 and 1996–1997. Between these time periods the round goby (Neogobius melanostomus) invaded and proliferated in the basin and mean annual particulate organic carbon (POC), dissolved organic carbon (DOC) and PCB congener concentrations in sediment changed. The objectives of this study were to use a food web bioaccumulation model and field data to quantify the relative importance of the round goby, POC, DOC and chemical concentration in sediment, to PCB congener levels in aquatic biota prior to (1993–1994) and since (1996–1997) the invasion of the basin by round gobies. The predicted effects of round gobies on PCB congener transfer, mediated through alterations in food web structure, were small increases (range 2–6%) in PCB burdens of pelagic fish species such as alewife and walleye. Larger increases (range 8–19%) in PCB burdens were predicted for benthic feeding sport fish species such as yellow perch and largemouth bass. Small decreases (range 1–5%) in PCB congener concentrations in fish were predicted to result from decreases in bioavailable concentrations of PCBs in water. Bioavailable concentrations of PCBs in water were predicted to decrease as a result of observed changes in POC and DOC concentrations. However, in all cases predicted changes in PCB concentrations in fish, resulting from changes in food web structure and POC and DOC, were smaller than those predicted from measured increases in PCB congener concentrations in sediment between 1993 and 1994 and 1996–1997. Increased concentrations of PCBs in sediment were attributed to exposure of older and more heavily contaminanted sediments from turbulence caused by higher wind speeds in 1996–1997 compared to 1993–1994.

The Distribution of 42 PCBs, Including Three Coplanar Congeners, in the Food Web of the Western Basin of Lake Erie

Non-ortho substituted PCBs, IUPAC numbers 77, 126, and 169, along with 39 other PCB congeners were quantified in samples of Lake Erie sediment and biota during the summer of 1991. Many PCB congeners were found at elevated levels, and biomagnification was apparent in all congeners but was more predominant in congeners with relatively high octanol-water partition coefficients (log Kow > 6.0). PCA analysis suggested that most PCB congeners had similar distributions in the Lake Erie food web, although congeners with very high Kows and coplanar congeners IUPAC # 77, 126, and 169 were found to have different distributions. Non-parametric statistics were used to determine if significant differences in concentration of selected PCB congeners existed among species and among tissues. Congener 126 was found primarily in benthic fish and top predators, whereas there was no significant differences in the concentrations of congener 77 in fish species of the benthic and pelagic food web. Congener 169 was found at very low concentrations in the food web of Lake Erie. There were also significant differences in concentrations of coplanar PCBs among liver, egg, and muscle tissues, but trends were not consistent among all the species examined. As significant differences were observed in the distribution of PCB congeners in the Lake Erie food web “total PCB” might not be an adequate estimation of the toxicological hazards associated with PCB accumulation. It is evident that the dynamics of individual congeners, in particular the coplanar PCBs, need to be accurately assessed in order to predict the environmental hazard of PCBs.

A river-wide survey of polychlorinated biphenyls (PCBs), polycylic aromatic hydrocarbons (PAHs), and selected organochlorine pesticide residues in sediments of the Detroit River - 1999

ABSTRACT The spatial distribution of hydrophobic organic contaminants, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and octachlorostyrene (OCS) in sediments of the Detroit River was established using data from a 1999 river-wide survey. The survey employed a stratified random sampling design that divided the river into six geostatistical zones consisting of upper, middle, and lower U.S. and equivalent Canadian river reaches. Organic carbon normalized OCS sediment concentrations demonstrated no significant differences between U.S. or Canadian sediments or upstream/downstream gradients suggesting that OCS is derived primarily from sources upstream of the Detroit River. In contrast, sum PCBs and sum PAHs were significantly elevated at U.S. as compared to Canadian stations and demonstrated significant increasing upstream/downstream gradients in organic carbon normalized sediment contamination. The upper and middle U.S. river reaches contained a number of near-shore stations with high localized PCB and PAH sediment concentrations suggesting multiple inputs along the upper U.S. portion of the river. Consistent with past surveys, wide-spread sediment contamination of PCBs and PAHs continues to be observed in the highly industrialized Trenton Channel and downstream of Grosse Isle. Threshold effect level (TEL) sediment quality guidelines for PAHs and PCBs were exceeded in 92.6 and 77.8%, respectively, of stations in Trenton Channel and downstream of Grosse Isle. This large reservoir of degraded sediments in the lower U.S. river reach has the potential to enter Lake Erie during sediment disturbance events and likely contributes to gentoxic stress and increased bioaccumulation of PCBs in resident benthos, fish, and wildlife.

Resource‐based adaptive divergence in the freshwater fish Telmatherina from Lake Matano, Indonesia

Adaptive radiations are an important source of biodiversity, but resolving which ecological pressures seed these processes in natural systems remains difficult. Here the adaptive radiation among Telmatherina, a genus of freshwater fish endemic to an ancient lake in central Sulawesi, Indonesia, was examined to determine its causal root. We demonstrate that all Telmatherina in this lake can be categorized into three lineages each possessing specialized skull shapes and pharyngeal jaw bones allowing them to exploit different resources. These data demonstrate a natural example of how resource partitioning has likely initiated adaptive radiation in a resource limited environment.

Bioaccumulation of Chlorinated Hydrocarbons by the Mayfly (Hexagenia Limbata) in Lake St. Clair

Concentrations of six PCB congeners, octachlorostyrene, and penta- and hexachlorobenzene were measured in sediments and in resident in situ mayfly populations (Hexagenia limbata) at a location in Lake St. Clair from July to September, 1987. Observed mayfly/sediment concentration ratios varied from 0.14 for pentachlorobenzene to 0.71 for PCB-153, and were linearly correlated with Kow when expressed on a logarithmic basis. A chemical equilibrium model of sediment-organism interactions predicting a mayfly/sediment concentration ratio of 0.5 is shown to be in good agreement with the field observations, particularly for the higher Kow compounds. A dynamic model gives a more realistic description of organic chemical uptake and bioaccumulation in the mayfly. However, when calibrated by rate constants derived from laboratory experiments, this model tends to overestimate mayfly/sediment concentration ratios by approximately a factor of 10.

Distribution of Heavy Metals in Sediments of the Detroit River

ABSTRACT The spatial distribution of 17 metals in the sediments of the Detroit River was established using metal concentrations from a river-wide survey. The survey (1999) was based on a stratified random sampling design that divided the river into upper, middle, and lower reaches and subsequently into U.S. and Canadian sides of the river. Results based on strong extraction, using concentrated acids, revealed that the Lowest Effect Level (LEL) for As, Cd, Cu, and Hg was exceeded at more than 75% of sampling sites and the Severe Effect Level (SEL) for As at 16.2% of sites. Most of the metals were homogenously distributed throughout reaches of the river, although sites with elevated concentrations were localized mainly along the middle and lower reaches as a result of a pattern of contamination sources and geographic complexity of the river, especially a spatial/temporal variability in water flow. A comparison of the results of a strong to a weak extraction (cold 5% acetic acid, to assess metal bioavailability) revealed two groups of sediment type. The first group with a “high” weak/strong ratio (bioavailable metals; about 1 for Ca, Mg, Na and from 0.6 to 0.4 for the rest of metals) was observed at sites with low flow velocities below 0.4 m s−1. The “low” ratio (non-bioavailable metals; 0.25 for Ca, Mg, Na and from 0.15 to 0.05 for other metals) was observed at sites with flow velocities greater than 0.6 m s−1. The data indicate that the sediment conditions, dependent on flow distribution, regulate not only the distribution of heavy metals but also can regulate metal bioavailability.

Biomonitoring of Bioavailable PAH and PCB Water Concentrations in the Detroit River Using the Freshwater Mussel, Elliptio complanata

Abstract Bioavailable PAH and PCB water concentrations were evaluated along the Detroit River using the freshwater mussel, Elliptio complanata . Bioavailable concentrations ranged from 64.2 to 620.7 ng/L for ΣPAHs and 0.1 to 3.0 ng/L for ΣPCBs. A principal component analysis grouped contaminants primarily on the basis of hydrophobicity, indicating that physical-chemical properties regulate the relative concentrations and distributions of PAHs and PCBs among sites. Concentrations of the more hydrophobic PAHs and more water soluble PCBs were present at elevated concentrations at the Detroit Edison Generating Station, in the Trenton Channel. Elevated PAH levels were also detected at three other sites: West Windsor Sewage Treatment Plant, Grassy Island, and Ambassador Bridge, along the Detroit River. This study supports the conclusion that E. complanata is an effective biomonitor of water PAH and PCB concentrations in aquatic systems. In addition, the results indicate that areas of high contamination in the Detroit River are a result of continued loading of these chemicals into the Great Lakes system.