Impact of bleached kraft pulp mill effluent on benthic community structure in relation to environmental factors

In this study, we assessed the impact of bleachedkraft pulp mill effluent (BKME) on the distributionand composition of benthic communities at JackfishBay, Lake Superior. Sediment samples were collectedfrom 44 stations from which several environmentalvariables (extractable organic chlorine [EOCl],metals, organic carbon, particle size, secchi depth,and water depth) and benthic community compositionwere determined. Relationships between environmentalvariables and benthic community structure wereassessed using canonical correspondence analysis(CCA). CCA revealed two distinct biological gradientsat Jackfish Bay, the first associated with degradedbottom sediments and nutrient enrichment and thesecond associated with water depth. Both gradientsrevealed three distinct regions at Jackfish Bay: 1) anarea of highly degraded sediments, located 300–1200 mbelow the outfall, 2) a small, mesotrophic (nutrientenriched) area adjacent to this zone, and 3) remainingareas of Jackfish Bay, including the internalreference sites in Tunnel Bay. Sediments in theimpaired region contained high concentrations oforganic matter (7–21% as loss on ignition [LOI]) andEOCl (up to 5200 mg/kg dw); together these variablesaccounted for 73% of the variation associated withthe first canonical axis of the CCA. This region wasdominated by the oligochaetes Tubifex tubifexand Limnodrilus hoffmeisteri (64–100% of thebenthic community). Sediments in the second regionwere characterized by an abundant and diverse benthiccommunity comprised of benthic harpacticoids,Chironomidae, and oligochaetes. Stations outside ofthese two regions were characterized by a benthiccommunity similar in composition to that expected foroligotrophic Lake Superior waters, including Diporiea sp., Stylodrilus heringianus, Mysis relicta, Sphaerium, Pisidium and benthicharpacticoids. Based on a Monte Carlo significancetest, benthic community structure was significantly(p = 0.01) related to the environmental variablescomprising the first axis of the CCA. Water depth wasthe most important explanatory variable associatedwith the second axis of the CCA; both taxa richnessand abundance declined significantly with increasingdepth. The comprehensive approach employed in thisstudy clearly delineated the occurrence and degree ofimpact on the benthic environment and may be useful infuture risk assessments of sites affected byanthropogenic activity.     

Patterns of Fish Growth along a Residential Development Gradient in North Temperate Lakes

Residential development of lakeshores is expected to change a variety of key lake features that include increased nutrient loading, increased invasion rate of nonnative species, increased exploitation rates of fishes by anglers, and alteration of littoral habitats. All of these factors may alter the capacity of lakes to support productive native fish populations. Fourteen north temperate lakes were surveyed to examine how growth rates of two common fish species (bluegill sunfish, Lepomis macrochirus; largemouth bass, Micropterus salmoides) varied along a residential development gradient. Size-specific growth rates for both species were negatively correlated with the degree of lakeshore residential development, although this trend was not statistically significant for largemouth bass. On average, annual growth rates for bluegill sunfish were 2.6 times lower in heavily developed lakes than in undeveloped lakes. This effect of lakeshore development on fish growth was not size specific for bluegills between 60 and 140 mm in total length. An index of population production rate that accounted for both the size-specific growth rate and the size distribution of fishes showed that bluegill populations were approximately 2.3 times less productive in highly developed lakes than in undeveloped lakes. Our results suggest that extensive residential development of lakeshores may reduce the fish production capacity of aquatic ecosystems. Received 29 April 1999; Accepted 26 October 1999.     

Seasonal phosphorus release from exposed,re-inundated littoral sediments of two Australian reservoirs

Water levels in many reservoirs typically fluctuate seasonally, but the effects of re-inundation of exposed sediments on nutrient dynamics in the water column are poorly known. This study concerns the seasonal differences in the potential of sediments from two Australian reservoirs, after having undergone different degrees of in situ desiccation, to release P under aerobic conditions. Differences were determined between biotic and abiotic P release, and results were also examined in relation to sediment chemistry. The two reservoirs, Carcoar Dam and Lake Rowlands, demonstrated different patterns of P release involving an interactive complex of P release mechanisms. Sediment chemistry at the reservoir margins was important because of the higher concentrations of N, P, Fe and Mn in Lake Rowlands. Physical and chemical processes influenced P uptake and release due to desiccation and oxidation of sediments and were of greater importance in Carcoar Dam. Abiotic P release from sterilised sediments was greater than from unsterilised sediments where both biotic and abiotic processes were apparent. Biotic P uptake and release were especially marked in Lake Rowlands where large macrophyte beds provided a rich source of organic matter. Little seasonal difference in P release was detected. The increased P release from dried sediments has ramifications for internal P loading into reservoirs and for the calculation of P budgets. For managers of reservoirs where large expanses of sediment are exposed during drying, it may be better to maintain high water levels, where possible, during the summer by modifying drawdown practices.     

Effects of the emergent macrophyte Juncus effusus L. on the chemical composition of interstitial water and bacterial productivity

Release of oxygen from the roots ofaquatic macrophytes into anaerobic sediments canaffect the quantity of interstitial dissolved organicmatter and nutrients that are available to bacteria. Nutrient and dissolved organic carbon (DOC)concentrations were compared between subsurface(interstitial) waters of unvegetated sediments andsediments among stands of the emergent herbaceousmacrophyte Juncus effusus L. in a lotic wetlandecosystem. Concentrations of inorganic nitrogen(NH₄ ⁺, NO₃ ^-, and NO₂ ^-)were greater from sediments of the unvegetatedcompared to the vegetated zone. DOC concentrations ofinterstitial waters were greater in sediments of theunvegetated zone both in the winter and springcompared to those from the vegetated zone. AlthoughDOC concentrations in hydrosoils collected from bothzones increased from winter to spring, bacterialproductivity per mg DOC in spring decreased comparedto winter. Greater initial bacterial productivityoccurred on DOM collected from the vegetated comparedto the unvegetated zone in winter samples (days 1 and4), with increased bacterial productivity on samplescollected from the unvegetated zone at the end of thestudy (day 20). Bacterial productivity wassignificantly greater on all sampling days on DOM fromvegetated samples compared to unvegetated samples. In nutrient enrichment experiments, bacterialproductivity was significantly increased (p < 0.05)with phosphorus but not nitrogen only amendments.     

Assessing the vulnerability of endemic diatom species in Lake Baikal to predicted future climate change: a multivariate approach

Diatoms in Lake Baikal exhibit significant spatial variation, related to prevailing climate, lake morphology and fluvial input into the lake. Here we have assessed the threats to endemic planktonic diatom species (through the development of empirical models), which form a major component of primary production within the lake. Multivariate techniques employed include redundancy analysis (RDA) and Huisman–Olff–Fresco (HOF) models. Our analyses suggest that eight environmental variables were significant in explaining diatom distribution across the lake, and in order of importance these are snow thickness on the ice, water depth, duration of days with white ice, suspended matter in the lake, days of total ice duration, temperature of the water surface in July, concentration of zooplankton and suspended organic matter. Impacts on dominant phytoplankton diatom species are highlighted using t‐value biplots. Predictions of future climate change on Lake Baikal are likely to result in shorter periods of ice cover, decreased snow cover across the lake in spring, increased fluvial input into the lake, and an increase in the intensification of surface water stratification during summer months. All these factors are likely to impact negatively on the slow‐growing, cold‐water endemics such as Aulacoseira baicalensis and Cyclotella minuta, which currently dominate diatom assemblages. Instead, taxa that are only intermittently abundant, at present, in offshore areas (e.g. Stephanodiscus meyerii) are likely to become more frequent. However, given the climatic gradient across the lake, the timing and extent of changes in community structure are likely to vary. Moreover, palaeolimnological records show that Lake Baikal diatom assemblages have been dynamic throughout the Holocene, with both endemic and cosmopolitan species exhibiting periods of dominance. Effects of climate change on the entire lake ecosystem may yet be profound as the structure of the pelagic food web may change from one based on endemic diatom taxa to one dominated by nondiatom picoplankton, and as limnological functioning (e.g. stratification and mixing) affects deepwater oxygen availability, nutrient cycling and trophic linkages.     

Visual conditions and habitat shape the coloration of the Eurasian perch (Perca fluviatilis L.): a trade‐off between camouflage and communication?

In theory, selection for effective camouflage (i.e. dull coloration) in fish should be strongest when the conditions for visual predation are most favourable, such as in structurally simple pelagic habitats. By contrast, in more sheltered (e.g. littoral) habitats, selection may favour effective intra‐specific communication (i.e. bright coloration) (at the expense of crypsis). Poor transparency, as in highly humic waters, should constrain colour adaptations. We investigated phenotypic variation in body coloration of Eurasian perch (Perca fluviatilis L.) in littoral and pelagic habitats of four humic boreal lakes. Perch from the most transparent lake had the lightest and less coloured belly and perch were more colourful in the littoral habitats than in the pelagic areas, with the pattern being clearest in the most transparent lake. In addition, perch in the most transparent lake exhibited sexual dichromatism, with males having a more colourful belly than the females, whereas no indications of sexual dichromatism were found in more humic lakes. Moreover, in the most transparent lake, the condition of fish correlated with bright belly coloration in the littoral, but with dull belly coloration in the pelagic habitat. The results obtained in the present study suggest that selection on perch coloration may differ between lakes as a result of visual properties of the water, and within lakes as a result of divergent selection for camouflage and communication in pelagic and littoral habitats. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 47–59.     

Probabilistic Risk Assessment and Risk Mapping of Sediment Metals in Sydney Harbour Embayments

Sediment metal concentrations in embayments of Sydney Harbour, acquired from the literature and from samples collected for this study, were used to generate contaminant probability density distributions using AQUARISK. The sediment metal concentrations often exceeded Australia's interim sediment quality guidelines. Similarly, estuarine spiked sediment toxicity test literature provided adverse biotic effects concentration data to generate species sensitivity distributions using AQUARISK. Although the harbor is subject to other inorganic and organic contamination, we have used sediment metals to demonstrate an approach for ecological risk mapping and environmental management prioritization. Sufficient spiked sediment toxicity test data were found for only three metals—Cd, Cu, and Zn—and some tests were likely to overestimate toxicity. The estimates of the hazardous concentration to 5% of species (the 50th percentile of the 95% species protection level) were 5, 12, and 40 mg/kg DW of total sediment metal for Cd, Cu, and Zn, respectively. These values were generally low when compared with the interim sediment quality guidelines due to the overestimation of toxic effects in the literature data. The parameters for the species sensitivity distributions have been combined with the measured sediment metal concentrations in Homebush Bay to generate risk maps of the estimated species impact for each metal as well as for all three metals collectively assuming proportional additivity. This has demonstrated the utility of comparing contaminants on a consistent scale—ecological risk.     

Upper Holocene dry land vegetation in the Moravian–Slovakian borderland (Czech and Slovak Republics)

Five pollen diagrams representing the upper Holocene vegetation and its anthropogenic changes are presented and evaluated. They come from small spring fens in the Czech (Moravian) and Slovak borderland. The northern part of the region (the Beskydy Mts) had natural, precultural forests with either coniferous trees (Picea abies and Abies alba) or mixed with Fagus sylvatica. In the southern part of the region (the Bílé Karpaty Mts) forests dominated by Fagus mixed with Acer, Fraxinus and Ulmus prevailed, whereas conifers were almost absent, although in a central, transitional region (northern Bílé Karpaty Mts) Abies was locally abundant in relatively humid places. Medieval colonisation deforested their lower areas and foothills in the course of the 11th–13th centuries and transformed the original mixed oak forests into fields and meadows, but the mountain forests were little affected. In the Beskydy Mts in the north, the Walachian colonisation of the 16th and 17th centuries transformed parts of the mountain forests into meadows, pasture and farmlands. Most remaining woodlands were transformed during the last two centuries into spruce plantations. In the Bílé Karpaty Mts in the south, the Walachian transformation of mountain forests had already started by the 15th century. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cusps and pipis on a sandy ocean beach in New South Wales

The effect of small-scale variation in beach morphology has been largely ignored in studies of beach macrofauna. This study examined the distribution and abundance of the large bivalve, Donax deltoides (commonly known as the ‘pipi’) in relation to beach cusps (rhythmically spaced undulations of the beachface consisting of scalloped bays and flanking horns on a scale of tens of metres). No differences were found in the abundance of pipis downshore of cusp horns versus cusp bays at any of three sites. In contrast, previous work on a relatively low-energy (reflective) beach reported greater abundances of bivalves below cusp bays than below cusp horns. Results suggest that the swash climate on the higher-energy (more dissipative) beach studied here produces weaker cusping and weaker patterns in the active or passive redistribution of beach fauna by swash action. Wider more dissipative beaches also allow beach macrofauna to remain on flatter parts of the beach, further below cusps than on reflective beaches. The more rigorous study design used here may also contribute to the difference in results between this study and previous studies. However, populations of pipis below cusp bays did contain a greater proportion of small individuals (≤20 mm length) than populations on cusp horns, suggesting some effect related to beach cusps. Small pipis live closer to the beach surface as they have shorter siphons and are subject to larger rates of dislodgement and movement from cusp horns to cusp bays by swash action than are large pipis. Future ecological studies of beaches with cusps should take beach cusps and the processes producing them into account as they may affect the distribution, abundance and the size distribution of beach invertebrates.     

Interannual patterns of water table height and groundwater derived nitrate in nearshore sediments

Nitrate concentration and microbial nitrogen transformations in ground-water-affected sediments of Great South Bay, NY were examined over several annual cycles. Nitrate concentrations are typically higher at 40 cm depth than at the surface, while salinity generally decreases with depth. Denitrification occurs through the sediment core and is organic substrate limited at depth while being nitrate limited near the sediment-water interface. Denitrification accounts for about 50% of the biological NO₃ ^- decrease between 40 and 15 cm depth interval. Higher than average annual rainfall during 1983 and 1984 was reflected in an elevated water table as well as lower Bay salinities. Conversely, extremely low rainfall occurred in 1985 and 1986, and the water table reached an extreme low in Sep. 1986. Interestingly, the amounts of nitrate in the sediment column of our primary station varied directly with water table height and, presumably, the discharge rate of nitrate enriched groundwater. We suggest that this may be a result of the more efficient removal of advected nitrate by denitrification during low flow conditions.