Early and late Holocene paleoenvironmental reconstruction of the Pearl River estuary, South China Sea

<p>Proxy reconstructions of estuarine evolution provide perspectives on regional to global environmental changes, including relative sea-level changes, climatic changes, and agricultural developments. Although there are studies of the Holocene sedimentary processes in the Pearl River estuary, the understanding of early Holocene sedimentation in unknown due to limited preservation.</p><p>Here, we present a new record of lithological, benthic foraminiferal, and geochemical (δ<sup>13</sup>C and C/N) change from a sediment core in the west shoal of the modern Lingding Bay along a paleo-valley. The lithologic and foraminiferal record reveal the transgressive evolution from fluvial, inner estuary to middle estuary in the early Holocene between 11300 and 8100 cal a BP in response to rapid sea-level rise. δ<sup>13</sup>C and C/N data indicate high freshwater discharge from 10500 to 8100 cal a BP driven by a strong Asian monsoon. The middle Holocene (8100 - 3300 cal a BP) sediment is absent in this core and others in the northward of the Lingding Bay. Seismic profiles reveal a tidal ravinement surface across Lingding Bay, which contributed to subaqueous erosion on the mid-Holocene sedimentation hiatus, might be resulted from unique geomorphology of the Pearl River Delta. In the late Holocene (3300 cal a BP to the present), the lithology and foraminiferal assemblages suggest further regressive evolution from outer estuary, middle estuary channel, to middle estuary shoal due to deltaic progradation under stable relative sea levels. In the last 2000 years, δ<sup>13</sup>C and C/N values reveal the intensive development of agriculture coupled with the reduction of freshwater input derived from a weakening Asian monsoon. Our study illustrates the interaction of Asian monsoon and sea-level changes within the Pearl River estuary landform and their impact on Holocene sedimentary processes.</p>

Pengaruh Kompetensi Pedagogik Guru Sains terhadap Hasil Belajar Siswa Kelas VII SMP Se-Kecamatan Kota Kefamenanu

Research with the title "Analysis of White Shrimp Abundance in the Abudenok Estuary of Malacca Regency". The purpose of this study was to determine the abundance of white shrimp in the Abudenok Malacca estuary and to find the parameters of the physical-chemical relationship to the abundance of white shrimp in the Abudenok estuary of Malacca Regency. The subject of this research is White Shrimp. The research data were obtained from the results of fishing catches using a 4 m diameter net. The study was conducted once a week for three weeks in the central and lower reaches of the Abudenok estuary. The results of the analysis of the abundance of white shrimp data shows the composition of the catch is different every week. In the first week the middle Estuary catches 158 white shrimp while the downstream Estuary captures fighting 234 tails In the second week the middle Estuary catches white shrimp winning 147 tails while the downstream Estuary catches white shrimp caught 356 tails. In the second week the middle Estuary catches 174 white shrimp while the downstream Estuary catches fighting 276 white shrimp. Effect of physical-chemical parameters on the abundance of 21.5 0C - 29 0C, current velocity of 0.13 ms-0.18 ms-1, salinity of 26.00 ppt - 29.00 ppt and sand substrate. The author concludes that the abundance of white shrimp in the Abudenok estuary is influenced by physical-chemical parameters, especially temperature, current speed and substrate.

Variations in abundance and diversity of phytoplankton in the surface waters of the Golden Horn Estuary (Sea of Marmara)

The abundance pattern and species diversity of phytoplankton in the surface waters of the Golden Horn Estuary were investigated between August 2011 and July 2012 in relation to environmental factors. Seventy-eight phytoplankton taxa (38 diatoms, 30 dinoflagellates and 10 phytoflagellates) belonging to eight taxonomic classes were identified in bottle and net samples. Phytoplankton abundance increased in spring and summer (from March to August) and reached its highest (10,429 × 103 cells L−1) during the bloom of Heterosigma akashiwo (Raphidophyceae) in the middle and upper estuary in late May. In general, phytoplankton abundance was higher in the middle estuary indicating more suitable conditions for phytoplankton growth, while species richness and diversity was higher in the lower estuary. The most abundant species were Skeletonema marinoi and Thalassiosira sp. among diatoms; Scrippsiella trochoidea among dinoflagellates; Plagioselmis prolonga and Heterosigma akashiwo among phytoflagellates. Diatoms were more abundant in the lower and middle estuary, while dinoflagellates and phytoflagellates in the upper estuary. The main factors causing the spatio-temporal variation of phytoplankton in the study area were temperature, salinity, water transparency and nutrients. Water transparency in the upper estuary is mostly influenced by organic and inorganic matter carried by two streams. As a result, this area should be considered a potential risk area for future algal blooms.

Spatial and temporal scales of environmental forcing of Acartia populations (Copepoda: Calanoida) in the Canal de Mira (Ria de Aveiro, Portugal)†

Zooplankton and hydrological data were collected from August 2000 and June 2002 at six stations distributed throughout Canal de Mira (Ria de Aveiro, Portugal). The abundance of Acartia clausi and Acartia tonsa adults and juveniles of Acartia spp. for each station and month were combined in a three-way data matrix, which was decomposed into three two-way matrices corresponding to different modes: biological, time, and space. Cluster analysis applied on the space mode revealed the existence of three different zones as a consequence of zooplankton composition. At each mode, principal component analysis showed strong seasonal variations in zones 1 and 2. A different spatial pattern was found between the periods November 2000–April 2001 and November 2001–April 2002, with the displacement of the highest abundance levels from the middle estuary to near the mouth. The congeneric populations were segregated in space: the A. clausi population was restricted to downstream stations (zone 1), whereas the A. tonsa population dominated the middle estuary. Significant correlations between hydrological parameters and copepod abundance were found to differ from zone to zone. The statistical methodology was a valuable tool to (i) discriminate spatial and seasonal distribution patterns, (ii) define estuarine sections based on the faunistic composition, and (iii) evaluate delayed effects of phytoplankton.

Advances in Fish Tagging and Marking Technology

<i>Abstract</i>.—Movement patterns of two co-occurring catadromous fishes, estuary perch <i>Macquaria colonorum </i>and Australian bass <i>Macquaria novemaculeata</i>, were investigated in a large tidal river in southeastern Australia. Nineteen estuary perch and seventeen Australian bass were captured as mature adults from the Shoalhaven River, surgically implanted with electronic transmitters and released. Forty-nine Vemco (VR2W) acoustic receivers were strategically placed throughout the river from the Tallowa Dam wall downstream to the sea (a distance of 75 km). Between September 2007 and February 2008, a total of 800,263 detection events were recorded with most fish detected in the middle (estuary perch) to upper (Australian bass) estuarine reaches of the river. Both species made extensive use of the estuary, with no estuary perch and only three Australian bass entering the freshwater, indicating that the freshwater residency phase of these catadromous fishes may not be obligatory. The data also suggests that estuary perch and Australian bass exhibit high site fidelity, which, along with their large scale movements may be influenced by factors such as river discharge and prey availability. This large freshwater-estuarine telemetry array combined with critical abiotic information (river discharge and salinity) has and will provide a greater understanding of catadromous fish movement, particularly in relation to habitat utilization and environmental flows.

Patterns of spatial distribution of five species of mojarras (Actinopterygii: Gerreidae) in a small tropical estuary in south-eastern Brazil

The spatial patterns of distribution of five species of the Gerreidae (Diapterus rhombeus, Eucinostomus argenteus, Eucinostomus gula, Eucinostomus melanopterus and Eugerres brasilianus) in Mambucaba estuary, south-eastern Brazil, were determined to assess habitat partitioning of the estuarine reaches. Sampling was conducted between October 2007 and August 2008. Diapterus rhombeus and E. gula were exclusively found in the lower estuary, whereas E. melanopterus and E. brasilianus were exclusively found from the middle estuary. Eucinostomus argenteus was common in the two estuarine zones. Total length and total weight data showed that the smallest individuals of D. rhombeus and E. gula were found near to the estuarine mouth compared with deeper areas of high salinity and lesser influence of the estuarine plume. The smallest individuals of E. argenteus, E. brasilianus and E. melanopterus were found in a protected estuarine lagoon connected to the main estuarine channel, and the largest in the other sites in the main channel of the middle estuary. Spatial partition seems to be the strategy developed by the 5 members of the Gerreidae family to coexist in the Mambucaba estuary, which may be attributed to competition in the past between the species of Gerreidae or to differentiated tolerance to environmental constraints

Seismostratigraphy of the Middle St. Lawrence Esturary: A Late Quaternary Glacial Marine to Estuarine Depositional/Erosional Record

ABSTRACTA buried bedrock trough 350 m deep extends 100 km above Saguenay Fjord beneath the North Channel of the middle estuary. Four of five regional seismostratigraphic units are recognized in and adjacent to the trough; unit 1 (glacial ice-contact) and older sediments might also be present beneath the largely unpenetrated trough axis. Units 2 and 3 represent thick glacial marine sediments deposited in the >550 m deep waters of the Goldthwait Sea after glacial withdrawal ca. 13 ka BP: lower draped muds 10-20 m thick (unit 2) suggest deposition proximal to a retreating ice margin, while upper onlapping muds > 290 m thick (unit 3) record distal basin-filling; lateral transition to a coarse-grained proximal wedge 5*260 m thick (unit 2) is indicated by unit 3 reflectors rising and strengthening towards the Saguenay entrance, where a stable ice-margin ca. 13-11 ka BP supplied sediment to the lower and middle estuary. Unit 4 corresponds to lobes over 30 m thick on both sides of the upper North Channel, recording marginal input from glacial fluvio-deltaic sources. Unit 5 (estuarine sands, gravels and muds =£30 m thick) unconformably overlies glacial units. A smooth unconformity surface records erosion (at least 15 m, to axial depths >150m) by strong currents; irregular relief above depths of 25-50 m might relate to relative sea levels below present ca. 7-6 ka BP. Sand bedforms (apparently inactive) occur at the estuary floor, and possibly buried beneath estuarine muds; buried bedforms would imply an early Holocene genesis. Greatest thicknesses of estuarine mud coincide with adjacent fluvial discharges. Sandy/gravelly veneers form the estuary floor in most places. Mass displacement has disturbed units 3 and 5 along the northern, and locally southern, walls of the North Channel.

Climate change and abundance cycles of two sympatric populations of smelt (Osmerus mordax) in the middle estuary of the St. Lawrence River, Canada

Commercial catches of two ecologically distinct sympatric smelt (Osmerus mordax) populations segregated along the two shores of the St. Lawrence middle estuary exhibited inverse patterns with periodicities on the order of 30 years. The influence of water level in the St. Lawrence River and air temperature, chosen to reflect variations in hydrology and climate, differed markedly between the two populations. Analyses revealed that both water level and temperature were generally positively related with north-shore smelt landings and negatively related with south-shore smelt landings. For both populations, a number of significant climatic factors contributing to variance in smelt landings were lagged by one to three years relative to the year of landings, indicating that climatic variables influenced smelt recruitment. The contrasting role of hydroclimatic variables in driving these abundance cycles is likely related to differential exploitation of estuarine habitats; the south-shore population is associated with shallow shoal habitat, whereas the north-shore population is associated with deep channel habitat. The responses of the two smelt populations also reflect the fundamental ecological differences existing between shoal and channel habitats, indicating that future climate change may differentially affect other populations or species that are segregated between these two habitats.