Phosphorus mass balance in a highly eutrophic semi-enclosed inlet near a big metropolis: A small inlet can contribute towards particulate organic matter production

Terrigenous loading into enclosed water bodies has been blamed for eutrophic conditions marked by massive algal growth and subsequent hypoxia due to decomposition of dead algal cells. This study aims to describe the eutrophication and hypoxia processes in a semi-enclosed water body lying near a big metropolis. Phosphorus mass balance in a small inlet, Ohko Inlet, located at the head of Hiroshima Bay, Japan, was quantified using a numerical model. Dissolved inorganic phosphorous inflow from Kaita Bay next to the inlet was five times higher than that from terrigenous load, which may cause an enhancement of primary production. Therefore, it was concluded that not only the reduction of material load from the land and the suppression of benthic flux are needed, but also reducing the inflow of high phosphorus and oxygen depleted water from Kaita Bay will form a collective alternative measure to remediate the environmental condition of the inlet.     

Fine particulate organic matter transport dynamics in a small Coastal Plain stream: influence of hydrology and channel morphology

Fine particulate organic matter (FPOM) represents a major component of stream organic matter budgets, and its dynamics greatly affect the productivity and metabolism of a stream community. FPOM transport dynamics has been well documented in high-gradient streams with rocky substrates, but information from low-gradient, sandy-bottom streams has been lacking. We estimated FPOM retention patterns in Payne Creek, a 2nd order Coastal Plain stream (USA), under naturally varying hydraulic conditions (discharge and velocity). Corn pollen, as an FPOM analogue, was released along with a conservative solute tracer and the particle retention coefficient (k _p) was calculated by fitting the ratio of total pollen remaining in the water column against the longitudinal transport distance to an exponential decay model. Pollen k _p (n = 4) ranged from 0.034 to 0.214 /m, and particle transport distance (S _p) ranged from 4.7 to 29.7 m. The S _p measured in Payne Creek was in the lowest range of previously reported values, and such rapid particle retention was attributed to the low channel slope and slow current velocity. S _p was significantly correlated to water velocity and the channel friction factor, but not to discharge (Q). Two summer experiments conducted in contiguous stream segments resulted in the shortest (4.7 m) and longest (29.7 m) S _p, despite the similar Q. This was attributed to the segment-scale channel alterations that occurred during the previous winter, which led to very different hydraulic conditions in the two stream segments. In Payne Creek, seasonal changes in hydrology and segment-scale variation in channel morphology were the main factors controlling FPOM transport and retention.     

Nutrients and organic matter in the surface sediment of a submerged macrophyte zone in a eutrophic lake:Implications for lake management

Little is known about the distribution and risk levels of nutrients and organic matter(OM) in the surface sediment of shallow submerged macrophyte-dominated lakes. In the current study, sixty surface sediment samples were collected from Xukou Bay, a typical submerged macrophyte-dominated zone in Lake Taihu, China. A 60-day degradation experiment of Potamogeton malaianus, a dominant species in the bay,was done in the laboratory. The results demonstrated that the ranges of total nitrogen(TN) and t...     

Dissolved and particulate fluxes of copper through the Morlaix river estuary (Brittany, France): mass balance in a small estuary with strong agricultural catchment

Dissolved and particulate copper were measured over an annual cycle (12 surveys between February 1998 and January 1999) in the Morlaix Estuary (Brittany, France). These variations were investigated in both the water column and the benthic compartment in order to calculate fluxes of copper within estuary. In the water column, dissolved and particulate copper concentrations ranged from 0.6 to 19.0 nM and from 0.03 to 2.3 micromol g(-1), respectively. In the benthic compartment, copper concentrations in superficial sediment varied from 0.04 to 0.32 micromol g(-1) and from 7.6 to 80.5 nM in the pore waters. The results show that copper contents in the water column reached levels commonly observed in estuaries affected by heavy industrial activities. Agricultural activities, extensively developed on the drainage basin, may be responsible for the copper excess. Mass balance of copper indicates that the metal accumulated within the estuary with a rate ranging from 97 to 119 kg yr(-1).