SPATIAL,SEASONAL AND INTER‐ANNUAL VARIABILITY IN ENVIRONMENTAL CHARACTERISTICS AND PHYTOPLANKTON STANDING STOCK OF THE TEMPERATE,LOWLAND RIDEAU RIVER,ONTARIO, CANADA

Chlorophyll‐a, biomass and living unit concentrations were monitored across the Rideau River over a three‐year period. The results show that a continuum of changing physical, biological and chemical conditions altered the phytoplankton standing stock of the Rideau River. From year to year, weather conditions and anthropogenic impacts like discharge control had a clear effect on the phytoplankton community. The year 2000, with poorer growing conditions and higher flow regime, had a significantly lower phytoplankton standing stock across all the stations. Based on hydrological characteristics, the Rideau River was divided into four distinct reaches, and ANOVAs show a clear reach effect on phytoplankton standing stock. The invasive zebra mussel consistently reduced the phytoplankton standing stock downstream from the main invasion zone over the three years, although there were differences between years. The non‐native zebra mussel further altered the phosphorus–phytoplankton standing stock relationship. Nutrients, ions and metals were not clearly correlated to standing stock in this three‐year study, although the significant effect of the four reaches suggested that environmental characteristics other than hydrological conditions may have an influence. Phytoplankton development downstream followed a polynomial model. However, unlike the stages of development characterizing many river continuum models, the pattern observed in the present study was affected by zebra mussels followed by anthropogenic impacts of discharge control and eutrophication. This and other studies on the Rideau River highlight the significance of scale (spatial and temporal) and metrics selected when evaluating environmental impacts and developing watershed models. Copyright © 2011 John Wiley & Sons, Ltd.     

Circular Rep encoding single stranded (CRESS) DNA virus-like sequences detected in quagga mussels (Dreissena rostriformis bugensis) and sediments from the central Lake Michigan benthos

Circular Rep Encoding Single Stranded (CRESS) DNA viruses are a diverse group of viruses that have been identified in both terrestrial and aquatic ecosystems. Recent work in the Laurentian Great Lakes characterized the ecology and diversity of CRESS-DNA viruses associated with amphipods, Diporeia spp. In the last 20 years the Lake Michigan benthos has changed considerably with drastic population declines of Diporeia spp. concurrent with an increase in invasive quagga mussel (Dreissena rostriformis bugensis) abundance. The purpose of this study was to characterize CRESS-DNA virus-like elements (VLES; which could represent complete, partial/defective, endogenized or satellite viruses) associated with both invasive quagga mussels and in sediment collected in central Lake Michigan. Viral metagenomic libraries were prepared from two size classes (>25 mm and <15 mm shell length) of Lake Michigan quagga mussels and for two different sediment layers (136 mm and 290 mm below the lake floor) in a sediment core extracted from the lake. Viral metagenomes were different between quagga mussels and sediment cores. Nine VLE sequences were present in both the quagga mussel tissues and the sediment core layers analyzed. Cs¹³⁷ radiometric dating results indicate that these VLEs were present in the sediment prior to arrival of quagga mussels in Lake Michigan. These data suggest quagga mussels may interact with CRESS-DNA VLEs and algal DNA VLEs historically present in the Lake Michigan benthos. Overall, these data suggest that quagga mussels interacted with CRESS-DNA VLES present in Lake Michigan benthos since at least 1952.     

Explaining Spatial Patterns of Mussel Beds in a Northern California River: The Role of Flood Disturbance and Spawning Salmon

Despite considerable effort, predicting habitat preferences for freshwater mussels has remained elusive. This study identified four parameters that correlate with bed stability to decipher fine‐scale spatial patterning of habitat use by the western pearl shell mussel (Margaritifera falcata) in the Trinity River of Northern California. Logistic regression analysis correctly predicted the occurrence of 83% of mussel bed areas based on water depth, velocity, substrate size, and distance to the stream bank as estimated from hydrodynamic modelling of low‐flow conditions. These parameters coincide with bed stability at high flow and provide support for the ‘refugia hypothesis’. Our data clearly demonstrate that mussel beds occupied the most stable portions of the riverbed; however, habitat was partitioned with one of their primary host fish, Chinook salmon (Oncorhynchus tshawytscha), a species that also requires stable bed areas for spawning. Mussels occupied significantly deeper and lower velocity areas that were closer to the streambank compared with spawning salmon, but where habitats directly overlapped (30% of potential mussel habitat) mussels were excluded because the act of spawning disturbs the riverbed. By necessity, mussels and salmon must co‐exist, but results of this study indicate that they compete for stable bed areas that may be limiting in dynamic river systems. Copyright © 2015 John Wiley & Sons, Ltd.     

Diets of the benthic amphipod Diporeia in southern Lake Michigan before and after the dreissenid invasion

Diporeia spp. were a key component of the Great Lakes benthos, converting the pelagic algal rain to secondary production, which is critical for Great Lakes fishes. However, Diporeia declines since the 1980s have been rapid and widespread. While there are temporal relationships between Diporeia declines and spread of zebra and quagga mussels, establishing a mechanistic link has been difficult. Diporeia declines may result from competition for food resources with dreissenid mussels; however, conflicting evidence suggests food limitation may not be the direct link. To test food limitation, we analyzed gut contents of Diporeia collected between the 1980s and 2009 from two deep (>100 m) and one nearshore station (~50 m depth) in southern Lake Michigan. We further analyzed sediment cores from the same stations to resolve relationships among food resources, Diporeia diet, and diet selectivity during pre- and post-dreissenid invasion. In spring, pre-dreissenid Diporeia fed selectively and exclusively on large (Stephanodiscus) and filamentous centric diatoms (Aulacoseira). Diporeia diets showed significant shifts during the 2000s to greater proportions of small centric and araphid diatoms, coincident with Diporeia declines and offshore expansion of quagga mussels. Sediment cores recorded declines in Aulacoseira and large Stephanodiscus from 1960 to 2009 and increases in small centrics after dreissenid introduction. Accounting for high selectivity in springtime Diporeia diets, community changes in sediment records are consistent with changes observed in Diporeia diets and suggest Diporeia declines have been exacerbated by a shift from more nutritious and highly preferred diatom species to less nutritious and negatively selected species.     

Ecological tracers track changes in bird diets and possible routes of exposure to Type E Botulism

Dreissenid mussels have become important components of the Great Lakes biological community since their introduction in the 1980s, but much remains to be understood regarding their effect on energy and nutrient flows in pelagic systems. Here, we report a new method that tracks incorporation of resources of molluskan origin into food webs used by aquatic birds. Biochemical tracers (fatty acids and stable carbon isotopes) are used to characterize species associated with pelagic and benthic food webs in Lake Ontario. Our focus is on the polymethylene-interrupted fatty acids (PMI-FAs) because previous research identified mollusks as their primary source. We found that PMI-FA mass fractions were greater in organisms associated with benthic (e.g. round goby) versus pelagic (e.g. alewife) food webs. Double-crested cormorants that had recently consumed benthic prey fish, i.e. goby, had greater proportions of PMI-FAs in their blood plasma than birds which showed no signs of recent goby ingestion. We did not detect an increase in mass fractions of PMI-FAs in cryogenically archived cormorant eggs following expansion of dreissenid mussels in Lake Ontario. However, following the introduction and expansion of round goby in the lake, PMI-FAs were detected at greater levels in cormorant eggs. These results illustrate how only after dreissenid mussel-facilitated establishment of round goby was the full extent of exotic species disruption of food webs manifested in fish-eating birds. These food web changes may be contributing to negative impacts on aquatic birds exemplified by the emergence of Botulism Type E as a significant mortality factor in this ecosystem.     

The Zebra Mussel Dreissena polymorpha Found in North America in 1986 and 1987

The zebra mussel Dreissena polymorpha was first detected in the western basin of Lake Erie, Ontario, Canada, on natural gas wellheads and well markers between April and November 1986. It was found again in 1987 on the north shore of Lake Erie in a water treatment plant, and in vessel fouling. The population increased in Lake Erie in 1988. Dreissena may have spread from Lake Erie to Lake St. Clair, where it was then discovered on 1 June 1988.     

贻贝仿生组织粘合剂研究进展

在组织创伤修复中,常需要应用传统的固定材料或组织粘合剂,虽然组织粘合剂较传统的固定材料有诸多优势,但仍然不能满足临床应用的要求。海洋生物贻贝能够分泌富含多巴的蛋白质,可在潮湿环境中牢固粘附于各种材料的表面。目前,已开展了大量关于贻贝粘附机理的研究,受此优异粘附性能的启发,国内外许多课题组开展了仿生组织粘合材料的研究,并在相关领域探索其应用。介绍了贻贝足盘粘附机理及贻贝仿生粘合材料的研究现状,并展望了该领域未来的发展方向。     

Nanostructured Polymeric Coatings Based on Chitosan and Dopamine‐Modified Hyaluronic Acid for Biomedical Applications

In a marine environment, specific proteins are secreted by mussels and used as a bioglue to stick to a surface. These mussel proteins present an unusual amino acid 3,4‐dihydroxyphenylalanine (known as DOPA). The outstanding adhesive properties of these materials in the sea harsh conditions have been attributed to the presence of the catechol groups present in DOPA. Inspired by the structure and composition of these adhesive proteins, dopamine‐modified hyaluronic acid (HA‐DN) prepared by carbodiimide chemistry is used to form thin and surface‐adherent dopamine films. This conjugate was characterized by distinct techniques, such as nuclear magnetic resonance and ultraviolet spectrophotometry. Multilayer films are developed based on chitosan and HA‐DN to form polymeric coatings using the layer‐by‐layer methodology. The nanostructured films formation is monitored by quartz crystal microbalance. The film surface is characterized by atomic force microscopy and scanning electron microscopy. Water contact angle measurements are also conducted. The adhesion properties are analyzed showing that the nanostructured films with dopamine promote an improved adhesion. In vitro tests show an enhanced cell adhesion, proliferation and viability for the biomimetic films with catechol groups, demonstrating their potential to be used in distinct biomedical applications.     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.