Effect of Mytilus coruscus selective filtration on phytoplankton assemblages

The feeding selectivity of bivalves can play an important role in shaping the structure of phytoplankton communities of natural waters. This could be particularly true in waters with intensive bivalves farming, like Sungo Bay, Northern China. Understanding the role of bivalve feeding behavior is important for assessing how the dense cultivation of bivalves may affect phytoplankton community composition and food web structure in farm areas. In this study, we investigated the feeding selectivity of blue mussel Mytilus coruscus on natural phytoplankton assemblages in Sungo Bay using both optical microscopy and HPLC-pigment analysis. Results showed that cryptophytes dominated the phytoplankton community and made up 66.1% of the total phytoplankton abundance. A comparison of phytoplankton composition between natural and filtered seawater showed that M. coruscus preferred cryptophytes and dinoflagellates than Chaetoceros spp. and Skeletonema spp. Cryptophytes were not detected in gut contents by microscopic observation, while their marker pigment alloxanthin was present, suggesting they were also consumed by M. coruscus and can be readily digested. This highlights the shortcomings of microscopic methods and the significance of HPLC-pigment analysis in obtaining a comprehensive understanding of feeding selectivity of bivalves. The proportions of Chaetoceros spp. and Skeletonema spp. in gut contents were significantly lower than their proportions in the seawater, and contrastingly, the proportions of Cocconeis spp. and Pinnularia spp. showed opposite patterns. The marker pigments prasinoxanthin and zeaxanthin were detected in the gut of M. coruscus indicating that picophytoplankton (e.g., prasinophytes and Synechococcus) are also food sources for this bivalve. This information furthers our understanding of bivalve aquaculture and environment interactions.publishedVersio

Soluble amyloid beta-containing aggregates are present throughout the brain at early stages of Alzheimer's disease.

Protein aggregation likely plays a key role in the initiation and spreading of Alzheimer's disease pathology through the brain. Soluble aggregates of amyloid beta are believed to play a key role in this process. However, the aggregates present in humans are still poorly characterized due to a lack of suitable methods required for characterizing the low concentration of heterogeneous aggregates present. We have used a variety of biophysical methods to characterize the aggregates present in human Alzheimer's disease brains at Braak stage III. We find soluble amyloid beta-containing aggregates in all regions of the brain up to 200 nm in length, capable of causing an inflammatory response. Rather than aggregates spreading through the brain as disease progresses, it appears that aggregation occurs all over the brain and that different brain regions are at earlier or later stages of the same process, with the later stages causing increased inflammation

Pb isotope compositions of detrital k-feldspar grains in the upper-middle yangtze river system: implications for sediment provenance and drainage evolution

The upper-middle Yangtze River drains the Qiangtang Block, the Songpan-Ganzi, the Yangtze Craton, and the Qinling-Dabie orogenic belt. These tectonic units have been shown to have heterogeneous Pb isotopic compositions, which allow this isotope system to be used as a sediment provenance tool. In this study we have employed laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) to measure Pb isotope compositions of sand-sized K-feldspar grains from the upper-middle Yangtze River. Data are presented from four major tributaries: Yalongjiang, Minjiang, Jialingjiang, and Hanjiang, as well as from the main Yangtze River near Yichang. A portion of K-feldspar grains in the Yalongjiang shows an ultraradiogenic character (Pb-206/Pb-204 > 20), which is unique in the upper-middle Yangtze. Moreover, these ultraradiogenic grains were transported as far as Yichang, just downstream from the Three Gorges, suggesting that the Pb-in-K-feldspar method could be applied to the sediments within the Jianghan Basin to date the formation of the Three Gorges. Pb isotopic data from Yichang indicate that erosion in the Longmen Shan and neighboring regions is more important than the Jinshajiang in supplying sediment. The grains in Hanoi Basin have little overlap with the Songpan-Ganzi, but show a good match with the Yangtze Craton in its range of lower 206Pb/204Pb ratios. These observations support the idea that the "Middle Yangtze\u27\u27 used to be a tributary of the paleo-Red River and that there has been no drainage linking the SongpanGanzi and the Red River since the Eocene

Human impact on erosion patterns and sediment transport in the Yangtze River

Sediment load in rivers is an indicator of erosional processes in the upstream river catchments. Understanding the origin and composition of the sediment load can help to assess the influence of natural processes and human activities on erosion. Tectonic uplift, precipitation and run-off, hill slopes and vegetation can influence erosion in natural systems. Agriculture and deforestation are expected to increase the sediment yield, but dams and reservoirs can trap much of this sediment before it reaches the ocean. Here, we use major element composition and 40Ar/39Ar ages of detrital muscovites to constrain the sediment contribution of various tributaries to sedimentation in the Yangtze delta. The sediment contribution calculated from muscovite data was compared with that estimated from current sediment load data from gauging stations. Muscovite data show that the main contributor to the Yangtze delta sands is the Min River, while the current sediment load suggests that the Jinsha and Jialing rivers are the most important current contributors to delta sediments. We suggest that this difference reflects an "old" and "young" erosion pattern, respectively as medium grained muscovite could be transported much slower than suspended sediment load in the complex river-lake systems of the Yangtze River basin. These two different erosion patterns likely reflect enhanced human activity (deforestation, cultivation, and mining) that increasingly overwhelmed long-time natural factors controls on erosion since ~1900 cal years B.P

No Yangtze River Prior to the Late Miocene:Evidence From Detrital Muscovite and K-Feldspar ⁴⁰Ar/³⁹Ar Geochronology

The Yangtze River is the largest river in Asia and its age and evolution has been the subject of debate for more than one century. Here, we applied a combination of detrital muscovite and K-feldspar 40Ar/39Ar dating on a set of samples from late Cenozoic Nanjing fluvial gravel sediments (overlain by basalt with ages of ∼22.9 and ∼10.3 Ma) distributed along the lower Yangtze River to trace the late Cenozoic Yangtze drainage. It is found that the characteristic Cenozoic muscovite and K-feldspar age signals of the upper Yangtze are absent in the gravel sediments, indicating that the upper Yangtze did not supply sediment to the lower Yangtze before at least late Miocene time. These results do not support a prelate Miocene birth of the Yangtze River, but favor an alternative model highlighting later integration of the upper Yangtze into the mid-lower reaches to form the current Yangtze drainage system

Late Oligocene Formation of the Pearl River Triggered by the Opening of the South China Sea

Abstract The Pearl River is one of the largest rivers entering the South China Sea, yet its initiation time remains debated, a topic we address using Pb isotopes in detrital K‐feldspar. Based on these Pb data, Eocene and Early Oligocene sandstones from the northern South China Sea are interpreted to have been supplied with sediment by proximal rivers draining the Cathaysia Block. In contrast, the Late Oligocene and Miocene sandstones are mainly derived from the western Pearl tributaries (e.g., Hongshui River), suggesting that the Pearl River had formed by the Late Oligocene. Detrital zircon data from the Beibuwan Basin previously suggested that the western tributaries flowed into this basin before being captured by the paleo‐Pearl River. These lines of evidence suggest that progressive headward erosion of the eastern Pearl River and late Oligocene integration of this large fluvial system can be linked to contemporaneous sea‐floor spreading of the South China Sea

40Ar/39Ar mica dating of late Cenozoic sediments in SE Tibet: implications for sediment recycling and drainage evolution

The Indo-Asia collision significantly changed the topography and drainage network of rivers around the Tibetan Plateau. Debate continues as to when and how the current drainage system of the Yangtze River was formed. Here we use 40Ar/39Ar dating of detrital micas (muscovite and biotite) to constrain provenances of the Pliocene sediments from the Jianchuan and Yuanmou basins in SE Tibet. Muscovite and biotite data of the same Pliocene samples from the Jianchuan Basin suggest contrasting distal v. local sources, respectively. Similarly, muscovite data of the Yuanmou Basin suggest a derivation of sediments from the Yalong River, but the characteristics of the Pliocene cobbles (palaeocurrent and subrounded cobbles) suggest that these sediments are locally sourced. Sediment reworking is proposed as an explanation for the different sediment provenance signals in the Jianchuan and Yuanmou basins that have led to the controversy of an either Pleistocene or pre-Miocene age of formation of the current Yangtze. Based on sediment provenance constraints, the evolution of the Jinsha River is reconstructed. The upper Jinsha River lost its connection with the southward flowing Red River upstream from the Jianchuan basin at least before the Pliocene. At the same time a parallel site in the Yuanmou Basin shows that the Yalong River stopped flowing southward into this basin. Detrital mica from early Pleistocene sediments at the Panzhihua site between the Jianchuan and Yuanmou basins is sourced from the current Jinsha and Yalong rivers. These results would suggest that the current upper Yangtze drainage system should have been established before the Pliocene

Bioaccumulation and biochemical patterns of Ruditapes philippinarum clams: Responses to seasonality and low contamination levels

Shellfish farming and shellfish harvesting have been practiced for a long time in the Ria de Aveiro coastal lagoon (Portugal). Among commercial bivalves, Manila clam Ruditapes philippinarum represents one of the most important species inhabiting this coastal system. Introduced in Portugal in 1984, naturalised R. philippinarum clam populations have been subjected to several pressures that may threaten this resource sustainable management: illegal fishing, harvesting in chemically polluted sites with impacts on human health and lack of control in terms of productivity with the risk of a progressive decline of the biomass. On behalf of the ASARISAFE project (with the title Safety and sustainable management of valuable clam product in Portugal and China) the environmental quality of Manila clam harvesting sites was evaluated, focusing on inorganic pollution and health status of clams in terms of bioaccumulation as well as biochemical performance. Seasonal sampling campaigns were conducted in six R. philippinarum harvesting areas evaluating inorganic pollution levels, in clam's tissues, sediment and water. Clams biochemical performance in terms of metabolism, energy reserves and oxidative stress was also assessed. The results obtained showed that mercury (Hg) and arsenic (As) were the elements with the highest BAF (Bioaccumulation factor) values, but contamination levels in tissues and sediments varied among sampling areas and seasonal campaigns. The amount of clams consumed per week to exceed Provisional Tolerable Week Intake (PTWI, kg) was the lowest for As, revealing that less 0.05 kg of clams was enough to exceed PTWI. However, the results obtained further demonstrated that the clam's biochemical performance was not responding to tissues contamination levels but were closely related to seasons, with distinct metabolic capacity and oxidative stress levels among distinct sampling periods during the year

DataSheet_1_Effect of Mytilus coruscus selective filtration on phytoplankton assemblages.docx

The feeding selectivity of bivalves can play an important role in shaping the structure of phytoplankton communities of natural waters. This could be particularly true in waters with intensive bivalves farming, like Sungo Bay, Northern China. Understanding the role of bivalve feeding behavior is important for assessing how the dense cultivation of bivalves may affect phytoplankton community composition and food web structure in farm areas. In this study, we investigated the feeding selectivity of blue mussel Mytilus coruscus on natural phytoplankton assemblages in Sungo Bay using both optical microscopy and HPLC-pigment analysis. Results showed that cryptophytes dominated the phytoplankton community and made up 66.1% of the total phytoplankton abundance. A comparison of phytoplankton composition between natural and filtered seawater showed that M. coruscus preferred cryptophytes and dinoflagellates than Chaetoceros spp. and Skeletonema spp. Cryptophytes were not detected in gut contents by microscopic observation, while their marker pigment alloxanthin was present, suggesting they were also consumed by M. coruscus and can be readily digested. This highlights the shortcomings of microscopic methods and the significance of HPLC-pigment analysis in obtaining a comprehensive understanding of feeding selectivity of bivalves. The proportions of Chaetoceros spp. and Skeletonema spp. in gut contents were significantly lower than their proportions in the seawater, and contrastingly, the proportions of Cocconeis spp. and Pinnularia spp. showed opposite patterns. The marker pigments prasinoxanthin and zeaxanthin were detected in the gut of M. coruscus indicating that picophytoplankton (e.g., prasinophytes and Synechococcus) are also food sources for this bivalve. This information furthers our understanding of bivalve aquaculture and environment interactions.</p